NTT Technical Review
March 2015 Vol. 13 No. 3
View from the Top
Katsuhiko Shirai, External Board Member of NTT, Chairperson of theFoundation for the Open University of Japan
Time for a More Human Approach—Facing the Challenges of an Aging
Society and Regional Revitalization through New Forms of Distance
Education

Feature Articles: Reducing the Environmental Burden of
ICT Services
R&D Efforts to Reduce the Burden of ICT Services on the Environment
Evaluation Methods of the ‘By ICT’ EffectR&D on Conservation of Material Resources in Telecom Facilities
Materials Technology for the Production and Storage of Energy
Efforts to Improve Energy Efficiency of Network Service System
Issues and Solutions in Saving Energy of Optical Access Network Equipment
HVDC Power Supply System Implementation
Development of Equipment for HVDC Power Supply Systems

Feature Articles: NTT Tsukuba Forum 2014 Workshop
Lectures
Future Optical Access Technologies for Flexible Service Deployment
R&D Trends in Optical Fiber and Cable Technology
NTT R&D Activities toward Future Access Network Operation

Regular Articles
Development of 100-Gbit/s Packet Transport System

Global Standardization Activities
Standardization Trends for Next-Generation Passive Optical Network
Stage 2 (NG-PON2)

External Awards/Papers Published in Technical Journals
and Conference Proceedings
External Awards/Papers Published in Technical Journals and Conference
Proceedings

View from the Top

Time for a More Human Approach—Facing the Challenges of an Aging
Society and Regional Revitalization
through New Forms of Distance
Education
Katsuhiko Shirai
External Board Member of NTT, Chairpersonof the Foundation for the Open University ofJapan
Overview

Japan is facing an aging society with a declining birthrate. How can distance education support our younger members of society, our future leaders? The Open University of Japan (OUJ) aims to provide new, high-quality
courses through the introduction of cutting-edge ICT (information andcommunication technology). We asked Katsuhiko Shirai, External Board
Member of NTT and Chairperson of the Foundation for the Open University of Japan, who has many years of experience in research and education,
to tell us about OUJ’s approach to education and regional revitalization. We
also asked him to share his thoughts on the role of researchers.
Keywords: ICT, MOOC, speech research

Providing high-quality learning through ICT—Mr. Shirai, please tell us about OUJ’s approach
towards education.
The Open University of Japan (OUJ) aims to provide university courses to a wide segment of society
through television (TV), radio, and other forms ofbroadcast media. Thirty years ago when OUJ was
first established, there were many people who could
not attend university or college because of their economic situation or other reasons. Our objective then
was to enable these people to receive a university

education while working, to promote lifelong learning in society, and to provide people who could noteasily attend a school of higher education because ofa long-distance commute, with the opportunity tolearn.
In the past, enrollment at OUJ was centered about
students in their 20s and 30s, but today, most students
are in the 30–60 age group, with about an equal number of students in each generation. However, there arealso the elderly who, faced with retirement, have astrong desire to study again; this includes people intheir 70s and up into their 90s who are very serious
about learning.
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View from the Top

Conversely, there are many young people whostarted out by entering a university only to quit soonafter if their studies were not meeting their needs or
personal goals. A system is therefore needed toenable them to continue their education. To support
such a wide range of students, OUJ will be introducing online courses with interactive capabilities infiscal year 2015.
The fact is, more than half of the students at OUJ
are now participating in courses via the Internet.
Today, there are more people than ever who areenjoying video and other media via the Internet using
their smartphones or tablets as part of everyday life.
It was therefore inevitable that OUJ would construct
an environment for delivering courses via theInternet.
OUJ is presently delivering lectures and courses
using TV channel 1+α and radio channel 1, but time
constraints limit the number of courses that can beprovided to about 300 per year. Using the Internet
will eliminate such constraints on delivery time andwill theoretically enable any number of courses to beoffered. In this way, we will be able to provide moredetailed, highly specialized courses.
—Internet delivery enables students to take classes
whenever they want, but aren’t you concerned thatsuch a format will give students the freedom to put off
their classwork if they so desire?
That problem exists even today. The current era issuch that students take their classes during a time slot
most convenient for them, whether it be via theInternet or TV. For people who are very serious about
learning, the problem here is more about content.
I believe that there are people who have stumbled
upon some of OUJ’s programs on TV when randomlychanging channels, so I think it is important to create
programs that can attract the interest of these peopletoo.
In addition, a key characteristic of OUJ is that students are always on the opposite side of the instructor’s microphone or camera. Consequently, other thanin face-to-face classes held at more than 50 Study
Centers throughout Japan, instructors cannot directly
perceive the reaction of students to the content of alecture. For this reason, instructors are asked toundergo training not just in regard to lecture content
but also on incorporating various techniques into
their lectures involving their way of speaking, theirbody language and gestures, and the like.
On top of that, an increase in the number of courses
Vol. 13 No. 3 Mar. 2015

offered incurs a proportional amount of preparations
and funds. We are therefore leveraging our extensive
experience in producing high-quality TV and radio
content in dealing with the challenges of creating new
programs. For example, we think that liberal arts
courses should be delivered via TV and radio since
there are probably many people who enjoy such lectures even if they are not OUJ students. On the other
hand, we think that highly specialized courses such as
those at the graduate level taken by a relatively small
number of people should be delivered via the Internet.
This type of management that makes use of the special characteristics of broadcast media is what I
would like to pursue.
Playing a part in dealing with the aging society
and regional revitalization—What is the current state of MOOCs and higher
education in Japan?
A massive open online course (MOOC) refers to acourse given by a celebrated professor of a renowned
university somewhere in the world that anyone canaccess via the Internet. However, participation in pure
MOOCs by Japanese universities would present a
language problem that would lessen their appeal.
Against this background, the Japan Open Online
Education Promotion Council established Japan
Massive Open Online Courses (JMOOC) with theaim of providing courses in the Japanese language.
One official platform for JMOOC is gacco, which
has the distinction of being Japan’s first MOOC website launched in April 2014 in collaboration with NTT
DOCOMO. It has been highly evaluated as a finemechanism for enabling anyone to experience aView from the Top

university level course free of charge, although course
credits are not provided.
In terms of university education, the matriculation
rate into four-year universities is above 50%, ofwhich more than 80% is into private universities. If
this matriculation rate remains unchanged while thebirthrate declines, the number of students will inevitably decrease. Under these conditions, every university is trying to come up with ways of providing more
attractive courses and facilities to attract and maintainstudents, but private universities, especially regional
ones, appear to be in a difficult situation in terms ofoperations and management.
One may think that achieving enrollment goals may
not be so difficult if social awareness of higher education increases and the matriculation rate rises by afew percentage points. However, the reality is that
economic factors and changing values on the part ofuniversity candidates, such as in questioning theworth of a university diploma given its cost, meansthat universities cannot ignore the issue of whether
they can truly provide high-quality courses when they
are in an unstable financial position.
I myself believe that ordinary universities could use
the courses and materials provided by OUJ. In fact, I
believe that if universities were to exchange and provide some of each other’s courses, the quality ofcourse content would rise while easing the burden on
instructors. It might also enhance the depth of courses
without having to raise tuition fees.

—The concept here is that high-quality courses
should be shared among everyone.
I call it a “cloud-type university,” but from here on,
I believe that the focus will be on two main styles ofuniversity education.
In the first style, the student places importance on
the university brand and studies at only one university, finding value in tradition and other conventions.
In the second style, the student discards such traditional values and studies by selecting high-quality
courses from a variety of universities. In either case,
I believe that one role of universities in the future willbe that of a guide to help students navigate through ahuge amount of available material.
It can be said that regional universities have the roleof contributing to the revitalization of the regions
where they are located. For this reason, the use of
JMOOC online courses means more than just supplementing the courses provided by a university; it also
holds the potential of educating and developing
human resources that can contribute to the revitalization of their region. Many young and socially aware
students in their 20s are enrolled in regional universities. If they do not simply complete courses—rather,
they learn something valuable from those courses andbecome more intelligent and motivated—they canbring about real changes in their regions.
It looks as if high-quality courses will become
increasingly open as we go forward. We are on theverge of an era in which an overabundance of content
will make it difficult to decide just what to study. In
the end, there will be a great need to organize thishuge amount of material so that students can makesense of it.
There will be more universities like the Khan
Academy that aim to improve education by creating amechanism for studying at one’s own pace anywherein the world. Adopting this system will enable a university to provide each student with individual support tailored to his or her level of proficiency as
opposed to supervising a few dozen students all
together in one classroom. JMOOC has not yet
reached this point, but some universities are in theprocess of incorporating this system in some of theircourses. I think there will be a major movement in the
future to adopt such a beneficial mechanism.
Time for a more human approach—The speech research field that you were involved infor many years has progressed amazingly.

NTT Technical Review

View from the Top

That’s right. I worked in the field of speech researchfor over 50 years. During that time, studies werebroadly divided into speech recognition and speechsynthesis, and Europe, the United States, and Japan
were vying for the top spot in this field. I was particularly involved in basic research in collaboration with
Advanced Telecommunications Research InstituteInternational (ATR), NTT laboratories, and otherinstitutions. ATR is known for its high-level researchers on loan from top Japanese research laboratories
such as NTT laboratories, and as the place that gavebirth to the automatic interpretation telephone. ATR
led the world in this area with its unique research
results, and the basic idea or principle of this system
can be said to have served as a model for NTT
DOCOMO’s “Hanashite Honyaku,” its automatic
voice translation application.
A major topic in the field of speech research today
is interactive technology. With the coming of the2020 Summer Olympics to Tokyo, there is a need fora practical function that can provide multilingual support. A good portion of this function has already been
completed. However, while speech recognition andspeech synthesis will be major components of thisfunction, multilingual support will require linguistic
elements and language data to serve as models. Up tonow, the study of language models has been thereserve of linguists and grammarians; however, compared to the written word, the spoken word, i.e.,everyday conversation, does not have to be as rigorously correct in terms of grammar or the language in
general. Consequently, in addition to researchers,
there is also a need here for a massive database of
everyday conversation, referred to as a “corpus” inthe linguistics field. It should be possible to create afunction that provides multilingual support by statistically analyzing this corpus and creating stochastic
models. In the past, there were no computers powerful enough to perform such an analysis, but advancesin ICT (information and communication technology)
have made it possible to handle such a huge corpus,
which now needs to be analyzed as “big data.”
Companies and organizations in a wide variety offields ranging from business science to traffic control,
disaster prevention, and case analysis, have alreadybegun to apply big data. I think that now is the perfecttime for the field of speech research to do the same,especially by combining big data with statisticalanalysis and stochastic models, which have been thecornerstone of this field.

Vol. 13 No. 3 Mar. 2015

—Mr. Shirai, having witnessed all sorts of trends inspeech research from its early days to the present,
how do you think NTT laboratories and NTT researchers should face the future?
In the early days, broadcasters and telecommunication companies had their own research laboratories
and carried out basic research in a step-by-step manner. Nowadays, however, companies are coming toquestion the necessity of in-house research—whether
that be basic research or applied research—and arethinking about consigning their research needs toother companies or institutions. In addition, research
institutions that have specialized in basic researchand given society such amazing research results, forexample, Bell Laboratories, have for the most part
disappeared throughout the world.
At the same time, major enterprises such as Google,
Amazon, and Microsoft are taking up the work ofapplied research, signaling a generational shift in thecorporate world. Nevertheless, despite this trend, I
believe that NTT’s basic research laboratories areholding fast to its traditions when it comes to the needfor basic research. Of course, the role of NTT laboratories in general has shifted from basic research toapplied research to meet the needs of the times, but I
believe that it still retains truly autonomous development capabilities.
I would like to see this core R&D (research anddevelopment) strength applied in a direction that cancontribute to society in all kinds of ways. This, I
believe, is NTT’s social responsibility—it’s not justwhat I want but also what society on the wholeexpects.
Today, there is huge competition in big data analysis techniques, which they call “recipes.” Given theabundance of big data material in the world, theView from the Top

important thing here is figuring out how to “cook” bigdata, so for researchers, the task is clear. However, themodels that are coming to be used in big data analysis
are not as simple as those used in the past. Today, they
are highly detailed and involved. Statistical concepts
are therefore becoming key elements in this work.
Techniques for creating statistical models, carryingout analyses, and solving a variety of problems havebeen used in speech research. I believe that applying
these techniques in combination with machine learning theory will reap a mountain of beneficial resultsin the years to come.
From here on, I think many researchers will be discussing the future and talking about what lies ahead.
They may think about truly incredible matters such aswhether intelligence and wisdom in the world can bebrought together inside a computer to outdo humans
and whether cosmic riddles can finally be solved.
They may also talk about various structures and systems by considering, for example, that events that
occur before our very eyes are, in the end, simply aquestion of human cognition. These topics may soundquite eccentric, but thinking in this manner is perhaps
a human trait. I believe that cutting-edge research isgenerated by asking questions such as “What dopeople feel?” and “What do people think about?” and“How do people behave?” Major themes at NTT arecommunications and data processing, or in otherwords, the network and the cloud, which have becomea major presence and influence in our lives. I myself
am fascinated by the prospect of combining thishuman touch with machines such as computers, so
you can see that my involvement in speech research
has continued unabated.

Interviewee profile
Career highlights
Katsuhiko Shirai became an Executive Advisor
for Academic Affairs at Waseda University in2010 after having served as a Professor there
since 1975 and as President of Waseda University
since 2002. He has been the Chairperson of theFoundation for the Open University of Japan
since April 2011 and an External Board Memberof NTT since June 2012.

NTT Technical Review

Feature Articles: Reducing the Environmental Burdenof ICT Services

R&D Efforts to Reduce the Burden of
ICT Services on the Environment
Nobuyuki Watanabe, Yoshiharu Akiyama,
and Akira Sugiyama
Abstract

Providing telecommunications services requires a telecom infrastructure that comprises network
equipment, air-conditioning systems, power supply equipment, access system equipment, and various
other facilities. As a telecom provider, NTT manages the full range of such facilities. This article
describes research and development efforts to reduce the burden placed on the natural environment by
ICT (information and communication technology) services, focusing on what is being done by the NTT
research laboratories and NTT Group companies as members of the Green and Sustainable Infrastructure
Committee.
Keywords: energy and environment, sustainable, energy management

1. Introduction
In the face of global environmental issues such as
global warming and depletion of natural resources,
the NTT Group has for some time been working toachieve three goals in the use and application of
information and communication technology (ICT)
services: creating a low carbon society, implementing
closed loop recycling, and conserving biodiversity.
The use of ICT services involves massive consumption of power and resources including the operationof network equipment such as routers and servers andthe air-conditioning systems needed to cool them,and access facilities such as utility poles and telecomlines. Network power consumption has been increasing along with network traffic, and the overall cost of
power has been increasing because of the rising cost
per unit of electricity. However, even when concerns
about protecting the global environment are set aside,
energy use is a growing problem for business operations in the NTT Group, which used nearly 8.6 billion
kilowatt-hours of electricity in fiscal year 2013
(Fig. 1). Power consumption on this scale accounts
for about 1% of all commercial power used in Japan.
The carbon dioxide emissions associated with power
consumption on that scale make up about 95% of allemissions attributable to the NTT Group, and thatmust be reduced as a step towards achieving a lowcarbon society. Furthermore, we rely almost entirelyon the commercial power supply. Japan currently
depends on imported fossil fuels for power generation, and fuel costs are rising year by year. The effectof that situation on short-term revenue cannot beignored by the NTT Group. What is more, traffic volume is increasing yearly with the increasing popularity of services that transmit large amounts of datasuch as video, and new services for smartphones andother such devices. The investment in facilities needed to cope with the increase in traffic is expected toalso increase the power consumed to provide thoseservices.
To solve the problem of rising energy costs andfuture problems related to the global environment,
NTT Energy and Environment Systems Laboratories
has been collaborating with NTT Network Service
Systems Laboratories, NTT Access Service Systems
Laboratories, NTT FACILITIES, INC. and otherorganizations in the research and development (R&D)
of technology to reduce power consumption and technology to conserve resources and in drafting R&D
strategies.

NTT Technical Review

Feature Articles(100 million kWh)
100
88.0

88.6

88.1

87.0

86.4

80

Renewableenergy, newenergy generation

60
40

Purchased

20
0
2009

2010

2011

2012

2013

(Fiscal year)

Source: based on data from NTT Group CSR Report 2014

Fig. 1. Trend in power use by the NTT Group.

2. Six areas of technology related toenvironment and energy
The provision of ICT services requires a telecom
infrastructure that comprises network equipment, airconditioning systems, power supply equipment,
access system equipment, and various other kinds offacilities. To reduce the environmental burden createdby the telecom infrastructure, the Environment andEnergy Technologies Committee was established in
April 2013. (The name was changed to the Green andSustainable Infrastructure Committee in November
2014.) The Committee serves as a strategic organization for cooperation among all facility-managing
entities within the NTT Group, including the researchlaboratories and member companies, in the R&D ofelemental technology in the six areas (Fig. 2) listed
below.
(1)	Power source related technology for raising thelevel of self-sufficiency and supplying power to
network equipment(2)	Air-conditioning related technology for raising
the energy efficiency of air conditioning systems for telecom buildings(3)	Technology for integrated operation of network
equipment, power supply systems, and air-conditioning systems(4)	Technology for reducing power consumption,with network architecture and network equipment designed to contribute to overall network
energy efficiency(5)	Green telecom infrastructure technology forVol. 13 No. 3 Mar. 2015

resource conservation(6)	Technology for dealing with electromagnetic
radiation, lightning, and other disturbances fromthe external environment.
These Feature Articles introduce R&D work onmaterials for energy production and storage [1] andhigh-voltage direct current (HVDC) power supplies[2, 3], which concern the first three items above.
Other articles feature work on reducing power use of
network equipment [4] and of optical access systems[5] (item 4), and work on conserving resources for thematerials used in the telecom infrastructure [6] (item5). We are also working on technology for quantitatively measuring the effects of ICT services on theenvironment [7].
3. Future development
NTT Energy and Environment Systems Laboratories has been collaborating with other NTT researchlaboratories and NTT Group companies through theGreen and Sustainable Infrastructure Committee todevelop technology for reducing the load placed on
the environment by ICT services. We are continuously moving forward with R&D to improve energy
efficiency and resource efficiency in the overall business activities of the NTT Group by responding rapidly to the needs of businesses and external trends.

Feature Articles(3) Technology that integrates operation of network equipment,
power supply systems, and air-conditioning systems(1) Power source related
technology– Electrical power supply
technology– Energy creation and storage
system technology

Network(4) Technology for energy-saving
network architecture andequipment– Reduces power consumption
through integration and reductionof equipment– Reduces equipment power
consumption

Communications Communications
infrastructurebuilding(2) Air-conditioning related
technology– Air-flow control technology

ONU
ONU
ONU
ONU

A/C

ONU

MDF

PS

(6) Technology for dealing with external environment– EMC technology– Soft error test technology(5) Technology for resource conservation

A/C: air conditioning
EMC: electro-magnetic compatibility
MDF: main distribution frame
ONU: optical network unit
PS: power source

Fig. 2. Six areas of technology concerning energy and the environment.

References
[1]

[2]

[3]



J. Nakamura, T. Komatsu, and M. Hayashi, “Materials Technology for
the Production and Storage of Energy,” NTT Technical Review, Vol.
13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa4.html
T. Tanaka, J. Kato, A. Sakurai, T. Iwato, M. Shintaku, A. Takahashi,
K. Asakimori, N. Hanaoka, H. Matsumori, and N. Yamashita, “HVDC
Power Supply System Implementation,” NTT Technical Review, Vol.
13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa7.html
H. Hoshi, H. Yajima, T. Babasaki, K. Hirose, H. Matsuo, M. Noritake,and T. Takeda, “Development of Equipment for HVDC Power Supply
Systems,” NTT Technical Review, Vol. 13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa8.html

[4]

[5]

[6]

[7]

J. Koga, T. Kurimoto, T. Hamano, A. Terauchi, and M. Miyasaka,“Efforts to Improve Energy Efficiency of Network Service System,”
NTT Technical Review, Vol. 13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa5.html
H. Ujikawa, T. Shibata, and K. Suzuki, “Issues and Solutions in Saving Energy of Optical Access Network Equipment,” NTT Technical
Review, Vol. 13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa6.html
Y. Higashi, K. I. Takahashi, and T. Sawada, “R&D on Conservation ofMaterial Resources in Telecom Facilities,” NTT Technical Review,Vol. 13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa3.html
T. Nagao, Y. Takei, and S. Hannoe, “Evaluation Methods of the ‘By
ICT’ Effect,” NTT Technical Review, Vol. 13, No. 3, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
03fa2.html

NTT Technical Review

Feature Articles

Nobuyuki Watanabe

Vice President, Head of NTT Energy and Environment Systems Laboratories.
He received the B.S. in electrical engineeringfrom Chiba University in 1982. Since joining
NTT in 1982, he has mainly been engaged in
R&D of digital switching systems, switching
services, and call agent systems. He is a memberof IEEE (Institute of Electrical and Electronics
Engineers) and IEICE (Institute of Electronics,
Information and Communication Engineers).

Akira Sugiyama

Senior Research Engineer, Research Planning
Section, NTT Energy and Environment Systems
Laboratories.
He received the B.S. and M.S. in computer science from Tokyo Institute of Technology, Tokyo,
in 1994 and 1996, respectively. He joined NTT
Basic Research Laboratories in 1996, where he
was engaged in research on natural language
processing. He moved to NTT Energy and Environment Systems Laboratories in 2004. He currently belongs to the Research Planning Section
in Energy and Environment Systems Labs.

Yoshiharu Akiyama

Executive Manager, Research Planning Section, NTT Energy and Environment Systems
Laboratories.
He received the B.E. and D.E. from the University of Electro-Communications, Tokyo, in 1990
and 2010, respectively. Since joining NTT in
1990, he has been researching methods of testing
and measuring electromagnetic compatibility(EMC) of wireless communication and broadband communication systems. In 2013, hebecame manager of the Energy System Project
and was engaged in developing the HVDC power
supply system. He is now the Executive Managerof the Research Planning Section in Energy andEnvironment Systems Labs.

Vol. 13 No. 3 Mar. 2015



Feature Articles: Reducing the Environmental Burdenof ICT Services

Evaluation Methods of the ‘By ICT’
EffectTomomi Nagao, Yuichiro Takei, and Shinsuke Hannoe
Abstract

As a step towards achieving the goals of THE GREEN VISION 2020, the NTT Group’s environmental vision for the year 2020, the NTT Energy and Environment Systems Laboratories has developed
various methods to evaluate the ‘By ICT’ effect as a means of evaluating the effect of reducing the societal load on the environment by using information and communication technology (ICT) at the enterpriselevel. Such evaluation makes it possible to easily calculate the total reduction in the environmental loadthat results from the ICT services provided by the NTT Group by using business indexes such as sales
and number of contracts.
Keywords: Green by ICT, environmental load reduction, CO2 emissions

1. Introduction
There are expectations that the use of informationand communication technology (ICT) can reduce theoverall load of society on the environment as a measure against global warming [1]. ICT can be used toincrease the efficiency of energy use, reduce the production and consumption of products and make theprocesses more efficient, and reduce the movement ofpeople and goods, and thus reduce CO2 emissions
stemming from those activities. Our name for these
efforts to use ICT to reduce CO2 emissions in society
as a whole is “Green by ICT.”The NTT Group established THE GREEN VISION
2020 as our environmental vision for 2020 [2], which
is based on the policies of Green by ICT, Green of
ICT, and Green with Team NTT. The objective ofGreen by ICT is to expand the use of ICT and, specifically, to achieve a reduction in CO2 emissions of
20 million tons by increasing the use of all ICT services offered to customers by all NTT Group companies in 2020. To manage and monitor the degree ofattainment of the goal for this objective, a means ofevaluating the total reduction in CO 2 emissions
resulting from the use of ICT services provided byeach company (the By ICT effect) is necessary.



2. Development of methods for evaluating
the By ICT effect
The By ICT effect for individual ICT services isevaluated by comparing the amount of CO2 emitted
when ICT services are used with the same emissions
produced when conventional, non-ICT means areused to provide the same functions, as calculated
according to environmental efficiency guidelines [3]using the life cycle assessment (LCA) method [4].
The concept of these calculations is illustrated inFig. 1. In the NTT Group, the By ICT effect of many
ICT services is evaluated by using the Environmental
Solution Certification System [5].
As the enterprise targets described above, all ICT
services offered by an enterprise to customers are
subject to evaluation of the By ICT effect. However,the number of ICT services at the enterprise level isvery large, so it is difficult to evaluate all of the services individually and to sum them up with limited
management resources. Therefore, the challenge wasto establish methods for easily estimating the total By
ICT effect at the enterprise level by using certain
management indexes, such as sales results and numbers of contracts.
To meet that challenge, we developed a method for
estimating the scaled, overall By ICT effect by
NTT Technical Review

Feature Articles

Model for comparison(e.g., travel by public transport)

ICT service model for evaluation(e.g., multipoint videoconferencing)
Gatekeeper
Videoconference
systemRouterTransportation

Conference
site

Reduction of environmentalload by ICT services(By ICT effect)

Environmental load
(CO2 emissions)

OfficeMultipoint connection
serviceVideoconference
systemRouterConventionalmeans

ICT services

Fig. 1. Evaluation of By ICT effect of ICT services.

Unit for calculations
By ICT evaluation of
application system services

Scaling factor

Solutions

CO2 emission reduction
per unit sales

×

Sales

Business NW

CO2 emission reduction
per contract

×

Number of service
contracts

Consumer NW

CO2 emission reduction
per line×

Number of line
contracts

By ICT evaluation of network
system services

NW: network

Fig. 2. Categories for evaluating By ICT effect.

multiplying the reduction in CO2 emissions per unit
by a scaling factor, under the assumption that the By
ICT effect is proportional to a value that represents
the number of ICT services offered by an enterprise(the scaling factor). We took the service hierarchy andusers into consideration and divided the NTT Group
services into solutions, business network services,and consumer network services, and developed evaluVol. 13 No. 3 Mar. 2015ation methods for each category (Fig. 2). For the scaling factors, we used management indexes, specifically the sales of solutions and the number of network
service contracts for network system services. The
evaluation methods for the different categories are
explained below.

