NTT Technical Review
May 2011 Vol. 9 No. 5
View from the Top hinichi Yamada, Executive Vice President & Representative Director,
S
CTO, NTT DATA CORPORATION

Feature Article:
NTT R&D Forum 2011 Panel Discussion
Noritaka Uji, Representative Director andSenior Executive Vice President, CTO, and CIO, NTT

Feature Articles:
NTT Tsukuba Forum 2010 Workshop Lectures
R&D toward “Access Networks—Building Trust, Connecting People”
Current and Future Research on Optical Fiber and Cables
Trends in Wireless Access Technologies toward
Expansion of Broadband and Ubiquitous Services

Regular Article
Monolithic Integration of Silicon Photonics Devices
for Telecommunications Applications

Global Standardization Activities
IPTV Interoperability Events at ITU-T

External Awards/Papers Published inTechnical Journals and Conference Proceedings
External Awards/Papers Published inTechnical Journals and Conference Proceedings

View from the Top

Motivated, Persistent, and Resolute––
Taking on the Challenges of New
Technologies and Customer Needs
with a Broad Perspective
Shinichi Yamada
Executive Vice President &Representative Director, CTO,NTT DATA CORPORATION
Overview

NTT DATA CORPORATION is known for promoting cloud computing
technology, which is now attracting considerable attention, and the further
globalization of Japanese enterprises. Wondering how top executives at thecompany with their many years of technical experience view present conditions, we asked Shinichi Yamada, Executive Vice President and Representative Director, to tell us about current business efforts at NTT DATA and therole that the company should play in society.

Combining advanced technologies and extensive
knowledge to look ahead to the future—This year marks the halfway point of NTT DATA’s
Medium-Term Management Policy. How do you
assess its progress?
NTT DATA seeks to become No. 1 in customer
satisfaction as a leading-edge innovator in line with
its Medium Term Management Policy, which targets
sales of 1.5 trillion yen in fiscal year 2012, and thegoal of becoming one of the top-five global IT (information technology) service companies. In this regard,
our efforts are achieving results, as reflected by anincrease in overseas sales, but if we turn our attention
to the Japanese market, I feel that the IT industry
itself is slightly contracting as customers become
more concerned with cost reductions. I don’t thinkthat we can simply blame the economy for our prob

lems here, but it is true that new IT investment bycustomers has not yet recovered in Japan and thateven at NTT DATA we are doing our best to justmaintain current business levels. Sometimes it feels
like we will never get back to a growth trend, but
despite these difficulties, we are getting some results
thanks to the hard work of our employees.
—What areas do you feel are contracting?
One good example is hardware, where technicalinnovation is raising performance and lowering prices. This trend toward commoditization is also happening to networks, where prices likewise seem to be
dropping every year. In the past, network scale would
inflate every time a system was upgraded, which
drove up sales. Nowadays, however, these networks
are simply being maintained, which results in a contracting environment.
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To give another example, NTT DATA has also been
involved in software development, and the developers
here have been Japanese engineers. However, once
Chinese engineers enter this field, we can expect
prices to collapse the same as they did in the manufacturing industry. This lack of IT investment andsluggish market expansion in Japan is making forsevere price competition, and even when orders arereceived, it is not uncommon for them to come withvery harsh conditions.
Expanding sales under these conditions is therefore
difficult to say the least, but nevertheless I want to set
the targets and take on the challenges of overcoming
these difficulties.
—Is there any approach that could lead to a breakthrough?
Yes, of course, and we are actually working on thisfrom many angles. One way is to lower costs such as
by expanding offshore development. And it is also
important that we not only convert our customers’
businesses to IT but also help them to expand theirbusinesses through optimal use of IT. In other words,
it is vital that we create added value and new markets.
Key tools here are cloud computing, machine-tomachine (M2M) communication, and business intelligence from a technical viewpoint and outsourcing
from a business-model viewpoint.
In terms of organization, robotics and businessintelligence are being pursued by the Robotics
Integration Promotion Office and Business Intellige­
nce Promotion Center, respectively, set up in NTT
DATA’s Research and Development Headquarters.
Today, smart grids and structure monitoring are
attracting attention as social infrastructures making
use of information and communication technology(ICT). We should think of robotics as a technologythat is essential to the construction of these social
infrastructures since it can be used to collect and analyze all kinds of information from sensor networks
and feed the analysis results back to the real world. In
other words, robotics can merge cyber space and real
space. For example, it can be used to monitor trafficand control signals and measure structural fatigue inbridges in real time and establish a repair plan. We areworking to open up this field of controlling the realworld through ICT. Of increasing importance here isbusiness intelligence as a means of analyzing andutilizing the huge amount of information obtained
from such systems and providing useful output.
I am getting good reactions to the use of robotics,
Vol. 9 No. 5 May 2011

and our employees keenly feel that we must do something. This also holds true for M2M. However, inJapan, customers often view ICT only in terms ofcost, without realizing that it can be a valuable toolfor expanding business and even for changing society. In the past, ICT was often approached in thecontext of “How can we develop it?” but from here
on, I believe that we must think of it in the context of“How can we use it to best effect?”—What are your thoughts on cloud computing?
As you know, the NTT Group is a service creationenterprise, and it is well aware that the cloud is a crucial factor in the future expansion of services.
NTT was originally involved in services that provide access to mainframe computers over the network(DRESS/DEMOS), even as far back as the Nippon
Telegraph and Telephone Public Corporation era,
which ended with its privatization in 1985. These
services themselves contracted as technical innovation brought the cost and size of computers down, but
NTT has nevertheless continued to provide shareduse systems to financial institutions. What I’m trying
to say here is that, while the technology itself maychange, our experience with the cloud model runs
deep. On the other hand, the services that NTT DATA
has long been providing have been directed toward
particular groups, and we have yet to tackle cloudservices for the general public as provided by
Amazon.
—As you have been involved with the cloud model
longer than most, you probably have some visions.
Yes, I think our experiences and know-how are very

View from the Top

valuable for NTT DATA’s efforts to expand its business in cloud computing. One idea is a cloud directed
toward a group of enterprises with common interests
as in the case of a supply chain. In short, we envision
clouds directed toward specific communities. I
believe that coordinating the needs of many stakeholders and incorporating them in services is a particular specialty of NTT DATA.
Another idea is to convert the assets of the NTT
DATA Group into a cloud platform to give us a competitive advantage. For example, NTT DATA
Intramart is the No. 1 workflow platform in Japan;
this was achieved through tie-ups with business application vendors and sales partners. In this way, NTT
DATA provides a space called an Intramart cloud, andby having our partners develop a variety of services
and applications, we can achieve a win-win-win relationship among NTT DATA, partners, and users. And
in the mainframe field, we are also converting NTT
DATA’s assets into a cloud. Migration to a cloud canbe promoted by providing a base called a COBOL*
cloud and preparing a migration path from the legacy
system to the cloud platform. In addition to the above,
NTT DATA was quick to make use of Hadoop open
source software for distributed processing of large
quantities of data. This software framework is attracting interest in the business intelligence field as a*

COBOL (common business-oriented language) is one of the oldest programming languages, but it is still widely used.

means of providing new added value to a customer’sbusiness, and we are providing it as a cloud service.
From the viewpoint of the NTT Group, however, thecloud has an additional meaning. The main role of
ICT so far has been to make the processing of business forms and exchanges with customers more efficient, but there is now a big movement toward using
ICT to achieve a better society in a variety of areas
such as medicine, education, social welfare, and traffic control in the manner of, for example, cyberphysical systems.
From here on, as this role of ICT rapidly expands,
it will become increasingly important to make application creation more efficient and make application
creation mechanisms easier to access. The cloudlooks to become a key mechanism for creating these
new applications. We have also been saying to ourcolleagues at NTT Laboratories in strategy meetings
held over the last few years that cloud computing will
become increasingly important in the years to come,and we are beginning to collaborate with them in thisregard.
—Please tell us about NTT DATA’s approach to
OSS.
There are three reasons for our involvement in open
source software (OSS).
The first reason, of course, is lower costs. Althoughhardware performance is rising as the cost of hardware is dropping, as I mentioned earlier, the cost of
software is not dropping all that much. Using OSS toconstruct software products can reduce costs below
those of using commercially available software. Thislicense-free advantage takes on even more value inthe case of cloud computing. Reducing costs, however, is not the main reason for using OSS.
The second and more important reason is to avoid
vendor lock-in. From the start, NTT DATA has advocated a multi-vendor approach and has been praisedfor doing so. Here, the use of OSS is indispensable toa truly vendor-free environment. At the same time,
we must set up our own system to support the analysis
and correction of software faults, at least for major
OSS products. Doing so will provide a number ofadvantages, including the long-term, reliable use of asystem not only for us but also for customers andlower costs over the system’s lifetime. We have beenworking with the NTT Holding Company at the NTT
Open Source Software Center on this, but I would
like to expand the scope of this collaboration.
The third reason, which is actually more of a
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secondary effect, is the training provided to NTTDATA engineers by reading and understanding thesource code themselves. The most important asset(resource) in an IT firm is its people. Open source
software represents the fruit of the skills and intellectof software developers around the world, which is
why it can progress so rapidly. Catching up in thisway or making a contribution to OSS is more usefulthan anything else for improving the skills of oursoftware engineers.
Looking forward, I would like to promote collaboration in OSS use between NTT DATA itself andoverseas companies in the NTT DATA Group.
Exploiting our strengths and advancing together—How is NTT DATA approaching globalization?
As I touched upon earlier, overseas sales havereached the 100-billion-yen level mainly throughmergers and acquisitions. The NTT DATA Groupalready has 20,000 employees working overseas. The
number of global projects is actually increasing witha focus on Japanese customers, and the opportunities
for providing consultations on global support are
increasing steadily.
To meet our customers’ expectations in this environment, I believe that we must standardize and unify
the work processes and quality level among the groupcompanies. Of course, each company has its particular forte and it would not be beneficial to overdo thisand prune off its strong points. Nevertheless, it isimportant to share the NTT DATA Way, as both
implicit and formal knowledge, among the companies so that a customer whose business spans a number of countries can feel at ease entrusting its work to
the NTT DATA Group.
My responsibilities also include offshore development companies. Our emphasis up to now has been
the provision of offshore services to Japanese firms,
but we now need to set up a mechanism for global
delivery that can perform development work at optimal locations throughout the world.
There is also a need to create solutions and productsthat can be sold on a global basis. In technology
development, we have begun to share information
about the skills, solutions, and products of each groupcompany and to pursue global research and development (R&D). The aim here is to consolidate the ideas
coming out of the various companies so that we canmove forward as the NTT DATA Group. Our global
R&D promotional base will be moving to North
Vol. 9 No. 5 May 2011

America (Silicon Valley) next fiscal year. Of course,
we will continue to cooperate with NTT Laboratoriesof the NTT Holding Company more than ever, but wewill move forward while maintaining a balance
between both approaches to R&D.
Incidentally, we have begun research in collaboration with NTT Laboratories on a high-accuracy multilingual machine translation system for automatically translating Japanese manuals and design specifications into English, Chinese, and other languages.
Needless to say, it is important that we connect
these new endeavors to results. Although we are also
tackling R&D with a view to the future, obtaining
results will be difficult unless we reassess our R&D
targets every year or even every quarter. In a world ofconstant change, I believe that it is more important toaccurately assess what is right in front of our eyes
than to look three years into the future.
Seeing the big picture—Under these circumstances, it appears that you
need the ability to change systems in response tochanges in the business world as well as foresight inresearch.
At present, no one really knows whether the projects that we are undertaking are the right projects, sohonestly speaking, it is extremely difficult to say
what viewpoint or approach is the best.
The history of IT is said to be in its infancy, but it’salready been several decades since the mainframeera, and technical innovations keep on coming. In thepast, NTT conducted multimedia experiments on an
Information Network System (INS), video-ondemand, and other new systems; today, we havereached the point where optical fiber can reach homesView from the Top

and TV can be viewed over optical fiber cables. Trials
such as these were carried out not only in Japan but
also overseas. It is said that life goes in cycles, andtrends like these can be found just about anywhere, so
if we study past cases, I think we can surmise that the
future will evolve in a similar manner and make predictions to some extent.
In this way, we pursue various types of businesswhile pondering whether we fully understand what
the customer is thinking and whether the test phases
for new products and services are advancing efficiently. To continue growing, NTT DATA must gaina foothold in new markets while efficiently constructing and operating systems in the current market. Bothare essential and achieving a balance between the two
is important.
However, it is not always possible to move forwardwith good balance between these two requirements;
there will sometimes be a bias toward one or theother, but it may not hurt to go back and forth between
these two modes of action. What is important here is
not giving up!
Moreover, advancing together as a team requires
frequent discussion. When I served as manager of the
Research and Development Headquarters, I made aneffort to set aside time to talk to employees. Everyone
would like to do the things they want to do, but that is
not always possible. That’s why talk is crucial toobjectively perceive, clarify, and share the why,
when, and what of work. In research in particular, one
tends to think in terms of what it is that one person-ally wants to accomplish, but aligning oneself withother people can broaden one’s horizons and lead togreat results. About fifteen years ago, I had the opportunity to spend two years in Silicon Valley in
California, and I noticed that the people I encountered there behaved much in this way. They conductedjoint research with the people that needed technology,
that is, with customers, and solved problems together,which I think is a great shortcut to results. Open innovation is a trendy phrase nowadays, but I would liketo see researchers approach their work in this way.

Interviewee profile
Career highlights
Shinichi Yamada entered Nippon Telegraph andTelephone Public Corporation (now NTT) in
1977. Since the founding of NTT DATACORPORATION in 1988 as a spin-off company,
he has held various positions including Directorof Business Development Sector (2004), Director
and Senior Vice President of the System Platforms
Sector (2005), and Executive Vice President of
the System Platforms Sector and Research andDevelopment Headquarters (2007). He has served
as Executive Vice President, Representative
Director, and CTO of NTT DATA CORPORATION and President of the Solutions &Technologies Company since June 2009.

NTT Technical Review

Feature Article: NTT R&D Forum 2011 Panel Discussion

Creating a Vigorous Society anda Richer Future with ICT––
Innovations in Lifestyle and Business
Coordinator:– Waichi Sekiguchi, Editorial Writer, Nikkei Inc. [1]Panelists:– Tetsuro Tomita, Executive Vice President andDirector General, Corporate Planning
Headquarters, East Japan Railway Company[2]– Kaori Sasaki, President & CEO,ewoman, Inc. [3]– Noritaka Uji, Representative Director andSenior Executive Vice President, CTO, and
CIO, NTT
Abstract

During the NTT R&D Forum 2011, a panel discussion entitled “Creating a Vigorous Society and aRicher Future with ICT” was held (ICT: information and communications technology). Noritaka Uji,
Senior Executive Vice President, participated as a panelist. This article reports on the discussion between
the coordinator and panelists.

1. Introduction

2. Presentations

Sekiguchi: I believe that we are all fully aware of
how the Internet and new information technology
called social media, such as Twitter and Facebook,gave impetus to the current movements toward
democracy that are taking place in certain Middle
Eastern countries. The challenge we face today is
how to make the most of this new technology.
Today, we intend to discuss that challenge under thetheme of “Creating a Vigorous Society and a Richer
Future with ICT” (ICT: information and communications technology). We are fortunate to have threepanelists who are eminently qualified to discuss this
topic. We will start with a brief presentation by eachpanelist and then move on to a panel discussion.

ICT as a powerful driving force for dramatic evolution of enterprises
Tomita: The railway industry has long been a leading-edge ICT industry. I’m sure you’re familiar withrailway signals. They show whether there is a train
ahead of you or whether it is safe to proceed. This isa core technology for ensuring safety. It is the culmination of a progression of painstaking efforts thathave been made since the inception of rail transportin Japan, in 1872. This is truly an ICT.
The latest example of ICT use in railway operations
is an IC (integrated circuit) ticket called Suica. [4] To
date, 33 million Suica cards have been issued. Of
these, 31 million can also be used as electronic

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Special Feature

Waichi Sekiguchi, Coordinator

Tetsuro Tomita, Panelist

Kaori Sasaki, Panelist

Noritaka Uji, Panelist

money, and some 2.3 million e-money transactions
take place every day. To ensure further developmentof Suica, we believe that it is important to achieveinteroperability with the IC tickets issued by otherrailway companies throughout Japan (Fig. 1). We arealso planning to expand Mobile Suica services, whichenable Suica functions to be used with a mobile
phone, by the summer of 2011 with a view to linking
with Android smartphones that are compatible with
Osaifu-Ketai (an electronic wallet scheme for mobile
phones [5]) so that payment for Internet shopping canbe done using Suica. The linking of Suica with
Android smartphones will enhance Suica’s capability
as a convenient payment facility for online shoppers.
We are considering exploiting ICT to create a railway system that does not rely on signals. Currently, a
train’s location is identified by sending an electric

current along the rails to create a track circuit andmeasuring the current in that circuit. Signals are thencontrolled on the basis of the identified train locations, and train operation relies on those signals. It
will soon be possible to use wireless technology,
instead of track circuits, to determine train locations.
Instructions about the running speed and direction ofeach train can be sent using wireless communication.
This will make it possible to dramatically reduce bothfacilities on the ground and maintenance costs. Theenergy consumption and overall costs of operating
the railway system can also be reduced and safety
will probably be further enhanced. We want toachieve a breakthrough in railway operation by using
such technologies.

Vol. 9 No. 5 May 2011Special Feature

Suica - Operations Strategy -Raiway usage
JR East area
Increasing usage rate in Tokyo metropolitan area(fiscal 2011 Suica/PASMO usage rate of 90%)
Enabling use on all railway lines

Railway usage

Outside area
Expand mutual-use metwork(Sapporo, Fukuoka areas)
e-money
e-money
Establish as No.1 e-money
Spread nationwide
Increase tie-up partners
Increase compatible stores

Establish as third pillar of operations(fiscal 2011 target)
8 million transactions daily
800

Increase tie-up partners
Convenience stores
Supermarkets
Taxis
Airlines

New information business400
Use as marketing data
0
PASMO: IC card scheme for non-JR railway lines
http://www.pasmo.co.jp/en/

Mar. 2008

Mar. 2011
From JR East 2020 Vision – i do mu

Fig. 1. Suica—Operations strategy.

