R&D Spirits
Optical Access Systems: The Key to Making
Broadband Services Economical
Yoichi Maeda
Senior Manager, Global Strategy
Group Leader, Full Service Access Systems Group
Optical Access Systems ProjectNTT Access Network Service Systems Laboratories

Today we are finally seeing the all-out commercial introduction of optical access systems
around the world. In the midst of that development, what next-generation optical access systems
does NTT envision for the future? Also, how is NTT working toward international standardization of its optical access systems? We asked these and other questions to Yoichi Maeda of NTTAccess Network Service Systems Laboratories. Mr. Maeda, the group leader in the Full Service
Access Systems Group, has promoted systems development for many years and has been
aggressively involved in promoting international standards for optical access systems.

Optical Access Systems as Economical Social
Infrastructure that Anyone Can Use
Editor: What are some of your group’s current
research themes?
Maeda: Our group is currently conducting R&D ofoptical access systems aiming to provide economical
broadband services for Internet access and video content distribution. Actually, high-speed broadband
communications using fiber optics for access hasbeen an R&D theme at NTT’s research laboratories
for over 25 years. It is only in the past few years, however, that the results of that research have been pulled
together and made economical to use. My personalresearch has been mainly in applications of ATM
technology, in applications of transmission technology at the optical medium level, and in communications control technology for point-to-multipoint networks shared by multiple customers through a single
optical fiber (passive optical networks (PONs)).
Besides R&D, I have participated in international
standardization activities for leading-edge technology.
E: What are the main technical points of optical
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access systems?
M: The most important point in our research is thePON. In a passive network, optical splitters are
installed between central offices and customer
premises for combining or splitting power from optical fibers. That technology enables economical communications by allowing up to 32 customers to sharea single optical fiber. Once that happens, it means thatthe customers also share the devices in the central
office. In the future, when optical access develops tothe point where it handles millions or even tens ofmillions of users, PONs will become effective as ameans of coping with a shortage of space in central
offices. A second important point is a communications protocol for efficiently transmitting signals for
the Internet, images, and sound at a high quality level.
A new protocol will be needed to transmit various
types of signals by multiplexing them through a single optical fiber and sending them to multiple customers.
E: What is the current status of your group’s work,and what specific tasks does your group face?
M: The initial basic report for our B-PON (BroadNTT Technical Review

R&D Spirits

band PON) system (Fig. 1) that provides Internet
access in the 100-Mbit/s class was submitted to ITUT in 1997. As of the end of 2002, a total of eight Recommendations were prescribed and one series ofstandardization was completed. Now the remaining
tasks are in progress, such as making the technology
economical to use and introducing it as smoothly asfeasible. Those tasks are mainly to be carried out by
the NTT Group companies with the support of NTT
Laboratories. Our group will then move toward conducting R&D for next-generation technology. A concrete example is research to raise the access speed ten
fold, i.e., from the Mbit/s to Gbit/s class.
E: With such technology, what can we expect to happen three to five years from today?
M: As an extension of current research, three years
from now we can expect to see a Gbit/s-class PON
developed. That technology will make it possible toprovide a full range of services, including the transmission of higher quality digital images and voice.
Five years from now, we can expect to see an accessnetwork that utilizes wavelength division multiplexing (WDM) and provides speeds in the 10-Gbit/sclass.
Remember, however, that our research is not aimed
solely at achieving higher transmission speeds. We
hope that by improving the performance of accessnetworks it will become possible to transmit data that
previously could not be transmitted, thus leading to
the creation of new services. Eventually, networks
capable of quickly transmitting large volumes of data
will become part of the social infrastructure, much
like water pipes and expressways. Our aim is to provide networks that all sorts of customers can use withthe convenience and security.