Feature Articles

Industry

effect on a national level in order to measure how theuse of ICT contributes to improving the environment.
2.2 E
 valuation method for business network services
The method for evaluating business network services applies to leased lines and Internet protocol
virtual private network (IP-VPN) services. The By
ICT effect for a model enterprise is evaluated according to the guidelines for environmental efficiency
evaluation. Assuming a typical model enterprise thatuses leased line services, we use the calculated
amount of CO2 emission reduction for the model
enterprise as the calculation unit. That value is multiplied by the number of service contracts in order toGovernment
Reduction of CO2 emissions

2.1 Evaluation method for solutions
The solutions evaluation method [6] estimates the
By ICT effect by multiplying the sales (scaling factor) and the unit for calculation. The unit for calculation is the amount of CO2 emission reduction per one
million yen of solution sales. We evaluated the By
ICT effect for the solutions provided by each NTT
Group company according to the guidelines for environmental efficiency, plotted the results against solution sales, and derived linear regression equations.
The slopes of the regression lines serve as the units
for calculation. Regression equations were derived
for the government, finance and insurance, and information and communication industry categories of
ICT solutions (Fig. 3). Grouping the solutions byindustry confirms that a correlation between the By
ICT effect and sales can be obtained. By multiplying
the calculation units of each industrial category by
the respective sales figures and then summing thevalues, the By ICT effect for all the solutions of anenterprise can be estimated (Fig. 4).
To share this approach with companies outside of
the NTT Group and obtain social recognition, weestablished the ICT Business Organization LCA
Study Group within the LCA Society of Japan in
2012. The Study Group is making progress in setting
guidelines for the method of calculating the By ICT
effect at the enterprise level. The calculation method
provides a basis for setting quantitative environmental targets for companies, quantitative management ofgoal attainment, and disclosure of information tosociety. Our objective for the future is to establish amethod for quantitatively calculating the By ICTInformation andcommunications

Finance &insurance

Sales

Fig. 3. Derivation of units for calculation.

Sales (millions of yen)Company A

Company B

Company C

Company D

Company E

Unit forcalculation(t-CO2/million yen)

Finance & insurance
Government
Information andcommunications
Manufacturing
Transportation
Health & social

Derived by using‘By ICT’ effectevaluation methods

Derived from financial
statements

Derived by using‘By ICT’ effectevaluation methods

Fig. 4. Estimated By ICT effect of solutions.



NTT Technical Review

Feature Articles

Assumed enterprise modelServices and use scenarios

Number of employees: N
Number of lines: m
Number of terminals: N

Officeoriented
services

BranchofficeBranchofficeBranchofficeICT services

IP phones

Fixed line andIP lineIntegrated to IP

Telecom2 muting

Working at theoffice (to work,
return home)

Telecommuting(at home, direct
return)Groupware

Return to office
to check

Check info.
while out of
office13

Calculated By ICT effect (total)
for business network services

Use scenarios
Conventional
means (before
adoption)

Main officeEvaluation ofenvironmental impact

IP phones
Telecommuting
GroupwareM=

Total =

M× number of corporate contractsmt-CO2/year permodel enterpriseFig. 5. Evaluation of By ICT effect for a model enterprise.

estimate the By ICT effect for typical leased line and
IP-VPN services. The evaluation concept is illustrated in Fig. 5. The number of service contracts used isthe number for the model enterprise obtained fromthe number of lines needed for the services and thenumber of corporate contracts. The By ICT effect foreach model enterprise is obtained by multiplying the
calculation unit and the number of service contracts,
and those values are then summed to estimate the By
ICT effect for all business network services.
2.3 E
 valuation method for consumer network
services
The method used to evaluate consumer network
services [7] is based on the use of feature phones or
smartphones on the mobile network and the use of
personal computers on a broadband network. The By
ICT effects are calculated by multiplying the calculation unit by the respective scaling factors (number ofline contracts). The calculation unit is the amount of
CO2 emission reduction per line calculated fromtypical use scenarios for consumer network services
and the corresponding values for conventional means.
The use scenarios for broadband and mobile networks are diverse, so we selected use scenarios forwhich the user rates were 10% or more as typicalscenarios after referring to statistical information(Table 1). We obtained the use frequencies for the
scenarios and the conventional means that were usedin the comparison from questionnaires, and we calculated the amount of CO2 emission reduction according to environmental efficiency guidelines (Fig. 6).
User questionnaires were obtained from 1160 people
via the web. The calculated units for calculation wereVol. 13 No. 3 Mar. 2015

multiplied by the respective numbers of contracts toestimate the By ICT effect for consumer network
services.
3. Trial calculations of the
By ICT effect for 2013
We applied the evaluation methods described abovein trial calculations of the By ICT effect for the NTT
Group for fiscal year 2013 and reported the results in
the NTT Group CSR (Corporate Social Responsibility) Report 2014 (Fig. 7). Those results include evaluations for solutions, business network services, andconsumer network services, and they indicate that the
reduction in the amount of CO2 emissions increased
from 10.37 million tons for fiscal year 2010 to 29.64
million tons for 2013. The large increase in the By
ICT effect is due to the increase in use time for consumer network services, particularly for broadband
networks and smartphones used on mobile networks.
The hours of use per day for personal computers andsmartphones have risen sharply since 2011, and thisfact is reflected in the evaluation results.

Feature Articles

Table 1. Typical use scenario selection for consumer network services.

Use scenario

Xi

FOMA

FLET’SHIKARI

FeaturephonesSmartphones

Personalcomputers

Voice calls
EmailMusic (including ring tones)
ImagesGamesEntertainment, sports, and news
Search and link aggregation
Bulletin boards
Personal websites
Blogs
SNS
Free video
Charged video
Dining information
Cell phone manufacturer sites
Maps
Transportation info & time schedules
General news
Weather reports
Online banking
Online shopping
Auctions
Awards, questionnaires
Bargains, discount coupons
Stocks, market information
Miscellaneous info & culture
SNS: social networking service

4. Future development
The NTT Group will continue to work towards
reducing the load placed by society on the environment in the future by further broadening the range of
ICT use in various fields. By quantitatively assessingthat work using the By ICT effect evaluation methods
and announcing the results to the public, we will continue to demonstrate the environmental contributionsof the NTT Group. We will also continue to expand
the use of the By ICT effect evaluation methods,
beginning with the work that is already underway toestablish guidelines for evaluating solutions.

References
[1]

[2]
[3]
[4]

[5]
[6]



T. Hayashi, T. Origuchi, Y. Somemura, and Y. Sugiyama, “Quantifying Environmental Load Reduction Effect of Utilizing ICT,” NTT
Technical Review, Vol. 9, No. 2, 2011.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2011
02fa9.html
NTT CSR Promotion Department, “NTT Group CSR Report 2010,”
2010.
LCA Society of Japan, “2005 Environmental Efficiency Guidelines
for ICT,” 2006.
S. Hannoe, Y. Takei, and H. Kitabayashi, “Environmental Impact
Assessment System,” NTT Technical Review, Vol. 11, No. 1, 2013.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2013
01fa5.html
S. Hannoe, M. Tsuda, and J. Nakamura, “Evaluation of the Environmental Impact of ICT Services and the Social Impact Index,” NTT
Technical Journal, Vol. 21, No. 8, pp. 32–36, 2009 (in Japanese).
T. Nagao, S. Hannoe, A. Sakurai, Y. Tanaka, and K. Saito, “Methods
for Estimating the Environmental Load Reduction Effects of ICT
Services,” The 9th Annual Meeting of the Institute of Life Cycle

NTT Technical Review

Feature Articles

Use
scenarios

ICT services(Xi)

Conventional
means(for comparison)

Service use
Use time
Percentrate (%) (hours/years) age (%)

Evaluation model

Email• Feature phone or
smartphone• Mobile network

Home
phone

• Fixed-line phone• Fixed-line network

58.5

Publicphone• Public phone or round-trip travel• Public phone• Fixed-line network

11.8

Letters• Letters• Posting or round-trip travel• Mail box• Mailing

6.9

FAX

• Paper• Fax machine• Fixed-line network

4.3

Directmeeting• Round-trip travel

5.5

Nothing• None13.0

Without Xi

96.7

The parts within the broken lines areoutside the scope of the evaluation.

48.6

100

CO2 emissions(kilograms ofCO2/year)

0.59

115.7

The numbers are for Xi.

Fig. 6. Method for calculating CO2 emission reduction for various use scenarios and conventional means (e.g., email).

(Fiscal year)
10.37 million ton reduction

2010

2013

29.64 million ton reduction
0

10

20

30

(Million t CO2)

Source: Compiled from NTT Group CSR Report 2014

Fig. 7. By ICT effect for NTT Group.

[7]

Assessment, Japan, pp. 240–241, 2014.
S. Hannoe, Y. Takei, A. Sakurai, T. Nagao, and K. Saito, “Environmental Impact Reduction Effect of Network Services,” Proc. of the
IEICE Society Conference, p. 98, 2014.

Vol. 13 No. 3 Mar. 2015



Feature Articles

Tomomi Nagao

Research Engineer, Environmental Management & Provisioning Project, NTT Energy andEnvironment Systems Laboratories.
She received the B.E. in economics and the
MBA in professional accounting from Tohoku
University, Miyagi, in 2009 and 2011, respectively. She joined NTT in 2011. She is currently
studying the evaluation methods of the ‘By ICT’effect.

Shinsuke Hannoe

Senior Research Engineer, Supervisor, Environmental Management & Provisioning Project,
NTT Energy and Environment Systems Laboratories.
He received the B.E. and M.E. in mechanicalengineering from Chiba University in 1990 and
1992, respectively. He joined NTT in 1992 andstudied microelectromechanical systems. He iscurrently researching how the use of ICT reduces
the burden on the environment.

Yuichiro Takei

Senior Research Engineer, Environmental
Management & Provisioning Project, NTT
Energy and Environment Systems Laboratories.
He received the B.S. and M.S. in chemistryfrom Keio University, Kanagawa, in 1985 and1987, respectively. He joined NTT in 1987. He iscurrently researching an environmental assessment system for ICT services. He is a member ofIEEE (Institute of Electrical and Electronics
Engineers) and IEICE (Institute of Electronics
Information and Communication Engineers).



NTT Technical Review

Feature Articles: Reducing the Environmental Burdenof ICT Services

R&D on Conservation of Material
Resources in Telecom Facilities
Yasuhiro Higashi, Kazue I. Takahashi,
and Takashi Sawada
Abstract

NTT Energy and Environment Systems Laboratories has been focusing on the material resources usedin constructing telecom facilities and is pushing forward with research and development (R&D) of green
infrastructure technology for conserving resources in the design of new facilities in order to achieve along service life, extend the service life of existing facilities, and renovate old facilities. This article
presents a technology for diagnosing and evaluating degradation of buried stay rods and anchors toextend the service life of existing facilities, and a resource visualization technology that is relevant torecycling of resources when discarding facilities.
Keywords: telecom facilities, material resources, resource conservation

1. Introduction
The NTT Group telecom line facilities that support
information and communication technology (ICT)
services include about 700,000 km of optical cable,
about 1.1 million km of metal cable, about 12 million
utility poles, and about 620,000 km of conduit. It isthus important for the NTT Group to move forwardwith resource conservation while maintaining thesafety and security of such a huge amount of infrastructure. Resource conservation is often discussed interms of 3R technologies: reduce, reuse, and recycle.
In reducing materials used for deployed facilities, it isimportant to extend the service life of existing facilities as well as to design future facilities with resource
efficiency considerations. For that purpose, proper
methods of diagnosing and evaluating degradation inexisting facilities are essential. In this article, we firstdescribe a technology for diagnosing and evaluating
degradation in the buried stay rods and anchors ofutility poles. We then describe resource visualization
technology that contributes to improving recycling
through clarification of the amounts and types ofresources contained in discarded telecom equipment.



2. Technologies for evaluating degradation ofburied stay rods and anchors
Utility poles are supported by a strand wire that isconnected to a stay rod and secured underground byeither a block (block type) or an anchor (anchor type)(Fig. 1). The stay rods are treated with hot-dip galvanization, and in order to prevent further corrosion,
they have been coated with polymer (coatings) since1988. About one-third of all blocks and anchors(about 2.5 million) produced under the old specifications prior to 1988 are still in use and are subject to ahigh failure rate due to corrosion in soil. The need forrenovation of such facilities depends on the degree ofdegradation, so the criterion for renovation of the rod
is set such that renovation is required before thecross-section of the rod is reduced by 50%, whichcorresponds to a safety factor of 1 (compared to asafety factor of 2 for new products). However,
although the above-ground portion of the rod can beinspected visually, there is currently no means of
directly checking the underground part without excavating the rod. There is therefore a need to develop an
evaluation technology that does not require excavation of the rod to determine if there is thinning or adefect in the underground part that poses a risk of
NTT Technical Review

Feature Articles

Utility poleLine tension

Anchor type

AnchorBlock type
Stay rod

Block

Fig. 1. Utility pole support: anchor and block types.

fracture. A method that uses ultrasonic guided waves
to detect degradation in the underground part isdescribed below.
2.1 U ltrasonic guided wave technology for underground rods
Ultrasonic guided waves*1 differ from ordinary
ultrasonic waves (bulk waves) in that their propagation is confined to within an object. There is lessattenuation of guided waves over distance than forordinary bulk waves, so they propagate over longer
distances. For that reason, guided waves are being
used in the development of diagnostic technologies
for pipelines and other such structures [1]. However,there are some problems to be solved before guided
waves can be applied to diagnose rods.
(1)	In an underground environment, the energy lossof the guided wave outside the rod results inhigh attenuation.
(2)	For rods that are in current use, particular probes
are required that enable guided waves to betransmitted and received from the above-ground
portion of the rod.
(3)	Detection of the signal reflected from underground thinning or defects with good sensitivity(high signal-to-noise ratio: SNR) is difficult
because noise that originates outside the underground part of the rod is generated.
As the first step in solving these problems, weinvestigated ultrasonic wave modes and frequencies.
A guided wave propagating in a cylindrical, isotropic,
homogeneous elastic body such as a metal rod may
have one of three modes, depending on the vibration
pattern. One of those modes is the L mode, which has
the vibration shape illustrated in Fig. 2(a). We calculated the dependence of the attenuation rate on freVol. 13 No. 3 Mar. 2015quency assuming that the propagation of the guided
wave in the L mode had the vibration pattern shownin the figure in a rod buried underground. The results
for a rod with a diameter of 13 mm obtained using
ordinary soil characteristics are shown in Fig. 2(b)[2]. On the basis of these results, we selected a 60kHz, L(0, 1)-mode guided wave as having a low
attenuation rate.
Next, we designed and fabricated compact probesthat have built-in piezoelectric vibration elementsthat generate vibrations at 60 kHz for transmitting
and receiving the guided waves from the side of a thinrod. In the measurements, we used pairs of probesthat had the same performance, and we set the twoprobes in each pair on opposite sides of the rod. The
probes are driven with the same phase, and thereceived signals are summed so that the L mode signal can be transmitted and received selectively. We
further arranged multiple pairs of probes to enable
control of the direction and directionality of the transmitted and received wave signals (Fig. 2(c)) toachieve a higher SNR and improve sensitivity [3].
We used the equipment configuration describedabove together with a new sample rod in which an
artificial defect was formed to investigate the feasibility of detecting the defect under the same conditions
as for an actual buried rod. The concept of defectdetection by a guided wave is illustrated in Fig. 3(a),and an example of the actual measured results for aburied rod (13 mm in diameter and 215 cm in length,with a 10-mm-wide artificial defect that reduced the*1	 Ultrasonic guided wave: An ultrasonic wave whose propagationis confined to within a solid object. Guided waves have multiple
modes, and the speed depends on the frequency, which is in contrast to ordinary ultrasonic waves (bulk waves), which propagate
in a medium that is sufficiently large relative to the wavelength.

Feature Articles

Attenuation rate (dB/m)(a) L-mode vibration shape

Vibration shape is axiallysymmetrical and has
displacement components inthe axial and radial directions.

150
L(0, 3)100
L(0, 1)50
00L(0, 2)200

400

Frequency (kHz)(b) Frequency dependence of L-mode guided wave attenuation in a buried rod
2 sets of pair probes 2 sets of pair probes
for transmitting
for receiving
P2

P1

R2

R1

Upper direction(to rearward direction)
Transmitted wave direction
control

Distance
Adjusting the distance between
betweenthe sets of probe pairs (P1 and P2) probe
controls the delay time andpairs forthe phase to cancel out the guided transmitting
wave in the rearward direction.

In-ground direction(to forward direction)
Received wave directionality control
Distance
betweenprobe
pairs forreceiving

Adjusting the distance between thesets of probe pairs (R1 and R2) sums thetwo received signals with a constant delay
time and polarity so that only the guided
wave signal is received from the forward
direction.

(c) Example of probe arrangement on rod

Fig. 2. L-mode guided wave vibration shape, attenuation, and probe arrangement.

diameter by 40%) is presented in Fig. 3(b). A clear
echo from the artificial defect is observed in the
result, confirming that it is possible to detect anunderground artificial defect with this method. We
are currently conducting field testing of this diagnostic technology to verify the feasibility of detecting
actual degradation from corrosion thinning with thecooperation of NTT EAST and NTT WEST.
2.2 I nvestigation of method to estimate degradation in buried anchors
In addition to the ultrasonic guided wave diagnosis
technology for stay rods, we are investigating amethod for estimating the degree of degradation inunderground anchors due to corrosion, since anchor
types are used in far more facilities than block types,
but the ultrasonic wave is not transmitted to theanchors. For anchors, the supporting force is obtained
from the part that is driven into the ground. We are
therefore investigating corrosion degradation in theunderground part of the anchor over time and constructing a degradation model, which we will use tocalculate strength in order to implement technology
to determine when renovation may be necessary.
3. Resource visualization technology
Resource visualization technology is used to understand the types and amounts of resources contained intelecom facilities and to identify locations of uneven
distribution of resources in order to provide information for advanced recycling of discarded equipment.
Information on toxic materials such as lead and heavy
metals has been available for some time because
manufacturers are obligated by law to report the content of harmful substances in order to prevent any
harmful effects on human health in the use andrecycling stages. However, the contents of gold, silver, and copper, which can be recovered throughrecycling, are not reported because there is no obligation to do so on the supply side. Therefore, the discarding of equipment has generally been handled
without information on the amount of resources contained in the equipment.
NTT Technical Review

Feature Articles

Loop

Probe

Pulserreceiver
Transmitted wave

Above ground
Below ground

Stay rod

Reflection from theartificial defect(defect echo)
Reflection fromthe end surface(end echo)

Artificial
defectEnd(a) Detection of artificial defect by guided wave
(blocks etc. are omitted.)

Artificial defect(60% diameter residual ratio)

Defect echo
End echo(b) Measured results for artificial defect in a buried rod

Fig. 3. Detection of defect by guided wave and measured
results.

3.1 Purpose of resource visualization technology
Used switching equipment accounts for the secondlargest amount of waste generated by the NTT Group,
after concrete utility poles. Many kinds of materials
are used in switching equipment to achieve high performance, so the discarded equipment itself can be an
important resource. We therefore consider the newnode switches, which will be discarded in large numbers in the future migration of the public telephone
network, to be a promising subject for research ontechnology for visualizing material resources. Analyzing and estimating the contents of resources arecore technologies for resource visualization technology. Knowing the types and amounts of materialVol. 13 No. 3 Mar. 2015

resources of discarded equipment in advance willlead to better selection of an optimal recycling method. Moreover, knowing which parts contain the greatest amounts of rare metals would make it possible toconcentrate those resources by collecting the appropriate parts and to increase the recovery efficiency.
Improving recycling processes can be expected toreduce the cost of disposing them, thus accomplishing two goals at the same time.
3.2 D evelopment of resource visualization technology
Material resource visualization involves the use ofanalysis and estimation technologies. The resource
contents of typical components and circuit boards areanalyzed, and the results are stored in a database, as
shown in Fig. 4. With circuit boards for which theresource content is unknown, the types and numbersof components mounted on the board are input, andthe content is estimated by obtaining data on partsinformation and/or content for similar parts from thedatabase.
New node switches use many kinds of circuitboards, so we first investigated the various circuitboards used in the switches. We selected typicalboards that are common to all switches and that arepresent in large numbers. Next, we selected material
resources that have high economic value and a highrisk of depletion. As a result, we selected eight elements for quantitative evaluation, including gold,
silver, copper, and palladium.
The challenge in developing the analytical method
was to find a way to analyze easily and circumstantially the target elements in circuit boards that containplastics as well as various kinds of metals. We first
tried the usual inductively coupled plasma (ICP)
analysis*2, but the preparation of samples in solution
form requires a complex and expensive process.
Therefore, X-ray fluorescence analysis*3 was used
together with ICP analysis because the preparation
process is simple; the samples are prepared by pulverizing and compacting the boards. We are therefore
investigating an analysis method using ICP and X-ray
fluorescence accordingly as a method for simple*2 ICP analysis (ICP-AES: ICP atomic emission spectroscopy, or
ICP-MS: ICP mass spectrometry): A quantitative analyticalmethod that can achieve highly accurate analysis of multiple
chemical elements but has the disadvantage of a complicatedsample preparation process.
*3 X-ray fluorescence analysis: A quantitative analysis method forchemical elements that is less accurate than ICP analysis but requires relatively simple sample preparation and can be used toanalyze multiple elements at the same time.

Feature Articles

Board Ax CPUs, y ICs,z capacitors, ...

Board AAu: 500 mg,
Ag: 1000 mg,
Cu: 18,000 mg, ...

Database of resource content by part
Part

Au

Ag

Cu

CPU

290

290

2500

IC

96

490

1500

Capacitor

0

5900

2500

…

基板 A
Au: 500 mg

Image
Resource
amounts

Resource value: x yen

3000 円Switch X…

Quantities ofcircuit boards
Board A: a
Board B: b
Board C: c....

Circuit board
configuration

Database of resource content by circuit board
…

Part

Au

Ag

Cu

Board A

500

1000

18000

Board B

600

3700

16000

Board C

1200

1200

28000

…

Database ofcontained
resource
amountin parts
and boards

CPU: central processing unit

Switch X
Au: 40 g
Ag: 300 g
Pd: 10 g...
Resource value:
Y yen

交換機 X
Au: 40g
300000 円

Resource amounts

IC: integrated circuit

Fig. 4. Resource content estimation system.

Table 1. Comparison of resource contents.
(Weight, ppm)
New node circuitboards*4

Personalcomputer [4]Natural ore [5]

Gold

230

120

411

Silver

440

680

182

13

Copper200,000

159,000

89,0008400

Palladium

95

160

90

1.1

Chrome

400

33

900

230,000

Gallium

8

1056

Zirconium

170

110

230

3700

Antimony

3800

58

130

9900

*4 Average for three new node boards

1.1*5 Average for 140 cell phones, excluding batteries

quantitative analysis within the permissible range ofaccuracy.
As an estimation method, we are investigating asumming method in which the amounts of resources
contained in the components stored in the databaseare multiplied by the number of each type of component. An advantage of this method is that the amountsof resources contained in circuit boards for which
resource content information is not available can be
estimated without pulverizing the boards. We are also
investigating the application of image processingCell phone*5

technology for fast and easy automatic recognition ofcomponents from images rather than relying on
visual counting by human workers alone. Such technology would be particularly effective for small andnumerous components such as chip condensers, andfor components that have many varieties and are difficult to classify such as IC chips. We have used thisapproach to clarify that new node circuit boards andcell phones contain many metals that have high economic value and a high risk of depletion as natural
resources (Table 1).
NTT Technical Review

Feature Articles

3.3 Future work in resource visualization
Many valuable material resources are contained intelecom facilities. To provide safe and secure ICT
services in the future, it is necessary to have a stablesupply of resources and to optimize recycling costs.
We believe that advanced recycling based on information on resource contents provided by resource
visualization technology will contribute to achieving
sustainable ICT services. Our objectives in the future
include expanding the targeted equipment, expanding
the database, and improving the estimation accuracy.
We would also like to investigate methods of providing information that take into consideration futurerisks to the environment, economy, and society.

Yasuhiro Higashi

Senior Research Engineer, NTT Energy andEnvironment Systems Laboratories.
He received the B.E. and M.E. in industrial
chemistry from the University of Tokyo in 1988
and 1990, respectively. He joined NTT Applied
Electronics Laboratories in 1990. He wasengaged in R&D of secondary ion mass spectrometry and laser-ionization sputtered neutral
mass spectrometry (1990–1998) and material
analysis services as the surface-analysis groupleader at NTT Advanced Technology Corporation (1998–2001). In 2001, he received the New
Century Award from the Japan Society for Analytical Chemistry. He is currently researchingand developing methods to evaluate telecommunication plant materials. He is a professional
engineer certified by the Ministry of Education,
Culture, Sports, Science and Technology, a certified environmental measurer certified by the
Ministry of Economy, Trade and Industry, aworking environment measurement expert (classI) certified by the Ministry of Health, Labour andWelfare, and a chief telecommunications engineer (chief line engineer) certified by the Ministry of Internal Affairs and Communications.

Vol. 13 No. 3 Mar. 2015

References
[1]
[2]
[3]

[4]
[5]

“Special Issue on Defect Detection by Guided Waves II,” Journal of
the Japanese Society of Non-Destructive Inspection, H. Nishino Ed.,
Vol. 54, No. 11, pp. 585–611, 2005.
M. Shoji and T. Sawada, “Guided Wave Attenuation in a Buried
Cylindrical Rod,” Proc. of the 20th Symposium on Non-destructive
Evaluation by Ultrasonic Waves, pp. 105–108, 2013.
M. Shoji, M. Mizunuma, and Y. Higashi, “Experimental Study ofDefect Detection in Cylindrical Rods by Ultrasonic Guided Waves,”
Proc. of the 21st Symposium on Non-destructive Evaluation by Ultrasonic Waves, pp. 153–156, 2014.
A. Kida, T. Shirohase, and M. Kawaguchi, “Metals Contents including Precious Metals in Waste Personal Computers,” Material Cycles
and Waste Management Research, Vol. 20, No. 2, pp. 59–69, 2009.
K. Halada, K. Ijima, N. Katagiri, and T. Okura, “An Approximate
Estimation of Total Materials Requirement of Metals,” Journal of theJapan Institute of Metals and Materials, Vol. 65, No. 7, pp. 564–570,
2001.

