NTT Technical Review
October 2014 Vol. 12 No. 10
View from the Top
Toshihiko Kumamoto, Senior Executive Vice President, NTT WEST
Taking on the Market with Vision—Using Brand Power to Pioneer
Novel Services

Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure
Maintenance and Management Technology for Safe, Secure, andEconomical Operation of Telecommunication Infrastructure Facilities
Facilities Management Technology for Optimizing Inspection andRepair Timing
Protecting Telecommunication Services from Earthquake Damage
Technology for Highly Efficient and High Quality Diagnosis ofInfrastructure Facilities
Repair and Reinforcement Technology for Safe and Secure Concrete
Structures that Have a Long Service Life
Effective Repair and Reinforcement Technology for Conduit Facilities

Regular Articles
Frequency-division-multiplexing Coherent OTDR for Realizing Effective
Construction and Maintenance of Submarine Optical Cable Systems
Development of Long-span Aerial Cable Installation Technique (Long
Hanger Method)

Global Standardization Activities
IEC Standardization Trends Related to Energy Infrastructure

Global Activities of NTT GroupNTT Com Security

Practical Field Information about
Telecommunication Technologies
Signal Generator for Noise Search Tester to Improve Noise-measurement
and Noise-identification Skills

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

View from the Top

Taking on the Market with Vision—
Using Brand Power to Pioneer Novel
Services
Toshihiko Kumamoto, Senior Executive
Vice President, NTT WEST
Overview

NTT WEST is executing a variety of measures to survive and thrive inmany highly competitive areas. It is involved in a series of new projects
such as Smart Hikari Town in various regions in Japan having diverse
cultural and social needs. We asked Senior Executive Vice President
Toshihiko Kumamoto about the frame of mind that NTT WEST must
adopt to ensure growth going forward.
Keywords: management policy, smart city, ICT

Smart Hikari Town project got off to a good start—Mr. Kumamoto, please tell us about the company’s
current endeavors in western Japan.
At present, there are more than 8 million subscribers to the FLET’S HIKARI optical broadband service
at NTT WEST. We have set a target of 9 million subscribers, and to this end, we are engaged in providing
a variety of price plans and a diverse lineup of services. In addition, I feel that we, as a company, havegreat potential—there are still many things that we
can accomplish.
Our work from here on will not simply be thedeployment of more optical fiber networks. Rather, it
will be to help solve all sorts of problems and issues
within the home and the company by making full use
of our technologies. In short, we want to make ourtechnologies useful in diverse scenarios of everyday
life including education and shopping, emergency/
disaster response, and implementation of energy-saving methods.

—Smart Hikari Town seems to be an example of using
those technologies in a comprehensive manner.
That’s right. Let me tell you about Smart Hikari
Town Kumamoto as a showcase example of that.
In 2012, NTT WEST entered into a “comprehensive cooperation agreement for regional revitalization
through ICT (information and communication technology) utilization” with Kumamoto Prefecture andKumamoto City as part of a plan to stimulate regional communities and improve community services.
Through this project, we aim to collaborate with local
residents on improving community services andachieving a new style of information distribution
using ICT. We will explore ideas such as the use of
television (TV) technology to monitor elderly people
or children who need constant nursing care, and thevisualization of current service conditions in municipal bus and railway systems.
In this project, information belonging to the local
government and data submitted by residents such as
posts in social networking services and word-ofmouth information will be collected and stored on the
NTT Technical Review

View from the Top

cloud based on a geographic information system.
This huge volume of data in different formats that wecall “big data” will be combined and visualized in aform useful for city management. Our target is urban
development based on efficient and effective towntype clouds.
This project has gotten off to a smooth start for two
main reasons. First, Kumamoto City, among many
local governments, is a prefectural capital that has an
appropriate scale in terms of population and area.
Second, the governments of Kumamoto Prefecture
and Kumamoto City have been extremely cooperativein this pioneering endeavor. In this experiment, it will
be necessary to test the usability and other aspects ofthis smart city from diverse viewpoints. These will
include our viewpoint as preparers of this environment and the viewpoints of users such as managers ofretail stores and their customers.
Actually, we have already collected opinions ofpeople living in the smart city and those of people
visiting as tourists and have received comments inline with our expectations as well as comments that
we did not expect at all. Some people commented on
how they enjoyed the town guidance provided by theregion’s character mascot named “Kumamon,” butothers voiced concerns about convenience.
Importance of generating interest in NTT WEST
technologies
I believe it is important that we get our customers
interested in the services and technologies of NTT
WEST, and hearing comments such as “It’s interesting!” and “It’s fun!” is a good place to start. From theviewpoint of users, it should be easier to become
familiar with services and technologies that are interesting and fun to use.
In this regard, NTT Solmare, a subsidiary of NTT
WEST, is in the business of delivering content such as
e-books (electronic books) and dating games oriented
to smartphones, personal computers, and tablets. This
year marks the tenth anniversary of its “comic
CmoA” e-comic delivery service that has become oneof Japan’s long-standing top-level sites. It has growninto a hugely popular site focused on worldwide
delivery of e-comics. NTT may have an image ofbeing serious and rigid, but our young employees hadlots of fun working out ways of displaying cartoon
balloons on the screen of a smartphone.
—Where did this unique approach of NTT WEST
originate?
Vol. 12 No. 10 Oct. 2014

Each of the 30 prefectures in which NTT WEST
provides services includes competing operators. We
therefore find ourselves in severe competition withother companies in the Internet communications
business, so we regularly have to start various new
endeavors in order to maintain a competitive edge. To
effectively cover a wide area with many cultural andlifestyle differences, we must first of all provide ahigh-quality network and other telecommunication
infrastructure facilities on a uniform basis. Then, in
terms of services, we must make sure that the sales
department obtains a firm understanding of the features and needs of each individual area.
We are fortunate to have high brand power in thename NTT WEST that has been nourished since thedays of Nippon Telegraph and Telephone Public
Corporation. This brand is associated with a “sense of
security,” that is, an awareness of NTT WEST as acompany that will never disappoint its customers
when it comes to technology and services. It’s truethat customers sometimes make comments to theeffect that “fees are too high,” but this can also betaken to mean that they are using NTT WEST services with confidence and expecting us to work
harder to reduce costs.
When sales personnel visit a potential customer for
the first time, the familiarity of the NTT WEST brandmeans that we are almost never turned away at thedoor and enables us to at least present our proposal toa receptive audience. This is testimony to the trustthat customers place in NTT WEST compared withother operators. In addition, we have inherited NTT’s
long-time reputation of providing “bridges.” We havea strong sense of mission to restore telecommunication facilities as quickly as possible when a natural
disaster or other mishap occurs so that customers cancontinue to enjoy services.
View from the Top

With this brand power and worthy mission in hand,
we venture forth into the market, but to survive thesevere competition that I mentioned, we must create
new value such as smart cities and e-comics.
We still have great potential as a company—taking
on the market with vision—In the end, the foundation to such novel services istechnological expertise. What message would you
have for NTT researchers?
I believe that we have great latent abilities including untapped strategies. As for issues that we need toaddress, price will always be a matter of concern, but
it’s technology that supports services and productquality. Technology is continuously evolving, and wemust make sure to introduce it in a timely manner to
respond effectively to customer needs. It is you, ourresearchers, who support this technology. I would ask
you to keep your eye on the market at all times and to
take up the challenge of developing innovative technologies with a sense of vision.
Of course, we at NTT WEST must also face themarket with vision and discern customer needs.
Going forward, I would like all of us to work together
to create convenient, low-cost, and high-quality prod-

ucts. For example, while Japan has achieved a globally high penetration of infrastructure facilities for
optical fiber networks, we would like to see more
research and development (R&D) done to ensure thatthe repeater span-length in an optical transmission
can be even longer, that the circuit can be switchedwithout interrupting services, and that the network
configuration can be simplified.
In addition, the growth in the use of optical broadband service for the home is slowing, so we are very
interested in R&D that will enable a greater use ofbidirectional communication via TV and Internet
lines. We are also interested in the delivery of 4K/8K
ultra high-definition video. I’m sure all of you
remember the impact of converting from analog todigital media a while back, but I would now like you
to pour your efforts into R&D of high-presence video
that will generate an even greater impact on users. On
our side, we will take a proactive approach to using
events such as public viewings as opportunities for
exposing our customers to your research achievements.
A change of pace is important—taking a break canraise performance!
—What is important to you in your work?
Today, ICT is more than just a communication
tool—it has become an essential means of making
our everyday life easier and our business activities
smoother. For this reason, I’m sure that the importance of ICT and the convenience that it provides willcontinue to increase in the years to come. On theother hand, ICT has given birth to conditions in which
we are always in contact with someone; that is, we arealways in an “active” state. They say it is now difficult
to make “downtime” for ourselves in which we canrelax and catch our breath.
A 24-hour day is provided equally to all. How those
24 hours are utilized depends, of course, on the individual. For me, dividing up that limited amount oftime into active and downtime states is very important. The time that we have to concentrate heavily on
things is not really as long as we might think.
Moreover, keeping our attention on one thing fromone angle may cause us to miss other things of importance. I believe that adding some variety in one’s lifeand changing one’s viewpoint and mood from time totime will bring unexpected ideas to the surface. If we
don’t employ some foresight not only on a day-to-day
basis but also over several days or even several

NTT Technical Review

View from the Topmonths, I think it will be difficult to allocate time in asatisfactory manner.
— Mr. Kumamoto, can you leave us with a message
for all NTT WEST employees?
Putting the things that you are involved in to gooduse in society—such as making the technology thatyou develop into practical products, turning yourdesigns into actual facilities, and getting our customers to actually use the fruits of our efforts—is one of
the great blessings of work. At the same time, relationships with colleagues with whom you work can
deepen with each passing year, and the number ofpeople that can come to your aid in times of emergencies can increase. For me, this is the joy of living!
I believe that I would not be where I am today if I
did not have such bonds with people. Forming longtime associations with people both inside and outside
the company and from a variety of backgrounds can
support your individual growth. I would like everyone to put the formation of relationships with all
kinds of people regardless of their age or position at
the top of their agenda.

Vol. 12 No. 10 Oct. 2014

Interviewee profile
Career highlights
Toshihiko Kumamoto entered Nippon Telegraph& Telephone Public Corporation in 1980. After
serving as Senior Manager of the Planning
Department and Director of Personnel Department
No. 2 at NTT WEST and as Manager of the NTT
WEST Kumamoto Branch, he became Presidentof NTT West Home Techno Kansai in 2008, NTT
WEST Senior Vice President Tokai Regional
Headquarters and Manager of the NTT WEST
Nagoya Branch in 2010, and NTT WEST SeniorVice President and General Manager of the
Network Department, Plant Headquarters in
2012. He assumed his present position in June
2014.



Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure

Maintenance and Management
Technology for Safe, Secure, andEconomical Operation of
Telecommunication Infrastructure
Facilities
Fumihide Sugino and Hiroshi Masakura
Abstract

The conduits, manholes, tunnels, and other telecommunication infrastructure facilities that support
optical access networks are aging rapidly, just as roads, bridges, and other elements of the social infrastructure are. The ability of these facilities to withstand large-scale earthquakes is also a major concern.
These Feature Articles describe the latest technical trends in facilities management, inspection and diagnosis, repair and reinforcement, and technology for making facilities resistant to earthquake damage aspart of efforts to achieve safe and secure telecommunication infrastructure facilities as well as economical maintenance.
Keywords: telecommunication infrastructure facilities, maintenance and management, age deterioration

1. Introduction
The aging of roads, bridges, tunnels, and other elements of the social infrastructure is becoming asevere social problem. Dealing with this problem isan urgent matter for governments at the national andlocal levels and the enterprises that manage infrastructure facilities. However, the huge cost and insufficient number of technicians are hindering an early
solution. Furthermore, there is no systematic knowledge or standard technology for dealing with aging
infrastructure facilities, so managers of the facilities
are left to devise measures individually. Accordingly,
there is a growing expectation by governments andsociety as a whole for the development of technology
to address the problem. Another equally important
problem is the need to strengthen facilities against
major earthquakes. The probability of a Nankai
Trough earthquake or an earthquake directly beneath
the Tokyo area is high, and the resulting damage toinfrastructure facilities, especially facilities deteriorated by age, would be immeasurable.
NTT telecommunication infrastructure facilities,
including conduits, manholes, and tunnels, would not
escape that damage. For example, about 80% of the
manholes will be over 50 years old (the service life
for such facilities) by 2030 (Fig. 1). Currently, 80%of the existing conduit is not equipped with earthquake resistance measures, and the problems that
require solutions are mounting. In developing new
business on the B2B2C (Business-to-Business-toConsumer) model, NTT is pressing forward with the
expansion of optical access systems, and having safe
and secure telecommunication infrastructure facilities is important in order to provide stable support ofsuch NTT services.
Research on telecommunication infrastructure
facilities at the NTT Access Network Service Systems Laboratories has spanned many years, and weare applying the technology and research expertise
NTT Technical Review

Feature Articles

Manholes (680,000)

NTT
building

Proportion of facilities
50+ years old
100%
80%
60%
40%
20%
0%
2010
2020
2030

Bridge-supported conduit:
36,000 sites
Special-purpose bridges:
3000 sites
Customerbuilding

By 2030, at least 80% of manholes will beover 50 years old.
Utility poles (12 million)

Conduit attached to bridge
Conduit
TunnelManholeConduit (620,000 km), section length (110,000 km)
Tunnels (650 km)

100%

Proportion of facilities
50+ years old

NTT conduit earthquake preparation
Prepared18%
110,000 km

80%

Not
prepared82%
510,000 km

60%
40%
20%
0%
2010 2020 2030 2040

80% of conduit was designed on old standards and has no antiearthquake measures.
*Conduit constructed before 1985 without elastic joints

Fig. 1. Telecommunication infrastructure facilities.

we have developed while gathering knowledge
acquired by other NTT laboratories and other companies to solve such problems.
2. Direction of research and development(R&D) related to telecommunication
infrastructure facilities
The NTT Access Network Service Systems Laboratories is concentrating on developing maintenanceand management technology for safe, secure, andeconomical maintenance of telecommunication
infrastructure facilities. By making the results of thatwork widely applicable to infrastructure facilities inJapan and other countries, rather than only within
NTT, we hope to contribute, if only to a small degree,
to solving a problem faced by society in general.
In our R&D on maintenance and management technology, we are going beyond the conventional
research topics such as repair procedures and tools
for inspection and diagnosis, by taking an overall
Vol. 12 No. 10 Oct. 2014

view of the maintenance and management performed
by NTT business companies and working on moreinnovative management strategies. We cannot keep
up with the rapid aging of a huge number of facilities
by increasing the efficiency of individual inspection
and repair tasks alone. We can see by looking at themaintenance and management cycle (Fig. 2) that aradical change is needed. We are focusing on thischallenge from the three viewpoints described
below.
2.1 F
 acility-specific management techniques
based on prediction of degradation and damage
The plan used to manage the entire maintenanceand management cycle is based on facility management criteria such as inspection interval, inspection
items, confirmation of degradation, and the timing of
repair and reinforcement work. However, most of
those criteria were set with reference to general structures that existed at the time the telecommunicationFeature Articles

Repair & reinforcement
Maintenance planning

Current problems• Increasing number of facilities that need repair &reinforcement (increasing costs)

Current problems• Uniform management criteria for all facilities(inefficient)

R&D• Economize repair & reinforcement procedures by
R&D
local reinforcement.
Maintenance• Optimum management to match actual states of• Maintenance-free with long-life materials
facilities, e.g., individual risk-basedplanning
Repair &management criteria for each facility(management criteria
reinforcement& procedures)
Remove from cycle byachieving maintenance-freefacilities.
Inspection & diagnosis

Diagnosis

Current problems• Huge amount of inspection
work• Fewer skilled technicians• Limits of inspection quality by humans• Accidents during inspection

Inspection

Aim for efficient maintenance andmanagement cycle operations throughinnovative facilities management.
R&D• Inspection automation• Diagnosis of facility soundness• Inspection efficiency throughscreening and constantmonitoring

Advanced inspection and diagnosis technology removes
hindrances in the maintenance and management cycle.

Fig. 2. Maintenance and management cycle and R&D efforts.

infrastructure facilities were constructed, a time whenawareness of maintenance and management was relatively low. The criteria are even ambiguous as a basis
for engineering. The NTT Access Network Service
Systems Laboratories is proceeding with R&D on
facilities management technology for revising suchmanagement criteria for NTT facilities to match current maintenance needs.
For example, even for facilities that were constructed with specifications that are nationally uniform, thedegree of deterioration from aging, the earthquake
damage rate, and the impact of facility failure can allvary with the facility environment. Our objective,
therefore, is to create a more efficient maintenanceand management cycle achieved by using detailed
criteria that take the conditions of individual facilities
into account instead of using uniform criteria for all
facilities.
Achieving that objective requires technology forevaluating the states of individual facilities and forpredicting degradation and damage. Such predictions
can be made by understanding the mechanism ofdeterioration with age, identifying points that are
weak against earthquake damage, and analyzing theenormous amount of accumulated inspection data.
Doing so would make it possible to set priorities and

optimize timing for facility inspection, repair, andimplementation of earthquake countermeasures. It
would also become possible to examine the inspection items and procedures for each facility in moredetail.
When all facilities are new, the total repair cost canbe effectively held down by considering the life cycle
cost and inspecting all of the facilities uniformly, andby repairing facilities whenever slight degradation
was found. However, under conditions where all
facilities are aging, such as the conditions that exist
now, facilities management must consider the risk offacility failure as well as the total repair cost. The
objective of the NTT Access Network Service Systems Laboratories is to establish a management
method that takes the probability of facility failure
and the effects of a failure into consideration [1] [2].
2.2 I nspection and diagnosis automation withimages and sensors
The aspect of maintenance and management thatmost requires skilled technicians is facility inspection. Inspection is difficult because the number offacilities is immense, facilities are spread widely
across the country, and they are installed under roads
and on bridges. With the declining number of skilled
NTT Technical Review

Feature Articles

technicians, inspection has become the primary causeof delays in the maintenance and management cycle.
Also, the ceiling collapse in the Sasago Tunnel
spurred a move toward stricter inspection of thenation’s facilities. As a result, NTT business companies now regard improvement of inspection efficiency
and quality as the most important problem in terms of
maintenance and management.
We are working on ways to solve that problem bydeveloping technology for automating the inspection
work that is now performed using human vision andtouch. This technology includes the use of image
processing, sensors, and robots. In addition to the
obvious objective of higher efficiency, we are also
targeting inspection results that are more accurate
without depending on the skill of the technician,inspection of parts that cannot be seen by humaninspectors, and diagnosis of facility soundness using
ways that cannot be done by human inspectors.
Inspection automation can also effectively increase
worker safety by reducing the work done by humans
at dangerous sites such as on roadways or in highplaces.
On the other hand, however, simply automating thework will not lead to a radical solution from the viewpoint of efficiency. Achieving efficiency of maintenance and management cycles more quickly requires
inspection by using facility screening as well as
inspection technology that is suited to screening.
Rather than carrying out detailed inspections of thehuge number of facilities one by one, we can analyze
data collected from sensors installed in facilities andimage data from vehicle-mounted cameras in order to
identify facilities that should be thoroughly inspected.
Doing so can avoid risk and greatly reduce the number of inspections that take place. While moving forward with this R&D, we are also looking towards the
future challenge of realizing technology for ‘unconscious inspection’ by continuous monitoring, inwhich the facilities themselves transmit data [3].
2.3 E
 conomical repair and reinforcement technology for extending service life
NTT’s basic stance is to extend the service life ofaged telecommunication infrastructure facilities
without having to renovate them. To more economically perform the increasing amount of repair andreinforcement work, and to extend the service life offacilities, we are moving forward with R&D on technology that takes the special features of NTT facilities into consideration. Examples include technology
for repairing conduit with telecommunication cableVol. 12 No. 10 Oct. 2014

in place and without interrupting service, and methods for accurately determining age deterioration,
weak points susceptible to earthquake damage, andthe residual strength of each facility part by part sothat repairs can be completed with the minimum necessary local reinforcement. Another objective is toultimately break free from the maintenance and management cycle itself by taking measures to control
degradation when repair and reinforcement work isdone and achieve maintenance-free facilities thathave a perpetual service life.
Although there is currently very little constructionof new conduit and manholes, it is assumed that therelocation work will increase when age-deteriorated
roads and bridges attached to NTT conduit and manholes are repaired or renovated. To reduce the cost of
any new construction that is required, we are also
investigating facilities for which there is no concern
for age deterioration and which require no inspection,and simple, economical facilities that are limited to
optical cables, with a view to the future all-optical
network [4] [5].
3. Future development
Telecommunication infrastructure facility construction technology has developed around what is
known as civil engineering technology. However, themaintenance and management technology describedin this article essentially requires certain application
technologies from other fields as well as combined
use of various technologies. Those fields include
materials technology, device technology, image processing technology, and wireless and other telecommunication technology, as shown in Fig. 3. In that
respect, a major strength of the NTT laboratories isthe advanced research in diverse fields centeredaround telecommunications technology. The NTT
Access Network Service Systems Laboratories is
proceeding with R&D in cooperation with the NTT
Energy and Environment Systems Laboratories, NTT
Device Technology Laboratories, and NTT MediaIntelligence Laboratories. We will aim for innovativetechnology by further strengthening and expanding
this cooperation between laboratories and applying
the strengths of the NTT laboratories in our future
work. Beyond NTT R&D, we are also aiming fortechnology that can be applied to facilities around theworld and the development of new services and business opportunities that apply that technology. We will
work to achieve those goals by deepening cooperation with universities and other sources of expertiseFeature Articles

Repair &reinforcement

Facility management
Risk
Statistics
Reliability
engineeringengineering
Degradation

Long-term rust-proofing
Materials
technology

Civil engineering(Infrastructure
facilities fortelecommunications)

Earthquake
engineeringTime
Degradation prediction
Sensingtechnology

Telecommunications
Image technology
Deviceprocessing
technology
technology

Robottechnology
Reinforcement

Damage prediction

Inspection &diagnosis

Vehicle-mounted camera& image-based diagnosis

Continuous monitoring

Fig. 3. Maintenance and management technology R&D.

and exchanging ideas with other infrastructure enterprises that face the same problems, while making
continued efforts to extend our knowledge of industrial fields other than those related to infrastructure.
Currently, aging and the lack of resistance to earthquake damage are important problems for social
infrastructure facilities, including NTT facilities. The
NTT laboratories will address that problem head-on
and continue to conduct R&D that can contribute tosociety in general as well as meet the expectations ofNTT business companies and NTT Group companies.
References[1]

K. Kawabata, J. Mori, Y. Katsuki, and S. Ashikaga, “Facilities Management Technology for Optimizing Inspection and Repair Timing,”
NTT Technical Review, Vol. 12, No. 10, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
10fa2.html

[2]

[3]

[4]

[5]

K. Sakaki, K. Tanaka, M. Wakatake, and A. Ito, “Protecting Telecommunication Services from Earthquake Damage,” NTT Technical
Review, Vol. 12, No. 10, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
10fa3.html
K. Kawabata, M. Kikuchi, S. Mochizuki, R. Yamakado, H. Takahashi,
S. Kaneko, and D. Uchibori, “Technology for Highly Efficient andHigh Quality Diagnosis of Infrastructure Facilities,” NTT Technical
Review, Vol. 12, No. 10, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
10fa4.html
K. Kawabata, S. Sakai, T. Deguchi, T. Sudo, N. Hori, and T. Ishikawa,“Repair and Reinforcement Technology for Safe and Secure Concrete
Structures that Have a Long Service Life,” NTT Technical Review,Vol. 12, No. 10, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
10fa5.html
K. Sakaki, K. Takeshita, K. Tanaka, A. Koizumi, Y. Tashiro, R. Seta,
K. Tanabe, and D. Kobayashi, “Effective Repair and Reinforcement
Technology for Conduit Facilities,” NTT Technical Review, Vol. 12,
No. 10, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
10fa6.html

NTT Technical Review

Feature Articles

Fumihide Sugino

Executive Research Engineer, Civil Engineering Project, NTT Access Network Service Systems Laboratories.
He received the B.E. in civil engineering from
Hokkaido University in 1987 and joined NTT thesame year. He has studied ACEMOLE construction technology, which is a construction methodthat does not require road excavation. He has also
worked at NTT EAST. His main field of work
was telecommunication infrastructure such as
cable tunnels and underground pipeline systems.
He has been in his present position since 2012
and is currently studying NTT infrastructure.