Opportunities for people to learn various viewpoints
Sasaki: In 2000, we created a website called ewoman, which serves as an information hub. We believethat ICT is not just about convenience but about helping people to develop. The Internet is more than a toolfor disseminating information; it’s a tool for building
a knowledge database. Users can search the databasefor information and consider how to make appropriate use of the obtained information. For example, theewoman site provides ewoman’s online roundtablediscussion. This is not a bulletin board for posting
information; there is a chairperson to coordinate afour-day discussion in each round table, and theresulting information is rearranged for readers. Users
can access past discussions in order to learn about the
subject matter discussed from various perspectives.
To make the database really useful for readers, wehave introduced what we call the I-statement rule.
Participants must limit their statements to mattersthat directly concern them. In other words, instead ofpresenting general statements, they are required to
discuss their own specific views and experiences. The
intention is to eliminate hearsay and generalized discussions and to enable readers to understand a rangeof perspectives. I believe that forums of this type will
be necessary in the coming age of diversity. We cancreate new value by integrating technology andknowledge.
What can we do with ICT? How should we use it?
It is important that ICT goes beyond merely providing convenience; it must enable people to learn andgrow. To create a true knowledge database, it isimportant to ensure interactivity and encourage participants to think in the first person. It is not enoughthat people can access the database. The databaseshould enable them to broaden their options, makelife more fulfilling, and enhance their sense of ethics.
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ICT supports socio-economic growth, resolutionof social problems, and pursuit of fulfilling lives
Uji: In this forum, a variety of ways of exploiting thelatest technology are being exhibited. Let me talkabout our fundamental approach to ICT.
We think that ICT is a cord linking different segments of society, industries, and organizations. For
example, in an enterprise, ICT links different
departments, such as sales, development, and generalaffairs. It also links different industries, or different
ministries and agencies of the national government. It
plays the role of holding things together. Linking different segments can enhance productivity and expedite transactions in business, for example. As we facevarious social issues, such as the declining birthrate
and aging society, we urgently need to make full useof ICT in the fields of medical care, education, andadministrative services in order to enhance the quality of these services. In this way, ICT can contributeto economic growth and the resolution of social problems. Another role for ICT is making possible a variety of lifestyles. We believe that ICT can support
fulfilling lives by making it possible to strengthen thebonds within families and within communities(Fig. 2).
The latest keywords these days are clouds andsmartphones. For example, studies are underway on
a collaboration model whereby video coverage ofwork being conducted in the field can be recorded ona smartphone and sent to a remote office, which canthen give visually oriented instructions to workers in
the field in real time. This could dramatically enhance
work efficiency. A new mechanism can be developed
whereby a cloud manages smartphones in such a waythat losing your phone is not longer a major inconvenience. The previous panelist talked about a knowledge database. I believe that the accumulation oflarge volumes of data in clouds can lead to the creation of new value for society.
Need for an ICT policy that emphasizes better useof information
Sekiguchi: As mentioned by one of our panelists, itwill become common for terminals, such as tablet
terminals, to be connected to clouds. The user willstore his or her data in clouds and access the clouds toretrieve data via any available terminal. The advent ofclouds and smartphones is making such a lifestylepossible. The time is coming when data clouds will
be provided as a utility service like electricity, gas,
and water. Faced with this prospect, people areexpressing concern about how to ensure security andVol. 9 No. 5 May 2011privacy. We need to ask ourselves how we should deal
with these issues.
If we pause to look around, we can observe manychanges taking place in the world, and we realize inwhat respects Japan is lagging behind. I think that
there are three stumbling blocks that may impair ourability to achieve innovation.
The first of these is what some Japanese refer to as
the Galapagosization of Japan, meaning that certain
technologies used in Japan are unique, like the species whose habitat is confined to the Galapagos
Islands, so they can never become global standards. It
is true that Japan has had many good technologies.
However, that is meaningless unless they are actuallyused. If our technologies are not well accepted globally, we will never get past a sense of being somewhat
isolated.
The second stumbling block is people’s general
misgivings regarding the protection of personal information. To fully exploit information technology forthe benefit of people’s lives, we must have a common
infrastructure. The idea of assigning an ID (identity
number) to every Japanese citizen has never advanced
beyond the discussion stage. I believe that Japanurgently needs to put this idea into practice.
Third is the tendency to demand excessive protection of copyrights. It is, of course, important to protect intellectual property rights, but I believe that we
now need to adopt an ICT policy that places moreemphasis on enabling people to better use copyrighted information than on rigorously protecting copyrights.
3. Discussion
How to promote globalization of Japan’s technologies and services
Sekiguchi: At this point, I would like to ask the panelists to discuss what type of information society weshould aim at creating. Although I think that Suica is
an excellent technology, when I go abroad, I findcompletely different systems in use. Suica would
seem to be one of those Galapagos species. Do you
have a strategy for expanding its application overseas
and, if so, could you share it with us?
Tomita: Now that Suica is well accepted in Japan, weare exploring ways to expand its use overseas. However, there are a couple of issues to consider.
The first is the data transmission speed. Commuters
in Japan walk very fast. They pass through a ticket
gate at about 1.5 m/s, probably the fastest rate in theworld. Therefore, the Suica system must also operateSpecial Feature

NTT’s understanding of the role of ICT

ICT as a cord linking segments of society, industries, and organizations
Utilization of
information

Globalization

Global warming• Enhance productivity in business.
• Expand global business.
• Enhance quality of medical care, education,
and administrative services.
• Reduce impacts on the environment.

Declining birthrate andaging of society

Swift decision making

ICT can support economic growth
and the resolution of social issues.

ICT as a means to enable a variety of lifestyles

Value-based
consumption

Increased
free time• Attractive entertainment• Life of comfort and convenience• Stronger bonds with family andcommunity

Shallow
relationships

Diversity insense of value

ICT can support fulfilling lives.

Fig. 2. NTT’s understanding of the role of ICT.

very fast. It both reads and writes data in less than 200
ms. In Europe and the USA, such high-speed operation would be regarded as over-specification.
The second issue is reliability. Suica ensures system
reliability by storing data in three different places—inthe central equipment, in the ticket gate machine, andin the Suica card—so that any lost data can be foundin a backup. Potential customers overseas regard suchan intensive backup system as unnecessary.


Even where we have an excellent technology inJapan, when we attempt to transfer it to another country, we need to examine whether or not the technology
is appropriate for the specific situation of the target
country. I often feel that we should not be complacent
about having an excellent system.
Sekiguchi: I think that we should make greater
efforts to have Japanese technology accepted globally
as a de facto standard. What do you think?
NTT Technical Review

Special Feature

Suica - Mobile Suica Service -Million users
2.4

2
1.8
1.6

MobileSuica
2.22 million users(as of November 1, 2010)

1.4

October 1, 2006
• Can be charged via
regular credit cards• Increase in types oftickets and season tickets

1.2
1
0.8
0.6
0.4

March 13, 2010
Automatic mobile Suica
charging service starts.

October 21, 2006
• Start of online payment service• Charging via bank account• Start of Easy Mobile Suica

2.2

January 28, 2006
Start of Mobile Suica
services(NTT DoCoMo and au)• Charged via communication• Display of use history• Mobile green charge

Start of Mobile Suica service
for Android smartphones
compatible with Osaifu-Keitai service
from first half of fiscal 2011
March 15, 2008
Mobile Suica Limited
Express ticket service
launched

March 18, 2007
Reciprocal use of Suica with
Pasmo IC cards in the Tokyo
metropolitan area begins.
December 2, 2006
Softbank Mobile
supports Suica

0.2
0Jan. 2006

Jan. 2007

Jan. 2008

Jan. 2009

Jan. 2010

From JR East 2020 Vision – i do mu

Fig. 3. Suica—Mobile Suica Service.

Tomita: We should not be the only ones to bear theburden of those efforts. We cannot make any progressin that direction unless the whole country becomesinvolved in thinking about how we should develop
smartcards and the systems that use them. Unfortunately, there seems to be a gap in perception between
Japan and other countries about the value of the convenience provided by smartcards. How to bridge that
gap is another difficult issue. However, I believe that,by linking the Suica system with smartphones(Fig. 3), you can develop cards and terminals that aresuitably tuned to individual users’ needs. Provision ofsuch sophisticated services can create new value.
Uji: I think it is great that Suica is built into a mobile
terminal and enables user identification to be used insetting up communication. Initially, a single smartcard cost about 10,000 yen. Over time, the price has
dropped dramatically. That is also great. The smartcard used to authenticate a cigarette vending machineVol. 9 No. 5 May 2011user has fewer functions than other smartcards
because it was paramount to reduce the price of thistype of card. The capabilities built into a smartcard
should be closely linked to how and where it is to be
used. It is necessary to consider whether there isgreater demand for less expensive cards or for highly
secure cards. A highly sophisticated card cannot be apanacea for all needs.
Sasaki: I recall a conversation that I had with somelocal people during a recent visit to Switzerland. I
showed them how my mobile phone receives information about what time my son passed through which
exit of which station because he used his student
commuter pass smartcard at a ticket gate. Their reactions surprised me. “What are you doing?” “That’s
wrong.” When I raised the issue of children’s safetyin public places, they responded: “Your way of thinking is wrong.” We then had a lengthy discussion.
This demonstrates that service needs vary dependSpecial Feature

ing on the specific environment and sense of values.
What is required of a system can vary depending onwhether you are targeting only the Japanese domestic
market or aiming for global market acceptance.
Sekiguchi: I agree that, while technology may beglobal in nature, the services that people want will
have a very local character. So, it would seem that thequestion we need to consider is how to intelligently
balance the global and local aspects of a particulartechnological offering.
Use of social media in enterprises
Sekiguchi: As I noted at the outset, we are witnessing
a surge in the use of social media. However, in Japan,
enterprises in particular seem to take these media
channels with a grain of salt. What’s your perception?
Sasaki: I think that the potential power of individuals
being able to speak out is clearly an extraordinary
development, as evidenced by events in the Middle
East. Previously, a person’s opinion travelled slowly.
Today, individuals access the Internet to post a variety
of information from wherever they happen to be.
Social network services (SNSs) on the Internet, forexample, have developed into powerful tools. What is
important in this Internet era is that individuals havea sense of ethics, a sense of responsibility in expressing their opinions, information literacy, and the ability to use and combine information.
Japanese enterprises are not even ready to experiment with SNSs. They are still watching these systems from a distance with suspicious eyes. Some
enterprises are reluctant to set up inquiry links ontheir websites. The moment some of them did, theyreceived a flood of complaints and had to shut down
the links because they could not deal with the volume.
I suspect that, if enterprises feel threatened by thenotion of setting up inquiry links, they simply
wouldn’t know what to do if their employees were to
begin speaking out via an SNS.
What enterprises should do is enhance employee
satisfaction and train their people in public relations
and communications so that they can serve as company spokespersons. Instead of restricting theiremployees’ opportunities to speak out, enterprises
would do better and enjoy enhanced brand perception
if they were to train their employees to become good
publicists.
Sekiguchi: A case in point is what happens when atrain service is resumed after a period of temporary
service suspension. It is Twitter users who transmit,
ahead of all other media, the news that the trains arerunning again. Leaving aside the matter of whether or
not such information is accurate, social media transmit information earlier than any official service. How
does JR East deal with this issue?
Tomita: This is a major issue. In principle, information about an accident or delay should be disseminated through the mass media. If we do not notify
reporters in the mainstream press first, our good relations with them will suffer. So, we must be carefulwhen issuing information. Although the idea you
mention is one possible way of sending information,
it involves a difficult problem.
It is true that social media can transmit information
faster. They can be effective tools. JR East has some
60,000 employees. A social network could be effective for mutual communication and exchange of
information between employees.
Sekiguchi: What is the position of the ICT service
provider on this issue?
Uji: Although we are a provider of ICT services, weare also users of these services. So, let me speak fromthe user perspective. NTT DATA has a web page fordisseminating internal information. It also operates
an internal social media mechanism through which
employees can communicate freely across different
departments and across different ranks. The mechanism is used effectively to communicate employees’
opinions about understanding user needs and to provide mutual support.
NTT Laboratories also has an SNS called chie-nowa, which operates across the boundaries between
organizations within the Laboratories. It is very useful for exchanging technical information and unearthing new ideas.
In addition, employees in the Public Relations
Department of NTT Holding Company are tweetingfor the public. This is highly rated as a new approach
to public relations.
The NTT Group has some 200,000 employees andthe number of overseas employees will increase. We
will need to study, on the fly, how to use social
networks while also seeking to ensure compliance.
How to deal with privacy and security in the age ofhigh utilization of information
Sekiguchi: The technology research company Gartner conducts an annual survey of chief information
officers (CIOs). It asks them to define the mostimportant issue for their respective companies.
Responses naturally include such considerations ascost reduction, improved efficiency in the supply
chain, and quick decision-making, but the one that is
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Special Feature

attracting growing attention is greater use of social
media. CIOs are increasingly concerned about how tofacilitate information exchange with customers,
employees, and other stakeholders.
However, if we look at what is happening in the
Middle East and at the WikiLeaks story, we can seethat efforts to facilitate communication are, in a way,
rebounding on those who have promoted such efforts.
Even though you might have completely protected
yourself against external attacks, you may not havetaken sufficient measures to prevent information
leakage from the inside. While the sharing of information is important, I think it is necessary to control
information wisely. What do you think?
Tomita: That is an issue that we need to address seriously. JR East currently has some 100 companies in
its group. Each company has its own website and its
own system for exchanging information over theInternet. We have begun to check the levels of security and information management of these systems.
We are exhaustively checking whether adequate
defensive steps are being taken to protect servers andterminals against not only attacks from outside thecompany but also information leakage from theinside and whether or not logs are kept.
Sekiguchi: While system developers need to take thisissue seriously, I think that each employee or eachindividual should also ensure that he or she takes
measures to prevent his/her personal informationfrom being disclosed in an undesirable manner.
Sasaki: When I read the blogs or twitters of wellknown figures, I am puzzled when they write “I’m on
the platform of such and such station” or “I am going
into the restaurant of such and such hotel.” Are they
inviting people to come over or informing people that
here is a chance to attack them? I am always careful
to avoid risk when I tweet.
Today, with so many people able to post information and access each other’s information, it is necessary to enhance users’ behavior and their ability tojudge what is confidential and whom they need toprotect in addition to implementing advanced security technology. Risk management and security education for users is just as important as security technology.
Security policy that considers active utilization of
information
Sekiguchi: Japanese companies tend to treat all kindsof information as confidential or classified. This
results in a situation where you can no longer tellwhich information really is sensitive.
Vol. 9 No. 5 May 2011

Uji: The higher the barrier to information access, theharder it is to make good use of that information andensure that it is widely used. On the other hand, if
access to information is not controlled at all, there isa risk of information leakage. I think that it is the roleof enterprise security policies to clarify these issues.
We have established a security policy and provided
tools and a mechanism for implementing the policy,
such as requiring employees to hold their employee
ID cards close to a contactless card reader, whichreads the IC in the card, when they start up their personal computers in the office and classifying information in terms of the required security level. While
we undertake research and development of technologies to enhance information security, our recognition
that it is important to classify information has led toestablishment of the security policy.
While it is necessary to protect the confidentialityof information, it is also important to promote active
use of information. For example, an NTT Group
company provides an online question answering service called Oshiete, goo!. When someone submits aquestion on this website, he or she gets answers. As
people discover the convenience of this service, thenumber of users is increasing and more and more
information is being accumulated, creating a virtuous
cycle. This is indeed a database of knowledge. I thinkthat the provision of such a service represents thecloud concept in its broadest sense. The time hascome for us to benefit from such convenient services.
Technology has come a long way.
Sekiguchi: So, the two mainstays are construction ofwatertight systems and establishment of a watertightsecurity policy. Even so, problems can occur. Therecan be pitfalls anywhere in the information society.
This is a risk management issue. Given the security
and privacy issues that we are faced with, how can webuild a trouble-free system?
Uji: I believe that mechanisms in which appropriate
security and privacy measures are implemented will
increasingly find their ways into enterprises andeveryday living. For example, service characteristics
required in the medical, educational, and administrative fields vary from service to service. Some services
can be provided on a best-effort basis. Some require
rigorous authentication of users. Some cannot tolerate temporary service interruption. The NTT Grouphas declared that it will provide clouds that serve as
safe and secure social infrastructures. In this respect,
I believe that we must broaden their utilization inservices of the Next Generation Network (NGN),
which combines the convenience of the Internet withSpecial Feature

ICT innovation as a driving force for growth of Japan and the world

Resolution ofsocial issues

Socio-economic
growthRealization ofa fulfilling life

Accelerated service creation
Evolution of mobile services
and fixed mobile convergence

Global activities

ICT innovations
Smartphones, clouds, smart communities,
high-reality video delivery, Home ICT,
visual communication,…

Fig. 4. ICT innovation as a driving force for growth of Japan and the world.

the reliability of the telephone network.
Need for interpreters to facilitate communication
Sasaki: I think that we now need interpreters tofacilitate communication between those who know
systems and those who know business processes.
While we want to hear feedback from users, wesometimes fail to understand what they are tellingus.
Here’s an interesting anecdote. When female users
said that they wanted a cuter product, the developer
assumed that they meant the product should be pink.
In fact, to the women, something cute meant a product with rounded edges. Enterprises need to recognize that proper interpretation is very important.
Now that it’s so easy for individuals to post information, as in the case of SNSs, media training for
consumers is also important. Our company provides
media training to enterprise executives. It will also
become necessary to provide media training toemployees so that they can communicate their business processes and advanced technologies in a manner that users find easy to understand and so that they
can determine for themselves what information is
confidential.
Sekiguchi: My daughter tends to describe almost
anything she likes as cute. I guess I need to be more
careful to determine whether she means the shape orthe color. This anecdote could apply to how weshould write and read purchase specifications. It is
important to understand what the users really mean.
Future ICT innovation
Sekiguchi: What measures should enterprises take inthe near future?
Tomita: I think that the safety levels of systems inJapan are relatively high because we have learned
from the experiences of various incidents. In the railway world, safety means that trains stop immediately
whenever a problem occurs. Railway operation is a
fail-safe system. The system design is aimed at ensuring safety without fail. However, since even this levelof safety does not necessarily satisfy our customers,
we need to aim higher.
Corporate executives need to further raise their ICT
literacy. There have been cases where good proposals
were not adopted by corporate executives simply
because they were poorly presented. I want ICT engineers to explain their technologies in a more easily
understandable manner.
Uji: When a new service is to be introduced, those
who actually use it, those who know the required
business processes, and those who develop the service need to collaborate with each other. Systemproviders should not stop at explaining what can bedone or what a thing means technically; they need to
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Special Feature

continue to exchange opinions with actual users.
Right now, broadband networks are ready to be
used by 99% of the Japanese population, but Japan islagging behind internationally in active utilization of
ICT.
Through ICT innovations, including the creation ofclouds and other services, fixed mobile convergence,and global ICT activities, we are aiming to help
achieve socio-economic growth, resolve social problems, and realize fulfilling lives (Fig. 4).
Sekiguchi: Today, we have heard some valuable
insights from our three panelists regarding our stanceon ICT, policy issues, system design issues, andoperational issues. The world of ICT is steadily
advancing, and information innovations are constantly emerging. There is no such thing as enough. We
have learned that there is virtually no end to the security and other measures we need to take because newtechnologies always arise. I hope that our audiencehas found today’s discussions useful. In declaring thesession closed, I would ask the audience to give ourthree distinguished panelists a big round of
applause.
References
[1]
[2]
[3]
[4]
[5]

Nikkei Inc.
http://www.nikkei.co.jp/nikkeiinfo/english/index.html
East Japan Railway Company.
http://www.jreast.co.jp/e/index.html
ewoman, Inc.
http://www.ewoman.co.jp/2005_about/english/
Suica.
http://www.jreast.co.jp/e/pass/suica.html
Osaifu-Keitai.
http://www.nttdocomo.co.jp/english/service/convenience/osaifu/

Vol. 9 No. 5 May 2011

Profiles of the coordinator and panelists
Waichi Sekiguchi
Editorial Writer, Nikkei Inc. [1]Serves as a member of the ICT Policy Task
Force of the Ministry of Internal Affairs andCommunications and also sits on the Council on
Computerization of School Education of the Ministry of Education, Culture, Sports, Science andTechnology.
Tetsuro Tomita
Executive Vice President and Director Generalof the Corporate Planning Headquarters, East
Japan Railway Company [2]Previous positions include Manager of the General Corporate Planning Headquarters and Director of the Life-style Business Development Headquarters.
Kaori Sasaki
President & CEO, ewoman, Inc. [3]Serves as a member of the Government’s IT
Strategy Headquarters and is also on the Legislative Council of the Ministry of Justice.
* The photographs and materials of the coordinator and panelists are used in this article bypermission of the persons concerned. It is strictly
prohibited to reproduce, reprint, or disclose to
any third party the photos and materials includedin this article without permission.

