NTT Technical Review

September 2016 Vol. 14 No. 9

Feature Articles: Device Technology Development for Beyond 100G Optical Transport
Network

Device Technology Development for Beyond 100G Optical Transport Network

Digital Signal Processor (DSP) for Beyond 100G Optical TransportCompact Optical Modulator and Coherent Optical Subassemblies for Beyond 100G Transport
Network

High-sensitivity 4-channel Receiver Module with Avalanche Photodiode for 400-Gbit/s
Ethernet

High Frequency Optical Module Assembly Technique Enabling High Modulation Speed over
100 Gbit/s/λGlobal Standardization Activities


Promotion of Environmental Management According to ITU-T L.1410 in NTT Group

Global Activities of NTT Group

Arkadin: Global Unified Communications & Collaboration Champion in a Dynamic Digital
Workplace

New NTT Colleagues


BIT.Group / VietUnion

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

Feature Articles: Device Technology Development for
Beyond 100G Optical Transport Network

Device Technology Development for
Beyond 100G Optical Transport
Network
Masahito Tomizawa, Akimasa Kaneko,
and Shunji Kimura
Abstract

The capacity of the optical transport network has been expanding for over 30 years, which has enrichedthe communication environment of users. This expansion has also helped to reduce the cost of communication lines and facilitate the growth of the Internet and the widespread use of smartphones. In the near
future, an optical transport network with a capacity beyond 100 Gbit/s per wavelength (beyond 100G
optical transport network) and its device technology will be needed in order to provide more sophisticated communication services such as IoT (Internet of Things) and 5G (fifth-generation) mobile access.
This article reviews NTT laboratories’ development of device technology for the beyond 100G opticaltransport network.
Keywords: optical transport network, device technologies, beyond 100G

1. Introduction
Expectations for communication networks havebeen increasing more and more in recent years. The
development of the Internet of Things (IoT) is one
example of such an expectation. The IoT is expected
to make people’s lives richer by connecting and controlling all things via networks. The fifth-generation(5G) mobile access network, which smoothly bridges
numerous users/things and core networks in the IoT
world, is also attracting attention. It is an opticaltransport network whose device technology supports
the realization of IoT from the viewpoint of long-hauldata transmission.
The capacity of the optical network has been
expanding for over 30 years, which has enrichedpeople’s communication environment (Fig. 1). Fromthe 1980s to the early 1990s, time-division multiplexing (TDM) techniques were developed to reduce thecost of communication lines and to realize integrated
services digital networks (ISDNs). With TDM techniques, the capacity of the optical transport network1reached 10 Gbit/s per optical fiber. From the late
1990s through the 2000s, progress was made inwavelength-division multiplexing (WDM) techniques in order to cope with the rapid growth in Internet traffic. WDM techniques finally reached a capacity of 1 Tbit/s per fiber. Digital coherent technology
has been applied since the 2010s, which has boosted
the capacity to manage drastic increases in trafficcaused by the widespread use of smartphones. At
present, 8 Tbit/s per fiber capacity has already beenrealized and utilized in real systems.
Digital coherent technology is very different fromconventional TDM and WDM techniques in terms of
the light modulation scheme for carrying digital data.
While conventional TDM and WDM techniques use
only optical intensity for light modulation, digital
coherent technologies modulate not only opticalintensity but also the optical phase. Moreover, digital
coherent devices can multiplex light polarization,
whereas TDM and WDM devices cannot.
Because light parameters for carrying digital data
are increased in digital coherent technology, theNTT Technical Review

Feature Articles

1985
Optical fiber network
through Japan

Opticaltransport
networktechnology

Transmission capacity per fiber

Network
services(Bit/s)1P

40G-DWDM
ROADM

1T

WDM tech.

100G-PTS

Digital coherent
tech.

10G-DWDM

FA-10GTDM tech.

ADM10G

1G

Device technology for
opticaltransport
network

2013 100G-PTS2008 Next Generation Network
2004 ROADM
2000 B FLET’S

F-1.6G FTM-2.4G

DFB-laser
FC connectorl
Signa gssin
400G-DSP proce es
devic
100G-DSP
onic
electr40G OTN-LSI
COSA
Opto ices
Optical fiber amp.
v
de
InP modulators
Coherent receiver
ROADM
switchSC connector
40G demodulator
AWG filter
Optical splitter
PLC tech.

Optical fiber mass-production method: VAD method
1980
ADM: add/drop multiplexer
AWG: arrayed waveguide grating
COSA: coherent optical subassembly
DFB: distributed feedback
DSP: digital signal processor

1990

Bending free fiber

2000

DWDM: dense wavelength division multiplexing
FC connector: fiber transmission system optical connector
FTM: fiber termination module
LSI: large-scale integrated circuit
OTN: optical transport network

2010

Multi-core fiber
2020 (Year)

PLC: planar lightwave circuit
PTS: packet transport system
ROADM: reconfigurable optical add/drop multiplexing
SC connector: single fiber coupling optical fiber connector
VAD: vapor-phase axial deposition

Fig. 1. Transition of optical transport network and device technologies.

capacity per one wavelength of light has reached 100
Gbit/s at present. (When WDM techniques were theprevailing technology, a few dozen wavelength signals were multiplexed in one optical fiber. At the endof the WDM era, 40-Gbit/s capacity per wavelength
had been achieved due to steady progress in TDM
techniques.) As mentioned so far, digital coherent
technology adopts a more complex light modulationand multiplexing scheme than those of conventional
TDM and WDM techniques, and it is the optoelectronic devices that physically realize the complex
digital coherent technology. Communication traffic
in the world of IoT with 5G mobile access is expected
to continue to increase, so an optical transport network beyond 100 Gbit/s per wavelength (hereafter,
100 Gbit/s/λ; λ (lambda) = wavelength), referred toas a beyond 100G optical transport network is highly
desirable by people all over the world.
2. Requirements for beyond 100G opticaltransport network and development strategy for
associated devices
Three requirements for the beyond 100G opticalVol. 14 No. 9 Sept. 2016transport network and the strategy of developing theoptoelectronic devices used with it are summarized inTable 1. NTT laboratories established the development strategy in order to meet the requirements, anddevelopment of the optoelectronic devices is underway to achieve the beyond 100G optical transport
network. The details of the development strategy aredescribed below.
2.1 Expanded capacity
Communication traffic will continue to increase in
the next generation, and it will be vital to expand thecapacity in order to meet the increase. In particular, it
is important to find a way to transport mobile traffic
long distances at reasonable cost as soon as possible.
Mobile traffic is currently growing at 1.4 times thecurrent amount per year. Although 8-Tbit/s total
capacity optical transport systems with 100 Gbit/s/λwere installed in 2013, 30-Tbit/s-class systems with
400 Gbit/s/λ are expected to be necessary by 2017 to
support the growing mobile traffic. Optoelectronic
devices used for such optical transport systems
should be ready one year ahead of the time they areneeded; therefore, research and development (R&D)
2

Feature Articles

Table 1. Optical transport network requirements and device development strategy.
Requirementsfor opticaltransport
network

Expanded capacity• Multi-level coherence (xQAM)
Device• Faster modulation
development(higher baud rate)
strategy

Downsizing of opticaltransport equipment• Choosing appropriate materials fordevices and optimizing device design

Low latency• Expansion of domain of opticaltechnologies(ultralong-haul optical transmission,
optical switches w/o EO/OE conversion)• DSP implementing QPSK and• Optical modulator and receiver using• DSP equipped with soft-decision
Concrete
16QAM
InP and Si
forward error correction (SD-FEC)
development • Optical transmitter and receiver• DSP using state-of-the-art miniaturized and frequency domain equalization
activities
corresponding to QPSK and 16QAM CMOS process (20 nm, 16 nm)
CMOS: complementary metal-oxide semiconductor
EO/OE: electrical-optical/optical-electrical
InP: indium phosphide

QAM: quadrature amplitude modulation
QPSK: quadrature phase-shift keying
Si: siliconof optoelectronic devices must be done quickly andefficiently.
NTT laboratories have been focusing on digital
coherent technology as a way to expand the capacityof the optical transport network. R&D is underway on
more sophisticated modulation schemes such as
16-level quadrature amplitude modulation (16QAM),
as well as conventional optical modulation schemes
such as quadrature phase-shift keying (QPSK). We
are also working to increase the speed of modulation(baud rate). By combining a more sophisticatedmodulation scheme and a faster baud rate, we will beable to achieve a much larger capacity of the opticaltransport network in the near future. One concrete
example of this is that NTT laboratories are trying to
implement a more sophisticated modulation scheme
and a faster baud rate into a digital signal processor(DSP), which is the heart of the optical transport network utilizing digital coherent technology. As for the
optical transmitter and receiver, we are focusing
especially on the coexistence of highly linear inputoutput characteristics and faster performance, which
are essential for implementing a more sophisticatedmodulation scheme and faster baud rate.
2.2 Downsizing of optical transport equipment
The volume of optical transport equipment affects
the size of the facility of the communication carriercompany, so compact assembly/packaging is essential. If the communication traffic is increased several
times with the new equipment, the volume of theequipment will need to be equal in size or smaller
than the previous equipment. In recent years, not only
have the facilities of communication carrier companies been directly connected to the optical transport
3

network in order to deliver information long distances, but so too have datacenters run by information
technology companies. The allotted space for equipment in datacenters is very limited, so compact
assembly/packaging is mandatory when installing
optoelectronic devices in datacenters.
Two aspects in the R&D of optoelectronic devices
that are important in order to achieve compact assembly/packaging are: 1) making each device smaller,and 2) reducing power consumption to prevent theinevitable problem of heat radiation in smaller size
devices. For example, although a 100-Gbit/s/λ digital
coherent optical transceiver (commercialized in2013) has a footprint of 5 inches × 7 inches (12.70 cm
× 17.78 cm), a 1.6 inch × 4.2 inch CFP2-ACO (centum (100) gigabit form-factor pluggable 2 - analogue
coherent optics, 4.06 cm × 10.67 cm) optical transceiver has been developed and is being commercialized in 2016. From now on, making devices smaller
and reducing power consumption will remain important tasks, and progress in these areas will continue
rapidly.
To make devices smaller, NTT laboratories choose
appropriate materials for optoelectronic devices andoptimize the device design. Selecting high refractive
index materials such as indium phosphide (InP) andsilicon (Si) helps in reducing the sizes of optoelectronic devices, but we are also focusing on optimizing
the device design so as not to degrade the opticaltransport performance. Also, to reduce power consumption, NTT laboratories have been researchingand developing ways to reduce the driving voltage of
optical modulators. Optical modulators using InP area representative example of such development, andthe details are described in the other Feature Articles
NTT Technical Review

Feature Articles

InP optical modulator

Coherent Compact coherent
DSP
optical subassembly
Flexible circuit forelectricalinterface

Input/output
fiber

Datacenters
Core network

Metro network
SubcarrierRadio frequency
substrate

Electro-absorption
distributed
feedback laser

Access network

Flip-chip-bonding
substrate

Optical transmitter /receiver for Ethernet

Fig. 2. Devices developed for optical transport network.

in this issue. As for DSP, the use of a state-of-the-art
complementary metal-oxide semiconductor (CMOS)
miniaturized process made it possible to achieve adrastic reduction in power consumption. While
40-nm and 20-nm CMOS miniaturized processes
were used in developing the DSP, a 16-nm process—the first in the world—is being used in the most recent
development to further reduce power consumption.
2.3 Low latency
In the near future, many applications using thecommunication network will be introduced. These
applications include those for services that requirereal-time responses and that have low latency. Examples for such services include highly sophisticatedfinancial services and smart cars connected to thecommunication network.
The total latency of network services mainly
depends on the configuration of servers and the architecture of the network. However, in terms of the optical physical layer, reducing the latency inside theoptical transport equipment is effective in reducing
the overall latency. The most effective way to reduce
latency is to reduce the number of times data packets
are stored and forward-processed after optical-toelectrical (OE) conversion, or in other words, toreduce the number of core routers. Moreover, if OE
and electrical-to-optical (EO) conversions were
excluded as well as the decreased number of corerouters, much lower latency would be obtained.
Vol. 14 No. 9 Sept. 2016

These technical trends require expanding the domainof optical technologies, for example, extending thetransmission distance of optical signals without OE/
EO conversion relay and routing optical signals without the OE/EO process.
To contribute to the low latency of the communication network using optical technologies, NTT laboratories have been researching ways to extend the reachof optical signals in the optical transport network andinvestigating switching techniques that do not require
OE/EO conversions. The following Feature Articles
introduce NTT’s development of a DSP implementing soft-decision forward error correction (SD-FEC)
and frequency domain equalization to extend theoptical transmission distance.
3. Future overview
The final goal of NTT laboratories, especially NTT
Network Innovation Laboratories and NTT Device
Innovation Center, is the widespread use of thebeyond 100G optical transport network. To achieve
this goal, we are continuing our R&D on state-of-theart technologies and fabrication of easy-to-use devices in a timely manner based on the development
strategy described earlier. The Feature Articles in thisissue introduce the following devices, which havebeen developed according to this strategy (Fig. 2).
(1)	Coherent DSPs: These are the heart of the optical transport network with digital coherent
4Feature Articles

technology [1](2)	InP coherent optical modulators and compact
coherent optical subassembly: These have thecompact size needed for the next generation of
optical transport equipment and achieve adequate performance by working in conjunction
with coherent DSPs [2, 3](3)	Optical transmitter and receiver for high-speed
optical Ethernet: These are essential opticalcomponents for connection between routers/
switches in client-side and coherent systems [4]References[1]

Y. Kisaka, M. Tomizawa, and Y. Miyamoto, “Digital Signal Processor

Masahito Tomizawa

Executive Research Engineer, Senior Manager,
Photonic Transport Network Laboratory, NTT
Network Innovation Laboratories.
He received an M.S. and Ph.D. in applied physics from Waseda University, Tokyo, in 1992 and2000. From 2003 to 2004, he was a visiting scientist at Massachusetts Institute of Technology,
USA. He has been engaged in R&D of highspeed optical transmission systems. Since 2009,he has been a project leader of the 100G Centerof-Excellence (CoE) Consortium consisting ofseveral manufacturing companies and is responsible for the development and marketing strategies of 100G coherent DSPs. In 2013, hereceived the President’s Award of the Ministry ofInternal Affairs and Communications of Japan
from the Telecommunication Technology Committee for his contributions and leadership of theconsortium in the 100G digital coherent CoE
project. In 2015 and 2016, he received Fellowgrade memberships from the Institute of Electronics, Information and Communication Engineers (IEICE) and the Optical Society of America, respectively.

[2]

[3]

[4]

(DSP) for Beyond 100G Optical Transport,” NTT Technical Review,Vol. 14, No. 9, 2016.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201609fa2.html
N. Kashio and Y. Nasu, “Compact Optical Modulator and Coherent
Optical Subassemblies for Beyond 100G Transport Network,” NTT
Technical Review, Vol. 14, No. 9, 2016.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201609fa3.html
S. Tsunashima, S. Kanazawa, and H. Tanobe, “High Frequency Optical Module Assembly Technique Enabling High Modulation Speedover 100 Gbit/s/λ,” NTT Technical Review, Vol. 14, No. 9, 2016.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201609fa5.html
Y. Nakanishi, T. Ohno, T. Yoshimatsu, and H. Sanjoh, “High-sensitivity 4-channel Receiver Module with Avalanche Photodiode for
400-Gbit/s Ethernet,” NTT Technical Review, Vol. 14, No. 9, 2016.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201609fa4.html

Shunji Kimura

Senior Research Engineer, Supervisor, ProjectManager, Metro-Access Network Device Project, NTT Device Innovation Center.
He received a B.E. and M.E. in electrical engineering in 1989 and 1991, and a Ph.D. in electronics, information, and communication engineering in 1997, all from Waseda University,
Tokyo. In 1991, he joined NTT LSI Laboratories,
where he researched design and evaluation technologies of high-speed integrated circuits for
optical transmission systems. In 2003, he was
assigned to NTT Access Network Service Systems Laboratories, where he was engaged in thedevelopment of next-generation optical accessnetworks. He is currently a project manager at
the NTT Device Innovation Center and is leading
the development of metro-access network devices. He is a senior member of IEEE and IEICE. He
was the recipient of the 1994 Japan Microwave
Prize at the APMC (Aisa-Pacific Microwave
Conference) 1994, the 1996 Young Engineer
Award from IEICE, and Best Paper Awards at
OECC (Optoelectronics and Communications
Conference) 2010 and COIN (Conference on the
Optical Internet) 2010.

Akimasa Kaneko

Executive Research Engineer, Project Manager, Photonic Network Device Project, NTT
Device Innovation Center.
He received a B.E. in electronics engineering,
and an M.E. and D.E. in materials science from
Keio University in 1989, 1991, and 1994. He
joined NTT Optoelectronics Laboratories in
1994, where he conducted research on polymer
waveguides and silica-based planar lightwave
circuits (PLCs). He worked from 2000 to 2003 at
NTT Electronics (NEL) manufacturing PLCbased devices for optical networks. From 2009 to
2011, he was the chief technology officer at NEL
America. He is a member of the Institute of Electrical and Electronics Engineers (IEEE) and
IEICE.