Vol. 12 No. 10 Oct. 2014

Hiroshi Masakura

Senior Research Engineer, NTT InfraNet Corporation.
He received the B.E. in civil engineering from
Ehime University in 1989. He joined NTT in
1989. He is engaged in R&D of communications-infrastructure facilities. He was previouslywith NTT Access Network Service Systems
Laboratories. He took up his current position in
July 2014.

Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure

Facilities Management Technology
for Optimizing Inspection andRepair Timing
Kazuyoshi Kawabata, Jiro Mori, Yasuhiro Katsuki,
and Sho Ashikaga
Abstract

The huge number of telecommunication infrastructure facilities that support information technology
services continues to deteriorate from aging, and the number of technicians available to conduct maintenance is decreasing, so maintenance and management methods that are both practical and economical
are needed. To meet this need, we are carrying out research and development on facilities management
technology for setting inspection and repair criteria according to the state of each facility as determinedby degradation prediction. This article describes our work on facilities management technology and ourmaintenance and management methods for manhole inspection.
Keywords: infrastructure facilities, maintenance and management, degradation prediction

1. Facilities management technology
1.1 Background and problems
Facilities management technology provides maintenance and management criteria and methods for theefficient management of the Plan-Do-Check-Act(PDCA) cycle as a series of maintenance tasks that
includes facility inspection, diagnosis, repair andreinforcement, and maintenance planning (Fig. 1).
The ceiling collapse in the Sasago Tunnel in 2012heightened concerns about infrastructure safety
within Japan, and infrastructure maintenance andmanagement efforts have since increased further inimportance. However, various challenges arise interms of maintenance. The maintenance of telecommunication infrastructure facilities involves threeparticular problems:(1)	Facilities are aging, and the number of maintenance technicians is decreasing; consequently,
the efficiency of maintenance work must be
increased in order to cope with these issues.
(2)	The current uniform management criteria must
be revised, and a management method that candeal with individual cases of degradation thatarise according to installation conditions andother factors must be developed.
(3)	There is a need for cooperation with the managing authorities of the roads under which facilities are installed and with other companies that
install underground infrastructure elements.
We are working on a plan for maintenance andmanagement of telecommunication infrastructure
facilities based on preventive maintenance, in whichinspections are done and measures are taken before
problems occur. To avert the risk of facility failures,
preventive maintenance involves uniform, comprehensive, and periodic inspections of all facilities andthe implementation of repairs and renovation asneeded. However, the cost and labor required simply
to inspect the huge number of aging facilities alone isvery high. To deal with that problem, we are aiming
to optimize the timing of inspections and repairs
based on an evaluation of the state of individual
facilities and on predictions of their eventual degradation (Fig. 2) [1]. That requires technology forunderstanding the degradation mechanism and for
NTT Technical Review

Feature Articles

Maintenance PDCA

P

• Revision of inspection interval
according to degradation
prediction

Inspection &diagnosis• Close examination of inspection
items and process according toanalysis of degradation trend inorder to identify locations
susceptible to degradation• Prioritization of inspections andrepairs according to cost andrisk evaluations

D

C
Evaluation
A
Repair &reinforcement

Fig. 1. PDCA cycle of maintenance tasks.

Repair costs andrisk of facility failure
× Corrective
maintenanceFuture objectives

Present statePredictive maintenance• Individual evaluation• Prioritization

Preventive maintenanceDegradation • Comprehensive, uniform
prediction • Periodic

Quantity and costof inspections

Fig. 2. Target for future maintenance plan.

prediction of degradation, and technology for evaluating degradation and residual strength.
1.2 F eatures of telecommunication infrastructure
facilities
Manholes and tunnels are constructed of steel-reinforced concrete. Past research on the degradation
mechanism of concrete structures and research on
maintenance and management methods has mainly
focused on roads and railway structures, and muchknowledge has been obtained. Compared to roads
and railway structures, telecommunication infrastructure facilities are small, individual structures that
all have roughly the same specifications. Because thefacilities are buried underground, the environmental
conditions are more limited than those of outdoor
structures. Also, the number of facilities is huge. For
Vol. 12 No. 10 Oct. 2014

these reasons, it is important to identify methods thatare particularly suited to telecommunication facilities
as we review research on road and railway structures.
Manholes are currently the facilities that are mostnumerous and that require a substantial amount ofinspection work. We are working on a maintenanceand management method that takes the features ofmanholes into account.
1.3 C ooperation with other infrastructure enterprises
In addition to referring to past research on roads
and railway structures, our research and development(R&D) on maintenance and management methods
includes exchanging ideas on inspection work withother infrastructure management authorities andFeature Articles

Future inspection method

Areas

Prioritization

Inspection prioritization
Give inspection priority
to facilities that havehigh probability of
degradation.
Inspection interval: 10 years

Total numberof facilities:
680,000

Present inspection method

Inspection interval: 5 years

ManholesDegradation
prediction

Early discovery
of degradedfacilities

Revision of inspection
interval
Set inspection interval
according to predicted
progression of
degradation.
Fewer
inspections

DegradedHigh probabilityof degradation

Safer

Less
inspection
work

Sound

Fig. 3. Manhole maintenance process.

enterprises. As part of that, we are participating in the
Research Initiative for Advanced Infrastructure withICT (information and communication technology)
offered by the University of Tokyo Interfaculty Initiative in Information Studies [2]. In addition to conferring with infrastructure enterprises such as the East
Japan Railway Company, Tokyo Metro Co., Ltd., andthe Metropolitan Expressway Company Limited aswell as with university scholars, we are engaging in
discussions on the sharing and analysis of problems
related to infrastructure management and the proposal of improvement and operation methods. The
research initiative involves analyzing some of theinspection data obtained using the manhole inspection prioritization technology. Also, NEXCO East
Japan (East Nippon Expressway Company Limited)
and the Tokyo Electric Power Company, Incorporated(TEPCO) will join the initiative in 2014. TEPCO also
manages manholes and other facilities of the sametypes managed by NTT, so we expect even more
fruitful activities.
2. Manhole maintenance andmanagement methods
NTT has about 680,000 manholes throughout
Japan, and about 80% of them are at least 30 years
old. Some are beginning to show deterioration fromaging, which will continue in the future, so early dis

covery of degraded facilities and appropriate maintenance are required. Currently, manhole inspection isdone area by area at a uniform inspection interval for
all facilities. However, manhole degradation does notoccur consistently with the age of the facility, but varies with the installation environment and structure.
Our objective for the future is to apply practicalinspection timing in which the progression of degradation is predicted for each manhole and inspections
are performed with priority given to facilities thathave a high probability of degradation, while theinspection interval is extended for other facilities(Fig. 3).
2.1 Manhole inspection prioritization technology
We used FEM (finite element method) analysis* toclarify the relation between outside forces that act on
the facilities and the installation environment, andcracking that occurs inside manholes. We used theresults to analyze existing inspection data in order to
identify the inspection items and installation conditions on which an inspection judgment of degraded isbased. The result is that we were able to determine
which facilities have a high degradation probability[3].
*

FEM analysis: The method of analysis in which a continuum that
has infinite degrees of freedom is approximated by using a region
that contains some specified finite number of unknown quantities
or a finite set of elements to solve an engineering problem.

NTT Technical Review

Feature Articles

FEM analysis

Data mining…65.2%

Others…42.7%…25.4%…23.9%
Degradation rate

(Priority)

Rank in order of degradation rate

…21.8%…19.8%…16.8%…11.4%…9.8%

High probability of degradation

Low

Facilities for inspection

Divided according to effects of external forces…70.2%

High

Degradation rate

Large effect of external forces

Low probability of degradation

Fig. 4. Assignment of priority.

First, facilities are sorted according to whether or
not they are in installation environments where theeffect of external forces may cause cracking. The data
are then analyzed in order to classify the facilities
according to the probability of degradation. Manholes that are subjected to large external forces andhave a high probability of degradation can then be
given priority in inspection (Fig. 4).
We analyzed about 20,000 inspection data values
and assigned priorities for the 7600 manholes to beinspected in the future. In 2013, about 2700 inspections were done, largely in order of priority. The
degraded facility discovery rates (number degraded/
number inspected) were 9.5% for all of the inspection
data collected so far, 14.2% for the prioritized facilities, and 13.3% for the actual inspection results. In
the actual inspections, too, the discovery rate washigher than previously obtained by a factor of from
1.4 to 1.5, close to what was expected.
The former area-based inspection scheme allowed
efficient setting of inspection routes. Inspection sites
selected according to priority, however, might bescattered over a wide area, making inspection work
Vol. 12 No. 10 Oct. 2014

inefficient. In practice, however, manholes that haverelatively high repair priorities tend to be clustered
together, so there was no actual decrease in efficiency
due to inspection routing.
The results described above confirm both the practicality of this method for actual inspection work andthe effectiveness of early discovery of degradedfacilities.
2.2 Revision of manhole inspection interval
Currently, the manhole inspection interval is about
five years, but it is desirable to set the interval so thatit matches the progression of manhole degradation.
We therefore proposed a method of setting the manhole inspection interval based on the level of rebar
corrosion risk determined according to an understanding of the manhole degradation process obtainedby observing the progression of rebar corrosion
within the concrete.
The process of degradation by rebar corrosion in
ordinary steel-reinforced concrete structures is illustrated in Fig. 5. There are four levels of risk: latent,
which is prior to the beginning of rebar corrosion;Feature Articles

LatentProgressing

Accelerating

Concrete degradation
Rebar

Degradation(Rebarcorrosion)

Neutralization

Put in service

Degradation

Rebar corrosion
Rust

Corrosion (rust)Corrosion starts

Cracking

Cracking
occursExposure
Degradation
event (point A)
Transition time (T years)

Riskmanagementlevel (point B)
Time

Fig. 5. Process of degradation in reinforced concrete.

progressing, in which rebar corrosion has begun but
no degradation is apparent on the surface of the concrete; accelerating, after cracking has appeared; anddegradation, where concrete has actually separated
or fallen off, and protection of the rebar is compromised. Point A is where degradation can be confirmed
visually, point B is the rebar corrosion state that
determines the risk level, and T (years) is the time forthe transition of rebar corrosion from point A to point
B. To detect point A by inspection before point B isreached, the inspection interval must be set to T years
or less. That is to say, if the state at the time of theinspection is before point A, point B will not bereached after T years with no measures taken at thetime of the next inspection. If degradation of point A
or later is confirmed at the time of the periodic
inspection, the arrival at point B at the time of thenext inspection T years later can be prevented byundertaking some repairs or other measures.
Data from past studies and the results of further onsite investigations show that if point A is taken as thepoint of rebar exposure and point B as the criteria forrequired repair of cut-and-cover tunnels, the transition time from point A to point B (T) with a rebar
corrosion rate of 15% is about 10 years. Because‘exposed rebar’ is a phenomenon that can be confirmed visually, the inspection can be done without agreat change in the conventional inspection work
flow. These results suggest that the current inspection
interval of five years can be extended in order toincrease the economy of inspections. (The results for

this finding were obtained in June 2014.)
3. Future development
Our future work on maintenance and management
methods for manholes will aim to improve the accuracy of predicting the degradation progression thattakes into account the environmental conditions ofindividual manholes. We also plan to investigate theextension of these methods to tunnels and otherfacilities. Although the studies of maintenance andmanagement methods have assumed periodic visualinspections as currently done, future R&D on facilities management technology will build on trends in
inspection technology in which other techniques areapplied.
References
[1]

[2]
[3]

F. Sugino, “R&D Trends in Communications Infrastructure to
Achieve Safe and Secure Access Networks,” NTT Technical Review,Vol. 11, No. 6, 2013.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2013
06fa2.html
Website of the Research Initiative for Advanced Infrastructure with
ICT,
http://advanced-infra.org/english.html
K. Kawabata, J. Mori, H. Masakura, R. Yamakado, S. Ashikaga, and
Y. Katsuki, “Inspection Prioritizing Technique for Early Discovery of
Defective Facilities–Manhole Facility Inspection Prioritization,” NTT
Technical Review, Vol. 12, No. 6, 2014.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2014
06ra1.html

NTT Technical Review

Feature Articles

Kazuyoshi Kawabata

Yasuhiro Katsuki

Jiro Mori

Sho Ashikaga

Group Leader, Concrete Structure Group, Civil
Engineering Project, Access Network Service
Systems Laboratories.
He received the B.E. and M.E. in civil engineering from Tokyo Institute of Technology in1988 and 1990, respectively. He joined NTT in
1990. He is engaged in R&D of communications-infrastructure facilities.

Senior Research Engineer, Concrete StructureGroup, Civil Engineering Project, Access Network Service Systems Laboratories.
He received the B.E. in civil engineering from
Osaka City University in 1990 and joined NTT
the same year. He is engaged in R&D of communications-infrastructure facilities.

Vol. 12 No. 10 Oct. 2014

Engineer, Concrete Structure Group, Civil
Engineering Project, Access Network Service
Systems Laboratories.
He received the B.E. in electronics from
Doshisha University, Kyoto, in 2007. He joined
NTT in 2007. He is engaged in R&D of communications-infrastructure facilities.

Engineer, Concrete Structure Group, Civil
Engineering Project, Access Network Service
Systems Laboratories.
He received the B.E. and M.E. in civil engineering from Hokkaido University in 2009 and2011, respectively. He joined NTT in 2011. He is
engaged in R&D of communications-infrastructure facilities.

Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure

Protecting Telecommunication
Services from Earthquake Damage
Katsumi Sakaki, Koji Tanaka, Masato Wakatake,and Akira Ito
Abstract

To protect telecommunication network facilities from damage caused by major earthquakes, NTT
Access Network Service Systems Laboratories has been continuously conducting research and development on technology to make the telecommunication infrastructure resistant to earthquakes and to
improve the accuracy of evaluating earthquake resistance. This article describes our work to improve thetechnology for evaluating non-standard private bridges that was introduced in 2013 as a measure to
improve the earthquake resistance of important facilities. It also describes the technology currently underdevelopment for evaluating the earthquake resistance of conduit.
Keywords: earthquake resistance technology, private bridge, damage estimation technology

1. Introduction
The 2011 Great East Japan Earthquake and Tsunami caused enormous damage to the telecommunication infrastructure. The government warns that wewill remain susceptible to large-scale damage fromearthquakes that originate in the Nankai Trough ordirectly beneath the Tokyo area well into the future.
Therefore, the need to strengthen facilities to makethem safer and more resistant to earthquakes is higher
than ever.
NTT Access Network Service Systems Laboratories is working to improve the reliability of telecommunication infrastructure facilities based on an analysis of damage to facilities caused by major earthquakes that occurred in the past. In particular, since
the Great Hanshin Earthquake in 1995, the earthquake resistance of cable tunnels and standard private
bridges, which are important infrastructure facilities,
has been evaluated according to new criteria based on
the definition of a Level 2 Earthquake by the Japan
Society of Civil Engineers. In addition, measures toprotect structures in the event of large-scale earthquakes have been applied. This article describes theevaluation technology introduced in 2013 for improving the reliability of earthquake resistance of nonstandard private bridges (defined in section 2).
Much importance has been placed on strengthening
underground pipeline systems located in areas likely
to experience ground liquefaction during earthquakes.
Improvements such as making conduit joints flexible
have been made, and the effectiveness of these measures was evident after the Great East Japan Earthquake in 2011 and other major earthquakes. However,these earthquake-resistant joints are applicable only
for newly constructed facilities; they are not currently
used to update conduit that was constructed andinstalled before the improvements were introduced.
Therefore, technology has been developed for
improving the earthquake resistance of old, standard
conduit that is already installed without having to
excavate it. The result of this development is the pipe
insertion type (PIT) new conduit method, which has
been confirmed to reduce damage from earthquake
motion and ground deformation through the use of afree-standing lining [1].
Currently, technology for evaluating earthquake
resistance is being studied in order to effectively
apply renovation technology such as the PIT method
to the huge quantity of existing standard conduit. We
have adopted a macro-evaluation method (Fig. 1) todetermine the degree of damage and the number of
NTT Technical Review

Feature Articles

Ranking by need for
improvement
A: Urgent
B: Planned
C: Requires attention
D: Improvement notneededFig. 1. Current earthquake-resistance evaluation technology.

Problem• Individual damage not known• Limited database• Output is damage rate based on past incidents

Liquefaction
Intensity: upper-6

EffectNo liquefaction
Intensity: upper-6• Can identify facilities that need immediate measures• Can manage facilities economically• Can diagnose degraded facilities in weak earthquake
regions (previously not evaluated)

A: Curving pipe
B: Deterioration

Same earthquake
magnitude …

D: Nearby structure
Liquefaction
Intensity: No liquefaction
lower-6
Intensity: lower-6
Damage rate =Number damaged
Total number examined

E: Discontinuous groundcharacteristics

C: Discontinuity (pipewith protective concrete)
A + B + C + D + E Effect rate 50%
A+D+E
Effect rate 30%
B
Effect rate 10% (dependent on degree of degradation)
Toward prioritization and individual evaluation
based on unified damage estimation

Fig. 2. Highly precise damage estimation technology (concept).

damage incidents that may occur in a wide area in theevent of an earthquake. This method uses a statisticalanalysis of damage from past earthquakes based on
the relationship of the earthquake magnitude, whetherliquefaction occurred, the type of conduit pipe, andthe age of the structure. For example, the damage rate
is A% for a steel pipe constructed before 1985 that is
exposed to an earthquake measured at upper 6 on theJapan Meteorological Agency seismic intensity scalewith liquefaction. That method has been used to predict damage from a major earthquake that is expected
Vol. 12 No. 10 Oct. 2014

to occur in the near future [2].
A problem with this method, however, is the difficulty in evaluating with precision individual sectionsof conduit in order to decide where to begin implementing measures to strengthen the huge number ofold conduit pipes against large-scale earthquakes.
Currently, we are aiming at developing technology
for identifying the specific weak points of individual
pieces of conduit (Fig. 2). Our specific objective is toachieve technology that will enable highly accurate
damage prediction through quantitative evaluation ofFeature Articles

Bridge with jointed steel pipes: Conduit pipes are welded together with steel straps.

Bridge without beams: Conduit pipes are supported by separated girders.

Fig. 3. Images of non-standard private bridges.

various factors that affect the underground environment, for example, loss of strength due to the deterioration of steel pipe, the line type, which refers to thecharacteristics of conduit such as whether it is horizontal curving or longitudinal sloping, or whether
protective concrete is used, and the ground conditions
where the conduit is located.
2. Earthquake resistance evaluation technology
for non-standard private bridges
NTT has constructed and owns two types of private
bridges that support telecommunication cables (telecommunication bridges): standard and non-standard.
The standard bridges conform to current NTT standards. In contrast, the non-standard bridges arebridges that conform to old standards or that weredevised and constructed individually according to onsite conditions. There are two broad types of nonstandard private bridges (Fig. 3).
Standard private bridges have been evaluated forearthquake resistance; however, the structure of nonstandard private bridges differs greatly from ordinary
bridges, and hence, their behavior during an earthquake is not clear. Private bridges are laid across rivers and carry assorted cables used to provide telecommunication services. A failure in one of these bridges
would affect third parties such as pedestrians, cars, orvessels traveling on or under the bridge. Although
there have been no incidents of bridge failures in pastearthquakes, adequate construction and maintenancetechniques are necessary because these bridges areimportant facilities for ensuring network reliability
and safety. For this reason, we have been investigating the conditions under which damage occurs andclarifying the damage mechanism during earthquakes
by investigating the vibration characteristics andstructural analyses of existing facilities [3].
The factors relevant to earthquake damage that may
affect bridges fall into two broad types: (i) the inertial
force from vibration caused by the earthquake and (ii)collapse of the bridge abutments or the main bridge
structure due to liquefaction of the ground that supports the bridge. We have developed technology forunderstanding the effects of these factors using easily
obtained data. The process used to evaluate earthquake resistance is illustrated in Fig. 4.
2.1 Evaluation of earthquake vibration
We have clarified the vibration movement of nonstandard private bridges by investigating actual nonstandard bridges and analyzing the results. We thenused the results to create a chart for comparing theinertial forces generated by earthquake motion to theresistance of the steel materials used in the bridges
based on simple data such as the length of the bridge
NTT Technical Review

Feature Articles

1) Evaluation of shaking
during earthquake

ke

Need for measures determined from lengthof bridge, number of conduit pipes, etc.
Generated
force

START

a
qu
rth
Ea tionmo2) Evaluation of liquefaction

e

ak
qu
rth n
a
E tio
mo

OK

Publishedmaterials

Probability ofliquefaction: high• Liquefaction history
diagram• Liquefaction map• Micro-geomorphologicalmap

Measures required

Length of bridgeNG

MeasuresrequiredOK

Earthquake
resistant

Probability ofliquefaction: low
BridgeNG

NG: no goodFig. 4. Process to evaluate earthquake resistance.

and the number of conduit pipes. For bridges without
beams, which are one type of non-standard private
bridge, we found that the possibility of damage canbe determined from the length alone.
2.2 Evaluation of liquefaction
Non-standard private bridges that do not havestrong abutments are susceptible to collapse due toliquefaction of the surrounding ground. Therefore,such bridges that are located in areas where the riskof liquefaction is high are classified as requiring
improvements. We also created a procedure for determining liquefaction areas using data published by
local governments or research organizations. Previously, the determination of liquefaction was based ontime-consuming studies that required the collectionof geotechnical boring data in the vicinity of the facility. However, liquefaction can be determined by aprocedure that effectively uses liquefaction history
diagrams, liquefaction maps that record the value ofthe potential of liquefaction, micro-geomorphological maps, and other published data, thus making it
possible to determine the risk of liquefaction for aparticular area.
These two evaluation processes enabled us to identify non-standard private bridges that are at high riskof damage and that consequently need immediate
countermeasures.

