Special Feature: Direction of Underground Infrastructure

Overview of Infrastructure Equipment R&D
Supporting the Next-generation Networks
Hiroshi Moriya and Shuichi Komatsu†
Abstract
To support the next-generation networks, underground infrastructure equipment must have the capacity to handle with the widespread deployment of optical access systems in addition to long-term equipment stability. This article describes the overall approach to research and development of equipment
management technology, equipment maintenance technology, and disaster prevention and security technology required for future infrastructure equipment.

1. BackgroundNTT’s underground infrastructure equipment has
been playing an important role in the rapid formationof optical networks for both the backbone and accesssystems and in the deployment of broadband services. Providing infrastructure equipment that willcontinue to provide enough underground space toensure stable quality and support the required services in future is an important requirement of NTT’s
medium-term management strategy target of acquiring 30 million optical access subscribers by 2010. At
NTT Access Network Service Systems Laboratories,
we are conducting research and development (R&D)
of equipment management technology to appropriately manage the quality and quantity of infrastructure equipment. We are working on technology thatwill contribute to the creation of a long-term plan formaintaining and managing equipment as well as supporting technologies that include inspection andrepair technologies and disaster prevention and security technologies.
2. Current problems and needs
2.1 Tunnel/conduit capacity
NTT has at total of 600 km of cable tunnels,
630,000 km of cable conduits, and 840,000 utility† NTT Access Network Service Systems Laboratories
Tsukuba-shi, 305-0805 Japan
E-mail: skomatsu@ansl.ntt.co.jp12holes for all of its carrier companies (Fig. 1).
Although the average usage rate for conduit equipment is not high nationwide, there are concerns abouta shortage of conduit facilities and an increase inrequired investment for them, especially in urban
areas where demand for optical services is rapidly
increasing. Accordingly, we need to develop a newplanning method that will allow us to minimize newinvestment in equipment while effectively utilizing
existing facilities. We also need effective techniques
for managing underground spaces.
2.2 Equipment deterioration
Like other social infrastructure equipment, NTT’scable conduits were built intensively in the rapidgrowth period of 1965 to 1985, so almost half of theequipment is more than 30 years old. Estimates showthat the ratio will reach 80% in the next 10 years. Furthermore, most cable tunnels were constructed
between 1970 and 1990, so cable tunnels are aging
too (Fig. 2). Cases of obstacles to cable installationsuch as corrosion or earth intrusion are increasing inaged and degraded conduits. Trouble caused bycracks or water leakage as a result of deterioration ofsteel-reinforced concrete or reinforcing steel isincreasing in cable tunnels. If such deterioration
problems are not resolved, large-scale repair andreinforcement projects will probably be required,
which will further increase the cost in the future.
Therefore, we need an equipment management
method that will ensure inspection and repair work
are executed at the appropriate time and can provide
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Equipment R&D

Underground cableconduits: 40,000 km

Mid-size diameter
conduits: 210 km

Attached to bridges: 38,000 places
Cable bridges: 3000 places

Cable conduits:
630,000 km(including undergroundcable conduits)

Cable tunnels: 600 km(1000 km if multi-purpose
conduits are included)

Utility holes and handholes: 840,000 units

Fig. 1. Overview of NTT’s infrastructure equipment.

(1000 km)180

Annual conduit construction

Annual tunnel construction

(km)
140

160

120120Vinyl tube

100

Steel pipe80Cast-iron pipe

60

Tunnel length

Conduit length

140
100

Shield80

Shear-cut

60

Mountain

40

40

20

2000up to 1955 –1965 –1970 –1975 –1980 –1985 –1990 –1995 –2000 –2004
1955 to1960
Years elapsed after tunnel constructionup to 1955 –1965 –1970 –1975 –1980 –1985 –1990 –1995 –2000 –2004
1955 to1960
Years elapsed after conduit constructionin 5 years(10,000 km)
30
70%
25

in 10 years(10,000 km)
30

20

20

15

15

10

10080%

25

5in 5 years

50 to 920 to 2940+
10 to 1930 to 39 (years)0in 10 years

(km)
250
200

35%

150

100

1005050

00 to 920 to 2940+
10 to 1930 to 39 (years)

65%

200

150

0 to 920 to 2940+
10 to 1930 to 39 (years)

Cable conduits

(km)
250

00 to 920 to 2940+
10 to 1930 to 39 (years)

Cable tunnels

Fig. 2. Transition of equipment construction and deterioration issues. The numbers in red show the percentage ofequipment that will be at least 30 years old.

long-term maintenance and minimize management
costs while predicting equipment degradation. At thesame time, inspection and repair/reinforcement technology must be upgraded and technology for achieving economical efficiencies is also needed.