5

NTT Technical Review

Feature Articles: Device Technology Development for
Beyond 100G Optical Transport Network

Digital Signal Processor (DSP) for
Beyond 100G Optical Transport
Yoshiaki Kisaka, Masahito Tomizawa,
and Yutaka Miyamoto
Abstract

As a foundation for the coming full-fledged big data society, optical communication networks must
further advance in speed, capacity, and cost-effectiveness. This article introduces beyond 100G (beyond
100 Gbit/s per channel) digital coherent optical transmission technology, which is a key to developing
high-capacity optical communication networks, and the digital signal processor (DSP) that provides corefunctions for this technology.
Keywords: digital coherent optical transmission, digital signal processing, multi-level modulation
scheme1. Introduction
Recent advances in telecommunications technology are expected to usher in a full-fledged big datasociety. These advances include the spread of FTTH
(fiber to the home), the growing use of smartphones,
the development of the 5G (fifth-generation) mobile
communication system, which provides super-highspeed mobile access, and the introduction of the IoT(Internet of Things), in which everything is interconnected via the Internet. This trend demands that weachieve further advances in the speed, capacity, andcost-effectiveness of optical communication networks, as they are the foundation for many communication services.
One technology that is expected to satisfy thisdemand and that has been gaining attention in recent
years is digital coherent optical transmission. This
uses coherent detection to improve both receiving
sensitivity and frequency utilization and employs
digital signal processing to achieve compensation forwaveform distortion, which accumulates in long-distance optical fiber transmission [1, 2]. Such waveform distortion compensation has so far been difficult
to achieve. Digital coherent optical transmission
technology is already used in high-capacity transmission systems that operate at a level of 100 Gbit/s per
1channel. With this technology, wavelength-divisionmultiplexing (WDM) optical transmission systems
with a total capacity of 8 Tbit/s have been introduced
commercially.
Currently, the standardization of 400-Gbit/s Ethernet transmission is in progress. This provides thepotential for commercial development of beyond
100-Gbit/s per channel (beyond 100G) optical transport technology. The trends in the development ofdigital signal processing technology for digital coherent optical transmission are shown in Fig. 1. There
are two possible directions for improving the technology applied to the existing 100-Gbit/s transmission:
enhancing performance and reducing power consumption. A high performance digital signal processor (DSP) needs to increase in both transmission
capacity and distance with realistic power consumption to be implemented in transmission equipment. In
contrast, a low-power DSP requires low-power consumption, a small package size, and low cost for
implementation with metro-access and datacenter
networks.
This article focuses on the former, in particular, on
extending the distance of beyond 100G transmission.
To increase the transmission capacity per fiber, it isnecessary to enhance frequency utilization. An effective way to achieve this is to increase the number of
NTT Technical Review

Feature Articles

100-Gbit/s optical transmission
technology elements
400-Gbit/s optical transmission
technology elements Digital signal

Transmission performance (transmission distance)

Adaptive
modulation/
demodulation
Adaptive
nonlinearcompensation

Higherperformance

100-Gbit/s optical transmission
technology elements
Dispersion
compensation
Polarization
controlErrorcorrection

Transmission
evaluation
Opticalmodulation/
demodulation
High-speed
ADC

Digital signal
processing
Transmission
properties
estimation

Adaptive error
correction

Existing
100G
Lower-power
consumption

processing
Linear adaptation
Dispersion
compensation
Transmission
properties
estimation
High-speed DAC

Lower-power control

Power consumption
and size
100-Gbit/s optical transmission
technology elements
Dispersion Transmission Digital signal
compensation evaluation
processing

Low-power DSP
Frequency utilization efficiency(number of wavelengths)

Lower-power
control

Transmission
properties
Data com. signal estimation
processing

ADC: analog-to-digital converter
DAC: digital-to-analog converter

Fig. 1. Technical development of digital coherent signal processing.

modulation levels in the optical amplitude and/or
phase. However, if the number of modulation levels is
to be increased, the optical signal-to-noise ratio(OSNR) required to achieve the desired symbol error
rate also needs to rise. If the transmission power isincreased to raise the OSNR, inter-symbol interference caused by the nonlinear optical effects of the
optical fiber increases, which in turn reduces the possible transmission distance. Therefore, if we are to
implement a beyond 100G optical transport system,
we need to combine a number of technologies,
including nonlinear compensation technology, which
compensates for nonlinear optical effects, and highcoding gain FEC (forward error correction). In addition, we have to consider applying adaptive modulation/demodulation technology, which adaptively
selects the modulation/demodulation method mostsuitable for the particular transmission performance
margin in order to maximize the network transmission capacity.
Another effective way to increase frequency utilization is to reduce the frequency spacing between
adjacent channels in WDM. This requires the frequency spectrum of the optical signal to be narrowed.
Nyquist filtering is essential for this because it
enables digital signal processing at the transmitter toVol. 14 No. 9 Sept. 2016

narrow the optical signal spectrum with minimum
degradation in signal quality. To develop a beyond
100G optical transport system, it is important toachieve these signal processing functions with a practical level of power consumption.
2. Digital coherent opticaltransmission technology
An overview of the digital coherent optical transmission technology is shown in Fig. 2. The modulation method most commonly used in conventional
optical transmission systems has been on-off keying(OOK), in which 1 and 0 in the optical signal used are
indicated by on and off states (intensity modulation),and the variation in optical intensity is detected by aphoto detector. When OOK is applied to transmission
at a rate of 100 Gbit/s, the degradation in transmission quality due to various waveform distortions of
the optical signal during propagation through an optical fiber becomes significant. As a result, the transmission distance is limited to only a few kilometers.
To avoid this problem, digital coherent opticaltransmission has been developed and adopted in
100-Gbit/s optical transport systems. This achieves
highly efficient and stable long-distance transmission
2

Feature Articles

Y-polarized wave

Polarization QAM modulation moduletxx

Polarization multiplexing
Multi-level phase modulation

PD

Polarization demultiplexing Carrier phase recoveryytY-polarized
wave

PD

Main digital
signal

Optical reception front-end moduleyX-polarized
wave

Local
oscillation
LD

A/D conversion + DSP

SignalLD

90° hybrid 90° hybrid

X-polarized wave

Polarization
splitter

Main digital
signal

Optical receiver

Polarization
coupler

DSP + D/A conversion

Optical transmitter

High-speed waveform distortion
arises due to crosstalk anddifferences in propagation delay
between polarized waves.

A/D conversion: analog-to-digital conversion
D/A conversion: digital-to-analog conversion

Waveform distortion compensation
by DSP

LD: laser diodePD: photo detector

Fig. 2. Overview of digital coherent optical transmission.

by not relying only on optical intensity but also using
digital signal processing to utilize the phase andpolarization of light, which are both properties of alight wave.
The main modulation scheme applied to 100-Gbit/s
optical transport is dual-polarization quadraturephase-shift keying (DP-QPSK). This modulates optical signals with four different phases and also uses
the X-polarized wave and the Y-polarized wave tocarry different signals. It achieves high receiving sensitivity by using coherent detection, in which a local
oscillator light generates an interference signal withthe received optical signal. From this interference
signal, the intensity and phase information of thereceived optical signal is detected. The two polarization-multiplexed signals can be demultiplexed using
digital signal processing. DP-QPSK achieves frequency utilization four times as high as that of OOK.
Digital signal processing can also be used at thereceiver to compensate for waveform distortions due
to chromatic dispersion, polarization mode dispersion (PMD), and crosstalk between polarization signals on the optical fiber. Consequently, optical fibertransmission over more than 1000 km becomes possible without using optical compensation media such3

as dispersion compensating optical fiber.
If the capacity of beyond 100G optical transmission
systems is to be further increased, it is necessary touse higher multi-level modulation of optical signals
such as dual-polarization 16-level quadrature amplitude modulation (DP-16QAM), which uses both optical intensity and phase. Different types of modulation
can be generated by changing modulation signals
generated using digital-to-analog (D/A) conversion
in the same hardware of the transmitter/receiverincluding the optical modulator, driver amplifier, andoptical receiver. This makes it possible to select the
optimal modulation scheme depending on the channel capacity or transmission distance required.
3. DSP for beyond 100G optical transmission
We have developed a real-time DSP for digital
coherent optical transmission through an open innovation in which a number of organizations have participated [3, 4]. This work was supported by aresearch and development (R&D) project of the Ministry of Internal Affairs and Communications (MIC)of Japan and another project of the National Instituteof Information and Communications Technology
NTT Technical Review

Feature Articles

Digital coherent optical transmitter
One 100GbE
ortwo 100GbE

DSP

Framer(LAN/WAN
conversion)

Error
correction
codingSignalmapping

Pilot signal
insertion

LAN

Transmission
spectrumshaping

D/A
conversion

Opticaltransmission
part

WAN
(OTN)

Transmission pathestimation

De-framer(WAN/LAN
conversion)
One 100GbE
ortwo 100GbE

100G DP-QPSK
or
200G DP-16QAM

Entire function control

Error
correction
decoding

Signalmapping

Adaptive
equalization

Wavelength
dispersion /nonlinearcompensation

Received
spectrumshaping

A/D
conversion

Opticalreception
part
100G DP-QPSK
or
200G DP-16QAM

Digital coherent optical receiverFig. 3. Configuration of digital coherent optical transmitter/receiver.

(NICT).
In digital coherent optical transmission, the DSP
performs modulation/demodulation and waveform
distortion compensation. The functional configuration of the digital coherent optical transmitter/receiver used is shown in Fig. 3. We describe here an
example of transmitting/receiving a 200-Gbit/s optical signal. In the transmitter, the framer converts thetwo 100-Gbit/s Ethernet (100GbE) signals input fromthe local area network (LAN) into two optical transport network (OTN) frame formats (optical-channeltransport unit (OTU)4 signals) for the wide area network (WAN) and outputs them to the DSP. The DSP
performs soft-decision error correction [5] with aredundancy of 20% or 25%, which provides strong
error correction capability. The signals are thenmapped onto four lanes (two orthogonal phases(phases I (in-phase) and Q (quadrature)) for each of
the two orthogonal polarized waves (X- and Y-polarized waves)). After that, a pilot signal for estimating
the status of the transmission path, for example, theOSNR, is added. Digital filtering for narrowing theoptical signal spectrum is then applied. This is followed by D/A conversion. Finally, the optical transmission part converts the signals into 200-Gbit/s
DP-16QAM signals and transmits them.
In the receiver, the optical receiver element mixes
the received signal light with the local oscillation
light to apply coherent detection and converts theVol. 14 No. 9 Sept. 2016

light into four-lane analog signals as in the transmitter. The DSP converts the analog signals into digital
signals and compensates for waveform distortion due
to chromatic dispersion and optical nonlinear effects
in the optical fibers [6, 7]. It then performs adaptive
equalization, demodulation of the 16QAM signals,
and error correction decoding. Thus, two OTU4 signals are obtained. The adaptive equalization element
performs demultiplexing of the polarization-multiplexed signals and compensation for waveform distortion due to factors such as PMD. The transmission
path estimation component rapidly estimates the inband OSNR and the chromatic dispersion of thetransmission path. With this information, it selects
the optimal modulation method by using a pilot-aided
bidirectional feedback channel between the transmitter and receiver [8] and performs rapid signal recovery [1, 2]. The entire function control element controls the coordinated operations of the different
functional blocks within the DSP. The de-framer converts the two OTU4 signals into two 100GbE signals
and outputs them to the LAN. If DP-QPSK is used formodulation, the transport rate becomes 100 Gbit/s,and only one 100GbE signal is handled.

4Feature Articles

Real-time optical transmitter/receiver

Pilot sequence (PS) for OSNR estimation
PS spectrum
Transmitted signal
PS• Bit error rate (Pre-FEC and Post-FEC), OSNR, constellation monitoring• Modulation/demodulation format control

Data

Control PC
Noise

-S

-S

S

S

f

4-laneIn-band Out-of-band

S: arbitrary complex number

16QAM

Pol.-MUX
I-Q Mod.

LD

72 km
19.6 dB

Superchannel λ2n-1(200G/400G)

I-ch
λ-MUX

…

C-band 56 ch
75-GHz spacing

QPSK

Even ch.
LD

ReceiverSignal processing

Pol.-MUX

4-lane4-laneOptical
Opticalfront-end
front-end

4-lane Real-time DSP

PDM
I-Q Mod.

Odd ch.
Constellations(Back-to-back)Transmitter
Signal processing

Superchannel(200G/400G)

SEL

λ2n

WSS
(Node #1)

WSS
(Node #3)

WSS
(Node #2)

Q-ch
36 km
10.3 dB

72 km
19.5 dB

EQ

JGN-X
36 km
10.5 dB Field-installed
216-km SSMF
incl. 120-km aerial
section

101 km19.0 dB (avg.)
3030-km SSMF
in lab.
x 30 (Straight line)
EQ every 4th span

FEC: forward error correction
PDM: polarization division multiplexing
SEL: selector
WSS: wavelength selective switch

Fig. 4. 400-Gbit/s/ch real-time field trial setup.

4. 400-Gbit/s/ch real-time fieldtransmission experiment
A 400-Gbit/s/ch real-time adaptive modulation/
demodulation experiment [9, 10] conducted using areal-time DSP and the Japan Gigabit NetworkeXtreme (JGN-X) testbed is described below. The
configuration of the field experiment system used isshown in Fig. 4. The system consisted of three photonic nodes (#1, 2, and 3). The nodes were interconnected by two types of fiber cable: a JGN-X fieldinstalled testbed fiber cable (216-km single-mode
fiber (SMF)) and a laboratory fiber (3030-km SMF).
The JGN-X field-installed fiber was made up offibers that were looped between the NICT Koganei
headquarters and the TOKAI Chofu Repeater Station.
The cable length was 18 km including a 10-km aerial
section. Twelve fiber cores were used for the 216-km
transmission line, with a 120-km aerial section. A
gain equalizer (EQ) was inserted mid-span of the
216-km field fiber.
The transmission fiber in the laboratory consistedof 30 spans of 101-km standard SMF (SSMF) on abobbin. Gain EQs were inserted at every fourth span
5(404 km). The even and odd channels of a continuous
oscillation light from a laser diode (LD) light sourcethat had been wavelength-division multiplexed with
C-band 75-GHz spacing were modulated separately,and polarization-multiplexed signals were generated
by a self-delayed polarization multiplexer (Pol.MUX). They were then optically multiplexed by
Node #1 to generate either DP-16QAM signals or
DP-QPSK signals with 112 wavelengths (ranging
from 1529.114 nm to 1562.283 nm) at C-band 37.5GHz spacing as background WDM signals.
Two real-time optical transmitters/receivers wereprepared in order to generate super-channel signals,
for example, 400-Gbit/s-2subcarrier (SC)-DP16QAM and 200-Gbits/s-2SC-DP-QPSK signals.
The real-time optical transmitter/receiver used
Nyquist filtering to narrow the optical signal spectrum so that 400-Gbit/s or 200-Gbit/s super-channels
with two wavelengths placed close to each other
could be built. Node #1 replaced the two wavelengths(λ2n-1 and λ2n) of the background WDM signal withtwo different wavelengths from two real-time DSPbased transmitters. The real-time transmitter/receiver
had a function for estimating the OSNR using a pilot
NTT Technical Review

Power(10 dB/div.)

Real-time channel
400-Gbit/s-2SC-DP-16QAM
λ2n−1

λ2n

1549.8 1550.3 1550.8
Wavelength (nm)Power (10 dB/div.)

Feature Articles

After 216-km field fiber transmission
22.4-Tbit/s WDM (56 ch x 400 Gbit/s)

1525 1530 1535 1540 1545 1550 1555 1560 1565
Wavelength (nm)

8

20

6
4
2
0

15
22.4-Tbit/s, 216-km transmission(56 ch x 400 Gbit/s-2SC-DP-16QAM)

1530

1540
1550
1560
Wavelength (nm)(b) Pre-FEC Q and estimated OSNR after
400-Gbit/s/ch transmission

10

12
10

25

11.2-Tbit/s, 3246-km transmission(56 ch x 200 Gbit/s-2SC-DP-QPSK)

8

20

6
4

15

2
0

1530

1540
1550
Wavelength (nm)

1560

10

Estimated OSNR (dB)25

10Pre-FEC Q (dB)

Pre-FEC Q (dB)

12

Estimated OSNR (dB)(a) WDM spectrum after transmission over 216 km(c) Pre-FEC Q and estimated OSNR after
200-Gbit/s/ch transmission

Fig. 5. Results of 400-Gbit/s/ch real-time field trial.

signal [8]. This allowed adaptive modulation/demodulation. Namely, the OSNR of the received opticalsignal, which varied depending on the transmission
distance, was estimated and used to select the appropriate modulation/demodulation scheme. In thisexperiment, adaptive modulation/demodulationtransmission was carried out using an optical switch
within Node #2 to change the transmission distance.
Some results of an experiment with a 112-wavelength WDM signal having a total capacity of 22.4
Tbit/s are presented in Fig. 5. In this experiment, an
OSNR of 20 dB was used as the threshold for determining whether DP-16QAM transmission was possible. After transmission over 216 km, the estimated
OSNR was greater than the 20-dB threshold, indicating that DP-16QAM transmission was possible. The
measured Q value before error correction of all thechannels was about 6 dB, and we confirmed that thesignals were free of errors after error correction. Aftertransmission over 3246 km, the estimated OSNR wasless than 20 dB. Therefore, DP-QPSK was selected
instead. In this case, the Q value before error correction was also greater than 6 dB, and we also confirmed that the signals were error-free after error
correction. This experiment verified that adaptive
modulation/demodulation using an estimated OSNR
is possible.