10

Feature Articles: NTT Tsukuba Forum 2010 Workshop Lectures

R&D toward “Access Networks––
Building Trust, Connecting People”
Yukio Akiyama†
Abstract

Researchers at NTT Access Network Service Systems Laboratories areengaged in research and development of the access network under thetheme of building trust and connecting people. This article describes thecurrent state of the access network and associated issues and introduces
the five main approaches at NTT Access Network Service Systems Laboratories. The Feature Articles in this month’s issue are based on lectures
given at the NTT Tsukuba Forum 2010 workshop held on October 21,
2010.

1. R&D at NTT Access Network
Service Systems Laboratories
At NTT Access Network Service Systems Laboratories, we are involved in the following four fields ofresearch and development (R&D):(1)	Optical access network technology to provide
high-speed, diverse, and inexpensive communication services by optical access(2)	Wireless access technology to provide highspeed, broadband, and seamless communication
services to diverse locations and areas by wireless access(3)	Media network technology to achieve an economical access network, rapid service provision, and efficient operation of facilities(4)	Infrastructure technology to achieve long-lasting and efficient use of primary communication
facilities such as conduits and manholes
In short, NTT Access Network Service Systems
Laboratories deals with a wide array of technologies
for making connections from NTT central offices tousers’ households.

† NTT Access Network Service Systems Laboratories
Yokosuka-shi, 239-0847 Japan

2. Trends surrounding the access system
As of the end of June 2010, the number of subscribers to broadband services in Japan had risen to33,550,000. Among these, subscribers to fiber-to-thehome (FTTH) access accounted for 18,570,000 or
55% of the total. In terms of national broadband penetration (total number of subscribers divided by population of the country), these figures mean that Japan
comes in second behind Korea, but in terms of total
number of subscribers, they indicate that Japan occupies first place, far ahead of other countries, reflecting
its commitment to increasing the penetration of
FTTH and being a world leader in this field.
Within the NTT Group, the number of FTTH subscribers as of the end of June 2010 came to 13,840,000
for NTT EAST and NTT WEST combined. This figure is forecast to exceed 15 million by the end of fiscal year 2010. Needless to say, the NTT Group is notjust aiming to increase the number of subscribers—itis also working to increase high-speed and advanced
services so that even better products can be provided.
When they were first deployed, FTTH services had amaximum transmission speed of only 10 Mbit/s.
Now, up to 100 Mbit/s is normal, and since 2009,services with a maximum transmission speed of 200
Mbit/s or even 1 Gbit/s have been available.
It is also important for social issues such as the
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Feature Articles

aging society and changes in the global environment
to taken into account when new technology for theaccess network is being developed.
An aging society means a decrease in the working
population. Japan’s workforce in 2010 made up
63.9% of the population, but from here on, it isexpected to drop by 5 points every 20 years. NTT is
not exempt from this problem: the aging of its
employees is also a major issue. For NTT, this makes
it all the more urgent to develop do-it-yourself (DIY)
facilities, simplify installation work, and make maintenance work more efficient.
At present, the amount of human-induced CO2 discharge is more than double the amount that can benaturally absorbed. The effects of global warming
such as rising sea levels and desertification are ofserious concern, prompting NTT to actively promotemeasures to protect the environment. Access-systemequipment and components are used in the section up
to the user’s home and even inside the home, and in
addition to being deployed in great quantities, theytend to be quite diverse in makeup in line with thediversification of services. Reducing the power andresource consumption of these products can therefore
have a major effect toward preserving the environment.
3. Access network R&D activities
On the basis of the following external trends, NTT
Access Network Service Systems Laboratories is taking up the following challenges in developing technology for the access network:•	Provide cheaper and more convenient broadband
services to more people•	Make operations more efficient and skill-free as
highly skillful personnel retire and the labor poolshrinks•	Incorporate measures to protect the global environment and reduce CO2 emissions•	Disseminate and support technology and form
partnerships to help accelerate the deployment of
FTTH overseas
To achieve the above, we are undertaking five specific measures, which are discussed below: constructing a high-reliability and economical network, creating new network services, expanding the broadband
service area, promoting green R&D, and expanding
globally.

Vol. 9 No. 5 May 2011

3.1 C
 onstructing a highly reliable and economical
network
To reduce capital expenditure (CAPEX), we areworking to optimize aggregation appropriate to user
dispersion, construct facilities applicable to rural
areas, promote the use of existing facilities, and simplify the work of installing new circuits and deploying new services. We are also working to reduce
operating expenditure (OPEX) in relation to maintenance/operations and fault repair. Here, to supplement operations support technology based on existing operations systems, our plan is to simplify installation work through DIY facilities and skill-free procedures and introduce technology like remote fault
troubleshooting and remote switching to make maintenance operations even more efficient. At the sametime, we are working to make network facilities morereliable and to achieve long-life infrastructure facilities. The three technologies described below reflect
these expenditure-reducing efforts.
(1)	Small-diameter, low-friction indoor optical fibercable
To promote the provision of optical services in
multi-dwelling units and especially in existing structures, it became necessary to lay many cables using
the spare space in existing conduits that alreadyhouse telephone cables. In response to this need, wedeveloped a small-diameter, low-friction indoor optical fiber cable having half the cross-sectional area
and one-fifth the dynamic friction coefficient of existing products. More than 20 of these new cables can be
deployed in the free space in existing conduits compared with only a few cables of the current type.
Thus, optical services that could not be provided in
the past owing to insufficient space in conduits can
now be offered. This newly developed cable was also
given an optimal amount of bending rigidity so that it
could be installed in the conduit using the push-in
method instead of the conventional pulling method
using a pulling wire. The end result was a reduction
in cable deployment time.
(2)	Optical-media maintenance and operations
technology (traffic monitoring tool)
We developed a traffic monitoring tool for monitoring signals from an optical network unit (ONU) anddisplaying service status. This tool enables on-site
personnel to check the link status between opticalfibers and an ONU. With this tool, the user’s usage
conditions can be checked in real time and the media
access control (MAC) address can be verified whenfibers are switched to ensure that the user has beenconnected. This prevents erroneous cutoffs orFeature Articles

ITU-T/FSAN: Standardization of next-generation 10G-class optical access system (XGPON) completed (2010). Discussion of next next-generation optical access system (NGPON2) begun.
IEEE: Basic interface specifications for 10G-EPON completed. Standardization of system
specifications toward interoperability proceeds (SIEPON).
Standardization trends for Ethernet and optical access systems
Now
100 Gbit/s
10GbE

Bit rate

10 Gbit/s
1GbE

1 Gbit/s

G-PON

100GbE
NG-PON2 (scheduled for 2015 and beyond)
40GbE
SIEPON
Next next-generation
10G-EPON(scheduled for 2012) optical access system
XG-PON

GE-PON
100BASE-T

100 Mbit/s

10 Mbit/s
1990

Next-generation
optical access system

Current system
IEEE Ethernet
IEEE PON
ITU-T PON

B-PON
10BASE-T
2000

2010

2020

FSAN: Full Service Access Network
ITU-T: International Telecommunication Union, Telecommunication Standardization Sector

Fig. 1. Progress and standardization of optical access systems.

connections in fiber switching activities while also
reducing installation time.
(3) Operations visualization technology
This technology aims to make operations more
efficient and improve security by systematizing business know-how possessed by individual employees.
This know-how can be extracted from work logs thatrecord the daily actions of operators and accumulated
in a database so that it can be reflected in future
operations. We can compare this approach to a highperformance car navigation system that uses a recordof routes travelled by veteran drivers to advise novice
drivers which roads to take or to guide a driver alongan optimal route by means of an auto-cruise (autopilot) function.
Although this function could have been achieved in
the past by embedding it in the system, the advantageof this technology is that information from work logs
can be collected without having to revamp the base
operations system. In this way, we aim to achieve
functions such as automatic execution of routine
operations, operation navigation, and controls on
certain operations.



3.2 Creating new network services
NTT Access Network Service Systems Laboratories is researching and developing a high-reliability,next-generation access network to promote the creation of new network services.
3.2.1 10G-EPON
The demand for a faster optical access network is
growing as broadband services spread and the Next
Generation Network (NGN) expands.
The standardization of optical access systems tends
to lag behind the Ethernet standardization process bya few years (Fig. 1). The GE-PON (Gigabit Ethernet
passive optical network) optical access system, whichis the one now in use, was standardized in 2004, while
specifications for the physical layer and data-linklayer of 10G-EPON (10-Gbit/s Ethernet PON) werestandardized in 2009. In addition, discussions on NGPON2 as the next next-generation optical accesssystem providing several tens of gigabits per second
have already begun.
At present, work is proceeding on standardizing
interoperability between GE-PON and 10G-EPON at
the system and network levels. Coexistence with thecurrent GE-PON system is essential to the adoption
and expansion of 10G-EPON. We are studying a
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Feature Articles

NTT is researching and developing technology to provide a diverse lineup of accessnetworks toward broadband service area expansion.

Creation of new network services
10G-EPON system
Carrier-grade
Ethernet technology
Video communications
network
High-speed,
broadband technology(WDM access)

Expansion of service area
PWR
(wireless local
area network)

PON extender

Train Internet
Wide-area
ubiquitous network(sensor network)

WDM: wavelength division multiplexing

Fig. 2. R&D for expansion of broadband service area.

system that has a 1G-10G dual-rate optical line terminal (OLT) to accommodate GE-PON ONUs (1G
upstream, 1G downstream) and 10G-EPON ONUs
(1G or 10G upstream, 10G downstream) connected tothe same splitter. Such interoperability will enable
users who desire faster speeds to migrate to newservices smoothly.
3.2.2 Carrier-grade Ethernet technology
To achieve high reliability, maintainability, andoperability, we are developing the following three
network technologies as well as an operations systemthat can implement those technologies and applying
them to commercial services (NTT’s Business Ether
Wide).
(1)	Ethernet OAM technology: Generates maintenance signals in communication circuits so thatfaults can be discovered in real time and troubleshooting performed immediately (OAM: operations, administration, and maintenance).
(2)	Ethernet ring protection technology: Prevents
collisions from occurring during ring-switchingat the time of a fault in a ring-based network.
(3)	Redundant access technology: Duplicates circuits in the access interval and performs highspeed switching at the time of a fault to improvereliability.
3.3 Expanding the broadband service area
NTT Access Network Service Systems Laboratories is working to expand the broadband service areaby providing a diverse lineup of access networks.
Vol. 9 No. 5 May 2011

There are many technologies that can link the creation of new network services with the expansion of
the service area (Fig. 2).
3.3.1 Optical-amplification PON repeater(PON extender)
The maximum transmission distance of the current
PON system is 20 km, which means that some sort ofdistance-extending technology is needed to provide
services to rural areas. In response to this need, weare developing a PON repeater to achieve wide-area
service coverage (with long-distance, multi-branching capabilities) through optical amplification. This
repeater can be installed outdoors on poles so thattransmission distances can be increased in rural areas
and the number of branches and accommodated
ONUs can be increased in urban areas.
3.3.2 Wireless technology
A personal wireless router (PWR) will enable avariety of devices equipped with wireless local area
network functions to be automatically connected tothe most optimal network (3G, Wi-Fi, optical access,etc.) without user intervention.
A wide-area ubiquitous network (sensor network)
will make possible services for automatically collecting information over a wide area by attaching wireless terminals to all kinds of things. Various service
concepts are now being studied: one application
would be to enable gas and electricity meters to beread wirelessly from an office instead of visually by aperson in the field.

Feature Articles

Example: Reduction in use of asphalt through cable-conduit repair technologies
Cable conduits can be repaired and new space for cables secured by only manhole operations.
Asphalt paving materials for road restoration become unnecessary, which reduces the environmental loadby saving resources and reducing CO2 emissions.

Cable-conduit high-pressure washing technology

3000-core optical fiber accommodation type

Rust, sand, dirt

Supports both straight and curved
sections of conduit
Easily assembled structure
Push inJoint
mating skirt
Main
Defective
mating skirt
conduit
Lining material

Metal conduit

Cable

Cable-conduit renovation technology

High-pressure
washing machine

Existing cableSpace-securing typeHigh-pressure
washing machine

Spraying

Supports both straight and curved sections of conduit(controls crimps, etc.)
Work at curved intervals does not affect existing cable.

Fig. 3. Resource-saving technologies.

3.4 Promoting green R&D
3.4.1 Activities toward preserving the global
environment
At NTT Access Network Service Systems Laboratories, our R&D efforts follow the “NTT Group
Energy Efficiency Guidelines” conforming to the“ICT Ecology Guidelines” established by the Telecommunications Carriers Association (ICT:
information and communications technology). We
are working to reduce power consumption in accessnetwork equipment by steering our long-term
research in the following three directions.
- Reduce power in devices and components-	Reduce power through a method/systemapproach-	Reduce power through a network-architecture
approach
We are also developing cable-conduit repair technology, design technology for concrete poles, and opticalsplitter compact housing technology to save resources
including recycling access-network facilities.


3.4.2 P ower-savings technology for PON systems
To reduce power consumption in the access network, we are researching the application of mechanisms like automobile idle-stop systems to PON systems. A sleep function will deactivate some ONU
functions according to current operating conditions
and a link-rate switching function will switch the linkrate between OLT and ONU according to current traffic conditions. Achieving these mechanisms will
require protocol for controlling communications
between the OLT and ONU, and standardization
activities to this end are proceeding.
3.4.3 Resource savings by cable-conduit repair
technologies
These technologies make it possible to repair cableconduits though operations performed only in a manhole. This enables conduits to be reused while also
reducing the use of asphalt conventionally required in
cable-conduit excavation work and cutting down on
earth, sand, and other waste (Fig. 3). Cable-conduit
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Feature Articles

NTT is building relationships with overseas carriers through internship programs.
It is focusing on the Asia region with an emphasis on Southeast Asia

Hong Kong
GE-PON adopted by PCCW
India
Held FTTH technology seminar

Taiwan
GE-PON adopted by Chunghwa
Telecom

Thailand
GE-PON adopted by TOT
Held NGN technology seminar
Held joint studies on NGN with carrier

Philippines
GE-PON adopted by PLDT
Held joint studies on NGN and
optical access with carrier

Malaysia
Received OJT optical access for
carrier personnel

Singapore
Held NGN and FTTH technology
seminarsSouth Africa
GE-PON adopted by GTS

VietnamConducted joint trials and joint business
operations on optical access with
VNPT Hanoi (GE-PON adopted)
Held joint studies on NGN with carrier
Received OJT for optical access for
carrier personnel
Indonesia
Received OJT for optical access and
NGN for carrier personnel
Held joint studies on NGN with carrier
Held NGN and FTTH technology
seminars

OJT: on-the-job training

Fig. 4. Relationship building with overseas carriers.

high-pressure washing technology removes rust anddirt inside a conduit by high-pressure washing without requiring the cable to be pulled out. Cable-conduit renovation technology secures space for accommodating additional cables by inserting lining
material inside a conduit after it has been washed.
Up to now, the repair of a degraded conduit required
excavation of the road surface, backfilling after
completion of the repair, and the application of a newasphalt coating. Our new no-dig technologies, however, eliminate the need for roadwork to excavate andrepair conduit cables. Once these technologies are
fully implemented, the use of asphalt paving materials is forecast to drop by about 300,000 tons over a
five-year period.
3.5 Expanding globally
To become more competitive on the world stage,
NTT is actively promoting its researched and developed technologies and their products to a number ofcountries overseas. It is also involved in international
Vol. 9 No. 5 May 2011

standardization activities and relationship building
with an eye to expanding business on a global scale.
Three specific R&D achievements of NTT AccessNetwork Service Systems Laboratories are contributing to the global expansion of the Japanese ICT
industry.
(1)	Free-bending optical fiber cord and small-diameter, low-friction indoor optical fiber cable:
NTT was the first in the world to commercialize
these products, which are now being sold overseas by Japanese manufacturers.
(2)	Optical connectors: These have been internationally standardized (by IEC: International
Electrotechnical Commission) and hold a world
share of about 50%.
(3)	High-speed optical access system (GE-PON):
This system has been internationally standardized (by IEEE) and adopted by Chunghwa Telecom (Taiwan), TOT (Thailand), PCCW (HongKong), and other overseas carriers.
Feature Articles

In addition to providing technologies and products,
NTT is also building relationships with overseas telecommunication carriers by receiving interns andholding technology seminars (Fig. 4). The initial
focus here was Southeast Asia, but tie-ups with carriers in Central and South America have recently
begun.
4. Conclusion
Under the theme of building trust and connecting
people, NTT Access Network Service Systems Laboratories will continue to research and develop technology toward achieving a sophisticated communication environment and a safe, secure, and reliable
information sharing environment for the bettermentof society.
ProfileCareer highlights
Executive Manager, Senior Research Engineer,
Supervisor, Access Service and Network Architecture Project, NTT Access Network Service
Systems Laboratories.
Yukio Akiyama received the M.S. degree inmathematics from Hokkaido University in 1987.
After joining NTT in 1987, he engaged inresearch on operations support systems for theaccess network, failure analysis of LANs, hugedata analysis, and R&D product promotion. He is
now engaged in strategy planning of access network R&D and research on the architecture ofoperations systems. He is a member of the Information Processing Society of Japan and the Japanese Society for Artificial Intelligence.