Kazue I. Takahashi

Senior Research Engineer, NTT Energy andEnvironment Systems Laboratories.
She received the B.E. and M.E. in appliedchemistry from Waseda University, Tokyo, in1986 and 1988, respectively, and the Ph.D. inmaterials engineering from the University ofTokyo in 2010. She joined NTT Applied Electronics Laboratories in 1988 and worked on thedevelopment of highly functional polymer materials. In 1998, she initiated a study on methods ofassessing the environmental and social impact of
ICT services. Her primary areas of interest
include visualizing and conserving natural
resources in ICT facilities.

Takashi Sawada

Senior Research Engineer, Group Leader, NTT
Energy and Environment Systems Laboratories.
He received the B.E. and M.E. in electronics
science from Nihon University, Tokyo, in 1989
and 1991, respectively. Since joining NTT in
1992, he has been engaged in R&D of polymer
optical devices and in promoting environmental
management in the NTT Group. He is currently
working on making telecommunication plantmaterials and maintenance technologies moreenvironmentally friendly and reliable.

Feature Articles: Reducing the Environmental Burdenof ICT Services

Materials Technology for the
Production and Storage of Energy
Jiro Nakamura, Takeshi Komatsu,
and Masahiko Hayashi
Abstract

Slowing the progression of global warming is an urgent task, and the NTT Group recognizes the needto reduce the carbon dioxide emissions that come with our corporate activities. Another important
requirement from the viewpoint of the business continuity plan is preparing backup systems in the eventof power failures that result from large-scale disasters. For these reasons, NTT Energy and Environment
Systems Laboratories has been researching and developing materials for producing electrical power andfuels from natural energy sources such as sunlight and materials for storing natural energy to serve as a
backup source of power during power outages. We describe here clean energy systems (artificial photosynthesis, algae, and thermal power generation), which can be used as energy producing materials, andlithium-air rechargeable batteries, which can be used as an energy storage material.
Keywords: rechargeable batteries, artificial photosynthesis, algae and thermal power generation

1. Introduction

2. Energy-storing materials: trends and R&D

There is renewed recognition of the need to achievea sustainable society that does not burden society or
the environment. Particularly in the aftermath of themassive destruction caused by the earthquake that
occurred in eastern Japan in 2011, there is heightenedinterest in technology for energy-producing materials
that make use of renewable energy and unused energy
sources, and technology for energy-storing materials
such as storage batteries (rechargeable batteries).
While much research and development (R&D) is
being done in the fields of materials for energy production and storage, and new technologies are being
introduced, it will probably take some time to develop
a market for such technology. This article describes
R&D on next-generation materials technology thatwill contribute to achieving energy production andstorage systems.

2.1 E
 xpectations for high-performance rechargeable batteries
There is an essential need to install backup electrical power systems to maintain stable communication
services during disasters and the ensuing power outages. Many communication facilities are equippedwith motor-driven electrical power generators andlead-acid batteries as backup power supply systems.
To provide sufficient power for large telecom facilities and datacenters, however, a large amount of
stored fuel or as much as an entire floor of dedicatedlead-acid storage batteries is required. These circumstances have created a need for a new type ofrechargeable battery that has a higher energy density
to provide the same amount of power with less volume and weight than lead-acid storage cells. One
approach to solving this problem is to scale-up thelithium-ion batteries that were initially developed ina smaller form to power mobile phones [1]. Ultimately, however, there is no doubt that a new type ofrechargeable battery that has even higher energyNTT Technical Review

Feature Articles

5
Lithium-ion batteries

Working voltage (V)43Metal-air batteries
Sodium-ion
batteries

2

Batteries with metal
negative electrode(calcium, magnesium,
aluminum, etc.)

10Lithium-sulfide batteries
2000 Wh/kg
1000 Wh/kg
500 Wh/kg

0

200

400
600
800
Discharge capacity (Ah/kg)

1000

1200

*This chart was created using data published by NEDO

Fig. 1. Performance mapping of new types of rechargeable batteries.

density than lithium-ion batteries will be required in
the future.
2.2 L ithium-air rechargeable batteries as a newform of rechargeable battery
A mapping of the performance of new types ofrechargeable batteries, including lithium-ion batteries, provided by the New Energy and Industrial Technology Development Organization (NEDO) [2] ispresented in Fig. 1. We can see from the figure that all
the new types of rechargeable batteries have higher
energy density than lithium-ion batteries. Of those
new types, metal-air batteries have the highest energy
density.
The structure and working mechanism of a lithiumair rechargeable battery is illustrated in Fig. 2 as an
example of a metal-air battery. Conventional batteries
include the active materials of the positive and negative electrodes within the battery. In contrast, oxygen,
which is an active material for the positive (air) electrode of the metal-air battery, is provided from thesurrounding air. Because most of the metal-air battery
is made up of the metal negative electrode, this typeof battery features a very high energy density and along discharge time. The negative-electrode materials
used in metal-air batteries include zinc (Zn), iron(Fe), aluminum (Al), lithium (Li), and other metals.
The battery voltage and energy density differ according to the metal that is used, and the lithium-air
rechargeable batteries provide a high voltage on theVol. 13 No. 3 Mar. 2015

3-V level as well as a higher energy density than batteries using other metals.
NTT Energy and Environment Systems Laboratories has taken these advantages into account and isproceeding with research on lithium-air rechargeable
batteries, which theoretically have a much higher
energy density than lithium-ion batteries, with a viewto using them in the future as an energy buffer fornatural energy sources as well as for backup power
supply systems.
2.3 I ssues facing lithium-air rechargeable batteries
The main thrust in research on lithium-air rechargeable batteries began in the first decade of this century.
Manufacturers and various research organizations are
currently proceeding with basic research to verify thepracticality of this technology, and that work has
shown that lithium-air rechargeable batteries have
low charge/discharge cycle performance, meaningthat the discharge time after charging is short, andthat it is difficult to obtain a large current. Anothertechnical problem that has become clear is the effectof moisture in the air. Various approaches have beentaken to solve these problems by developing battery
materials, and in particular, NTT Energy and Environment Systems Laboratories has been researchingcatalysts that can enhance the reaction rate at the air
electrode [3–7].

Feature Articles

e−Electrolyte solution

Air electrode(positive electrode)

Negative electrodeLi metal
O2

Li ionAir electrode: 2Li + O2 + 2e
Negative electrode: Li
Li+ + e−
+

Li2O2
−

Li2O2

Li: lithium

Fig. 2. Working mechanism of lithium-air rechargeable batteries (discharge reaction).

2.4 H
 igher charge/discharge performancethrough development of air electrode catalysts and electrolyte optimization
Our research shows that ruthenium oxide has higher activity than conventional catalysts. The initialcharge/discharge curves of lithium-air rechargeable
batteries that use a ruthenium oxide catalyst and aconventional manganese oxide catalyst are shown in
Fig. 3. We can see that the ruthenium oxide catalyst
has a higher discharge voltage and a larger discharge
capacity, and that the charge voltage is low and thecharge capacity is large. These results indicate thatruthenium oxide has higher catalytic activity thanconventional catalysts.
The choice of electrolyte solution is another important factor in improving the cycle performance. A
comparison of the charge/discharge performance fora lithium-air rechargeable battery that uses a conventional carbonate ester-based electrolyte and a battery
that uses a newly selected di-ether-based electrolyte
is shown in Fig. 4. We can see a clear improvement in
the cycle performance with the di-ether-based electrolyte.
These results indicate that optimization of battery
materials is important for improving the charge/discharge cycle and other aspects of battery performance.


2.5 A new future with high-performance
rechargeable batteries
If high-performance rechargeable batteries thathave high energy density can be made practical, it
will be possible to greatly reduce the size and weightof backup power supplies, which are currently heavy
and consume a lot of space. In telecom facilities that
dedicate as much as an entire floor of the building to
the backup power supply, that would free up a large
amount of space that could be used for servers orother equipment. If batteries with sufficiently highcycle performance can be achieved, it would expand
the range of applications beyond backup systems. For
example, large rechargeable batteries introduced to
private residences would allow power to be stored
during the night when rates are relatively low, for use
during the day. It would also allow homes that havesolar panels but do not use much power during the
day to store power for use at night. Such peak power
cutting or shifting to reduce power consumption canhelp reduce carbon dioxide emissions.
3. Energy-producing materials:
trends and R&D
Concerns about the problem of the contribution ofcarbon dioxide, methane, and other greenhouse gases
NTT Technical Review

Feature Articles

Measurement atmosphere: room temperature, dry air
Current density: 0.1 mA/cm2
Electrolyte: carbonate ester-based solution
4.5
Conventional catalyst: manganese oxide
ChargeBattery voltage (V)4High activation
3.5

New catalyst:
ruthenium oxide

3High activation
2.5
Conventional catalyst:
manganese oxide

Discharge

2
0

100

200

300

400

500

600

700

Discharge capacity (mAh/g)

Fig. 3. Initial charge/discharge curves of lithium-air rechargeable batteries using a ruthenium oxide catalyst.

Discharge capacity (mAh/g)

1000

Di-ether-based
electrolyte solution

500

Carbonate ester-based
electrolyte solution
0

0

1

2

3

4

5

6

7

Charge/discharge cycle time
RuO2: ruthenium oxideFig. 4. Dependence of cycle performance on electrolyte
solution of lithium-air rechargeable battery using a
RuO2 catalyst.

on global warming, as well as the problem of dwindling fossil fuel resources have been increasing year
by year. This has led to an increase in the demand fordevelopment of clean energy technology for utilizing
renewable and unused energy. In contrast to energythat is derived from petroleum, coal, natural gas, andother fossil fuels, renewable energy exists in the natuVol. 13 No. 3 Mar. 2015

ral world in the form of sunlight, wind, and geothermal heat, for example. Unused energy includes heatcontained in rivers and drainage systems and the heatgenerated by power transformer substations. In particular, these forms of energy are characterized as
non-depletable and present everywhere, and they do
not emit greenhouse gases or increase the emission ofgreenhouse gases. Such energy sources therefore
have the potential to be a radical solution to the problems mentioned above when used well. We have been
focusing efforts on using these forms of energy in thedevelopment of green energy technology including
green fuels, green power generation, and the capturing of carbon dioxide. We describe here a green fuelbased on artificial photosynthesis, the use of microalgae to capture carbon dioxide, and thermoelectric
conversion as a means of green power generation.
3.1 Research on artificial photosynthesis
Artificial photosynthesis is a process that mimics
the photosynthesis of plants by using sunlight tocause a reaction between carbon dioxide and water inorder to produce fuels such as hydrogen, carbon monoxide, formic acid, methanol, and methane (Fig. 5).
The artificial photosynthesis process uses renewableenergy from sunlight (non-fossil fuel) and consumes
carbon dioxide, which is a cause of global warming.
Currently, though, the efficiency of converting solar
energy in the conversion of carbon dioxide to methane and other fuels is very low, and the process isFeature Articles

Plant photosynthesis

Artificial photosynthesis

Water
Water

OxygenOxygenCarbon dioxide
Carbon dioxide

Carbohydrate (sugar)

Hydrogen,carbon monoxide,
formic acid, methanol,
methane, etc.

Fig. 5. Comparison of artificial and natural photosynthesis.

tion as a fuel resource that does not compete withfood sources. Microalgae have a very high rate of
reproduction compared to terrestrial plants, as well asa high lipid content and a carbon dioxide capture
capability about 10 times higher than a forest. We
have been conducting R&D on a system for chemically capturing carbon dioxide using microalgae [9,10]. We have also been investigating the effects ofgrowth conditions such as the composition of thecultivation medium and temperature, and evaluating
the growth rate of algae and the amount of carbon
dioxide capture with the objective of optimally controlling the cultivation conditions (Figs. 7 and 8).

Fig. 6. Exposure to sunlight produces reaction gases(mainly hydrogen) on the electrode (rod).

inferior to natural photosynthesis. We are therefore
investigating the use of photocatalytic thin films anda way to improve the performance by modifying thethin-film surface with promoters [8]. So far, we haveused known photocatalysts for the thin-film, constructed a system for evaluating performance, andconfirmed the generation of hydrogen, methane, andcarbon monoxide by instigating a reaction between
carbon dioxide and water (Fig. 6).
3.2 Research on microalgae
Algae, especially microalgae, are attracting atten

3.3 Research on thermoelectric conversion
Thermoelectric conversion is a process in whichelectrical power is generated when there is a temperature gradient within a thermoelectric element. The
thermoelectric element comprises p-type and n-typesemiconductors that are arranged in a π-type series(Fig. 9). The use of inorganic materials for thermoelectric elements is widely known, but there are problems with their widespread use in general society, as
they contain rare or toxic metals, and are hard andheavy. For that reason, we are researching organic
thermoelectric conversion materials. Organic materials offer the potential for lightness, workability, andflexibility. They are also less expensive and have less
impact on the environment because they contain norare metals. However, organic materials have lower
thermoelectric conversion efficiency than inorganic
materials, so there is a need to raise that efficiency.
We have therefore been moving forward with thedevelopment of practical thermoelectric elements
NTT Technical Review

Feature Articles

Fig. 7. Microalgae cultivation.

Fig. 10. Thermoelectric element (1 square inch).

Cultivator (#1)
Cultivator (#2)

with two objectives: raising the element performanceand increasing the element surface area [11]. We havealready achieved an element surface area of one
square inch (Fig. 10).
4. Future prospects
Natural energy such as sunlight and unused energy
such as waste heat can be found everywhere. It is
important to collect these forms of energy efficiently
and convert them into high-quality energy. By
advancing the basic materials research, we aim todramatically improve the efficiency of such processes.

Fig. 8. Outdoor cultivators (on the grounds of the Atsugi
R&D Center).

References
[1]
[2]

–

Waste heat+[3]

p-typesemiconductors

n-typesemiconductors+–
Cooling
Current

Electrode

[4]

[5]

Resistance[6]

Fig. 9. Thermoelectric conversion principle.
[7]Vol. 13 No. 3 Mar. 2015

Web site of NTT FACILITIES, Products & Services, lithium-ion batteries (in Japanese).
http://www.ntt-f.co.jp/service/products_service/lib/
New Energy and Industrial Technology Development Organization(NEDO), Secondary Cell Development Roadmap, August 2013 (inJapanese).
http://www.nedo.go.jp/content/100535728.pdf
M. Hayashi, H. Minowa, M. Takahashi, and T. Shodai, “Surface Properties and Electrochemical Performance of Carbon Materials for Air
Electrodes of Lithium-Air Batteries,” Electrochemistry, Vol. 78, No.
5, pp. 325–328, 2010.
H. Minowa, M. Hayashi, M. Takahashi, and T. Shodai, “Electrochemical Properties of Carbon Materials and La0.6Sr0.4Fe0.6Mn0.4O3
Electrocatalysts for Air Electrodes of Lithium-air Secondary Batteries,” Electrochemistry, Vol. 78, No. 5, pp. 353–356, 2010.
M. Hayashi and T. Shodai, “Metal-air Secondary Battery Development,” in Towards Innovation in Storage Batteries: Metal-air Secondary Cells, Electrochemistry, Vol. 78, No. 6, pp. 529–539, 2010 (inJapanese).
H. Minowa, M. Hayashi, T. Shodai, and K. Saito, “Metal-air Secondary Cell R&D, Present and Future,” Chapter 5 in Metal-air Secondary
Cell Development and Most Recent Technology, Gijutsu Kyoiku Publishing, pp. 57–69, April 2011 (in Japanese).
M. Hayashi and T. Tsujikawa, “Secondary Battery Technology inFeature Articles

[8]

[9]

Support of Telecom Services,” Special Issue on Leading-edge Secondary Cell Development and Use and Related Issues, Electrical
Review, Vol. 97, No. 6, pp. 39–43, June 2012 (in Japanese).
Y. Ono, J. Nakamura, M. Hayashi, and K.I. Takahashi, “Effect ofSubstituent Groups in Rhenium Bipyridine Complexes on Photocatalytic CO2 Reduction,” American Journal of Applied Chemistry, Vol. 2,
No. 5, pp. 74–79, 2014.
T. Yamada, Y. Ono, M. Takenaka, M. Ota, and H. Inomata, “Nondestructive Measurement of Microalgae Density by Image Analysis,”
Proc. of The 9th Asia-Pacific Marine Biotechnology Conference,
Abstracts p. 122, Kochi, Japan, July 2012.

Jiro Nakamura

Project Manager, Green Material Project, NTT
Energy and Environment Systems Laboratories.
He received the B.E., M.E., and Ph.D. inapplied chemistry from Osaka University in
1987, 1989, and 1995, respectively. He joined
NTT LSI Laboratories in 1989 and worked on thedevelopment of microfabrication technology. He
moved to the NTT Information Sharing Laboratory Group in 2001 and engaged in the development of environmental sensing systems and inanalyzing the influence of ICT on the global
environment until he moved to his present
research department in 2004. He received thePaper Award at the MicroProcess Conference in1997 and the Science and Technology Award at
the Photopolymer Conference in 1998.

[10] M. Takenaka, Y. Ono, T. Yamada, M. Ota, Y. Sato, and H. Inomata,“Effects of External Factors on Growth of Chlorococcum Littorale,”Proc. of The 9th Asia-Pacific Marine Biotechnology Conference,
Abstracts p. 128, Kochi, Japan, July 2012.
[11] A. Kohno, S. Ogawa, and Y. Somemura, “Effect on Thermoelectric
Property of Conductive Polymer by Adding Polyols,” Proc. of the 7thInternational Symposium on Organic Molecular Electronics (ISOME
2012), Tokyo, Japan, June 2012.

Masahiko Hayashi

Senior Research Engineer, Green Material
Project, NTT Energy and Environment Systems
Laboratories.
He received the B.E., M.E., and Ph.D. inapplied chemistry from Kyushu University,
Fukuoka, in 1995, 1997, and 2000, respectively.
He joined NTT in 2000 and has been engaged inresearch on battery materials, in particular, alithium-air secondary battery. He is a member ofthe Electrochemical Society of Japan.

Takeshi Komatsu

Senior Research Engineer, Green Material
Project, NTT Energy and Environment Systems
Laboratories.
He received the B.S. and M.S. in physics from
Yokohama City University, Kanagawa, and the
Ph.D. in engineering from Nagaoka University ofTechnology, Niigata, in 1996, 1998, and 2007,
respectively. He joined NTT in 1998 and until
2010 conducted research on fuel cells, in particular, a solid-oxide fuel cell. He was with the NTT
Environmental Protection Office from 2010 to2013. He has been with the Green Material Project since 2013. He is a member of the Electrochemical Society of Japan.



NTT Technical Review

Feature Articles: Reducing the Environmental Burdenof ICT Services

Efforts to Improve Energy Efficiencyof Network Service System
Junichi Koga, Takashi Kurimoto, Takafumi Hamano,
Atsushi Terauchi, and Masahiro Miyasaka
Abstract

NTT Network Service Systems Laboratories is developing network architecture and supporting technologies towards a future network that will enable a service-oriented platform and the creation of newvalue along with the Hikari Collaboration Model. This article describes our efforts in improving theenergy efficiency of network service systems such as routers and servers.
Keywords: telecommunications carrier network, network service system, energy efficiency

1. Introduction
In 2014, NTT announced it would shift its businessmodel to provide the world’s first full-scale wholesaling of a fiber access service in order to stimulate theJapanese ICT (information and communication technology) market [1]. To accelerate the evolution of
network and operation technologies to support the
new business model, NTT Network Service Systems
Laboratories has been carrying out research anddevelopment (R&D) towards achieving a service-oriented network in which network resources and functions are modularized in order to provide themquickly and flexibly according to a service player’s
request.
Building on the concept of the service-oriented
network, we focus here on discussing the future network, which is intended to create new value in various ways, to provide network functions to meet
diverse needs, and to provide a social infrastructurethat is secure, stable, and economical. The objectivesof the future network are to reduce capital expenditures (CAPEX) by drastically simplifying the network, and to reduce operating expenses (OPEX) byintroducing virtualization for more flexible and efficient use of resources through integration of advanced
operations across the entire network (Fig. 1). We areinvestigating network architectures and developing
support technologies in order to achieve these goals.


We are also researching system architectures of network service systems that increase energy efficiency.
In this article, we describe our work on reducing
power consumption for the transport network system,
server system, and operation system.
2. Transport network systems
We aim to achieve a 50% reduction in power consumption in the transport network system throughefforts focused on each part of the network.
For link systems, we are working on energy-efficient transmission methods to support a future
increase in network capacity, and on a network control method that makes use of equipment with low
energy consumption. For the core network, we areinvestigating terabit-class optical transport methods
that can reduce the power consumption per bit underhigh-volume traffic by combining high-density wavelength path multiplexing with the use of energy-efficient devices. For metro networks, standardization ismoving forward for short- to medium-distance optical transmission methods that are expected to be usedwith devices that have higher energy efficiency thanthose used for long-distance optical transmission.
Our objective is to establish network control schemesthat can reduce power consumption by using suchenergy-efficient transmission methods.
We are considering two steps to reduce the cost and
NTT Technical Review

Feature Articles

Business partners(service players)

Service system

VM

NW
functions

Orchestrator

VM

Commodity HW

NW
functions
VM

Servercontroller

NW
functions
VM

Transport network
systemLower OPEX throughintegrated, high-speed
operations across theentire network

NW
controller

Commodity HWLower CAPEX
through drastic
network simplification

Operation systems

NW
functions

Higher resource
flexibility and efficiency
through virtualization

NTT Group

Collaboration

Forwarding
systemForwarding
systemLink system

Link system
Transport network

10G-OLT/ WDM/TDM access
HGW

Fixed

MobileWi-Fi

NW: network
HGW: home gateway
HW: hardware
OLT: optical line terminal
TDM: time-division multiplexing
WDM: wavelength-division multiplexing

Fig. 1. Future network architecture.

power consumption of packet forwarding systems.
The first step is a drastic network simplification. We
aim to aggregate the functions and shift them towards
the network core. In the future network, we aim todevelop large capacity edge routers that can accommodate more subscribers in order to reduce the total
number of edge routers. In the next step, we aim to
make greater use of general purpose products as network nodes. The concept of MSF (multi-service fabric) is an effort to reduce transport system cost andpower consumption by enabling a shift from conventional ways of carrier network deployment. Instead ofusing high-performance, large-scale routers that havehigh per-bit power consumption, we aim to form a
network with resources provided virtually by a set ofcommodity switches and servers. These switches andVol. 13 No. 3 Mar. 2015

servers are handled as modules that can be combinedin accordance with changing demands such as thosefor traffic load, launching new services, and failover.
3. Server systems
Server systems are aimed to be much more flexibly
configured based on network function virtualizationin order to maximize the advantages of resource sharing and to launch new services quickly.
Network systems for conventional telecommunication services consist of a wide variety of components,
each of which has been developed as a separate unit
to provide a specific function. To satisfy service quality and reliability with a set of such components, thecapacity has been designed with a certain amount ofFeature Articles

redundancy so that it can maintain the required performance and availability even in the event of a sudden traffic increase and equipment failure. The newserver platform in the future network will adopt a
distributed architecture that combines multiple general-purpose servers that are compact and inexpensive. In the proposed architecture, service quality will
be maintained by adding or removing server resources as needed in order to cope with the load on thesystem, and the required reliability will be achieved
without installing redundant systems by providing
backup data storage in machines that are currently
being used. By using resources efficiently in this way,
we expect to be able to reduce the number of servers
and the power consumption by one-half relative to theconventional network while maintaining service
quality and system reliability.
4. Operation systems
For the future network, we are developing a new
network management mechanism called an integrated
management, operation, and orchestration system(MOOS) that enables us to achieve comprehensive
network operation through the network layer to theservice layer.
With current networks, a network administrator
uses various operation systems (OpS) dedicated to
specific network equipment or a specific network
layer. In the future network, MOOS will make it possible to conduct integrated and advanced operations
for the entire network. By using MOOS, we can
expect to 1) reduce the operations workload by introducing real-time network configuration and automation failure recovery, and 2) increase the efficiency ofremote and on-site operation by using network virtualization technology that can realize service management that is independent of equipment management.
By achieving these two objectives, we can reduce theresources required for operations (for example, ondemand, on-site failure recovery will not be needed),
and the overall electronic power consumption in network operations will also be reduced.
In regard to the power consumption by the OpS
itself, achieving the first of the above two objectives
can be expected to reduce the amount of OpS equipment such as by eliminating the need for a console.
The accomplishment of the second objective will
make it possible to reduce the number of servers andthe network equipment to be managed, and the OpS
facilities for such devices will also be reduced. As aresult, we can achieve a great decrease in power consumption related to network operations by using
MOOS.
5. Future plans
We have described our efforts to reduce the power
consumption of the network service system. In moving forward with future network R&D, NTT Network
Service Systems Laboratories will continue to takevarious approaches to energy conservation beyond
the work reported here with the objective of reducing
overall power consumption in the NTT Group.
Reference[1]“Hikari Collaboration Model,” NTT press release published on May
13, 2014.
http://www.ntt.co.jp/news2014/1405eznv/pdf/ndyb140513d_all.pdf

NTT Technical Review

Feature Articles

Junichi Koga

Atsushi Terauchi

Senior Research Engineer, Network Systems
Planning & Innovation Project, NTT Network
Service Systems Laboratories.
He received the B.S. and M.S. in condensed
matter physics from Kyushu University, Fukuoka, in 1997 and 1999, respectively. He joined
NTT Network Service Systems Laboratories in
1999. His research interests include high-availability server systems and session control servers. He is a member of the Institute of Electronics, Information and Communication Engineers(IEICE).

Senior Research Engineer, Operation Innovation Project, NTT Network Service Systems
Laboratories.
He received the B.E. in control engineeringfrom Osaka University and the Ph.D in engineering from Waseda University in 1991 and 2007
respectively. He joined NTT in 1991 and moved
to NTT Network Service Systems Laboratories
in 2013. His research interests include network
virtualization and future network operations. He
is a member of IEICE and IEEE (Institute ofElectrical and Electronics Engineers) Computer
Society.

Takashi Kurimoto

Masahiro Miyasaka

Senior Research Engineer, Transport Service
Platform Project, NTT Network Service Systems
Laboratories.
He received the B.E. and M.E. in applied physics from Tokyo Institute of Technology in 1992
and 1994, respectively, and the Ph.D. in engineering from Keio University, Tokyo, in 2012. In
1994, he joined NTT Network Service Systems
Laboratories. He has been engaged in researching switching technology for high-speed computer networks and multimedia communication
networks. He received the IEICE Switching
System Research Award in 1996.