5. Conclusion
This article has described the latest trend in beyond
100G digital coherent optical transmission technology, which is the critical technology for building ahigh-capacity optical communication network thatwill provide a foundation for the coming full-fledged
big data society. We will continue our R&D toenhance the performance and expand the application
area of this technology.
Acknowledgments
This work is partly supported by the R&D projecton “Research and Development of Ultra-high-speed
and Low-power-consumption Optical Network Technologies” of the MIC of Japan and the R&D projecton “Research and Development of Optical Transparent Transmission Technology (Lambda Reach)” of
NICT. We sincerely thank all concerned parties
involved in the projects.
References
[1]

[2]

Vol. 14 No. 9 Sept. 2016

S. Suzuki, Y. Miyamoto, M. Tomizawa, T. Sakano, K. Murata, S.
Mino, A. Shibayama, M. Shibutani, K. Fukuchi, H. Onaka, T. Hoshida, K. Komaki, T. Mizuochi, K. Kubo, Y. Miyata, and Y. Kamio,“R&D on the Digital Coherent Signal Processing Technology forLarge-capacity Optical Communication Networks,” The Journal of
IEICE, Vol. 95, No. 12, pp. 1100–1116, 2012 (in Japanese).
E. Yamazaki, S. Yamanaka, Y. Kisaka, T. Nakagawa, K. Murata, E.

6

Feature Articles

[3]

[4]

[5]

[6]

Yoshida, T. Sakano, M. Tomizawa, Y. Miyamoto, S. Matsuoka, J.
Matsui, A. Shibayama, J. Abe, Y. Nakamura, H. Noguchi, K. Fukuchi,
H. Onaka, K. Fukumitsu, K. Komaki, O. Takeuchi, Y. Sakamoto, H.
Nakashima, T. Mizuochi, K. Kubo, Y. Miyata, H. Nishimoto, S.
Hirano, and K. Onohara, “Fast Optical Channel Recovery in Field
Demonstration of 100-Gbit/s Ethernet over OTN Using Real-time
DSP,” Opt. Express, Vol. 19, No. 14, pp. 13179–13184, 2011.
K. Yonenaga, “400Gbps-class High-speed and Power Efficient Digital-coherent Optical Transmission Technologies,” Proc. of the 2014
IEICE Society Conference, C-3-1, Tokushima, Japan, Sept. 2014 (inJapanese).
K. Yonenaga, H. Onaka, A. Maruta, T. Sugihara, A. Tajima, K. Sato,and S. Suzuki, “Research and Development on Photonic Transparent
Transmission Technologies (λ-Reach Project)—Expanding Transmission Area with Dynamic Adaptive Modulation and Equalization
Techniques,” IEICE Tech. Rep., Vol. 111, No. 411, OCS2011-110, pp.
29–34, 2012 (in Japanese).
K. Sugihara, Y. Miyata, T. Sugihara, K. Kubo, H. Yoshida, W. Matsumoto, and T. Mizuochi, “A Spatially-coupled Type LDPC Code withan NGC of 12 dB for Optical Transmission Beyond 100 Gb/s,” Proc.
of the Optical Fiber Communication Conference and Exhibition/
National Fiber Optic Engineers Conference (OFC/NFOEC) 2013,
OM2B.4, Anaheim, CA, USA, Mar. 2013.
E. Noguchi, J. Abe, W. Maeda, and K. Fukuchi, “Signal Bandwidth

Yoshiaki Kisaka

Senior Research Engineer, NTT Network Innovation Laboratories.
He received a B.E. and M.E. in physics from
Ritsumeikan University, Kyoto, in 1996 and1998. In 1998, he joined NTT Optical Network
Systems Laboratories, where he engaged in R&D
on high-speed optical communication systems
including 40-Gbit/s/ch WDM transmission systems and an OTN mapping/multiplexing scheme.
He was with NTT Electronics Technology Corporation between 2007 and 2010, where heengaged in the planning and product development of a 40/100-Gbit/s OTN framer LSI. Since
2010, he has been with NTT Network Innovation
Labs, where he has been researching and developing a high-speed and high-capacity opticaltransport network using digital coherent technologies based on 100-Gbit/s channels andbeyond. He received the Young Engineer’s Award
from the Institute of Electronics, Information andCommunication Engineers (IEICE) in 2001. He
is a member of IEICE.

Masahito Tomizawa

Executive Research Engineer, Senior Manager,
Photonic Transport Network Laboratory, NTT
Network Innovation Laboratories.
He received an M.S. and Ph.D. in applied physics from Waseda University, Tokyo, in 1992 and2000. From 2003 to 2004, he was a visiting scientist at Massachusetts Institute of Technology,
USA. He has been engaged in R&D of highspeed optical transmission systems. Since 2009,he has been a project leader of the 100G Centerof-Excellence (CoE) Consortium consisting ofseveral manufacturing companies and is responsible for the development and marketing strategies of 100G coherent DSPs. In 2013, hereceived the President’s Award of the Ministry ofInternal Affairs and Communications of Japan
from the Telecommunication Technology Committee for his contributions and leadership of theconsortium in the 100G digital coherent CoE
project. In 2015 and 2016, he received Fellowgrade memberships from IEICE and the OpticalSociety of America, respectively.

7

Optimization by Adaptive Controlled Frequency-domain Equalizer
based on Spectrum Monitoring,” Proc. of the 2014 IEICE General
Conference, B-10-44, Niigata, Japan, Mar. 2014 (in Japanese).
[7] T. Hoshida, L. Dou, W. Yan, L. Li, Z. Tao, S. Oda, H. Nakashima, C.
Ohshima, T. Oyama, and J. C. Rasmussen, “Advanced and Feasible
Signal Processing Algorithm for Nonlinear Mitigation,” Proc. of
OFC/NFOEC 2013, OTh3C.3, Anaheim, CA, USA, Mar. 2013.
[8] S. Okamoto, K. Yonenaga, F. Hamaoka, and Y. Kisaka, “Field Experiment of OSNR-aware Adaptive Optical Transmission with Pilot-aided
Bidirectional Feedback Channel,” Proc. of OFC 2016, Th2A.2, Anaheim, CA, USA, Mar. 2016.
[9] K. Yonenaga, M. Teshima, T. Hoshida, Y. Akiyama, T. Sugihara, S.
Kametani, H. Noguchi, S. Yanagimachi, K. Sato, A. Maruta, and Y.
Miyamoto, “400Gbps/ch Realtime Field Trial with Scalable Photonic
Nodes in JGN-X Testbed,” Proc. of the 2016 IEICE General Conference, B-10-66, Fukuoka, Japan, Mar. 2016 (in Japanese).
[10] K. Yonenaga, K. Horikoshi, S. Okamoto, M. Yoshida, Y. Miyamoto,
M. Tomizawa, T. Okamoto, H. Noguchi, J. Abe, J. Matsui, H.
Nakashima, Y. Akiyama, T. Hoshida, H. Onaka, K. Sugihara, S. Kametani, K. Kubo, and T. Sugihara, “Field Demonstration of Modulation
Format Adaptation Based on Pilot-aided OSNR Estimation Using
400Gbps/ch Real-time DSP,” Proc. of OECC 2016 (21st Optoelectronics and Communications Conference), TuB2-2, Niigata, Japan,
July 2016.

Yutaka Miyamoto

Senior Distinguished Researcher, Director,
Innovative Photonic Network Research Center,
NTT Network Innovation Laboratories.
He received a B.E. and M.E. in electrical engineering from Waseda University, Tokyo, in 1986
and 1988. In 1988, he joined NTT Transmission
Systems Laboratories, where he engaged in R&D
of high-speed optical communications systems
including the first 10-Gbit/s terrestrial opticaltransmission system (FA-10G) using EDFA
(erbium-doped optical fiber amplifier) inline
repeaters. He was with NTT Electronics Technology Corporation between 1995 and 1997,
where he engaged in the planning and productdevelopment of high-speed optical modules atdata rates of 10 Gbit/s and beyond. Since 1997,
he has been with NTT Network Innovation Labs,
where he has been researching and developing
optical transport technologies based on
40/100/400-Gbit/s channels and beyond. He has
been investigating and promoting the scalable
OTN with the Pbit/s-class capacity based on
innovative transport technologies such as digital
signal processing, space division multiplexing,
and cutting-edge integrated devices for photonic
pre-processing. He currently serves as Chair of
the IEICE technical committee of Extremely
Advanced Optical Transmission (EXAT). He hasa Dr. Eng. degree, and is a member of IEEE anda Fellow of IEICE.

NTT Technical Review

Feature Articles: Device Technology Development for
Beyond 100G Optical Transport Network

Compact Optical Modulator andCoherent Optical Subassemblies for
Beyond 100G Transport Network
Norihide Kashio and Yusuke Nasu
Abstract

This article presents an indium-phosphide-based optical modulator and a silicon-photonics-based
coherent optical subassembly. Both devices enable compact and low-power beyond 100G (beyond 100
Gbit/s per wavelength) digital coherent transceivers that are essential for constructing an optical transport network economically.
Keywords: coherent transceiver, InP, silicon photonics

1. Introduction
Steady progress has been made in the last few
decades in expanding the transmission capacity of
optical transport networks [1]. Recently, digital
coherent technology with advanced modulation formats was proposed, which can significantly increase
the transmission capacity of optical transport networks by incorporating ultrahigh-speed digital signal
processing [2]. A commercial service employing
100-Gbit/s dual-polarization quadrature phase-shift
keying (QPSK) systems is already in operation.
Transceivers for the digital coherent technology needvarious components in order to support complicatedmodulation formats.
However, there is strong demand for small-form
factor pluggable digital coherent transceivers in order
to expand their application space from long-haul networks to cost-sensitive metro areas and datacenterinterconnections. The specifications of digital coherent transceivers such as power consumption and size
are standardized at the Optical Internetworking
Forum (OIF), where service providers, equipmentvendors, and component vendors cooperatively
develop implementation agreements (IAs) for optical
networking products.
The evolution of digital coherent transceivers, discussed at OIF, is shown in Fig. 1. The IA on the first1

generation digital coherent transceivers, which were
5 × 7 inches (in) in size, was issued in 2011. Since
then, the size and power consumption of these transceivers have been continuously reduced. At the second generation, the size was reduced to 4 × 5 in, andthe latest IA at the OIF was for a centum (100) gigabit
form-factor pluggable 2 - analogue coherent optics(CFP2-ACO) with a size of 1.6 × 4.2 in. Such compact transceivers facilitate high-density and lowpower optical network equipment for metro networks
and datacenter interconnects. Another aspect inregard to the evolution of the transceiver is the speed.
If the transceiver can support beyond 100 Gbit/s per
wavelength (beyond 100G) speed with the same form
factor as 100 Gbit/s, the size required for a transmission capacity will be substantially reduced.
In this article, we present an indium-phosphide(InP)-based optical modulator and a silicon (Si)photonics-based coherent optical subassembly(COSA). We first discuss the InP-based modulator,
which was the key component to achieve the current
generation CFP2-ACO transceiver. The InP-based
modulator can achieve high speed with a compact
size, and is promising for future very high-speedtransceivers. Then, we discuss the Si-photonicsbased COSA. The Si can integrate various kinds of
optical devices on a single chip and will help toachieve an extremely compact transceiver.
NTT Technical Review

Feature Articles

Size, power consumption

OIF Gen1 MSA
5 × 7”, 90 W

OIF Gen2 MSA
4 × 5”, 40 W

CFP
3.2 × 5.7”, 32 W

CFP2-ACO
1.6 × 4.2”, 12 W

2012

2015
Year

ACO: analog coherent optics
CFP: centum (100) gigabit form-factor pluggable” : inches
MSA: multi-source agreement

Fig. 1. Evolution of digital coherent transceivers.

Table 1. Features of InP and LN modulators.
InP

LN

Modulation length

Small (~3 mm)

Large (~3 cm)

Driving voltage

Small (1.5–2.5 V) Large (~3 V)

Modulation speed

High speed(> 45 GHz)High speed(> 35 GHz)

Thermal shift

Large

Very small

Optical loss

Moderate

Low

StabilityHigh

Low (bias shift)

2. InP-based optical modulator
NTT laboratories have developed a compact andhigh-speed InP optical modulator by making use of
the superior optical properties of InP materials [3].
Table 1 summarizes the features of an InP and lithium niobate (LiNbO3: LN) modulator. Quantum confined stark effects in an InP-based multiple quantum
well structure used in a waveguide core enable a large
phase shift per unit length. Thus, the length of thephase modulation for an InP modulator can be
reduced to as small as ~3 mm, which is one-tenth thatfor an LN modulator (~3 cm). In addition, the InP
modulator can also provide low driving voltage
Vol. 14 No. 9 Sept. 2016

(1.5–2.5 V). These features are beneficial for lowpower operation.
Furthermore, the InP modulator is free in principle
from direct current bias fluctuation under operation,
which is observed in LN modulators. A photographand the features of our InP modulator are shown in
Fig. 2. The modulator provides a driving voltage ofless than 2.5 V while significantly reducing the footprint to half that of the LN modulator. The compact
and low-power InP modulator technology makes it
possible to achieve CFP2-ACO transceivers.
Table 2 compares the size and power consumptionof the first- and second-generation optical modulators. A large portion of the power consumption in an
2

Feature Articles• Differential operation• Surface mount radio frequency interference• Driving voltage (Vπ): < 2.5 V @32 Gbaud• Extinction ratio: > 20 dB• Size: 34 × 15.6 mm (less than half that of LN modulator)

Fig. 2. Photograph and features of the developed InP modulator.

Table 2. Size and power consumption of LN and InP modulators.
Generation 1

Generation 2

Material

LN

InP

Size

13.2 × 90.5 × 7 mm

15.6 × 34 × 6.5 mm

Powerconsumption*

5.2 W

3.5 W

* Total power consumption for modulator and driver integrated circuits (ICs).
Power consumption values for each driver IC were obtained from OIF2013.239.00.

optical modulator is determined by drivers. The
power consumption of drivers for the LN and InP
modulators is 5.2 W and 2.5 W, respectively. Even
when taking into account the power consumption of athermoelectric cooler (1 W) to maintain the operating
temperature of the InP modulator, the total power
consumption of the InP modulator (3.5 W) is still 1.7
W lower than that of the LN modulator.
3. Si-photonics-based COSA
NTT laboratories have been developing a COSA
based on Si photonics technology in order to further
reduce the size of digital coherent transceivers. In
digital coherent transport systems, the digital signal
processor (DSP) not only demodulates signals but
also compensates for signal distortion in the transmission line and analog devices. The powerful abilityof DSP has opened up more choices in optical devices for the transceiver, including Si photonics, whichuses microfabrication technology for LSIs (largescale integrated circuits). Si substrates, which aretransparent to 1.5-μm-wavelength light, are used as
the platforms of photonic integration.
3

NTT laboratories started research and development
on Si photonic devices in 2000, foreseeing the potential of Si photonics [4]. Now, in addition to simple
passive devices, high-speed optical modulators andgermanium (Ge) photo detectors (PDs) can be integrated in Si substrates.
The digital coherent transceiver has an opticalmodulator and drivers at the transmitter part and an
integrated coherent receiver (ICR) at the receiver
part. The ICR consists of 90° optical hybrids, highspeed PD arrays, a dual polarization mixer, and transimpedance amplifiers (TIAs) that convert the output
current of PDs into a voltage signal. To date, these
optical devices have been fabricated with different
materials and connected with optical fibers. A function block for a COSA module is shown in Fig. 3. The
key optical components are integrated in a single chip
(Si photonics chip), and the drivers and TIAs are
implemented in a package, as shown in Fig. 4. The
subassembly eliminates the optical fibers and lenses
that are conventionally used for connection between
optical devices, resulting in an extremely small digital coherent transceiver.