Vol. 4 No. 6 June 2006

2.3 Manpower
Although there are currently about 2000 engineers
working on infrastructure equipment-related operations in the NTT Group as a whole, the number is
expected to decrease greatly in the years to comebecause of pressure to hire fewer new employees
13Special Feature

while many engineers will be retiring (Fig. 3). In thefuture, it will be necessary to restructure equipment
databases and upgrade operations technology to efficiently provide services with stable quality using vast
amounts of complex infrastructure equipment withthe minimum amount of human effort.
3. Direction of R&D on infrastructure
equipment technology
In response to the above issues, we are developing(Persons)
600

Current status
in 5 years (forecast)in 10 years (forecast)

300

2030

4050AgeFig. 3. Transition of NTT’s infrastructure equipment
engineers.

the following technologies as part of our R&D strategy for the future telecommunications infrastructure
for the coming ubiquitous broadband age (Fig. 4).
3.1 Equipment management technology
3.1.1 Quantitative management ofinfrastructure equipment
We are working to establish equipment management technology that includes equipment planningtechniques for the period in which metallic and optical cables will coexist and decision-making techniques for investing in equipment.
3.1.2 Management of maintenance and repair
technologies for infrastructure equipment
We are investigating techniques for creating longterm maintenance and repair plans by diagnosing thequality of equipment and evaluating the lifecycle
cost.
3.1.3 Upgrading of the infrastructure equipment
database technology
We are working on upgrading infrastructure equipment database technology to allow precise identification of the amount of equipment, its location, and its
quality using the latest GIS (geographical information system) and GPS (global positioning system)
technologies and to allow efficient management ofequipment.

NTT’s mission • Achieve nationwide deployment of optical broadband network and a ubiquitous environment.
• Secure further reliability so that the network can be used as a lifeline.
• Stabilize the financial base and reinforcing competitiveness.
(from mid-term business plan)
Requirements • Provide capacity to accommodate 30 million optical subscribers.
of equipment • Secure stability that does not interrupt communications.
infrastructure • Minimize maintenance & management costs.
Equipment
infrastructure
issues• Accommodation capacity is being strained by the overlap of metallic andoptical cables.
• Concern over increased maintenance & management costs anddecreased reliability of the network as a whole due to further degradation• Concern over insufficient management of facilities due to reduced
equipment technology◆ Equipment management
technology◆ Equipment maintenance& repair technology◆ Disaster prevention &security technology

Fig. 4. Directions of infrastructure equipment R&D.

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Special Feature

3.2 Equipment maintenance and repair
technology
3.2.1 Non-destructive inspection and analysis
technology
This is technology for performing non-destructive
inspection and analysis using electromagnetic or
ultrasonic waves to identify the exact status of degradation of concrete or steel structures. We havealready put to practical use technology for measuringcracks in concrete and measuring concrete thickness
and are currently developing further advanced technology for measuring the status of reinforcing steel
corrosion and concrete strength degradation.
3.2.2 Metal conduit repair technology
Pipe-cameras and various lining technologies havebeen put to practical use for inspecting and repairing
vacant conduits. At present, we are developing repair
technology for cable-accommodating conduits andbridge conduits.
3.2.3 New infrastructure equipment
construction technology
We are currently investigating new construction
methods to reduce the lifecycle cost by improving
durability and new structures such as free-space conduits or new utility hole iron covers. We are also
working on environmental technologies that utilize
waste material from optical cables.

3.3 Disaster prevention and security technology
3.3.1 Quake resistance technology to support
infrastructure equipment
To ensure the reliability of networks against disasters, especially earthquakes, we have been conducting
R&D of quake resistance technologies. That includes
efforts to make existing cable tunnels and conduits
resistant to earthquakes. At present, we are investigating simulation and evaluation technologies for evaluating the quake resistance of underground equipment as
a whole, including cables, and looking at technology toreinforce cable bridge equipment against earthquakes.
3.3.2 Optical sensing technology
Using optical sensing technology for measuring
distortion in structures utilizing the characteristics ofreflected light in optical fibers, we are currently conducting R&D in disaster prevention technology forvarious types of social infrastructure such as tunnels,road slopes, and bridges [1]. We are using that technology in actual business via NTT group companies.
4. Future of infrastructure equipment business
By conducting the R&D mentioned above, we areaiming to establish a business style where equipment
management technology and the hardware technologythat supports it are unified so that it can functionsmoothly in a cycle that includes maintenance andmanagement planning, inspection and repair, and history management of infrastructure equipment (Fig. 5).
PointsManagement system applications
Maintenance &management plan

Infrastructure
equipment
database

LCC
calculation ···application

Equipment
maintenancecost per year, etc.