Senior Research Engineer, Server Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. in engineeringscience from Osaka University in 1996 and 1998,
respectively. He joined NTT Network Service
Systems Laboratories in 1998 and engaged in
R&D of high-availability server systems for session control technologies. He is now researchingserver platform systems for service innovation.
He is a member of IEICE.

Takafumi Hamano

Senior Research Engineer, Transport Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.E. and M.E. in engineeringfrom Kyoto University in 1994 and 1996, respectively. He joined NTT in 1996 and moved to NTT
Network Service Systems Laboratories in 2002.
His research interests include next-generationtransport network architecture and systems. He isa member of IEICE.

Vol. 13 No. 3 Mar. 2015



Feature Articles: Reducing the Environmental Burdenof ICT Services

Issues and Solutions in Saving Energyof Optical Access Network
Equipment
Hirotaka Ujikawa, Tomoko Shibata, and Ken-ichi Suzuki
Abstract

High-speed web browsing and high-resolution video content have become commonplace for end users
with the help of recent high-performance user terminals. However, this results in continuous increases
in both the use frequency and the volume of data traffic in the network, so an improvement in the capacity of the network is highly expected. However, the potential increase in power consumption of network
nodes is a serious concern, as it is already at a significant level in current systems. Therefore, much effort
is being focused around the world on finding ways to construct the next generation of network systems
without increasing the power consumption. This article introduces issues specific to the optical accessnetwork, which represents a significant part of the power consumption in the entire network system, anddescribes the contribution of NTT Access Network Service Systems Laboratories in tackling theseissues.
Keywords: optical access network, power conservation, cyclic sleep

1. Introduction
The architecture of the current 1-Gbit/s-capable
FTTH (fiber-to-the-home) system, which is widely
deployed for high-speed Internet services, consists ofmultiple network nodes, as illustrated in Fig. 1. The
entire network can be roughly divided into two parts:
the access network part, which is close to the end
user, and the core network part. While the power consumption of one node in the core network is muchlarger than that of one node in the access network, thetotal consumption is greater in the access network
because of the number of users each node is capableof serving [1]. Consequently, the per-user power consumption of the access network node is significantly
larger. Therefore, tackling the issues related to thepower consumption of the access network nodes will
greatly contribute to reducing the total power of theentire network system.



2. Issues in power conservation of
network nodes
There are several methods of reducing the power
consumption of electrical devices, although somemethods can affect the quality of service. Generally,
the more a method reduces power consumption, themore adversely it affects network services. Moreover,some methods are only effective for specific types ofnodes and are not effective on the others.
For example, user terminals such as personal computers (PCs) can accurately detect the usage of theend user by directly receiving user operations throughinput interfaces such as a mouse click. With this precise information about user operations, user terminals
can control the power saving functions according to
the usage. Unlike this example, the intermediate network nodes must control the power saving functions
by monitoring the network traffic and estimating theusage so as not to induce adverse effects on the user
application.
Another difficulty specific to the network nodes is
NTT Technical Review

Feature Articles

Customer premises

Central officeCore
network

PON
UNI
ONU

L2SW

OLT

PC
ONU
Access network
ONU

OLT L2SW Core network

60%

7%

14%

19%

PON: passive optical network
ONU: optical network unit
OLT: optical line terminal
L2SW: layer 2 switch
UNI: user network interface

Fig. 1. Power consumption ratio in the entire network system.

their simplicity. The network nodes are basicallyequipped with only communication functions, which
is different from the user terminals that have various
rich functions. While user terminals can conserve
power by turning off the unused functions, the network nodes’ method of saving power is limited totemporarily suspending the communication function
when there is no traffic. Furthermore, the componentsthat take a long time to wake up cannot be turned off
because that could induce an additional delay, which
also restricts the power saving of the network node.
3. Issues specific to optical access networks
Moreover, there are further difficulties in power
conservation of network nodes specific to opticalaccess networks. The network nodes in the core network (e.g., servers and routers) accommodate traffic
from a huge number of users. Because this aggregatedtraffic in the core network is expected to vary smoothly with time by the statistical multiplexing effect,effective power saving is also expected to be achievedat these nodes by reducing the number of active ports
or packages of the processing unit. However, the traffic in the optical access network changes so drastically that it is difficult to estimate. Additionally, thenodes in the optical access network are often configured without redundancy such as that of a duplex
system. Therefore, these power saving approaches
Vol. 13 No. 3 Mar. 2015

are not applicable for optical access nodes that
accommodate a small number of users. The appropriate power saving control technique for the opticalaccess network should be able to precisely turn components on and off taking the bursty traffic into
account.
4. Characteristics of traffic in the opticalaccess network
We focus here in particular on Internet traffic via an
optical access network because the other traffic generated by VoIP (Voice over Internet protocol) and
IPTV (Internet protocol television) services can belogically distinguished from Internet services, and it
is easier to determine whether they are in use.
While the amount of downloaded data from theInternet has been increasing year after year, it is muchsmaller than the potential capacity that the opticalaccess network offers if we take unused time into
account. For example, the most frequent value of thetraffic volume in 2014 was reported to be 28 MB/day
uploaded and 447 MB/day downloaded by one user[2]. Under the assumption that these data could betransferred in bulk, the upload and download would
be completed in less than 4 s with an ideal 1-Gbit/s
network. In theory, this indicates that most of the timein a day could be considered as resting time for the
network nodes, as they do not have to transmit orPower consumption of ONU

Feature Articles

Awakes to avoid link disconnect by timeout

Awake

Active
Sleep

Sleep

Sleep

Downstream
traffic

Upstreamtraffic

timePower consumption of ONU

Fig. 2. Start and continuation of Tx sleep.

Awake
Awake

Awake

Sleep

Sleep

Upstreamtraffictime

Fig. 3. Termination of Tx/TRx sleep caused by upstream traffic.

receive user data. In fact, however, the access nodes
have to control the timing to apply power saving
functions in order not to induce adverse effects on theuser experience.
5. Effect of suspending communication
functions
Specifically, the adverse effect induced by suspending the communication function of the access nodes
is additional delay of the head packets, which are partof the packets successively generated by an application. It used to take several minutes for a PC to wakeup from standby mode, so the head packets had to
wait for the suspended devices to wake up. Because
the actual delay would differ according to which
components were suspended, we introduced sleep
modes based on the standardized optical network unit
(ONU) power saving of IEEE (Institute of Electricaland Electronics Engineers) Standard 1904.1-2013[3]. There are two representative sleep modes, namely transmitter (Tx) sleep, which suspends the opticaltransmitter, and transceiver (TRx) sleep, which suspends the optical transceiver on the passive optical
network (PON) side.



5.1 Tx sleep
Tx sleep is designed to suspend the functionalities
in relation to the upstream data transmission of the
ONU. Because the ONU has an Ethernet port on theuser network interface (UNI) side, the ONU can
immediately wake up by detecting the upstream input
to the UNI even while the ONU turns off the opticaltransmitter on the PON side. The PON linkage
between the ONU and the optical line terminal (OLT)
at the central office is not disconnected by the timeout
unless the ONU suspends the optical transmitter for along time with no packet transmission. Therefore, theadditional delay in applying Tx sleep would be limited to almost the same length of time as required towake up the optical transmitter of the ONU regardlessof the sleep duration while the sleep duration is lessthan 1 s (Figs. 2 and 3).
5.2 TRx sleep
In contrast, TRx sleep is designed to further suspend the functionalities in relation to the downstream
data reception of the ONU. To detect the notificationof downstream data arriving at the OLT, the ONU has
to periodically turn on the optical transceiver. Therefore, the additional delay in TRx sleep would belengthened according to the period in the worst case,
NTT Technical Review

Power consumption of ONU

Feature Articles

Awakes to confirm the downstream traffic

Awake

ActiveSleep Upstream or
downstream
traffic

Sleep

Awake

Sleep

Awake

Sleep

Awake

Sleep

Sleep

time

Power consumption of ONU

Fig. 4. Start and continuation of TRx sleep.

Awake

Delay

Awake

Awake
Sleep

Sleep

Sleep

Downstream
traffictime

Fig. 5. Termination of TRx sleep caused by downstream traffic.

even if the wakeup time of the transceiver is short(Figs. 4 and 5).
6. Controlling the effect of ONU sleep
More effective power saving can be expected with
TRx sleep than with Tx sleep by suspending a wider
range of components in the ONU. Meanwhile, a conservative control that does not adversely affect theuser application is necessary for TRx sleep. A typicalcontrol is to set a guard time so that the sleep period
does not start for a certain period of time after apacket arrives, which would be effective for continuous packet generation while the application was inuse.
However, a few types of traffic flow are automatically generated in the access network even while theuser is not actively using an application. For example,
some protocols periodically send packets to eachother in order to detect a fault quickly in the communication path. In these circumstances, the ONU will
not start the sleep during the guard time, which isconstantly extended by the periodic arrival, and theeffectiveness of power conservation would be significantly constrained.
Therefore, we have proposed an adaptive control
Vol. 13 No. 3 Mar. 2015

method for TRx sleep that enables the length of theguard time to be changed (Fig. 6). When the numberof arrived packets is so small that it can be assumed
to be automatically generated traffic consisting ofkeep-alive messages, the controller reduces the guard
time. When the number of arriving packets exceeds
the threshold, the ONU extends the guard time toprevent the additional delay that directly affects theuser experience, assuming that the user is actively
using the applications. We confirmed in experimentsthat these proposed methods can reduce the average
power consumption by 20 percent at maximum when
the automatic keep-alive messages are frequently
generated.
7. Future direction
In an era of IoT (Internet of things), where a variety
of sensors would automatically communicate withthe servers more frequently even without any humanoperations, the traffic characteristics would experience a drastic change. Because there is a close relationship between the power saving of network nodes
and network traffic, especially in an optical accessnetwork, as introduced in this article, we have to pay
constant attention to traffic trends in order to develop
Feature Articles

Number of frame arrivals ≥ threshold

Number of frame arrivals < threshold

Extended guard time

Shortened guard time

time
Awake
Sleep

time

Awake

Awake

Sleep

Sleep

Awake
Sleep

Awake
Sleep

Power consumption ratio

Constant guard time to prevent
additional delay by sleep
1
0.95

Reduced power consumption withadaptively shortened guard time

0.9
0.85

Adaptively shortened
guard time

0.8
0.75
0.1

1
10
100
Number of arrived frames in one second

Fig. 6. Power reduction with proposed adaptive guard time control.

energy efficient network systems.

[2]

References[1]

A. Otaka, “Power Saving ad-hoc Report,” Proc. of IEEE 802.3 Interim
Meeting, Seoul, South Korea, September 2008.
http://www.ieee802.org/3/av/public/2008_09/3av_0809_otaka_1.pdf[3]

K. Cho, “Broadband Traffic Report—Traffic Volumes Rise Steadily
Over the Past Year, and HTTPS Use Expands,” Internet Infrastructure
Review (IIR), Vol. 24, pp. 28–33, August 2014.
http://www.iij.ad.jp/en/company/development/iir/pdf/iir_vol24_
report_EN.pdf
IEEE Std. 1904.1-2013,“Service Interoperability in Ethernet Passive
Optical Networks (SIEPON),” 2013.

NTT Technical Review

Feature Articles

Hirotaka Ujikawa

Engineer, Optical Access Systems Project,
NTT Access Network Service Systems Laboratories.
He received the B.E. and M.E. in computerscience from Waseda University, Tokyo, in 2007
and 2009, respectively. In 2009, he joined NTT,
where he has been engaged in research anddevelopment (R&D) of optical access systems.
His current research interests include dynamic
bandwidth allocation and dynamic sleep scheduling for energy efficient optical access systems.

Tomoko Shibata

Senior Research Engineer, Optical Access
Systems Project, NTT Access Network Service
Systems Laboratories.
She received the B.S. in chemistry from Hokkaido University in 1995. She joined NTT
Access Network Service Systems Laboratories in
1995. She is currently engaged in R&D of opticalaccess systems. She is a member of the Instituteof Electronics, Information and Communication
Engineers (IEICE).

Vol. 13 No. 3 Mar. 2015

Ken-ichi Suzuki

Senior Research Engineer, Supervisor, Group
Leader of Full Service Access Group, NTT
Access Network Service Systems Laboratories.
He received the B.E. and M.E. in electronicengineering from Utsunomiya University, Tochigi, in 1988 and 1990, respectively, and the Ph.D.
in information science and technology from
Hokkaido University in 2009. He joined NTT
laboratories in 1990, where he has been working
on R&D of optical communication systems
including PON based optical access systems. He
currently leads the Access Systems Technology
Group, which is investigating optical access
related services/technologies. His current
research interests are 10G-EPON related opticalaccess systems/technologies and optical-amplifier-based long-reach PON systems/technologies. He is an IEEE 802.3 Working Group (WG)
voter and was an active member of the IEEE
P802.3av Task Force creating 10G-EPON standardization. He has been a Vice Chair of IEEE
P1904.1 SIEPON WG since 2011 and was an
executive secretary of IEEE P1904.1 SIEPONWG during 2009–2011. He has been a Directorof the Optical Access Adhoc WG in HATS (Harmonization of Advanced Telecommunication
Systems) Conference of Japan for EPON familyinteroperability tests since 2012. He is a memberof IEEE, IEICE, and the Optical Society ofAmerica. He has also been a member of theTechnical Committee on Communication Systems in IEICE Communication Society since2008 and was an associate editor of IEICE Transactions on Communications during 2007–2011.
He was the TPC (Technical Program Committee)
Secretary of IEEE CQR (Communications Quality and Reliability) in 2012, 2013, and 2014.

Feature Articles: Reducing the Environmental Burdenof ICT Services

HVDC Power Supply System
Implementation
Toru Tanaka, Jun Kato, Atsushi Sakurai, Takeshi Iwato,
Mikio Shintaku, Akiko Takahashi, Koki Asakimori,
Naoki Hanaoka, Hiroaki Matsumori,and Nobuhiko Yamashita
Abstract

The high-voltage direct current (HVDC) power supply system is ready to implement and is expected
to reduce energy consumption and costs in telecommunication buildings and datacenters. In this article,
we explain the implementation status of this system and discuss standardization efforts. We also review
the technical requirements and power supply system guidelines that were developed by the NTT Groupto further promote HVDC systems.
Keywords: HVDC power supply system, technical requirements, power supply system guideline

1. Introduction
The NTT Group is working on various energy-saving measures for telecommunication buildings anddatacenters. At NTT Energy and Environment Systems Laboratories, we have developed a high-voltage
direct current*1 (HVDC) power supply system to supply power to information and communication technology (ICT) equipment in collaboration with NTT
Group companies. It is the world’s first such system,
and we are now shifting to the introduction stage.
The HVDC power supply system uses DC 380 V,
which is converted from commercial AC (alternating
current) 200 V, and it supplies power to ICT equipment while charging the batteries [1]. If a power outage occurs, the battery directly supplies power to ICT
equipment and acts as a backup to maintain the system until the upper engine generator starts and anengineer arrives.
A comparison of a conventional AC power supply
system, 48 VDC power supply system, and our
HVDC power supply system is shown in Fig. 1.
The AC power supply system is mainly used indatacenters. However, power loss is greater than inDC systems due to the many conversion stages. Also,a DC to AC converter is necessary between the ICT
equipment and the battery. Therefore, system reliability is the lowest of the three systems in Fig. 1.
The 48 VDC power supply system is used in telecommunication buildings because it has a simple
configuration and is highly reliable. However, thepower consumption of ICT equipment has been
increasing in recent years. Therefore, thick cables areneeded, which causes problems in installation andsystem positioning.
Our HVDC power supply system is based on theconcept of the 48 VDC power supply system. It istherefore highly reliable and efficient. In addition, theuse of high voltage means that it does not requirelarge-diameter cables.
We organized the entire configuration of the HVDC
power supply system and developed various power
supply devices such as rectifiers, power distribution
frames, and power outlets in cooperation with NTT*1	 High voltage direct current: DC power supply systems in the ICT
industry generally use 48 VDC. A voltage range of about 300–
400 VDC is called high-voltage direct current.

NTT Technical Review

Feature Articles

AC power supply system
UPS
AC
DC
1

DC
AC
2

48 VDC power supply system
ICT equip.

100–200
VAC

AC
DC
DC
DC
3
4

DC power supply equip.
AC
DC
1

MB

Battery

Total losses
can be reduced.

48 VDC

DC
DC
2

MB

Battery

4 conversion stages: Complicated• Higher efficiency(fewer conversion stages)• Higher reliability(direct battery connection)

ICT equip.

2 conversion stages: Simple

HVDC power supply system
HVDC power supply equip.
ACDC
1

ICT equip.

380 VDC

DC
DC
2

MB

• Lower installation cost(small diameter cables
are possible)• Flexible installation
Building cost
can be reduced.

Battery
2 conversion stages

MB: Motherboard

Fig. 1. HVDC power supply system.

Group companies.
To improve safety, we developed a non-exposedconnector and an outlet to avoid the risk of electric
shock. We also devised a grounding scheme so thateven if an accidental electric shock occurs, the current flowing through the human body will be suppressed. We also developed a fuse and power distribution frame to ensure electrical stability during an
accident such as a short circuit in ICT equipment.
Even if a circuit breaker or a fuse trips or opens, thevoltage fluctuation does not affect the other ICT
equipment. The power supply devices and grounding
scheme we developed are shown in Fig. 2.
2. International standardization
International standardization is necessary to promote our HVDC power supply system. Therefore, we
are actively involved in standardization efforts in theInternational Telecommunication Union, Telecommunication Standardization Sector (ITU-T), and wehave contributed to efforts to publish the requirements of the input port of ICT equipment (L.1200)
and the power supply system configuration (L.1201)[2, 3]. These activities are expected to promote theimplementation of the HVDC power supply systemworldwide and to increase the lineup of HVDC-supVol. 13 No. 3 Mar. 2015

ported ICT equipment.
3. HVDC implementation in NTT GroupIn the NTT Group, the HVDC power supply system
has been installed at research and development centers in a trial experiment and also at NTT FACILITIES as a power monitoring system. NTT Communications has introduced our HVDC power supply system for large-scale systems. This system uses eight
500-kW systems (i.e., approximately a 4-MW system
in total) and helps to reduce electricity and installation costs.
However, expansion of the HVDC-supported ICT
equipment lineup and a reduction of the system cost
are necessary in order to further promote HVDC
implementation within the NTT Group. We haveestablished the technical requirements (TR) as thetechnical documentation for procuring HVDC-supported ICT equipment in the NTT Group. We havealso established guidelines (GL) that concern thedevelopment, procurement, design, and constructionof the power supply system.
Through publication of the TR, the NTT Group has
made it possible to support the promotion of HVDCsupported ICT equipment worldwide, boosting thecommercial development of products by ICTFeature Articles

500-kW system: 100 kW × (5 + 1)
Input module Power supply module

Output module

DC PDF

HVDCHVDC power
supported strip
Fuse type fuse
MCCB type
380 VDC
100-kW system: Commercial
15 kW × (7 + 1)
200 VAC

Rectifier

PDF

Plug
ICT rack
ICT equipment(HVDC-supported)
ICT equipment(HVDC-supported)
ICT-equipment(48 VDC, AC, etc.)
ICT equipment(48 VDC, AC, etc.)

Converter

Battery

Cable
protector

Connector Grounding
scheme

MCCB: molded case circuit breaker
PDF: power distribution frameFig. 2. Lineup of power supply components for HVDC.

vendors. The establishment of the GL makes the system manual more useful; for example, the design
guidelines of the power supply system are specified.
The establishment of a standard design and construction will help to reduce costs.
3.1 TR provision items
The TR consists of interface requirements of the
ICT equipment. To ensure consistency with international standards, the TR incorporates the basic
requirements of ITU-T L.1200 such as the operating
conditions of the voltage range and abnormal voltage[4].
The specified range and the main provision items
are respectively shown in Figs. 3 and 4. To start business operations, we incorporated additional provisionitems in TR other than those of international standard
L.1200. To ensure safety and electrical stability, theTR establishes regulations such as the level of stored
energy during an ICT equipment stoppage, maximum
rated capacity, and rated voltage.
In addition, the risks associated with oscillation
conditions and inrush current specified in the 48 VDC
power supply system were evaluated with our HVDC
power supply system and were found to be low.
This TR will enable ICT vendors to easily developand sell HVDC-supported ICT equipment, while the
NTT Group will be able to procure a wide range of
HVDC-supported ICT equipment. In 2014, The NTT
Group issued a press release announcing the fullscale introduction of the HVDC power supply system
in 2016 [5].
3.2 GL provision items
The GL consists of guidelines for the overall power
supply system. The 48 VDC power supply system
guidelines have already been issued. However, they
contain many complex provision items. In contrast,
the HVDC power supply system guidelines havebeen issued as minimum required guidelines in order
to apply it to telecommunication buildings as well as
datacenters. The GL incorporates provisions for
introducing and operating the HVDC system toensure safety and reliability.
The specified range and main provision items of the
GL are shown in Fig. 5. The existing strict regulations
were deregulated while ensuring safety. For example,
different floor power supply designs in the 48 VDC
system, which provides energy from the rectifier
floor to another ICT equipment floor, were prohibited
due to possible risks associated with noise, stray current, and overvoltage from direct lightning strikes.
NTT Technical Review

Feature Articles

This TR interface(L.1200 conformant)

RectifierBasic
configuration

Rack
ICT equipment
MotherPSU
board

380 VDCAC
DC

Battery

Rack

Rectifier380 VDC

AC
DC

PSU

Battery
Other
configurations

This TR isapplicable.

Rectifier380 VDC

AC
DC

PSU

Battery

ICT equipment
Motherboard

12 VDC,
48 VDC, etc.

Rack

48 VDC,
100 VAC,etc.

48 VDC input
equipment
100 VAC input
equipment, etc.

PSU: power supply unit

Fig. 3. Specified range of TR.

Operating voltage rangeof ICT equipment
260–400 VDC

Voltage range
Operating voltage range of ICT
equipment is defined.
Operating conditions forabnormal caseOperating conditions inoperating voltage range anddeviant voltage conditions of
ICT equipment (overvoltage,
instantaneous power failure,etc.) are defined.

(v)

(v)

410

Above
abnormalvoltage

400

Abnormal voltage

Operatingvoltage260

2k

Typical power capacity: under 7.8 kW

500
420
410
400

Rated voltage*
Rated voltage of ICT equipment is defined toproperly compare characteristics. Rated voltage iscompliant with test voltage of L.1200.

Operating condition

260
Abnormalvoltage0Abnormal condition
0

50 µ

10 m

1

FilterRated voltage: 380 VDC(s)Inrush current
To prevent unintended operation of the protective circuit breaker due toinrush current, the passing current and time are defined.
Breakeropens
Inrush current
Rectifier
ICT equipment
AC
FilterConverter
DC
Battery

Rated capacity per power supply system*
To ensure that the top breaker does not open at theminimum operating voltage, the rated capacity per
power supply system of ICT equipment is defined.

Safety*Design conditions such as structure, risk, andreductions in power supply input of ICT equipment
to prevent electric shock are defined.
*Additional provision items other than L.1200
international standard provision items

Converter

Fig. 4. Provision items of TR.

The HVDC power supply system can reduce noiseand stray current risks because the grounding scheme
is different. Therefore, we investigated measures toVol. 13 No. 3 Mar. 2015

reduce the risk of overvoltage from direct lightning
strikes.
In collaboration with NTT FACILITIES, weFeature Articles

Technical Requirements (TR)(Published in June 2014)

Specified range of power supply system guidelines
HVDC power supply equipment
Rectifier380 VDC
AC
DC
2–3

Battery

PSU

PDF

2–1

2–2
3

1

1

Cabling (diameter, lengths, etc.),
different floor power supply design,
grounding2

2–1 Typical voltage and capacity,
input voltage range, EMC
2–2 Current shut down function, EMC
2–3 Power supply configuration,
voltage vibration, EMC

3

Cabling, grounding, EMC

ICT equipment

Converter

HVDC power supply system

Motherboard

Conventional
ICT equipment(48 VDC, AC, etc.)

EMC: electromagnetic compatibility

Fig. 5. Specified range and main provision items of power supply system guidelines.

developed a surge protection device (SPD) and clarified the inhibitory effect of overvoltage and the installation conditions of the SPD. We were able to comeup with different floor power supply designs. We also
evaluated the impact of transient voltage on other ICT
equipment when the circuit breaker or fuse opens
through experimentation and simulation of detailed
models.
The use of fuses and a power distribution frame wedeveloped keeps the transient voltage within the operating voltage range of ITU-T L.1200, which suggeststhat stable operation is possible.

In the future, in addition to strengthening relationships with stakeholders such as ICT vendors, we will
expand HVDC-supported ICT equipment and reduce
the total costs of the power supply system. Hence, wewill accelerate the introduction of the system andcontinue to contribute to energy-saving strategies.
References[1]

4. Future development[2]

The TR and GL have enabled the NTT Group toorganize a full-scale introduction of the HVDC system and to plan a deployment strategy starting in fiscal year 2016; the objective is to have the system
become standard by 2030. The implementation of our
HVDC power supply system will make it possible toreduce electricity rates and installation costs.

[3]



[4]
[5]

T. Babasaki, T. Tanaka, Y. Nozaki, T. Tanaka, T. Aoki, and F. Kurokawa, “Developing of Higher Voltage Direct-current Power-feeding
Prototype System,” Proc. of INTELEC 2009 (31st International Telecommunications Energy Conference), pp. 1–5, Incheon, Korea, October 2009.
ITU-T Recommendation L.1200: Direct current power feeding interface up to 400 V at the input to telecommunication and ICT equipment, 2012.
ITU-T L.1201: Architecture of power feeding systems of up to 400
VDC, 2014.
NTT, “Technical Requirements for Power-supply Interface of Communications Equipment,” October 2008.
http://www.ntt.co.jp/ontime/e/img/pdf/TR176001e.pdf“Publication of World’s first Technical Requirements for the Nextgeneration Power-supply Interface,” NTT press release issued on
August 4, 2014.
http://www.ntt.co.jp/news2014/1408e/140804a.html

NTT Technical Review

Feature Articles

Toru Tanaka

Senior Research Engineer, Energy Management Group, Energy Systems Project, NTT
Energy and Environment Systems Laboratories.
He received his B.E. and M.E. in quantum science and energy engineering from Tohoku University, Miyagi, in 1996 and 1998. He joined
NTT Integrated Information and Energy Systems
Laboratories in 1998. He was engaged inresearch on evaluation of DC power supply system stability and voltage fluctuations. He also
developed HVDC power supply systems fortelecommunication buildings and datacenters.
From 2009 to 2012, he was a manager at NTT
FACILITIES, where he researched power supply
systems and smart community. He is currently
creating documents of ITU-T standard, promoting the use of HVDC systems and researching
future power supply systems at NTT. He received
the 2003 and 2009 Shibusawa Award of The
Japan Electric Association (JEA). He is a member of IEICE.