NTT Technical Review

Feature Articles: NTT Tsukuba Forum 2010 Workshop Lectures

Current and Future Research on
Optical Fiber and Cables
Shigeru Tomita†
Abstract

This article introduces the organization, research group topics, andR&D directions of NTT Access Network Service Systems Laboratories,
which is researching and developing a full range of access-system technologies with a focus on optical fiber and cables.

1. Introduction

2. Research topics by group

NTT Access Network Service Systems Laboratories is fully engaged in the research and development(R&D) of access-system technologies. In particular,
the Access Media Project extracts core technologies
from themes selected through strategic studies,
researches and develops those technologies, andpasses on the R&D results to various promotion projects. In short, it exclusively handles the R&D of coretechnologies considered necessary for future systems. The Access Media Project consists of fourgroups. Some of the topics they are working on are
described in more detail in section 2.

2.1 B
 ending-loss insensitive fiber (Media Utilization Group)
One consequence of the rapid penetration of fiberto-the-home (FTTH) services is that many unskilledworkers have came to be involved in the deployment
of optical fiber. As a result, optical fiber bending loss
became a frequent occurrence in the field. This problem led to active development of bending-loss insensitive fiber.
Standardization of optical fiber insensitive to bending loss is progressing as Recommendation G.657 in
ITU-T (International Telecommunication Union,
Telecommunication Standardization Sector). There
are two categories according to compatibility withexisting optical fiber specifications (G.652): Category A having full compatibility and Category B having
partial compatibility (Table 1).
There are two approaches to decreasing bending
loss: control the refractive-index distribution (optimal-refractive-index-distribution type of fiber) andform air holes (microstructured fiber). The former
method controls the refractive-index distribution ofexisting single-mode fiber (SMF) to suppress bending loss, but its suppression effect is smaller than thatof the latter method. The microstructured type, on theother hand, achieves large differences in refractive
index within the optical fiber, which enables considerable design freedom. NTT has been using microstructured fiber for some time. It comes in various
kinds such as hole-assisted fiber (HAF) and this type(1)	Media Utilization Group: next-generation outdoor optical line technology(2)	Media Maintenance Group: optical line testing
technology, media network management andoperation technology, and preventive maintenance technology(3)	Advanced Media Research Group: new opticalfiber structures(4)	Media & Equipment Monitoring Group: media
measurement technology† NTT Access Network Service Systems Laboratories
Yokosuka-shi, 239-0847 JapanNTT Technical Review

Feature Articles

Table 1. Development and standardization of bending-loss insensitive fiber.
G.657
Low-bending-loss optical fiber for access networks
Category A
Fully compatible with G.652

Minimum bending radius
10 mm

7.5 mmA1
Specified

A2
A3
Specified Under discussion

B1
B2
No standard product Specified

Category B
Partially compatible with G.652

5 mm

B3
Specified

G.652: standard for SMF

Desired bending-loss and cutoff-wavelength characteristics can be achieved bycontrolling the hole occupancy rate.
(nm)
1600
1500

1

1400

10−1

1300

10−2

1200

10−3

a ≈ 4.5 mm, ∆ ≈ 0.35%
0

0.2

0.4

0.6

Cutoff wavelength λc

Bending loss αb(dB/turn) @1625 nm, R = 5 mm
102
Bold lines:
calculated results
10
Plotted data:measured results

1100

Hole occupancy rate S

Fig. 1. HAF hole occupancy rate and transmission characteristics.

also includes nanostructured fiber.
NTT has developed single-mode HAF design technology that simultaneously achieves single-mode
transmission characteristics equivalent to standard
SMF and low bending loss characteristics that greatly
surpass the G.657.B.3 standard. The transmission
characteristics of HAF can be easily determined fromthe area ratio of the hole section in the annular regionof HAF (hole occupancy rate) and the core structure(core radius and refractive index). Bending loss
decreases as the hole occupancy rate increases, but at
the same time, the shortest single-mode wavelength(cutoff wavelength) increases, which prevents singlemode transmission from being achieved. Setting ahole occupancy rate of 0.3–0.4 yields optimal transmission characteristics for maintaining the cutoff
wavelength while suppressing bending loss (Fig. 1).
An example of HAF that can simultaneously
Vol. 9 No. 5 May 2011

achieve single-mode transmission characteristics andlow bending loss has the following properties: hole
occupancy rate of 0.41, bending loss (at 1625 nm,
R=5 mm) of 0.04 dB/turn, cutoff wavelength of 1126
nm, and loss (at 1550 nm) of 0.19 dB/km.
NTT is already providing free-bending optical fiber
cord using HAF with a large bending-loss suppression effect. This cord can be deployed by ordinary
people within their homes. Moreover, there are plans
to extend single-mode HAF to NTT office facilities
and other indoor and outdoor facilities with the aimof achieving even higher levels of transmission quality and reliability.
2.2 S ingle-mode HAF optical cord (Media Maintenance Group)
A distribution frame can be found at the point
where NTT office cables connect to outside cables. InFeature Articles

Ringc- The fiber-fuse propagation phenomenon depends on therelationship between diameter c of the circle inscribing
the holes and the diameter of the melted area (Dmelted) [1].
- Dmelted is assumed to be nearly the same as the diameter ofthe plasma region.

DmeltedFiber fuse propagation versus Dmelted/c
Pin (W)

Dmelted (µm)

Dmelted /c

Fiber fuse

HAF-A

15.6

23.5

0.77

Propagate

HAF-B

15.6

23.5

1.37

Not propagate

HAF-C

13.5

22.8

2.39

Not propagate

PCF

14.3

23.2

2.35

Not propagate

Source: K. Takenaga, S. Tanigawa, S. Matsuo, M. Fujimaki, and H. Tsuchiya, “Fiber Fuse
Phenomenon in Hole-Assisted Fibers, Proceedings of the 34th European Conference andExhibition of Optical Communication ECOC2008, P.1.14

Fig. 2. Relationship between fiber fuse and Dmelted/c.

the work of connecting these cables, there are many
places where workers can come into direct contact
with optical fiber. Applying low-bending-loss opticalfiber to those places can be an extremely effective
measure for maintaining quality. Shock-resistanceexperiments have shown that, while SMF can begreatly affected by shocks, single-mode HAF exhibits no shock-induced frame errors. Therefore, the useof single-mode HAF in a distribution frame caneliminate worries about transmission quality loss
even if optical fibers should be accidently bent or
pulled.
2.3 F
 iber fuse studies (Advanced Media ResearchGroup)
Increasing the amount of incident light in an opticalfiber can raise the fiber’s internal temperature andcreate a plasma in which discharge phenomena occur.
This flash of light can propagate back toward the lightsource and damage the optical fiber in a process
called fiber fuse. In SMF, this can occur at an opticalpower of about 1.3 W (at a wavelength of 1480 nm).
By contrast, in holey fiber, this fuse-propagationthreshold is very high. We have found that fiber fusedoes not occur in photonic crystal fiber (PCF) or HAF
for input power below 9.0 W (at 1060 nm) and 8.1 W(at 1550 nm), respectively. In the latest reports, thephenomenon can be controlled for light sources withpower in excess of 10 W in PCF and HAF at wavelengths of 1480 nm and 1550 nm, respectively.
Fiber fuse was found to terminate at the connectionpoint between ordinary optical fiber and holey fiber.
In an experiment in which SMF and HAF were connected, a flash propagating from the SMF side createdmany harmful cavities in the SMF but lost its momentum and disappeared after crossing the connection
point. The reason for this fuse propagation termination is considered to be that the density of the propagating plasma suddenly decreased once its expanding
breadth reached the air holes in the holey fiber.
Various types of HAF and PCF were used to compare propagation phenomena and clarify the relationship between fiber fuse and hole structure. It was
found that the relationship between the diameter ofthe circle inscribing the holes (c) and the diameter of
the area melted by the fiber fuse (Dmelted) determines
the propagation characteristics (Fig. 2). Specifically,
if Dmelted is less than c, that is, if the ratio Dmelted/c isless than 1, the fiber fuse propagates, but if it isgreater than 1, no propagation occurs.
This finding suggests that plasma propagation
might be suppressed upon reaching air holes. To test
this idea, a fiber fuse was propagated in HAF having
a structure in which Dmelted and c were nearly equal.
The manner in which the core was destroyed wasfound to differ greatly from that in ordinary SMF. In
SMF, cavities caused by core melting appeared
sequentially at very short intervals (10 µm) while in
HAF, cavities opened up at relatively long intervals(330 µm) and destroyed the core. When the section ofdestroyed core was analyzed, it was found that Dmelted
broadened gradually and came to a stop near to the air
NTT Technical Review

Feature Articles

Achieves a resolution of 5 cm at 40 km: a level not yet attained by any other reflectometer

100 m

Measurement resolution

10 m: Current experimental results(laboratory environment)

C-OTDR
OTDR

1m
10 cm
PNC-OFDR
1 cm
C-OFDR
1 mm

OLCR
Device
1m

10 m

LAN

Access

100 m

1 km

Relay
10 km

Submarine

100 kmMeasurement distance
OLCR: optical low coherence reflectometry

C-OTDR: coherent-OTDR

Fig. 3. PNC-OFDR for long-distance, high-resolution measurements.

holes. It was also observed that energy concentrated
after propagation stopped and that a fiber fuse reoccurred, producing a repeating propagation phenomenon. Although the reason for this could be inferred tobe the occurrence of boundary phenomena, a detailed
explanation has not yet been given.
2.4 P
 hase-noise-compensated optical frequency
domain reflectometry (Media & Equipment
Monitoring Group )Coherent optical frequency domain reflectometry(C-OFDR) is a technique for locating fault points andmaking distortion-distribution measurements in thelongitudinal direction of optical fiber. This technique
has superior resolution characteristics but is limited
to measurement distances of 2–3 km owing to the
influence of phase noise from the light source. On theother hand, optical time-domain reflectometry(OTDR), which makes measurements within an optical fiber by injecting optical pulses to minimize theeffect of phase noise, is capable of long-distancemeasurements but suffers from low resolution.
Phase-noise-compensated OFDR (PNC-OFDR)
achieves both long-distance and high-resolution measurements by monitoring phase noise with an auxiliary interferometer and removing its effect. It cantherefore maintain accuracy even at long distances
Vol. 9 No. 5 May 2011

(Fig. 3). The auxiliary interferometer compensatesfor phase components by electrically storing phasenoise data in memory and superposing components.
This technique does not suffer from measurement
disablement due to excessive phase noise at long distances. PNC-OFDR can achieve a resolution of 5 cm
from 40 km away, which exceeds those of all otherreflectometry methods.
PNC-OFDR is very effective for detecting spanswith high polarization mode dispersion (PMD). In
optical fiber, PMD, which arises from optical birefringence, is one factor limiting transmission speed.
It has come to be controlled in recent optical-fiber
products but not in older products. To maintain transmission quality in the system, high-PMD spans must
be located and replaced with new optical fiber. In ahigh-PMD span, short-period fluctuations in polarization occur in the transmission direction, and such
fluctuations can be used to identify high-PMD locations. However, the fluctuation period is less than a
few tens of centimeters, which means that detection
requires a high resolution of 5–10 cm.
Moreover, as the relay interval on transmission
paths can currently be up to 80 km, a measurementdistance performance of at least 40 km is needed
when making measurements from both ends of theinterval. In an experiment to assess PNC-OFDRFeature Articles

1800

1900

Morse
telegraphy(1835)

2000

Telephone
Copper twisted pair (1835– )(1876)

PCM(1938)Year

ADSL(1995)

Coaxial cable (1934– )Multilevel
modulation(20XX– )WDM(1990)
Laser
transmission Optical fiber (1980– )(1953– )ADSL: asymmetric digital subscriber line
PCM: pulse code modulation
WDM: wavelength division multiplexing

New media
transmission(20XX– )? (20XX– )Fig. 4. History of wired transmission media

based measurement, a high-PMD fiber taken from thefield was installed at the end of about 40 km of SMF
and PMD was clearly identified at that location.
3. Directions of future optical fiber research
3.1 Overview
The history of wired transmission media beganwith copper twisted pairs in Morse telegraphy andprogressed to coaxial cable and then optical fiber inthe 20th century, resulting in the development of newtransmission systems (Fig. 4). The development of
optical-fiber technology brought a huge leap in transmission capacity, but as demand for even higher
capacities grew, capacity limits for conventional SMF
began to be observed. Improved or new forms oftransmission media are being eagerly sought. Two
optical-fiber-based candidates for improved transmission media are multicore optical fiber and multimode optical fiber. The former has multiple coreswithin one clad, which can improve the spatial density and achieve high-capacity transmission. The latter has a structure capable of multiple-input multipleoutput (MIMO) transmission and can achieve highcapacity transmission through multichannel propagation. Next-generation studies on the possibility ofachieving transmission media for carrying terahertzband and ultraviolet light signals are also being performed.



3.2 Higher cable density
Small-diameter high-density optical cable technology increases transmission capacity by increasing
cable density. A 1000-core optical fiber cable of thelatest slot-type design in current use has an outer
diameter of 23 mm and a weight of 0.45 kg/m, while
the new small-diameter high-density optical cablecurrently under development is designed to have anouter diameter of 15.8 mm and a weight of 0.19 kg/m.
Thus, the new cables will lead to very compact installations. A number of foreign firms are involved in
making cables thinner and lighter and the mostadvanced research product from these firms has adensity more than 1.5 times existing levels. Nevertheless, the pursuit of higher fiber densities is approaching inherent limits and we can expect the objective of
future cable R&D to shift toward functional enhancements.
3.3 Manpower shortage solutions
The number of employees involved in cable deployment and maintenance is forecast to decrease byaround 60% in seven years time as aging workers
retire. Replacing those employees with younger staff
is one countermeasure, but there will still be a great
shortage of staff with the appropriate skill set. Thereis therefore an urgent need for navigation-based support systems and equipment that can be operated byunskilled staff.

NTT Technical Review

Feature Articles

ProfileCareer highlights
Senior Research Engineer, Executive Managerof the Access Media Project, NTT Access Network Service Systems Laboratories.
Shigeru Tomita received the B.S. and D.Eng.
degrees from Nihon University, Tokyo, in 1983
and 1993, respectively. After joining the Ibaraki
Electrical Communication Laboratories of Nippon Telegraph and Telephone Public Corporation(now NTT) in 1983, he engaged in research on
optical fibers and optical fiber cables. From 1995
to 1996, he engaged in development of outsideplant planning tools in NTT’s Outside Plant Planning Division. After returning to the laboratories,
he worked to develop optical components such as
connectors and cords for use indoors. From 2008
to 2010, he was the leader of the Advanced Media
Research Group. He is a member of IEEE and theInstitute of Electronics, Information and Communication Engineers.

Vol. 9 No. 5 May 2011

Feature Articles: NTT Tsukuba Forum 2010 Workshop Lectures

Trends in Wireless AccessTechnologies toward Expansion of
Broadband and Ubiquitous Services
Toshihiro Manabe†
Abstract

This article introduces wireless technologies being studied in the Wireless Access Systems Project at NTT Access Network Service Systems
Laboratories. To achieve flexible access networks that meet various needs
or demands, the coexistence of optical fiber and wireless systems is indispensable. It also mentions electromagnetic wave propagation technology
and technology for increasing frequency utilization as core technologies
of wireless systems and eco-related activities that began in 2010.

1. Overview of wireless systems
1.1 C omprehensive view of wireless technology
R&D
NTT is conducting research and development(R&D) of wireless systems and deploying a variety ofwireless access services to satisfy different objectives
and accommodate different types of service areas. In
satellite communications, for example, we are developing technology for compact earth stations that canapply the wide-area capability of satellite communications to circuit restoration in disaster areas andtechnology for mobile-multicast satellite communications systems for application to maritime communications in places where the laying of optical fiber is
impossible. And for rural areas, we are providing
communication services using the combination of an
optical fiber system (from an NTT building to a certain point) and a fixed wireless access (FWA) system(from that point to end users). At the same time, we
are working on the development of a triple-play FWA
system that can support quality of service (QoS) andprovide video and telephony functions conforming to† NTT Access Network Service Systems Laboratories
Yokosuka-shi, 239-0847 Japan

0AB-J specifications (where 0AB-J refers to a 10digit phone number starting with 0).
Meanwhile, for urban areas, NTT is developing
nomadic wireless access (NWA) and cognitive-radio
systems that can provide high-speed wireless local
area network (LAN) services in designated publicareas such as airports, train stations, and cafes.
Expanding the service area while keeping costs down
is a problem common to FWA and NWA, but it isbeing solved by multihop technology that uses wireless repeaters to broaden the service area. The application of multihop technology has made it possible toeasily expand wireless LAN areas that have, until
now, been just spots.
In addition to the above, we are developing personal wireless router (PWR) technology that enables
terminals equipped with a wireless LAN function to
make connections over a broad region instead of justa limited area. As a wireless LAN router that can be
carried anywhere, a PWR enables a wireless LAN
terminal to be used seamlessly at outside locations or
at home. We are also developing ubiquitous systems(wide-area sensor network systems) for gathering
information about various types of machines andfacilities situated over a wide area such as automobiles, transport vehicles, and vending machines.
NTT Technical Review

Feature Articles

Wide area
Slow, but covers up
to several kilometers
10 km

Service area

Wide-area
ubiquitous
1 km

Mobilehigh-speed

FWA(P-P)3Gceccellular

3.5G
cellularellular
ar

WiMAX

LTE

High efficiency
Flexible
100 m
802.11b802.11a/g

802.11n802.11ac/ad

10 Mbit/s 100 Mbit/s

1 Gbit/s

RFID tags

High-speed
Fast, but covers
a small area

10 m
1 kbit/s

10 kbit/s

100 kbit/s

1 Mbit/s

Transmission speed

Fig. 1. Directions of wireless technologies.