NTT Technical Review

Feature Articles

Si photonics chip

Signal output

DriverPM-IQ
modulator

Local optical input
Signal input

Dual pol.
mixer

PD

TIA

IQ: in-phase and quadrature
PM: polarization multiplexed

Fig. 3. Function block of COSA module.

Flexible circuit
for electrical interface

Both devices are key components for constructing
cost-effective beyond 100G transport networks. NTT
laboratories will continue to develop the key devices
that contribute to the evolution of optical transmission networks.
References

Input/output
fiber(Size: 19 × 17 × 2.1 mm)[1]Fig. 4. Photograph of COSA module.
[2]

4. Conclusion
An InP-based optical modulator and Si-photonicsbased COSA are promising enablers for the future
generation of digital coherent transceivers. The InP
modulator is essential for future high-speed and longdistance transmission systems, and the COSA isessential for metro and datacenter interconnections.

Vol. 14 No. 9 Sept. 2016

[3]

[4]

K. Murata and T. Saida, “Optical Device Technologies for Future
Network Evolution,” NTT Technical Review, Vol. 9, No. 3, 2011.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201103fa6.html
Y. Miyamoto, A. Sano, E. Yoshida, and T. Sakano, “Ultrahigh-capacity Digital Coherent Optical Transmission Technology,” NTT Technical Review, Vol. 9, No. 8, 2011.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201108fa2.html
E. Yamada, K. Tsuzuki, N. Kikuchi, and H. Yasaka, “Compact Lowpower-consumption Optical Modulator,” NTT Technical Review, Vol.
3, No. 3, pp. 41–45, 2005.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr200503041.pdf
S. Itabashi, “R&D Trends in Silicon Photonics,” NTT Technical
Review, Vol. 8, No. 2, 2010.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201002sf1.html

4Feature Articles

Norihide Kashio

Senior Research Engineer, Photonic Network
Device Project, NTT Device Innovation Center.
He received a B. Eng., M. Eng., and Dr. Eng. inelectrical engineering from Waseda University,
Tokyo, in 2000, 2002, and 2012. He joined NTT
Photonics Laboratories in 2002, where he has
been conducting research on ultrahigh-speed
InP-based optical and electrical devices for
future optical fiber communication systems. He
is a member of the Institute of Electrical andElectronics Engineers (IEEE) and the Institute ofElectronics, Information and Communication
Engineers (IEICE).

5

Yusuke Nasu

Senior Research Engineer, Photonic Network
Device Project, NTT Device Innovation Center.
He received a B.S., M.S., and Ph.D. in electronic engineering from the University of Tokyoin 2000, 2002, and 2010. He joined NTT Photonics Laboratories in 2002, where he has been
engaged in research on silica-based planar lightwave circuits. From 2005 to 2008, he wasinvolved in developing 40-Gbit/s differential
QPSK demodulators. From 2012 to 2015, he wasan Engineering Manager at NTT Electronics
Corporation, where he developed coherent
receivers for 100-Gbit/s systems and a multicast
switch for CDC-ROADM (colorless, directionless, and contentionless reconfigurable optical
add/drop multiplexing). He is a member of
IEICE and the IEEE Photonics Society.

NTT Technical Review

Feature Articles: Device Technology Development for
Beyond 100G Optical Transport Network

High-sensitivity 4-channel Receiver
Module with Avalanche Photodiodefor 400-Gbit/s Ethernet
Yasuhiko Nakanishi, Tetsuichiro Ohno,
Toshihide Yoshimatsu, and Hiroaki Sanjoh
Abstract

We developed an integrated 4-channel receiver optical subassembly (ROSA) with high-sensitivity
avalanche photodiode (APD) for 400-Gbit/s Ethernet. A minimum receiver sensitivity of –21.2 dBmwith a 4-channel × 28-Gbaud PAM-4 (four-level pulse amplitude modulation) APD-ROSA was achieved,
enabling us to achieve 30-km transmission.
Keywords: avalanche photodiode (APD), 400-Gbit/s Ethernet, receiver optical subassembly (ROSA)

1. Introduction
Data traffic both within and between datacenters is
rapidly increasing as the demand for cloud computing, video streaming, and mobile services grows. To
cope with this demand, the Institute of Electrical andElectronics Engineers (IEEE) is currently discussing
the standardization of 400-Gbit/s Ethernet [1] as thenext-generation standard following 100-Gbit/s Ethernet. The bit rate/lane and modulation format of each
operating distance in 400-Gbit/s Ethernet using an
optical fiber are listed in Table 1. The 400-Gbit/s
Ethernet is the first to employ a higher-order modulation (HOM) format for the Ethernet optical datatransmission. The optical modulation format currently employed is non return to zero (NRZ); however, 400-Gbit/s Ethernet employs a four-level pulse
amplitude modulation (PAM-4) as a kind of HOM
format. While an NRZ signal consists of two levels (0and 1), PAM-4 consists of four levels (0, 1, 2, and 3),
as shown in Fig. 1. Therefore, the transmission of a
PAM-4 signal can achieve twice the bit rate of the
NRZ signal under the same baud rate.
The standardization of 400-Gbit/s Ethernet is basedon operating distances up to 10 km. However, thepossibility of extending the operating distance has
1been discussed to cope with the increasing capacityof inter-building links and mobile backhaul [2].
Extending the operating distance will require enlarging the power budget from transmitter to receiver.
One promising method to do this is to improve sensitivity using an avalanche photodiode (APD). Applying an APD to a receiver not only achieves a highsensitivity receiver thanks to inner gain, but also a
compact receiver thanks to its low power consumption [3].
2. Linearity of APD receiver opticalsubassembly (APD-ROSA)
In systems with the PAM-4 signal, photodiodes are
required to achieve high linearity of an output photocurrent against the optical input power. While APDs
can deliver high performance in terms of responsivity, they exhibit higher nonlinearity than p-i-n photodiodes (pin-PDs) in direct current (DC) input andoutput characteristics due to both the thermal effectand the space charge effect [4]. Consequently, inorder to employ APDs in the PAM-4 system, it isnecessary to measure the linearity of an APD receiverusing a linear-type transimpedance amplifier (TIA)
and confirm the degree of nonlinearity.
NTT Technical Review

Feature Articles

Table 1. Bit rate/lane and modulation format in 400-Gbit/s Ethernet using optical fiber.
400GBASE-SR16

400GBASE-DR4

400GBASE-FR8

400GBASE-LR8

Operatingdistance

100 m

500 m

2 km

10 km

Bit rate/lane

26.5625 Gbit/s

106.25 Gbit/s

53.125 Gbit/s

53.125 Gbit/s

Modulation
format

NRZ

PAM-4

PAM-4

PAM-4

Media

Multi-mode
fiberSingle-mode
fiberSingle-mode
fiberSingle-mode
fiber

Number oflanes andmultiplexing

16 lanes
Parallel fibers

4 lanes
Parallel fibers

8 lanesWDM

8 lanes
WDM

WDM: wavelength division multiplexing

1

0

0

1

1

0

0

0

0

Time

Optical power

Optical power

T: symbol rate 40 picoseconds

Time
T
Eye pattern (NRZ)

Waveform (25-Gbit/s NRZ)

3

2

0

1

1

0

1

3

2
1
0

Time
Waveform (50-Gbit/s PAM-4)

Optical power

Optical power

T: symbol rate 40 picoseconds

Time
T
Eye pattern (PAM-4)

Fig. 1. Comparison of optical modulation formats.

The measured output photocurrents in a pin-PD and
our APD and the calculated output photocurrent
when the APD operates with the ideal linearity areplotted in Fig. 2. As indicated by the solid red curve
and the dashed red line, the gap between the red curve
and the line increases as the input optical power isincreased. These results show that our APD has nonlinearity in DC input and output characteristics. If the
waveform of the optical PAM-4 input is converted toan electrical signal in accordance with DC input andoutput characteristics of the APD, one concern is thatthe amplitude of the upper inner-eye would become
smaller than that of the middle and lower inner-eyes,Vol. 14 No. 9 Sept. 2016

resulting in bit error rate (BER) degradation.
To evaluate the effect of DC nonlinearity on the
optical-to-electrical (O/E) conversion of PAM-4 signals, we measured the ratio of each inner-eye amplitude to the outer-eye amplitude, as shown in Fig. 3(a).
To simplify the measurements, we used an experimental baud rate of 10 Gbaud and a PAM-4 modulation format. The measurement results are shown in
Fig. 3(b). The solid curves are the ratios calculated
from the DC input and output characteristics of the
APD. In the calculation, the extinction ratio (ER) of
the outer-eye is assumed to be 4.8 dB. The calculated
values deviate by 9% from 33% for the average
2

Feature Articles

Output current (mA)10

Calculated output photocurrent of APD
when APD operates with ideal linearity

1
Measured output
photocurrent of APD

0.1
Measured output photocurrentof pin-PD

0.01
−20

−18

−16

−14

−12

−10

−8

−6

−4

−2

0

Input optical power (dBm)

Fig. 2. DC input and output characteristics of pin-PD and APD.

3
Outer-eyeUpper inner-eye

2

Middle inner-eye

1

Lower inner-eye
0
Eye pattern (PAM-4)(a) Inner-eye and outer-eye patterns of PAM-4 signal.

Ratio of outer-eye toinner-eye amplitude (%)

50
40
33
30
20
10

Measurement
Upper
MiddleLower

Calculation
Upper
MiddleLower

0−20 −18 −16 −14 −12 −10 −8 −6 −4 −2
Input optical power (dBm)0(b) Ratio of outer-eye to each inner-eye amplitudeFig. 3. Linearity of APD-ROSA.

received power of 0 dBm due to the DC nonlinearity.
In contrast, the measured ratios stay at 33%, which iswithin the range of measurement error, regardless of
the received optical power. These results indicate that
the O/E conversion of PAM-4 signals does not seemto be affected by DC nonlinearity for average received
powers up to –2 dBm.
3

3. APD-ROSA for 400-Gbit/s Ethernet systems
A photograph and schematic view of a 4-channel
APD-ROSA, which can receive 200-Gbit/s (4-channel × 28 Gbaud × PAM-4) signals are shown in Fig. 4.
The APD-ROSA consists of a planar lightwave circuit demultiplexer (PLC-demux), a quad-channel
NTT Technical Review

Feature Articles

W
H

W = 6.7 mm
L = 17.5 mm
H = 5.8 mm

L

PLC-demux

Quad-channel APD array

4-channel linear-type
TIA array

LC receptacle
FPCs
Lens

Multi-mode waveguides Micro-lens array

Fig. 4. Photograph and schematic view of 4-channel APD-ROSA.

APD array, and a linear-type TIA array. An LC receptacle and flexible printed circuits (FPCs) are respectively attached to the optical wavelength-divisionmultiplexing (WDM) input and electronical output.
The optical coupling between the PLC-demux and
APD array employs a low-loss technique using boththe multi-mode waveguide and micro-lens arraydeveloped for a 100-Gbit/s Ethernet ROSA [5]. The
input 4-wavelength × 28-Gbaud PAM-4 optical signal is demultiplexed into four wavelengths in the
PLC-demux. In the quad-channel APD array, theoptical signals are converted to electrical signals andfed into the linear-type TIA array. Then, amplified 4
× 28-Gbaud PAM-4 signals are output from the linear-type TIA array. The package size is as small as
17.5 × 6.7 × 5.8 mm in order to install two modules
in a CFP8 (centum (100) gigabit form-factor pluggable 8) [6] transceiver (107.5 × 40 × 9.5 mm) for
400-Gbit/s operation. The total power consumptionof the APD-ROSA is as low as 860 mW at room temperature.
The performance of the 4-channel APD-ROSA in
receiving PAM-4 signals was investigated in a backto-back configuration. The experimental setup is
shown in Fig. 5. The input optical signal from a tunable laser source was modulated using a lithium niobate Mach-Zehnder modulator with a 28-Gbaud
PAM-4 signal of a 215-1 pseudo random bit sequence(PRBS). The wavelengths for lanes 0, 1, 2, and 3 wererespectively set at 1295.56, 1300.05, 1304.58, and1309.14 nm. The ER of the outer-eye for lanes 0, 1, 2,
and 3 was 5.6, 6.4, 6.0, and 6.8 dB, respectively. The
PAM-4 signal was received and converted to the electrical signal by the APD-ROSA and then input into a
digital storage oscilloscope with 33-GHz analog
Vol. 14 No. 9 Sept. 2016

bandwidth and a sample rate of 80 GSample/sec. We
demodulated the stored signal by offline digital signal
processing, in which we used a half-symbol-spaced
adaptive equalizer with 17 taps. A variable opticalattenuator was inserted before the APD-ROSA tochange the input power.
The BER measurement results for single-channel
operation of each lane are shown in Fig. 6. We
observed a minimum receiver sensitivity better than
–21.2 dBm in optical modulation amplitude (OMA)of the inner-eye for all channels at a BER of 2e-4,
assuming the Reed-Solomon forward error correction(544, 514) defined in 100GBASE-KP4 (IEEE802.3bj) [7]. The symbols plotted on 1e-6 show thatno bit error is observed within the stored data length.
This minimum receiver sensitivity has a margin of
9.3 dB for the sensitivity (–11.9 dBm) required in
400GBASE-LR8. This margin would enable
400-Gbit/s transmission with an extended operating
distance up to 30 km, assuming a 0.4-dB/km loss of
single-mode fiber.
4. Conclusion
We developed a 4-channel APD-ROSA as a key
component to achieve 400-Gbit/s Ethernet. The APDROSA is integrated using a quad-channel APD array,
PLC-demux, and linear-type TIA. We investigatedthe linearity of the APD-ROSA for PAM-4 signals
and confirmed that three inner-eye amplitudes of theoutput waveform were kept equal up to –2 dBm. We
also successfully demonstrated 28-Gbaud operation
with a minimum receiver sensitivity of –21.2 dBm or
below for PAM-4 signals. This result indicates thatwith an assumed 0.4-dB/km loss of a single-mode
4

Feature Articles

28-Gbaud PAM-4
optical waveform
ER: 5.8–6.8 dB

Lane 0: 1295.56 nm
Lane 1: 1300.05 nm
Lane 2: 1304.58 nm
Lane 3: 1309.14 nm
Tunable laser source

Pulse
pattern
generator

LN modulator

6-dB ATT
Variable opticalattenuator

28-Gbaud
PRBS 215-1

DigitalstorageoscilloscopePC(offline
processing)

4-channel
APD-ROSA

ATT: attenuator
LN: lithium niobate
PC: personal computer

Fig. 5. Experimental setup.

1e-128-Gbaud PAM-4
PRBS: 215-1
Vapd: 25 V
Taps: 171e-2Lane 0Lane 1
Lane 2
Lane 3

BER

Receiver sensitivity of
400GBASE-LR8 (–11.9 dBm)

1e-3

9.3 dB

1e-4
KP4 FEC limit (2e-4)

1e-5
1e-6
1e-7
–25

–21.2 dBm
–20

–15
Inner-eye OMA (dBm)

–10

–6

Vapd: APD bias voltage

Fig. 6. BER of 4-channel APD-ROSA.

fiber, the APD-ROSA is a promising device toachieve 400-Gbit/s data transmission up to 30 km or
longer.

5

References[1]

Website of IEEE standard 802.3bs Ethernet Task Force,
http://www.ieee802.org/3/bs/

NTT Technical Review

Feature Articles

[2]
[3]

[4]

Website of IEEE 802.3 industry connections NG-ECDC ad hoc group,
http://www.ieee802.org/3/ad_hoc/ngrates/
F. Nakajima, M. Nada, and T. Yoshimatsu, “High-sensitivity Avalanche Photodiode and Receiver Optical Subassembly Technology for
100-Gbit/s Ethernet,” NTT Technical Review, Vol. 13, No. 10, 2015.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201510ra1.html
W. Sun, Y. Fu, Z. Lu, and J. Campbell, “Study of Bandwidth Enhancement and Non-linearity Behavior in Avalanche Photodiodes underHigh Power Condition,” J. Appl. Phys., Vol. 113, No. 4, 044509, 2013.

Yasuhiko Nakanishi

[5]

[6]
[7]

Y. Doi, M. Oguma, M. Ito, I. Ogawa, T. Yoshimatsu, T. Ohno, E.
Yoshida, and H. Takahashi, “Compact ROSA for 100-Gb/s (4 x 25
Gb/s) Ethernet with a PLC-based AWG Demultiplexer,” Proc. of Optical Fiber Communication Conference 2013, NW1J.5, Anaheim, CA,
USA, Mar. 2013.
400G CFP8 Form Factor Proposal, 2015.
http://www.cfp-msa.org/Documents/400g_CFP_MSA_proposal.pdf
IEEE P802.3bj 100 Gb/s Backplane and Copper Cable Task Force,
http://www.ieee802.org/3/bj/

Toshihide Yoshimatsu

Senior Research Engineer, Optical SubAssembly Module Development Project, NTT
Device Innovation Center.
He received a B.E. and M.E. from Hokkaido
University in 2000 and 2002. He joined NTT
Access Network Service Systems Laboratories in
2002, where he has been involved in research anddevelopment of optoelectronics devices for optical communication systems. He is currently with
the NTT Device Innovation Center. He is a member of the Institute of Electronics, Information
and Communication Engineers (IEICE).