Jun Kato

Senior Manager, EMC Engineering Group,Technical Assistance and Support Center, Maintenance and Service Operations Department,
Network Business Headquarters, NTT EAST.
He received his B.E. from Shizuoka University
in 1992. He joined NTT Telecommunication
Networks Laboratories in 1992. He has been
engaged in research and development of overvoltage for telecommunication systems. During
1995–1997, he was in the Multimedia Business
Department, where he installed photovoltaics fortelecommunication power systems. During
2004–2006, he was at the Technical Assistanceand Support Center, NTT EAST, as an engineerof telecommunication equipment for telecommunication buildings. He received the 2006 Shibusawa Award of JEA. He is a member of
IEICE.

Mikio Shintaku

Research Engineer, EMC Technology Group,
Energy Systems Project, NTT Energy and Environment Systems Laboratories.
He received his B.E. and M.E. in electrical andelectronic engineering from Kobe University,
Hyogo, in 1993 and 1995. He joined NTT
FACILITIES in 1995 and worked on a lightning
protection project for telecommunication buildings. He is currently researching countermeasures against lightning and grounding methods at
NTT Energy and Environment Systems Laboratories. He received the 2011 Electrical Scienceand Engineering Promotion Award of The Promotion Foundation for Electrical Science andEngineering. He is a member of IEICE.

Akiko Takahashi

Researcher, Energy Supply Systems Development Project, First Promotion Project, NTT
Energy and Environment Systems Laboratories.
She received her B.E. and M.E. in electricalengineering from Tokyo University of Agriculture and Technology in 2008 and 2010. She
joined NTT FACILITIES in 2010 and engaged inmaintenance of power systems for telecommunication facilities. Since 2012 she has been
researching power reduction technologies intelecom equipment rooms at NTT Energy andEnvironment Systems Laboratories.

Koki Asakimori

Researcher, Energy Systems Project, NTT
Energy and Environment Systems Laboratories.
He received his B.E. and M.E. in aerospaceengineering from Tohoku University, Miyagi, in2009 and 2011. He joined NTT Energy and Environment Systems Laboratories in 2011 and has
been studying power conversion systems and
HVDC power feeding systems.

Atsushi Sakurai

Senior Research Engineer, Environmental
Management and Provisioning Project, NTT
Energy and Environment Systems Laboratories.
He received his B.A. in policy management
and M.M.G. from Keio University, Kanagawa, in2001 and 2003. He joined NTT in 2003 andstudied sensor networks. He is currently working
on the promotion and development of ICT systems related to energy and the environment.

Takeshi Iwato

Naoki Hanaoka

Researcher, Energy Management Group,
Energy Systems Project, NTT Energy and Environment Systems Laboratories.
He received his B.S. in physics from Shinshu
University, Nagano, in 2010 and M.S. in divisionof Particle and Astrophysical Science from
Nagoya University, Aichi, in 2012. He joined
NTT Energy and Environment Systems Laboratories in 2012 and studied power conversion
systems and power feeding systems.

Research Engineer, Energy Management
Group, Energy Systems Project, NTT Energy
and Environment Systems Laboratories.
He received his B.E. in electrical engineeringfrom Kinki University, Osaka, in 2003. He joined
NTT FACILITIES in 2003 and engaged in thedesign of power supply systems for telecommunication and photovoltaic systems. Since 2013,
he has been researching HVDC power supply
systems for telecommunication facilities at NTT
Energy and Environment Systems Laboratories.

Vol. 13 No. 3 Mar. 2015



Feature Articles

Hiroaki Matsumori

Energy Systems Project, NTT Energy andEnvironment Systems Laboratories.
He received his B.E. and M.E. in electricalengineering from Tokyo Metropolitan University
in 2011 and 2013, and is currently working on his
Ph.D. at the same university. He joined Energy
and Environment Systems Laboratories in 2013
and studied power feeding systems. He is a member of IEEE.



Nobuhiko Yamashita

Senior Research Engineer, Supervisor, Energy
Supply Technology Group Leader, Energy Systems Project, NTT Energy and Environment
Systems Laboratories.
He received his B.E. in electronics engineeringfrom Kyushu Institute of Technology, Fukuoka,
in 1987. He joined NTT Electrical Communications Laboratories in 1987 and was engaged instudies on high-speed power semiconductor
devices and circuits for DC–DC converters. After
working at ENNET Corporation and NTT
FACILITIES, INC., he joined NTT Energy andEnvironment Systems Laboratories. He is currently developing power supply systems fortelecommunication facilities. He is a member of
the Institute of Electrical and Electronics Engineers (IEEE), the Institute of Electronics, Information and Communication Engineers (IEICE),
and the Institute of Electrical Engineers of Japan(IEEJ). He received the IEICE Academic Encouragement Award in 1995 and the IEICE Communications Society Distinguished Contributions
Award in 2004.

NTT Technical Review

Feature Articles: Reducing the Environmental Burdenof ICT Services

Development of Equipment for
HVDC Power Supply Systems
Hidekazu Hoshi, Hiroya Yajima, Tadatoshi Babasaki,
Keiichi Hirose, Hidenori Matsuo, Masatoshi Noritake,and Takashi Takeda
Abstract

NTT FACILITIES is conducting research and development focusing on the introduction of high-voltage direct current (HVDC) power supply systems to telecommunication buildings, datacenters, and othersuch facilities. Future applications involving the direct integration of renewable DC energy sources suchas solar panels into smart grids are also in view. This article describes our work on the development,
construction, and maintenance of HVDC systems.
Keywords: high-voltage DC power supply system, HVDC rectifier, HVDC PDU

1. Introduction
Servers, data communication equipment, and otherinformation and communication technology (ICT)
equipment are in wide use in society and have been
supporting substantial economic activity in recent
years. ICT equipment is managed centrally in telecommunication buildings and datacenters, and as theuse of such equipment spreads throughout society, its
importance as a social infrastructure increases. The
increasing use is accompanied by an increase inpower consumption, however, and consequently,
reducing that power consumption has become anissue.
Expectations are high worldwide that high-voltage
direct current*1 (HVDC) power supply systems willconserve energy while still providing highly reliable
power supplies. The NTT Environment and Energy
Systems Laboratories and NTT FACILITIES havebeen doing basic research on HVDC as well as developing various types of equipment, which aredescribed in the following sections [1].
2. HVDC rectifiers
The HVDC rectifier converts the commercial AC(alternating current) power supplied by power companies to 380 VDC [2]. There are 100-kW capableand 500-kW capable rectifiers, and the maximum
conversion efficiency is a high 98%. Adopting a
redundant configuration makes it possible to continue
operation in the event that a failure occurs.
3. HVDC PDU
To counter the problem of arcing*2 when high-voltage direct current is interrupted, we developed a special HVDC power distribution unit (PDU) (Fig. 1).
The PDU has an internal mechanical switch that
does not operate when the power plug of an ICT
device is inserted into the socket. After insertion, theswitch is slid to the ‘on’ position, and the internal
contact points are closed, allowing current to flow.
The switch is locked in position so that the plug cannot be removed. To remove the plug, the mechanical*1	 High-voltage direct current: In the ICT field, –48 VDC supply
voltage is used for telecommunications throughout the world. DC
voltages in the range from about 300 V to 400 V, on the other
hand, are referred to as high-voltage direct current.
*2 Arcing: A sustained electrical discharge through the air between
electrodes that occurs due to the electrical potential across theelectrodes

NTT Technical Review

Feature Articles

Fig. 1. HVDC PDU.

19-inch rack
200 VAC

380 VDC

HVDC rectifier(100 kW/500 kW)

380 VDC ICT equipment

380 VDC

HVDC
distribution
panel

380 VDCPower converters for
migration (S/M)

Power converters for
migration (S/M)

Existing AC or –48 VDC
ICT equipment

Existing AC or –48 VDC
ICT equipment

Battery
S: small capacity

M: medium capacity

Fig. 2. HVDC power supply system configuration.

switch is slid to the ‘off’ position, opening the internal contact points. The arcing is interrupted, and thelock is released so that no arcing occurs outside themechanism. That makes the plug insertion andremoval operations safe for operators and maintenance personnel.
4. Power conversion equipment for migration
Introducing an HVDC power supply system
involves procuring ICT equipment that is compatible
with HVDC, as well as HVDC rectifiers and HVDC
distribution panels. However, it is assumed that not
all of the ICT equipment to be introduced will be
HVDC-compatible in the initial transitional migration period. It is therefore necessary to use power
converters that accept 380 VDC from the HVDC rectifiers and output 200 VAC, 100 VAC, and –48 VDC
for the ICT equipment that operates on those voltages
Vol. 13 No. 3 Mar. 2015as provided by the previous power supply systems,
without changing the general framework of the
HVDC power supply system (Fig. 2).
We developed two power converters, a small-capacity type (S) and a medium-capacity type (M), to suitthe equipment being supplied (Fig. 3). The S typewas developed for equipment that consumes poweron the level of several hundreds of watts such as
monitors or other console systems. The M type wasdeveloped for ICT equipment that uses power on thelevel of several kilowatts.
5. Future development
We have described here work on introducing
HVDC power supply systems to telecommunicationbuildings, datacenters, and other such facilities.
Looking to the future, we will expand our field ofview to include the development of HVDC smart
Feature Articles

Power converters for migration (S)Power converters for migration (M)AC output

DC output

AC output

DC output

W: 430 × D: 700
× H: 43 (1U)

W: 430 × D: 700
× H: 43 (1U)

W: 430 × D: 553
× H: 130 (3U)

W: 430 × D: 652
× H: 130 (3U)

External
appearance

Dimensions
(mm)
Input
voltage
Outputvoltage
Outputcapacity
Unit
efficiency

Rating: 380 VDC
100 VAC–48 VDC

100 VAC, 200 VAC

1.0 kW(500 W unit 2 + 1)
90% or higher–48 VDC
7 kW

93% or higher

90% or higher

94% or higher*M type dimensions are for the unit.

Fig. 3. Lineup of power converters for migration.

Utility power

380 VDC

Rectifier(15 kW)

Left: Li-ion bidirectional charger
Right: DC power
converter

AC lineDC lineNetwork

DC-EMS

6600 V/
200 V

Rectifier(15 kW)PV(10 kW)

DC-PCS(10 kW)PV(10 kW)

DC-PCS(10 kW)

Li-ionbi-directionalcharger

EV bidirectionalcharger

BMU
Li-ion(25 kWh)EV

EV & EV bidirectional charger
Li-ion battery

PV panel (10 kW × 2)

BMU: battery management unit
EMS: energy management system

EV: electric vehicle
Li-on: lithium ion

LEDlighting

DCadapter

Notebook
computerDCswitchRefrigerator
DC-PDU

DC power converterDCswitchDC-EMS serverDCadapter

Television

DC PDU380 VDC peripheral
equipment

Blu-ray
playerTV & Blu-ray player
LED lighting Refrigerator
380 VDC home electrical appliance

PCS: power conditioning subsystem
PV: photovoltaic

Fig. 4. Ministry of the Environment Field Testing System (Obihiro, Hokkaido).

grids that operate on renewable energy sources, combining distributed DC power generation by solar
panels and other such sources with storage batteries[3]. We are currently involved in field testing in Obihiro City, Hokkaido and in Yamagata City, Yamagataas part of the Technology Development and Verification to Counter Global Warming Project of the Japanese Ministry of the Environment (Fig. 4), and weplan to actively apply the results from that work.

NTT Technical Review

Feature Articles

References[1]

K. Asakura, T. Tanaka, and T. Babasaki, “Higher-voltage Direct Current Power-feeding System,” NTT Technical Review, Vol. 9, No. 2,
2011.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2011
02fa2.html

Hidekazu Hoshi

Assistant Manager, Technical Division, Energy
Business Headquarters, NTT FACILITIES,INC.
He received the M.E. in engineering from
Utsunomiya University, Tochigi, in 2006 andjoined NTT FACILITIES the same year. He is
engaged in the development of HVDC systems
for central telecom offices and datacenters.

Hiroya Yajima

Engineer, Technical Division, Energy Business
Headquarters, NTT FACILITIES, INC.
He received the B.E. and M.E. in electricalengineering from Utsunomiya University, Tochigi, in 2005 and 2007, respectively. He joined
NTT FACILITIES in 2007 and engaged in thedevelopment of uninterruptible power supplies.
He subsequently joined NTT Energy and Environment Systems Laboratories and is currently
researching a DC power supply system for telecommunications.

Tadatoshi Babasaki

Manager, Technical Division, Energy Business
Headquarters, NTT FACILITIES, INC.
He received the M.S. and Ph.D. in electronicengineering from Nagasaki University in 1990
and 2011, respectively. He joined NTT Applied
Electronics Research Laboratories in 1990. He
has mainly been engaged in R&D of DC power
feeding systems and batteries for telecommunications systems. He is a member of the Instituteof Electrical and Electronics Engineers (IEEE),
the Institute of Electronics, Information andCommunication Engineers (IEICE), and theInstitute of Energy Economics, Japan.

Vol. 13 No. 3 Mar. 2015

[2]

[3]

Y. Udagawa and H. Matsuo, “Power Supply Technology and Air Conditioning Technology for ICT,” NTT Technical Review, Vol. 12, No.
11, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
11fa10.html
K. Hirose, “Trends of DC Power Technologies and their Applications,” IEEJ Transactions on Power and Energy, Vol. 131, No. 4, pp.
358–361, 2011.

Keiichi Hirose

Executive Manager, Technical Division, Energy Business Headquarters, NTT FACILITIES,INC.
He received the B.Eng. and M.Eng. in electrical engineering from Yamagata and Niigata Universities, respectively, in 1990 and 1992, and the
Ph.D. in electrical engineering and computer science from Nagoya University in 2011. He joined
NTT in 1992. He has worked as a research engineer and has more than 18 years of experience inthe design, development, and operation of reliable power systems for telecom offices anddatacenters. He is currently working with 380
VDC systems for NTT and its customers, as well
as researching aspects of smart grids.
He is a member of IEEE, the Institute of Electrical Engineers of Japan (IEEJ), the Institute ofElectrical Installation Engineers of Japan (IEIEJ),
and IEICE. He is also very active in many standards bodies in areas associated with power systems. He is a member of the IEC (International
Electrotechnical Commission) SMB (Strategic
Management Board) Study Group 4, a memberof the Green Grid Power sub-working group,
chair of the IEC SC 22E Japanese NC (National
Committee), and a recent past secretary of the
IEEJ Investigating R&D Committee into DC
power distribution. He was awarded the IEEE
PELS (Power Electronics Society) INTELEC
3rd best paper award in 2009, the outstanding
paper prize from IEEJ in 2010, the best paper
award of IEIEJ in 2013, and the Scientific Awardof the Japan Society of Energy and Resources in
2013. He was also awarded the Hoshino Awardof IEIEJ in 2014.

Feature Articles

Hidenori Matsuo

Research engineer, Research and Development
Headquarters, NTT FACILITIES, INC.
He received the M.E in human and environmental studies from Kyoto University in 2000
and joined NTT FACILITIES the same year. He
worked on the development of HVDC rectifiers
that reduce annual power consumption. He iscurrently studying –48 VDC rectifiers for telecommunication sites. He is a member of IEEJ.

Takashi Takeda

Group Leader of Power Supply System Group,
Research and Development Headquarters, NTT
FACILITIES, INC.
He received the B.E in electronic engineeringfrom Tokyo Denki University in 1996. He joined
NTT FACILITIES in 1996. He has mainly been
engaged in R&D of DC power systems for ICT
applications. He is a member of IEEE, IEEJ, and
IEIEJ.

Masatoshi Noritake

Researcher, Research and Development Headquarters, NTT FACILITIES, INC.
He received the B.E. and M.E. in engineeringfrom Keio University, Tokyo, in 2005 and 2007,
respectively. He joined NTT FACILITIES in2007. He is working on the development of
HVDC systems.

NTT Technical Review

Feature Articles: NTT Tsukuba Forum 2014 Workshop Lectures

Future Optical Access Technologies
for Flexible Service Deployment
Akihiro Otaka
Abstract

The direction of technical development in optical access systems has
mainly been towards achieving stable Internet access at higher speeds.
However, we now recognize that technology for higher speeds alone is notenough to keep up with a changing market. Flexible use of resources is
considered to be a requirement for the next generation of optical access.
This article presents an overview of this problem and other upcoming
challenges and describes examples of technology that NTT Access Network Service Systems Laboratories is working on in order to come up
with solutions. These Feature Articles are based on presentations made at
the Tsukuba Forum 2014 Workshop that was held on October 17, 2014.
Keywords: access system, WDM/TDM-PON, mobile

1. Next-generation optical access challenges
Optical access systems have mainly been used forbroadband Internet access. Fiber-to-the-home(FTTH) services began with the 50-Mbit/s passive
optical network (PON), which was followed by BPON (broadband-PON). The current Gigabit Ethernet(GE)-PON system can provide services at up to 1 Gbit/s.
Statistics provided by the Ministry of Internal Affairs
and Communications show that Internet traffic in
Japan moves at approximately 2.9 Tbit/s over fixedlines (May 2014) and at approximately 620 Gbit/s
over the mobile network (June 2014) [1, 2]. Thesefigures represent an annual rate of increase of 30%
for the fixed network and 50% for the mobile network. We can see that although traffic is steadily
increasing, the increase in the number of optical lines
has begun to taper off. In view of this situation, what
is required of optical access in the future? The respective circumstances for fixed-line and mobile communications are reviewed in this section.
1.1 Fixed lines
From the change in traffic volume per fixed-lineuser over time (Fig. 1) [1, 3, 4] we can see that thetraffic per user is only about 100 kbit/s, which is only
about 10 seconds per day for a 1-Gbit/s line. Even forheavy users in the top 1%, the average speed is only
several megabits per second, which is still far below
the available access speeds. We can also see that theincreasing trend in traffic volume is exceeded by the
progress in technology for higher speeds. We shouldnote here that this discussion concerns the averagevalues, and so does not cover phenomena that occur
rarely. On the scale at which a certain number of users
share bandwidth in a single access system, such as
PON, we cannot necessarily expect a statistical multiplexing effect. For this reason, an important point iswhether or not services can be provided without any
problem when rarely occurring phenomena are taken
into account. An IP (Internet protocol) video service,for example, must be capable of providing the service
even when all subscribers are using the service to the
maximum extent when the total content bandwidthand number of simultaneously available channels for
all users is within the total access bandwidth. In otherwords, that requires the access system to have ahigher capacity than when bandwidth is considered in
NTT Technical Review

Feature Articles(kbit/s)
100,000,000
Standardization

10,000,000

Speed

1,000,000

G-PON
GE-PON

B-PON

100,000

NG-PON2
XG-PON
10GE-PON

10,000Upper 1%

1,000
100

Upper 5%
Average user traffic(downloads)

19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14

10

(Year)

G-PON: Gigabit passive optical network
XG-PON: 10-Gigabit-capable passive optical network
NG-PON2: next-generation passive optical network stage 2

Fig. 1. Trend in average traffic per user for fixed lines.

(kbit/s)
100,000,000

5G
LTE-A

10,000,000
LTE

Speed

1,000,000
3.5G

100,000
10,0003G

Traffic perbase station

1,000
100

Optical line average

20
0
20 0
0
20 1
0
20 2
0
20 3
0
20 4
0
20 5
0
20 6
0
20 7
0
20 8
0
20 9
1
20 0
1
20 1
1
20 2
1
20 3
1
20 4
1
20 5
1
20 6
1
20 7
1
20 8
1
20 9
20

10

(Year)

LTE: Long-Term Evolution

Fig. 2. Trend in average traffic per base station.

terms of average usage levels, which results in wasted
resources. In the Hikari Collaboration Model [5],NTT’s new business model in which a particular formof use or bandwidth is secured for partner providers,
efficient resource allocation will be important to provide economical optical access.
1.2 Optical lines for mobile communication
Mobile communication base stations are connectedto the network by optical lines, and the traffic on
those lines is increasing because of the mutual amplifying effect of an increasing number of users andVol. 13 No. 3 Mar. 2015

increasing communication volume per user. Opticalline speeds are currently higher than wireless speeds,
so the radio link is the bandwidth bottleneck.
The trend in traffic volume per base station,
obtained by dividing the amount of mobile traffic by
the number of base stations, is shown in Fig. 2 [2–4,6]. Just as with fixed lines, there is a sufficient margin
in optical line speed. In contrast, speeds higher thanwireless speeds are required for optical lines. Implementation of wireless speeds in excess of 10 Gbit/s isbeing studied for the future fifth-generation (5G)
mobile communication, and speeds above the 1-Gbit/sFeature Articles

More sectors
Highercapacity

Antenna

Optical
Optical

OpticalSmall cell

Optical2.1 GHz

Optical

1.5 GHz

Macrocell

Extendedfrequency
band

800 MHz

Fig. 3. Example of optical lines used with radio base station.

Core network• Fast and reliable packet
network

Backhaul
BBU
Base station

BBU
Base station

Fronthaul
RRH

Fronthaul
RRH
RRH

Remote radio head

RRH

• C-RAN facilitates RRH
coordination by implementing
baseband processing
at the base station.
• Transmission of digitizedradio signal

Remote radio head

BBU: baseband unit
RRH: remote radio headFig. 4. Example mobile network configuration.

rate that is currently provided by optical lines will be
required.
The direction of mobile communication technology
as it progresses will be toward meeting the requirements for greater use of optical access as well as
achieving higher optical line speeds. Increases inmobile capacity will come from the use of smaller
cells, higher cell density, expansion of the radio frequency band, and other such factors, in addition tohigher wireless transmission speeds. That will require
more optical lines (Fig. 3).
There are also issues that are specific to mobile
communication. Mobile networks are divided into thebackhaul, which connects base stations to the core
network, and the fronthaul, which connects base stations to remote radio heads (RRHs) (Fig. 4). The
backhaul network is a high speed, highly reliable
packet network whose speed depends on the traffic
volume. The fronthaul network, on the other hand,

uses a C-RAN (centralized radio access network)
configuration, which facilitates coordination processing for multiple RRH towers that have overlapping
signal areas. In that configuration, baseband processing and other processing is done at the base station,and only the high-frequency processing is done at the
RRH tower, so the fronthaul part uses a CPRI (Common Public Radio Interface) signal, which is a digitized radio waveform. CPRI uses a fixed rate whether
or not users are communicating, and requires a speedof about 16 times that of wireless transmission. With
150-Mbit/s LTE (Long-Term Evolution), for example, an optical transmission speed of 2.4 Gbit/s isrequired. If adopted in the present form for 5G mobile
communication, the system would require an opticalexcess capacity of 160 Gbit/s per RRH tower, which
is impractical.
Thus, the challenges for future high-speed mobile
communication mainly concern the fronthaul system,
NTT Technical Review

Feature Articles

TDM-PON extends the total WDM bandwidth: 40-Gigabit-capable PON
P2P system WDM is possible.

2.5–10 Gbit/s
ONU

OSU
OSU

ONU

PON

ONU

WDM
(4–8 wavelengths)

OSU
OSU
P2P OSUONU

λ1

P2P ONUP2P ONU
Wavelength

λ4
Wavelength
occupied
Wavelength
occupiedTime

P2P OSUWDM/TDM-PON

P2P WDM overlay

Fig. 5. NG-PON2 features.

specifically, the commitment of resources whether or
not users are using the system, and the very large
required bandwidth.
2. Implementing the next-generation opticalaccessWe believe that the past trend of simply increasing
speed is limited as a solution to the problems outlined
above. We present here technology that NTT AccessNetwork Service Systems Laboratories is working onthat represents a different approach.
2.1 WDM/TDM-PON
WDM/TDM-PON uses wavelength division multiplexing (WDM) to superimpose multiple time division multiplexing (TDM) PON on a single fiber(Fig. 5). Currently, the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is moving forward with standardizationof 10-Gbit/s PON as the NG-PON2 (next-generationpassive optical network stage 2) [7]. This is a 40Gbit/s PON that multiplexes four typical 10-Gbit/s
PON systems. This format also allows WDM forpoint-to-point (P2P) systems, which will be advantageous for mobile communication applications.
Although multiplexing four 10-Gbit/s PON systems on a single fiber quadruples the bandwidth, this
WDM/TDM-PON is not simply a 40-Gigabit-capable
PON system. The WDM technique has been used toVol. 13 No. 3 Mar. 2015

achieve target communication speeds that are relatively low in the early stage of standardization, forwhich further speed improvements have been difficult. However, that was a transitional technology, andtechnical advances mean that it has since been
replaced with high-speed serial communication.
In WDM/TDM-PON, WDM is not simply a technique for achieving higher speeds. The multiplexingof four 10-Gbit/s signals differs from a 40-Gbit/s
serial signal in that the multiplexing provides flexibility in the use of wavelengths. The advantages ofwavelength flexibility are described below.
The wavelength flexibility in a WDM/TDM-PON
system is implemented by the ability to dynamically
set the wavelength that is used by the optical network
unit (ONU) for communication. That eliminates theneed to provide an ONU for each wavelength, asshown in Fig. 5, which is an advantage in respect to
the ONU management. The dynamic setting of the
ONU wavelength also enables flexible bandwidth
allocation and increases reliability. The improvement
in reliability comes from being able to continue communication with a different optical subscriber unit
(OSU) when an OSU fails during communication byswitching the ONU wavelength [8].
When traffic volume is low, energy can be conserved by connecting all of the ONUs to a single OSU
and placing all of the other OSUs into sleep mode
(Fig. 6). Conversely, if it is known in advance that
traffic will be low, service can be started on a single
Feature Articles

When communication traffic is light, all ONUs can be connected toa single OSU and the other OSUs placed in sleep mode.
Fast wavelength switching is required so as to not affect communication.
λ1u
ONU 1
ONU 2
ONU 3

Switch towavelength1(λ1u)ONU 3

OSU #2

λ3u

λ1u

ONU 2

OSU #1

λ2u

ONU 4

ONU 1

OLT

λ2u

Energyconservation Addition

λ1u
λ1u
λ1u

ONU 4

OSU #3OLT
OSU #1
OSU #2

Power off

OSU #3Fig. 6. Wavelength switching for energy efficiency and flexible bandwidth allocation.