Vol. 12 No. 10 Oct. 2014

3. Improving earthquake resistanceevaluation technology
3.1 F actoring in deterioration of underground
conduitEstimating the damage to underground conduit during an earthquake was previously done assuming thatthe conduit was sound before the earthquake. Actually, however, a lot of conduit has been in place forover 30 years and may therefore be partially corrodedin some areas, and corroded steel conduit is more
likely to be weaker than sound conduit. To moreaccurately determine the location where damage may
potentially occur, it is necessary to know the locationof weakened conduit and also to what extent the performance of such conduit has decreased. For that
purpose, we conducted performance tests on collected conduit pipes that were removed in construction
work throughout the country (Fig. 5) to determine thedegree of deterioration.
The results of the performance testing showed that,on average, the formerly buried conduit performed atroughly 90% of the level of sound conduit, which is
to say that the average loss of strength was 10%.
However, there was a large dispersion in the values
for individual samples, and many samples performed
as well as sound pipes. More detailed observations
revealed that although there were some exceptions,the performance tended to decrease when there wassevere corrosion on the inner surface (Fig. 6). We are
currently at the stage of confirming the results qualitatively, but in the future, we plan to develop technologyFeature Articles

Pipe

Steel bar

Joint

Jig

Attached to the floor

Fig. 5. Performance test (tension test) of conduit pipe.

Inner corrosion: slight

Performance (%)

100
Inner corrosion: severe
90

80

70

No corrosion

Sample 1

Sample 2

Sample 3

Sample 4

Fig. 6. Examples of inner corrosion and loss of strength.

for predicting the decrease in performance of individual conduits by conducting more basic tests andon-site investigations to reveal the relation of loss ofstrength to the length of time the conduit has been
underground and the ground environment of the conduit.
3.2 F actoring in the line type of underground
conduitNTT underground conduit pipes follow the paths ofroads and may deviate from a straight line verticallyor horizontally to avoid other buried objects. Externalforces due to earthquakes may be concentrated atsuch deviations, making those locations weak points.
Some conduit is buried at shallow depths, and theinner cable is protected from construction such as
road excavation by concrete that is poured around the
conduit. (Since 2003, a protective cover made fromrecycled optical fiber has been used instead of concrete.) In such locations, the conduit characteristics
are discontinuous because the conduit is partiallycontained within protective concrete, and earthquake
forces may be concentrated in those places, creating
weak points.
NTT Technical Review

Feature Articles

Table 1. Results of damage rate analysis by type of installation.
Inspected spans

Damaged spans

Damage rate

Total

1064

82

7.7%

Curved61 (estimated)

6

9.8%

Sloping

Unknown

56

Unknown

With protective concrete

100 (estimated)

22

22%

Horizontal curve

Discontinuity(Assuming that conduit is contained
within protective concrete)

Slope
θ
R

θ

Horizontal curve and slope results (relative to straight pipe)

5Radius of curvature 1 m

4.5

Sloping pipe

4

Radius of curvature 2.5 m

3.5Radius of curvature 10 m

Axial force generated (kN)

ResponsivenessDiscontinuity results (compared to straight pipe)
150

3
2.5
2
1.5
1
0.5
0

sinθ
0

0.2

0.4

0.6

0.8

The vertical axis indicates the magnitude of the external
force acting on the pipe relative to a straight pipe.

1

120
90
60
30
0

With protective concrete Without protective concrete

It is known that the axial force (stress) is higher by afactor of 1.1 for when there is a discontinuity than when
there is no discontinuity.

Fig. 7. Analysis models and results.

Past studies of earthquake resistance conducted by
NTT did not consider such changes in linearity; thus,
the NTT Access Network Service Systems Laboratories is now investigating the susceptibility of suchsites to earthquake damage.
An investigation of damaged conduit was conducted after the Great East Japan Earthquake in 2011. The
investigation was limited to underground steel pipe
sections, so conduit that was located above ground,such as conduit attached to bridges, was excluded.
The results are listed in Table 1.
The investigation revealed relatively high damage
rates for facilities that had protective concrete within
the span (higher than the overall rate by a factor of
2.8) and for curved facilities with a radius of curvaVol. 12 No. 10 Oct. 2014

ture of 100 m or less (higher by a factor of 1.3). To
quantify the susceptibility to damage, three types ofconduit lines—curved conduit, conduit laid on aslope or gradient, and conduit enclosed in protective
concrete (referred to as a discontinuity)—were modeled, and a numerical analysis was executed. By
comparing the results with the analysis results forstraight conduit with no linear deviations, we wereable to evaluate the effects of the line type of conduit
during a large-scale earthquake. The results areshown in Fig. 7. Compared to the external force
applied on straight conduit, the force is up to 3.5
times higher for curved installations and up to 4 times
higher for sloping conduit. With protective concrete,
the force is about 1.1 times that of conduit withoutGroup with highdamage rate in strong
earthquake region

PGV (cm/s)

3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0

Group with low
damage rate in strong
earthquake region((100,100](200,200](300,300](400,400](500,500](600,600](700,700](800,800](9 0,90(1000,1000](1100,1100](1200,1200](1300,1300](1400,1400](1500,1500](1600,1600](1700,1700](1800,1800](1900,1900](2000,2000](2100,2100](2200,2200](2300,2300](2400,2400]
00,
2500]
0]

Group with highdamage rate in weak
earthquake region

Damage rate R (10−2)

3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0

(0,1
0]
(10
,20
(20 ]
,30
(30 ]
,40
(40 ]
,50
(50 ]
,60
(60 ]
,70
(70 ]
,80
(80 ]
,90
]
(90
,10
0
]
(10
0,1
(11 10]0,1(12 20]0,1(13 30]0,1(14 40]0,1(15 50]0,1(16 60]0,170]

Damage rate R (10−2)

Feature Articles

PGA (cm/s2)*Open diamonds indicate there is insufficient data (parameter is less than 0.5% of the total).

Fig. 8. Results of analyzing underground conduit damage.

protective concrete. Although the analysis is very simple, and more detailed model settings and numericalanalyses are required, we can nevertheless identify
which types of conduit may have weak points during
a large-scale earthquake. In the future, we will conduct a numerical analysis using more detailed conduit
models.
3.3 F
 actoring in the ground environment ofunderground conduit
In this section, we describe how the ground conditions affect the estimation of damage to conduit during an earthquake. For example, the liquefaction
phenomenon was responsible for many incidents ofdamage that occurred to NTT conduit during theGreat East Japan Earthquake in 2011. To quantify theeffects of the ground environment on damage, NTT
Access Network Service Systems Laboratories performed analyses using ground data and facilities
data.
The ground data used in the analysis were earthquake magnitude, peak ground velocity (PGV), andgeomorphological classification (e.g., whether it wasreclaimed land).
The facilities data used for the analysis included
data on a few hundred spans for which damage wasconfirmed and approximately 20,000 spans for which
there was no damage.
A geographic information system (GIS) was usedin the analysis to investigate the correlation between
the ground conditions and damage. The damage ratio
was calculated by focusing on the facility attributes
such as the age or type of pipe, the magnitude of theearthquake, and the ground conditions. The results
are shown in Fig. 8.
The group of conduit pipes in regions where strong
earthquakes occurred had a high damage rate, and thegroup subjected to earthquake motion with a PGV of
90 cm/s or more in particular had a damage rate ofabout 3%, which is high compared to the othergroups. Closer examination of this group revealed
that a lot of the damaged conduit in the group wasburied in ground whose micro-geomorphologicalclass is backswamp, which is generally weak ground,and a lot of the damaged conduit was a type that was
introduced prior to the current standards. In otherwords, the analysis revealed that old standard conduit
in weak ground has a high damage rate.
A group with a low damage rate was also confirmed, even though the samples in this group werelocated in regions where strong earthquakes had
occurred. The PGA (peak ground acceleration) was
about 1400 cm/s2, and the damage rate in that group
was 0.5%, which is lower than in other groups. Mostof the conduit in that group was constructed based on
current standards. These results indicate that the current standards for earthquake resistance are superior
to the former standards.
In contrast, a group of conduit that exhibited a damage rate of 1% in weak earthquake regions where the
PGV was around 30 cm/s was also confirmed. Thisvalue is about the same as the damage rates of othergroups subjected to strong earthquake motion. An
examination of the feature attributes of that grouprevealed that in many cases, the conduit conformed tothe old standards and was buried in reclaimed land. In
other words, the damage rate was high for old standard conduit buried in areas where liquefaction
NTT Technical Review

Feature Articles

occurred.
The three tendencies concerning ground environment
described here are the same as previous qualitative
conditions under which conduit was found to be susceptible to damage during earthquakes in previous
qualitative studies. Nevertheless, these results can beconsidered important for improving the prediction ofearthquake damage on the basis of data on underground facilities and the ground environment.

is necessary to implement measures that combine
these factors. The technology reported here has contributed to the improved reliability of important telecommunication routes by identifying the weak points
that are most likely to be damaged in earthquakes.
References[1]

4. Future development[2]

Various factors other than the need to implement
earthquake resistance measures may lead to updatingof the telecommunication infrastructure. These
include aging of facilities, insufficient capacity offacilities, eliminating redundancy in relay cableroutes, economizing construction work done by othercompanies or done collaboratively, and rerouting. It

Katsumi Sakaki[3]

Y. Yamazaki, N. Segawa, M. Okutsu, N. Ishida, T. Inamura, and K.
Tanaka: “Improved Earthquake Resistance for Existing Facilities byReinforcement of Occupied Cable Conduit (3000 core),” NTT Technical Journal, Vol. 23. No. 11, pp. 42–46, 2011 (in Japanese).
Y. Yamazaki, N. Segawa, K. Tanaka, T. Okazawa, N. Ishida, and T.
Kishimoto, “Evaluation of Telecommunication Facility Performance
during an Earthquake,” NTT Technical Journal, Vol. 21. No. 8, pp.
75–78, 2009 (in Japanese).
A. Ito, N. Ishida, N. Segawa, K. Kuribayashi, and T. Suzuki,“Research on Earthquake-proof Evaluation of the Bridge for Communication which Has Special Structure,” Journal of Japan Society of
Civil Engineers, Ser. A1 (Structural and Earthquake Engineering),
Vol. 70, No. 4, pp. 701–709, 2014 (in Japanese).

Masato Wakatake

Branch Manager, NTT InfraNet Hokuriku
Branch Group Leader, Pipeline System Technology Group, Civil Engineering Project, AccessNetwork Service Systems Laboratories.
He received the B.E. in civil engineering fromMusashi Institute of Technology (now Tokyo
City University), in 1988. He joined NTT in 1988
and is engaged in R&D of communicationsinfrastructure facilities.

Engineer, Pipeline System Technology Group,
Civil Engineering Project, NTT Access Network
Service Systems Laboratories.
He received the B.E. and M.E. in engineeringfrom Osaka University in 2008 and 2010. After
joining NTT WEST in 2010, he was involved indesigning an optical cable route. In 2012, hemoved to NTT Access Network Service Systems
Laboratories. He is now studying earthquake
resistance technology for underground pipeline
systems. He is a member of JSCE.

Koji Tanaka

Akira Ito

Senior Research Engineer, Pipeline System
Technology Group, Civil Engineering Project,
NTT Access Network Service Systems Laboratories.
He received the B.E. and Ph.D. in civil andenvironmental engineering from University of
Yamanashi, in 1990 and 2013. He joined NTT in
1990 and developed trenchless repair technologies for underground pipeline systems. He
moved to NTT Access Network Service Systems
Laboratories in 2012. He is currently researching
earthquake proofing technology for underground
pipeline systems. He is a member of the Japan
Society of Civil Engineers (JSCE).

Vol. 12 No. 10 Oct. 2014

Engineer, Pipeline System Technology Group,
Civil Engineering Project, NTT Access Network
Service Systems Laboratories.
He received the B.E. and M.E. in agriculture
from Kyoto University in 2010 and 2012. He
joined NTT Access Network Service Systems
Laboratories in 2012. He is studying earthquake
resistance technology for underground pipeline
systems. He is a member of JSCE.

Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure

Technology for Highly Efficient andHigh Quality Diagnosis ofInfrastructure Facilities
Kazuyoshi Kawabata, Masato Kikuchi, Shoji Mochizuki,
Ryo Yamakado, Hiroyuki Takahashi, Suguru Kaneko,
and Daisuke Uchibori
Abstract

The large number of infrastructure facilities throughout the country must be regularly inspected anddiagnosed for possible problems. The NTT Access Network Service Systems Laboratories is working
toward a transition from the current methods involving inspection and diagnosis by humans to automatic methods, which will be essential for carrying out such work efficiently over a wide area. This work
involves advancing the existing image processing technology through a fusion of various technologies
that include sensor networks, mechatronics, and remote sensing systems that have been developed inother laboratories. This article describes the inspection technology for concrete utility poles and manhole
covers as representative of the direction of our most recent research and development.
Keywords: infrastructure facilities, non-destructive inspection technology, automatic diagnosis

1. Introduction
NTT performs systematic inspections of all facilities, and most of these inspections are done visually.
The inspectors observe the infrastructure facilities(for example, concrete utility poles and manholes)that support telecommunications services to see
whether any deterioration (such as degradation of
performance over time due to corrosion of steel andneutralization of concrete) or deformation (cracking,warping, distortion, peeling, rust run-off, and otherabnormalities that can be seen on the surface) has
occurred and to determine the degree and scale of thedeterioration. The necessary repair, reinforcement, or
renovation is then performed. Also, the large amountof data obtained in the inspections is stored in a database and used as evaluation criteria and as a basis for
optimizing and adjusting evaluation methods andoperations in the maintenance and management of
infrastructure facilities. Through such efforts, we

ensure the safety and reliability of the many NTT
facilities throughout the country and support stableprovision of telecommunication services.
Nevertheless, there are problems that must be overcome by introducing new technology for the inspection and diagnosis of infrastructure facilities. These
problems include the following:•	The aging of NTT infrastructure facilities resultsin the need for more frequent inspections andinspection of more items, which increases
inspection costs.
•	As the baby boom generation retires, the numberof proficient technicians with experience andexpertise in conducting inspections is declining,
so the quality of inspection work done by successor technicians must be maintained andimproved.
•	The state of degradation must be determined inorder to facilitate renovation and extension ofservice life of the underground tunnels thatNTT Technical Review

Feature Articles

house a large quantity of telecommunication
cables and extend for several dozen kilometers,
and the manholes for accessing facilities buried
beneath roads.
•	There is a strong social need to preserve thesafety of the aging social infrastructure, as wellas the structures managed by local and national
governments (bridges, tunnels, roads, manholes,
and other ancillary road structures) and thefacilities that depend on them (such as the conduits supported by bridges). The consequent
trend toward obligatory periodic inspections
results in a significant amount of inspection
work and a high inspection cost.
The NTT Access Network Service Systems Laboratories took these problems into account and focusedon the three aspects of cost, quality, and added value
in creating new inspection technology. For cost, wetargeted inspection methods that involve less work,
fewer procedures, and fewer people. For quality, we
aimed to develop inspection methods that could bedone accurately and uniformly by anyone, anywhere,
and at any time, without requiring the skill level of anexperienced technician. For added value, our objectives were ease of handling, higher work safety, andvisualization techniques for locations where nakedeye inspections are difficult.
The research being done at the NTT Access Network Service Systems Laboratories on infrastructure
facilities inspection and diagnosis technology is moving forward, with short-to-mid-term work and longterm work being done in parallel.
Our short-term to mid-term work puts priority on
maintaining safety with respect to inspection of infrastructure facilities (concrete poles, manhole covers,
and facilities attached to bridges) in which there ispotential for damage or harm to third parties. Specifically, we aim to develop inspection and diagnosis
technology that eliminates sites where inspection isdifficult or impossible and that reduces the number ofsites where high levels of labor, cost, and technicalskills are required. Our mid-term to long-term workis aimed at developing innovative inspection anddiagnosis technology that achieves a radical change
in the maintenance and management of infrastructure
facilities through collaboration with other NTT laboratories developing image processing technology andsensor technology to enable screening inspection andcontinuous monitoring using still and moving images.
This article describes the direction of the mostrecent research on infrastructure facility inspection
and diagnosis for concrete poles and manhole covers
Vol. 12 No. 10 Oct. 2014

underway at the NTT Access Network Service Systems Laboratories.
2. Concrete pole inspection anddiagnosis technology
NTT EAST and NTT WEST together have about
eight million concrete poles throughout Japan, which
are inspected periodically to maintain them in a safe
condition. In the inspections, the surface is examinedfor cracks by eyesight or with a binocular microscope. Ultrasound sensors are used for non-destructive inspection of parts that are underground or thatare hidden by sheets attached to the poles to preventthe posting of advertisements, and magnetic sensors
are used to check the utility pole for internal degradation. An accurate understanding of cracking or internal degradation, however, requires inspectors thathave expert knowledge, skill, and proficiency.
Recently, the number of proficient technicians available for inspecting concrete poles that are in service
has been decreasing, making it difficult to maintainboth the quantity and quality of inspections. To
address this problem, the NTT Access Network Service Systems Laboratories has been researching threeinspection and diagnosis technologies for utility
poles. These technologies enable inspections that areeven more accurate and efficient than current inspections regardless of the skill and proficiency of theinspector.
2.1 C rack inspection technology based on image
analysis
This technology can automatically detect the cracks
that arise on the surface of concrete poles from photographic images obtained with commercially available digital cameras (Fig. 1). However, remotely
acquired photographs of concrete poles often include
cables, foot pegs, and other objects attached to thepoles, as well as the area in the background, so theoutline edges of those objects may be mistakenly
detected as cracks in the image processing. Humans
use information such as hue and the feel of a material
to recognize cracks on the surface of a concrete pole,so we have implemented a function for automaticallyremoving attached objects and the background fromthe image by implementing this discrimination taskusing image processing technology. By doing so, wewere able to reduce errors in detection and to accurately detect cracks. This technology can be used to
conduct accurate inspections, regardless of worker
skill and experience, and it makes it easy to check forFeature Articles

Image
acquisition
Analysis on
personal computer

ObjectCrack

Image transfer

Crack

ObjectDigital camera

Fig. 1. Detection of cracks by image analysis.

Scanning sensor over sheet
Observation throughthe sheet
Crack
Millimeter-wave
sensorPosting prevention
sheet

Fig. 2. Detection of cracks beneath protective sheet by millimeter-wave see-through imaging.

the presence of cracks and their location, including
on the upper parts of concrete poles, which previously required extensive labor for visual inspection.
There is also a function for automatically organizing
and managing the large number of acquired images
for each utility pole, which greatly reduces theamount of paperwork.
2.2 T echnology for detecting cracks beneath protective sheets
Currently, the detection of cracks hidden behindposting prevention sheets and other obstacles is donewith detection equipment that uses ultrasound. However, some expertise is required to read the propagated waveforms with this technique, so the inspectors must have the appropriate skills. To solve thisproblem, we developed the world’s first equipment
for conducting inspections for cracks beneath posting

prevention sheets with imaging technology that uses
millimeter waves* in the 76.5-GHz band, at which the
sheeting is transparent (Fig. 2).
In this technique, the surface of a utility pole isilluminated with millimeter waves. Places on the surface where there are no cracks reflect the waves backwith a certain strength, but places where there arecracks disperse the reflected waves in all directions,so the strength of the waves reflected back toward thesource (backscattering) is detected as a small signal.
Because the posting prevention sheets are transparent
to millimeter waves, and the waves are reflected by
the concrete surface, we are able to implement thesee-through imaging of cracks. The crack inspection*

Millimeter wave: An electromagnetic frequency band extending
from 30 GHz to 300 GHz. The short wavelengths make this bandintermediate between light and radio waves.

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Feature Articles

The need for renovation is displayed
as High, Medium, or Low.

TappingDiagnosis

Acceleration
sensorDiagnostic equipment

Fig. 3. Diagnosis of soundness by vibration analysis.

system we constructed creates a see-through image
from the signals detected from the concrete surface,and software included in the system automatically
identifies cracks from the image. It is thus possible tocheck for cracks visually without relying on inspector
skill or proficiency.
2.3 Soundness diagnosis technology
Currently, when cracks are discovered in a concretepole, magnetic sensors are used to perform a detailed
examination to determine the condition of the rebar
inside the pole. That method, however, requires a
special work vehicle to access the upper part of thepole so that the pole can be scanned, and the measurement requires time and labor. We therefore developed
a soundness diagnosis technique that enables aninspector on the ground to diagnose soundness by
simply striking the side of the utility pole with a hammer (Fig. 3). The inspector taps the utility polearound the circumference with the hammer, and theresulting vibrations are measured. If the utility pole issound, the measurements will be uniform around thecircumference. If there is a defect or other problem,
the rigidity will not be uniform, and the frequenciesof vibrations measured from striking the pole at certain places around the pole will vary. The soundnessof a pole can therefore be determined by variations in
the natural frequency in response to tapping aroundthe pole circumference.
The three technologies described above are alreadybeing used for some of the concrete poles managed
by NTT, and we plan to proceed with their commercial introduction in order to maintain and manage
facility safety.
Vol. 12 No. 10 Oct. 2014

3. Technology for measuring level differences inmanhole covers
NTT maintains about 680,000 manholes throughout Japan, and the manhole covers are inspectedperiodically to see if there is a difference in level
between the manhole cover and the seat it fits into. If
there is an excess level difference between the manhole cover and the frame, it could result in an uncomfortable and noisy ride for vehicles driving over the
manhole cover. The current method of measuring thelevel difference involves the inspector setting up
safety barriers on the road and then using a verniercaliper or other tool to take the measurement while
continuing to check for safe conditions (Fig. 4). Thismethod is problematic in that it is necessary to apply
for a permit before conducting the on-site inspection,
safety barriers must be set up to ensure the safety of
the inspector, and local traffic is affected for the duration of the inspection. To address these problems, theNTT Access Network Service Systems Laboratories
developed image-based level difference measurement technology with the objective of achieving asafe and efficient method for inspecting manhole covers.
That technology involves using a commerciallyavailable single-lens reflex camera to acquire imagesof manhole covers. From the images, areas wherelevel differences exist are identified, and the level differences are measured. An advantage of this method
is that the inspection can be done from a distance. The
inspector photographs the manhole cover from the
sidewalk or another safe location with a digital camera, and the acquired image data are transferred to aFeature Articles

Fig. 4. Current method used to measure level differences.