Senior Research Engineer, Optical SubAssembly Module Development Project, NTT
Device Innovation Center.
He received his B.E. and M.E. in applied physics from Tohoku University, Miyagi, in 1998 and2000. He joined NTT Photonics Laboratories in
2000. He has been researching and developing
ultrafast optoelectronics devices. He received the
SSDM Paper Award from the SSDM (Solid State
Devices and Materials) Organizing Committee in
2004. He is a member of IEICE and the Japan
Society of Applied Physics.

Tetsuichiro Ohno

Hiroaki Sanjoh

Senior Research Engineer, Optical SubAssembly Module Development Project, NTT
Device Innovation Center.
He received a B.E. in 1989 and M.E. in 1991
from Osaka University, and a Ph.D. in 1999 from
Shizuoka University. In 1991, he joined NTT
Optoelectronics Laboratories and has been
researching optoelectronics devices. He is currently with the NTT Device Innovation Center.
He is a member of the IEEE Lasers and ElectroOptics Society.

Vol. 14 No. 9 Sept. 2016

Group Leader, Optical Sub-Assembly Module
Development Project, NTT Device Innovation
Center.
He received a B.E. and M.E. in applied physics
from Hokkaido University in 1990 and 1992. He
joined NTT Optoelectronics Laboratories in1992. He is currently with the NTT Device Innovation Center, where he is conducting developmental research on optical semiconductor devices.

6

Feature Articles: Device Technology Development for
Beyond 100G Optical Transport Network

High Frequency Optical Module
Assembly Technique Enabling High
Modulation Speed over 100 Gbit/s/λSatoshi Tsunashima, Shigeru Kanazawa,and Hiromasa Tanobe
Abstract

A novel optical module assembly technique enabling high modulation bandwidth is described. This
optical module features not only high modulation bandwidth but also a small footprint and low-power
dissipation. These features help accelerate optical module development for 400-Gigabit Ethernet applications.
Keywords: 100 Gbit/s/λ, high modulation bandwidth, flip-chip interconnection

1. Introduction
In response to the urgent demand for expanded network bandwidth for mobile and cloud computing
networks, the standardization of high transmission
bandwidth is being actively discussed. In Ethernet
standardization, the Institute of Electrical and Electronic Engineers (IEEE) standard 802.3ba [1] wasadopted as the standard for 100-Gigabit Ethernet(100GbE) in 2010 (Fig. 1). The IEEE 802.3ba standards define that wavelength-division multiplexing(WDM) transmission technology be utilized to establish 100GbE optical links for 10-km and 40-km single-mode fiber (SMF) transmission. In WDM transmission, four 25-Gbit/s optical data signals with different wavelengths are launched on SMFs and travel
along the SMFs. This transmission scheme is called
multi-lane transmission.
In 2013, the IEEE 802.3bs [2] task force started
discussions on 400-Gigabit Ethernet (400GbE) standards to cover the emerging shortage of bandwidth
capacity in 100GbE based networks. The 400GbE
transmission uses a multi-lane transmission schemewith a newly introduced signal modulation technology called four-level pulse amplitude modulation(PAM-4)*1. Eight 50-Gbit/s PAM-4 optical signals
1

×8

×4

400GbE

Downsize

100GbE
×4

25

Downsize
×1

50

100

Transmission speed per wavelength (Gbit/s)

Fig. 1. Ethernet standardization trends.

with different wavelengths establish a 400GbE fiber
optic link with the multi-lane scheme.
In the optical transceiver marketplace, some manufacturers launched their 400GbE transceiver products,*1 PAM: A form of pulse modulation. By making the amplitude direction multilevel, we can increase the amount of information per
modulation. At level four modulation, it is PAM-4: log2 4 = 2bit.

NTT Technical Review

Feature Articles

Subcarrier

Subcarrier

Top view

Top view
RF substrate

RF substrate

Terminator

EA-DFB laser

WireSide view

Terminator

Au bump

Side view

RF substrate

EA-DFB laser

RF substrate

Subcarrier(a) Wire interconnection

Flip-chip bonding
substrate

Subcarrier(b) Flip-chip interconnection

Fig. 2. Schematic structure of wire and flip-chip interconnections.

known as CFP8 (centum (100) gigabit form-factor
pluggable 8) [3], before the IEEE 802.3bs task force
had finalized the 400GbE standards. This CFP8transceiver typically has four optical assemblies consisting of two transmitter optical subassemblies(TOSA) and two receiver optical subassemblies(ROSA). Each assembly of TOSA and ROSA runs at
200 Gbit/s with four wavelengths and transmits andreceives 50-Gbit/s optical signals per wavelength.
There are various requirements for cost reduction anddownsizing of the CFP8 400GbE optical transceivers
arising from an issue involving the use of four opticalassemblies. This has made establishing opticalassemblies based on serial 100-Gbit/s with one lambda (λ: wavelength) transmission an urgent priority for
future 400GbE fiber optic networks.
A new assembly technique developed by the NTT
Device Innovation Center can establish a high modulation bandwidth in each wavelength by improving
the high-speed electromagnetic characteristics in an
optical module with a novel flip-chip interconnection*2 technique. With this new technique, each wavelength transmits an optical signal at 100 Gbit/s (100Gbit/s/λ), thus enabling 400GbE to be attained. This
new assembly technique is explained in detail in thefollowing sections.

Vol. 14 No. 9 Sept. 2016

2. 100 Gbit/s/λ-high frequency
assembly technique
The serial 100 Gbit/s optical signal transmission isa key technology for future Ethernet networks. By
using four wavelengths at 100 Gbit/s, the 400GbE
transmission can be established. A flat and wideband
frequency response for the serial 100-Gbit/s opticalmodule is essential in order to obtain multi-level
modulation (PAM-4) and a high-speed symbol rate
(50 Gbaud) in the serial 100-Gbit/s optical signaltransmission. However, conventional optical transmitter modules cannot extend the modulation bandwidth beyond 50 Gbit/s at high-speed transmission
such as 50-Gbit/s operation. The schematic structureof a wire interconnection in the conventional opticaltransmitter module is shown in Fig. 2(a). The radio
frequency (RF) signal is transmitted from an RF substrate through a wire to an electroabsorption modulator (EAM) integrated with a distributed feedback
laser (EAM-DFB laser, or EA-DFB laser). Due to thenature of the characteristics in wire inductance, themodulation bandwidth degrades rapidly with a longer
wire.
*2 Flip-chip interconnection: A chip interconnection technique.
Generally, by forming small protruding metallic terminals aselectrodes of chips, the chips can be placed and connected on to
the face of the substrates. This helps to reduce the assembly footprint compared to conventional metal wire interconnection techniques.

2Feature Articles

3

More than 10-GHz bandwidth
improvement

3

Power (dB)To resolve this issue, we propose using a flip-chip
interconnection technique as a wire-free interconnection. The schematic structure of the flip-chip interconnection is shown in Fig. 2(b). A flip-chip bonding
substrate is connected to an RF substrate and an EAM
with gold (Au) bumps. The height of the Au bumps is
as small as just a few micrometers (~10 µm). To
eliminate wire connections between the EAM and aterminator, a terminator resistance thin film is integrated on the flip-chip bonding substrate. The flipchip interconnection reduces the parasitic inductancesince the wire is no longer necessary. Therefore, theflip-chip interconnection improves the frequency
response of the module, as shown in Fig. 3.
Eye diagrams of 56-Gbaud PAM-4 (112 Gbit/s)
signals obtained under the configuration of a back-toback transmission and after 10-km SMF transmission
using the flip-chip interconnection EA-DFB laser
module are shown in Fig. 4. Clear eye opening characteristics with four levels (0, 1, 2, 3) are observed
even after 10-km SMF transmission thanks to thehigh modulation bandwidth and the flat frequency
response of the module.
Generally, the digital signal processing circuits are
introduced to high-speed optical communication systems using a multi-level modulation format in order
to compensate for the bandwidth degradation occurring in the optical modules. However, those digital
signal processing circuits use a lot of electric power,
which creates additional latency on the transmission
link, so it is desirable to reduce the number of digital
signal processing circuits for future Ethernet networks.
The bit error rate (BER) characteristics are shownin Fig. 5 for back-to-back configuration and 10-km
SMF transmission without any digital signal processing such as BCH (Bose-Chaudhuri-Hocquenghem)forward error correction (FEC). The BER of less than1 × 10−3, which is the error-free condition for the
BCH FEC, was obtained even after 10-km SMF
transmission. Our optical module has a sufficiently
high modulation bandwidth and flat frequency
response to make the digital signal processing unnecessary [4]. The module enables us to construct lowpower consumption and low-latency networks thanks
to the elimination of the digital signal processing
circuits. Moreover, this optical module helps reduce
the number of wavelengths from eight to four so that
we can establish 400GbE transmission.
Moreover, if digital signal processing is utilized tocompensate for the bandwidth degradation in an optical transmission link while using our optical module,

0−3
Flip-chip interconnection
Wire connection
−6
0

10

20

30

40

50

60

Frequency (GHz)

Fig. 3. F requency response of wire and flip-chip
interconnections.

Level 0Level 1
Level 2
Level 3Extinction ratio: 7.57 dB(a) Back-to-back configuration
Level 0Level 1
Level 2
Level 3Extinction ratio: 7.65 dB(b) After 10-km transmission

Fig. 4. Eye diagrams under 56-Gbaud PAM-4 operation.

dramatic improvements in transmission bandwidth
can be expected. In our experimental work, we demonstrated 200-Gbit/s per wavelength operation [5].
By applying this technique in 100-Gbit/s per wavelength operation, the digital signal processing as a
bandwidth degradation compensator becomes unnecessary, which thus reduces power consumption.
3. Future plans
The proposed assembly technique makes it possible
to achieve a smaller optical module with lower-power
consumption. We plan to create a flip-chip interconnection 4ch optical transmitter module integrated
with an optical multiplexer for 400GbE transmission.

NTT Technical Review

Feature Articles

56-Gbaud PAM-4 (112 Gbit/s)

1E-1

BER

Back-to-back configuration
After 10-km transmission
1E-2

BCH code
FEC limit

1E-3
1E-4
1E-5

0

2

4

6

8

Averaged receiver power (dBm)

Fig. 5. BER characteristics under 56-Gbaud PAM-4 operation.

References
[1]
[2]
[3]
[4]

Website of IEEE standard 802.3ba Ethernet Task Force,
http://www.ieee802.org/3/ba/
Website of IEEE standard 802.3bs Ethernet Task Force,
http://www.ieee802.org/3/bs/
Website of the CFP Multi-Source Agreement, Documents,
http://www.cfp-msa.org/documents.html
S. Kanazawa, T. Fujisawa, K. Takahata, Y. Nakanishi, H. Yamazaki, Y.

Satoshi Tsunashima

Senior Research Engineer, Metro Access Network Device Project, NTT Device Innovation
Center.
He received a B.S. and M.S. in electrical engineering from Toin University of Yokohama,
Kanagawa, in 1996 and 1998. In 1998, he joined
NTT Optical System Laboratories and engaged
in research on high-speed circuit design for optical communication systems. He joined NTT
Photonics Laboratories in 2000, where he has
been conducting research on optical subsystems
and assembly and packaging technologies fortheir optical modules. He is a member of theInstitute of Electrical and Electronics Engineers(IEEE) and the Institute of Electronics, Information and Communication Engineers (IEICE).

[5]

Ueda, W. Kobayashi, Y. Muramoto, H. Ishii, and H. Sanjoh, “56Gbaud 4-PAM (112-Gbit/s) Operation of Flip-chip Interconnection
Lumped-electrode EADFB Laser Module for Equalizer-free Transmission,” Proc. of the Optical Fiber Communication Conference andExhibition (OFC) 2016, W4J.1, Anaheim, CA, USA, Mar. 2016.
S. Kanazawa, H. Yamazaki, Y. Nakanishi, T. Fujisawa, K. Takahata, Y.
Ueda, W. Kobayashi, Y. Muramoto, H. Ishii, and H. Sanjoh, “Transmission of 214-Gbit/s 4-PAM Signal Using an Ultrabroadband
Lumped-electrode EADFB Laser Module,” Proc. of OFC 2016,
Th5B.3, Anaheim, CA, USA, Mar. 2016.

Hiromasa Tanobe

Senior Research Engineer, Metro Access Network Device Project, NTT Device Innovation
Center.
He received a B.E. in physics from Tokyo
University of Science in 1989 and an M.E. and
Ph.D. in electronics from Tokyo Institute ofTechnology in 1991 and 1994. He joined NTT
Optoelectronics Laboratories in 1994 and began
researching and developing temperature-insensitive semiconductor optical devices for low-power-dissipation WDM networks. During 1998–
2001, he was with NTT Communications, where
he worked in the Tier1 network project for NTT
global IP network services and businesses. His
current research involves optical subsystems andassembly and packaging technologies for their
optical modules. He is a member of the IEEE
Photonics Society, JSAP, and IEICE.

Shigeru Kanazawa

Research Engineer, Metro Access Network
Device Project, NTT Device Innovation Center.
He received a B.S., M.S., and Ph.D. in electronics and communication engineering from
Tokyo Institute of Technology in 2005, 2007, and2016. He joined NTT Photonics Laboratories in
2007, where he has been engaged in research anddevelopment of optical semiconductor devices
and integrated devices for optical communications systems. He is a member of the Japan
Society of Applied Physics (JSAP) and IEICE.

Vol. 14 No. 9 Sept. 2016

4

Global Standardization Activities

Promotion of Environmental
Management According to
ITU-T L.1410 in NTT Group
Minako Hara and Xiaoxi Zhang
Abstract

The NTT Group is moving forward with environmental management practices conforming to ITU-T(International Telecommunication Union - Telecommunication Standardization Sector) Recommendation L.1410. Here, we describe the promotion of energy-saving technology for datacenters, the evaluation of environmental contributions of products and services developed by NTT laboratories, and theenvironmental solution label.
Keywords: environmental management, ICT, ITU-T L.1410

1. Introduction
THE GREEN VISION 2020 formulated by the
NTT Group in November 2010 promoted three
approaches for activities related to three environmental management themes (Fig. 1). The three themes
focus on creating a low carbon society, implementing
closed-loop recycling, and conserving biodiversity.
The three action approaches are efforts to reduce theenvironmental impact of our own business activities(Green of ICT), the use of information and communication technology (ICT) services to contribute to
reducing the environmental impact by society as awhole (Green by ICT), and contributions to various
environmental protection activities together withGroup employees, their families, and local communities (Green with Team NTT) [1].
More specifically, Green of ICT refers to the efforts
by the NTT Group to reduce its own environmental
impact by lowering CO2 emissions through increased
energy efficiency of ICT equipment and ICT facilities
such as networks and datacenters. Green by ICT
refers to efforts that contribute to reducing the environmental impact of society as a whole from a broad
perspective that encompasses all fields. Those efforts
include using ICT to reduce consumption and theneed to transport people and goods, increase the effi1

ciency of energy use in the supply chain, and increase
the visible impact of ICT use on the environment.
Green with Team NTT refers to participation in various activities aimed at protecting the environment by
Team NTT, a group whose members support the corporate social responsibility of the NTT Group andemployees of the NTT Group in general, together
with local communities.
Worldwide attention is being placed on the use of
ICT to increase energy efficiency and efficiency inthe production and consumption of goods as well as
the use of ICT to reduce the transportation of people
and products. To promote the introduction of ICT, weneed ways to quantitatively evaluate the effectivenessof its positive environmental contributions. NTT
laboratories are developing methods for calculating
the environmental impact of the Green of ICT andGreen by ICT approaches.
One result of that research is the development of amethod for calculating the amount of CO2 emissions
over the entire lifecycle of products, networks, andservices, which has been adopted as Recommendation L.1410, “Methodology for Environmental Life
Cycle Assessments of Information and Communication Technology Goods, Networks and Services” by
the International Telecommunication Union - Telecommunication Standardization Sector (ITU-T).
NTT Technical Review

Global Standardization Activities

Green OF ICTReducing the environmental impact of our own business activities.
Green BY ICTUsing ICT services to contribute to reducing the environmental impact
by society as a whole.
Green WITH Team NTT
Contributing to various environmental protection activities together
with Group employees, their families, and local communities.

Fig. 1. THE GREEN VISION 2020.