OSU with more OSUs added successively as neededto accommodate increasing traffic. It is also possible
to dynamically change connections between ONUs
and OSUs, making it possible to switch to the appropriate OSU at any time in consideration of the user
ONU resources needed to ensure bandwidth. The
WDM technique can thus be used to avoid the current
problem of configuring facilities for maximum
capacity regardless of the amount of traffic.
In addition to moving forward with R&D on WDM/
TDM-PON based on that approach, NTT Access Network Service Systems Laboratories is also using
these results to contribute to standardization of NGPON2 in ITU-T.

processing for coordination of the RRHs is performedat the base station in the current fronthaul configuration, and only the high-frequency processing is performed at the RRH. NTT Access Network Service
Systems Laboratories has shown that a new interface
definition that reduces fronthaul bandwidth is madepossible by revising that functional distribution andassigning appropriate functions to the RRHs toimplement inter-RRH coordination (Fig. 7) [10].
We believe these technologies can be applied tocreate a mechanism in which bandwidth is allocatedflexibly according to traffic level and only duringcommunication to replace the conventional wastefulreserving of fixed optical access bandwidth.

2.2 C ompression technology and interface redefinition technology
For the mobile network, we are mainly working on
developing technology to reduce fronthaul speeds.
Here, we describe compression technology and interface redefinition technology for that purpose.
As mentioned earlier, the fronthaul system currently transmits radio waveform information, so optical transmission at a fixed speed is required, regardless of user traffic volume. NTT Access Network
Service Systems Laboratories has developed compression technology for greatly reducing the radio
waveform sample data by exchanging information on
the user communication situation between the radio
base station and the optical access system [9]. Also,

3. Future development

The next generation of optical access systems isfacing problems that the conventional approach ofsimply increasing speed cannot solve. Various
research programs are underway based on theapproach of allocating the required resources whenrequired, such as that described here. In the future, itwill probably be possible to shift bandwidth flexibly
from the home to the business district during businesshours and from the mobile network to the home during evening meal times. We are working on achieving
such an efficient communication society.

NTT Technical Review

Feature Articles

CPRI

Modulation

RF

Coordination
function
Modulation

RF

New
Coordination
functioninterface

Base station

Modulation

RF

Modulation

RF

Remote radio head

RF: radio frequency

Fig. 7. Redefinition of the mobile fronthaul interface.

References
[1]

[2]

[3]

[4]
[5]
[6]

[7]
[8]

[9]

Ministry of Internal Affairs and Communications, “Aggregation andPreliminary Calculation of Internet Traffic in Japan” October 7, 2014
(in Japanese).
http://www.soumu.go.jp/main_content/000316564.pdf
Ministry of Internal Affairs and Communications, Information &Communications Statistic Database, Data by field/Communications/Traffic (in Japanese).
http://www.soumu.go.jp/johotsusintokei/field/tsuushin06.html
Ministry of Internal Affairs and Communications, Information &Communications Statistic Database, Data by field/Communications/Internet (in Japanese).
http://www.soumu.go.jp/johotsusintokei/field/tsuushin01.html
K. Cho, “Broadband Traffic Report,” Internet Infrastructure Review,Vol. 20, pp. 32–37, 2013.
“Hikari Collaboration Model,” NTT press release published on May
13, 2014.
http://www.ntt.co.jp/news2014/1405eznv/ndyb140513d_01.html
Ministry of Internal Affairs and Communications, Information &Communications Statistic Database, Data by field/Radio and wireless/Number of radio base station by use (in Japanese).
http://www.soumu.go.jp/johotsusintokei/field/denpa02.html
ITU-T Recommendation G.989.1: 40-Gigabit-capable passive optical
networks (NG-PON2): General requirements, 2013.
S. Kaneko, T. Yoshida, S. Kimura, N. Yoshimoto, and H. Kimura,“Agile OLT-protection Method Based on Backup Wavelength andDiscovery Process for Resilient WDM/TDM-PON,” Proc. of ECOC
(European Conference on Optical Communication) 2014, Tu.1.2.4.
Cannes, France, September 2014.
N. Shibata, S. Kuwano, J. Terada, and N. Yoshimoto, “Dynamic Compression Method Using Wireless Resource Allocation for Digitized

Vol. 13 No. 3 Mar. 2015

Radio over TDM-PON System,” Proc. of OFC (Optical Fiber Communication Conference and Exposition) 2014, Tu3 F.4, Los Angeles,
USA, March 2014.
[10] K. Miyamoto, S. Kuwano, J. Terada, and H. Kimura, “A Study on
Optical Transmission Bandwidth for Future Mobile Fronthaul Basedon PON System,” IEICE Tech. Rep., Vol. 114, No. 119, CS2014–18,
pp. 7–12, July 2014.

Author profile
Career highlights
Executive Manager, NTT Access Network Service Systems Laboratories.
Akihiro Otaka received the B.S. and M.S. inphysics from the University of Tokyo in 1989 and1991, respectively. He joined NTT in 1991 andengaged in developing optical lithography technologies for LSI fabrication. In 1998, he began
working on the development and standardizationof optical access systems such as Gigabit and 10
Gigabit EPON. From 2010 to 2014, he was withNTT EAST R&D Center, where he worked on
optical access, wireless access, and wirelesshome networks. He joined NTT Access Network
Service Systems Laboratories in 2014.

Feature Articles: NTT Tsukuba Forum 2014 Workshop Lectures

R&D Trends in Optical Fiber andCable Technology
Kazuyuki Shiraki
Abstract

At NTT Access Network Service Systems Laboratories, we are engaged
in research and development (R&D) of optical fiber and cable technologies that contribute to drastically reducing network costs. This article
introduces the latest R&D in maintenance and operation technologies for
effective maintenance and management of a massive number of opticalfacilities. It also reviews next-generation optical fiber technologies tohandle the explosive future growth of data traffic.
Keywords: optical fiber and cable, maintenance and operation technology, next-generation optical fiber technology

1. Introduction
NTT has been involved in the development of optical fiber technology for over 40 years. A commercial
optical fiber service was started in Japan in a trunkline network in 1982, and the Japan longitudinal optical fiber network was completed in 1985. Since then,
the transmission capacity has expanded year by year
to meet the growing demand and to implement technical advances. In access networks, the full-scale
fiber-to-the-home (FTTH) service called B FLET’S
began in 2001. NTT laboratories have developed
various optical components and systems to implement these commercial optical fiber services. In the
recent decade, in particular, we have focused on
improving fiber and cable technologies for opticalaccess networks to further promote the FTTH service. A recent typical research and development(R&D) achievement is a bending-loss insensitive
fiber we developed using holey fiber technology. A
hole-assisted fiber, which is one type of holey fiber,
has much higher resistance to optical bending loss
compared to the conventional optical fiber and has
been applied commercially as bending-free opticalfiber cord, gap wiring indoor cable, and jumper cablefor office buildings. These optical cords and cables

may prevent an increase in accidental bending loss incustomer homes and office buildings, where there aremany opportunities to handle such cords and cables
directly. In addition, these optical cords and cables
make it possible to deliver optical cable into customer
homes, where it was once difficult to wire conventional cable.
2. Future direction of R&D of optical fiberand cable technology
2.1 Target of optical fiber and cable technology
The transition in the number of FTTH subscribers
can be divided into three phases (Fig. 1): an earlystage, expansion phase, and mature phase. In theearly stage, quick, mass installation was very important. In the expansion phase, it became important toconstruct optical facilities economically in order toexpand service areas, especially where it was difficult
to deliver service such as in rural areas. In the maturephase, however, it is becoming increasingly important to efficiently maintain and manage the huge
number of existing optical facilities. In fact, our R&D
focus has been shifting from how to reduce the construction cost, i.e., CAPEX (capital expenditure), to
how to maintain and operate optical facilities
NTT Technical Review

Feature Articles

CAPEX
reduction
Number of FTTH
subscribers

OPEX
reduction
All opticalaccessComponent cost

Construction cost

Operation cost

We are here!
Mature phase

20 M
Expansionphase• Quick, mass installation• DIY technologies for
optical network construction• Fundamental cost reduction in
operation and maintenance• Mobile fronthaul• Migration technology• Skill-free work support• Operation and maintenance for numerous facilities• Various lineups for installation on customer premises• Efficient construction for rural areas

Early stage

2010

2014

Year

DIY: do it yourself

Fig. 1. Target for optical fiber technology.

effectively, i.e., OPEX (operating expenditure), as
shown in the figure.
2.2 T wo main objectives of R&D of optical fiberand cable technology
In view of the transition in the R&D target, we areconducting our R&D activities by focusing on two
main objectives. First is the creation of new technologies for the operation and maintenance of optical
network facilities as a short- to medium-term objective. To reduce the maintenance and operation cost of
optical access networks, it is important to create newtechnologies by converging optical fiber technology
and the latest information technology.
Second is the innovation of next-generation opticalfiber as a medium- and long-term objective. It is
expected that the conventional fiber will not be able
to handle the explosive growth in traffic in the future.
The limited transmission capacity of optical fiber is acontinuous challenge that we also intend to tackle.
2.3 D irection of R&D of optical fiber and cabletechnology
The direction of R&D of optical fiber and cable isconsidered to have three axes: workability, operability/maintainability, and capacity/functionality. We
are proceeding with our R&D activities having set thefollowing four technology goals on these three axes.
(1) Easy and effective construction- Cable design technology- Optical connection technology
Vol. 13 No. 3 Mar. 2015

(2) Effective maintenance and operation- Optical local injection/detection- Fiber switching technology(3) Precise and quick remote fault location- High resolution and long distance measurement-	Measurement technique for PON (passive optical network) architecture(4) Ultrahigh capacity fiber- New structure fiber (holey fiber)- Multi-core and few-mode fiber
3. Recent R&D topics involving
optical fiber and cable
We introduce here some of the R&D themes wehave focused on recently.
3.1 Optical line switching technology
First, we introduce optical access line switching
technology, which can minimize service interruption
caused by fiber route changes. We have been studying
this technology by focusing on two approaches. One
is interruption-free switching, and the other ismomentarily interrupted switching (Fig. 2).
In interruption-free switching, route switching isachieved without an interruption in service by preparing a bypass line, which is used temporarily to duplicate in-service lines. Finally, service is switched to a
newly constructed line. The key technologies for thisare delay difference measurement to precisely measure the signal delay between two different linesFeature Articles

Interruption-free switching

Newly constructed line
Customer
2×2 coupler Current
ONU
line
Bypass line
Prototype system

IDM
OLT
2×2
coupler

Fundamental technology

Delay difference Delaymeasurement adjustment

Newly constructed line
Customer
SplitterCurrent line

IDM

Bypass line

ONU

Momentarily interrupted switching

Repeater

Local light injection anddetection technique
Index matching gel Fiber probe

OLT
2×2 coupler

Prototype device

Lens
Bent
part

Current line

Type A

Type B

IDM: integrated distribution module
OLT: optical line terminal
ONU: optical network unit

Fig. 2. Optical line switching technology.

(between the current line and the bypass line, andbetween the bypass line and the newly constructedline) and delay adjustment to control and adjust thesignal delay. By improving this technology, we havebeen able to reduce the volume of equipment by 40
times (14 L) and to reduce the adjustment time by1000 times (less than 3 seconds for a 1-km adjustment) compared to the original time. This improvement has enabled us to advance this switching technology to the practical use level.
Route switching in momentarily interrupted opticalline switching technology is carried out by using a
local light injection and detection technique in orderto formulate a bypass line. In this scheme, bending is
temporarily applied to the currently used line toswitch an optical signal from the current line to a
bypass line or from a bypass line to the newly constructed line. A very short service interruption occurs
during switching, but this scheme is advantageous inthat it can achieve switching with a very simple system configuration compared to interruption-freeswitching.
The local injection and detection technique is the
key technology to realize this system. It enables
input-output of signal light through the fiber coating
without cutting the fiber. To detect very weak lightsignals leaking from the fiber and to input light signals into the fiber efficiently, it is necessary to adjusta fiber probe with a high degree of accuracy. We havedeveloped a highly efficient local injection/detection
system by designing an appropriate probe position to
maximize the coupling efficiency and by devising an
optical coupling scheme.
These two line-switching systems can be selectedaccording to the work situation in the field. We
believe that this new technology will make it possible
to complete line-switching tasks more effectively andwithout service interruptions. We are now conducting
a field trial by using prototype systems to identify
practical problems, including those involving operation and procedures for line-switching work. We plan
to further improve this technology taking the resultsof the field trial into account in order to establish it asa total solution for line-switching work.
3.2 Coated fiber connection technique
Next, we introduce our coated fiber connection
technique, which makes it possible to cut and connect
optical fiber without removing the fiber coating. The
use of this technique eliminates the need to remove
the fiber coating and to clean the fiber, and thus, thetools for this work (stripper, alcohol, paper, etc.)
become unnecessary. Moreover, this connection technique reduces the risk of fiber breakage because it
does not require field workers to handle bare fiber
directly.
NTT Technical Review

Feature Articles• High accuracy 3D map (point cloud DB) is made by spatially measuring facilities
using GPS antenna, camera, and laser scanner.
1) MMS: new spatial measurement technology certified as public survey method;
MMS uses a GPS antenna, inertial measurement unit, camera, and laser
scanner to take highly accurate measurements at speeds of 20–80 km/h.
2) Poles and cables are automatically extracted from 3D point cloud data.
3) Extracted poles and cables are drawn on map using GPS data.

MMS (mobile mapping system)

High accuracy 3D map (point cloud DB)

Fig. 3. 3D facility management technology.

This novel new connection approach incorporates
two important key technologies. The first involves
cleaving a coated optical fiber, and the second consists of removing the fiber coating in a connecting
component. For the cleaving method, we found that astretching method was suitable for cleaving the coated fiber over a wide temperature range. We also
clarified that for the removal technique, improving
the shape of the part of the connecting component thecoating was removed from made it possible to remove
the fiber coating more effectively over a wide temperature range. We will continue to improve thistechnique in order to reduce the cost of the cleaver
device and increase the percentage of successful outcomes in almost every work environment.
3.3 3D facility management technology
We are working to reduce the total cost of outsidefacility management and make outside work more
efficient by establishing outside facility databases(DBs) and business applications based on threedimensional (3D) computer-aided design (CAD)
technology. This technology is aimed at making
design and maintenance work for outside facilities
simpler and more effective by constructing a 3D
CAD-based outside facility DB and business applications, instead of using the conventional 2D plant
records (Fig. 3). This new technology is characterized by the use of a mobile mapping system (MMS)
to build a highly accurate 3D map. MMS is a new
spatial measurement technology certified as a public
survey method; it is equipped with a GPS (Global
Vol. 13 No. 3 Mar. 2015

Positioning System) antenna, an inertial measurement unit, a camera, and a laser scanner. It performs
highly accurate measurements at speeds from 20 to
80 km/h. We are developing a 3D point cloud DBwith MMS that can automatically extract outsidefacilities such as poles and cables from 3D point
cloud data and identify extracted facilities by accessing an existing facility DB system.
One application example is automatic detection ofpole deflection and the height of cables from the 3D
point cloud DB. This enables us to select particularfacilities that preferentially need to be inspected froma massive number of network facilities. Moreover, byanalyzing changes in the 3D point cloud DB over theyears, the system can be used to automatically indicate unsafe facilities on a map. This novel facility
management system is expected to contribute to making inspection work of various facilities more efficient because it eliminates the need to dispatch workers to the field to inspect each piece of facility equipment.
3.4 R emote fault location measurement for PON
architecture
PON technology has been widely adopted to deliver FTTH services to save the cost of cables and optical transceivers. One of the critical issues with PON
configuration is how to monitor the faults in tributaries of the optical splitter, because conventional optical time-domain reflectometry cannot obtain accurate
loss distributions beyond the optical splitter. We havedevised a novel remote measurement technique thatFeature Articles

enables us to obtain the loss distribution of eachbranched fiber below the optical splitter using aphysical phenomenon called Brillouin scattering.
In this new measurement method, two opticalpulses—a pump pulse and a probe pulse—are
launched into an optical fiber with a time delay froman apparatus in the central office. The two launchedpulses go into branched fibers through an optical
splitter and are reflected at an optical termination
filter installed in front of an optical network unit
(ONU). Because the two pulses are injected with atime delay, the probe pulse, which is launched prior
to the pump pulse, reaches the reflection point at theend of the branched fiber first, and it collides with thepump pulse, which is launched with a time delay, inthe tributary fiber. The optical frequencies of the twopulses are set to have a difference between them that
corresponds to a Brillouin frequency shift. When thetwo pulses collide, Brillouin scattering occurs in thefiber, which is when part of the energy is transferredfrom the pump pulse to the probe pulse. We canobtain the loss distribution of each tributary in orderto analyze the returned probe pulses at the apparatus,
while controlling the timing of the pulse launches.
We confirmed that we were able to identify the faulty
fiber and the accurate fault location in a PON configuration with an 8-branched splitter by using thismethod. This new method is therefore effective for
identifying fault locations in fiber branches where
failures tend to occur without having to dispatch
workers to the field. If this approach can be implemented practically, it will help to overcome one of the
major difficulties with PONs and will also reduce
maintenance costs.
3.5 N ext-generation ultrahigh speed and capacity
fiber technology
The bandwidth of optical fiber communication systems that form the backbone for this communication
is being increased yearly. So far, transmission capacity per optical fiber has increased by using time division multiplexing (TDM) and wavelength divisionmultiplexing (WDM) and by increasing the multiplexing density and signal density based on various
breakthroughs. However, as the density of signal
multiplexing increases, the power density per crosssection of fiber inevitably increases. High power density in optical fiber is known to cause nonlinear optical effects, which degrade signal characteristics, andfiber fuse, which destroys optical fiber thermally.
When the power density threshold and the bandwidthof the optical amplifier are taken into consideration,

it is said that the maximum transmission capacity of
conventional single-mode fiber (SMF) is limited toaround 100 Tbit/s. Space division multiplexing(SDM) is thought to be a potential candidate as thenext multiplexing axis to break through the capacity
limitation. Thus, new optical transmission technology
is expected to meet the growing demand for transmission capacity. In terms of the transmission medium,two design concepts have been proposed for realizing
SDM. One is multi-core fiber (MCF), which has multiple individual cores in a fiber, and the other is fewmode fiber (FMF), in which multiple different transmission modes can be transmitted within a single
core. We are conducting research on the transmission
medium for SDM technology in order to extend thetransmission capacity to meet the future explosive
increase in data traffic.
The MCF transmission system is illustrated inFig. 4. The transmission system with MCF consistsof some fundamental technologies as well as thosefor fiber design and manufacturing. These include
optical amplification technology, which amplifies
multiple optical signals simultaneously; connection
technology, which connects multiple cores at one
time; and fan-out technology, which divides MCF
into multiple SMFs. We are now conducting researchon MCF in a national project launched by Japan’s
National Institute of Information and Communications Technology (NICT), which has established anindustry-academia research group. One of theachievements in this project is that we conducted thefirst trial of a multi-vendor interoperability experiment with MCF technology in 2013. We constructed
a 100-km-long transmission line consisting of MCF
with seven cores provided from five different fiber
vendors, and other optical components such as amplifiers, connectors, and fan-out cords. We confirmed in
the transmission experiment that transmission signals
in the seven individual cores were successfully transmitted simultaneously without noticeable interference. We believe that this interoperability experimentis highly significant from a practical application perspective.
Fundamental technologies for mode division multiplexing transmission are shown in Fig. 5. Mode division multiplexing is a transmission scheme in which
multiple optical modes individually modulated withsignals are transmitted in a single-core optical fiber.
The key technology with the multi-mode fiber used
for SDM is the effective control of individual opticalmodes, in contrast to conventional multi-mode fiber.
Mode division multiplexing systems are also based
NTT Technical Review

Feature Articles

SCF to MCF
125 µm–250 µm
Cores: 1

Cores: 2–a few dozen
RX (reception)

TX (transmission)
MCF

MCF

Optical amplification
Input

MCF

Connection

Fan-out

OutputSMF

MCF

Amplify multiple optical signals
simultaneously.

Connect multiple coresat one time.

Divide MCF into multiple SMFs.

Various fundamental technologies should be established to achieve the MCF transmission system.

Fig. 4. Fundamental technologies for MCF transmission.

SMF to FMF
+

+

TX

RX

+

Mode multiplexer/demultiplexer

Multi-mode amplification

Signal processing
Received signal

Processed signal

+
SMF

FMF

MIMO Processing

Amplify higher modes as well
as fundamental mode.

Restore signals disturbed intransmission line and/or atconnection points.

MIMO: multiple-input, multiple-output

Fig. 5. Fundamental technologies for mode division multiplexing transmission.

Vol. 13 No. 3 Mar. 2015



Feature Articles

on various fundamental technologies as well as fiber
design and manufacturing technology, for example,
mode multiplexer/demultiplexer technology, in which
individual modes are multiplexed and demultiplexed;
multi-mode amplification technology, in whichhigher modes as well as fundamental modes areamplified; and signal processing technology, which
restores signals disturbed in the transmission line
and/or at connection points. We successfully carriedout the first ever mode division multiplexing transmission experiment, in which two modes that weremodulated individually were transmitted in one fiber;
this achievement was reported at the Optical Fiber
Communication (OFC) Conference in 2011.
We have also reported world-leading data in thefield of mode division multiplexing transmission
technology such as multi-mode fiber with a trenchassisted graded index core in which six LP (linearlypolarized) modes (ten modes if degenerate modes areincluded) can be transmitted with low differential
mode dispersion and in a wide wavelength region,
and a planar lightwave circuit (PLC) type mode multiplexer/demultiplexer, which can multiplex anddemultiplex four individual modes in one PLC chip.



In terms of SDM technology, we will continuously
strive to tackle the limitation in the transmission
capacity of optical fiber and also to make progress inthe practical use of SDM technology.

Author profile
Career highlights
Executive Research Engineer, Executive Manager, Supervisor, Access Media Project, NTT
Access Network Service Systems Laboratories.
He received the B.E. and M.E. in physics andthe Ph.D. in electrical engineering from Kyushu
University in 1988, 1990, and 2000, respectively.
He joined NTT Transmission Systems Laboratories in 1990 and studied low-loss optical fiber andnonlinear optical effects in optical fiber. He hasover 20 years of experience in optical fiber andcable research, development, and standardization. He has served as a rapporteur of ITU-T
SG15 Question 8. He is a member of IEICE(Institute of Electronics, Information and Communication Engineers) of Japan.

NTT Technical Review

Feature Articles: NTT Tsukuba Forum 2014 Workshop Lectures

NTT R&D Activities toward Future
Access Network Operation
Jun Nishikido
Abstract

The Access Network Operation Project of NTT Access Network Service Systems Laboratories is a research and development (R&D) undertaking targeting a future operation system in the access network. This
article provides an overview of access network operation in a future network slated for implementation around 2020 and describes related R&D
activities. It also introduces various R&D efforts focused on the use ofnavigation technology for streamlining the execution of business operations without affecting the existing operation system.
Keywords: future operations, future networks, navigation technology

1. Introduction
On May 13, 2014, NTT President and CEO Hiroo
Unoura announced in a press conference that NTT
EAST and NTT WEST would begin wholesaling
fiber access services. By providing these services in afair manner to a wide variety of market players indiverse industries, NTT is advancing a Hikari Collaboration Model [1] that signals a radical shift fromits existing B2C (business-to-consumer) business to
B2B2C (business-to-business-to-consumer) business. In this model, players such as telecommunication carriers, mobile virtual network operators(MVNOs), and Internet service providers (ISPs) provide services linking fixed and mobile communications. For example, the Hikari Collaboration Model
could be applied to a total health support service inwhich medical institutions provide remote diagnosis
and health consultations, electronics manufacturers
provide devices for health monitoring, and fitness
clubs suggest exercise plans for their members. In
this way, market players in a wide range of industries
collaborate to provide one-stop services supporting ahealthy lifestyle.
The target access network operation scenario needed in order to achieve this B2B2C model based on thewholesaling of fiber access services is shown in
Fig. 1. In this scenario, NTT will be an operations
provider for service providers, who are represented
by the second “B” in the B2B2C model. NTT will
provide, in particular, one-stop operation and maintenance of network, cloud, and application services.
This one-stop operation can contribute to the creationof new and attractive services in a wide variety ofindustries. Furthermore, end users in this scenario
will be able to select from a variety of innovative
services provided by diverse market players. At thesame time, the operations provider (NTT), represented by the first “B” in the B2B2C model, must be
capable of supporting diverse service levels andresponding quickly to a huge number of service
applications, so substantial labor savings will beneeded to provide operations in this model.
NTT Access Network Service Systems Laboratories is currently examining five future directions ofaccess network operation (Table 1). Of these, we will
first introduce R&D activities surrounding Operations as a Service (OaaS) and Service Orchestration,
which are strongly related to one-stop operation. We
will then introduce Simple & Smart Operation (navigation technology) for reducing the operator’s workload as a direction to be taken in parallel withNTT Technical Review

Feature Articles

End users• One-stop operation(service operation/
maintenance)• Automated optimizationof operation environment
Service providers

One-stop operation
Collaboration
and automatedoptimization

Fixed network

MobilenetworkCloud• Create value throughtechnology collaboration• Achieve drastic laborsavings

Operations provider (NTT)
Applications
Voice Pictures
Video

...

Fig. 1. Scenario targeted by access network operation.