Photographing manhole cover (on-site)
Digital single-lensreflex camera

Measurement by computer (in office)Images (SD card)

ComputerLevel-difference
measurement software
Manholecover

Main screen
Auto-detection of manhole coverSub-image (magnified location of level difference)

Auto-detection of level difference (red line)

Maximum level difference (yellow line)
SD: Secure Digital

Auto-detection of areas wherelevel difference occurs

Maximum level difference value (blue outline)

Fig. 5. Measurement of level difference from image acquired by digital single-lens reflex camera.

computer and stored (Fig. 5). Level-difference measurement software is then used to automaticallydetect the areas in which there is a difference in level
between the manhole cover and the frame in which
the cover sits. The detected areas and the maximum
differences in level are displayed on the screen.
Actual images contain curbs, road marking lines,
gravel, grass, and other irrelevant objects, but thoseobjects can be appropriately eliminated by a new
function that uses texture and color information, thus
reducing detection errors. This technology makes it
possible to measure level differences in manhole covers by simply taking a photograph from a safe location. We plan to begin implementing this technology
in manhole inspection work performed by NTT in2014.
4. Future development
We plan to investigate expansion of the use of automatic inspection technology that grew from thedevelopment of utility pole inspection and diagnosis
technology to manholes, tunnels, and other concrete
structures. Our objective is to apply this technology
broadly so that inspection work can be done safely
and without worry, and inspection costs can be
reduced for all NTT infrastructure facilities. For theinspection of manhole covers, we are also planning toconduct research on automatic inspection technologythat applies the image processing technology
NTT Technical Review

Feature Articles

produced within the NTT laboratories to measure thestate of surface wear—another important maintenance item—from images. Establishing technology
for simultaneous inspection of level differences andwear of steel manhole covers from photographs is

Kazuyoshi Kawabata

expected to greatly reduce the work required for manhole cover inspection and to make such inspections
easier. We also plan to investigate automated inspection technology for facilities that are attached tobridges.

Ryo Yamakado

Group Leader, Concrete Structure Group, Civil
Engineering Project, NTT Access Network Service Systems Laboratories.
He received the B.E. and M.E. in civil engineering from Tokyo Institute of Technology in1988 and 1990, respectively. Since joining NTT
in 1990, he has been engaged in R&D of communications-infrastructure facilities. He is amember of the Japan Society of Civil Engineers(JSCE) and the Japan Concrete Institute (JCI).

Senior Research Engineer, Civil Engineering
Project, NTT Access Network Service Systems
Laboratories.
He received the B.E. in mechanical engineering from Keio University, Tokyo, in 1992. He
joined NTT the same year. He has been engaged
in R&D of communications-infrastructure facilities.

Masato Kikuchi

Hiroyuki Takahashi

Senior Research Engineer, Civil Engineering
Project, NTT Access Network Service Systems
Laboratories.
He received the B.E. in civil engineering from
Meisei University, Tokyo, in 1986. He joined
NTT the same year. He has been engaged in
R&D of communications-infrastructure facilities.

Shoji Mochizuki

Senior Research Engineer, NTT Device Technology Laboratories.
He received the B.E., M.E., and Ph.D. in electrical and electronic engineering from Chuo
University, Tokyo, in 2001, 2003, and 2005,
respectively. He joined NTT Microsystem Integration Laboratories in 2005. From 2005 to 2011,
he was engaged in the R&D of millimeter-wave
and microwave imaging. From 2012 to 2013, he
was active in developing a portable handy scanner based on near-field millimeter-wave techniques for crack inspection of concrete poles. His
current research involves nondestructive testingand diagnosis technology for concrete structures.
He moved from NTT Access Network Service
Systems Laboratories to his current position in
July 2014. He is a member of the Institute ofElectrical and Electronics Engineers (IEEE) andthe Institute of Electronics, Information andCommunication Engineers (IEICE) of Japan. He
received the 2004 International Union of Radio
Science (URSI) Commission B Young Scientist
Award.

Vol. 12 No. 10 Oct. 2014

Senior Research Engineer, Civil Engineering
Project, NTT Access Network Service Systems
Laboratories.
He received the B.S. and M.S. in applied physics from Nagoya University, Aichi, in 2001 and
2003, respectively. He received the Dr.Eng. inelectrical and electronics engineering from
Osaka University in 2014. He joined NTT in
2003. His current research involves inspection
and diagnosis systems for civil infrastructure
facilities. He is a member of the IEEE Microwave Theory and Techniques Society (MTT-S)
and IEICE, Japan. He received the 2008 Young
Engineers Prize presented by EuMIC, the 2010
APMC prize, the 2012 IEEE MTT-S Japan
Young Engineer Award, and the 2012 APMC
prize.

Suguru Kaneko

Engineer, Civil Engineering Project, NTT
Access Network Service Systems Laboratories.
He received the B.E. in quantum and electronicengineering from University of Tsukuba, Ibaraki,in 2002 and the M.E. in physical electronics from
Tokyo Institute of Technology in 2003. He joined
NTT EAST in 2003 and moved to NTT AccessNetwork Service Systems Laboratories in 2008.
He is currently researching maintenance technology for civil infrastructure facilities.

Daisuke Uchibori

Engineer, Civil Engineering Project, NTT
Access Network Service Systems Laboratories.
He received the B.E. and M.E. in civil engineering from Hokkaido University in 2009 and2011, respectively. He joined the Civil Engineering Project, NTT Access Network Service Systems Laboratories, in 2011. His current research
involves inspection and diagnosis technologies
for concrete structures. He is a member of
JSCE.



Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure

Repair and Reinforcement
Technology for Safe and Secure
Concrete Structures that Have aLong Service Life
Kazuyoshi Kawabata, Satoshi Sakai, Taishi Deguchi,
Teiichi Sudo, Naoki Hori, and Takuya Ishikawa
Abstract

A vast number of concrete manhole and tunnel structures managed by NTT are 30–40 years old, andthere is obvious degradation in some of those facilities. To address this problem, the NTT Access Network Service Systems Laboratories has been conducting research and development on the technology
needed to extend facility use long into the future, including technology for more efficient and cost-effective maintenance and management, accurate measurement of the durability of existing facilities, andeffective and economical repair and reinforcement. This article describes the direction and future development of that work.
Keywords: concrete structures, durability evaluation, repair and reinforcement

1. Research and development (R&D) on
manhole maintenance and management
1.1 C
 urrent state of maintenance and management
NTT has about 680,000 manholes throughout Japan(Fig. 1). They serve as connection points for telecommunication cables and hubs for customer lead-in
cables, and they also provide space for maintenancework. The majority of manhole facilities were constructed from 30 to 40 years ago or earlier, and degradation such as concrete cracking, concrete separation, and rebar exposure has become evident in recent
years. Currently, only 6% of all manhole facilities
have been determined to be degraded (Fig. 2); however, a significant number of this group are affectedby rebar corrosion and require repair or reinforcement (Fig. 3). The cost of repairs is expected toincrease as these facilities continue to age.
Because manholes are buried at relatively shallow

depths of from several tens of centimeters to several
meters below the surface of roads, they are susceptible to effects from the weight of vehicles (live load).
There was a large increase in live load with the expansion of goods distribution that followed the period ofhigh economic growth when many of the manholes
were constructed. As a result, even though the facilities were designed to have sufficient strength, somewere subjected to loads beyond what was assumed at
the time of construction.
Accordingly, a method is needed to evaluate durability that appropriately takes into account futureaging of facilities and environmental factors such aschanges in the live load. Additionally, technology foreconomical repair and reinforcement that matches theevaluated durability is necessary.
1.2 R&D direction
The two basic types of manhole structures are steel
reinforced concrete (about 580,000 in service) and
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Feature Articles

50,000800,000
700,000

Number of manholes

40,000600,000

30,000500,000

Single year
Cumulative

400,000

20,000300,000
200,000

10,000100,000
0
Before
1955

1965

1977

1985 1989

1998

0
2012

Fiscal year

Fig. 1. Number of manholes by age of construction.

From inspection dataon 427,977 manholes,
as of 2011

26,917degraded
6%94%401,060in goodcondition

Fig. 2. Number of degraded manholes.

resin block concrete (about 100,000 in service).
Resin block concrete manholes are constructed withhigh-strength resin concrete, and inspection results
show there is relatively little degradation of this type.
Therefore, in our continuing investigation, we aretargeting steel reinforced concrete manholes thathave obvious rebar corrosion. A schematic and aphoto of a steel reinforced concrete manhole areshown in Fig. 4.
The degradation in steel reinforced concrete manholes indicates that rebar exposure that progresses
from cracks occurs mainly on the ceiling and is therefore considered to be an effect of the live load on thefacility.
Furthermore, the resistance to the live load on the
top of the manhole structure is maintained primarilyVol. 12 No. 10 Oct. 2014

by the rebar, so manhole safety and security requires
particular attention to rebar corrosion in the ceiling of
the structure.
Manholes can be broadly grouped into the earliest
reinforced manholes, which conform to the standardsof 1956 and were constructed in a period when traffic
was relatively light, (about 430,000 in service), andthose that conform to the more stringent 1977 standard (about 250,000 in service). Inspections revealthat manholes in the first group account for a relatively large proportion of the degraded facilities, so
we must place priority on that group.
Currently, there are two ranks for degradation, but
the degree of degradation actually varies from facility
to facility. The method of repair and reinforcement
also varies according to the degree of degradation.
Thus, a more detailed degradation ranking system isneeded to lower the repair cost.
Nevertheless, the availability of skilled technicians
is expected to continue to decrease into the future,and consequently, appropriate evaluation of thedegree of degradation by inspectors, and determination of the optimum repair and reinforcement method
are likely to become increasingly difficult.
Therefore, the NTT Access Network Service Systems Laboratories has been developing a simple
method that can be applied on-site for evaluation of
degradation in the top part of the 1956-standard manholes and a method for setting repair and reinforcement criteria based on the degree of degradation.

Feature Articles

Cracking

Separation

Exposed rebar, rustFig. 3. Types of manhole degradation.

Steel cover (above ground)
Steel coverTop
Top
ConduitConduitSide wall

Cable
Bottom

BottomOnly the cover isabove ground.

Manhole model with side removed to show interiorFig. 4. Structure of steel reinforced concrete manhole.

1.3 E
 valuation methods for manhole maintenance(1)	Evaluation of durability by the degree of degradation
On the basis of the assumption that the strength of
the rebar governs the durability of the manhole, we
conducted bending strength tests on a beam model ofpart of the ceiling of a manhole to determine the relation of rebar corrosion to manhole durability. The
results showed that the relation of the amount of rebar
corrosion to the decrease in durability in ordinary
reinforced concrete structures can also be applied to
NTT manholes.
As a simple on-site method of evaluating the durability of manholes, which vary in size and depth
below ground level, we have also been investigating
structural calculations using the known formula
regarding the relation of the amount of rebar corrosion to the decrease in durability for ordinary reinforced concrete structures. This approach holds
promise as a means of setting the criteria for determining when repair or reinforcement is necessary.

(2)	Approach for making appropriate structural calculations for 1956-standard manholes
Road traffic was much lighter when the 1956-standard manholes were built than it is today, so the loadon the manholes was considered to be concentrated.
Later, however, the amount of traffic increased, andthe load on the manholes became more constant andevenly distributed. It thus became necessary to evaluate durability under a distributed load.
A search of the literature for a correction formulafor structural calculations that applies the current
equally distributed load condition produced a way to
do structural calculations for 1956-standard manholes under equally distributed loads. An evaluationof the validity of this approach by a manhole maintenance study group in 2013 showed good prospects forapplicability.
Currently, we are developing a simple calculation
formula that we plan to test in the laboratory with theobjective of establishing a simple, on-site evaluation
method.

NTT Technical Review

Feature Articles

ManholeTunnel (shield)

Fig. 5. Tunnel facilities.

1.4 Future development
Although degradation has been confirmed in only asmall percentage of manholes, it will continue, andincreased degradation is a concern. Because the manholes are buried beneath roads, renovation is not a
simple matter, and we must rely on enhanced maintenance and management to extend the service lifetime.
Furthermore, maximum efficiency is necessary indetermining the present condition of the facilities anddealing with any problems discovered. This isbecause the approximately 680,000 facilities are scattered across the country, the cost cannot simply be
assigned per facility, and the work force is aging. We
are currently working on a simple method of evaluating durability based on the degree of degradation
without using structural calculations. Future R&D
will be aimed at developing reinforcement methods
that renovate the degraded concrete and that havelong-term effectiveness to extend the service life of
the entire manhole facility and achieve higher efficiency in maintenance and management.
2. R&D on tunnel maintenance
2.1 Current state and issues
The deterioration of aging infrastructure facilities is
becoming a problem that affects our whole society.
Forty years or more have passed since the peak periodof NTT telecommunication tunnel construction, andconcerns for the future are growing as concrete degradation increases due to the intrusion of undergroundwater and its corrosive effect on rebar.
Tunnels house the large numbers of cable that leadVol. 12 No. 10 Oct. 2014

out from telecommunication buildings. In an analogy
with the human body, they would correspond to theaorta of the heart. Any problem that arises with thetunnels can affect the entire telecommunication network, so it is crucial to keep these important facilities
in good working order (Fig. 5).
There are two types of tunnels: cut-and-cover tunnels and shield tunnels. Cut-and-cover tunnels areconstructed of steel reinforced concrete and have arectangular cross section. They are built by excavating to a relatively shallow depth of from 5 to 10 m
below the ground surface. Shield tunnels have a circular cross-section and are constructed by boring
through the earth at depths from 15 to 30 m underground using a shield tunneling machine (Fig. 6).
Tunnels range from several tens of meters to several
hundreds of meters in length. There are about 650 km
of telecommunication tunnels in Japan in total, mainly in urban areas, and renovation of these facilities isvery difficult. Accordingly, maintaining safety over along service life and curtailing maintenance costs aremajor issues in maintenance and management.
Cut-and-cover tunnels were constructed in an earlier period than shield tunnels, and degradation suchas rebar corrosion and concrete separation has been
observed in some of them. Therefore, we have carriedout planned maintenance work for the cut-and-covertunnels by setting priorities. Specifically, we optimize the scope and timing of repair work according
to a life cycle cost evaluation based on degradation
criteria and prediction of degradation in steel
reinforced concrete. That work is founded on an
accurate understanding of facility degradation statesFeature Articles

Cut-and-cover tunnel

Shield tunnel
Steel segments

Cable bearer

Steel reinforced concrete

Concrete lining

Fig. 6. Types of tunnel structures.

Progressing

Accelerating
Pre-failure
Rebar corrosion

Failurerust
Neutralization

Put in service

Corrosion (rust)

Cracking

Exposure

Corrosion starts
Years

SafetyDegradation(rebarcorrosion)rebar

LatentConcrete degradation

Life-cycle cost

Preventive
maintenance

Corrective No countermeasures
maintenanceYears

Fig. 7. Optimum repair timing of cut-and-cover tunnels.

obtained using management tools and a periodic
inspection database of inspection results (Fig. 7).
2.2 Direction of R&D
There are several different types of ordinary shieldtunnel structures, but most consist of steel segments
and a concrete lining. Other tunnels that have similar
structures include some sewage tunnels, although
they differ in the materials used and other details, so
the structures are not strictly the same. Therefore,
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Feature Articles

Beam elements• Steel segments• Concrete lining

Spring elements• Load transfer from ground• Beam element responsetransfer

The model makes it possible
to represent the exchange offorces due to differences inrigidity of the ground, steel
segments, and concrete lining
as well as the direction offorce transfer when there iscracking in the concrete.

Fig. 8. Beam and spring analysis model.

R&D concerning evaluation of facility durability andrepair and reinforcement must be done independently.
NTT telecommunication shield tunnels also havethe same basic structure, but they differ in theirdimensions and installation environment. Also, theactual constructions of those tunnels were based on
individual designs. We have been devising required
maintenance measures according to individual
designs while managing individual states according
to inspection results. Our R&D target, however, is tocreate a highly general standard method that is basedon the basic structure and that can accommodate individual environmental conditions. To deal with the
reduced availability of technicians in the future due tothe aging work force, we are developing maintenancetechniques that can be performed simply and easily
by workers who do not require advanced design skills
in order to allow the continued safe use of facilities
with long inspection intervals and without the needfor repeated maintenance.
2.3 E
 valuation method for shield tunnel maintenance and management
Shield tunnels are designed to resist loads acting on
the structure, for example, soil pressure, by the steel
segment alone. The concrete lining is intended toVol. 12 No. 10 Oct. 2014

prevent corrosion and seepage of underground water
into the tunnel. Conventionally, the durability ofcompleted shield tunnels is evaluated by applying thesame design calculation method as that used at thetime of construction. However, it became clear inexperiments conducted with cross-section models of
actual tunnels that the concrete lining also plays a rolein durability. That is to say, use of the design calculation method for tunnel construction to evaluate existing shield tunnels may underestimate their durability.
Therefore, taking the concrete lining into account in
the durability evaluation makes it possible to avoid
excessive reinforcement and to maintain safety economically when considering the necessary reinforcement in the event of degradation due to corrosion ofsteel segments. We have completed the developmentof this new evaluation method.
The new evaluation method for existing tunnels
uses a beam-spring computational model that is used
for the cross-sectional influence analysis. We devised
an analytical model that can reproduce the responsesof steel segments and the concrete lining. That analytical model can also represent the response transfer
due to cracks or non-uniformity in the concrete lining(Fig. 8).

Feature Articles

2.4 Future development
An important future maintenance goal is to reduce
the number of facilities that require maintenance.
One of our current tasks is to develop a repair methodthat effectively extends the service life by making it
possible to prevent water from coming into shieldtunnels over the long term. Water seepage is one of
the factors that necessitate frequent repairs. We arealso working on a method of reinforcing the strengthof degraded parts using a simple and minimum structure.

Kazuyoshi Kawabata

Teiichi Sudo

Satoshi Sakai

Naoki Hori

Group Leader, Concrete Structure Group, Civil
Engineering Project, Access Network Service
Systems Laboratories.
He received the B.E. and M.E. in civil engineering from Tokyo Institute of Technology in1988 and 1990, respectively. He joined NTT in
1990. He is engaged in R&D of communications-infrastructure facilities.

Section chief, NTT InfraNet Corporation.
He received the B.E. in civil engineering from
Ashikaga Institute of Technology, Tochigi, in
1992. He joined NTT in 1992. He is engaged in
R&D of communications-infrastructure facilities. He was previously a Research Engineer in
the Concrete Structure Group working on the
Civil Engineering Project in Access Network
Service Systems Laboratories. He took up his
current post in July 2014.

Branch chief, NTT InfraNet Corporation.
He received the B.E. and M.E. in civil engineering from Kyushu University in 1989 and1991, respectively. He joined NTT in 1991. He is
engaged in R&D of communications-infrastructure facilities. He was previously a SeniorResearch Engineer in the Concrete StructureGroup working on the Civil Engineering Projectin Access Network Service Systems Laboratories. He took up his current post in July 2014.

Senior Research Engineer, Concrete StructureGroup, Civil Engineering Project, Access Network Service Systems Laboratories.
He received the B.E. in civil engineering from
Shibaura Institute of Technology, Tokyo, in 1998
and the Master of infrastructure policy from
National Graduate Institute for Policy Studies,Tokyo, in 2006. He joined NTT in 1998. He is
involved in R&D of communications-infrastructure facilities.

Taishi Deguchi

Takuya Ishikawa

Senior Research Engineer, Concrete StructureGroup, Civil Engineering Project, Access Network Service Systems Laboratories.
He received the B.E. in civil engineering from
Kanazawa University in 1992. He joined NTT in
1992. He is engaged in R&D of communications-infrastructure facilities.



We intend to continue working on capabilities thatare necessary for optimum timing in planned maintenance, including increasing the efficiency of inspection work, applying automation, and improving theaccuracy of methods for predicting the progression of
corrosion and other forms of degradation. In the
future, we will continue to seek an overall picture ofan effective tunnel maintenance cycle and to develop
the optimum solution for operations.

Engineer, Concrete Structure Group, Civil
Engineering Project, Access Network Service
Systems Laboratories.
He received the B.E. and M.E. in geosciencefrom Shimane University in 2007 and 2009,
respectively. He joined NTT in 2009. He is
engaged in R&D of communications-infrastructure facilities.

NTT Technical Review

Feature Articles: R&D on Maintenance and Management
Technologies for Telecommunication Infrastructure

Effective Repair and Reinforcement
Technology for Conduit Facilities
Katsumi Sakaki, Katsuya Takeshita, Koji Tanaka,
Akira Koizumi, Yoshihiko Tashiro, Ryo Seta,
Katsuhiro Tanabe, and Daiki Kobayashi
Abstract

Conduit facilities are located in every part of the country. As the huge number of conduit facilities
deteriorate because of age, the cost of renovation and repair as well as maintenance and management
increases, there is concern that network reliability may decline as a result. The development of conduit
renewal techniques that use new technology and new materials will enable us to achieve the most effective use of conduit facilities and will contribute to reducing costs and maintaining a highly reliable network. This article describes newly developed maintenance and management technologies for buried
conduit and conduit attached to bridges.
Keywords: infrastructure facilities, repair technology, permanence of facilities

1. Introduction
The telecommunication infrastructure supports awide variety of information and telecommunication
services that use telephones and the Internet. Part ofthat infrastructure consists of about 630,000 km ofunderground telecommunication conduit managed byNTT, and 70% of that conduit is at least 30 years old.
A high proportion of old conduit is made of steel
pipe, which has a strong tendency to deteriorate withage, so the number of degraded facilities is expected
to increase. While we are continuing to improve
facilities based on what we have learned from pastmajor earthquakes, most old conduit was designed on
old standards and therefore has low resistance toearthquakes. We must therefore take measures to prevent large-scale damage of these facilities in order toimprove network reliability (Fig. 1).
Maintaining telecommunication reliability throughefficient maintenance and operation of the immense
number of aging conduit facilities is a problem inview of the limited resources. For underground conduit, the steadily progressing facility degradation andthe on-going transition to optical transmission createconcerns about whether there is sufficient space toaccommodate underground cables. To address theseconcerns, we developed and introduced technology
for repairing cable conduit that also creates extra
cable space and improves resistance to earthquake
damage. We are working on applying the technology
to more types of conduit and reducing the repair
cost.
Steel conduit that is attached to bridges is exposed
to various conditions that promote corrosion. These
include repeated wet and dry cycles because of rain,
being sprayed with anti-freezing agents in winter,
exposure to airborne salt in coastal regions, and various other severe environmental conditions. We are
currently developing technology for safely cutting
cable conduit and replacing degraded conduit withcorrosion-free fiber reinforced plastic (FRP) pipe,
which we plan to apply to corrosion-degraded conduit attached to bridges. We are also working ontechnology for reducing OPEX (operating expenses)
by preventing the progression of rusting and extending the effective lifetime of coating materials.