The Wireless Access Systems Project is also
researching and developing fundamental technologies in support of the above wireless transmission
technologies.
1.2 Future directions of wireless technologies
The development of wireless technologies has traditionally focused on increasing transmission speeds.
The wireless LAN standard IEEE802.11, though supporting only a small area, initially specified transmission speeds of only about 1 Mbit/s but now specifies
speeds in excess of 100 Mbit/s and speeds above
1 Gbit/s are under study. Greater speeds for mobile
devices over broader service areas have also been
pursued in system development from 3G (third-generation) cellular to Long Term Evolution (LTE). In
addition, FWA has come to provide service areas
several kilometers in size for point-to-point (P-P)
connections and several hundred meters in size forpoint-to-multipoint (P-MP) connections at transmission speeds of about 10 Mbit/s in both cases.
More recently, studies have been progressing on
wide-area ubiquitous systems that emphasize widearea coverage as a new technology direction separate
from the pursuit of higher speeds. The wide-areaubiquitous system was born from the idea that a sensor network could be constructed by enhancing radiofrequency identification (RFID) tags and extending
Vol. 9 No. 5 May 2011transmission distances. Although supporting speedsof only several kilobits per second, it features a service area several kilometers in size (Fig. 1).
2. Activities toward expansion of broadband
and ubiquitous services
2.1 Satellite communications systems
NTT is currently providing the following satellite
communications services.
-	Infrastructure satellite communications system(for disaster response): maintains public lifelines
in disaster areas (NTT EAST and NTT WEST)-	Infrastructure satellite communications system(for remote islands): provides universal service(NTT EAST and NTT WEST)-	Maritime broadband system: provides broadband communications to ships at sea (NTT Communications)-	WIDESTAR & WIDESTAR II: provide satellite
mobile communications (NTT DOCOMO)
For each of these services, improved functionality
is required to meet a high demand for smaller andmore economical equipment, greater mobility, higher
bandwidth and capacity, improved security, extremely wide coverage at low bit rates, and so on. To meetthese needs, NTT laboratories are investigating theextension of existing services, the renovation ofFeature Articles

Present

New systems
Transportable antenna

Aperture: 55 cm
Weight: 30 kg
Remote-islands satellite
communications system(Ku-1ch)Aperture: 75 cm
Weight: 100 kg

Aperture: 75 cm- Automatic satellite capture(at installation)
Weight:20 kg max.

Aging
14–16 years old
Large and heavy

Disaster-response satellite
communications system

Aperture: 1.2 m
Weight: 150 kg

Maritime broadband
system
(Ku-Globe)

Aperture: 70 cm
Weight: 170 kg

Manual satellite
capture→ Radio skills
necessary

Mobile antenna

Aperture: 40 cm- Automatic satellite capture(at installation)- Automatic satellite tracking(during operation)
Weight:20 kg max.

Automatic signal testing tool
Enables signal transmission tests to be performed
remotely from a base station: Reduces setup timefrom 60 to 10 min. and does not require radio qualifications.

Fig. 2. Development of compact earth stations for satellite communications.

services, and the development of new services.
(1) Compact earth station
One key advantage of satellite communications isthat a lifeline can be secured by simply setting up
earth stations at a number of points and then connecting them via satellite. However, most of the facilities
for existing earth stations are 14–16 years old while
also being too large and heavy to be easily transported. Moreover, their operation requires skilled radio
technicians to orient the antenna in the direction of
the satellite (manual satellite capture). In response tothis situation, we have developed new systems (transportable type and mobile type) that are significantly
smaller and lighter. The transportable type has an
automatic satellite capture function and the mobile
type has automatic satellite capture and tracking
functions to improve operability (Fig. 2).
The field of wireless communications is not
immune to the problem of a dwindling number oftechnicians as the numbers of licensed radio operators is on a downward trend. As one countermeasure
to this problem, we are developing an automatic
uplink access testing tool. This tool enables uplink
access tests to be performed remotely so that earth
stations can be put into commission even by unlicensed personnel and setup time can be greatly shortened from 60 minutes to only 10.
(2) Multi-domain signal processing technology
The frequency band of a satellite transponder isextremely limited. In addition, as a result of the setting and releasing of channels having different bandwidths, unused frequency slots are scattered acrossthe transponder’s bandwidth and these prevent theentire band from being used. To make effective use ofsuch unused frequency slots, the spectrum of themodulated signal is divided into subspectra, some ofwhich can then be purposefully removed or superposed to reduce the bandwidth required. The verticaland horizontal polarization axes can also be shared sothat subspectra can be assigned as desired.
The purpose of the above techniques is to improve
spectrum utilization efficiency, but these techniques
also have a positive side effect from the viewpoint of
security. Because the spectrum of the modulated signal is broken down into fine sections before transmission, the signal cannot be correctly demodulated by athird party even if a portion of the band can beobserved.
This multi-domain signal processing technology
enables a single satellite transponder to be shared bya disaster-response infrastructure satellite system, aremote-islands infrastructure satellite system, and amaritime broadband satellite system and enables awide-area large-capacity system to be compact andeconomical while also having improved security.
2.2 FWA system
On the basis of the current Wireless IP Access System (WIPAS (IP: Internet Protocol)), we are developing an FWA system supporting triple-play services
NTT Technical Review

Feature Articles

Network
Wireless LAN network

Home

HSPA network

StationAirport

Cafe

Hotel

OfficeSchoolEthernet network

Home

OfficeSchoolPublic area

Private area

Hotel

Automatic selection and connection/switching to optimal broadband service
Wireless LAN(WAN-side)
Connection to wireless LAN in anarea with high-speed wireless LAN

HSDPA
Ethernet

PWR
Wireless LAN(LAN-side)

Diverse Wi-Fi devices

Game console

LaptopMobile Internet device,
e-reader, etc.

Music player

Digital camera

Fig. 3. PWR: core terminal of NWA and cognitive radio.

equipped with a QoS control function including
0AB-J support and a multichannel video delivery
function. For P-P (one-to-one) connections, this system will provide a maximum transmission distance ofabout 1.3 km and a transmission capacity of about
180 Mbit/s (total for uplink and downlink). Moreover, for P-MP (one-to-n) connections, the system
will have a multicast function enabling the simultaneous provision of Internet, voice over IP (VoIP), andvideo services.
When wireless LAN was first introduced, terminals
equipped with Wi-Fi were basically limited to laptop
computers and personal digital assistants (PDAs).
Since then, however, Wi-Fi-certified terminals havecome to be installed in a wide variety of products fordiverse applications, from business to personal needs
and from indoor to outdoor use. However, places
where wireless LANs can be used are still basicallylimited to one’s home, train stations, trains, offices,and cafes. Consequently, Wi-Fi-only terminals without 3G wireless access functions cannot connect tothe network from other locations.
In the light of this situation, NTT Broadband Platform, Inc. has undertaken the development of a PWR
as a key device for connecting to the network at any
Vol. 9 No. 5 May 2011

time. It can accommodate various types of Wi-Fi
devices on the LAN side and features wireless LAN,
high-speed packet access (HSPA), and Ethernet on
the wide area network (WAN) side. It can automatically select and connect to the broadband service
depending on the user’s current location (Fig. 3).
It might appear at first glance that there is no needfor a wireless LAN function on the WAN side. However, including wireless LAN here, even in a terminal
equipped with 3G wireless access, means that theterminal will be able to use a service that is faster than
3G wireless access when connecting at public wireless-LAN hotspot access points. In other words, it isdesirable to offer wireless LAN as an optional wireless access method.
Moreover, another benefit of the PWR is that it has
an authentication agent function. A terminal without
an authentication agent function cannot make use ofa public wireless-LAN service that requires authentication. Furthermore, even if a terminal has an authentication function, the user must still follow a troublesome procedure for inputting an ID and password.
The PWR eliminates this bother and enables the terminal to be used anywhere and anytime regardless ofwhether it implements an authentication function.
Feature Articles

2.3 Wide-area ubiquitous systems
Contrary to recent network technology trends
where high-speed and large-capacity features are
dominant, wide-area ubiquitous systems, thoughsmall in capacity, have been attracting attention as
distinctive wireless systems that can cover a wide
service area. These wide-area ubiquitous systems
have the following features.
-	A wireless area with a radius of several kilometers-	Transmission and reception of information
between various types of sensors/actuators andIP terminals-	Low information capacity (a few hundred bytes
to several kilobytes per terminal per month) andlow rates (about 100 yen per month)-	Accommodation of an extremely large numberof terminals (10–100 times the population)-	Extremely small terminals with long lives (battery exchange required once every 5–10 years).
-	High security (not currently achievable by theInternet and RFID tags)
Ubiquitous terminals, which excel in operability,
utility, durability, and cost efficiency, can be attached
to people, vehicles, measuring devices, and information appliances, and the information obtained fromthem can be consolidated and controlled in the system. Application examples are the reading of gas andelectricity meters, stock inventory of vending
machines, location recognition, determination of traffic conditions, route selection, measurement of CO2
emissions, and assessment of green measures.
NTT has been holding verification trials in Special
Ubiquitous Zones [1] within Tokyo as part of a threeyear project beginning in 2008. In these trials, NTT
collaborated with gas companies to test network connectivity (telemetry and safety) and with telecommunication operators to test terminal mobility and location accuracy (mobility and signal reachability).
A wide-area sensor network consists of application
servers on the user side (gas companies and telecommunication operators as joint participants in thesetrials), a master base station, (at Kyojima in Sumidaku), remote base stations (Kyojima in Sumida-ku,
Kanamachi in Katsushika-ku, and Chuo in Edogawaku), and network management equipment (NTTMusashino R&D Center) linked via an optical network. In the trial communication system, packets
transmitted from wireless terminals, each about thesize of a business-card case, are transferred throughthe optical network and the sensor network. The
transmission power of these wireless terminals isvery low, but the reception system composed of three
remote base stations can maintain communication
quality (site diversity technique).
2.4 E
 lectromagnetic wave propagation technology
Electromagnetic wave propagation is a very important research theme in terms of equipment design,
radio zone design and the establishment of core competence. In this area, questions that should be studiedchange as transmission speeds of wireless communication systems increase. Studies during the 1990s(1st- and 2nd-generation cellular systems) focused onreceive-level characteristics, while those during the
2000s (dominated by wireless LAN and 3rd-generation cellular systems) analyzed the temporal spreading of incoming waves (differences in signal arrival
times due to reflection and scattering) in addition toreceive-level characteristics. Looking forward, futuresystems applying multiple-input multiple-output(MIMO) technology now under study (for next-generation wireless LAN and other systems) will be able
to achieve high-speed and high-reliability communications by sending and receiving signals using multiple antennas and making use of complex electromagnetic wave propagation conditions in which signals arrive spatially not just from one direction but
from many directions. It will therefore be necessary
to analyze and model electromagnetic wave propagation characteristics that include spatially spreading
characteristics in addition to studying receive levels
and the temporal spreading of incoming waves as in
the past.
The frequency bands used for wireless communications also broaden as systems become diverse, so the
propagation characteristics in various frequency
bands must also be studied. Furthermore, in broadband wireless access, rainfall can cause electromagnetic waves to fade and scatter when millimeter-wave
bands are used. Therefore, consideration must be
given to such rainfall-related attenuation.
2.5 T echnology for increasing frequency utilization efficiency
Spectrum resources are limited, and effective use of
the radio spectrum has been an incessant problem inwireless systems. Moreover, the 6-GHz band andbelow, which is suitable for mobile communications,is seriously congested and there is no way of easing
this congestion other than by increasing utilization
efficiency by having multiple systems share the same
frequencies. The means adopted so far to enable such
NTT Technical Review

Feature Articles

Present

Proposed technology
Frequency spectrum

Frequency

Interference

Frequency
High spectrum utilization efficiency is achieved byallowing interference and using
interference-compensation techniques.

Each system is segregated by time and/or frequency to avoid
interference thereby limiting spectrum utilization efficiency.
(1) Interference suppression (frequency control)
Suppression filter

Technical difficultyInterference compensation effect×Spectrumsuperposedtransmission=(2) Interference cancellation (frequency/time control)
Replica=−

Wireless network
codingTarget: 10-fold improvementin spectrum utilization
efficiency by 2015(3) Interference reduction (adaptive array)(spatial control + (frequency/time control))×=

Adaptive array
Interferencecompensation
between systems

Array antenna

Fig. 4. From interference avoidance to compensation: interference compensation techniques.

frequency sharing is to detect the surrounding environment and take measures to avoid interference(interference avoidance technology), which has been
implemented in carrier sense multiple access/collision avoidance (CSMA/CA) and cognitive radio.
However, such an interference-avoidance type ofapproach requires each system to be segregated interms of time and/or frequency, which itself is limited
in increasing frequency utilization efficiency.
In a current study, we are looking at methods thattake an aggressive approach to interference by allowing for interference in frequency sharing but removing any interference that may occur (interferencecompensation frequency sharing system). There areseveral interference-compensation techniques assummarized below (Fig. 4).
-	Interference suppression: cuts off interference
power by using a suppression filter, but also
reduces the power of the original spectrum
resulting in slight deterioration-	Interference cancellation: generates a replica ofinterference to subtract it from the received signals.
Vol. 9 No. 5 May 2011-	Interference reduction: sets up an antenna arrayto make an antenna beam pattern and does notreceive signals in the direction of arriving interference
The technical difficulty of these techniques rises in
the order of suppression, cancellation, and reduction
but so does the interference-compensation effect. Our
aim is to achieve a ten-times increase in frequency
utilization efficiency by 2015 by applying thesemethods.
2.6 Green wirelessWe are also working on reducing power consumption and CO2 emissions in wireless systems. One
example of our efforts here is the virtual base station,
which can be created by interlinking many wireless
LAN access points connected by optical fiber withthe aim of lowering power consumption at the systemlevel.
It is also instructive to consider that a wireless system, while providing information transfer by wirelessmeans, must be fed power by wired means. Achieving
independent power supplies for wireless systems hasFeature Articles

been said to be difficult, but we are investigating thefollowing two techniques.
(1)	Wireless power transmission: Power is transmitted to wireless equipment via radio waves froma remote location, which makes power supply
lines unnecessary and provides more flexibility
for the equipment installation location.
(2)	Energy harvesting: Radio waves emitted throughspace such as broadcast waves are concentrated
and converted into electric power for use as a
power supply for wireless equipment. Alternatively, natural energy such as sunlight can beused to generate power.
3. Conclusion
The mobility, flexibility, and extendibility of wireless systems have made wireless access essential tothe diverse development of access-network services.
The development of wireless technologies is as crucial and significant as that of optical access technologies in the construction of a seamless network environment.
Reference[1]

H. Toshinaga, H. Nishizawa, A. Yamagishi, K. Fujii, S. Teruhi. H.
Tsuboi, H. Shibata, and Y. Fujino, “Feasibility Test of Next Generation Wireless Network at a Special Ubiquitous Zone,” NTT Technical
Review, Vol. 8, No. 6, 2010.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2010
06sf3.html

ProfileCareer highlights
Executive Manager of the Wireless Access Systems Project and the Third Promotion Project,
NTT Access Network Service Systems Laboratories.
Toshihiro Manabe received the B.E. and M.E.
degrees from Kyushu Institute of Technology,
Fukuoka, in 1985 and 1987, respectively. After
joining NTT in 1987, he engaged in research on
26-GHz microwave systems. From 1990 to 1992,
he was with NTT Network Systems Development
Center, where he developed microwave systems
connecting cell sites of mobile phone systems.
From 1996 to 2002, he worked on R&D of theAdvanced Wireless Access system at NTT Laboratories. From 2002 to 2006, he was with NTT
Broadband Platform, Inc. developing public
wireless LAN systems and services. After returning to NTT in 2006, he engaged in R&D of wireless access systems and services using wirelessLAN. His activities are currently focused on thedevelopment of wireless access systems andresearch on wireless core technology. He is amember of the Institute of Electronics, Information and Communication Engineers.

NTT Technical Review

Regular Articles

Monolithic Integration of Silicon
Photonics Devices for
Telecommunications Applications
Tai Tsuchizawa†, Hidetaka Nishi, Rai Kou, Toshifumi
Watanabe, Hiroyuki Shinojima, Koji Yamada, andSei-ichi Itabashi
Abstract

This article introduces our recent progress in silicon photonics device integration for telecommunications
applications. We have developed new processes for selective epitaxial growth of Ge on a Si waveguidecore and for low-temperature deposition of silica waveguide film. Using these processes, we havemanaged to monolithically integrate Si variable optical attenuators (VOAs) with a Ge photodetector and
Si VOAs with a silica arrayed waveguide grating. These integrated devices exhibit sufficient performancefor application to future telecommunications systems that combine wavelength-division multiplexing
and burst-mode packets.