Widespread International Activities with
Ultimate Aim of Contributing to CommonStandards
E: What are the main domestic and overseas trends in
optical access systems research?
M: Optical access systems are expected to become
the social infrastructure that supports the future ageof broadband information technology. Among thedifferent access technologies being studied, B-PON
is expected to become the most standard and stable
technology. In 1997, NTT was the first company inthe world to offer B-PON services commercially. The
service at that time was aimed at business customers
utilizing dedicated lines. From September 2002, a BPON for use with B-FLET’S was introduced for general users, and there are now already over 150,000
subscribers to that service.
In North America as well, SBC, Bell South, andCentral Office

Customer premiseInternet access service

1.49 µm

Data communication(100 Mbit/s)
Optical splitter 1.49 µm

B-ONUInternet

1.31 µm

Contents delivery service

B-OLT
Contents
deliveryserver

1.31 µm

100BASE-TX
WDM

WDM

Coax
V-ONU
MAX: 32Branches

Optical fiber
1.55 µm
V-OLTVideo distribution
Multi-channel
video distribution service

B-ONU (Broadband-optical network unit)
V-ONU (Video-optical network unit)

1.55 µm

Tx

Broadcasting
centerTx (Video signal transmitter)
B-OLT (Broadband-optical line terminal)
V-OLT (Video-optical line terminal)

Fig. 1. Broadband passive optical network system (B-PON).

Vol. 1 No. 6 Sep. 2003

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R&D Spirits

Verizon—three leading carriers—announced in June
2003 that they would jointly procure optical accesssystems using B-PON. Their overall plan is large
scale, with expected purchases of over one million
systems. PON systems can thus be said to have finally reached the stage of all-out introduction. NorthAmerican carriers, however, are just beginning to use
optical fibers. Preconditions for those carriers, therefore, from the viewpoint of cost/effectiveness areproviding triple plays which include telephone, video
distribution for CATV, and data communications overthe PON system. That is quite different from Japan,
where PON systems are developing solely for use
with data communications.
In Europe, moves toward commercializing PON
systems began quite early. Before long, though, large
amounts of capital were required to purchase therights to use wavelengths for mobile communications. That derailed the business strategy of the European carriers. Although they were quite aggressive intheir approach, they have therefore not yet been able
to introduce systems on a large scale.

M: I have participated in international standardization activities since 1989, initially with CCITT(International Telegraph and Telephone ConsultativeCommittee; today’s ITU-T), mainly related to defining common standards for ATM technology for BISDN and optical access systems. I am currently vicechairman of ITU-T SG13 (SG: study group) and WGChairman (WG: working group) of the Full ServiceAccess Networks (FSAN; see Fig. 2) consortium.
Because of those activities, my schedule has me traveling overseas more than 100 days a year.
E: What are ITU-T’s main activities at present?
M: Four years is considered one research period at
ITU-T, and next year marks the end of the current
period. Discussions are thus underway for selecting
research themes for the next four-year period. InSG13, NTT wants to work toward a common standard for networks that will be linked to its concept ofresonant communication networks. Optical access
related discussions, the bailiwick of SG15, are currently focused on resolving problems that occasionally arise with B-PON systems and initiating a neweffort for standardizing PON networks operating at
bit-rates above one Gbit/s.

E: What international activities does your group conduct, including in the area of standardization?

Telia

Eirecom

VerizonKTBTNTT
KPN

Bezeq

DTAG
FT

Bell Canada
Chunghwa

SingTelSwissCom

TelstraTI

Qwest

Telefonica

BellSouth
SBC
Malta
As of September 2003, 21 telecom carriers and 29 vendors

AFC

Agere

Broadcom

BroadLight

Ericsson

FlexLight

Fujitsu

Hitachi

Iamba

Intel

LucentMarconi

Mitsubishi/Paceon

Nortel

OFN/OkiOptical Solutions

ST Microelectronics

AlcatelSamsung

CISCO

Entrisphere

Infineon

INOVIA/ECIMotorola

NEC

Quantum Bridge
Terawave

VinciZonu

Fig. 2. Companies participating in FSAN.