NTT Technical Review

Feature Articles

Problems

Present state of conduit

Steel pipe corrosion(age deterioration)• Facilities installed from 1960s to mid-1980s
are mostly old conduit.
• Old conduit is primarily made of steel pipe.

Corrosion inside pipe hinders
installation of additional
optical cable.
Example of corrosion inside conduit

10

Hardened vinyl pipe
(260,000 km)

Steel pipe
(370,000 km)

Damage from major
earthquake

Conduit

Damage may interrupt
Service.

Optical
cable

5
0

~1
9
~1 56
9
~1 61
9
~1 66
9
~1 71
97
~1 6
9
~1 81
9
~1 86
9
~1 91
9
~2 96
0
~2 01
0
~2 06
01
1

Facilities (10,000 km)

Year of construction
15

Optical cable

Example of earthquake damage

Fig. 1. Current state and problems of conduit.

Current conduit cleaning method
Metal conduit degraded by rust and corrosion is cleaned
with high-pressure water without affecting cable.
High-pressure cleaning device Smaller device
is cheaperand has wider
applicability.

Rust & soil

High-pressurecleaning device

Cable

Large pump truck

Cleaning device withrotating nozzle

Small pump

Fig. 2. Current conduit cleaning technology and new cleaning device.

2. Underground conduit repair technology
New optical cable is being laid in the transition to
optical transmission, and the use of multiline cable(laying multiple cables in a single conduit) is increasing in order to effectively use the limited undergroundcable accommodation space. However, about 52% of
the conduit for which multiline-cable laying isplanned has been diagnosed as degraded by rust or
corrosion to an extent that prevents the use of multiline cable. As a result, roads have been excavated to
add or reroute conduit, and some conduit has been
repaired using the cut-and-cover method.
However, cut-and-cover repairs are expensive andtime-consuming. They also cause many environmental problems such as traffic congestion and noise, andthey result in excess soil remaining after excavation.
Vol. 12 No. 10 Oct. 2014

Therefore, a different solution is needed. We focusedon finding a more effective method to repair steel
conduit that contains optical cable and consequently
developed technology for removing the rust and corrosion that causes degradation. The technology canbe applied while the existing cable remains in place.
We also developed conduit repair and rehabilitation
technology that has wide applicability. These technologies and their most recent states of development
are described in the following sections.
2.1 Technology for cleaning cable conduit
This technology uses high-pressure water to remove
rust and corrosion from conduit that contains cablewithout affecting the cable (Fig. 2). An existing technique is capable of cleaning conduit up to 150 m inlength. However, it requires a large truck equippedFeature Articles• Repair by forming new inner pipe
Installation of repair components creates new space for cables.
1. Assemble

Degraded conduit (steel)

2. Insert
Joint

Pipe for repair(PVC)

Existing optical
cable

Main Rubber joint
unit
Joint

Fig. 3. PIT new conduit repair and renovation method.

with a high-pressure pump that is expensive and has
restrictions on how it can be used in construction. To
overcome these problems, we developed a compact
cleaning unit that can be used for small-diameter
conduit and can accomplish the cleaning with asmaller, general-purpose pump. For effective cleaning with a lower pump output, we devised a rotating
nozzle that has smaller holes, as shown on the rightside of Fig. 2. We also developed a low-friction hose
for cleaning longer lengths of pipe. It can safely workat distances of up to 250 m. This technology expands
the application range, makes the system more flexible
to use, and reduces cost by approximately 30% relative to current methods. The rotating nozzle cleaninghead will be introduced in the second half of fiscal
year (FY) 2014.
2.2 T
 echnology for repair and rehabilitation ofcable conduit
The PIT (pipe insertion type) new conduit method
is used to repair conduit that has existing cable inplace. It uses components that have an upper part andlower part made of PVC (polyvinyl chloride) and thatare assembled around the existing cable. The components are 23 cm long and are connected end-to-end
and pressed into the conduit that is being repaired toform a new pipe (Fig. 3). The entire conduit that is tobe repaired becomes a double pipe, with the pipe
formed by the repair component inside the original
conduit. Even though the outer steel pipe has degraded with age, the inner repair pipe is strong, so theresulting structure is maintenance free. The repair
also has no effect on the existing cable, so there is nointerruption of service during the repair. The repair
involves no excavation of roads and no open cuts, so
it is less expensive and has no negative environmentaleffects. The repair also creates two new cable accommodation spaces, making a total maximum capacityof 3000 cores (1000 × 3). The double structure created by the repair also increases the resistance toearthquake damage and improves facility reliability.
The PIT new conduit method was first introduced
by NTT EAST and NTT WEST in 2012, but its application was limited. For example, the maximum lengthof conduit that could be repaired was 150 m, and it
also could not be used for older, small-diameter conduit. We therefore worked to expand the applicabilityof the technology.
We reconsidered the component design in order toextend the length of conduit that could be repaired.
We also changed the structure so it could better withstand the thrusting force generated when the units arepressed into the conduit being repaired, thus extending the repairable length to 250 m. We also revised
the component structure so it could be applied toolder, small-diameter conduit. The outside diameterof the modified component is smaller, so the cableaccommodation capacity is also smaller. However,
the existing cable accommodation space is also
smaller, (small-diameter, 1000-core optical cable orless), we were able to make the newly created cablespace the same as for current components, thus securing space for 3000 cores (3 small-diameter, 1000core optical cables). In this way, we expanded theapplication range of the PIT new conduit method toolder, small-diameter conduit. We also confirmed thatthe new design can withstand earthquake forces justas well as or better than the current vinyl pipe (Fig. 4).
This technology is planned for commercial introduction in the latter half of FY2014.

NTT Technical Review

Feature Articles

Repair method

Cross section

Φ28 mmNew cable space
Φ23 mm: accommodates
1000-core cableΦ28 mm78 mm

Insertion
Joint

Existing cable space
Φ31 mm: accommodates
existing 1000-core cableΦ35 mmWide application
to old conduit

More compact

Φ28 mmMain unit

New cable space
Φ23 mm: accommodates
1000-core cableΦ28 mm

72 mm
Φ28 mmExisting cable space
Φ23 mm: accommodates
existing 1000-core cableTwo spaces for new cable are created.

Wide application
Length of installation:
150–250 m
Steel pipe with existing cable is repaired with
PVC components consisting of two parts.
Earthquake-proof
Cables are protectedfrom effects of earthquake.

20 cm
15°

Cable
Steel pipe

PIT

Stronger protection
against earthquakes

Fig. 4. Advantages of PIT new conduit method.

• Conduit attached to bridge
Conduit attached to road bridge withmetal fixtures• Special-purpose telecom bridges
Special-purpose girder bridge• Pipe bridges
Bridge over small waterways etc.
supported by strength of pipe

Approx. 36,000

Approx. 3000

Approx. 10,000

Fig. 5. NTT bridge facilities.

3. Technology for repairing conduit
attached to bridges
NTT’s approximately 50,000 bridge facilities
include conduit attached to bridges, special-purpose
telecommunication bridges, and pipe bridges (Fig. 5).
About 20% of these bridge facilities require repairs.
Those that have advanced deterioration due to age arebeing repaired by replacing the conduit, and thoseVol. 12 No. 10 Oct. 2014

that have surface rusting are being repainted. The current replacement repair technique is limited in thelength of conduit that can be replaced due to theinsufficient strength of FRP pipe. Also, when the gap
between conduits is small, there are places where theconduit cannot be cut. We are therefore working on
ways of expanding the range of applications of thistechnique.
The conduit coating technology we are currently
Feature Articles

Current two-piece repair pipe

Hollow rectangle

Cross section

Circular90

ϕ 80

Half-piece

Assembled(Units: mm)

Filament winding
Forming method

Newly developed repair pipe

104

ϕ 80

Formed part

91
Assembled(Units: mm)

Pultrusion

Metal form
Fiberglass cloth

Fiberglass cloth
Rotation

Metal form
Pull

Resin

Resin

Fig. 6. Comparison of repair pipe structures and forming methods.

using involves the use of an economical and commercially available coating technique. However, thistechnique cannot keep up with the increasing quantityof age-degraded conduit, so we are developing technology for greatly extending the service life of conduit coatings. These technologies are described
below.
3.1 Replacement-repair technology
The replacement technique to repair corrosiondegraded cable conduit attached to bridges involves
replacing the corroded section of the steel pipe with
two-piece FRP repair pipe. This technique was introduced commercially in FY2008. However, the application of this technique was limited to conduit where
the distance between supports was L = 2.5 m or less.
The main reason for this restriction is that the rigidityof the currently used two-piece repair pipe is insufficient to satisfy the permissible deflection (L/300 orless) under load (cable and snow). Applying the current technology with additional supports deviatesfrom the original bridge design, so it is often not possible to obtain permission to modify the structurefrom the road managing authority, and such repairs
then cannot be done.
To solve this problem, we developed long andhighly rigid FRP repair pipe that can be used toextend the replacement-repair technique to cable conduit where the distance between supports (L) is up to
5.5 m. The current repair pipe has a circular cross section and is formed by the filament winding method,in which fiberglass cloth is wrapped circumferentially. However, the cross-section shape and material
rigidity of this method does not provide sufficientstrength for repairs longer than L = 2.5 m, as describedabove. Furthermore, a process for splitting the formed
pipe into two pieces is required, which adds to the
manufacturing cost. By developing a repair pipe thathas a hollow rectangular cross section, we efficiently
increased the cross-sectional rigidity. This new repair
pipe is formed by pulling fiberglass cloth out in theaxial direction of the pipe, thus increasing the material rigidity against perpendicular loads. This is called
the pultrusion method, and it can be applied to any
cross-section shape, so formed parts that have leftright symmetry can be assembled into repair pipe,
thus eliminating the splitting process and reducing
the manufacturing cost (Fig. 6).
This repair pipe is strong and highly resistant tobending and degradation. It is called ST-LONG pipe,
which is derived from square-type, long length FRP
pipe. Also, to reduce the splitting cost, we adopted thepultrusion method for the insertion sockets, which areused for joining ST-LONG pipe and existing steel
NTT Technical Review

Feature Articles

Insertion socket

ST-LONG pipe

Stainless steel (SUS304) band

Fixed end

Expansion/contraction end
Support interval: 2.5–5.5 m
Pull Push
16 cm 11 cm

The same amount of expansion/contraction
as current expansion joints

Fig. 7. New repair technology.

pipe to complete the replacement repair.
Because the old facilities to which replacement
repair is applied have little capacity for expansion andcontraction, there is concern about possible damage
due to disconnection or buckling at the joints in an
earthquake. We therefore designed the joints to havethe same amount of expansion and contraction as current expansion joints, thus improving their resistanceto earthquake damage in addition to enabling completion of the repair (Fig. 7).
The results of testing prototype ST-LONG pipe andinsertion sockets for bending, strength, and vibration
resonance with bridge structures confirmed that thedeveloped components satisfy the permissible deflection at L = 5.5 m and that the strength and resistanceto resonance effects are sufficient. We also evaluatedrepair workability with a model for conduit attached
to a bridge. The results showed that the developed
components provide good workability for multiple
cable-conduits.
3.2 E
 xpanding the applications of conduit cutting
technology
In places where the gap between conduits is lessthan 30 mm, the corroded part cannot be cut out andremoved, so the current two-piece FRP repair pipe
cannot be used for replacement repair in such cases.
Conduit attached to bridges is installed densely
because of the limited space, so narrow gaps between
Vol. 12 No. 10 Oct. 2014

conduits are common. Replacement repair is performed using three main steps.
Step 1) Check whether or not conduit has cable.
Step 2) Cut and remove degraded conduit.
Step 3) Attach repair pipe.
The reason the corroded parts often cannot be cut
and removed in step 2 is that current pipe cutting tools
cannot be inserted into the narrow gap between the
conduits. Also, the cutting is done manually using
existing cutting tools, and this is inefficient for onsite work.
The technology we developed uses a low cutting
blade height to achieve a low-profile pipe cutter (thinform tool). The cutting unit is constructed of fivesegments and can easily be inserted into narrow gaps.
As a result, the unit can be inserted into a gap as small
as 12.5 mm, which is the narrowest gap assumed forplaces where conduit joints are installed in an alternating configuration. Furthermore, higher cutting
efficiency is achieved by using a rotating cutter thathas a gear mechanism driven by an electric drill.
Whereas the current cutting tool requires about 15
minutes to make one cut in a conduit, this thin-form
tool requires only about 5 minutes (Fig. 8).
Another problem with the current cutting method isthat there is no protection for the cable inside theconduit. The reason for the lack of protection is thedifficulty of inserting a protector into the conduit. To
solve this problem, we developed a simple and sureFeature Articles

Blade

Gear unit

Jig

Tool thickness:
10.5 mm

Cutting unit

Five-segment toolwith low cutting blade
height can be usedin 12.5-mm gaps.

12.5 mmJoint
Conduit
Alternating joints;
narrow gap

Thin-form tool

Cutting unit (5-segment structure)

ConduitThin-form tool
Cross section

Electric drill-driven-gear rotating
mechanism makes cut in about 5 min.

Pipe cutting

Fig. 8. Pipe-cutting tool (thin-form tool).

cable protection method to apply when the thin-form
cutting tool is used. The method involves inserting along, narrow protector through the hole used to checkfor cable in step 1 so that it wraps around the cableinside the conduit and keeps the cable away from theedge of the cutter blade. This prevents contact
between the blade and the cable, ensuring protectionof the cable during the cutting process. The protector
is inserted by using a hammer in an operation that iseasy to do even with thick and heavy cables. We
evaluated a variety of materials for ease of insertion,
strength, and cost, and selected 5.0-mm-thick polyethylene foam sheeting as a sample material to be
used for the cable protector (Fig. 9). Commercial
introduction of this protection technique for use
together with the replacement repair techniquedescribed above is planned in FY2014.
3.3 Coating repair technology
Conduit that has superficial rusting where the corrosion is not severe is repaired by removing the rustand coating the affected area with polyurethane paintto prevent further corrosion. The purpose of repairing
the conduit at the stage of light rusting is to halt the

progression to the stage of corrosion degradation inwhich replacement is necessary. Currently, threecoats of a polyurethane resin and epoxy resin rustproofing agent are used. The coating is effective for
10 to 15 years, but this approach cannot keep up with
the increasing number of deteriorating facilities.
We are therefore working on rust-proofing technology that remains effective for 40 years or more. The
results of accelerated degradation tests performed incooperation with the NTT Energy and Environment
Systems Laboratories indicated that oil-based rustproofing using wool wax is effective (Fig. 10). We
found that rusting progressed after 2000 hours for
currently used coatings (polyurethane resin), butthere was no rusting after 6000 hours with an oilbased coating, which confirmed an improvement indurability by a factor of three or more.
The results of temperature and coating thickness
tests showed that securing the target lifetime of 40
years requires a thickness of at least 0.5 mm of acream-type oil-based rust-proofing agent. However,that type of rust-proofing agent does not harden, so it
would be difficult to maintain the required thickness
over the required period of time. We are therefore
NTT Technical Review

Feature Articles

Protector

Holes to insert punch

HammerProtector

Punch

Cable

Cable

Cable-checking holeProtector

Cutting blade ofthin-form tool
Protector is inserted throughthe cable-checking hole by striking
a punch with a hammer.

Protector wraps around the cable,
keeping it away from the edge of the cutter blade.

Fig. 9. Cable protection method.

No rustinhibitor

Oil-based rustinhibiting coating
Covering

Before test

After test
(6000 hours)
Equivalent to 30
to 45 years of
rust

Rusting

No new rust or
progression of rustingFig. 10. Accelerated degradation test over 6000 hours.

investigating methods for using oil-based rust-proofing on conduit attached to bridges. Currently, therequired coating thickness can be maintained byusing cloth impregnated with the oil-based rustproofing agent that is wrapped around the conduit.
Therefore, we are continuing our efforts towards
making this technique practical for use on bundledfacilities and in places where the gap between conduits is small, aiming for commercial introduction in
FY2015.

Vol. 12 No. 10 Oct. 2014

4. Future issues and prospects
Most of the NTT conduit facilities are buried
beneath roads. Work on repairing or widening roads,
sidewalk maintenance work, or work done on theunderground facilities of other companies may disturb existing NTT conduit facilities or result in theneed to relocate them. For spans that cross rivers, thefacilities may also need to be relocated when NTT
conduit attached to bridges and bridge facilities arerebuilt, reinforced against earthquakes, or painted.
We are also working on technology for reducing
construction costs in order to deal with facility relocation. For cases in which new facilities are constructed after relocation, we will continue to investigate simple and economical facility designs that can
flexibly cope with changes in capacity and transmission medium specifications, keeping future all-optical transmission in mind.
The increasing number of NTT conduit facilities
that are degraded by aging and other factors remain aconcern for the future. We will continue developing
new technology to solve such problems and contribute to achieving higher network reliability.

Feature Articles

Katsumi Sakaki

Research Engineer, Civil Engineering Project,
NTT Access Network Service Systems Laboratories.
He received the M.E. in information engineering from Nagoya University in 2006. He joined
NTT in 2006 and has been working on maintenance of access networks. In 2008, he moved to
NTT InfraNet and was engaged in developing
optical fiber sensing. In 2010, he moved to NTT
EAST, where he was engaged in human resources development. In 2013, he moved to NTT
Access Network Service Systems Laboratories.
He is currently involved in developing technology for maintaining conduits attached to bridges.

Katsuya Takeshita

Ryo Seta

Senior Research Engineer, Pipeline System
Technology Group, Civil Engineering Project,
NTT Access Network Service Systems Laboratories.
He received the B.E. in civil engineering from
Kumamoto University in 1992. He joined NTT in
1992 and has been with the NTT Access Network
Service Systems Laboratories since 2011. He is
engaged in R&D of persistence technologies forburied conduit.

Koji Tanaka

Senior Research Engineer, Pipeline System
Technology Group, Civil Engineering Project,
NTT Access Network Service Systems Laboratories.
He received the B.E. and Ph.D. in civil andenvironmental engineering from University of
Yamanashi, in 1990 and 2013, respectively. He
joined NTT in 1990 and developed trenchless
repair technologies for underground pipeline
systems. He moved to NTT Access Network
Service Systems Laboratories in 2012. He is currently researching earthquake proofing technology for underground pipeline systems. He is amember of the Japan Society of Civil Engineers.

Akira Koizumi

Research Engineer, Pipeline System Technology Group, Civil Engineering Project, NTT
Access Network Service Systems Laboratories.
He received the B.E. in civil engineering fromMusashi Institute of Technology (now Tokyo
City University), Tokyo, in 1991. He joined NTT
in 1991 and has been with NTT Access Network
Service Systems Laboratories since 2011. He iscurrently engaged in R&D of maintenance technology for aging telecommunication infrastructure facilities.

Yoshihiko Tashiro

Branch Manager, NTT InfraNet Hokuriku
Branch.
He received the B.E. in civil engineering fromMusashi Institute of Technology (now Tokyo
City University), Tokyo, in 1988. He joined NTT
in 1988. He is engaged in R&D of communications-infrastructure facilities.

Engineer, Pipeline System Technology Group,
Civil Engineering Project, NTT Access Network
Service Systems Laboratories.
He received the B.E. and M.E. in informationand communication systems engineering from
Tokyo Metropolitan University in 2008 and2010, respectively. He joined NTT EAST in
2010, where he was mainly engaged in troubleshooting of home networks in Fukushima. In
2012, he moved to NTT Access Network Service
Systems Laboratories. He is currently involved indeveloping repair technologies for conduits
attached to bridges.

Katsuhiro TanabeEngineer, Pipe System Technology Group,
Civil Engineering Project, NTT Access Network
Service Systems Laboratories.
He received the B.E. from the Interdisciplinary
Faculty of Science and Engineering, Shimane
University, in 2010. He joined NTT WEST in
2010, where he worked on the Grand Design
Osaka infrastructure project. In 2012 he moved
to NTT Access Network Service Systems Laboratories. He is engaged in R&D of persistence
technologies for buried conduit.

Daiki Kobayashi

Engineer, Pipeline System Technology Group,
Civil Engineering Project, NTT Access Network
Service Systems Laboratories.
He received the B.E. in agriculture from Meiji
University, Kanagawa in 2011 and the M.E. inagriculture from the University of Tokyo in 2013.
He joined NTT Access Network Service Systems
Laboratories in 2013. He is currently conducting
research on bridge inspection technology.

NTT Technical Review

Regular Articles

Frequency-division-multiplexing
Coherent OTDR for Realizing
Effective Construction and
Maintenance of Submarine Optical
Cable Systems
Hiroyuki Iida, Kunihiro Toge, and Fumihiko Ito
Abstract

We have developed a novel coherent optical time domain reflectometry (C-OTDR) technique with thehighest level of measurement sensitivity yet reported, thus enabling us to achieve the effective
construction and maintenance of submarine optical cable systems. Our technique minimizes theoperating time required during measurement. This article provides an overview and reports the featuresof our new technique, which we call frequency-division-multiplexing coherent OTDR (FDM-OTDR).
Keywords: C-OTDR, submarine cable, fiber measurement

1. Introduction
Submarine optical cable systems have been constructed and upgraded recently by employing noveltransmission techniques such as digital coherent optical transmission in order to meet the demand for
rapidly growing data traffic over optical trunk networks. Submarine optical cable systems are classified
into two categories. One consists of repeatered systems for long-haul applications, which transmit signals over several thousand kilometers by using optical amplifiers (erbium doped fiber amplifiers(EDFAs)) and power feeding through submarine
cables. The other consists of repeaterless systems for
short-distance applications of up to several hundred
kilometers. The fiber conditions in long-distance submarine optical cables need to be evaluated at various
times including during an acceptance inspection andshipping of the cables, in a final inspection after laying the cables, and when identifying fiber faults during operation. Coherent optical time domain reflectometry (C-OTDR) [1] is normally used in such evalu

ations. C-OTDR is a mature technique with superiorsensitivity and good characteristics for eliminating
amplified spontaneous emission noise from opticalamplifiers by employing coherent detection.
2. Problem with conventional C-OTDR
Submarine cable systems typically have long
repeater spans for repeated systems, or a long transmission length in repeaterless systems, thanks to optical amplifiers with high total output power and lowloss optical fibers with large effective areas. C-OTDR
is sensitive up to the shot noise limit of the receiver.
However, one problem is that the dynamic range(DR) is sometimes insufficient when we evaluate theentire length of such submarine optical cable systems(Fig. 1). With C-OTDR measurement, a lot of time isneeded to conduct a large number of iterations foraveraging in order to obtain a good signal-to-noise
ratio (SNR) in OTDR traces. Therefore, it is important to extend the DR in C-OTDR in order to minimize the operating time needed for cable inspection.
NTT Technical Review

Regular Articles

Probe light

Repeater

Optical fiber
Upstream line Bypass forbackscattering
light
Downstream line

C-OTDREDFA

Backscattering light25
Unable tomeasure due
to noise

Reflectivity (dB)

20

15

10

5

0

0

50

100

150
Distance (km)

200

250

300

Fig. 1. Configuration of submarine optical cable system and overview of measurement of submarine optical cable using
C-OTDR.