1. Introduction
The rapid and huge increase in telecommunications
traffic requires highly integrated photonic devices,which make possible high-functionality, low-power,
and low-cost telecommunications modules. Recently,
photonic integration has been intensively pursued byapplying silicon (Si) photonics technology because
photonic devices made of Si have many advantages,
such as ultrasmall size, low cost, and convergencewith electronic devices. A more detailed review ofrecent R&D trends in Si photonics is given in [1].
Various passive and dynamic devices, such as
wavelength filters and modulators, have already beendeveloped using an ultracompact Si wire waveguide,
which is a promising platform for photonic integration [2]–[7]. Moreover, some active devices, such as
photodetectors (PDs) and light sources have recently
been developed on a Si wafer by using heteroepitaxy
technology for germanium (Ge) and wafer bonding† NTT Microsystem Integration Laboratories
Atsugi-shi, 243-0198 Japantechnologies for III-V materials [8]–[11]. We can now
make various individual photonic devices on the Si
platform, and some devices, such as filters, modulators, and PDs are already at a level suitable for practical application. As device integration on a chip is themost important advantage of Si photonics, researchon Si photonics is now shifting to the integration ofdevices having various photonic functions.
In this article, we describe two optical device integrations for telecommunications applications. One is
the integration of a Si variable optical attenuator(VOA) and a Ge PD and the other is the integration of
Si VOAs and a silica-based arrayed waveguide grating (AWG) filter. The VOA-PD integrated device
allows high-speed optical level control, which is very
important for suppressing fast gain transients andequalizing gain variations. The VOA-AWG integrated
device provides wavelength demultiplexing and highspeed power-level adjustment in individual channels.
These integrated devices should be applicable tofuture telecommunication systems that combine
wavelength-division multiplexing (WDM) and burst
packets.
NTT Technical Review

Regular Articles

2. Fundamental characteristics of
Si wire waveguide

3. Monolithic integration of Si VOA and Ge PD
3.1 Device structure and characteristics
Since Si has semiconductor characteristics, we caneasily implement various electronic device structures,such as PN (positive, negative), PIN (positive, intrinsic, negative), and MOS (metal oxide semiconductor)
Vol. 9 No. 5 May 2011(b)
SiO2(n=1.46−1.51)

SiO2~400 nm~600 nm

Si

Si

SiO2(n≈1.44)

SiO2

Si substrate

Si substrate

Fig. 1. C ross-sectional structures of (a) channeland (b) rib-type Si wire waveguides.

0Transmittance (dB)

Cross-sectional structures of Si wire waveguides
are shown in Fig. 1. We have developed two types of
Si wire waveguides: the single-mode channel type
and the rib type. Both types consist of a Si core andsilica-based cladding and are fabricated on a siliconon-insulator (SOI) wafer with a buried SiO2 layer of
3 μm. The thickness and width of our waveguide core
are roughly in the ranges of 200–300 nm and 300–600
nm. The rib-type waveguide is mainly used for
dynamic devices such as attenuators and modulators
based on carrier injection because the p+ and n+regions can be formed in the slab areas. The channeltype waveguide is used for passive devices such as
wavelength filters. The Si wire waveguide has a very
high refractive index contrast. This is advantageousfor high-density integration because it allows the core
to be less than a micrometer wide and the bending
radius to be just a few micrometers.
Transmission characteristics of our Si wire waveguide for 1550-nm infrared light are shown in Fig. 2.
To reduce the coupling loss to an external fiber, ourwaveguides have spot size converters (SSCs) at bothends. Each SSC consists of a Si inverse taper and a
low-index waveguide with a large core covering thetaper [2], [13]. For the measurement, high-numericalaperture fibers with a 4.3-μm field diameter were
butt-coupled to the SSC’s low-index waveguide. The
slope of the line in the figure shows propagation loss,
which is typically around 1 dB/cm. This is for transverse electric (TE) polarization, but the propagation
loss for transverse magnetic (TM) polarization israther lower. The loss of the Si wire waveguidedepends largely on the sidewall roughness of the Si
core. Improvements in the fabrication technique havegreatly reduced the loss due to sidewall roughness[12]. In Fig. 2, the transmittance corresponding towaveguide length = 0 shows the coupling loss for two
converters; one coupling loss is about 0.5 dB. The
superior performance in propagation and coupling
will satisfy the severe telecommunication standards
for insertion loss.

(a)−1.09±0.03 dB

−2
−4

1.18

−6

±0.0

8 dB

−8

/cm

−10
−12

0

1

2

3

4

5

6

7

Waveguide length (cm)Fig. 2. M easured propagation loss of a silicon photonic
wire waveguide with SSCs.

structures [5], [14]–[16], which give optical modulation ability through the carrier plasma effect. We havedeveloped a Si VOA with PIN-type carrier injection
structures in the rib-type Si wire waveguides [16].
The cross-sectional structure of the Si VOA is shownin Fig. 3. The rib-type Si waveguide has a 600 nm ×
200 nm core and 100-nm-thick slab. The p+ and n+regions are 1 mm long and defined in the slab section,and they are about 3 μm apart. The VOA based on Si
wire waveguides has the following advantages. The
smaller the core is, the faster the device works. Moreover, because of its ultrasmall core, the carrier density, which determines the optical absorption, can beeasily increased, so the size and injection current, or
power consumption of the device, can be reduced. We
have already demonstrated these advantages in our
fabricated devices. For example in a 1-mm-long
VOA, the 3-dB frequency bandwidth is over 100
MHz, which is about ten times higher than that inRegular Articles

Al electrode

Al electrode(a)

300–600 nm PE-CVD
SiO2
100 nmn~1020 cm–3+

BOX (3 µm)

i-Si
200–300 nm~3 µm

Al electroden+Alelectrodep~1020 cm–3

Ge 1 µm+

200 nmPE-CVD
SiO2

p+

Si slabGe mesa
8×50 µm

WaveguideBOX

Si substrate

Si substrate
BOX: buried oxide layer
PE-CVD: plasma enhanced chemical rapor deposition

Fig. 3. Cross-sectional view of the Si VOA.

(b)

1 mm

In
Si VOA

MMI
branchAl electrodeGe PD

Insulation
grooveRib-type Si wire
waveguideOut

Fig. 5. ( a) Cross-sectional structure of the Ge PD
and (b) its top view image.

Fig. 4. T
 op view image of monolithic integrationof Si VOA and Ge PD.

conventional devices. Operation with 30-dB attenuation in a 1-cm-long device requires about 55 mW,
which is about half the power consumption of conventional rib-type devices [17]. As this fast VOA isbased on a simple structure, a polarization-independent VOA can be achieved just by optimizing the Si
core size [18].
PDs made from Ge are preferred in Si photonics
because Ge has process compatibility with Si as well
as a large absorption coefficient at telecommunication wavelengths. Recently, we have successfully
integrated PIN-type Si VOAs and Ge PDs [19], [20].
A schematic of a fabricated VOA-PD integrated
device is shown in Fig. 4. The device consists of a Si
VOA, a 3-dB multimode interferometer (MMI)
branch, and Ge PD. The MMI branch was placed
between the Si VOA and Ge PD to route light to theoutside for device evaluation. The vertical cross-section of the Ge-PD and its top view are shown in
Fig. 5. The Ge PD is based on a vertical PIN photodiode. A Ge mesa was grown on a Si waveguide by
selective epitaxial growth in an ultrahigh vacuum
chemical vapor deposition (UHV-CVD) chamber[21]. A SiO2 film that acts as the overcladding of the
Si waveguides was used as a mask for the Ge selective growth. The thickness and size of the Ge mesa
were fixed to 1 μm and 8 × 50 μm2, respectively. To
prevent electrical crosstalk between each VOA and
PD through the Si layer, an insulation groove is madearound the VOA. For device characterization, we
injected 1560-nm-wavelength light with a TE-likemode through a lensed fiber into the waveguide witha 3-μm-expanded core at both edges. The infrared
light input into the VOA was split by the MMI branchat the VOA’s exit waveguide. One of the outputs was
fed to a Ge PD on the chip and the other to an external
fiber. The propagated optical power was attenuatedby carrier absorption when carriers were injected into
the waveguide.
The current-voltage (I-V) curves of a Ge PD in dark
and illuminated condition are shown in Fig. 6. Dark
current (Idark) was as low as 60 nA at 1 V of reverse
bias, corresponding to a dark current density of 15
mA/cm2. Such a low Idark can guarantee sensitivity ashigh as -41 dBm in the detectable minimum light
power. When light was injected into the waveguide, aphotocurrent was generated as shown in Fig. 6. The
estimated responsivity was around 0.8 A/W at reverse
bias of 1 V. The 3-dB frequency bandwidth of the Ge
NTT Technical Review

Regular Articles

10–2

0

10–3

Normalized response (dB)l = 1560 nm

10–4
Current (A)

10–5
10–6
Dark
10–7
10–8

Ge size
8 x 50 mm

10–9
10–10

–2

–1

0

–4
–6

w/ 150-MHz filter
w/o filter

–8
–10
–12
1 MHz

1

Si-VOA @ 10 mA
Ge-PD @ −1 V

–2

10 MHz

100 MHz
Frequency

1 GHz

10 GHz2

Fig. 8. F requency responses for synchronous operation
between the VOA and PD.

Voltage (V)Fig. 6. Current-voltage curves of a fabricated Ge
PD with and without light guided to a
waveguide.

–15

1560 nm–20

Optical power
at output fiber

–25

0.1

0.01
0

–30

Ge-PD
photocurrent
10

20

30

40

50

Optical power (dBm)

Photocurrent (mA)1

–35

VOA injection current (mA)

Fig. 7. Photocurrent of the Ge PD on chip and theoptical power detected off chip when the
VOA was operated with various injection
currents.

PD was a few gigahertz, which is limited simply by
the RC time constant.
The photocurrent detected at the Ge PD on-chipand optical powers monitored at the output fiber
under the condition of VOA current injection are
shown in Fig. 7. Since attenuation is linearly proportional to carrier density in the intrinsic region of a
VOA, the attenuated optical power in decibels
decreased linearly with respect to the injection current. The change in photocurrent corresponds well tothe optical power. This indicates that the PD precisely
detected the light intensity attenuated by the VOA.
Leakage current between the two devices was not
Vol. 9 No. 5 May 2011

observed in synchronous operation because of theinsulation groove made around the VOA. We confirmed that both devices fabricated in monolithic
integration worked synchronously with good performance. The frequency responses of the VOA-PD
integrated device are shown in Fig. 8. Regardless of
the reverse bias at the PD, the 3-dB cut-off frequency
in VOA-PD synchronous operation was about 130
MHz. The 3-dB cut-off frequency of the VOA wasaround 130 MHz, while that of the PD was in thegigahertz range. The frequency response of an integrated VOA-PD device is limited solely by the VOA.
3.2 Application to optical power equalization
One of the most promising applications of the
VOA-PD integration is fast optical power equalization for burst optical packets. For example, power
equalization of bursty upstream optical packets canenhance the dynamic range of receivers [22]. Since
the response time should be a few hundred nanoseconds in a 10-Gbit/s passive optical network (PON)
system [23], the 130-MHz frequency response of ourintegrated VOA-PD is sufficient for this fast power
equalization. To confirm the feasibility of the fast
optical power equalization, we attempted opticalintensity equalization using our VOA-PD device andan off-chip electrical feedback circuit [24]. The feedback circuit was a simple linear system. The photocurrent of the Ge PD was converted into a voltage
signal through a transimpedance amplifier (TIA). The
output voltage of the TIA was amplified by a differential
amplifier with respect to a voltage reference, which
represented the target power level for optical output.
Regular Articles

4.1 L
 ow-temperature deposition of silica waveguide films
Silica-based waveguides are very attractive for constructing high-performance passive photonic devices,such as AWG wavelength filters and interferometers
for receiver circuits because low propagation loss andsmall polarization dependence are expected [25]. On
the other hand, Si wire waveguide devices have otherexcellent features, such as very fast operation, lowpower consumption, and high integration density.
Therefore, integrating a Si waveguide device with asilica waveguide device should lead to high-performance practical devices for telecommunications
applications.
A serious obstacle to the integration of Si and silica
is the thermal degradation of the Si devices during the
fabrication of a silica waveguide. Silica waveguidefabrication generally involves a high-temperatureprocess at over 1000ºC in silica film deposition [26].
Such a temperature oxidizes the Si waveguide coreand destroys the PIN structures for Si modulation
devices and Ge PDs. For Si and silica device integration, we need a low-temperature silica film depositionOn-chip output power (dBm)

On-chip output power (dBm)

–15

150

Injection current (mA)

–20

120

–25

90

–30

60

–35

30

–40

–20

–15

–10
–5
0
5
On-chip input power (dBm)010Fig. 9. R
 esults of optical power equalization in DC
operation.

On-chip output power On-chip output power
(dBm)
(dBm)

4. Monolithic integration of silicon-based
dynamic and silica-based passive devices

180

–10

Injection current (mA)

Then, the signal was guided to the VOA driver, where
injection current proportional to the control voltage
signal was generated. The feedback circuit covered afrequency bandwidth from DC to 180 MHz.
The output optical power versus input power in DC
feedback operation is shown in Fig. 9. The output
power stabilized within a deviation of 2.7 dB evenwhen the input power varied by 22 dB. For 10-dB
input variation, output stabilization within a deviationof 0.8 dB was accomplished. The VOA injection current exhibited a monotonic increase with no irregularbehavior. This indicates that the feedback circuit
worked very stably even for a large dynamic range ofmore than 25 dB in optical input. The temporal
response of the output for a step-wise increase in the
input level is shown in Fig. 10. When the input opticalpower suddenly increased by 16 dB, the output power
was quickly recovered and stabilized within a 1.5-dB
residual error. The 3-dB recovery time was about 90
ns, which will satisfy the timing criterion for burst
optical packets in a 10G-EPON (10-Gbit/s Ethernet
PON) system. The recovery time includes a 40-ns
insensitive cable delay, which could be eliminated by
mounting an application-specific integrated circuit on
the VOA-PD chip.

5
w/o feedback
0
–5
–10
16 dB
–15
–20
–25
–10
Cable delay: ~40 ns
w/ feedback–15
Recovery time:Target: –30 dBm–20<90 ns @3 dB
–25
±3 dB
–30
–35
Residual deviation: <1.5 dB–40

Fig. 10. R
 esults of optical power equalization in pulse
operation.

method. We have recently developed one based onelectron-cyclotron-resonance plasma enhanced
chemical vapor deposition (ECR-PECVD). The ECR
plasma easily dissociates gas molecules and provides
moderate energy to the substrate. This enables fast
deposition of high-quality silica and silicon-rich silica (SiOx) films at low temperatures. The refractive
index and deposition rate of silica film by ECRPECVD with a mixture gas of SiH4 and O2 are shownin Fig. 11. In this experiment, the SiH4 flow rate wasmaintained at 25 sccm and the O2 flow rate waschanged. The results indicate that the silica film
refractive index can be controlled over a wide range
from 1.47 to 1.60 by forming SiOx (Si-rich oxide),which is achieved simply by adjusting the flow rate ofoxygen. The deposition rate is about 150 nm/min,
NTT Technical Review

Regular Articles

0.3
0.25

1.8

0.2

1.7

0.15

1.6

0.1

1.5

0.05

1.4

0

24

28

32

36

40

44

Transmittance (dB)

Refractive index

1.90Deposition rate (µm/min)

SiH4: 25 sccm

–2

y = –0.57x –0.88

–4
–6
–8
–10
–12

(a)
0

TE
2

4

6

8

10

12

0

O2 flow rate (sccm)

Fig. 11. Refractive index and deposition rateof silica film versus O2 flow rate withconstant SiH4 flow rate of 25 sccm.

Transmittance (dB)2–2y = –0.84x –0.38

–4
–6
–8
–10

(b)

TM

–12
0

160

4

6

8

10

12

Waveguide length (cm)140
Wafer temperature (°C)

2Fig. 13. T ransmittance of SiOx waveguides for(a) TE and (b) TM modes as afunction of waveguide length.

120
SiOx (n=1.47)

100
80
60
40
20
0

0

5

10

15

20

25

30

Deposition time (min)Fig. 12. W afer temperatures during ECRPECVD of silica film.

which is high enough for waveguide films that need athickness of a few micrometers. The wafer temperatures during the ECR-PECVD of silica film, whichwere measured with thermosensitive tape put on thewafer surface are shown in Fig. 12. Although thewafer was not cooled purposely, the wafer temperature was below 150ºC throughout the deposition timeof 30 min, which corresponds approximately to a 2µm-thick deposition.
To evaluate the optical loss of SiOx made by ECRPECVD, we made SiOx waveguides with a refractive
index contrast of about 3%. The core was made of
SiOx, whose refractive index is 1.515, and the size
was 3 μm square. The overcladding was SiO2, whose
Vol. 9 No. 5 May 2011refractive index is 1.47. These films were formed on
3-μm-thick thermal SiO2 on a Si wafer because the
SiOx waveguides were integrated with Si waveguides
on an SOI wafer with 3-μm buried SiO2. The transmittance of SiOx waveguides for TE and TM modes
as a function of waveguide length is shown in Fig. 13.
From the slope of the fitted line, we obtained propagation losses of 0.57 dB/cm for the TE mode and 0.82
dB/cm for the TM mode. These values are low
enough for making a practical device on a small chip.
The larger loss of the TM mode is probably due toleakage of the propagated light to the Si wafer. The
minimum bending radius of this waveguide is 0.5mm, which will significantly reduce the device size.
4.2 Si VOA and SiOx AWG integration
Using the low-temperature silica deposition technique, we have fabricated an integrated variableattenuator multiplexer/demultiplexer (VMUX/
DEMUX) [27], which is an important component forphotonic networks, such as a reconfigurable optical
add/drop multiplexing (ROADM) system. The
VMUX/DEMUX consists of VOAs for opticalpower-level control, PDs for power-level monitoring,
and an AWG for WDM. An optical microscope image
Regular Articles

SiOx AWG

2 mm
SSC

Si VOA

SSC

Fig. 14. O ptical microscope image of a fabricated VOAAWG integrated device.