Here, we describe efforts within the NTT Group topromote effective environmental management basedon that Recommendation.
2. Case study of environmental assessment onenergy-efficient technology for datacenters
based on ITU-T L.1410
Datacenters generally consume about ten times asmuch power per unit floor area as offices, so a quantitative evaluation of the effect of introducing energysaving technology can be expected to contribute to a
reduction of CO2 emissions as such technology isadopted. NTT laboratories have performed a lifecycle
environmental impact assessment based on ITU-T
L.1410 with the objective of evaluating the effect ofenergy-efficient datacenters on the environment. The
subject of the study was a datacenter implementing a
combination of NTT FACILITIES technology,
including a highly efficient air-conditioning system, ahigh-voltage direct current (HVDC) power supply
system, and technology for reusing the heat generated
by equipment (Table 1) [2]. The results of the annual
operation of servers, air conditioning, and the power
supply for a datacenter with a total annual ICT equipVol. 14 No. 9 Sept. 2016

ment power consumption of 183,585 kWh revealed
there was an annual reduction in CO2 emissions ofabout 40%. This case study was published as a supplement to ITU-T L.1410 [3].
3. Assessment of the environmental contributionof research and development (R&D) products
The NTT Service Innovation Laboratory Group,
NTT Information Network Laboratory Group, andNTT Science and Core Technology Laboratory
Group have been engaged in various research projects
related to ICT and are striving to reduce the environmental impact of ICT while contributing to ICT
development on the basis of THE GREEN VISION
2020 [3]. Since the 2014 fiscal year, the three laboratory groups have been efficiently and effectively
operating an integrated environmental management
system designed to reduce the environmental impact
of ICT use. The laboratory groups have moved forward with creating and providing R&D results thatmake positive contributions to the environment. The
R&D results provided to NTT operating companies
make large indirect contributions via customers andsociety as a whole to reducing the environmental2

Global Standardization Activities

Table 1. Technology used in energy-efficient datacenter.
Type

Energy-saving technology

Description

Highly efficient package air conditioners
for datacenters

Designed to match the characteristics of datacenters, these air conditioners
feature highly efficient operation using the latest fans and compressors.

Package air conditioners featuring indirect
outdoor air cooling

These air conditioners reduce power consumption by using outdoor air forcooling; the compressor is stopped in seasons when the outdoor air
temperature is low.

Rack-mounted air conditioners for local
cooling

These air conditioners are mounted on racks near high-temperature servers
to efficiently treat hot air from the servers and reduce the power needed byfans for air circulation.

Use of ground heat

This technology provides cooling in the summer and other seasons by
circulating water through pipes buried underground.

Airflow control

This technology raises the operating efficiency of air conditioners by
preventing the mixing of hot exhaust air from servers with the cool air supplied
from the front of servers.

Power supply

High-voltage direct current (HVDC) power
supply system

This technology decreases the number of power conversion steps to reduce
power loss by supplying power to servers and other equipment with direct
current at about 380 V instead of the conventional 100/200 V alternating
current.

Heat reuse

Use of heat generated by servers

This technology reduces air-conditioning power consumption for both thedatacenter and offices by using the hot air produced by the servers for officeheating.

Air conditioning

impact of ICT use, thus helping to prevent global
warming. In partial accordance with the concept of
ITU-T L.1410, we are making progress in clarifying
NTT’s contribution to the alleviation of global warming by evaluating the contribution of R&D results,
publishing environmental reports, and providing
feedback to the R&D process.
In the 2014 fiscal year, the results of ten research
projects were evaluated, and two that were found tohave made large contributions, “edge router systems
for next-generation networks—high-capacity routing
node for next-generation network transport systems”
and “voice mining platform,” were described in Environmental Report 2015 [4]. Here, we describe thoseresults together with their contributions to the environment.

and the increase in the SSE accommodation ratio wastaken as a quantitative measure of the environmental
contribution.
In the evaluation, there were 154 SSEs per conventional edge router and 240 SSEs for one developededge router*2. The systems were set up for redundancy with active equipment (system 0) and backup
equipment (system 1) as shown in Fig. 2.
The results show that the developed system accommodating 240 units contributed to a 37% decrease inannual CO2 emissions (195 t CO2/year) relative to theconventional case. The main factor in the decrease isthat the increase in the number of SSEs accommodated per edge router reduces the number of requirededge routers to one (or two, considering both theactive and backup systems).

3.1 E
 dge router systems for next-generation
networks
The high-capacity routing node is the core router of
the transport system for the next-generation network
and will be used in a redundant three-level star configuration. The area edge routers installed in edge
node buildings have a higher accommodation ratio
for subscriber service edges (SSEs)*1 than previous
routers, and the evaluation was performed for the casein which the core routers were equipped with newly
developed interface modules. The conventional edge
routers and the developed edge routers were compared for the same amount of information processing,

3.2 Voice mining platform
Problems encountered in conventional analysis ofcalls in call centers include the fact that only a small
volume of calls can be analyzed because the calls
must be transcribed manually and also that the analysis is subjective and time-consuming. Voice mining
technology makes it possible to quickly and flexibly
analyze a large volume of calls objectively and quantitatively, which has previously been difficult to3*1 SSEs: Routers that accommodate access lines on the lowest level.
*2 The maximum SSE accommodation for the developed interface
module.

NTT Technical Review

Global Standardization Activities

Conventional IF module mounted
on a CRS-3 single chassis (16 slots)

Developed IF module mounted on a
CRS-3 single chassis (16 slots)

One edge router accommodating
154 SSEs and one edge routeraccommodating 86 SSEs were used.

One edge router accommodating
240 SSEs was used persystem.

System 0

SSE

System 0

System 1

240 units

SSE*The SSEs were not part ofthe evaluation.

SSE

System 1

240 units

SSE*The SSEs were not part ofthe evaluation.

IF: interface(a) Conventional edge router(b) Developed edge routerFig. 2. Evaluation model for edge router systems for next-generation networks.

achieve. NTT’s voice mining platform records thecalls between operators and customers in call centers
and uses speech recognition technology to convert
the calls to text. Various call analysis techniques thatuse spoken language processing technology are thenperformed. This platform can be used to increase
efficiency in the process of discovering problems incall center operations and in the products and services
offered so that improvement policies can be set [5].
We evaluated the application of this platform in acall center. To quantify the environmental effect, we
compared two cases for analysis (Fig. 3). In the firstcase, the analysis was performed manually after all
calls had been obtained. In the second case, theanalysis work was partially automated by using thevoice mining platform. The call center used for thisevaluation had 50 operators, and the analysis wasdone monthly on all calls, for a total of 12 times in
one year. The evaluation conditions were manualtranscription of recorded call speech for the conventional case and automatic conversion of the recorded
call speech to text followed by partial automation of
the analysis task for the case in which the voice mining platform was used.
The evaluation results show that using the voicemining platform for call analysis contributed toreducing CO2 emissions by 98% (257 t CO2/year)
Vol. 14 No. 9 Sept. 2016

compared to the conventional process of analysis.
The main factor in the emission reduction is the substantial decrease in manual work achieved throughautomation of call analysis.
4. NTT Group environmental solution label
The NTT Group environmental solution labelingsystem certifies ICT solutions provided by the NTT
Group that exceed a specified criterion for reducing
the environmental impact (reduction of CO2 emissions) of ICT as environment-friendly solutions [6].
The use of some ICT services contributes to reducing
the environmental impact of our society as a whole[7]. In the NTT Group, services that reduce CO2
emissions by 15% or more are certified as environment-friendly solutions and are marked with a label
in the service catalog and other places (Fig. 4). Our
objective in providing such services is to reduce theenvironmental impact of the NTT Group, our customers, and society as a whole. We have been evaluating
the effect of ICT services on reducing CO2 emissions
according to the Environmental Efficiency Assessment Guidelines for ICT Services issued by the Japan
Forum on Environmental Efficiency (currently
merged with the Life Cycle Assessment Society ofJapan) [8]. The article “Assessment of ICT Effects in
4

Global Standardization Activities

Storage of callvoice data

Store
voice
data.
Voice data

Manual analysis
Call transcription

Store
voice
data.

Storage of voice
data

Voice data
Automatic
conversion of
speech to text

Data
serverText data

PC

Detect topic
search.
Determine reason
for topic surge.

Analysis by call analysis system
Identify service
Analysisfor which “topic”
serveris frequent.
PC
Identify surge
period for “topic.”
Determine reason
for topic surge.

(a) Conventional analysis(b) Voice mining platform

Fig. 3. Evaluation model for voice mining platform.

Fig. 4. NTT Group environmental solution label.

the Reduction of Environmental Impact,” which isbased on those guidelines, appeared in the “Study
Group on ICT Policy Concerning Global Warming”
report issued by the Ministry of Internal Affairs andCommunications of Japan in April 2008. The
approach of the assessment methods described in thearticle were incorporated in ITU-T L.1410.
Here, we present and explain the assessment results
for three solutions that are likely to have relatively
high environmental impact reduction effects fromamong the solutions that were certified in 2015 and
2016.
4.1 E
 nterprise Cloud from NTT
Communications
Enterprise Cloud is a global cloud service that takes
5

advantage of NTT Group’s strong technical capabilities and abundant expertise concerning networks,
datacenters, applications, and security as a telecom
carrier (Fig. 5). Enterprise Cloud makes it possible toreduce CO2 emissions by providing for virtualizationof servers and storage. The assessment conditions
involved an enterprise with four offices and 300
employees that operates and manages ICT storage
facilities with a capacity of 6900 GB over a period of
one year. The assessment revealed that use of thesystem reduced CO2 emissions by 74% relative to aconventional system.
4.2 TopicRoom from NTT Software
TopicRoom is a chat tool for fast, secure, and simple sharing of business information. It can be used on
desktop computers, tablet devices, and smartphones,
so work efficiency can be increased by sending amessage on an issue to be discussed to TopicRoom
from any device so that the issue can be resolved
quickly (Fig. 6) [9]. Use of TopicRoom can be
expected to reduce the time and movement of people
to attend meetings as well as the use of paper.
Under the assessment conditions of 48 meetings
involving a total of five people from five offices (Shinagawa, Ogikubo, Yokohama, Nagoya, and Osaka)over a period of one year, the use of TopicRoom
reduced CO2 emissions by 78% relative to the conventional process (where employees traveled toattend meetings).
NTT Technical Review

Global Standardization Activities

Backbone application
OracleManagement service

SAP

Microsoft
Dynamics

ExchangeEnterprise Cloud

Security service

SDN

Datacenter service

Network service

SDN: software-defined network*Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
SAP is a registered trademark of SAP AG in Germany and in several other countries all over the world.
Microsoft Dynamics is a registered trademark of Microsoft Corporation in the United States and/or other countries.

Fig. 5. Overview of Enterprise Cloud.

SampleTenant3 - TopicRoom - Sales

TopicRoom - Sales

Keyword search Settings New window Version

LogoutTopicRoom - Sales

Time line

Log

Topic

Time line

Today’s sales meeting will startat 15:00 in Conference Room 4

Takuya Hara
14:16

Log

Room
Information

Topic

We’ll get together at 15:00 in Conference Room 4 for today’s sales meeting.

14:16

TopicRoom - Sales

14:17

Takuya Hara

Takuya Hara
14:17

Get

Get

together!

together!

Kenta Chiba

OK.

14:19

Ai Ichikawa

I’m out of the office, so I’d like to participate by phone conferencing.
Could you give me the number?

14:23

Takuya Hara

03-1224-2675

14:23–New messages below–

Kenta Chiba
OK.

Ai Ichikawa

Ai Ichikawa

03-1234-5678

14:19

Ryoichi Matsudo

Thanks.
I’ll call at that time.

Ai Ichikawa

Kenta Chiba

I’m out of the office, so I’d liketo participate by phone conferencing.
Could you give me the number?
Input message.

Member
14:27

Takuya Hara (2015/11/17 14:23)

Ryoichi Matsudo I’m going out for a customer meeting.
Please create a topic for any important discussion.

Takuya Hara
Misaki Funabashi

Send

Send

(a) Android/iOS

14:28(b) Windows/Mac

Fig. 6. Images of TopicRoom discussion threads.

4.3 BizInspect® from NTT DATA Shikoku
BizInspect® is a solution in which a tablet device isused to check inspection items, enter results, andautomatically generate and save reports during theinspection, testing, investigation, or repair of buildings and other facilities (Fig. 7). When performed in
the conventional way, this task involves carrying alarge amount of paper materials and requires a lot ofVol. 14 No. 9 Sept. 2016

time to compile reports with photographs of theinspection site. Using BizInspect reduces the amountof materials needed and makes the work more efficient. For periodic inspections and other such tasks
that are performed repeatedly, inspectors can checkthe previous inspection results, so it is possible toperform the inspection efficiently while maintaining
the inspection information obtained up to the6Global Standardization Activities

OfficeField
Ordering party
Inspection
preparation

ReportReport

Crack
Photo

Report checking

Results of storage
and sharing

Inspection sheet

Inspection work
ReportReport writing

Fig. 7. Overview of BizInspect®.

previous inspection. With paperless inspection materials and reports, the natural resources consumed for
paper can be reduced, and the storage space requiredfor paper materials can also be eliminated. Anotheradvantage is that the input of information is not duplicated in the on-site inspection work or in the report
production work that is done in the office, so less timeis required to complete the task.
BizInspect was assessed in conditions involving
four inspections and the production of reports forthem at 900 locations over a one-year period, and theresults revealed that the use of BizInspect resulted ina 68% reduction in CO2 emissions relative to the conventional process.

References
[1]
[2]
[3]
[4]

[5]

[6]

5. Future challenges[7]

The NTT Group will continue to develop environment-friendly solutions and to promote the social
contribution and environmental impact reduction
effect of ICT in ITU-T well into the future.

7

[8]
[9]

NTT website of THE GREEN VISION 2020,
http://www.ntt.co.jp/kankyo/e/protect/vision.html
Website of NTT FACILITIES,
http://www.ntt-f.co.jp/english/
ITU-T, “Supplement to ITU-T L.1410 - Case Study: A Hybrid
Approach based Comparative Analysis of the Environmental Impactof a Baseline Data Centre and an Energy-efficient Data Centre,” 2016.
NTT Service Innovation Laboratory Group, NTT Information Network Laboratory Group, and NTT Science and Core Technology
Laboratory Group, “Environmental Report 2015” (in Japanese).
http://www.ntt.co.jp/RD/environment/pdf/rep2015.pdf
S. Kawamura, K. Machida, K. Matsui, D. Sakamoto, and M. Ishii,“Utilization of Artificial Intelligence in Call Centers” NTT Technical
Review, Vol. 14, No. 5, 2016.
https://www.ntt-review.jp/archive/ntttechnical.php?contents=
ntr201605fa7.html
Website of NTT Group environmental solution labeling system (inJapanese),
http://www.ntt.co.jp/kankyo/protect/label/index.html#2016
Ministry of Internal Affairs and Communications, “To Utilize ICT for
the Environment,” 2007.
Japan Forum on Environmental Efficiency, “Environmental Efficiency Assessment Guidelines for ICT Services,” 2006 (in Japanese).
http://lca-forum.org/environment/forum/past/pdf/10.pdf
NTT Software website of TopicRoom (in Japanese),https://www.ntts.co.jp/products/topicroom/index.html

NTT Technical Review

Global Standardization Activities

Minako Hara

Senior Manager, Environment Management
Promotion Office, Technology Innovation
Department, NTT WEST.
She received a B.S. in applied chemistry from
Tokyo University of Science in 1998, and an
M.E. and Ph.D. in applied chemistry from the
University of Tokyo in 2000 and 2005. During
2004–2006, she was a post-doctoral researcher at
the Japan Science and Technology Agency,
where she developed a methodology of environmental impact assessment and an eco-efficiency
index. She joined NTT Energy and Environment
Systems Laboratories in 2006 and studied environmental assessment, including life cycle
assessment and material flow analysis. She
moved to NTT WEST in 2016. She is a memberof the Society of Environmental Science, Japanand the Society for Environmental Economics
and Policy Studies.

Vol. 14 No. 9 Sept. 2016

Xiaoxi Zhang

Research Engineer, Environmental Technology and Management Project, NTT Network
Technology Laboratories.
She received a B.S. and M.S. in social engineering from Tokyo Institute of Technology in2007 and 2009. Since joining NTT Energy andEnvironment Systems Laboratories in 2009, she
has been engaged in research on risk-based management of telecommunication infrastructures.
She moved to NTT Network Technology Laboratories in 2015. She is currently researching environmental assessment of ICT use. She is amember of the Institute of Electronics, Information and Communication Engineers.