3. DR enhancement method for C-OTDR
The easiest way to extend the DR is to increase thepeak power of the probe pulse from the C-OTDR.
However, this does not apply to repeatered systems
because the output power from the repeaters is
restricted by the automatic level control function of
the repeater itself. The frequency-division-multiplexing coherent OTDR (FDM-OTDR) technique wedeveloped employs multi-frequency-coded probe
pulses instead of the single-frequency pulse used inconventional C-OTDR [2]. The basic concept of our
FDM-OTDR is shown in Fig. 2. A probe pulse train
with N-multiple frequencies is launched into thefiber. Each frequency component is serially arrangedin the time domain. These components are detectedby a single photodetector, and they provide multiple
OTDR traces measured at different frequencies by afast Fourier transform (FFT). As a result, we cansimultaneously obtain multiple OTDR traces measured at different frequencies. This means that OTDR
traces with an SNR improved by N can be obtained
within a single iteration of the measurement. In otherwords, an OTDR trace with the same SNR can beVol. 12 No. 10 Oct. 2014

obtained during an Nth part of the measurement timeby using FDM-OTDR. This concept was proposed by
NTT several years ago [3]. However, it required a
modulator in which the probe frequency could becontrolled precisely and rapidly, as well as manyelectronic devices at the receiver for demultiplexing
the signal, which has prevented the realization of apractical system for commercial use.
4. FDM-OTDR
An overview of the FDM-OTDR configuration wedeveloped is shown in Fig. 3. The probe frequency ofa continuous wave (CW) from one narrow-linewidthlaser is controlled by an external modulator. On thereceiver side, Rayleigh backscattering light with multiple frequencies is detected by a single coherent
receiver and digitized with an analog/digital (A/D)
converter. With FDM-OTDR, a digitized signal isdemultiplexed by digital signal processing, whichindicates that many electronic devices are notrequired. Therefore, FDM-OTDR is comparable toconventional C-OTDR in terms of size and cost. The
details of the FDM-OTDR scheme are as follows.
Regular Articles

f1 f2Rayleighbackscattering

Probe pulse

fN

Multi-frequency
coded probe
pulse

Multi-frequency
backscatteringTime

FDM-OTDRC-OTDRTime

Time
Iteration and multi-frequency averaging

Reflectivity (dB)

Reflectivity (dB)

Iteration and averaging

10log N dB(a) C-OTDR(b) FDM-OTDR

Noise level

Fig. 2. Principle of FDM-OTDR.

f1 f2

fN
Optical fiber under test
Time
Fourier transform

SSB
modulator
Coherent
receiverNarrow-linewidthlaser

A/D converter
and PC

Local light

CW light source(Coherence > 10 µs)

Generation of frequency
code by external modulator

Real-time demultiplexing
by digital signal processing

PC: personal computer
SSB: single side band

Fig. 3. Configuration of FDM-OTDR.

4.1 Frequency-coding of probe pulse
The frequency coding of a probe pulse on the transmitted side is shown in Fig. 4. It is performed with
kHz-order accuracy by using an optical single sideband (SSB) modulator. The optical SSB modulator iscontrolled by using bias adjustment to modulate only
the +1st order (or −1st order) component, and to suppress the carrier frequency component (CW fromnarrow linewidth laser) and higher order side-band
components. The probe frequency is changed with aduration corresponding to the spatial resolution(namely, the pulse width in conventional C-OTDR).
The number of multiplexed frequencies is limited by
the receiver bandwidth. The frequency interval of the
NTT Technical Review

Regular Articles

Carrier+1st order side band

f1

(γ+)

f2
f3
γ

f2

f3

Time

OpticalSSB
modulator

Arbitrary signal
generator

f1

Opticalfrequency

Modulated probe

Modulated frequency

Narrowlinewidth
laser

Frequency-coded pulse train

Duration for eachfrequency (corresponds
to pulse width)

Frequency
interval

f3
f2
f1
1

2

3
Time

Fig. 4. Generation of frequency-coded pulse train in FDM-OTDR.

multiplexing is optimally designed in the receiver
bandwidth to suppress crosstalk between frequency
channels.
4.2 F requency demultiplexing by digital signal
processing
Rayleigh backscattering with multiple frequencies
is detected and then digitized when a frequencycoded probe pulse is launched into an optical fiber
under test (FUT). The digitized backscattered signals
can be separated into each frequency component withan FFT. This signal processing is performed in realtime during the round-trip time of the frequency
coded probe pulse in the FUT, and it then provides theaverage OTDR trace from N OTDR traces. Consequently, FDM-OTDR requires significantly fewer
iterations because the SNR in an OTDR trace with
one iteration can be improved by N .
4.3 Design of inter-channel crosstalk
The design of the inter-channel crosstalk in FDMOTDR is very important because it appears as a distortion in an OTDR trace. Schematic illustrations of
the distortion in an OTDR trace caused by inter-channel crosstalk are shown in Fig. 5. When we measuresubmarine cable systems, the reflectivity is precipitously changed with twice the gain (in dB) of therepeater. If the effect of inter-channel crosstalk greatly exceeds this reflectivity change, the shape of theVol. 12 No. 10 Oct. 2014

OTDR trace in front of the repeater broadens asshown in the figure. This broadening in the OTDR
trace can be considered degradation of the fundamental performance of OTDR measurement with respect
to spatial resolution. Therefore, suppression of interchannel crosstalk is an essential issue in FDM-OTDR.
With our developed FDM-OTDR method, we
employed an appropriate digital filtering technique tosuppress the side lobes of the detected signals during
processing. We also realized the optimal design of thefrequency intervals to achieve the allowable interchannel crosstalk and thus maintain a sufficient levelof spatial resolution.
5. Characteristics in FDM-OTDR
Here, we introduce an example of the measurement
results we obtained using the FDM-OTDR techniquewith 40-frequency-multiplexing that we developed.
The results of OTDR traces obtained for conventional C-OTDR and FDM-OTDR are compared inFig. 6. The measurement conditions are the same interms of iteration number (213) and spatial resolution(1 km). It can be seen from the figure that the roundtrip DR of FDM-OTDR improved by about 7.8 dB,
which agrees well with the theoretical improvementof about 8 dB (≈ 10log N ). This means that thesame SNR performance can be obtained in about 1/40
the measurement time by using FDM-OTDR.
Regular Articles(a) Suppressed inter-channel crosstalk(b) Unsuppressed inter-channel crosstalk

Repeaters
Distortion
Reflectivity

Reflectivity

Fresnelreflection

Distance

Distance

Normal OTDR trace

Distorted OTDR trace

Fig. 5. Effect of inter-channel crosstalk on OTDR trace.

20
C-OTDR
40-frequency multiplexed
FDM-OTDR

Reflectivity (dB)

0

−20

−40
7.8 dB

1550 nm
−60

0

100

200
300
Distance (km)

400

500

Fig. 6. Sample measurement result by FDM-OTDR.

An OTDR trace obtained in front of the last repeater is plotted in Fig. 7(a), in which a huge change inthe reflectivity is observed. Although we can see amarginal effect of inter-channel crosstalk when wecompare conventional C-OTDR and FDM-OTDR
traces, the inter-channel crosstalk is suppressed bymore than 36 dB. In the Fresnel reflection in the trace
obtained with FDM-OTDR at the far end of the FUT(Fig. 7(b)), it can be seen that the inter-channel crosstalk does not degrade the spatial resolution, and that
we obtained the designed performance with 1 km for
3-dB spatial resolution.
As described above, our FDM-OTDR techniqueenables us to minimize the measurement time without any degradation in spatial resolution.



6. Future perspectives
This article introduced FDM-OTDR with 40-frequency multiplexing, which can minimize the operating time required during the construction and maintenance of submarine cable systems. The softwarebased processing in the FDM-OTDR benefited fromrecent increases in the capacity of computer processors. We have also reported 200-frequency-multiplexed FDM-OTDR [4]. The FDM-OTDR performance, namely, the number of multiplexed frequencies, strongly depends on the performance of the
hardware, for example, the A/D converter and computer processor. Noteworthy recent progress has been
made on an A/D converter with a broad bandwidthand a field programmable gate array for high-speed
FFT implementation. The FDM-OTDR can potentially evolve further by employing such progress. We
NTT Technical Review

Regular Articles

C-OTDR
40-frequency multiplexed FDM-OTDR
Fresnel reflection

Repeater
30
10

(a)

(b)
20
36

Reflectivity (dB)

Reflectivity (dB)

0
−10
−20
−30

3-dB resolution:< 1 km

10
0
−10

−40
320

330

340
350
360
Distance (km)

370

380

−20
396

398

400

402 404 406
Distance (km)

408

410

Fig. 7. Enlarged view of OTDR traces (a) in front of repeater, (b) at Fresnel reflection.

expect FDM-OTDR to be deployed for practicalapplications in the near future since a short measurement time is advantageous with respect to reducing
the construction and operating costs of submarine
networks.
References[1]

H. Izumita, “Coherent OTDR Technology,” O plus E, Vol. 24, No. 9,
pp. 974–979, 2002 (in Japanese).

Vol. 12 No. 10 Oct. 2014

[2]

[3]
[4]

H. Iida, Y. Koshikiya, F. Ito, and K. Tanaka, “High-sensitivity Coherent Optical Time Domain Reflectometry Employing Frequency-division Multiplexing,” Journal of Lightwave Technology, Vo1. 30, No. 8,
pp. 1121–1126, 2012.
M. Sumida, “Optical Time Domain Reflectometry Using an M-ary
FSK Probe and Coherent Detection,” Journal of Lightwave Technology, Vo1. 14, No. 11, pp. 2483–2491, 1996.
H. Iida, K. Toge, and F. Ito, “200-subchannel Ultra-high-density Frequency Division Multiplexed Coherent OTDR with Nonlinear EffectSuppression,” Proc. of Optical Fiber Communication Conference,
Anaheim, CA, USA, March 2013.



Regular Articles

Hiroyuki Iida

Research Engineer, Access Media Project,
NTT Access Network Service Systems Laboratories.
He received his B.E. in physics from Nihon
University, Tokyo, in 2006, and his M.E. in physics from the University of Tokyo in 2008. He
joined NTT Access Network Service Systems
Laboratories in 2008. He has been engaged inresearch on optical reflectometry and opticalmeasurement. He is a member of the Institute ofElectronics, Information and Communication
Engineers (IEICE).

Kunihiro Toge

Senior Research Engineer, Access Media Project, NTT Access Network Service Systems Laboratories.
He received his B.E. and M.E in mechanicalengineering and his Ph.D. in electrical engineering from Waseda University, Tokyo, Japan, in
1999, 2001, and 2007, respectively. He joined
NTT Access Network Service Systems Laboratories, where he has been engaged in research on
optical fiber cable and optical fiber measurements. He has also been engaged in standardization work in ITU-T SG15 (International Telecommunication Union, Telecommunication
Standardization Sector, Study Group 15) since2012. He is presently a senior research engineer
in a research group developing future opticalmeasurement technology for fiber network management and evaluation. Dr. Toge is a member of
IEICE. He received the best paper award at the12th OECC/IOOC (OptoElectronics and Communications Conference and International Conference on Integrated Optics and Optical Fiber
Communication) in 2007.



Fumihiko Ito

Senior Research Engineer, Supervisor, AccessMedia Project, NTT Access Network Service
Systems Laboratories.
He received his B.E. and Ph.D. in electricalengineering from the University of Tokyo, in1985 and 1999, respectively. Since joining NTT
in 1985, he has been engaged in various areas ofresearch on optical fiber communication systems
and optical devices. His work includes semiconductor optical switches, holographic opticalmemory using photorefractive effects, opticalneural networks and their application to communication systems, and coherent optical signal
processing for ultrafast communication. Since
2000, he has been with NTT Access Network
Systems Laboratories and has worked in the fieldof ontology-based network operation. Currently,
he is supervising a research group developing
future optical measurement technology for fiber
network management and evaluation. Dr. Ito is amember of IEICE.

NTT Technical Review

Regular Articles

Development of Long-span Aerial
Cable Installation Technique(Long Hanger Method)
Katsuhisa Kawaguchi, Ryosuke Yasui, Ryoichi Kaneko,
Kunihiro Shimokubo, Kazutoshi Takamizawa,
and Yuji Aoyagi
Abstract

We have developed a technique called the long hanger method for installing a long span aerial cable
across, for example, a valley or river without using conventional methods that require special skills or
installation tools. Our new method enables us to easily overlay or replace cables.
Keywords: long-span aerial cable installation, rural area, overlay/replace cables

1. Introduction
When optical services were being developed for
NTT EAST and NTT WEST, optical equipment was
deployed throughout the country. Facilities werealready adequate in most urban areas, so the development of rural areas was planned for the future. The
environment in rural areas is different from that inurban areas in terms of the distances between NTT
buildings and customer premises, as well as customer
density. Therefore, we require components andinstallation methods that are suitable for rural environments. An example is the aerial cable installation
technique used for 200- and 250-m long-span sections over valleys or rivers. Conventionally, we use acatenary method or a lashing method, but they giverise to the following two problems.
(1) Installation
The catenary method requires a special skill (theability to do aerial work) for construction to be completed safely (Fig. 1). The lashing method requires a
special tool (lashing machine). The widespread application of this tool ended decades ago, and it is now
only required for long-span sections (Fig. 2). Today,
few engineers have the skill required to do aerial

work, and lashing machines that meet NTT specifications are no longer produced. Therefore, it will bedifficult to continue using these methods in the future.
In addition, the catenary method was used for cable
restoration work after the Great East Japan Earthquake, and it took a long time to secure the required
personnel and to conduct the preparatory work forbuilding the facilities. Therefore, new technology isneeded that can reduce the cable restoration time.
(2) Components
With these conventional methods, overlaying or
replacing a cable takes an equivalent amount of timeas that originally needed to install the same components because of the difficulty in installing an additional cable.
We have developed the long hanger method as asolution to these two problems.
2. New development concept
We first explain the problems regarding the catenary and lashing methods. The components used withthe catenary method consist of two messenger wires(a main messenger wire and a sub-messenger wire), a
NTT Technical Review

Regular Articles

Lashing machine
Aerial work

Fig. 1. Catenary method.

Fig. 2. Lashing method.

Main
messenger
wire Cable
Cable ring
Main messenger
wire

Sub-messenger
wire

Pulley for cabling

Cable ring Cable

Aerial work apparatus

Fig. 3. Equipment and installation using catenary method.

cable, and cable rings (Fig. 3). It is necessary to do
aerial work (i.e., to work in mid-air) using a speciallydesigned apparatus when fixing the main messenger
wire to a sub-messenger wire during the temporary
installation of a cable, and when attaching cablerings. This is also the case when we install an additional cable, where we must remove and reattach
cable rings individually. This means that it takes along time to install an additional cable. Replacing thecable takes even more time because we have to
remove the cable in addition to carrying out the above
process.
The lashing method was developed to eliminate theneed for aerial work. The lashing method employs amessenger wire, a cable, and a lashing wire (Fig. 4).
In the installation, we first place a lashing wire in alashing machine and then fix a messenger wire and aVol. 12 No. 10 Oct. 2014

cable in place with the lashing wire. The lashingmachine can be used over a long-span section, so
aerial work is not required. However, lashingmachines that meet our specifications are no longer
being produced, and therefore, we cannot continue to
use this method. In addition, if we overlay a cableusing the lashing method, it will be necessary to carryout the installation of a messenger wire, a cable, anda lashing wire as if it were a new installation, which
would take a long time. Replacing the cable takes
even more time because we have to remove the existing cable in addition to completing the above installation process. Our aim with the long hanger method
was to employ the binding hanger used for conventional aerial sections and create a space in which we
can overlay and remove cables freely without theneed for aerial work or a special tool. We developed aRegular Articles

Messenger
Cable
Lashing wire wire

Messenger wire

Lashing
Pulley formachinecabling

Lashing wire

Fig. 4. Equipment and installation using lashing method.

Messenger wire
Binding hanger
Binding hanger

Messenger wire

SS cable
Additional cable
SS cable
Image showing space available
for installed cable

SS: self-supporting

Fig. 5. Equipment used in long hanger method.

safe installation technique for 250-m spans andhighly reliable equipment that can be used in various
environmental conditions such as strong winds.
3. Required components
The components required for the long hanger
method include a messenger wire, a binding hanger,
and cables (Fig. 5). The role of the messenger wire isto support the load of all components as well as theload applied by wind pressure. The binding hanger
creates a space in which we can freely overlay or
remove cables. From several types of binding hangers, a cosine curve hanger (CCH) is used in this

method because it can be coiled up compactly even if
it is long. A stopper is used to fix the CCH to the messenger wire, which further improves the reliability(Fig. 6). This stopper prevents the CCH from moving
away from the messenger wire and prevents cablesfrom falling out of the CCH because the internal
space of the CCH is enclosed. A self-supporting (SS)cable is used to prevent fiber movement and fiber
strain.
4. Installation
In a standard aerial section, we first install a messenger wire and then a CCH by pushing the CCH out
NTT Technical Review

Regular Articles

Messenger wire
Stopper

Cable

CCH

Fig. 6. Stopper installation.

along the messenger wire from a given pole. However,
if we want to install a CCH in a log-span section, we
cannot get it all the way over to the other pole because
the friction against the messenger wire increases witha slack and steeply pitched messenger wire. Alternatively, when we pull a CCH from one side, it can be
stretched as a result of the large tension. This reduces
the internal space of the CCH and makes it impossible
to overlay and replace cables.
With the long hanger method, we install a messenger wire and a CCH simultaneously. This approach
reduces the tension on the CCH and makes it possible
to get the CCH all the way over to the other side. The
procedure is as follows:(1)	A light rope is first installed between the poles(the same process as in the conventional method).
(2)	Two ropes are then installed between the poles
by connecting them both to the first light ropeand pulling it. (Fig. 7(a)).
Rope A: messenger wire
Rope B: SS cable	Wiring rings are used to lift rope B across a longspan.
(3)	A messenger wire and a CCH are installed bypulling rope A and adding stoppers (Fig. 7(b)).
Rope B is fixed to the poles, and it prevents themessenger wire and CCH from falling down
between the poles of the long span section. A
conventional winch can be used for this process
because rope B can reduce the tension needed topull the messenger wire and the CCH.
(4)	Tension is applied to the messenger wire, whichis then fixed to the poles; a space has been
included for freely overlaying and removing
cables.
(5)	An SS cable is installed by connecting it to rope
B and then pulling on rope B (Fig. 7(c)).
(6) The SS cable is fixed to the poles.
Vol. 12 No. 10 Oct. 2014(a)Direction
Rope A

Light rope

Rope B
Winch(b)Wiring ring
CapstanDirection
Rope B
CCH

Stopper

Messenger
wire

Rope A(c)

Direction
Cable

Rope B

Fig. 7. Installation using long hanger method.

Regular Articles

5. Overlaying/replacing a cable

6. Conclusion

In a conventional aerial section, when we overlay orreplace a cable, we use a wiring method that involves
pushing a shuttle that carries the wire from one sideand passing it through the CCH. However, we cannot
use this approach in a long-span section because the
shuttle falls from the CCH as a result of the large
amount of slack. Therefore, we adopt an approach
where a wire is installed at the same time the cable isfirst installed. In this way, we can pass the CCH
through without fail and eliminate the later wiring
process.

The long hanger method is highly versatile because
the tools it requires—namely, ropes, a winch, and soon—are in general easily available. In addition, we
confirmed the high reliability of the components usedin this method, which is important since they are
exposed to extremely windy environments with large
temperature fluctuations. This method is scheduled to
be introduced in 2014 by NTT EAST and NTT
WEST. We will assist each company with its introduction.

Katsuhisa Kawaguchi

Kunihiro Shimokubo

Ryosuke Yasui

Kazutoshi Takamizawa

Research Engineer, NTT Access Network Service Systems Laboratories.
He received his B.E. and M.E. in informationand electronic engineering from Tokyo Instituteof Technology in 2007 and 2009, respectively.
He joined NTT in 2009 and moved to his current
position in 2013. Since then, he has been engaged
in the development of the optical access network.

Research Engineer, NTT Access Network Service Systems Laboratories.
He received his B.E. and M.E. in informationand electronic engineering from Hosei University, Tokyo, in 2008 and 2010, respectively. He
joined NTT in 2010 and moved to his current
position in 2012, where he has been engaged indevelopmental research on communication
facilities with high resilience to disasters.

Senior Research Engineer, Supervisor, NTT
Access Network Service Systems Laboratories.
He received his M.E. in electronic engineeringfrom Shinshu University, Nagano, in 1987. He
joined NTT in 1986 and moved to his current
position in 2006. He has been working on developmental research focusing on optical accessnetwork systems.

Ryoichi Kaneko

Yuji Aoyagi

Senior Research Engineer, Second Promotion
Project, NTT Access Network Service Systems
Laboratories.
He received his B.E. in civil engineering fromTohoku-Gakuin University, Miyagi, in 1991. He
joined NTT in 1991 and moved to NTT AccessNetwork Service Systems Laboratories in 2010,
where he conducted developmental research on
optical closure technology. He is now with NTT
EAST.



Senior Research Engineer, Second Promotion
Project, NTT Access Network Service Systems
Laboratories.
He received the A.A in civil engineering from
Kisarazu National College of Technology, Chiba,
in 1988. He joined NTT in 1988 and moved to hiscurrent position in 2010. Since then, he has been
conducting developmental research on communication facilities with high disaster resilience.

Senior Research Engineer, Supervisor, NTT
Access Network Service Systems Laboratories.
He received his B.E. in management engineering from Hosei University, Tokyo, in 1992. He
joined NTT in 1992 and moved to his current
position in 2011. Since then, he has been engaged
in developmental research on optical access network systems.