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NTT Technical Review

R&D Spirits

Our work at ITU-T, incidentally, is not to create
standards after networks or systems have been completed but to prepare them ahead of time. There areresearchers who believe that differentiation should bea company’s top priority and that standardization hasa low priority. But researchers working together toprovide a clear direction to future research can lead toenhanced R&D activities. That is why I do not viewmy standardization work as simply a side job. It isalso physically tiring work, but that is no reason tostop either.
E: What are some of the activities of FSAN?
M: FSAN was founded in 1995 on the initiative ofNTT. At present, its members include 21 carriers
from around the world, centered on NTT and six
European carriers (BT, FT, etc.), and 29 vendors. As
its name implies, the group’s goal is to create common standards for access systems that will support awide variety of services. The carriers create the basic
policy for technological development and the vendors
propose specific solutions. FSAN is also a venue forthe participating companies to exchange opinions,thus promoting quick standardization. Once issues
have been basically agreed upon in the FSAN group,
they are proposed to ITU-T.

World Interest on Japan as Most Advanced
Nation in Optical Access
E: What reaction have you seen from overseas
regarding your group’s research results and otheractivities?
M: Most of our overseas work is related to standardization activities. At ITU-T, all the Recommendations
and proposals NTT offered concerning ATM and BPON were eventually officially accepted and carried
to completion. There were even several cases where I
was the designated editor. Also, as I mentioned,
because Japan is the most advanced country in termsof introducing optical access systems, there has beenquite an increase over the past two years or so in invitations I have received to give lectures and write
papers on trends in standardization and commercialization. Our accomplishments and the favorable
response from others are due mainly to the support ofmany persons. I interpret that to mean that our activities to date, including meeting so many otherresearchers, have been evaluated positively.

Vol. 1 No. 6 Sep. 2003

E: Based on your personal experience, how do you
think the rest of the world views NTT?
M: From 1989 to 1990, I spent one year as anexchange research engineer at BT Research Laboratories in the UK. That experience provided me theopportunity to view NTT from the outside. Eventually, I came to realize there are few organizations likeNTT anywhere in the world that conduct wide-ranging research on such a large scale. Today, in fact, NTTmight be the only organization in the world with suchlaboratories. In a large research organization likeNTT Laboratories, it is possible to conduct widely
varied discussions on a single theme. And when technical proposals are made, it is possible to obtain various background supports, making the final proposals
highly credible. Concerning standardization as well,even before I began participating actively, NTT personnel before me made great contributions at theinternational level. The Synchronous Digital Hierarchy (SDH) used today in trunk systems, for example,
resulted from the tremendous efforts of current Director Yuji Inoue of NTT and current Vice President Katsuya Okimi of NTT Communications. So I think it
can be said that NTT is viewed favorably overseas interms of its technology, its human networking, and its
ability to influence the adjustments made among differing opinions.
E: What direction would you like to see your researchtake in the future?
M: My greatest interest is in seeing many people
around the world using optical access systems inexpensively. Based on a high-performance transmissionmode, I would like to provide an environment inwhich NTT can compete for service at a higher level.
I would also like to see more quality control technology and various applications linked to R&D and systems development for handling them efficiently.
That’s where the real competition will begin. For
those purposes, I would like to contribute even furtherto networking with other researchers around theworld and to constructing a future standardization
strategy for NTT.

With Rich Human Resources, NTT Provides
an Ideal Environment for Systems R&D
E: What was the original stimulus for starting yourpresent research?