8Global Activities of NTT Group

Arkadin: Global Unified
Communications & Collaboration
Champion in a Dynamic Digital
Workplace
Didier Jaubert
Chief Executive Officer, Arkadin SAS
Abstract

Arkadin is one of the largest and fastest growing communications and collaboration service providers
in the world. With a vision rooted in the belief that progress emerges from people’s desire to share, Arkadin offers a complete range of integrated audio, web, video, and unified communications solutions. This
article introduces the company’s operations, strategies, and potential future as an NTT Communications
Group company.
Keywords: audio/web/video conferencing, cloud, digital workplace

1. Introduction
In a global workplace that is becoming increasingly
digital and connected, enterprises must become moreagile to compete and succeed. Rapid and seamless
communications through any device is essential at
every level of the organization, whether between
departments, divisions, or countries, anywhere in the
globe. The net result is a new importance on workforce engagement. Having the right mix of collaborative technologies is essential for driving productivity,
improving employee wellbeing, and retaining top talent.
At Arkadin, we have a collection of market-leadingaudio/web/video conferencing and unified communications solutions that are essential for success in our
digitally connected global workplace. All services aredelivered in the cloud and are backed by a cuttingedge infrastructure for premium service quality.
Our business model is based on deploying services
that are administered locally by highly trained Arka1

din professionals who are geographically and culturally close to our clients. As entrepreneurs, we beganwith this innovative local approach to customer service from our start in 2001, and it remains a key pillarof our success.
Arkadin is one of the largest and fastest growing
providers of unified communications and collaboration (UC&C) services in the world. We have operations in over 30 countries, with 56 offices spreadthroughout the Americas, EMEA (Europe, the Middle East, and Africa) and CEMEA (Central and Eastern Europe, the Middle East, and Africa), and in the
Asia Pacific region, including China, which serve over
50,000 clients from a vast range of industries (Fig. 1).
Our mission is to lead companies to increased
growth and success by delivering positive collaboration experiences. We are driven by the idea that progress emerges from people’s desire to share and work
together. As such, our vision is to be at the forefront
in meeting growing demand for cloud-based UC&C
services by providing organizations with the best
NTT Technical Review

Global Activities of NTT GroupWe are a global leader in UC&C solutions in the cloud.

+30

19

countries

languages+50,000+1200

customers

employees

21%

+50

compoundedannual growthrate 2010–2015“ A level of growth such as this cannot be achieved without a strong commitment toquality of the products and management of the company. Arkadin has demonstrated
the soundness of its growth strategy. ”

offices

Deloitte.

Fig. 1. Global service coverage.

As a leading expert in collaboration, we understand your business challenges.

– Consolidating different collaboration technologies,
integrating legacy systems– Reducing upfront expenditure and resources– Minimizing total cost of ownership– Creating a UC&C infrastructure that is scalable andfuture-proof– Demonstrating return on investment

Fig. 2. Expertise in collaboration technologies.

solutions for enhancing their business (Fig. 2).
2. Strong performance positions Arkadin as#1 cloud collaboration service provider
Arkadin is profitable and has gained a 21% compound annual growth rate over the past five years,
which is very healthy. We hosted just over 30 million
meetings in 2015, with 119 million participants
clocking 82 million hours in total, as well as 40,000
Vol. 14 No. 9 Sept. 2016

events, of which 3000 were webcasts. Our strong
performance has made us the fastest growing cloud
collaboration provider in the industry (Fig. 3).
3. Arkadin values are significant
competitive differentiators
Values run through everything we do, both from acultural and business perspective, and we are convinced they set us apart in the marketplace. Our
2

Global Activities of NTT Group

Arkadin is the fastest growing collaboration service provider in the industry.

29

26
21

Number of countries
12
Arkadin has operations
8
3

Number of 173
employees
6135
13Group revenue
12
6
1
2

286

1000

23
788

16

739
597
508

102

392

3

1

15

321

31

188

32
1094

33

33

1200 1250
264M€

202

264M€
Revenue group level in 2015219
+21% / year
Compounded annual growthrate 2010–2015

129

88
70

2015

53

30.3 million meetings

37
119 million participants

21

82 million hours

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015

Fig. 3. Achieving strong growth.

cultural values are based on respect, working together, entrepreneurial spirit, and workplace enjoyment,
while our business values are centered on creating
and sustaining a premium customer experience. They
are inextricably linked. A premium customer experience begins with a strong culture within Arkadin. We
know that a happy workforce makes for happy customers. This idea is central to our business, and webelieve it gives us a significant advantage. We are so
passionate about our values that we recently launched
a new website to showcase how they apply across all
aspects of our organization [1].
4. Strategic acquisitions to propel agile
global growth
Acquisitions of organizations with stellar trackrecords, advanced technologies, and trusted reputations allow us to expand our global footprint andmarket share. Our most recent example is our purchase of T-Uno last year, which enabled us to enter
Colombia with the market leader in the region. We
also acquired AT Conference [2] in 2015, a New
York-based audio and web conferencing provider,which is helping us to increase our customer base andmarket share in the North American collaboration
market. Arkadin will be keeping the AT Conference
brand and Information Systems to leverage theirstrength in the small- and medium-sized businesses
3(SMB) sector. Their service and support complement
our existing capabilities, while our full suite of
UC&C solutions are a great fit for their customers.
We also target potential technologies for acquisition that will enhance our customer value propositionand provide cutting-edge UC&C solutions for meeting all communications requirements.
Our 2014 acquisition of implement.com [3], a key
Microsoft partner with a stellar track record inenabling service providers to leverage hosted voiceand Microsoft technologies, has allowed us to extend
our UC-as-a-Service (UCaaS) offerings so that businesses can harness the full power of UC for greater
workplace productivity. Arkadin has benefited fromtheir honed UC expertise and advanced collaboration
service platform. The acquisition has been instrumental in giving us the most advanced business productivity tools, plus all telephony capabilities, in a convenient, cost-efficient cloud-based offer in Arkadin
Total Connect.
In the video category, our acquisition of French
video specialist Novasight [4] in 2012 gave us a leg
up in video managed services, an important longterm growth market.
The synergies from these acquisitions are significant. Together with NTT Communications, we offer
the complete package: the most advanced UC&C
technologies and global infrastructure plus comprehensive, locally administered support services, resulting
NTT Technical Review

Global Activities of NTT Groupin a tremendous competitive advantage on a worldwide basis and a win-win for our customers.
5. Product and marketing strategies driven bya digitally transformed workplace
We are in a hyper-connected world where anytime,
anywhere, any-device communication is the expectation. Trends driven by the cloud, social communities,
and a mobile workforce are driving dramatic changes
in global workplaces, and they will only intensify as
millennials become more dominant and achieve leadership positions. Workers’ expectations are changing
fast, and collaboration technology is a vital enabler.
There is a new importance placed on the engagementof people and a flatter work structure. Workers are
expected to access their information from anywhere—even their corporate intranets. Teams need tocollaborate virtually across geographical barriers andtime zones to be effective and competitive. And flexible work policies are no longer just something niceto have, but are essential for driving productivity,
retaining top talent, and reigning in costs for unnecessary business travel. In short, collaboration technologies are vital enablers.
All of these trends and developments translate to avery dynamic market for our services, and we are
extremely well positioned to profit. We have theambition and an aggressive plan to capture a sizable
share of the market. Our strategy is centered on threestrategic pillars, which are explained in the following
subsections.
5.1 Best UC&C solutions in the cloud
There is no future without great products. Arkadin
has a two-pronged product strategy that has fueled
our strong growth. We have our own branded Arkadin­
Anytime audio conferencing and ArkadinAnywhere
web conferencing, with the most digitally advanced
cloud collaboration platform [5].
We also maintain partnerships with leading technology companies including Microsoft, ON24,
Adobe, Vidyo, Cisco, Blue Jeans Network, and IBM
for best-in-class cloud solutions that are rich in features, intuitive, and integrated with our premium
audio conferencing for an exceptional user experience. Each of our partners has a different set of capabilities that enable us to be a true one-stop shop for
UC&C services.
5.1.1 UC—a key enabler of digital workplacetransformation
In the UC sector, Arkadin offers a suite of marketVol. 14 No. 9 Sept. 2016leading solutions from Microsoft Skype*1 for Business and Cisco Jabber*2 combined with WebEx*2.
Delivered in the cloud for fast international deployment offering a high return on investment (ROI), theservices are integrated with Arkadin’s stable, crystalclear audio conferencing and combined with ourcomprehensive support services.
The center of our UC strategy is Arkadin Total Connect, a Microsoft Skype for Business hosted service.
Integrated into Arkadin ‘as a Service,’ Arkadin Total
Connect offers voice, contact center, and conferencing services to Office 365*3, all under a ‘single paneof glass,’ which frees up information technology (IT)teams to focus on other strategic projects. The voiceenabled Office 365 deployment seamlessly integrates
with Exchange Online (within Office 365) for unified
messaging that drives efficiencies while reducing
costs associated with traditional PBX (private branchexchange) and third-party conferencing services.
Businesses benefit from the convenience of a single
all-in-one solution, which offers substantial cost savings from on-premises UC deployment, coupled with
Arkadin’s premium quality integration, networking
expertise, and customer support.
In December 2015, Arkadin was named a launch
partner for the new Skype for Business meetings andvoice services in Office 365. Arkadin will be a key
resource for driving the rollout of the new services.
We are one of only a few service providers operating
on a global scale that meet Microsoft’s requirements
and enable it to offer a fully integrated platform formeeting and voice services (Fig. 4).
Being named a launch partner is a testament to oureight-year history of success in hosting voice in thecloud for Microsoft UC services. As an NTT Communications’ subsidiary, we can leverage the company’s sophisticated global voice architecture and integration capabilities and help customers reduce thecosts and complexity associated with voice deployments. Our professional end-user support, training,
migration, and change management capabilities guarantee efficient rollouts. The net result is a single
source for deploying Office 365 as a business-classphone system, contact center, and conferencing platform delivered in the cloud.
*1 Microsoft and Skype are registered trademarks of Microsoft Corporation in the United States and/or other countries.
*2 Cisco Jabber and WebEx are registered trademarks of Cisco Systems, Inc. and/or its affiliates in the United States and certain othercountries.
*3 Office 365 is a registered trademark of Microsoft Corporation in
the United States and/or other countries.

4

Global Activities of NTT Group

Arkadin is bridging the gap in Microsoft Office 365.

*Excel Launch Icon 2012, Exchange Launch Icon 2013, Office with Office 2012 Design, OneNote Launch Icon 2012, Outlook Launch Icon
2012, PowerPoint Launch Icon 2012, Publisher Launch Icon 2012, Skype “S” Design, SharePoint, SharePoint Launch Icon 2012, andWord Launch Icon 2012 are registered trademarks or a trademark of Microsoft Corporation in the United States and/or other countries.

Fig. 4. A key provider of Microsoft Skype for Business services and voice services in Office 365.

A good example of how we are helping clients tosucceed with Office 365 is with a Texas-based IT
services firm. ENTRUST Technology Consulting
Services required a hosted UC solution that would
have all collaboration features and mobility in one
product, plus voice and a call center solution. Arkadin
Total Connect for Office 365, integrated with Clarity
Connect, provided everything they needed in a simple-to-manage hosted solution. It has transformed theway they think about their operations. The ENTRUST
workforce is now empowered to operate from wherever they are, and is thus able to better service theircustomer base and expand their footprint since they
are no longer dependent on any single location.
“Arkadin Total Connect for Office 365 enables
our workforce to operate from anywhere they are.
Working at home is no different than working
from our office. It has transformed the way wethink about our operations.”
Mitchell R. Sowards, President, ENTRUST
5.2 Premium customer experience
In this fast changing business environment that is
driving tremendous change in global workplaces, it ismore essential than ever to listen to customers and5

adapt strategies when necessary for delivering on
their requirements.
A premium client experience is in our DNA, and it
is a key competitive differentiator. Our local yet
global approach to customer service sets us apart in
the industry and delights our clients since they deal
with local teams who speak their language and understand their culture. Regional customer success teams
take the time to understand our clients’ unique needs
and challenges, whether they are a global conglomerate or an SMB, so that we can implement the toolsthat will deliver a high ROI. It is all about a complete
365-degree experience in the spirit of a true partnership for building customer loyalty.
Our service strategy is truly end-to-end and multilayered, encompassing live assistance 24/7 in 19
languages, and user training that is live, onsite, andvirtual. We offer sophisticated reporting tools andprofessional services complete with project managers, and technical pre-sales and service relationshipmanagers for more complex collaboration and UC
deployments. Our value-added capabilities also
include professional services for concierge and endpoint management, infrastructure monitoring, andbilling services (Fig. 5).
Arkadin’s customer Hatch, one of the world’s
NTT Technical Review

Global Activities of NTT GroupBest of
breed
UC&C
solutionsSuperior
qualityof service

Responsive,end to end
local
supportInteroperability
andintegration

All the ingredientsneeded to help
our clients with
their digitaltransformation
strategies

Fig. 5. Arkadin value proposition.

pre-eminent suppliers of technical and strategic services for the mining, metallurgical, and energy industries, with operations throughout North America,
Europe, the Middle East, South America, Asia Pacific, and South Africa, relies on virtual meetings tocommunicate high level company information to its
10,000 global employees. Hatch recently experienced
the value of our live, value-added global service strategy in conjunction with a large annual meeting inSouth Africa. We had the complete array of audio,
video, and multimedia solutions, plus experienced
engineers and support technicians in South Africa as
well as their headquarters in Ontario, Canada, forpulling off the meeting. For the first time, Hatch had
every aspect of the event covered by one provider.
Following the success of the meeting, Arkadin now
provides a cost-efficient, one-vendor approach for allof Hatch’s large global meeting needs regardless of
where their conferences are staged.
“Arkadin had the complete array of audio, video,
and multimedia solutions, plus experienced engineers and support technicians in South Africa as
well as Ontario, Canada, for pulling off our large
general meeting. It was the complete package.
For the first time we had every aspect of the event
covered by one provider. The huge success of ourmeeting convinced us to use Arkadin for all of ourlarge global meetings and webcasts regardless of
where in the world they are located.”
Stephen Goodger, ICT Lead – Operational
Management, Hatch
To ensure we continue to deliver the best experiVol. 14 No. 9 Sept. 2016ence for our clients, we have instituted a threepronged plan that addresses People Development,
World Class Operations for delivering the mostadvanced infrastructure, and World Class Digital
Customer Experiences. As an example of our commitment to customers, we implemented a new Customer Lifecycle Program for an improved, globallyconsistent onboarding process for all new Arkadin­
Anytime and ArkadinAnywhere users. It is part of arenewed focus on improving our customers’ digital
experience and reinforces our overall value proposition, while giving us a significant competitive advantage around the customer pain point of low new-user
adoption.
We devised a personalized new-user nurture campaign to replace the original “one shot” welcome
pack. It consists of three strong induction emails withreasons to activate the service and handy tools to
make collaboration easier. The tools include: a Getting Started Guide, Mobility Apps, and a Productivity
Toolbar. Taking advantage of Arkadin’s newly
refreshed brand, these communications are morevisual and dynamic (Fig. 6). All new customers who
still fail to activate after this first phase of induction
are sent through a second ‘adoption’ nurture flow
with additional motivational messages to encouragethem to get started.
We rolled out the program in the second half of2015, and it is now live in most Arkadin countries. To
date, customer engagement has been extremely high,with adoption levels for new users averaging 59%
compared to the previous global average of 43%. In
addition to being added value for customers, it is also
a high revenue generator for Arkadin, creating 2
6

Global Activities of NTT GroupWe devised three strong induction emails for new users.

CLEAR

CONCISEACTION

Fig. 6. New welcome emails.

million worth of net new revenue since its launch lastyear, and it will continue to build as new territories
and products are added.
We have now made onboarding incredibly simple,
and the results speak for themselves. In addition, weare proud to be a finalist in this year’s Oracle Markie
Awards for “Best International Campaign 2015”
based on the global impact of this customer-led initiative.
5.3 E
 xpansion and profitable long-term growth
as a member of NTT GroupIn addition to having the best technology partners,
Arkadin will continue to align with strategically positioned telecommunications companies, agents,
resellers, and systems integrators who share our philosophy about the value of cloud-based UC&C services. At the center of this dynamic ecosystem are
NTT Communications and fellow NTT Group subsidiary Dimension Data. We have programs in placethat leverage each of their strengths, resulting in powerful synergies for our customers. For example:•	Arkadin is collaborating on NTT Communications’ Arcstar brand of collaboration services inJapan. We recently launched the Japan Platform
in April 2015 as an Arcstar UCaaS Microsoft
Type service utilizing Arkadin’s international
platform.
•	Reselling agreements are in place in North
America, Europe, and Asia. Each market has adistinct platform, which is a tremendous competitive advantage, especially in selling to large
global companies.
•	Our partnership is not all about business. The
7people side is equally important. Considering thevery different cultural orientations and work
styles between teams based in Japan and theWest, we have instituted programs to acceleratemutual understanding and appreciation of ourstrengths and differences. One example is our
employee exchange program that enables us toconnect and share our knowledge, culture, andvalues. To date, approximately 10 employees
from both companies have participated by leaving their home turf for offices in Paris and Montpelier, France, as well as in Hong Kong, Tokyo,
and Singapore. We are confident programs likethis will be enormously beneficial in building
better teamwork and synergies between teams
across the globe.
6. Bright and digital future withNTT Communications
Our opportunities for greater global growth andleadership are unlimited and are just beginning to berealized. Arkadin is well positioned within the larger
NTT Group for enabling the organization and its subsidiary companies to achieve global leadership incloud-based UC&C services. Together we offer customers the most sophisticated infrastructure, networking, and telecommunications capabilities. In the
30 months since NTT Communications acquired
Arkadin, we have been working closely as a team toensure we leverage our complementary strengths forproviding the most comprehensive collection of thehighest quality UC&C solutions available in the market.
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Global Activities of NTT Group

Photo 1. Arkadin team.