NTT Technical Review

Global Standardization Activities

IEC Standardization Trends Related
to Energy Infrastructure
Keiichi Hirose
Abstract

The globalization of corporate activities and the expanding markets of emerging economies in recent
years has made international standardization more important than ever. This article describes the standardization activities of the International Electrotechnical Commission concerning direct current power
supply systems as part of international standardization efforts in the field of energy, which has been thefocus of attention in recent years. The main trends in the field of smart grid communities are also introduced.
Keywords: IEC, energy infrastructure, DC power

1. Introduction
The energy shortages caused by the major earthquake disaster that occurred in eastern Japan in
March of 2011 and the need to avert global warming
and other environmental issues have led the NTT
Group to focus more attention on the field of energy,
in addition to the field of information and communication technology (ICT) that has been our traditional
focus. NTT Facilities has been the most actively
engaged in international standardization activities
related to energy in combination with their on-goingwork in technological development, various kinds offield testing, and commercialization studies. This
article introduces the main trends in international
standardization in the field of energy based on theactivities of the International Electrotechnical Commission (IEC) concerning the direct current (DC)power supply that the NTT Group has been recommending [1].
2. Background on the need for international
standardization [2]The importance of international standardization
became clear with the introduction of the 1995 WTO/TBT (World Trade Organization/Technical Barriers
to Trade) Agreement and the 1996 WTO GovernmentProcurement Agreement, which oblige nations to useinternational standards as the basis for procurement
standards. The advanced nations of Europe and North
America have placed importance on conducting vigorous international standardization activities tostrengthen their international competitiveness. Many
countries have also been actively trying to use international standardization as a strategic tool with aview to cultivating emerging markets. Japan, too, hasplaced importance on ensuring that international
standards are set as a component of a long-term strategy. In Japan’s revitalization strategy, too, there is aneed to take the lead in international standards infields where Japan has strength, including smart grids
and energy-efficient infrastructure.
3. IEC and its organizational structure [3]IEC is an international organization that sets standards for electrical and electronic technology; it wasestablished in 1906 and comprises member National
Committees that represent individual countries. Japanis represented by the Japanese Industrial Standards
Committee (JISC), which serves as an umbrella for
about 300 associations and scientific societies within
Japan that are engaged in drafting and studying international standards for various specialized fields.
About 7000 IEC standards have been set, and expansion
NTT Technical Review

Global Standardization Activities

COUNCIL (C)(Full Member National Committees)
COUNCIL BOARD (CB)EXECUTIVE COMMITTEE (EXCO)(IEC Officers)

SMB: Standardization
Management Board

CO: Central Office

MSB:
Market Strategy Board

SG: Strategic Groups
SG 4: LVDC distribution systems
up to 1500V DC
SG 6: Electrotechnology for mobility
SG 7: Electrotechnical applicationsof robot technologies

SEG: Systems Evaluation GroupSEG 1: Smart Cities
SEG 2: Smart Grids
SEG 3: Ambient Assisted Living

CAB: Conformity
Assessment Board

TC: TechnicalCommittees

TAC: Technical Advisory
Committees

SC:
Subcommittees
WG: Working Groups
MT: Maintenance Teams
PT: Project Teams
LVDC: low-voltage direct current

Fig. 1. Organization of the IEC.

of standards for electric vehicles, storage batteries,and smart grids, as well as for semiconductor devices,
home electronics, and other fields that are deeply
linked to energy infrastructure and equipment is
expected in the future.
The organizational structure of the IEC is shown in
Fig. 1. Within the IEC, there are over 100 TechnicalCommittees (TCs) and Subcommittees (SCs) thatcover all sub-fields of technology.
The IEC also includes Strategic Groups (SGs) thatare set up for limited periods of time to put together
proposals on the direction, issues, and recommendations concerning international standards. It has also
been recognized that standardization based on entire
systems is necessary, and therefore, the IEC hasdecided to set up Systems Committees (SyCs) for
establishing standards for systems that span multiple
TCs/SCs rather than simply the conventional TCs/
SCs that deal only with individual products.
The Systems Evaluation Groups (SEGs) are set up
prior to setting up SyCs. They conduct feasibility
studies to investigate the future potential for creatinginternational standards in particular fields. The resultsof these studies by SEGs serve as the basis for the
future establishment of SyCs.
Vol. 12 No. 10 Oct. 2014

4. Activities concerning DC power sources
The NTT Group began seriously studying highvoltage DC power supply systems in 2000. With theacceleration of commercial introduction within the
NTT Group in 2014, we have made progress in longterm technological development. Those activities are
now expanding in various countries around the world
as well as in Japan (Fig. 2), and there is a need forinternational standards for worldwide compatibility.
Below, we introduce the standardization activities
concerning DC power supplies within the IEC.
4.1 SG 4 activities
The DC power supply systems that have been
attracting attention in recent years have applications
in many fields other than ICT, and development asenergy systems for commercial buildings, future residential buildings, distributed power systems, andcharging of electric vehicle batteries is expected.
Building on such work, the Swedish National Committee (SENC) proposed that the IEC set up an SG to
study the standardization of DC distribution systems
up to 1500 V, and the approved SG 4 (LVDC (lowvoltage DC) distribution systems up to 1500 V DC inGlobal Standardization Activities

USA
SAP
380 VDCUSAIntel Corp.
380 VDC

USA
Syracuse Univ.
380VDCUSA
NEXTEK
380 VDCUSA
Stanford Univ.
USA
380 VDC
I/O
380 VDC
USA
USA
Duke Energy
UCSD
380 VDC
380 VDC

Norway350/380 VDC

USASteel ORCA
380 VDCFranceTelecom
380 VDC

Sweden350/380 VDC

China Telecom
240/380 VDC
China Mobile
380 VDC

Switzerland
ABB
Taiwan380 VDC India
380 VDC
IBM
380
Telecom
VDC Singapore
North America
IBM
380 VDC
380 VDC

KOREA
300/380
VDC

Japan
NTT Group
380 VDCNew Zealand
Telecom NZ
220 VDCUCSD: University of California, San Diego
VDC: volts direct current

Fig. 2. Introduction and testing of high-voltage DC power systems.

relation to energy efﬁciency) started activities in2009, which include considering the IEC standards
required for DC power supplies, creating a road map,and analyzing market trends.
4.2 TC and SC activity
In addition to SG 4, various other activities for
actual standardization have begun within the IEC.
Examples showing the scope and present situation ofinternational standardization studies related to DC
distribution as of May 2014 are shown in Fig. 3.
Because of the need for standards concerning uninterruptable power systems, rectifiers, and power converters, SC 22E and SC 22H respectively began
activities in 2013 and 2014. If those activities resultin international standards, we can expect future promotion of the universal use of DC power supplies andexpansion of the practical range and markets for themby JISC as well as by the IEC.
SC 23E is working on DC breakers for wiring andshort-circuit breakers. Outside the field of ICT, theintroduction of mega-solar facilities and photovoltaic(PV) panels for ordinary homes and buildings is
expanding rapidly. Because PV panels output direct
current, their characteristics when a short circuit
occurs differ from those of alternating current (AC)power sources. For that reason, specifications areneeded that are optimized for DC and are different
from the specifications for circuit breakers for AC orfor both AC and DC. An expected result of the SC
23E activities is the issuing of circuit breaker specifi

cations that further improve the safety of DC powersources.
TC 23/WG 8 activities for DC socket and plug standardization began in 2009. These efforts include the
400 volt DC (VDC) socket and plug specifications
developed by both NTT Facilities and Fujitsu Components, which served as the basis for draft international standards. Currently, the AC systems being
used in various countries and areas lack uniformity
and vary in frequency, voltage, and socket and plug
shape. DC power sources are expected to be introduced in greater numbers in the future, and thus,international standardization to ensure uniformity ofshape and regulation will benefit many of the involved
parties.
Furthermore, grounding and protective systems forregulating safety and preventing electric shocks, aswell as equipment and instrumentation, are importantfor DC systems just as they are for conventional AC
systems. In the IEC, TC 64 is charged with setting
and managing regulations for electrical installations
and protection against electric shocks. In TC 64, too,
discussions on DC power sources, including grounding and protective systems, are in progress.
With the recognition that the scope of future studies
includes DC power meters, load equipment switches,charging systems for electric vehicles, DC microgrids(small power grid systems capable of functioning
autonomously), and DC power distribution in residential or commercial buildings, regions, etc., we
expect specific standardization discussions in those
NTT Technical Review

Global Standardization Activities

SC 22E
Stabilized power supply, DC/DC, and AC/DC power converters
SC 22H
DC-UPS (DC uninterruptible power supply)

SC 37A
Low-voltage surge protective devices
SC 23EDC protective equipment

DC source(PV, FC, etc.)

Automatic
Utility gridtransfer switch

AC-DC(Rectifier)G

M

Protection
device(s)

Load

SPD

Emergency backup
generator-set

Storagebattery

TC 23/WG 8
DC socket-plug

SC 23J
Equipment switch

TC 13: DC power meter
TC 64: safety, protection, and construction
Scope of IEC (electricity facilities, equipment, and materials)

Fig. 3. Current scope of IEC studies on DC power supplies.

areas to proceed in addition to the activities depicted
in Fig. 3.
5. Efforts in the field of (smart) energy
infrastructure
IEC work on international standardization of smart
grids is accelerating. IEC communities involved withsmart grids are listed in Fig. 4. Japan, too, has taken
an interest in this field, and various activities areunderway. IEC activities concerning smart grids andsmart cities are described below.
5.1 TC 120 Electrical Energy Storage Systems
In October 2012, the IEC approved the formation ofa new Technical Committee for storage batteries andother EES (electrical energy storage) systems (TC120) that connect to smart grids. This new committee
was proposed by Japan, and Japan is serving as thesecretary, while Germany is the convener. The resultsof experiments being conducted in various countries
that are relevant to businesses involved in constructing environmentally friendly smart communities are
expected to serve as the basis for future international
standards.
5.2 SEG 1 Smart Cities
Japan, Germany, and China have made joint proposals involving smart cities, and those proposals
have been approved. SEG 1 Smart Cities has been set
Vol. 12 No. 10 Oct. 2014

up, and studies on the feasibility of international standards have begun within the IEC. The role of infrastructure in city functions is important in terms ofbusiness continuity planning, and discussions on thetechnical requirements that will become necessary
from the viewpoint of future international standardization are planned.
SEG 1 is planning activities that include compilingdescriptions of the activities within IEC and ISO(International Organization for Standardization),establishing the standardization scope and categories,
evaluating marketability, defining terms, conducting
case studies, creating a standardization road map, andcollecting relevant information.
5.3 SEG 2 Smart Grid (formerly SG 3)
SG 3, which has been discussing smart grids, hasbeen reorganized as SEG 2 in order to begin establishing international standards. As mentioned in section 3, the reorganization is part of the progression
from SG to SEG to SyC. Exchanges of opinions andvigorous discussions in this field are expected, withthe goal of establishing future IEC standards.
In SEG 2, further discussions in the field of smart
grids, including smart energy, are anticipated in orderto prepare for the future transition to an SyC. In addition, the SEG is expected to provide coordination andguidance on system level standards in the area ofsmart energy, including heating/cooling and the useof gas and electricity.
Global Standardization Activities

International standardization activities concerning smart cities have been intensifying.
For example, new TCs related to renewable energy and the smart grid have been established.
Year establishedIEC community

Secretary

Convener (Chair)2007

TC 114: Marine energy

UK

USA

2008

TC 115: High voltage direct current (HVDC)
transmission for DC voltages above 100 kV

China

Germany

2011

TC 117: Solar thermal electric plants

Spain

Israel2012

PC 118: Smart grid user interface

China

France2012

TC 120: Electrical energy storage (EES) Systems

Japan

Germany

2013
2013

SEG 1: Smart cities
SEG 2: Smart gridCentral OfficeCentral Office

Japan
FranceSmart energy has become the most important field in international standardization efforts.
Source: Recreated by the author based on the document “Strengthening International Standardization
Policy for 2014,” Ministry of Economy, Trade, and Industry of Japan, October 2013 (in Japanese).
PC: Project Committee

Fig. 4. Efforts to strengthen (smart) energy infrastructure.

Cooperation with SEG 1, future SEGs, related IEC
internal organizations, and with ISO and ITU (International Telecommunication Union) is also anticipated.
6. Future developments
In the IEC, international standardization concerning energy infrastructure in relation to smart grids is
actively underway, and the Japanese government isalso placing importance on such activities. The IEC isalso working on standardization of the DC power
supply as a smart grid subsystem, and standardization
work is proceeding in coordination with the activitiesof ITU-T (ITU-Telecommunication Standardization
Sector) and ETSI (European Telecommunications
Standards Institute), etc.
Increasing the efficiency and convenience of energy
systems will be beneficial to many parties. The cooperation of international standards organizations, sci-

entific associations, and the members of the NTT
Group is more important than ever before, and it isnecessary to continue to promote international standardization activities in this field well into the
future.
References
[1]

[2]

[3]

T. Tanaka, K. Asakura, and T. Babasaki, “Trends in the International
Standardization of HVDC Power Feeds,” NTT Technical Review, Vol.
11, No. 3, 2013.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr2013
03gls.html
Strengthening International Standardization Policy for 2014, Ministryof Economy, Trade and Industry of Japan, October 2013 (in Japanese).
http://www.meti.go.jp/press/2013/10/20131007005/201310070054.pdf
IEC Business Overview –2014 Edition– (one company) Japan Standards Association, IEC Activities Promotion Committee, May 1, 2014
(in Japanese).
http://www.iecapc.jp/documents/gaiyou/2014_gaiyou_ippan.pdf

NTT Technical Review

Global Standardization Activities

Dr. Keiichi Hirose

Executive Manager, Technical Division, Energy Business Headquarters, NTT Facilities.
He received his B.Eng. and M.Eng. in electrical engineering from Yamagata and Niigata Universities, respectively, in 1990 and 1992, and his
Ph.D. in electrical engineering and computer science from Nagoya University in 2011. He joined
NTT in 1992. He has a background as a researchengineer and has more than 18 years of experience in the design, development, and operation ofreliable power systems for telecom and datacenters. He is currently working with 380-VDC
systems for NTT and its customers, as well as
researching aspects of smart grids.
He is a member of The Institute of Electricaland Electronics Engineers (IEEE), the Instituteof Electrical Engineers of Japan (IEEJ), the Institute of Electrical Installation Engineers of Japan(IEIEJ), and the Institute of Electronics, Information and Communication Engineers (IEICE). He
is also very active in many standards bodies inareas associated with power systems. He is amember of the IEC SMB (Strategic Management
Board) SG 4, a member of the Green Grid Power
sub-working group, chair of the IEC SC 22E
Japanese NC, and a recent past secretary of the
IEEJ Investigating R&D Committee into DC
power distribution.
He was awarded the IEEE PELS (Power Electronics Society) INTELEC 3rd best paper award
in 2009, the outstanding paper prize from IEEJ in2010, the best paper award of IEIEJ in 2013, andthe Scientific Award of the Japan Society ofEnergy and Resources in 2013. He was also
awarded the Hoshino Award of IEIEJ in 2014.

Vol. 12 No. 10 Oct. 2014



Global Activities of NTT GroupNTT Com Security
Tetsuo Someya, Chief Business Development Officer andChief Governance Officer
Abstract

NTT Com Security, the successor to security specialists
Integralis (Germany) and Secode (Sweden), launched its
comprehensive risk management service called WideAngle
in June 2013. This article introduces the work of NTT Com
Security while describing the information security environment surrounding today’s corporations.

1. Introduction
NTT Com Security provides information security
services. Its main office is located in Germany, andthe company is listed on the German stock exchange.
Its parent companies are Integralis, a German company founded in 1988, and Secode, a Swedish company founded in 1986, both of which were acquiredby NTT Communications—the former in 2009 andthe latter in 2010. The two companies merged in 2011
and changed their name to NTT Com Security in
October 2013. NTT Com Security has just started
afresh as a company at the core of the security services business in the NTT Communications Group(Fig. 1).
NTT Com Security has been a leading company inthe security field for over 25 years since its initialfounding. It has been expanding its business with afocus on Europe and the United States and is now
developing its business in the Asia Pacific region(Fig. 2).
NTT Com Security employs about 870 people
worldwide, of which more than 500 are skilled personnel such as consultants specializing in security or
security analysts prominent in the field. It consists ofa main office and branch offices in 15 countries
around the world. More than 200 of these employees
are working as security engineers or risk analysts atGlobal Risk Operations Centers in seven countries.
Their job is to perform security monitoring for NTT
Com Security customers 24 hours a day, 365 days ayear and to keep track of global security trends.
2. Current state of security market
A common theme today is that security is something that cannot be ignored in an environment ofadvanced communications technologies, BYOD
(Bring Your Own Device) policies, and big dataapplications. Hacking of information related to financial, government, and military institutions, as well ashacking of confidential information to conduct electronic commercial transactions (e-commerce), andhacking simply for financial gain, occur on a daily
basis in an increasingly organized and sophisticatedmanner. Another side of technological progress is thenumerous examples of commonly used services thatare being exposed to security threats, which results ina less reliable social infrastructure. Specifically, it has
become clear that serious vulnerabilities such as
Heartbleed, which was uncovered in the OpenSSL
cryptographic library, and those in Apache Struts 2, a
widely used open-source framework for creating web
applications, have exposed many transactions on the
web to the risk of information leaks, resulting, forexample, in the temporary closure of a website used
NTT Technical Review

Global Activities of NTT Group

2000
Verio (Tier 1 operator)acquired2008
SAMURAI (anti-DDoS product) launched

2003

2009

Integralis
foundedTwo companies
integrated

Acquired

1988

2011

• Business description: Deployment and operation of full-layer security services• Achievements: Extensive track record in diverse industries mainly in Europe
and the United States

1986

Name changed:
NTT Communications
NTT Com Security

Development
collaboration

2012

2010

Tokyo SOC established Integralis acquired Secode acquired

2013

Provider of total
ICT
outsourcing
services

Security operation
platform integrated

New brand launched

NTT Secure
Platform
Laboratories

AcquiredSecode founded • Business description: Consulting and provision of managed security services• Achievements: Extensive track record in the public sector and financial industry
DDoS: distributed denial of service
ICT: information and communication technology
SOC: Security Operations Center

Fig. 1. History of NTT Com Security.

USA
Aliso Viejo (Ashburn)

Netherlands Sweden
UK
Finland(London)
NorwayGermany
Waltham
Switzerland
Bloomfield &Austria
New York
FranceJapan
Hong Kong
Malaysia
Singapore

SydneyBases installing a SIEM (security information and event management) engine (2013)
Bases deploying security consultants
Bases having a Global Risk Operations Center

Fig. 2. Global expansion of NTT Com Security business.

for filing income tax returns.
In March 2014, the NTT Group published the
Global Threat Intelligence Report (GTIR) based onrecent attacks and a massive security-monitoring log(Fig. 3). This report was prepared and released by
NTT Innovation Institute, Inc. (NTT I3) in cooperation with NTT Group security companies (Solutionary, NTT Com Security, Dimension Data, and NTT
DATA) and NTT laboratories. Through an analysis ofVol. 12 No. 10 Oct. 2014

more than 3 billion recent security attacks and security log data covering several trillion cases obtained
through monitoring at 16 Security Operations Centers (SOCs) worldwide, this report provides useful
information on what information assets attackers areaiming for and what methods they are using, and on
how an organization can protect itself.
According to this report, 34% of all known attacks
are related to client botnet activity and 15% toGlobal Activities of NTT Groupanomalous behavior, i.e., unnatural or abnormal communications (Fig. 4). This means that, for about halfof all attacks, users’ internal terminals or users themselves are either knowingly or unknowingly complicit in the attacks. An enterprise must take countermeasures against the risk of becoming a victim and of
simultaneously becoming a perpetrator. Furthermore,it goes without saying that individual employees can
expose the enterprise they work for to major lawsuits
or compensation claims by causing internal or external damage.
There are cases in which a system manager’s terminal within a corporate network becomes infected withmalware that then spreads throughout the network
unbeknown to that manager. It is clear from survey
materials that most such cases result in large monetary losses. The GTIR states that the monetary dam-

age per incident of this type is estimated to be about
US$110,000.
Malware is continuously evolving to evade systemmanagers and diverse security measures. The same
survey revealed that 54% of new malware gatheredby honeypots set up by the NTT Group for research
purposes could not be detected by existing anti-virus
software and similarly that 71% of malware gathered
in a sandbox environment could not be detected by up
to 40 existing virus countermeasures.
New types of attacks that are mounted from either
inside or outside a company directed at information
assets appear daily, so it is impossible to protect oneself by simply introducing security devices and security software. It is important to have a security maintenance mechanism that can defend against both
external and internal attacks and deal with new attack
techniques on a continuous basis. Furthermore, whenselecting a security service or vendor, it is important
to consider whether the service or company can provide a mechanism not just for end-point security but
also for detecting malware throughout the corporate
network and cloud and whether that mechanism canuncover vulnerabilities and understand the nature of
attacks. It must also be considered whether a security
service or vendor can provide resources for keeping
up with the latest security trends.
3. New service brand—WideAngle
The market focused on by NTT Com Security ismainly corporate information security management
consisting of three business domains: (1) professional
services, (2) sales and deployment of security devices, and (3) managed security services (MSS).

Fig. 3. Global Threat Intelligence Report.

10%
4%

Attacks by type

5%

34%

6%
8%
8%
10%

15%

Client botnet activity

Anomalous behavior

Network manipulation

Service specific attack

Web application attack

Application specific attack

DoS/DDoS

Reconnaissance

Other

Fig. 4. Breakdown of security attacks.



NTT Technical Review

Global Activities of NTT GroupAs of June 2014
Global Risk Operations Center (GROC)
Level 3

Risk management for individual customers
Advanced security analysis

Level 2

Security event management
Device change management

Level 1Primary customer support desk

SwedenJapan(in preparation)

Malaysia

Japan

Japan

USA

UK

SwedenNorway Malaysia

SingaporeFig. 5. Security monitoring operations system.