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R&D Spirits

M: My main motivation was to take high-quality, stable optical transmission technology, which makes it
possible to transmit large volumes of data over long
distances, and apply it to access networks where there
is a strong demand for economy. In pursuing economical use, it was necessary not only to conduct
pure R&D of technology but also to obtain feedback
from mass production. I would also like to contribute,
through the standardization process, toward networking with other researchers and building a scheme thatwill provide for common components.
E: What have been your principal research themes upto now?
M: Actually, optical access research has taken up
only the second half of my career. In graduate school,
my studies were totally different from today. I conducted research into electronic engineering using
microwaves in the medical field. Specifically, I studied non-contact methods of measuring body temperatures for use in the early detection of breast cancer.
After joining NTT, my initial research was DataOver-Voice technology for transmitting 100 bit/s ofdata over telephone lines. After that, I moved to theLSI Design Labs for about two years to conduct
research into making subscriber circuits for digitalexchanges smaller and more economical. Up to then,resistors and capacitors had been used in those circuits. I proposed terminal circuits that processed digital signals. One result of my research was twopatents that earned me special recognition in thecompany at the time. That experience showed me
how pleasant it was to know that the results of myresearch could be used in real-life situations. Afterthat experience my research shifted with a major
move by NTT to build ultra-highspeed networks thatcould handle multimedia. My specific research wasin the development of ATM transmission technologyand efforts to have it included in international standards. That position led directly to my current
research in access-related areas.
My original major field was thus related tomicrowaves. Optics, my present field of study, also
involves waves, and many aspects of optics havepoints in common with microwaves. PON systems, inparticular, are identical to microwaves in that manysignals can propagate through the same spatial medium. Thinking like that, it was perhaps fortuitous forme that I began my research career by studying wireless systems. Perhaps it is exactly because I did not
begin my career as a specialist in optical fibers that I
8was able to come up with some fresh ideas in the fieldof optics.
E: Please share with us some of your thoughts aboutthe future.
M: Rather than saying that I personally want to be
involved in some particular research in the future, I
would prefer to say that as a manager I want to createa research environment in which young researchers
can gradually come to gain confidence in theirresearch work. There is also still much difficult work
for me to do in the areas of standardization andinternational collaboration. Regarding international
collaboration, in particular, it is important to work
further to solidify the presence of NTT Laboratories
on the world stage. In that context, I am continuing towork toward creating a joint scheme with the researchlaboratories of SBC, Bell South, BT, and FT. Meanwhile, NTT Laboratories is now reviewing its organizational structure and its relationship with its business companies. Looking at the present situation, it iscertainly important to consider the business chances
we see before our eyes. From a long-term perspective, however, it is also pretty important to have anorganization which carries out investigations withnew ideas and new points of view from the perspective of future, new ideas. Based on the company’s
domestic and international activities, a clearer direction must be provided for the future. Nothing would
please me more than to have such considerations leadto the creation of an environment that would make iteasier for young researchers to conduct theirresearch.
E: What has the NTT Laboratories meant to you personally?
M: Research by an individual, even a genius, does
not build systems. Systems require an organization
like NTT Laboratories, where there are outstanding
researchers in numerous fields working together.
Such a group is extremely important for conducting
research into systems. There is great freedom alongwith responsibility in conducting research in NTT
Labs, and if a researcher wants very much to work on
a particular theme, the organization is basically flexible enough to allow him to do so. We often hear fromoverseas researchers that the environment in NTT
Labs is not one where researchers sign confidential
agreements with the organization and then conduct
research only on themes assigned to them. In thatNTT Technical ReviewR&D Spirits

sense, researchers in NTT Labs are blessed with great
freedom. Although there are areas that need improvement, NTT Labs has many fine points compared withresearch organizations in the advanced Western countries and we should strive to keep them.

Vol. 1 No. 6 Sep. 2003

Interviewee profile■ Career highlights
Yoichi Maeda received the B.E and M.E. degrees inelectrical engineering from Shizuoka University,
Hamamatsu, Shizuoka Prefecture, in 1976 and 1978,
respectively. Since joining NTT in 1980, he has been
engaged in research and development on access network transport systems for broadband communications, including SDH, ATM, and IP. From 1988 to1989, he worked for BT (formerly British Telecom)
Research Laboratories, UK, as an exchange researchengineer. He is now a senior manager of Global Strategy and manages the Full Service Access Group ofNTT Access Network Service Systems Laboratories.
Since 1989, he has been an active participant in
ITU-T SG13 and SG15. He is currently serving as thevice-chairman of ITU-T SG13 and as WG chairman ofthe FSAN committee. He is a member of IEEE and theInstitute of Electronics, Information and Communication Engineers (IEICE) of Japan. He has publishedseveral books on B-ISDN standards, including Introduction to ATM Networks and B-ISDN (John Wiley &Sons).
■ Major awards
2002 ITU-AJ (the ITU Association of Japan Inc.)
Award
2003 TTC (The Telecommunications TechnologyCommittee) Award

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