Recently, NTT Communications launched Vision2020 – Transform. Transcend, an innovative initiativethat is perfectly placed to serve an ever-changing
digital world [6]. Arkadin will work together withNTT Communications to continually assess market
trends and provide customers with new state-of-theart technologies that will not only bring businesschange, but will break boundaries and extend ourimagination.
We believe our team of global entrepreneurs andour stellar portfolio of UC&C products, set within ahigh-growth market, give us all the components weneed for a bright and digital future (Photo 1).
References
[1]
[2]
[3]
[4]
[5]
[6]

Arkadin, https://www.arkadin.com/
AT Conference, http://www.atconference.com/
implement.com, http://www.implement.com/
Novasight (in French), http://www.novasight.fr/
Arkadin UK, https://www.arkadin.co.uk
NTT Communications, http://www.ntt.com/en/index.html?link_
id=ostp_headon

Didier Jaubert

Chief Executive Officer, Arkadin SAS.
Didier Jaubert brought 30 years of commercial
and general management experience with IT andtelecommunications multinationals to Arkadin.
He had senior roles at Orange Business Services,where he was recognized for his expertise inoutsourcing and system integration, and at IBM,
where he held various management positions insales and global services in France and the U.S.
He has a degree in engineering from the Ecole
Centrale Paris and an economics degree from
Paris University. He has been Chief Executive
Officer of Arkadin since October 2015.

Vol. 14 No. 9 Sept. 2016

8

New NTT Colleagues––We welcome our newcomers to the NTT Group
This is a corner of the NTT Technical Review where we introduce our new affiliate companies.

BIT.Group
SAP service provider; established in 2004; headquartered in Bautzen, Germany
Founded in 2004, BIT.Group GmbH stands out as a provider of innovative services for national and international customers. The multi-certified SAP* partner has about 380 employees and offers extensive SAP services
focusing on SAP application management, technology services, application lifecycle management, and cloudservices.
In June 2016, BIT.Group GmbH and itelligence AG, a Germany-based SAP consultancy firm and a subsidiaryof NTT DATA Corporation, reached an agreement for itelligence AG to acquire 100% of outstanding shares in
BIT.Group GmbH.
With this acquisition, itelligence AG is cementing its position as one of the leading information technology
service providers in Germany with a strong focus on cloud and SAP managed services. For further information
about the acquisition, please visit: http://itelligencegroup.com/us/crprtprsrlss/itelligence-acquires-applicationmanagement-and-cloud-specialist-bitgroup/
Contact:
Public Relations Department
NTT DATA Corporation
Tel: +81-3-5546-8051

VietUnion
Payment service provider; established in 2008; headquartered in Vietnam
Since 2011, NTT DATA Corporation has been investing in VietUnion Online Services Corporation (VietUnion), a group company of Saigon Construction Corp (SCC). VietUnion has been expanding its payment business primarily through “Payoo.” Payoo enables users to make different sorts of bill payments for almost all the
big chain retailers, nearly 4000 stores in total throughout Vietnam, such as convenience stores, ICT (information*

1

SAP is a registered trademark of SAP AG in Germany and in several other countries all over the world.

NTT Technical Review

New NTT Colleagues

and communication technology) shops, shopping centers, and supermarkets. Payoo also has a mobile application
for smartphones that enables customers to pay charges via Internet banking provided by over 20 local banks.
VietUnion also provides various software solutions such as a mobile POS (point of sales) system, smart-card
solutions for transportation, location-based solutions for billers, and platforms for tuition fee management andcollection for 1700 schools in Ho Chi Minh City.
In June 2016, NTT DATA Corporation reached an agreement to purchase additional shares in VietUnion
through its subsidiary NTT DATA Asia Pacific Pte. Ltd and to take on VietUnion as an NTT DATA Group company. Partnered with SCC, NTT DATA Corporation is committed to support VietUnion in strengthening its
internal structure as well as establishing its position in the market in order to generalize non-cash payment in the
country. For further information about the acquisition, please visit: http://www.nttdata.com/global/en/newscenter/others/2016/062300.html
Contact:
Public Relations Department
NTT DATA Corporation
Tel: +81-3-5546-8051

Vol. 14 No. 9 Sept. 20162

External Awards
Achievement Award
Winner: Naonori Ueda, NTT Communication Science Laboratories
Date: June 2, 2016
Organization: The Institute of Electronics, Information and Communication Engineers (IEICE)
For his pioneering research on statistical learning theory.
Best Presentation at JPA Annual Convention
Winner: Ryunosuke Sudo, Kyushu University; Daisuke Satoh, NTT
Network Technology Laboratories; Yuji Takano, Doshisha University; and Takemi Mochida, NTT Communication Science Laboratories
Date: June 16, 2016
Organization: The Japanese Psychological Association (JPA)
For “Examination of the Measures and Subjective Stress of Calling
Party during Disaster.”
Published as: R. Sudo, D. Satoh, Y. Takano, and T. Mochida, “Examination of the Measures and Subjective Stress of Calling Party during
Disaster,” Proc. of the 79th JPA Annual Convention, Nagoya City,
Japan, Sept. 2015.
Best Paper Award 2015
Winner: Hiroaki Shiokawa, University of Tsukuba; Yasuhiro Fujiwara and Yasuhiro Iida, NTT Software Innovation Center; Makoto
Onizuka, Osaka University
Date: June 18, 2016
Organization: The Database Society of Japan (DBSJ)
For “Density-based Clustering for Dynamic Graphs.”
Published as: H. Shiokawa, Y. Fujiwara, Y. Iida, and M. Onizuka,“Density-based Clustering for Dynamic Graphs,” DBSJ Japanese
Journal, Vol. 14-J, 4, Mar. 2016.
TTC Chairman’s Prize
Winner: Akira Takahashi, NTT Network Technology Laboratories
Date: June 21, 2016
Organization: Telecommunication Technology Committee (TTC)
For his contribution to the standardization of quality of service andquality of experience concerning audiovisual communication services and IP networks.
JSAI Best Paper Award 2015
Winner: Makoto Nakatsuji, NTT Service Evolution Laboratories;
Yasuhiro Fujiwara, NTT Software Innovation Center; Hiroyuki Toda
and Hiroshi Sawada, NTT Service Evolution Laboratories; Jin Zheng
and James Hendler, Rensselaer Polytechnic InstituteDate: June 24, 2016
Organization: The Japanese Society for Artificial Intelligence(JSAI)For “Tensor Factorization that Utilizes Semantics behind Objects.”
Published as: M. Nakatsuji, Y. Fujiwara, H. Toda, H. Sawada, J.
Zheng, and J. Hendler, “Tensor Factorization that Utilizes Semantics
behind Objects,” Trans. JSAI, Vol. 30, No. 3, pp. 510–525, May 2015
(in Japanese).
JSAI Incentive Award 2015
Winner: Koh Takeuchi, NTT Communication Science Laboratories;

1

Yoshinobu Kawahara, ISIR, Osaka University; and Tomoharu Iwata,
NTT Communication Science Laboratories
Date: June 24, 2016
Organization: JSAI Special Interest Group on Fundamental Problems in Artificial Intelligence (SIG-FPAI)
For “Structured Regularizer for Spatio-temporal Matrix Completion.”
Published as: K. Takeuchi, Y. Kawahara, and T. Iwata, “Structured
Regularizer for Spatio-temporal Matrix Completion,” Proc. of the100th SIG-FPAI, pp. 47–52, Kumamoto, Japan, Mar. 2016 (in Japanese).
The Meritorious Award on Radio
Winner: Yoshitaka Shimizu, NTT Network Innovation Laboratories;
Nei Kato, Tohoku University; Kouji Eguchi, Fujitsu Limited; andShinichi Yamaguchi, NTT Communications
Date: June 27, 2016
Organization: Association of Radio Industries and Businesses(ARIB)For development of the movable and deployable ICT resource unit
(MDRU).
OECC/PS 2016 Best Paper Award
Winner: Kazushige Yonenaga, Kengo Horikoshi, Seiji Okamoto,
Mitsuteru Yoshida, Yutaka Miyamoto, and Masahito Tomizawa, NTT
Network Innovation Laboratories; Takeshi Okamoto, Hidemi Noguchi, Jun-ichi Abe, and Junichiro Matsui, NEC Corporation; Hisao
Nakashima, Yuichi Akiyama, Takeshi Hoshida, and Hiroshi Onaka,
Fujitsu Limited; Kenya Sugihara, Soichiro Kametani, Kazuo Kubo,
and Takashi Sugihara, Mitsubishi Electric Corporation
Date: July 6, 2016
Organization: The 21st Optoelectronics and Communications Conference/International Conference on Photonics in Switching 2016
(OECC/PS 2016) organizing committee
For “Field Demonstration of Modulation Format Adaptation Basedon Pilot-aided OSNR Estimation Using 400Gbps/ch Real-time DSP.”
Published as: K. Yonenaga, K. Horikoshi, S. Okamoto, M. Yoshida,
Y. Miyamoto, M. Tomizawa, T. Okamoto, H. Noguchi, J. Abe, J.
Matsui, H. Nakashima, Y. Akiyama, T. Hoshida, H. Onaka, K. Sugihara, S. Kametani, K. Kubo, and T. Sugihara, “Field Demonstrationof Modulation Format Adaptation Based on Pilot-aided OSNR Estimation Using 400Gbps/ch Real-time DSP,” OECC/PS 2016, TuB2-2,
Niigata, Japan, July 2016.
OECC/PS 2016 Best Paper Award
Winner: Kengo Nozaki, Shinji Matsuo, Takuro Fujii, Koji Takeda,
Masaaki Ono, Abdul Shakoor, Eiichi Kuramochi, and Masaya
Notomi, NTT Basic Research Laboratories
Date: July 6, 2016
Organization: OECC/PS 2016 organizing committee
For “Sub-fF-capacitance Photonic-crystal Photodetector towards
fJ/bit on-chip Receiver.”Published as: K. Nozaki, S. Matsuo, T. Fujii, K. Takeda, M. Ono, A.
Shakoor, E. Kuramochi, and M. Notomi, “Sub-fF-capacitance Photonic-crystal Photodetector towards fJ/bit on-chip Receiver,” OECC/
PS 2016, TuE1-3, Niigata, Japan, July 2016.

NTT Technical Review

Papers Published in Technical Journals and Conference Proceedings

OECC/PS 2016 Best Paper Award
Winner: Wataru Kobayashi, NTT Device Technology Laboratories;
Naoki Fujiwara, NTT Device Innovation Center; Takahiko Shindo,
NTT Device Technology Laboratories; Shigeru Kanazawa, NTT
Device Innovation Center; Koichi Hasebe, Hiroyuki Ishii, and Mikitaka Itoh, NTT Device Technology Laboratories
Date: July 6, 2016
Organization: OECC/PS 2016 organizing committee
For “Ultra Low Power Consumption Operation of SOA Assisted
Extended Reach EADFB Laser (AXEL).”
Published as: W. Kobayashi, N. Fujiwara, T. Shindo, S. Kanazawa,
K. Hasebe, H. Ishii, and Mikitaka Itoh, “Ultra Low Power Consumption Operation of SOA Assisted Extended Reach EADFB Laser(AXEL),” OECC/PS 2016, WD3-2, Niigata, Japan, July 2016.

Technical Committee on Communication Quality Research
Encouragement Award
Winner: Rie Tagyo, NTT Network Technology Laboratories;
Hideaki Kinsho, Osaka University; Daisuke Ikegami, NTT Network
Technology Laboratories; Takahiro Matsuda, Osaka University;
Akira Takahashi, NTT Network Technology Laboratories; Tetsuya
Takine, Osaka University
Date: July 26, 2016
Organization: Technical Committee on Communication Quality,
IEICE Communications Society
For “Inference of QoS Degradation Based on Spatial Dependencein Mobile Networks.”
Published as: R. Tagyo, H. Kinsho, D. Ikegami, T. Matsuda, A.
Takahashi, and T. Takine, “Inference of QoS Degradation Based on
Spatial Dependence in Mobile Networks,” IEICE Tech. Rep., Vol.
116, No. 10, CQ2016-1, pp. 1–6, Apr. 2016.

Papers Published in Technical Journals andConference Proceedings
Five Senses Theater: A Multisensory Display for the
Bodily Ultra-reality
Y. Ikei, K. Hirota, T. Amemiya, and M. Kitazaki
Emotional Engineering, Vol. 4, pp. 145–164, June 2016.
The present paper describes a multisensory virtual reality (VR)system built for the exploration of the bodily ultra-reality.

Development of Embodied Sense of Self Scale (ESSS):
Exploring Everyday Experiences Induced by Anomalous
Self-representation
T. Asai, N. Kanayama, S. Imaizumi, S. Koyama, and S. Kaganoi
Frontiers in Psychology, Vol. 7, 1005, July 2016.
The scientific exploration of the self has progressed, with muchattention focused on the Embodied Sense of Self (ESS). Empiricalstudies have suggested the mechanisms for self-representation. On
the other hand, less attention has been paid to the subjectivity itselfof the self. With reference to previous studies, the current study collected items that reflect the ESS and statistically extracted three factors for it: Ownership, Agency, and Narrative. The developed questionnaire [Embodied Sense of Self Scale (ESSS)] showed goodenough validity and reliability for practical use. Furthermore, ESSS
discriminated schizophrenia, a disorder of the ESS, from controls.
We discuss the factorial structure of ESS and the relationship among
factors on the basis of the current results.

Vol. 14 No. 9 Sept. 2016

Perceived Topographic Surface Modulated by Pitch Rotation of Motorized Motion Chair
T. Amemiya, K. Hirota, and Y. Ikei
Transactions of the Virtual Reality Society of Japan, Vol. 21, No.
2, pp. 359–362, July 2016 (in Japanese).
A great number of driving simulators with visual presentation havebeen developed. But little is known about the perception of a topographic surface induced by visual and vestibular stimuli when a user
runs over a bump or hole. In this paper, we conducted a user study toassess how congruence or incongruence of visual and vestibular
shape cues influence the perception of a topographic surface. Experimental result show that the vestibular shape cue contributed to making the shape perception more than the visual one. The result of alinear regression analysis showed that performance with visual unimodal and vestibular unimodal cues could account for that withvisuo-vestibular multimodal cues.

Event-based Transient Visual and Tactile Feedback Produces a Sensation of Impact
T. Amemiya
Transactions of the Virtual Reality Society of Japan, Vol. 21, No.
2, pp. 381–384, July 2016 (in Japanese).
This paper reports a design of a new haptic feedback technique fordesktop applications which creates a sensation of impact with modulated transient visual and tactile feedback. A transient vibration or
impulse tactile stimulus was presented when a computer mouse cursor made contact with a virtual object on the screen, while changing

2

Papers Published in Technical Journals and Conference Proceedings

the visual motion of the cursor. Two experiments were performed tocompare the effect of stimulus combination and find an effective time
lag of visuotactile stimuli to generate a clear sensation of impact.
Experimental evaluations showed that a sensation of impact was successfully induced by tactile stimuli of either single pulse or damped
oscillation, while a strong sensation of vibration was not induced, andthe sensation of impact was induced when tactile stimuli were presented 30–120 ms after the cursor made contact.

On Maximizing a Monotone k-submodular Function Subject to a Matroid Constraint
S. Sakaue
arXiv:1607.07957, July 2016.
In this paper, we prove that a greedy algorithm outputs a
1/2-approximate solution for monotone k-submodular maximization
with a matroid constraint. The algorithm runs in O(M|E|(MO + kEO))
time, where M is the size of an optimal solution, |E| is the size of theground set, and MO and EO represent the time for the membership
oracle of the matroid and the evaluation oracle of the k-submodular

3function, respectively.

Topographic Surface Perception Modulated by Pitch Rotation of Motion Chair
T. Amemiya, K. Hirota, and Y. Ikei
Proc. of HCI International 2016, pp. 483–490, Toronto, Canada,
July 2016.
The paper investigates multimodal perception of a topographic
surface induced by visual and vestibular stimuli. Using an experimental system consisting of a motion chair and optic flow on a wide
screen, we conducted a user study to assess how congruence or incongruence of visual and vestibular shape cues influence the perceptionof a topographic surface. Experimental results show that the vestibular shape cue contributed to making the shape perception larger thanthe visual one. Finally, the results of a linear regression analysis
showed that performance with visual unimodal and vestibular unimodal cues could account for that with visuo-vestibular multimodalcues.

NTT Technical Review