NTT Com Security began its security business in1986 at overseas locations and in 2003 at the Tokyo
SOC as a base within Japan. The company continues
in its role of monitoring corporate network security.
At present, a total of about 200 employees work at
customer support desks at seven bases around theworld (Fig. 5). This support includes security event
management and device change management inJapan and Malaysia and advanced security analysis
and risk management for individual customers inJapan and Sweden.
The company began providing Biz Managed Security Services as MSS for the Japan market in June
2012. In 2013, it upgraded its service platform undera new service brand called WideAngle to provide
information security services for customer systems ina seamless manner across international and domestic
cloud services and on-premise corporate systems. In
this way, NTT Com Security can provide both corporate information security platforms and operations
services as a trusted advisor. In MSS, the company
provides total security outsourcing services on various layers to uncover vulnerabilities and deal withnew types of threats such as targeted attacks that aim
to exploit user psychology. NTT Com Security hascome to manage over 11,000 security devices inabout 3000 companies (as of May 2014).
At NTT Com Security, security consulting is thepillar of professional services, and the company has arecord of providing consulting in more than 8000
cases over the last 25 years. Based on this extensive
experience accumulated since its initial founding, thecompany is now providing a new consulting program
called Global Enterprise Methodology (GEM). This
program has established a globally uniform evaluaVol. 12 No. 10 Oct. 2014tion technique and systematized the company’s
know-how. It quantifies the security level of a clientcompany, determines the optimal security level thatthe company should have given the client’s businessand industry and the requirements to attain that level,
and makes proposals for overall improvement.
In information security, the defending side must be
optimized in the face of ever-changing attacks. The
attacker, meanwhile, may not necessarily be aiming
to exploit information or engage in fraud throughonly one attack. A more likely scenario is that theattacker shifts to full execution only after making
some preparations and performing a preliminary
investigation of the target site. Detecting such signsof prior activity can only be accomplished throughmanaged services that perform continuous security
monitoring. An effective defense against attacks cannot be achieved by only implementing a countermeasure once, by only deploying security devices, or by
only using a detection system engine.
It is extremely difficult for a company to thoroughly defend itself from threats by implementing suchmeasures on its own or by keeping an eye on numerous devices.
The new WideAngle service platform provided by
NTT Com Security features a newly developed security information and event management (SIEM)
engine in addition to monitoring and analysis byexpert risk analysts. It also provides the customer
with a portal for integrated viewing of the state ofvarious security devices.
In providing total managed services for client companies and public institutions, NTT Com Security is
working with NTT laboratories, NTT DATA, andSolutionary to assemble knowledge and know-howGlobal Activities of NTT Grouprelated to NTT Group security technology. It
researches how to identify threats that are continuously changing, how to protect information assets,
and how to make the use of such assets safe. It thenpromptly incorporates the results of this research into
actual services.
4. NTT Group’s approach to security solutions
The NTT Group added Solutionary in North America as a new security service provider in 2013, andtogether with NTT Com Security (born out of Integralis and Secode), Earthwave, a subsidiary of
Dimension Data, and NTT I3, the Group’s researchand development center in North America, it has been
making its presence felt in the global security market
and receiving high marks from client companies.
The NTT Group was evaluated as a “Challenger” inGartner’s 2014 Magic Quadrant for Global MSSPs*,
which positions MSS providers in the global market,
and was positioned in the same quadrant as the vendor with the highest “ability to execute.”
At NTT Com Security, we believe that the reason
for this high evaluation is due to our provision ofhigh-quality MSS services, our development of awide variety of novel technologies in support of thoseservices, our globally uniform system of providing
services and operating SOCs, and our sophisticatedinformation exchange network within the NTT Groupfor keeping up with the latest security trends andthreats.
Going forward, we aim to create a synergetic effectthrough even further interaction and collaboration
among the NTT Group companies while providing
solutions in diverse domains such as network services, datacenters, and cloud services. Our desire is toprovide cutting-edge security solutions at the forefront of the industry by working together as a unified
group.
*

Gartner, “Magic Quadrant for Global MSSPs,” Kelly M. Kavanagh, 26 February 2014.
Gartner does not endorse any vendor, product, or service depicted
in its research publications, and does not advise technology users
to select only those vendors with the highest ratings. Gartner research publications consist of the opinions of Gartner’s researchorganization and should not be construed as statements of fact.
Gartner disclaims all warranties, expressed or implied, with respect to this research, including any warranties of merchantability
or fitness for a particular purpose.

Tetsuo Someya

Chief Business Development Officer and Chief Governance Officer, NTT Com
Security.
He has an MBA from Yale School of Management and a BA in law from Waseda
University in Japan. He was appointed Chief Business Development Officer andChief Governance Officer in January 2013. As Chief Business Development Officer,
he is responsible for developing the relationship between NTT Com Security and
NTT Communications and its affiliates. In his role as Chief Governance Officer, helooks after key group governance functions, including those concerning legal, procurement, information security, internal auditing, and group IT issues.
Prior to this, he worked in a variety of roles across NTT Communications for over
20 years, including service planning and development, public relations, global business strategy, and global human resources management, and spent time at NTT
Europe leading the Düsseldorf office. He also played an important role in overseas
investment management at NTT (holding company) from 2001 to 2005.

NTT Technical Review

Practical Field Information about
Telecommunication Technologies

Signal Generator for Noise Search
Tester to Improve Noise-measurement
and Noise-identification Skills
Abstract

This article introduces recent equipment and methods developed for use in troubleshooting noise
faults. This is the twenty-fifth of a bimonthly series on the theme of practical field information on telecommunication technologies. This month’s contribution is from the EMC Engineering Group, Technical
Assistance and Support Center, Maintenance and Service Operations Department, Network Business
Headquarters, NTT EAST.
Keywords: noise faults, noise measurement, maintenance skills

1. Introduction
The objective in the development of electric andelectronic devices in recent years has been to makethem smaller and more energy efficient. Meeting thisobjective, however, results in heavy use of the switching circuit in the power-supply section of such devices. This means that noise caused by the operation of
the switching circuit or by problems in capacitors,
semiconductors, or other circuit devices may be conducted to the outside via power or communicationlines or radiated through space. Noise of this type cangenerate audible noise in telephone calls in the user’sbuilding or home or can bring down a communication
link in ADSL/VDSL (asymmetric digital subscriber
line/very-high-speed DSL) lines as a result of a communication coding error or other fault. In this situation, some type of countermeasure must be takensuch as installing appropriate noise filters in the
power or communication lines connected to the telephone equipment or by removing the noise sources
themselves. In any case, measuring the frequency andlevels of the disturbance voltage (or current) superimposed on power or communication lines is necessary
for the troubleshooting process. It is for this reason
that we developed a noise search tester (NST) thatcan be easily used by on-site maintenance operators.
We have also marketed a successor to this product(NST II) that features enhanced sensitivity to periodic burst noise. More than 1000 units of the NST
series have so far been introduced into the market.
In order to look for the noise source, it is necessary
to conduct the noise measurement in complex facility
environments that include not only telecommunication equipment but also various types of power-supply devices. It is therefore important that maintenance
operators improve their skills in conducting measurements with NST II. In this article, we present a casestudy of a malfunction of telecommunication equipment and describe our development of a signal generator designed for simulating actual noise waveforms.
2. Case study
2.1 Noise sources
Noise sources that can lead to faults can exist in awide variety of electric and electronic devices in
addition to communications equipment. Identifying anoise source can therefore be quite difficult. Types ofnoise sources found in a two-year on-site survey are
shown in Fig. 1. It can be seen from the figure thatelectric and electronic devices that use alternating
current (AC) mains power, for example, a Kotatsu
and AV (audio-visual) equipment, can be a source ofnoise. However, because a variety of electric and
NTT Technical Review

Practical Field Information about Telecommunication Technologies

11%

33%

7%
7%
3%

6%

6%

3%

3%

3% 3%

Kotatsu (Japanese electric heated table)

AV equipment

3% 3%

3%

3%
3%

Fluorescent lighting

Fax machine

Analog cordless phones

Water pumps

ISM-equipment interference

Boosters

AM radio signals

ADSL modems

Leased-line terminals

AC6600V ground relays

Call signals

UPS (in telecommunication center)

IP equipment (in telecommunication center)

Unidentified noise source
AM: amplitude modulation
IP: Internet protocol
ISM: industrial, scientific, and medical
UPS: uninterruptible power supply

Fig. 1. Types of noise sources.

electronic devices are usually connected to the same
AC mains line, it has been extremely difficult to identify where the noise source is actually located. The
following section presents a case study of a noiseinduced fault describing how the noise source was
identified and what countermeasure was taken.
2.2 Case study of noise-induced fault
2.2.1 Fault overview
A customer using business phones reported a fault
in which an audible noise would sometimes be heard
during telephone calls. The facility setup on the customer’s premises is shown in Fig. 2. Although amaintenance operator spoke with the customer anumber of times to determine the cause of the fault,
the fault remained, and it was eventually decided toperform on-site noise measurements and consider
countermeasures.
2.2.2 Noise measurement
The maintenance operator performed noise measurements at several locations (points A–C in Fig. 2)
and measured, in particular, disturbance current using
an oscilloscope and current probe. The noise waveforms at the intercom communication line (point A)
are shown in Fig. 3.
(1)	The noise waveforms depicted typical periodic burst noise that was generated every halfcycle (10 ms) with respect to the frequency of
AC mains power (50 Hz). An on-site inspecVol. 12 No. 10 Oct. 2014tion revealed that this noise was generated
when arc welding work was being done. It wasalso found that disturbance current values
were highest on the intercom communicationline (point A in Fig. 2) situated adjacent to thearc welding workplace.
(2)	The results of performing FFT (fast Fouriertransform) analysis on the measurement
results of Fig. 3 and determining its power
spectrum are shown in Fig. 4. In comparing
the state in which noise was present with thestate in which noise was absent, it was foundthat the noise level was high across a wide
frequency range of 800 kHz–10 MHz.
These measurement results indicate that the fault
occurred during the arc welding operation. In addition, the results of more detailed measurements
revealed that this noise was transmitted to the business phone from the intercom communication line
near the arc welding workplace, and it then flowed
into other communication lines and AC mains lines.
2.2.3 Noise countermeasure
The following actions were taken as a countermeasure to this noise:(1)	Unused multi-pair in-customer-premises
cables near the arc welding workplace were
removed.
(2)	Noise filters were installed on communicationlines on the business-phone side and on thePractical Field Information about Telecommunication Technologies

Multifunction
telephone

Main equipment for business phone system

MDF
Extensionphone unit
Point B
Intercomunit

Intercom

Point A

Communication line conduit
Adjacent to conduit
High-voltage
power-receiving facilities

Power
supply unit

Power
(AC100V)

Power(AC200V)

Point CArc welder
Arc welding
workplace

Communication
line
Groundingconductor

GroundUnusedcommunication line
Multi-pair in-house
cable

AC100/200V
power-supply line

MDF: main distribution frameFig. 2. Facility setup on customer’s premises.

(mA)
+1000
Intercom0
communicationline(point A in Fig. 2)
−1000

10 ms

(5 ms/div)
820 mAp-p

Burst noise waveforms

Fig. 3. Noise-current waveforms on intercom
communication line.

(dBA)

−20
−40

800 kHz–10 MHz
Noise present

−60
−80
−100
−120
100 k

Noise absent

1M

(Hz)

10 M

100 M

Fig. 4. Power spectrum of intercom communication line.

side of terminals connected to the businessphone side.
(3)	A transformer was installed on the businessphone AC mains line; the ground terminal andthe business-phone FG (frame ground) terminal were connected, and these were connected
in turn to the MDF (main distribution frame)
ground, keeping the connection as short as
possible. The above countermeasure made it
possible to eliminate the audible noise fromthe business-phone side.
Nevertheless, the on-site maintenance operator said
that we had had few encounters with a noise-induced
fault of this type, which meant that they had noopportunities to practice troubleshooting or dealing
with this kind of problem, even employing an easyto-use measurement tool like the NST II. We therefore realized that a tool that could facilitate the acquisition of necessary skills when using NST II had to be
developed.

NTT Technical Review

Practical Field Information about Telecommunication Technologies

3. Signal generator for use with anoise search tester
3.1 Development background
Given the occurrence of audible noise in telephone
calls or of link down in ADSL/VDSL lines, an experienced maintenance operator would be able to measure noise using NST II (Fig. 5) and then identify thesource of the noise and implement appropriate countermeasures with noise filters. An on-site maintenance operator needs noise-measurement skills toappropriately identify the noise source and to selectnoise filters when using NST II. For this reason, we
have been engaged in technology dissemination
activities by creating a noise fault environment using
a signal generator so that maintenance operators canacquire the skills needed for troubleshooting andidentifying noise sources and for selecting appropriate countermeasures. Maintenance operators who
have wanted to improve their noise-measurement
skills on their own have been faced with a number ofproblems, which is reflected by comments received
from them such as “Signal generators are too expensive” and “Creating a noise environment is too difficult.” In the face of these problems, we developed asignal generator for use with a noise search tester thatcan easily and inexpensively create noise environments for training purposes (Fig. 6).
3.2 Functions
This signal generator has been designed to enable
simulated noise to be safely and easily measured
when used in combination with NST II. Two important points in the development of this signal generator
are described below.
(1) Triangular-wave signals
The signal generator can output seven types of triangular-wave signals corresponding to the NST II
frequency range. It was decided to use triangularwave signals since the high harmonic components ofnoise cannot be simulated in the case of sinusoidal
signals. The specific signal frequencies that can be
output are 1 kHz, 15 kHz, 70 kHz, 250 kHz, 1 MHz,
3 MHz, and 20 MHz, which means that the signal
generator can simulate signals that approximate thoseof actual noise waveforms (Fig. 7).
(2)	Signals that simulate burst noise on AC mains
line
The signal generator can output signals that simulate the periodic burst noise (half cycle of the frequency) on an AC mains line. This type of noise has
become the chief cause of noise-related faults in
Vol. 12 No. 10 Oct. 2014

Fig. 5. NST II.

Fig. 6. S ignal generator for use with a noise searchtester.

70 kHz250 kHz
15 kHz1 MHz

Fig. 7. S creen showing noise measurement for 70-kHz
signal.

Practical Field Information about Telecommunication Technologies

Operation
check
Noise
detection
Noise
Signal generator

Distribution
frame

-0

1k

15k

70k 250k 1M

3M

Noise-filter
countermeasure

20M

dBV

- 30
dBV

0 0 :0 0 :0 0

RANGE × 1
MEM.BLOCK

MONI
REC
VIEW

INTVL
10 m i n
s ec

Noise
Noise search tester

Telecommunicationequipment

Fig. 8. Usage scenario.

recent years. When selecting a simulated noise signal,
the user can listen to a whirring sound representing
noise by connecting an earphone to the NST II for
monitoring purposes.
The signal generator described above enables
maintenance operators to improve their noise measurement skills using NST II by making it possible toeasily create a noise environment that is similar to
one with actual noise faults.
3.3 Usage of the signal generator
A typical setup for this signal generator, NST II,
and telecommunication equipment is shown in Fig. 8.
In this figure, the signal generator directly applies
noise to the communication cable, and a maintenance
operator uses NST II to measure that noise. By checking for the frequency of the NST II, the maintenance
operator can apply an appropriate countermeasure.
This signal generator therefore makes it easy to create
an environment in which maintenance operators canpractice searching for the noise source and decide
what countermeasure to take against the noise fault,
which has been difficult to do in the past. We expect
repeated practice with such simulated noise to enable
maintenance operators to solve noise faults on communication cables.



4. Conclusion
Solving noise-induced faults in a system requires
troubleshooting skills in identifying the source of thenoise as well as skills for taking appropriate countermeasures. To meet these requirements, we developed
a signal generator for use with a noise search tester as
an effective means of creating a noise environment at
low cost and to enable maintenance operators toacquire noise measurement skills while using NST II.
Going forward, we plan to continue our research anddevelopment efforts to facilitate speedy solutions tonoise-related problems and provide enhanced support
for safe and secure communication services.
References
[1]

[2]

K. Tominaga, Y. Ogura, and K. Murakawa, “Recent Noise Troubles
for Telecommunication Equipment and Future Work,” Proc. of theSociety Conference of the Institute of Electronics, Information andCommunication Engineers (IEICE), B-4-66, Sapporo, Japan, September 2011 (in Japanese).
K. Murakawa, K. Tominaga, Y. Okugawa, Y. Ogura, and H. Itou,“Recent Malfunctions and Mitigation of Telecommunication Installations,” Proc. of IEICE Technical Committee on Electromagnetic
Compatibility (EMCJ), EMCJ2011-93, pp. 31–36, Tokyo, Japan,
November 2011 (in Japanese).

NTT Technical Review

External Awards
Entropy Best Paper Award 2014, 1 st Prize of Review
Award
Winner: Katherine L. Brown, School of Physics and Astronomy,
University of Leeds; William J. Munro, NTT Basic Research Laboratories; and Vivien M. Kendon, School of Physics and Astronomy,
University of Leeds
Date: April 30, 2014
Organization: Multidisciplinary Digital Publishing Institute (MDPI)
AG, based in Basel, Switzerland

For “Using Quantum Computers for Quantum Simulation”.
In this review we surveyed the theoretical and experimental development of quantum simulation using quantum computers, from thefirst ideas to the intense research efforts currently underway. This was
the first comprehensive review.
Published as: K. L. Brown, W. J. Munro, and V. M. Kendon, “Using
Quantum Computers for Quantum Simulation,” Entropy 2010, Vol.
12, No. 11, pp. 2268–2307.

Papers Published in Technical Journals andConference Proceedings
Network Coding and its Application to Content Centric
Networking
S. Miyake and H. Asaeda
Proc. of WITMSE (Workshop on Information Theoretic Methods
in Science and Engineering) 2013, pp. 55–61, Tokyo, Japan, August
2013.
Content Centric Networking (CCN) is one of the predominant
proposals that have been made for the next generation content distribution platform. In CCN each router in a network is equipped with alarge sized cache memory and becomes a content router that can be
regarded as a temporary content server in the network. This mechanism can reduce the concentration of data traffic going into the original content server.
To enhance the merits of CCN, we propose applying network coding (NWC) to it. Applying NWC in this way makes it possible toimplement distributed data storing of content data and to achieve
multi-path transmission between content routers and an access router(or an end user). CCN with NWC can provide higher throughput forend users and reduce network load.
In addition to proposing the aforementioned application, in thispaper we specify issues needing to be addressed to more successfully
combine CCN with NWC.

A Disaster Resilient Image and Video Transmission
Scheme Based on Movable and Deployable Resource
Units
T. Nakachi, S.Y. Kim, and T. Fujii
Proc. of HTC (Humanitarian Technology Conference) 2013, IEEE
Region 10, Sendai, Japan, August 2013.
In this paper, we propose a disaster resilient image and video transmission scheme based on specially designed “Movable and Deploy-able Resource Units (MDRUs)”. The proposed resilient data transmission scheme offers image and video data appropriately to people
in disaster areas through MDRUs. The image and video data aretransmitted based on the MDRU power supplies and the network
bandwidth between the MDRUs and terminal devices in the disasterarea. Experimental results and demonstrations show the effectivenessof the proposed disaster resilient image and video transmission
scheme.

A Conceptual Foundation of NSCW Transport Design
Using an MMT Standard
T. Nakachi, Y. Tonomura, and T. Fujii
Proc. of ICSPCS (International Conference on Signal Processing
and Communication Systems) 2013, Gold Coast, Australia, December 2013.
This paper introduces the concept of Network Supported Collaborative Work (NSCW) and its transport design based on the emerging
standard of MPEG Media Transport (MMT). Based on extra-highquality 4K video technologies, NSCW is being developed to realize
effective remote collaboration for business workspaces. MMT specifies technologies for the delivery of coded media data for multimedia
services over the concatenation of heterogeneous packet based network segments including bidirectional IP networks and unidirectional digital broadcasting networks. One of the core technologies fordelivery is forward error correction (FEC) codes. Simulation results
using our proposed MMT FEC codes show the effectiveness of the
proposed method.

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

An Overlay Network Construction Technique for Minimizing the Impact of Physical Network Disruption in Cloud
Storage Systems
K. Suto, H. Nishiyama, N. Kato, T. Nakachi, T. Fujii,
and A. Takahara
Proc. of ICNC (International Conference on Computing, Networking and Communications) 2014, pp. 68–72, Honolulu, HI, USA,
February 2014.
Cloud storage exploiting overlay networks is considered to be ascalable and autonomous architecture. While this technology canensure the security of storage service, it requires addressing the“server breakdown” problem, which may arise due to malicious
attacks on servers and mechanical problems with servers. In existing
literature, an overlay network based on bimodal degree distribution
was proposed to achieve high connectivity to combat these two typesof server breakdown. However, it cannot ensure the high connectivity
against physical network disruption that removes numerous nodes
from the overlay network. To deal with this issue, in this paper, we
propose a physical network aware overlay network, in which theneighboring nodes are connected with one another in the overlay.
Moreover, the numerical analysis indicates that the proposed system
considerably outperforms the conventional system in terms of service
availability.

An Iterative Compensation Approach without Linearization of Projector Responses for Multiple-projector System
I. Miyagawa, Y. Sugaya, H. Arai, and M. Morimoto
IEEE Transactions on Image Processing, Vol. 23, No. 6, pp.
2676–2687, June 2014.
We aim to realize a new and simple compensation method thatrobustly handles multiple-projector systems without recourse to thelinearization of projector response functions. We introduce state
equations, which distribute arbitrary brightness among the individual
projectors, and control the state equations according to the feedback
from a camera. By employing the color-mixing matrix with gradientof projector responses, we compensate the controlled brightness
input to each projector. Our method dispenses with cooperation
among multiple projectors as well as time-consuming photometriccalibration. Compared with existing methods, our method is shown
to offer superior compensation performance and a more effective wayof compensating multiple-projector systems.

Vol. 12 No. 10 Oct. 2014

Rapid Switching in High-Q Mechanical Resonators
H. Okamoto, I. Mahboob, K. Onomitsu, and H. Yamaguchi
Applied Physics Letters, Vol. 105, 083114, August 2014.
Sharp resonance spectra of high-Q micromechanical resonators
are advantageous in their applications, such as highly precise sensors
and narrow band-pass filters. However, the high-Q characteristics
hinder quick repetitive operations of mechanical resonators becauseof their long ring-down time due to their slow energy relaxation.
Here, we demonstrate a scheme to solve this trade-off problem inpaired GaAs micromechanical resonators by using parametricallyinduced intermode coupling. The strong intermode coupling inducedby the piezoelectric modulation of tension allows on-demand energy
transfer between closely spaced mechanical modes of the resonatorvia coherent control of the coupling. This enables rapid switching of
the vibration amplitude within the ring-down time, leading to quick
repetitive operations in high-Q mechanical resonators.

On the Computational Power of Constant-depth Exact
Quantum Circuits
Y. Takahashi
Proc. of Satellite Workshop of AQUIS (Asian Quantum Information Science Conference) 2014, Tokyo, Japan, August 2014.
We show that there exists a constant-depth polynomial-size quantum circuit for the quantum OR operation. We also show that, undera plausible assumption, there exists a classically hard problem that issolvable by a constant-depth quantum circuit with gates for the quantum Fourier transform.

Hardness of Classically Simulating Quantum Circuits with
Unbounded Toffoli and Fan-out Gates
Y. Takahashi, T. Yamazaki, and K. Tanaka
Quantum Information and Computation, Vol. 14, No. 13&14, pp.
1149–1164, October 2014.
We show that there exists a constant-depth quantum circuit with
only one unbounded Toffoli gate that is not weakly simulatable,
unless BQP ⊆ PostBPP AM. Then, we show that there exists a
constant-depth quantum circuit with only two unbounded fan-out
gates that is not strongly simulatable, unless P = PP.
⊂

Water Electrolysis and Energy Harvesting with 0D Ionsensitive Field-effect Transistors
N. Clément, K. Nishiguchi, J. F. Dufrêche, D. Guérin, A. Fujiwara,
and D. VuillaumeProc. of International Symposium on Energy Challenges &Mechanics, Aberdeen, Scotland, UK, July 2014.
Water electrolysis is one of the most “green” approaches for producing hydrogen (H2) as a fuel source. As a key issue in the operationof the International Space Station and the mission to Mars, waterelectrolysis is utilized as a regenerative life support system and is partof the energy conversion system. The behavior of gas bubbles inwater electrolysis is a typical interfacial phenomenon. Many experiments including optical, acoustic, and other approaches (e.g., electrical impedance), have been performed to determine the bubble size
distribution in samples of water. Here, we show that nanotransistors,
which are so small that they can be considered as 0D, can be used totransform energy lost during bubble emission into electrical pulses.
This system does not require light, is sensitive to a single bubble, andhas no intrinsic limitation in bubble size.

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