Table 1. Future directions of access network operation.
OaaS

Provide operation functions as a service

Service Orchestration

Achieve service operations with nophysical limitations through virtualization
technology

Proactive Operation

Achieve a proactive form of operation byclarifying latent mechanisms driving
changes in the network

Simple & Smart Operation

Save on labor by reducing number ofoperations and simplifying tasks

Sustainable Operation

Achieve management technology thatenables secure and sustainable
expansion that is robust to changes inthe business and service environment

one-stop operation.
2. OaaSThe OaaS mechanism provides a portion of theoperation functions for achieving efficient operationof network facilities to service providers as a service(Fig. 2). It enables over-the-top (OTT) and othertypes of service providers to use customer management functions that they formerly had to prepare
themselves such as order processing, quality of service (QoS) and service level agreement (SLA) management, and billing management. The service providers can access these functions via an OaaS appliVol. 13 No. 3 Mar. 2015

cation programming interface (API) prepared on the
NTT Group side. The OaaS mechanism also provides
for automated collaboration in which service providers use the API to access a variety of operation functions that they formerly had to link to manually. This
capability can dramatically shorten the time-to-market of a service. NTT aims to use this OaaS mechanism to provide an attractive network that service
providers will continue to choose.
A beneficial effect of OaaS on the service-provider
side is that an operation system can be used simultaneously with the network services (fixed and mobile)provided by the NTT Group, which means that information and functions on the NTT side and theFeature Articles

Operation functions** From enhanced Telecom Operation Map (eTOM) of TeleManagement Forum (TMF)
Service order

Maintenance

Charging

Customer
relationsmanagement

Order
processing

Customer
QoS/SLAmanagement

Billingmanagement

Servicemanagement

Serviceactivation

Servicequality
management

Serviceguidance

Facility
management

Resource
provisioning

Resource
performance
management

Resource
usage report

OaaS API
Service providers (OTT etc.)• Telecommunications carrier• MVNO, ISP• Companies in other industries

Network facilities

Fig. 2. OaaS mechanism.

service-provider side can be linked. It should therefore be possible to provide new services that merge
communications with applications from diverse
industries while making the best use of the key attributes of the service provider. As for end users, theprovision of innovative services by a variety of service providers, each leveraging its core competence,
should contribute to improved quality of life (QoL).
The main challenges and recent activities surrounding OaaS are listed in Table 2.
3. Service Orchestration
The Service Orchestration mechanism uses virtualization techniques to automate and streamline theprocess of making network settings that are needed
for service provision but that straddle multiple layers(Fig. 3). In the network of the future, the clouddomain and the network domain must be seamlessly
connected. The role of Service Orchestration will be
to interlink legacy network equipment, network
equipment that can be controlled by the new software-defined networking (SDN)*1 technology, andnetwork functions that have been virtualized by the
network functions virtualization (NFV)*2 technology
provided on the cloud.
NTT is establishing three main goals for Service
Orchestration: (1) end-to-end network service management to provide integrated control from the application layer to the physical layer; (2) separation of

network services and equipment by applying virtualization techniques (SDN, NFV) to the network; and(3) advanced and automated operations through lumpconfiguration of multiple network equipment andautomatic recovery after failures. Service Orchestration should also reduce operating expenses while
enhancing network value. We can expect Service
Orchestration to achieve the former effect by simplifying remote tasks and consolidating on-site tasks
and by identifying the causes and effects of failuresassociated with layer integration, and to achieve thelatter effect by providing fast and efficient operations
tailored to the request levels of diverse market players.
The main challenges and recent activities surrounding Service Orchestration are listed in Table 3.
4. Simple & Smart Operation
Simple & Smart Operation is introduced here as adirection to be pursued in parallel with the above
R&D activities surrounding one-stop operation.
Simple & Smart Operation focuses on the workflow*1	 SDN: A network that can dynamically set and modify the network configuration, functions, performance, etc., through software operations, or the concept of such a network*2 NFV: A system for implementing the functions of a network-controlling communications device by using software and executingthat software on an operating system (OS) that runs virtualized
general-purpose servers

NTT Technical Review

Feature Articles

Table 2. OaaS: Challenges and recent activities.
Challenges

Recent activities

Clarify operations/collaboration functions
and associatedinformation• Establishing basic business patterns in the B2B2C model• Extracting user requirements through open innovation• Formulating a standard policy specifying a base API

Achieve collaboration
between advanced
applications and create
collaboration variations• Establishing technology for enabling collaboration according
to service-provision conditions and user requests (big data
analysis, security analysis, information virtualization,authentication and authorization technology, etc.)

Clarify OaaS architecture• Specifying a general-purpose interface based on standard
technology• Creating function/information models according to service
grade

Service Orchestration

Automated collaboration

E2E service management

Legacy network equipment

SDN-ready network equipment

Equipment controllable
by OpenFlow etc.

Virtualized network functions(NFV)

Network functions on cloudFig. 3. Service Orchestration.

Table 3. Service Orchestration: challenges and recent activities.
Challenges

Recent activities

Clarify envisioned scenarios (scope ofbusiness)• Clarifying business requirements and network function requirements• Studying use cases such as NFVCreate an information management model• Studying a network/server resource management system• Studying standard management models such as TMF

Establish function mapping and interface
provisions• Deploying functions for achieving Service Orchestration(NMS, EMS, orchestrator, etc.)• Studying multi-grade management technology tailored to customers

Establish migration system• Studying a migration system that considers migration from existing OSSAssess range of use for market
technologies and standardized
technologies• Studying orchestrator technology based on standardization trends• Assessing trends in virtualization studies of NFV/TMF

EMS: element management system
NMS: network management system
OSS: operation support system
TMF: TeleManagement Forum

Vol. 13 No. 3 Mar. 2015



Feature Articles

in business operations (the portion of operations performed manually). This technology covers the range
from simple operation support to drastic revision ofprocesses; it addresses individual on-site environments that have been difficult to deal with in conventional system development and is intended to directlyreduce the workload on operators. R&D efforts areunderway in the Access Network Operation Projectwith the aim of creating a navigation framework thatcollects, consolidates, and processes individualdependent know-how and materials used for decision-making in manual operations and feeds that
information back to operators. Three specific technologies that are part of these R&D efforts aredescribed in this section: Unified Management Support System (UMS) [2] for automating repetitive
operations on a personal computer (PC); DataBridge[3] for transferring data securely between different
networks; and annotation technology for overlaying
various types of supplementary information on theoperator’s screen.
4.1 UMS
UMS software technology is designed to reduce theworkload on operators by automating terminal operations performed on a PC. Its functions range fromautomatic recording of a sequence of operations to
executing operations on behalf of the operator. UMS
can automate relatively simple repetitive data-input
operations performed on a Windows*3 OS and significantly reduce the operation workload on theoperator. The main features of UMS are: (1) a function for automating operations and executing them onbehalf of the operator; (2) a function that enablesscenarios to be automatically generated by simply
having the operator perform ordinary operations withrespect to a certain application, and that enables thosescenarios to be visually edited; and (3) simple implementation by copying the UMS file to the computer
without having to modify the target system or perform a program installation. UMS software has
already reached the practical stage and has been marketed by NTT Advanced Technology under the product name WinActor.
4.2 DataBridge
DataBridge is technology for smoothly linking systems at minimal cost while making use of existing
security policies. Conventional practices for transferring data such as copying files between PCs using a
USB (universal serial bus) memory stick or inputting
printed information into a terminal on a different network would raise security concerns because of thepossibility of losing physical media. DataBridge, incontrast, enables secure data transfer between
detached networks without having to modify theexisting system or network. In particular, it enablesdetailed security policies to be added such as allowing the transfer of PDF (portable document format)
files but prohibiting the transfer of Excel files, orallowing the transfer of data for only specific users or
specific time periods. In short, DataBridge can appropriately limit the types of information transferred
between networks. It also preserves a record of thetransferred information in the form of a log, thereby
enabling operations that follow existing security policies. DataBridge has also reached the practical stage
and is being marketed by NTT Software Corporation
under the product name Crossway/DataBridge.
4.3 Annotation technology
Windows*3 includes a function for displaying help
in the form of balloons when placing the mouse cursor over an item, but annotation technology facilitatesuser navigation through an application by enabling
the user to add any type of supplementary information anywhere on an operation screen without having
to upgrade the application (Fig. 4). In short, annotation technology enables a user to freely and directly
display know-how anywhere on an operation screen.
It can be used, for example, to display operation
assistance after deploying a new system, to provide
beginners with support in using an application thatinvolves complicated terminal operations, and to display help information on the screen in the native
language of foreign-language-speaking users. It alsoenables annotations to be edited easily by anyone via
a GUI (graphical user interface) on an editing screen.
Some of the functions of this annotation technology
are now under development toward a prototype product.
5. Future outlook
Finding ways of responding to the diverse needs ofservice providers in a low-cost and rapid manner isessential to implementing the Hikari Collaboration
Model. At the same time, the portion of operations
run by people in meeting these needs must be mademore efficient. NTT Access Network Service Systems Laboratories is committed to conducting ongoing research of access network operation in order to*3 Windows is a registered trademark of Microsoft Corporation.

NTT Technical Review

Feature Articles

Annotation marks
ToolboxAnnotations as displayed
ToolboxFirst, use the snipping tool

Click or placecursor over mark
• Overlay annotations on any screen without upgrading the application• Display information whenever and wherever needed<Examples> • Create and edit annotations easily in parallel with actual work and operations
Beginners
start here.

10 users

3 users

Fig. 4. Annotation technology.

respond optimally to these needs and to help create aprosperous and enriched society.
References
[1]
[2]

[3]

“Hikari Collaboration Model,” NTT press release published on May
13, 2014.
http://www.ntt.co.jp/news2014/1405eznv/ndyb140513d_01.html
H. Adachi, K. Hotta, F. Yokose, T. Toyoda, and A. Inoue, “UMS:
Software for Automating Operators’ Actions to Rapidly Improve
Operational Efficiency at Low Cost,” NTT Technical Review, Vol. 12,
No. 2, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
02fa1.html
H. Adachi, N. Nawa, F. Yokose, K. Tsuchikawa, and A. Inoue, “DataBridge: Technology to Transfer Data Securely and Efficiently
Between Terminals Connected to Different Networks,” NTT Technical Review, Vol. 13, No. 1, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2015
01ra2.html

Vol. 13 No. 3 Mar. 2015

Author profile
Career highlights
Project Manager, Access Network Operation
Project, NTT Access Network Service Systems
Laboratories.
Jun Nishikido received the B.E. in electricalengineering from Waseda University, Tokyo, in
1986; he joined NTT the same year. He received
the 2000 Best Paper Award from the Institute ofElectronics, Information and Communication
Engineers (IEICE). He is currently engaged instrategy planning of operation system R&D andresearch on SDN/NFV in access networks. He isa member of IEEE (Institute of Electrical andElectronics Engineers) and IEICE.

Regular Articles

Development of 100-Gbit/s Packet
Transport System
Takeshi Kawasaki, Masaaki Inami, Yoshiaki Sasakura,
Daisaku Shimazaki, Makoto Horiguchi,
and Katsutoshi Koda
Abstract

A rapid increase in the amount of Internet traffic is expected in the core network of the NTT Group
due to the growing popularity of mobile and cloud services. NTT Network Service Systems Laboratories
has developed a 100-Gbit/s packet transport system (100G-PTS) in order to increase the network
capacity cost-effectively. Moreover, 100G-PTS also improves the operability and reliability of thetransport system, which is expected to reduce operational expenditures. This article presents an overview
of 100G-PTS and its technical features.
Keywords: 100G, digital coherent technology, MPLS-TP

1. Introduction
The trend of steadily increasing Internet trafficmeans that transport systems with higher capacity are
required in the carrier network. To provide sufficient
capacity economically, NTT Network Service Systems Laboratories has developed a next-generation
optical transport system called a 100-Gbit/s packet
transport system (100G-PTS) that makes it possible
to deliver 100-Gbit/s high speed data traffic using
digital coherent technology and also to accommodate
data traffic efficiently using packet transport technology. The goals for this development, in addition toenhancing the capacity, are to improve the operability
and reliability of the system by integrating the equipment in different layers and by simplifying the network, and to reduce power consumption in order toreduce the total operational expenditure (OPEX). In
the near future, we will be able to further save costsof Layer-3 equipment such as relay routers by using
100G-PTS (Fig. 1). Thus, 100G-PTS will be our key
system in the NTT Group.



2. Overview of 100G-PTS and its key
technical features
There are three key technical features in 100G-PTS,
which bring certain advantages, as follows (Fig. 2):(1)	Capacity enhancement by 100-Gbit/s digital
coherent technology(2)	High operability and reliability by high performance optical switching technology that
achieves compatibility between flexible bandwidth setting of the circuit and advanced operations, administration, and maintenance (OAM)
functions through the use of MPLS-TP (MultiProtocol Label Switch Transport Profile) technology(3)	Cost reduction by integration of both optical(Layer-0) and packet switching (Layer-2) in asingle system
2.1 1 00-Gbit/s transmission with digital
coherent technology**

Digital coherent technology: Technology that uses high speed
digital signal processing (DSP). It can drastically mitigate thelimitations of transmission distance due to optical waveform distortion through the optical fiber cable.

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Conventional network

Future network(1) High speed WDM transmission
with 100-Gbit/s waves(4) Increased number of
unnecessary IP processes atrelay routers
Relay router
Edge router(1) Transmission by 10-Gbit/s
based technology
Layer Edge router Relay router
Layer 3

Edge router
Layer(4) Cutting through relay routers withcombination of OXC & packet switching

Relay router Relay router Edge router

Layer 3Layer 2

Layer 2

Layer
0/1

Layer 0(3) Reducing thenumber of NE-OpS
by integrating
systems between
layers(2) Back-to-back connection
required between layers(3) NE-OpS foreach system[Legend]L2 switch

10G wave

Transport
equipment (WDM)

100G wave

Packet switching

Logical path(5) Supports futuretechnology such as
beyond 100G
transport(2)• Cost reduction achieved byintegrating the equipment
in different layers• Improving the quality ofoperation under simplified
configuration

OXC

NE-OpS: network element operation system
OXC: optical cross-connect

Fig. 1. Advantages of integrating layers in transport network.

NMS(3) MPLS-TP label path can provide various
kinds of interfaces and bandwidths.

EMS

Link aggregation
Line
card
Line
card
Line
card
Line
card

High speed digital
leased line
IP service network forcorporate
customers

Packetswitch(MPLS-TP)

L2 functional block

Internet/Core network
IP service network
for corporate
customers

10GbE/100GbE
Line
card

GbE/10GbE/100GbE

100GbE

Link aggregation
Packetswitch(MPLS-TP)

Line
card
Line
card

Line
card

(4) Implementation of transponder
function omits the need for
additional interface between the twofunctional blocks. It also improves
system reliability.

Line
card
Line
card

L2 functional block
Core routerTransponder(2) Flexible wavelength switching by highperformance optical cross-connect (OXC)

Trans
ponder

10 G × 10(SDH/Ether)

Transponder
Transponder

OXC

OXC

OXC
TransponderL0 functional block

Max 8 directions(1) Accommodation of 10-Gbit/s to 100-Gbit/s signals
enables high capacity & long distance transmission bydigital coherent technology. Fiber measurement for CD
or PMD is no longer required, and in-line DCF modules
are not used.

100 G × 80 λL0 functional block[Legend]100-Gbit/s wave
MPLS-TP Label Switched Path

DCF: dispersion compensating fiber
EMS: element management system
L0: Layer-0
L2: Layer-2
NMS: network management system
SDH: synchronous digital hierarchy

Fig. 2. 100G-PTS key technical features.

Vol. 13 No. 3 Mar. 2015

Regular Articles

Benefits of digital coherent technology
1. High capacity by improved spectral efficiency
2. Long haul transmission by highly sensitive optical coherent detection
3. Strong dispersion compensation by digital signal processing (DSP)

Conventional scheme(2) Design and operation

Current scheme with digital coherence

DC module @ site #A DC module @ site #B DC module @ site #C

Optical cable

High-spec fiber
measurement kits

Site #A(1) Fiber measurement
before deployment

No DC module

No DC module
100-Gbit/s
signals

10/40-Gbit/s
signals

Optical cableFibermeasurement
between sites#A and #B

Site #B

No DC module

Transport
equipment
Site #C(3) Maintenancework(1) Fiber measurement is required at all sites before deployment.
High-spec measurement kits for CD or PMD are also required.
(2) DC modules are fixed based on the results of fiber
measurement in (1). Module types are installed and managedsite by site.
(3) When the cable route is changed due to maintenance work,(1) and (2) are carried out again.

Site #A

Transport
Transport
equipment
equipment
Route change formaintenance
Site #B(No high-spec(No high-spec
measurement kits measurement kits
required)
required)Site #C(No high-spec
measurement kits
required)

Digital coherence scheme has huge tolerance to chromatic
dispersion and PMD, so DC modules no longer need to beinstalled, and fiber measurements for CD and PMD can beskipped. Even when a route change is required, digital
coherence can automatically compensate for the CD/PMD
change of the fiber. Furthermore, the latency is reduced,
since DC modules are unnecessary.

DC: dispersion compensation

Fig. 3. Benefits of digital coherent technology.

In conventional wavelength-division multiplexing(WDM) systems, the maximum speed is 10 Gbit/s or
40 Gbit/s per wavelength. However, using more
10/40-Gbit/s WDM equipment will not be sufficient
to deal with the rapid increase in traffic, and therefore, a new transport system that can drasticallyenhance the capacity with higher speed data transmission is required. Digital coherent technology,
which is a breakthrough technology in the industry,
makes it possible to deliver 100-Gbit/s transmission
per wavelength in 100G-PTS. 100G-PTS can achievea maximum capacity of 8.0 Tbit/s by multiplexing 80
wavelengths of 100-Gbit/s signals.
To speed up the transmission rate (from 10/40
Gbit/s to 100 Gbit/s), spectral efficiency must be
improved. We adopted a multi-level modulation/
demodulation scheme that is widely used in the wireless communication field. However, long haul transmission still presented difficulties because multi-level
modulation is sensitive to the noise generated inside
the fiber during transmission. Polarization mode dispersion (PMD) and chromatic dispersion (CD)induced in the fiber are also factors that limit thetransmission distance. The use of digital coherent
technology resolved these difficulties, as its highspeed digital signal processing (DSP) capability cancompensate for or drastically mitigate distortion due
to noise or PMD/CD during transmission.
Another major advantage of digital coherence is in
deployment and operation (Fig. 3). In conventional
systems, fiber measurements for loss, CD, and PMD
need to be done using high-specification measurement kits before the installation work starts. On thebasis of the results of such measurements, we have to
install the appropriate CD compensation module siteby site. Moreover, if the cable route is altered formaintenance purposes, we have to do the fiber measurements again for other fibers, which requires a lotof extra work. This is no longer necessary when using
100G-PTS with digital coherent technology, however, because CD and PMD can be generally compensated for by DSP. Thus, the measurement kits are no
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Conventional systems

100G-PTS
Manual/Automatic switchingassociated with design system- Provisioning (shelf, circuit packs, etc.)- Add/delete/change optical paths

EMS

EMS
Dispatching local engineer to site toreposition transponder cards andmake new fiber cabling

Dispatching local engineer to site
to reposition transponder cards andchange fiber cabling

No need to dispatch local
engineer to site!

Dispatching local engineer to site
to reposition transponder cards andchange fiber cabling

Route #1
Route #2
Route #3
Optical amplifier

Route #1
Route #2
Route #3
OXC/Optical amplifier

MUX/DMUX
Transponder

MUX/DMUX & selector
Transponder

Direction and wavelength of the path are fixed based on the location of
initially installed transponders.
In case of disaster, the transponder should be removed and reinstalled inanother slot to change the route, and the fiber cabling must be changed
in order to change the wavelength.

Direction and/or wavelength can be easily changed
remotely even if a double fault occurs in the network.

MUX/DEMUX: multiplexer/demultiplexer

Fig. 4. Features of high performance optical switching technology.

longer needed, which reduces the OPEX for suchwork. Moreover, the delay of the system is improved
because no CD module needs to be installed in 100GPTS, which is an advantage for the carrier network.
2.2 H
 igh operability and reliability by highperformance optical switching technology
In a WDM system, a transceiver called a transponder is necessary to generate the optical signal that is
optimized in order to transmit signals a longer distance when it receives signals from external equipment such as service nodes. In conventional systems,
the direction or wavelength of the path is fixed basedon the position of the slot the transponder card isplaced in. Therefore, when we have to change theroute of the optical path or wavelength in the event of
a disaster, we need to dispatch a local engineer to thesite and manually change the slot in which the transponder card is placed. After that, we change the fiberconnection and reconfigure the optical path via the
network element operation system (NE-OpS) (Fig. 4).
This requires a lot of planning for the route change.
Vol. 13 No. 3 Mar. 2015

In 100G-PTS, on the other hand, we can remotelychange the direction and/or wavelength via NE-OpS
by using the high performance optical switch. Thus,
we do not have to dispatch a local engineer to change
the fiber connection and change the slots in which thetransponder cards are placed, and this substantiallyreduces the OPEX of this task. A double fault casethat might occur in a disaster is depicted in Fig. 4, in
which we can repair a commercial circuit by switching to a third route remotely.
2.3 C ompatibility between flexible bandwidth
setting of the circuit and advanced OAM
functions by MPLS-TP technology
In conventional systems, we have generally used
the SDH (Synchronous Digital Hierarchy) format as
an ITU-T (International Telecommunication Union
Telecommunication Standardization Sector) standard
to multiplex and accommodate legacy service trafficsuch as that from landlines or leased lines. In the SDH
scheme, fixed time slots are allocated for each circuit/
path, so the bandwidth is fully occupied even whenRegular Articles

MPLS-TP technology key features
1. Various quality of service (QoS) settings
2. Flexible bandwidth settings
3. Multiple OAM functions and high operability

QoS
Wide range of quality of service can be provided:- High quality path with bandwidth guarantee- Normal quality path as best effort using statisticalmultiplexing effectDiscard packets with low
10G (Not guaranteed)priority when exceeding the
100G wire rate.

Priority level (low)max 10G (Partially guaranteed)minPriority level (medium)
Priority level (high)

10G (Fully guaranteed)
Priority (high)

EMS

OAM functions
OAM frames achieve operation and maintenance quality
equivalent to SDH and ATM formats.
- Continuity check (CC)
Periodic health check of signals- Loop back (LB)
Response check to the designated node
- Delay and loss measurement
Bandwidth setting
Bandwidth can be set with finegranularity, improving the efficiency of
bandwidth utilization.

Priority level (low)Priority level (medium)
Priority level (high)100G optical path

Cost reduction of devices
Devices or components in the cross connect building
block can be commonly used as the devices in thenormal packet switch. This means that these devices canbe used for a longer term even if the legacy productbecome outdated and their devices reach the end ofsales/service (EOS) and the end of life (EOL).

Packet transport network

Fig. 5. Features of MPLS-TP technology.

there is no data traffic in the time slots.
In a packet system such as 100G-PTS, however,packets are generated only when there is some data
traffic on the circuit. Additionally, we can set the pathbandwidth with fine granularity by using packet multiplexing, and we can also set and manage an end-toend label switched path (LSP) as well as set the SDH
technology. When several LSPs are mapped onto thewavelength path, 100G-PTS can mix both types of
LSPs (bandwidth guaranteed and non-bandwidth
guaranteed) in order to effectively use the bandwidth.
It can also configure the redundant LSP paths that
achieve less than 50-ms protection switching, andmoreover, it can provide hitless protection switchingwith no frame loss. Different types of protection
paths are possible based on the operating conditions,so 100G-PTS assures high reliability of the network.
In terms of operation and maintenance, continuity
check (CC) or loop back (LB) testing functions areavailable in 100G-PTS, which supports sufficient
OAM functions to realize high quality operations andmaintenance.



2.4 C
 ost reduction by integrating opticalswitching (in Layer-0) and packet switching(in Layer-2) in a single system
The equipment for WDM (as an optical transportsystem) and TDM (time-division multiplexing) (as anelectrical MUX/DMUX (multiplex/demultiplex)
switch) was generally released as separate units fortransport systems, so an additional transponder wasnecessary to connect both pieces of equipment, andthe cost was relatively higher. The 100G-PTS system
can provide one system that combines the Layer-0
functional block (WDM) and Layer-2 functional
block (packet switch), which reduces the interface
cost by simplifying the connection between the twolayers. It can also save the space needed for the equipment and the power consumption as well.
Because 100G-PTS supports many kinds of interfaces and a number of routes, it can be applied invarious situations in the carrier network. For example,
100G-PTS can configure a multi-ring network, and it
can also remotely switch to the third route in the eventof a disaster, as shown in Fig. 5.

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NMS

Enhancement of remote
operation functions such as
F/W upgrades

EMS

Remote route switching to third route incase of disasters
DCN

Variety of interfaces(GbE to 100GbE) andlogical path multiplexing aresupported.
Leased linenode
L2 switch
100 G × 80 λRouterCapacity enhancement& layer integration
DCN: data communication network
FW: firmware[Legend]100G-PTS L2 functional block
100G-PTS L0 functional block

Fig. 6. Schematic of 100G-PTS network (summary).

3. Conclusion
Against the background of increasing demand forInternet traffic, NTT has developed 100G-PTS,
which brings sufficient capacity and achieves highoperability and reliability as summarized in Fig. 6.
The demand for equipment that consumes less powerhas been growing in recent years because the rapidly
increasing heat density (per rack) requires a powerfulVol. 13 No. 3 Mar. 2015

air cooling system, which drives up the cost of facilities. This in turn raises the CAPEX (capital expenditure)/OPEX. In the near future, we will focus ondeveloping technology that can reduce the power
consumption in 100G-PTS, and we will also continue
to investigate further high performance technologies
such as 400-Gbit/s transmission and SDN (softwaredefined networking).

Regular Articles

Takeshi Kawasaki

Senior Research Engineer, Transport Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.S. in physics from Keio
University, Tokyo, in 2001 and the M.A. in artsand sciences from the University of Tokyo in
2003. He joined NTT Network Service Systems
Laboratories in 2003 and studied optical transmission systems. He also worked on the development project for optical transport systems. During 2011–2014, he was involved in international
submarine cable projects at NTT Communications. He has been in his current position since
July 2014 and is engaged in developing 100Gbit/s packet transport systems (100G-PTS). He
is a member of the Institute of Electronics, Information and Communication Engineers (IEICE).

Masaaki Inami

Research Engineer, Transport Network Innovation Project, NTT Network Service Systems
Laboratories.
He received the B.S. in electronics and information science from Kanazawa University, Ishikawa, in 2002 and the M.S. from the Japan
Advanced Institute of Science and Technology,
Ishikawa, in 2004. He joined NTT Network Service Systems Laboratories in 2004 and was
involved in research and development of the Next
Generation Network (NGN). He has been in his
current position since July 2010 and is engaged
in developing 100G-PTS. He is a member of theInstitute of Information Processing Society ofJapan (IPSJ).