40

30
Attenuation (dB)of the fabricated device is shown in Fig. 14. The
device was made by the monolithic integration of SiVOA and SiOx AWG on an SOI wafer with a 3-μmthick buried oxide layer. The AWG was made with
SiOx waveguides of D 3% and enables wavelength
demultiplexing of the C-band signal in 16 channels
with 200-GHz spacing. The Si VOA is 5 mm long andits structure is based on the PIN carrier injection
described in section 3.1. The AWG provides wavelength demultiplexing and the VOAs quickly adjust
the power level in each channel.
The silica and Si waveguide have very different
dimensions. The SiOx waveguide, which composes
the AWG, has a cross section of 3 × 3 μm2. The Si
wire waveguides, which compose the VOA, have a
0.2-μm core height, 0.6-μm core width, and 0.1-μm
slab thickness. The large difference in core size
causes a large coupling loss between two waveguides.
This is another problem in the integration of Si andsilica waveguides. We used an SSC to compensate forthe mode-size mismatch and connect them with low
loss. Each output port of the AWG is connected to a
Si pin-type VOA through SSCs. An SSC consists of a
Si inverse taper and a low-index waveguide with alarge core covering the taper [20]. The taper, which
gradually becomes thinner toward the end, is 300 μm
long and the tip is 80 nm wide. A low-index waveguide over the Si taper is made from a SiOx waveguide, which has an about-3-μm-square core andindex contrast of about 3%. In this device, the same
SiOx layer is used for the cores of the AWG’s waveguides, the cores of the low-index waveguide over the
Si taper of the SSCs, and the overcladding of the Si
wire waveguide. The sharing of SiOx layers for different purposes simplifies the fabrication process.
First, we examined the performance of the integrated Si VOAs. The relationship between attenuation and injected current is shown in Fig. 15. In theseexperiments, the DC source was connected to theelectrode pads of the VOAs. The Si VOA exhibitedlinear operation as a function of injected current andhad a dynamic range up to 30-dB attenuation with aninjected current of 70 mA. The power consumption
for 20-dB attenuation was 45.8 mW (44.0 mA, 1.04
V). These characteristics are almost the same as thoseof the stand-alone VOA, indicating that the
ECR-PECVD process did not affect the PIN structurein the waveguide. The measured frequency responseis shown in Fig. 16. The VOA had a 3-dB bandwidthof about 50 MHz. This frequency bandwidth is sufficient for level equalization for burst optical packets in
a 10-Gbit/s PON system. Next, as a demonstration of20@20 dB att.
44.0 mA
1.04 V

10

0
0

10

20

30
40
50
Injected current (mA)

60

70

80

Fig. 15. R elationship between injected current andattenuation of Si VOA in integrated device.

multichannel power equalization using the VMUX/
DEMUX, we operated the VOAs individually andmeasured the transmission spectrum of each channel.
The measured spectra are shown in Fig. 17. We separated the channels into groups of four and drove the
VOAs so that all the channels in a group had the same
intensity. We can see that the VOAs independently set
the optical level in a group. We verified that all of theintegrated VOAs operated, and we drove them so thatthe transmission level was equivalent every fourchannels. This device exhibits wavelength demultiplexing owing to the AWG and high-speed powerlevel adjustment in individual channels owing to the
Si-VOA, which has a 3-dB bandwidth of about 50
MHz. The fast level control on each wavelength
channel will be useful in future burst-mode WDM
telecommunications networks.

NTT Technical Review

Regular Articles

showed wavelength demultiplexing and fast power
optical power control of each wavelength channel.
Although the integration of many more devices isnecessary for practical use, we believe that the integration of Si photonics devices will enable us to makelow-cost, high-performance devices for telecommunications.

Normalized response (dB)

0

–3

–6
5 mA

Acknowledgments

10 mA
20 mA

–9
106

107

108

109

Frequency (Hz)Fig. 16. Frequency response of an integrated Si VOA
measured under injected currents of 5, 10, and
20 mA.

The Ge film-growth process was carried out at the
Wada Laboratory, the University of Tokyo. We thankProfessor Kazumi Wada, Professor Yasuhiko Ishikawa, and Dr. Sungbong Park for their cooperation anduseful suggestions.
References[1]

Flattened

Normalized output (dB)0

5 dB att.
10 dB att.

–1015 dB att.

–20
–30
TE
–40

1550

1555

1560
1565
Wavelength (nm)

1570

1575

Fig. 17. Demultiplexing and intensity adjustment forevery channel using the integrated VOA-AWG
device.

5. Conclusion
We demonstrated the monolithic integration of a
Si-wire-based VOA, Ge PD, and SiOx-based AWG.
To integrate photonic devices made of different materials, we developed new processes, including selective epitaxial growth of Ge on a Si core, and a lowtemperature method of silica film deposition. The Si
VOA and Ge PD integrated device showed good synchronous operation with a bandwidth of around 100
MHz, which is limited by the VOA. We demonstrated
that this device can work as a fast intensity equalizer
for burst-mode packets in optical network systems.
The Si VOA and silica AWG integrated device
Vol. 9 No. 5 May 2011

Special Feature: Silicon Photonic Technologies Leading the Way to a
New Generation of Telecommunications, NTT Technical Review, Vol.
8, No. 2, 2010.
https://www.ntt-review.jp/archive/2010/201002.html[2] T. Tsuchizawa, K. Yamada, H. Fukuda, T. Watanabe, J. Takahashi, M.
Takahashi, T. Shoji, E. Tamechika, S. Itabashi, and H. Morita, “Microphotonics Devices Based on Silicon Microfabrication Technology,”IEEE J. Select. Topics Quant. Electron. Vol. 11, No. 1, pp. 232–240,
2005.
[3] W. Bogaerts, P. Dumon, D. V. Thourhout, D. Taillaert, P. Jaenen, J.
Wouters, S. Beckx, V. Wiaux, and R. G. Baets, “Compact Wavelengthselective Functions in Silicon-on-insulator Photonic Wires,” IEEE J.
Select. Topics Quant. Electron., Vol. 12, No. 6, pp. 1394–1401,
2006.
[4] H. Fukuda, K. Yamada, T. Tsuchizawa, T. Watanabe, H. Shinojima,and S. Itabashi, “Silicon Photonic Circuit with Polarization Diversity,”
Optics Express, Vol. 16, No. 7, pp. 4872–4880, 2008.
[5] L. Liao, D. Samara-Rubio, M. Morse, A. Liu, D. Hodge, D. Rubin, U.
Keil, and T. Franck, “High Speed Silicon Mach-Zehnder Modulator,”
Optics Express, Vol. 13, No. 8, pp. 3129–3135, 2005.
[6] W. M. Green, M. J. Rooks, L. Sekaric, and Y. A. Vlasov, “Ultra-compact, Low RF Power, 10 Gb/s Silicon Mach-Zehnder Modulator,”
Optics Express, Vol. 15, No. 25, pp. 17106–17113, 2007.
[7] D. M. Morini, L. Vivien, G. Rasigade, J. M. Fedeli, E. Cassan, X. L.
Roux, P. Crozat, S. Maine, A. Lupu, P. Lyan, P. Rivallin, M. Halbwax,
and S. Laval, “Recent Progress in High-speed Silicon-based Optical
Modulators,” Proc. of IEEE 97, Vol. 97, No. 7, pp. 1199–1215, 2009.
[8] D. Ahn, C. Hong, J. Liu, W. Giziewicz, M. Beals, L. C. Kimerling, J.
Michel, J. Chen, and F. X. Kärtner, “High performance, waveguide
integrated Ge photodetectors,” Optics Express, Vol. 15, No. 7, pp.
3916–3921, 2007.
[9] L. Vivien, M. Rouvière, J. M. Fédéli, D. M. Morini, J. F. Damlencourt,
J. Mangeney, P. Crozat, L. E. Melhaoui, E. Cassan, X. L. Roux, D.
Pascal, and S. Laval, “High Speed and High Responsivity Germanium
Photodetector Integrated in a Silicon-On-Insulator Microwaveguide,”
Optics Express, Vol. 15, No. 15, pp. 9843–9848, 2007.
[10] A. W. Fang, H. Park, O. Cohen, R. Jones, M. J. Paniccia, and J. E.
Bowers, “Electrically Pumped Hybrid AlGaInAs-silicon Evanescent
Laser,” Optics Express, Vol. 14, No. 20, pp. 9203–9210, 2006.
[11] J. Van Campenhout, P. Rojo-Romeo, P. Regreny, C. Seassal, D. Van
Thourhout, S. Verstuyft, L. Di Cioccio, J.-M. Fedeli, C. Lagahe, and
R. Baets, “Electrically Pumped InP-based Microdisk Lasers Integrated with a Nanophotonic Silicon-On-Insulator Waveguide Circuit,”
Optics Express, Vol. 15, No. 11, pp. 6744–6749, 2007.
[12] T. Tsuchizawa, K. Yamada, T. Watanabe, H. Fukuda, H. Nishi, H.

Regular Articles

Shinojima, and S. Itabashi, “Si Photonics Platform and Its Fabrication,” Proc. of the 5th International Symposium on Advanced Scienceand Technology of Silicon Materials, pp. 366–370, Kona, Hawaii,
USA, 2008.
[13] T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita,“Low Loss Mode Size Converter from 0.3 μm Square Si Wire Waveguides to Singlemode Fibres,” Electron. Lett., Vol. 38, No. 25, pp.
1669–1670, 2002.
[14] A. Liu, L. Liao, D. Rubin, H. Nguyen, B. Ciftcioglu, Y. Chetrit, N.
Izhaky, and M. Paniccia, “High-speed Optical Modulation Based on
Carrier Depletion in a Silicon Waveguide,” Optics Express, Vol. 15,
No. 2, pp. 660–668, 2007.
[15] Q. Xu, B. Schmidt, S. Pradhan, and M. Lipson, “Micrometre-scale
Silicon Electro-optic Modulator,” Nature, Vol. 435, pp. 325–327,
2005.
[16] W. M. Green, M. J. Rooks, L. Sekaric, and Y. A. Vlasov, “Ultra-compact, Low RF Power, 10 Gb/s Silicon Mach-Zehnder Modulator,”
Optics Express, Vol. 15, No. 25, pp. 17106–17113, 2007.
[17] K. Yamada, T. Tsuchizawa, T. Watanabe, H. Fukuda, H. Shinojima,and S. Itabashi, “Applications of Low-loss Silicon Photonic Wire
Waveguides with Carrier Injection Structures,” Proc. of the 4th IEEE
Intern. Conf. Group IV Photonics, Tokyo, Japan, 2007.
[18] H. Nishi, T. Tsuchizawa, T. Watanabe, H. Shinojima, K. Yamada, and
S. Itabashi, “Compact and Polarization-independent Variable Optical
Attenuator Based on a Silicon Wire Waveguide with a Carrier Injection Structure,” Japanese Journal of Applied Physics, Vol. 49, No. 4,
pp. 04DG20 1–5, 2010.
[19] S. Park, T. Tsuchizawa, T. Watanabe, H. Shinojima, H. Nishi, K.
Yamada, Y. Ishikawa, K. Wada, and S. Itabashi, “Monolithic Integration and Synchronous Operation of Germanium Photodetectors andSilicon Variable Optical Attenuators,” Optics Express, Vol. 18, No. 8,



pp. 8412–8421, 2010.
[20] T. Tsuchizawa, K. Yamada, T. Watanabe, S. Park, H. Nishi, R. Kou, H.
Shinojima, and S. Itabashi, “Monolithic Integration of Silicon-, Germanium-, and Silica-based Optical Devices for Telecommunications
Applications,” IEEE J. Sel. Top. Quant. Electron., Vol. PP, No. 99,
2011 (in press).
[21] S. Park, Y. Ishikawa, T. Tsuchizawa, T. Watanabe, K. Yamada, S.
Itabashi, and K. Wada, “Effect of Post-growth Annealing on Morphology of Ge Mesa Selectively Grown on Si,” IEICE Trans. Elect., Vol.
E91-C, No. 2, pp. 181–186, 2010.
[22] S. Nishihara, M. Nakamura, K. Nishimura, K. Kishine, S. Kimura,and K. Kato, “10.3 Gbit/s Burst-mode PIN-TIA Module with HighSensitivity, Wide Dynamic Range and Quick Response,” Electron.
Lett., Vol. 44, No. 3, pp. 222–223, 2008.
[23] F. Chang, IEEE 802.3av Task Force, Sept. 2008.
http://www.ieee802.org/3/av/public/2008_09/3av_0809_chang_1.pdf[24] R. Kou, K. Yamada, T. Tsuchizawa, T. Watanabe, S. Park, H. Nishi, H.
Shinojima, Y. Ishikawa, K. Wada, and S. Itabashi, “Fast-response,
Wide-dynamic-range Optical Equalisation Based on Silicon Photonic
Platform,” Electron. Lett., Vol. 46, No. 25, p. 1683, 2010.
[25] A. Himeno, K. Kato, and T. Miya, “Silica-based Planar Lightwave
Circuits,” IEEE J. Sel. Top. Quant. Electron., Vol. 4, No. 6, pp. 913–
924, 1998.
[26] M. Kawachi, “Silica Waveguides on Silicon and Their Application to
Integrated-optic Components,” Opt. Quantum Electron., Vol. 22, No.
5, pp. 391–416, 1990.
[27] H. Nishi, T. Tsuchizawa, T. Watanabe, H. Shinojima, S. Park, R. Kou,
K. Yamada, and S. Itabashi, “Monolithic Integration of a Silica-based
Arrayed Waveguide Grating Filter and Silicon Variable Optical
Attenuators Based on p-i-n Carrier-injection Structures,” Appl. Phys.
Express, Vol. 3, pp. 102203-1–3, 2010.

NTT Technical Review

Regular Articles

Tai Tsuchizawa

Hiroyuki Shinojima

Senior Research Engineer, NTT Microsystem
Integration Laboratories.
He received the B.S. and M.S. degrees in physics from Sophia University, Tokyo, and the Ph.D.
degree from the University of Tokyo in 1984,
1986, and 1990, respectively. Since joining NTT
Laboratories in 1990, he has been engaged instudies on ECR plasma technology and its application to an etching process for microfabrication.
His current research interest is fabrication technologies for silicon-based optoelectronics devices. He is a member of the Japan Society ofApplied Physics (JSAP).

Senior Research Engineer, NTT Microsystem
Integration Laboratories.
He received the B.S. and M.S. degrees inapplied physics from Tokyo Institute of Technology and the Ph.D. degree from Muroran Instituteof Technology, Hokkaido, in 1984, 1986, and2009, respectively. Since joining NTT Laboratories in 1986, he has been engaged in studies onmaterial physics and nonlinear optics in semiconductor microcrystals. His current researchinterests include coherent control in silicon,
material physics in low-dimensional semiconductors, and the origin of homochirality in terrestrial bioorganic compounds.

Hidetaka Nishi

Koji Yamada

NTT Microsystem Integration Laboratories.
He received the B.S. and M.S. degrees inmechanical science and engineering from Tokyo
Institute of Technology in 2005 and 2007,
respectively. In 2007, he joined NTT Microsystem Integration Laboratories, where he has been
engaged in research on silicon-based optoelectronics devices. He is a member of JSAP.

Rai Kou

NTT Microsystem Integration Laboratories.
He received the B.E. and M.E. degrees inapplied physics from Waseda University, Tokyo,
in 2007 and 2009, respectively. From 2007 to
2009, he was a visiting researcher at the National
Institute for Materials Science (NIMS), Tsukuba,
Japan, where he worked in the field of nonlinear
optics and its related materials. He joined NTT
Microsystem Integration Laboratories in 2009.
His current research interests are integrated silicon photonic devices. He is a member of JSAPand the Institute of Electronics, Information andCommunication Engineers (IEICE). He received
the JSAP Young Scientist’s Award for the Presentation of an Excellent Paper in 2009.

Senior Research Engineer, NTT Microsystem
Integration Laboratories.
He received the B.E., M.E., and Ph.D. degrees
in nuclear engineering from Kyushu University,
Fukuoka, in 1986, 1988, and 2003, respectively.
Since joining NTT Laboratories in 1988, he has
been engaged in theoretical and experimental
studies on beam dynamics in electron synchrotrons. Recently, he has been engaged in researchon silicon-based nanophotonic structures. He is amember of the Physical Society of Japan, JSAP,
the Atomic Energy Society of Japan, the Particle
Accelerator Society of Japan, IEICE, and IEEE.

Sei-ichi Itabashi

Senior Research Engineer, Supervisor, NTT
Microsystem Integration Laboratories.
He received the B.S. and M.S. degrees in physics from Tohoku University, Miyagi, and the
Ph.D. degree from Hokkaido University in 1982,
1984, and 1998, respectively. Since joining theMusashino Electrical Communication Laboratories of Nippon Telegraph and Telephone Public
Corporation (now NTT) in 1984, he has been
engaged in experimental studies on X-ray and
EUV sources. He has also been engaged in theoretical and experimental studies on highly reflective X-ray mirrors and multilayers. He is currently engaged in studies on silicon photonics
technology. He is a member of JSAP.

Toshifumi Watanabe

Senior Research Engineer, NTT Microsystem
Integration Laboratories.
He received the B.S. and M.S. degrees inapplied physics from Tokyo Institute of Technology in 1982 and 1984, respectively. Since joining
the Musashino Electrical Communication Laboratories of Nippon Telegraph and Telephone
Public Corporation (now NTT) in 1984, he has
been engaged in layout processing studies forelectron-beam pattern writers and for computeraided design data modulation for large-scale
integration and photonic circuits. His current
research interests include robust processing algorithms for very complex pattern layouts.

Vol. 9 No. 5 May 201110

Global Standardization Activities

IPTV Interoperability Events at ITU-T
Masahito Kawamori†
Abstract

This article reports the results of the first Conformance and Interoperability Testing event for IPTV
(Internet protocol television) hosted by ITU-T (International Telecommunication Union, Telecommunication Standardization Sector) in Geneva (July 2010), the second event in Singapore (September 2010),
and the third event in Pune, India (December 2010).