• Create a long-term maintenance& management plan that takes
into consideration LCC &investment equalization.

Reliability
evaluation
application

Degradation
judgment ···application

List of equipment
to be repaired,etc.

• Implement continuous inspection &diagnosis.
• Accumulate degradation information
and analysis results in a database.

LCC
calculation
application

Repair method
determination ···application

Reliability
evaluation
application

Measurement
equipmentInspection
Diagnosis
Infrastructure
equipment
database
Repairing &reinforcing

History
management

Infrastructure
equipment
database• Results of inspection• Repair methods,
date of execution, etc• Results of repairing& reinforcing

Infrastructure
equipment
database• Implement precise and timely
repairing & reinforcing.
• Accumulate results of repairing& reinforcing in a database.
• Establish platforms such as
infrastructure equipment databases
and management systems as earlyas possible.

LCC: life cycle costFig. 5. Concept of future infrastructure equipment business.

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Special Feature

NTT in-house use:
• Infrastructure equipment• Building structures

Social infrastructure market:• Roads• Sewers• Railways • Buildings

Cooperate with other organizations from the startof R&D with an eye to applying results for NTT
in-house use and the social infrastructure markets.
NTT Group

NTT InfraNet

Airec Giken(equipment managementtechnologies)(diagnosis, renewaltechnologies)

NTT AT(basic technologies)

NTT Access Network Systems Labs.

Other research labs
• Universities• Public works researchinstitute• National Research Institutefor Earth Science andDisaster Prevention• Lifeline companies

NTT East
Technical Assistance& Support Center

Telecom construction
companies(materials technologies)(engineering technologies)

Consultants

Other NTT labs

(quake resistancetechnologies, etc)

(basic echnologies)

Related research organizations

Fig. 6. Infrastructure equipment R&D framework for application to in-house use and the social infrastructure market.

In this cycle, the following points are important.
• Creation of long-term maintenance and management plans, taking into account the lifecycle costand equalization of investment based on theresults of inspection and analysis• Continuous implementation of inspection andequipment diagnosis and accumulation of a database including degradation status and diagnosis
results• Implementation of precise and timely repair andreinforcement and records showing the history of
the results• Early establishment of platforms for constructing
infrastructure equipment databases and management systems
5. Deployment in the social infrastructure
marketRefining the equipment maintenance and management technologies described above is also related toJapan’s social infrastructure as a whole, including
roads, railways, and sewers. People have become
more concerned in recent years about the safety andreliability of the social infrastructure after several
incidents involving concrete falling from the ceilingsof railway tunnels, landslides occurring after heavy
rain, and inadequate earthquake resistance being discovered in recently constructed buildings. NTT
Access Network Service Systems Laboratories islooking at deploying its technology in the social
infrastructure market in addition to applying it for
16

NTT in-house use. From the early stages of R&D, wecoordinate with other NTT group companies as well
as related research organizations to conduct productdevelopment that makes the most of NTT’s strengths(Fig. 6).
Reference[1]

K. Fujihashi, H. Uehara, M. Okutsu, and K. Komatsu, “Developmentof a Road Disaster Monitoring System Using Optical Fiber Sensing
Technology,” NTT Technical Review, Vol. 1, No. 9, pp. 48-52, 2003.

Hiroshi Moriya
Senior Research Engineer, Civil Engineering
Project, NTT Access Network Service Systems
Laboratories.
He received the B.E. degree in civil engineering from Hokkaido University, Hokkaido, in
1977. He joined Nippon Telegraph and Telephone Public Corporation (now NTT), Tokyo, in
1977 and has been engaged in research on underground telecommunication facilities, especiallyon no-dig technology. In 2002, he was transferred to NTT Access Network Service SystemsLaboratories. He is a member of the Japan Society of Civil Engineers (JSCE).

Shuichi Komatsu
Research Engineer, Civil Engineering Project,NTT Access Network Service Systems Laboratories.
He received the B.E. degree in civil engineering from Nagoya University, Aichi, in 1986. He
joined NTT, Tokyo, in 1986 and has mainly been
engaged in the design of cable tunnels. In 1999,
he was transferred to NTT Access Network Service Systems Laboratories. He is a member ofJSCE.

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