Yoshiaki Sasakura

Research Engineer, Transport Network Innovation Project, NTT Network Service Systems
Laboratories.
He received the B.S. and M.S. in electronics
from Kyoto University in 1994 and 1996, respectively. He joined NTT in 1996 and was involved
in designing and planning network infrastructures in Long Distance Telecommunication Division. He was with Network Operation Division in
NTT Communications during 1999–2007. He
was with Ubiquitous Service Division during
2007–2009, with Business Network Operation
Division during 2009–2011, and with Network
Service Division during 2011–2012. Since July
2012, he has been in a current position and he isengaged in the development project for 100GPTS.



Daisaku Shimazaki

Senior Research Engineer, Transport Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.S. in applied chemistry andthe M.S. in materials science from Keio University, Kanagawa, in 1999 and 2001, respectively.
He joined NTT Network Service Systems Laboratories in 2001, where he researched and developed multi-layer network virtualization as a
Research Engineer. He has been in his current
position since January 2014 and is engaged indeveloping 100G-PTS. He is a member of
IEICE.

Makoto Horiguchi

Senior Research Engineer, Transport Network
Innovation Project, NTT Network Service Systems Laboratories.
He received the B.S. in electronics from the
University of Tokyo in 1990. He joined NTT in
1990. During 1999–2009, he was involved inoperation and maintenance for transport andleased line systems at NTT EAST. He also
worked on traffic management and a development project for operation systems. He has beenin his current position since July 2009 and isengaged in developing 100G-PTS.

Katsutoshi Koda

Director, Transport Network Innovation Project, NTT Network Service Systems Laboratories.
He received the B.S. and M.S. in mechanicalsciences from Tokyo University of Science in1987 and 1989, respectively. Since joining NTT
in 1989, he had been engaged in the developmentof transport systems at the Network System
Development Center. During 1999–2000, he wasengaged in human resource management at NTT
EAST, and during 2001–2004, he was with theglobal procurement office at NTT. He was withNTT EAST during 2005–2007 and with NTT
Network Systems Laboratories during 2008–2011. He has been in his current position since
July 2014. He manages the development projectfor 100G-PTS. He also manages research anddevelopment for future optical networking andtransport network management technology.

NTT Technical Review

Global Standardization Activities

Standardization Trends for
Next-Generation Passive Optical
Network Stage 2 (NG-PON2)
Kota Asaka and Jun-ichi Kani
Abstract

The FSAN (Full Service Access Network) Group and ITU-T (International Telecommunication
Union-Telecommunication Standardization Sector) are actively working to develop new standards inorder to achieve high capacity transmission, multiple service capability, and flexible network operationin future optical access network systems. This article reports on the standardization trends of NG-PON2(Next-Generation Passive Optical Network Stage 2) systems that are being developed under a frameworkof the ITU-T G.989 series.
Keywords: ITU, optical access, NG-PON2

1. Introduction

2. NG-PON2

To meet the large demand for high capacity transmission in optical access systems, a 10-Gigabitcapable PON (passive optical network) has alreadybeen standardized by IEEE (Institute of Electricaland Electronics Engineers) and ITU-T (International
Telecommunication Union-Telecommunication
Standardization Sector). To enable cutting-edge standardization of future optical access systems, theFSAN (Full Service Access Network) Group and
ITU-T SG15/Q2 (Study Group15/Question 2) arecurrently discussing the specifications of a 40-Gigabit-capable PON, which employs wavelength-division multiplexing (WDM) technology, for the purpose of enabling cost-effective 40-Gigabit-capabletransmission capacity and multiple service capability.
The FSAN Group is a forum for discussing future
optical fiber access networks, and FSAN member
companies offer their contributions to ITU-T SG15/
Q2 in order to promote the development of international standards for PON systems.

In 2010, FSAN initiated discussions on a 40-Gigabit-capable PON known as NG-PON2 (Next-Generation Passive Optical Network Stage 2), which is going
to be standardized in the ITU-T Recommendation
G.989 series. Table 1 lists the framework and standardization status of the G.989 series recommendations.
As the table indicates, the G.989 series consists ofrecommendations G.989, G.989.1, G.989.2, andG.989.3. The G.989 recommendation specifies NGPON2 definitions, abbreviations, and acronyms andwill be consented in July 2015. The G.989.1 recommendation, which covers the general requirements
for NG-PON2, was approved in March 2013. The
G.989.2 recommendation, which specifies the physical media dependent (PMD) layer including the
wavelength plan and power budget of NG-PON2, wasconsented in December 2013 and approved in
December 2014. The G.989.3 recommendation
specifies particulars for the transmission convergence(TC) layer of NG-PON2 such as the wavelength protocol and bandwidth allocation, and is targeted forconsent in July 2015. These achievements so far suggest that the standardization of the G.989 series will

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Global Standardization Activities

Table 1. Framework and status of ITU-T G.989 series recommendations.
Recommendation

Title

Status

G.989

40-Gigabit-capable passive optical networks (NG-PON2):
Definitions, abbreviations, and acronyms

To be consented(Jul. 2015)

G.989.1

40-Gigabit-capable passive optical networks (NG-PON2):
General requirements

Consented (Jul. 2012)
Approved (Mar. 2013)

G.989.2

40-Gigabit-capable passive optical networks (NG-PON2):
Physical media dependent (PMD) layer specifications

Consented (Dec. 2013)
Approved (Dec. 2014)

G.989.3

40-Gigabit-capable passive optical networks (NG-PON2):
Transmission convergence (TC) layer specifications

To be consented(Jul. 2015)

Mobile service
RRH
PtP WDM overlay

TWDM
TWDM
TWDM
TWDM

RouterPtP WDMBBU

Residential users

Mobile networks

OLT

Core networks

Business users

ONU
BBU: baseband unit
OLT: optical line terminal
RRH: remote radio head

Fig.1. Example architecture of NG-PON2 system.

be completed in 2015 or 2016.
2.1 System architecture
An example of NG-PON2 system architecture isshown in Fig. 1. Although the previous PON systems
offer broadband service only for residential users,
NG-PON2 systems are expected to accommodate
business users and mobile users in addition to residential users. The primary NG-PON2 solution iscalled TWDM (time and wavelength-division multiplexing)-PON, which is a hybrid of conventional
TDM (time-division multiplexing) and WDM technologies. Optionally, NG-PON2 also supports Pointto-Point (PtP) WDM overlay, which is expected to besuitable for mobile services that require low latency.
Vol. 13 No. 3 Mar. 2015

In NG-PON2, colorless optical network units (ONUs)
are mandatory for reducing system operating expenses because they can eliminate the complicated inventory management of ONUs.
2.2 General requirements
Table 2 lists the general requirements for NGPON2 that are specified in G.989.1 [1]. In TWDMPON there are four (optionally eight) multiplexed
wavelengths for upstream and downstream, respectively. In an NG-PON2 network there are three typesof line rates (per wavelength) of 10-Gbit/s symmetry,
2.5 Gbit/s and 10 Gbit/s for upstream (US) and downstream (DS), respectively, and 2.5-Gbit/s symmetry.
Therefore, the transmission capacities for each lineGlobal Standardization Activities

Table 2. General requirements for NG-PON2.
SystemTWDM-PON (primary)
PtP WDM overlay (option)

Capacity*1

DS*2 40G (10G × 4λ), US*3 40G (10G × 4λ)DS 40G (10G × 4λ), US 10G (2.5G × 4λ)DS 10G (2.5G × 4λ), US 10G (2.5G × 4λ)Logical split ratio

1:256

Distance*4

40 km (without repeater)

Co-existence

All legacy PONs (RF video included)Service

Residential and business users,
mobile backhaul, and other applications*1 For 4 wavelengths (λ)*2 Downstream*3 Upstream*4 The maximum split ratio at this distance will depend on the budget class.

TWDM
US

TWDM 1596–1603 nm
DS

Wide
Widebandband option:
option: 1524–1544
1524-1544 nm
NG-PON2 (G.989.2)

Shared spectrum:
1603–1625 nm

Reduced
Reducedband
band option:
option: 1528–1540
1524-1540 nm
Narrow
Narrowband
band option:
option: 1532–1540
1532-1540 nm

Expanded spectrum: 1524–1625 nm
DS

US
10G-EPON
XG-PON

1575–1580 nm

1260–1280 nm
US

GE-PON
G-PON

Regular: 1260–1360 nm
Reduced: 1290–1330 nm
Narrow: 1300–1320 nm

1200

1260

PtP WDM
overlay

1300

DS
GE-PON, G-PON

Video
1550–1560 nm

G-PON

1360

1400

1480

1500

1600

1625 (nm)Fig. 2. Wavelength plan for NG-PON2.

rate are 40-Gbit/s symmetry, 10 Gbit/s (US) and 40
Gbit/s (DS), and 10-Gbit/s symmetry. The 40-Gbit/s
symmetric capacity is expected to be applicable tobusiness users, and the 10/40-Gbit/s asymmetriccapacity to residential users. In G.989.1, the logicalsplit ratio and the transmission distance are specified
as 1:256 and 40 km, respectively. However, the optimum capacity, split ratio, and distance may dependon the NG-PON2 system services or applications.
Therefore, G.989.1 shows combinations of these tobe supported, for example, a 40-Gbit/s optimum
capacity (DS), 20-km distance, and 1:64 split ratio.


2.3 Wavelength plans
The NG-PON2 wavelength plan specified in
G.989.2 [2] is shown in Fig. 2, along with other system plans for comparison. To support co-existencewith legacy PON systems that include an RF (radio
frequency) video system, G.989.2 specifies 1524–
1544 nm (wide band option) and 1596–1603 nm for
US and DS, respectively. Two other options are also
specified for the US plan: a reduced band option(1528–1540 nm) and a narrow band option (1532–
1540 nm). These three options are specified by taking
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Global Standardization Activities

λ1u
ONU 1
ONU 2
ONU 3

OLT

λ2u

OSU #1λ2u

OSUt #2

λ3u

OSU #3ONU 4
λ1u
Tune to λ1u

ONU 1
ONU 2

Tune to λ3u

ONU 3Failure

λ1u

OLT

Fixed
OSU #1λ3u

OSU #2λ3u

ONU 4

OSU #3Fig. 3. Example of OLT protection technology using wavelength tuning in ONUs.

into account the wavelength channel spacings (min.
50 GHz, max. 200 GHz) and the tunable components
implemented in ONUs. Since the C band is to be used
for US in NG-PON2, a dispersion compensation
technique would be necessary for a line rate (perwavelength) of 10 Gbit/s. For the wavelength plan for
PtP WDM overlay, shared spectrum (1603–1625 nm)
usage is specified for co-existence with legacy PONs.
Expanded spectrum (1524–1625 nm) usage is also
specified for greenfield applications. As mentioned
above, G.989.2 specifies the wavelength band for PtP
WDM overlay, but it does not specify the number ofwavelengths or the wavelength allocation for US andDS.
The contents of G.989.3 are currently being discussed in FSAN and ITU-T. Basically, G.989.3 may
be specified on the basis of G.987.3, which is the TC
layer specifications for a 10-Gigabit-capable PON,
with supplementary contents related to the wavelength assignment protocol.
3. Expected network function by in-service
wavelength tuning
In developing colorless ONUs for NG-PON2, it isessential for the ONU transmitter and receiver to havewavelength tunability. Therefore, it is expected thatusing the in-service wavelength tuning technique in
ONUs will enable NG-PON2 systems to haveadvanced network functions. In addition, cost-effective tunable components are important for practical
deployment. The term in-service tuning means thatan ONU can tune its wavelength during service
operation in addition to the ONU’s initialization proVol. 13 No. 3 Mar. 2015

cess. An example of an advanced network function
called OLT (optical line terminal) protection is illustrated in Fig. 3. As shown at the top right, the OLT iscomposed of three OSUs (optical subscriber units),
and different wavelengths are assigned to each one. Ina normal state, OSU #1, OSU #2, and OSU #3 communicate with ONU 1 (λ1u), ONU 2 and ONU 3 (λ2u),
and ONU 4 (λ3u), respectively. Upon assuming a failure in OSU #2, ONU 2 and ONU 3 immediately tune
their wavelengths to maintain communications withother OSUs. As shown at the bottom left, ONU 2changes its wavelength from λ2u to λ1u in order to beconnected to OSU #1, while ONU 3 changes its
wavelength from λ2u to λ3u to be connected to OSU#3. One of the advantages of the OLT protection isthat ONUs with the in-service tuning technique caneasily provide a protection function without additional equipment, such as a backup OLT and an optical switch. Another example of in-service tuning is an
OSU sleep function, which is also attractive as ameans of reducing power consumption in the OLT.
With this function, all ONUs are connected to one (orfewer) OSU(s), and the other OSUs can be forced tosleep. This function is also implemented by using
wavelength tuning during service operation. For
these advanced functions, a tunable component isrequired to have a short tuning time in order to avoid
any signal frame loss even during a tuning process.
On the other hand, such a fast tunable component is
not needed if an operator requires wavelength tuning
only for ONU initialization. In accordance with theaforementioned background, G.989.2 specifies tuning time classes, which are categorized into class 1(<10 µs), class 2 (10 µs–25 ms), and class 3 (25 ms–Global Standardization Activities

1 s). The categorization is specified by taking into
account the requirements from expected network
functions in NG-PON2 and the current technologies
of tunable components.
4. Future prospects
This article reviewed NG-PON2 as the latest standardization trend for future optical access networks.
In the near future, FSAN and ITU-T will focus on
discussing PtP WDM overlay specifications as an

Kota Asaka

Senior Research Engineer, Optical Access
System Project, NTT Access Network Service
Systems Laboratories.
He received the B.S. and M.S. in electricalengineering from Waseda University, Tokyo, in
1996 and 1999, respectively, and the Ph.D. inphysics from Kitasato University, Tokyo, in
2008. In 1999, he joined NTT Photonics Laboratories, where he researched photonic integrated
circuits and long-wavelength VCSELs (verticalcavity surface emitting lasers). From 2005–2008,
he was engaged in research on OCT (opticalcoherence tomography) using SSG-DBR-LDs(super-structure-grating distributed Bragg reflector laser diodes) in collaboration with Kitasato
University. From 2009–2012, he worked on thedevelopment of low-cost and small optical subassemblies for optical access networks. He hasserved as the working group secretary of TC(Technical Committee) 86/SC (Subcommittee)
86C/WG (Working Group) 4 of the IEC (International Electrotechnical Commission), and has
worked on the international standardization offiber optic systems and active devices. Since
2012, he has been with NTT Access Network
Service Systems Laboratories and has been
engaged in international standardization efforts
for next-generation optical access systems in
ITU-T SG15/Q2 and FSAN. He is a member of
the IEEE Communications Society, the Instituteof Electronics, Information and Communication
Engineers (IEICE), and the Japan Society ofApplied Physics.

amendment to the G.989 series. It is also expectedthat further evolution of optical access network technologies will be discussed in FSAN and ITU-T.
References[1][2]

ITU-T Recommendation G.989.1:40-Gigabit-capable passive optical
networks (NG-PON2): General requirements.
ITU-T Recommendation G.989.2:40-Gigabit-capable passive optical
networks (NG-PON2): Physical media dependent (PMD) layer specifications.

Jun-ichi Kani

Senior Research Engineer, Supervisor / Distinguished Researcher, Optical Access System
Project, NTT Access Network Service Systems
Laboratories.
He received the B.E., M.E., and Ph.D. inapplied physics from Waseda University, Tokyo,
in 1994, 1996, and 2005, respectively. In 1996,
he joined the NTT Optical Network Systems
Laboratories, where he was engaged in researchon optical multiplexing and transmission technologies. Since 2003, he has been with NTT
Access Network Service Systems Laboratories,
where he is involved in the research and development of optical communications systems for
metro and access applications. He received the
Leonard G. Abraham Prize from the IEEE Communications Society, the Best Paper Award fromthe 18th Optoelectronics and Communications
Conference (OECC) in 2013, and 7 other academic/industry awards. He has been participatingin ITU-T and working on the FSAN initiative
since 2003. He has served as Associate Rapporteur of ITU-T Q2/15 (optical systems for fibre
access networks) since 2009. He is a member ofIEEE and IEICE.

NTT Technical Review

External Awards
2014 Specially Selected Paper
Winner: Akihiro Miyata, Shunichi Seko, Ryosuke Aoki, Ryo Hashimoto, Tatsuro Ishida, Takashi Isezaki, Masahiro Watanabe, andMasayuki Ihara, NTT Service Evolution Laboratories
Date: January 15, 2015
Organization: Information Processing Society of Japan (IPSJ)

IEICE Electronics Society LQE Young Researchers Award
Winner: Kengo Nozaki, NTT Basic Research Laboratories
Date: December 19, 2014
Organization: Technical Committee on Lasers and Quantum Electronics (LQE), Electronics Society (ES), The Institute of Electronics,
Information and Communication Engineers (IEICE)

For “An Information Display System Using Digital Signage andMobile Devices for Multiuser Environments.”
We propose a digital signage system by which multiple users canaccess different content at the same time, and we report the results ofa field evaluation. Some existing digital signage systems display
multiple content in the beginning, then expand the detail of one typeof content over the entire screen in response to requests from users.
However, this method has the potential to fill only one user’s needsince the details of only one content selection occupy the entire
screen. Our method enables several users to control her/his pointer toselect certain content on the digital signage screen and browse detailsof the content on the mobile device immediately. This design also
allows users to know which content is being watched by many others.
The field evaluation (105 subjects) in Kumamoto City proved that oursystem is easy to use and acceptable for general users.
Published as: A. Miyata, S. Seko, R. Aoki, R. Hashimoto, T. Ishida,
T. Isezaki, M. Watanabe, and M. Ihara, “An Information Display
System Using a Digital Signage and Mobile Devices for Multiuser
Environments,” IPSJ Journal, Vol. 56, No. 1, pp. 106–117, January
2015 (in Japanese).

For “InGaAs Photodetectors Based on Photonic Crystal Waveguide Including Ultrasmall Buried Heterostructure.”
Ultrasmall InGaAs photodetectors based on a photonic crystal
waveguide with a buried heterostructure (BH) were demonstrated forthe first time. A sufficiently high DC (direct current) responsivity of~1 A/W was achieved for the 3.4-μm-long detector. The dynamic
response revealed a 3-dB bandwidth of 6 GHz and a 10-Gb/s eye
pattern. These results were thanks to the strong confinement of bothphotons and carriers in a small BH and will pave the way for unprecedented nano-photodetectors with a high quantum efficiency andsmall capacitance. Our device potentially has an ultrasmall junction
capacitance of much less than 1 fF and may enable us to eliminate
electrical amplifiers for future optical receivers and subsequentultralow-power optical links on a chip.
Published as: K. Nozaki, S. Matsuo, K. Takeda, T. Sato, T. Fujii, E.
Kuramochi, and M. Notomi, “InGaAs Nano-photodetectors Based on
Photonic Crystal Waveguide Including Ultrasmall Buried Heterostructure,” Technical Report of IEICE. OPE, Vol. 113, No. 394, pp.
307–310, January 2014 (in Japanese).

Papers Published in Technical Journals andConference Proceedings
Synergistic Effect between Image and Sound in 3D Audio/
Visual Communication System
H. Takada, M. Date, Y. Kurokawa, Y. Honda, and A. Kojima
Proc. of EVCP 2014 (the 37th European Conference on Visual
Perception), p. 36, Belgrade, Serbia, August 2014.
We developed a natural telecommunication system from a realistic
spatial composition made with a high-fidelity position representation. This position representation is induced using three-dimentional(3D) imaging and acoustic technology. An image was produced using
a stable 3D image generated by an edge detection method in thedepth-fused 3D (DFD) visual perception. The sound was produced
using acoustic wave field synthesis. The system provides realistic,
natural, and comfortable communication by reproducing the distanceand position of the image and sound without inconsistency. Using oursystem, we evaluated how images and sound together influence therelation between vision and hearing. The experiment varied the 3D
position and timing of an image and sound, and the results showedthat eye movements were pulled in the direction of the sound. In the
future, we will develop an innovative hyper-reality communication
system in which 3D sounds can guide the gaze-point on 3D images.

Efficient Virtual Network Optimization across Multiple
Domains without Revealing Private Information
T. Mano, T. Inoue, D. Ikarashi, K. Hamada, K. Mizutani, and O.
AkashiProc. of ICCCN 2014 (the 23rd International Conference on Computer Communications and Networks), pp. 694–701, Shanghai,
China, August 2014.

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

Building optimal virtual networks across multiple domains is an
essential technology to offer flexible network services. However,existing research is founded on an unrealistic assumption that providers will share their private information including resource costs.
Providers, as is well known, never actually do that to remain competitive. Technically, secure multiparty computation, which is acomputational technique based on cryptography, can be used tosecure optimization, but it is too time-consuming. This paper presents
a novel method to optimize virtual networks built over multiple
domains, with great efficiency but without revealing any private
information. Our method employs secure multi-party computation
but only for masking sensitive values; it can optimize virtual networks under limited information without requiring a time-consuming
technique. It is solidly based on the theory of optimality and isassured of finding reasonably optimal solutions. Experiments showthat our method is fast and optimal in practice even when concealing
private information; it finds nearly optimal solutions in just a few
minutes for large virtual networks with tens of nodes. This is the firstwork that can be implemented in practice for building optimal virtual
networks across multiple domains.

Convex Object Surface Mapping for Wide-field of View
Video Representation
D. Mikami, D. Ochi, and A. Kojima
IEEJ Transactions on Electronics, Information and Systems, Vol.
134, No. 10, pp. 1451–1457, October 2014.
This paper proposes a new video representation method for videos
capturing events held in a wide field. Such events can be captured
with high resolution thanks to the recent development of video capturing technologies. Despite the development of these technologies,
progress in representation methods for wide field-of-view (wideFOV) video is quite limited. Some methods prioritize ease of overviewing, and forgo detailed observations; other methods put a highpriority on detailed observations while sacrificing overviewing. Our
work is aimed at simultaneously achieving (1) high visibility forregions of interest (ROIs), (2) easy overviewing, and (3) intuitive
comprehension of the relative positions of video objects. Because of
these advantages, the proposed method is especially suitable forshowing wide-FOV videos on small display devices such as tabletsand smartphones. To achieve the abovementioned aims, this paper
propose a convex object surface mapping technique that provides
high ROI visibility and easy overviewing. In addition, by selecting an
elliptic cylinder or an oval as a convex object, the convex object surface mapping enables intuitive comprehension of the relative positions of video objects. The efficacy of the proposed method wasverified through objective and subjective experiments.

Low-power Liquid Crystal Driving Technique Based on
Capacitors for 1-Pixel Displays
H. Manabe, M. Date, H. Takada, and H. Inamura
Proc. of IDW 2014 (the 21st International Display Workshops), pp.
1343–1346, Niigata, Japan, December 2014.
Liquid crystal displays (LCDs) are suitable as elements for wearable and ubiquitous computing, thanks to their low power consumption. A technique that drives LCDs with lower power is proposed. It
harvests charges on the LCD and stores them in an additional capacitor for reuse when the polarity changes. A simulation shows that thetechnique reduces the charge requirements by up to 50%. An experiment on a prototype shows that the reduction is only partially offset
by the overhead of micro-controller operation. Overall, a 30% reduc-Vol. 13 No. 3 Mar. 2015tion was achieved with large 1-pixel LCDs. With a small 10 × 10-mm
LCD, the overhead matched the reduction and no improvement wasmeasured.

Sodium-ion Insertion/Extraction Properties of Sn-Co
Anodes and Na Pre-doped Sn-Co Anodes
Y. Yui, Y. Ono, M. Hayashi, Y. Nemoto, K. Hayashi, K. Asakura,and H. Kitabayashi
Journal of the Electrochemical Society, Vol. 162, No. 2, pp.
A3098–A3102, January 2015.
The electrochemical properties of Sn-Co were investigated toshow the correlation between the cycle performance and the bindersof electrode component materials. Sn-Co electrodes with polyacrylicacid (PAA) exhibited a better cycle property (about 300 mAh/g up to
30 cycles) than those with polyvinylidene difluoride (PVdF). Thisbetter cycle property with PAA was due to the slight change in thevolume of the electrode that occurred during cycling as revealed byin-situ light microscopy. In addition, Na pre-doping in Sn-Co electrodes improved the average coulombic efficiency from 95.4% to99.9% at 2–10 cycles.

Recognizing the Use of Portable Electrical Appliances
Using Battery-shaped Sensor NodeT. Maekawa, Y. Kishino, Y. Yanagisawa, and Y. Sakurai
IPSJ Journal, Vol. 56, No. 1, pp. 229–238, January 2015 (in Japanese).
This paper proposes a battery-shaped sensor node that can monitor
the use of an electrical device into which it is inserted by sensing theelectrical current passing through the device. We live surrounded bylarge numbers of electrical devices and frequently use them in ourdaily lives, and so we can estimate high-level daily activities by recognizing their use. Therefore, many studies on ubiquitous and wearable sensing devices have attempted to recognize the use of electricaldevices by attaching sensor nodes to the devices directly or by attaching multiple sensors to a user. With our node, we can easily monitor
the use of an electrical device simply by inserting the node into thebattery case of the device. We also propose a method that automatically identifies which electrical device the sensor node is inserted intoand recognizes electrical events related to the device by analyzing thecurrent sensor data.

Recognizing the Use of Portable Electrical Appliances
Using Hand-worn Coil
T. Maekawa, Y. Kishino, Y. Yanagisawa, and Y. Sakurai
IPSJ Journal, Vol. 56, No. 1, pp. 239–249, January 2015 (in Japanese).
This paper describes the development of a new finger-ring shaped
sensor device with a coil of wire for recognizing the use of handheld
electrical devices such as digital cameras, cellphones, electric toothbrushes, and hair dryers by sensing time-varying magnetic fields
emitted by the devices. Recently, sensing the usage of home electricaldevices has emerged as a promising area for activity recognition studies because we can estimate high-level daily activities by recognizing
the use of electrical devices that exist ubiquitously in our daily lives.
A feature of our approach is that we can recognize the use of electrical devices that are not connected to the home infrastructure without
the need to equip them with sensors. We evaluated the performanceof our approach by using sensor data obtained from real houses. ThePapers Published in Technical Journals and Conference Proceedings

evaluation revealed that our approach can successfully recognize theuse of appliances with motors.

NTT Technical Review