1. Background
IPTV (Internet protocol television) is expected to
become a promising service and global standardization is making progress. IPTV standards produced by
ITU-T (International Telecommunication Union,
Telecommunication Standardization Sector) arebased on various services including NTT Plala’s
Hikari TV service, which started in March 2008.
Many Japanese companies, including NTT, are participating in ITU-T’s IPTV-GSI (Global Standards
Initiative), which is contributing greatly to the global
standardization of IPTV. This was much appreciatedby ITU, which decided to hold events that would promote conformance to Recommendations and interoperability among the implementations of those Recommendations in order to enhance the quality of
ITU-T’s IPTV standards. This is a remarkable decision in ITU-T’s long history of standardization, andthe first Interop event was considered especially significant. This article reports the results the first Conformance and Interoperability Testing (CIT) event for
IPTV hosted by ITU-T in Geneva (July 2010), thesecond event in Singapore (September 2010), and thethird event in Pune, India (December 2010).
At the World Telecommunication Standardization
Assembly (WTSA), held in October 2008 in Johannesburg, the Republic of South Africa, a resolution
was proposed and adopted as Resolution 76 “Studies
related to conformance and interoperability testing,assistance to developing countries, and a possible
future ITU Mark Program” at the request of the† NTT Cyber Solutions Laboratories
Yokosuka-shi, 239-0847 Japandeveloping countries. It states that ITU-T Study
Groups should develop the necessary conformance
testing Recommendations for telecommunicationequipment as soon as possible and that ITU-T Recommendations to address interoperability testing
shall proceed as quickly as possible. On the basis of
this resolution, Japan proposed to develop a draft
Recommendation for CIT. This contribution was discussed in Study Groups SG11, SG13, and SG16 andresulted in the creation of Joint Coordination Activities of Conformance and Interoperability Testing(JCA-CIT). Following this move, during the IPTVGSI events, Question 13 of SG16 (Q13/16) drafted
CIT Recommendations. At the IPTV-GSI event heldin January 2010, it was agreed that the first CIT event(called Interop) would be held in July 2010 in Geneva. At the IPTV-GSI event in May 2010, companies
were invited to participate in the upcoming event. To
prepare for the first Interop event, Q13/16 had anelectronic meeting almost every week until July 2010
to facilitate progress on the CIT Recommendations.
2. 1st Interop in Geneva
After six months of preparation, the first Interop
event for testing conformance and interoperability for
IPTV Recommendations was held on July 20 to 23,
2010, as scheduled, at the ITU headquarters buildingin Geneva, Switzerland (Photo 1). This was the firstever interoperability event organized by ITU, andmuch attention was paid to this historic event, as it
was called by Malcolm Johnson, the Director of
ITU-T’s Telecommunication Standardization Bureau(TSB).
The Interop event itself consisted of two parts: theNTT Technical Review

Global Standardization Activities

first two days were devoted to conformance andinteroperability testing (CIT event). This testing was
not open to the public, but only to those companies
that registered as event participants. The remaining
two days were an open showcasing event, to which
many individuals and companies were invited to witness the implementations of ITU-T IPTV Recommendations. Special provision was made for regulators and government agencies that had requested andregistered beforehand for one-on-one discussions
with the presenters at the showcasing event to enable
them to have a special tour of the showcased solutions. NTT participated in the closed CIT event aswell as the open showcasing event.
2.1 C onformance and interoperability testing(CIT event)
The Recommendations tested in Geneva are listed
in Table 1.
H.721 is a Recommendation for IPTV terminal
devices, initiated by an official contribution fromJapan and based on specifications for IPTV terminals

Photo 1. “ Dr. Hamadoun Touré, ITU Secretary-General,
addressing at the first ITU-T Interop event on
IPTV in ITU Headquarters”.

actually implemented and deployed for IPTV services in Japan. It defines the requirements for the basic
IPTV services, which include video on demand, Linear IPTV (also known as channel service), and interactive applications (IPTV portal).
H.750 specifies metadata. Many of the metadata
elements defined in this Recommendations are
already used in Japan. H.750 also includes metadata
specified by ATIS (Alliance for Telecommunication
Industry Solutions) IPTV Interoperability Forum(IIF).
H.762 (Lightweight Interactive Multimedia Environment; LIME) is a Recommendation in the MAFR
(Multimedia Application Framework) series, whichenables interactive applications and IPTV portals.
This Recommendation was also based on contributions from Japan. The technology defined in H.762 iscurrently used in Hikari TV, NTT’s IPTV service.
H.770 specifies how an IPTV terminal device candiscover service providers and services, an essential
mechanism for a standard IPTV service. It was initiated by contributions from Europe, but many contributions were also made by Japanese and Korean
companies. As a result, H.770 is harmonized withservice discovery specifications of IPTV Forum
Japan and ATIS-IIF as well as those of digital video
broadcasting (DVB).
At the first CIT event, Sumitomo Electric Networks, OKI, NEC, Mitsubishi Electric, and NTT
were represented. These companies tested conformance to the requirements of the abovementioned
Recommendations and interoperability among theimplementations of those Recommendations on thebasis of those Recommendations themselves and the
newly created CIT Recommendations. Although theJapanese companies simply brought servers and terminals that are already deployed in Japan and implement those Recommendations for IPTV, the results ofthe conformance testing were excellent and interoperability was well proven. This shows the accuracy of
their implementations as well as the quality of their

Table 1. Recommendations tested at the Interop event in Geneva.
Recommendation title

Rec. no. Approving SG Completion date1 Content delivery error recovery for IPTV services

H.701

SG16

2 IPTV terminal devices: Basic model

H.721

SG16

Jan. 2008

3 High-level specification of metadata for IPTV services

H.750

SG16

Mar. 2009

4 Lightweight Interactive Multimedia Environment for IPTV service (LIME)

H.762

SG16

Nov. 2009

5 Mechanisms for service discovery and selection for IPTV services

H.770

SG16

Aug. 2009Vol. 9 No. 5 May 2011

Jan. 2008

Global Standardization Activities

products. It also shows the maturity of the Recommendations themselves. Sumitomo Electric Networks, in particular, stood out in testing its products
against all of the abovementioned Recommendations
and achieving excellent results. This was truly aremarkable feat.
The checklists used in the testing were collected
and made into test templates, which in turn will be
used to improve the quality of Recommendations, as
deemed necessary. Some of the abovementioned Recommendations were amended on the basis of theresults of the first CIT event. This shows that CIT
events are not just a showcase, but also an importantpart of the standardization process, which ensures thequality of standards, as well as providing the practicalbenefits of a test center.
2.2 Showcasing event
The remaining days, July 22 and 23, were dedicatedto the showcasing and exhibition of IPTV products
based on ITU-T standards to publicize and promote
the general understanding of what ITU is doing withrespect to IPTV standardization.
In addition to the previously mentioned Japanesecompanies, Cisco System (USA), TVSTORM (South
Korea), and the Pontifical University of Rio de Janeiro (Brazil) participated in the showcasing event.
Photographers and TV crews at the Interop event
site recorded the event and provided promotional
content on YouTube.
Government agencies as well as companies from
China, Japan, Indonesia, Singapore, Kenya, India,
Turkey, Tunisia, Cote d’Ivoire, Italy, France, Germany, Australia, etc. around the globe came to see thedemonstrations of standards-based IPTV. Interest
among the developing countries was especially
impressive. European companies, for whom it was
the first time ever to see ITU-T’s IPTV standards,
were also impressed by the demonstrations, so muchso that some of them started discussing how to deploy
IPTV services using the showcased products.
On July 22, we had the honor of receiving Dr
Hamadoun Touré, the Secretary General of ITU, who
made the welcome address to all the participants andvisitors at the event. During the address, he emphasized ITU’s seriousness concerning CIT events ingeneral, stating that this IPTV Interop event was ahistoric occasion, being the first event of its kind, andwill be followed by CIT events for the Next Generation Network (NGN) and other topics.
One of the most important things to note about thisIPTV Interop event is that many international organiPhoto 2. L
 IME application for e-health on ITU-T IPTV
showcased by NTT (copyright: I2R and NTT).

zations, some part of the United Nations, were invited. Especially significant was the participation of the
Deputy Director of the European Broadcasting Union(EBU) and the Director of Intellectual Property at theWorld Intellectual Property Organization (WIPO).
EBU is influential in various matters, including standardization, regarding the broadcasting world ofEurope, and the fact that EBU recognized ITU-T’s
Recommendations as the first global standard on
IPTV gives them considerable weight. With thisevent, EBU and ITU-T have agreed to even closer
collaboration, which resulted in the joint workshop
on accessibility for IPTV in November 2010. WIPO
is a United Nations agency that is influential in copyright management, and it was very significant that
WIPO recognized for the first time ITU-T IPTV as alegitimate medium for broadcast content.
NTT demonstrated interactive content created incooperation with the Institute for Infocomm Research(I2R) in Singapore and compliant with H.762 (LIME)
on an H.721-compliant TV set already available on
the market. This was the first time ever for an application complying with H.762 (LIME), which wasapproved in 2009, to be demonstrated in Europe,
where digital TV sets with IP connections are not yet
popular. Since there is no standard interactive platform widely used in Europe, LIME applications(Photo 2) were received with interest. Moreover,many observers from developing countries were
impressed with LIME, which they saw for the firsttime.
The guest visitors were all impressed by the level of
implementations, especially those of the Japaneseparticipating companies, and it was truly significant
NTT Technical Review

Global Standardization Activities

Table 2. Newly created CIT documents based on Interop results.
Document title

No.

Approving SG Completion date1

Technical Paper: Conformance Testing Specification for H.721
HSTP.CONF-H721(formerly H.IPTV-CONF.2)

SG16

July 2010

2

Technical Paper: Conformance Testing Specification for H.721
HSTP.CONF-H762(formerly H.IPTV-CONF.6)

SG16

July 20103

Technical Paper: Conformance Testing Specification for H.770
HSTP.CONF-H770(formerly H.IPTV-CONF.7)

SG16

July 2010that the companies participating in the CIT event
were able to demonstrate the maturity of ITU-T Recommendations for IPTV as well as the high quality of
the implementations from an international viewpoint,
in Geneva, one of the major centers in Europe.
2.3 R elationship between Interop event and Recommendations
The Geneva Interop results will be reflected in the
CIT documents for Recommendations H.721, H.762,
and H.770 and in those Recommendations themselves (Table 2). The changes to the Recommendations received consent at the SG16 Plenary meetingon July 30, 2010. Thus, the CIT event has been instrumental in improving the quality of current Recommendations for IPTV, a point that was well emphasized by ITU-T.
3. 2nd Interop in Singapore
3.1 Overview
The second IPTV Interop event took place on September 20 through 27, 2010, in Singapore as part of
the IPTV-GSI event. The venue was provided by I2R,
which belongs to the Agency for Science, Technology
and Research (A*STAR) at Fusionopolis next toBiopolis, which is famous as the center of Bioscience
research in Singapore. Conformance testing took
place there on September 23 and 24, while the 27th
was dedicated to an open showcasing.
Fusionopolis and Biopolis were created by A*STARwith the aim of making Singapore into a global hub
for research on information, telecommunications,sciences (such as physics, chemistry, and biology),
and engineering. Biopolis and Fusionopolis areworld-renowned research institutes, as witnessed by
the fact that they have been featured in an NHK TV
program. The venue was in the academic center ofSingapore. Biopolis is next to the National Universityof Singapore and the Nanyang Technical University,
while Fusionopolis is next to the Singapore campus
Vol. 9 No. 5 May 2011of INSEAD, a famous European business school.
More and more developments are expected in thisarea, which will certainly become the brains of Singapore. NTT R&D laboratories have been engaged incollaborative research with A*STAR, and the resultof the joint work was also demonstrated at the Interop
event.
The Singaporean government expressed strong
interest in this event and gave essential support. At
the open showcasing event on September 27, Leong
Keng Tai, Director-General (Telecoms and Post) of
the Infocomm Development Authority (IDA), welcomed participants and took a tour of the exhibitionand observed the quality of ITU-T Recommendations
for IPTV. This tour was also joined by Philip Heah,
who heads the work on Next Generation Nationwide
Broadband Network (NGNBN), and Raymond Lee,
who is in charge of standardization at IDA.
Participants in this Interop event included Sumitomo Electric Networks, OKI, NEC, Mitsubishi Electric, and NTT from Japan, Panasonic Singapore andtwo other companies from Singapore, and two Korean companies.
Testing was conducted mainly on H.721 (IPTV
terminal devices: Basic model) and H.701 (Content
delivery error recovery for IPTV services). All theJapanese companies performed very well, showing
their high quality. One Korean company also participated in the testing for the first time, in testing for
H.770 (Mechanisms for service discovery and selection for IPTV services).
The main purpose of this Interop event was qualityof experience (QoE) for IPTV services. Sumitomo
Electric Networks, who led the discussion on H.701,
the basic Recommendation for QoE, showed an endto-end solution for IPTV service. They especiallyemphasized the high quality of Hikari TV IPTV service. Mitsubishi Electric also showed high-definition
content. In Singapore, there is currently strong interest in the quality of content, as can be seen from thearticles in newspapers that daily report on the qualityGlobal Standardization Activities

of service of their current IPTV service. The Interop
event and its stress on quality was very relevant andwell received by the guests to the event, including thegovernment.
NTT demonstrated LIME content again, this timechoosing an e-health application on the ITU-T IPTV
platform. In the demonstration, data collected bydevices for measuring body weight and blood pressure through the FLET’s Phone as a gateway wasgraphed on the fly by the LIME application on an
IPTV compliant with ITU-T standards. These measuring devices are already available on the market,
and the participants from the Singaporean government seemed to be impressed with the demonstration.
As the Singapore government has been emphasizing
the importance of e-government, and IPTV in particular is considered to provide the user interface forsuch services, it was good for NTT to be able to demonstrate such a solution by using retail products. The
fact that this demonstration was also based on collaborative work between NTT and A*STAR made it
more meaningful to the local audience.
3.2 Results
As a result of the Interop event in Singapore, H.
IPTV-CONF.1, the conformance and interoperability
document based on H.701 was updated.
4. Third Interop Event in Pune, India
The third Interop event was held in Pune, near
Mumbai, in India on December 15–17, 2010. It was
co-located with ITU-T Kaleidoscope and IPTV-GSI.
It was partially supported by the Indian government.
Important representatives from major companies inIndia, such as the chairman of BNSL and representatives from Bollywood studios, came to the open
showcasing event on December 17 and saw ITU-T’s
standard IPTV in action. The event was videoed byBloomberg TV and broadcast to more than a million
subscribers. It was notable that during the event the
representative of the Indian government stated thatthey are considering ITU-T Recommendations as thenational standard for IPTV in India.
5. Conclusion
ITU, led by TSB Director, Malcolm Johnson, hasbeen vigorously working on conformance andinteroperability testing, and Interop events havebecome important activities, as can be seen from themany references made to them in the news media. As
we have seen, the CIT results will be reflected in theexisting Recommendations, and participating companies can list products confirmed to be compliant with
the Recommendations in the CIT database on the
ITU-T website. Companies that want to purchase
IPTV products compliant with ITU-T Recommendations can go to the database and easily find suitablevendors.
In 2011, several countries, including Brazil and theUnited Arab Emirates, expressed interest in hosting
Interop events. ITU-T is also planning to promote
LIME (H.762) and other application platforms byhosting an Application Contest Event, along with an
Interop event, during this year’s ITU Telecom.
NTT R&D will not only actively participate inthose events, but also proactively lead their management, thereby promoting international standards
based on contributions based on NTT technologies.

Masahito Kawamori

Senior Research Engineer, NTT Cyber Solutions Laboratories.
He joined NTT Laboratories in 1989. He has
worked in research areas such as artificial intelligence, language processing, and interactive
agents using speech recognition. His current
research area is metadata and rights language,
media delivery for broadcasting and broadband
communications with special emphasis on IPTV,
and the convergence of fixed and mobile communications services. Since 2000, he has been
the leader of the Metadata Task Group of the
Association of Radio Industries and Businesses(ARIB) Working Group for Broadcasting Systems based on a Home Server. He is involved in
IPTV standardization work in ITU-T and is the
Rapporteur of Q13/16 and the IPTV-GSI TSRCoordinator.



NTT Technical Review

External Awards
Best Presentation Award
Winners: Kevin Duh and Ching-man Au Yeung, NTT Communication Science Laboratories
Date: Feb. 25, 2011
Organization: 12th International Conference on Intelligent Text
Processing and Computational Linguistics
For “Providing Cross-Lingual Editing Assistance to Wikipedia
Editors”.
The 26th TELECOM System Technology Award
Winners: Hiroyuki Funakoshi and Tatsuya Matsukawa, NTT Service
Integration Laboratories
Date: Mar. 22, 2011
Organization: The Telecommunications Advancement Foundation
For “A Failure Rate Estimation Considering the Change in the
Number of Equipment”.

Published in: IEICE Trans. on Commun., Vol. J93-B, No. 4, pp.
681–692, Apr. 2010.
For “A Simple Estimation Method of Network Reliability with
Failure Scale”.
Published in: IEICE Trans. on Commun., Vol. J88-B, No. 8, pp.
1444–1453, Aug. 2005.
For “Analyzing Failure Frequency and Severity in Communication
Networks”.
Published in: Proc. of the 56th Annual Reliability and Maintainability Symposium (RAMS 2010), Jan. 2010.
For “Unavailability Evaluation Method for Communication Network Management”.
Published in: Proc. of the 55th Annual Reliability and Maintainability Symposium (RAMS 2009), Jan. 2009.

Papers Published in Technical Journals andConference Proceedings
Simultaneous Enlargement of SRAM Read/Write Noise
Margin by Controlling Virtual Ground Lines
H. Makino, T. Kusumoto, S. Nakata, S. Mutoh, M. Miyama, T.
Yoshimura, S. Iwade, and Y. Matsuda
Proc. of NEWCAS 2010, the 8th IEEE International Conference,p. 73, Montreal, Quebec, Canada.
The SRAM operating margin in 65-nm technology is analyzed.
The peak characteristic in the read margin versus supply voltage wasfound to be caused by the channel length modulation effect. Controlling the memory cell virtual ground line proved to be effective inenlarging the operating margin simultaneously in the read and write
operations. A simple optimum circuit that does not require any
dynamic voltage control and achieves an operating margin comparable to conventional circuits that do require dynamic voltage control
is proposed.

Efficient Data Selection for Spoken Document Retrieval
Based on Prior Confidence Estimation Using Speech andContext Independent Models
S. Kobashikawa, T. Asami, Y. Yamaguchi, H. Masataki, and S.
Takahashi
Proc. of Spoken Language Technology Workshop (SLT), 2010,
IEEE, pp. 200–205, Berkeley, CA, USA.

This paper proposes an efficient speech sample selection techniquethat can identify those samples that will be well recognized. Conventional confidence measures can identify well-recognized speechsamples, but they require speech recognition to estimate confidence
scores. Low-confidence speech samples should not undergo recognition since they yield speech documents that will eventually berejected. The proposed technique can select the samples that will
justify the application of speech recognition. It is based on rapid priorconfidence estimation by using speech and context independent models to calculate acoustic likelihood values on a frame-by-frame basis.
Tests show that the proposed confidence estimation technique is over
50 times faster than the conventional posterior confidence measure
while maintaining equivalent data selection performance for speech
recognition and spoken document retrieval.

Fault Recovery Performance Analysis of Functionally Distributed Transport Networking System
K. Ogawa, K. Higuchi, and S. ChakiIntelligent Networking, Collaborative Systems and Applications(INCOSA), Springer, Vol. 329, pp. 281–295, 2011.
We propose a fault recovery method in functionally distributed
transport networking that separates the control-plane processing part(control element (CE)) from the forwarding-plane processing part

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings(forwarding element (FE)) of the router. In this architecture, one
path-control process in the CE consolidates and processes the pathcomputations and the path settings for multiple FEs. This leads to a
reduction in path-control complexity and efficient operation of largescale networks. On the other hand, it is absolutely critical to ensure

Vol. 9 No. 5 May 2011

the high reliability of the CE. We analyze the performance of the
proposed fault recovery method by using a software implementation.

