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大容量フォトニックネットワークのアーキテクチャ

長谷川 浩 佐藤 健一

名古屋大学 大学院工学研究科 電子情報システム専攻

〒464-8603 愛知県 名古屋市 千種区 不老町 E-mail: {hasegawa,sato}@nuee.nagoya-u.ac.jp

あらまし 本稿では、超大容量通信を実現するためのフォトニックネットワークのアーキテクチャについて解説

する。従来の IP 技術をベースにしたネットワークでは、パケット単位での経路制御を電気処理にて行うため、宛先

検索にかかるオーバーヘッドが通信容量を制限しかつ膨大な消費電力に直結していた。光ファイバ中の波長多重信

号の経路制御を、波長をラベルとし光信号のまま行うことにより、超低消費電力と大容量を実現するフォトニック

ネットワークが導入されつつあるが、コスト面やハードウェア規模の面から多数の光信号の経路制御処理は容易で

はなく、更なる大容量化は困難であった。本稿ではフォトニックネットワークの現状と課題について述べ、ボトル

ネックであるフォトニックノードの容量を向上させるためのアーキテクチャを解説する。 キーワード フォトニックネットワーク 階層化光パス エラスティック光パス フォトニックノードアーキテク

チャ

Architectures of Bandwidth Abundant Photonic Networks

Hiroshi HASEGAWA Ken-ichi SATO

Dept. Electrical Engineering and Computer Science, Nagoya University

Furo-cho, Chikusa-ku, Nagoya 464-8603 Japan E-mail: {hasegawa, sato}@nuee.nagoya-u.ac.jp

Abstract In this manuscript, we present architectures of photonic networks to realize bandwidth abundant optical transport. Current IP-based networks are suffered from the energy consumption and the capacity limitation caused by the packet-by-packet forwarding in the electrical layer. This fact motivates the introduction of photonic networks that utilize wavelength routing in the optical layer. The elimination of costly E/O and O/E conversion and the routing in the optical layer makes photonic networks energy efficient and capacity abundant. However, due to the difficulty in realizing large scale optical switches, further capacity enhancement is not straightforward. We elucidate the current situation and issues in photonic networks and then show novel node architectures that can achieve larger capacity cost-effectively.

Keyword Photonic Network, Hierarchical Optical Path, Elastic Optical Path, Photonic Node Architecture

2010 2008 2006 2004 2012 2002 2000 1998

JPIX (Japan Internet Exchange) (1998-2012) ( )

2003 2004 2005 2006 2007 2008 2009 2010 2011

1.696Tbps (2011/11)

0.669Tbps (2011/11)

• (+30-40%/ ).

•

•

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000PB/Month

File Sharing

Internet Video

Web/e-mail/data

VoIP Online gaming

2011 2012 2013 2014 2015 2016 Cisco VNI, “Global Consumer Internet Traffic, 2011-2016”

– -

3

’10 ’11

4

( )

(YouTube)

9.7 29.3%

26.8 33.6%

14.1 21.6%

2360 2900

5

iPhone3 : 480 x 320 iPhone4 : 960 x 640

HDTV: 1920 x 1080

(DVD : 720 x 480)

2560 x 1600 (6.1inch)

3840 x 2160 (Sharp 32inch)

Ultra HDTV : 7680 x 4320 (NHK, 145inch PDP)

4K Cinema

Raw data: 72Gbps

Introduction of 3D tech.

(ADSL, FTTH)

7

8k/4k Digital cinema Layer one VPNex. Just-in-time, Optical mesh network

-ex. UHD-TV, 3D-TV, 8k/4k Digital cinema

1990’s

2000’s 2020’s

Ultra-High Definition TV 72Gbps( )

2010’s

web

/

+30-40% = 15

=

9

( ) &

10

11

(DSP ) 100Gbps/

100+Tbps/

D. Qian, “101.7-Tb/s (370 294-Gb/s) PDM-128QAM-OFDM Transmission over 3 55-km SSMF using Pilot-based Phase Noise Mitigation, ” OFC/NFOEC, PDPB5, Mar. 2011. J. Sakaguchi et.al., “19-core fiber transmission of 19x100x172-Gb/s SDM-WDM-PDM-QPSK signals at 305Tb/s,” OFC/NFOEC,PDP5C.1, Mar. 2012.

(“Capacity Crunch”, )

OFDM / Nyquist WDM

JPN48

8090100

110

120131132

140

190

200

220

210

230240

260

270280

290300

250

180

10

20

30

40

50

60

70

8090100

110120

131132140

150160170

180190

200

210

220230

240250

260270280

290300

310320

330340350

360370

380390

400410

420 430440

450460

470

Ver.2013.06.06

13

( )

( )

15

“HIKARI”

16

( )

( )

LSR O/E O/E O/E O/E

E/O E/O E/O E/O

WXC

WXC: Wavelength Cross-Connect LSR: Label Switch Router

17

OXC /ROADM

OXC /ROADM

OXC /ROADM

OXC /ROADM

OXC /ROADM

OXC /ROADM

Traffic increase Traffic increase Traffic increase

1. Link cost ( ) = OFDM 2. Node cost ( ) =

Link cost Node cost

19

Conventional ITU-T Grid

Elastic Optical Path

Network

50GHz

12.5 GHz Designate a set of frequency slots

Elastic channel spacing Adaptive modulation

Residual bandwidth wasted

frequency

frequency

10Gbps 40Gbps 100Gbps 40Gbps

400Gbps, 1Tbps

0

2

6

8

10

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 # of hops

# of

freq

uenc

y slo

ts

By introduction of frequency slot and OFDM

1 slot : 12.5GHz

4

QPSKITU-T nonDA-SLICE DA-SLICE

16QAMQPSK

Transmission distance

Band

wid

th

QPSK

QPSK

QPSKBy introduction of distance adaptive Modulation4

22

• “(RWA)” “(RSA)”

•

•

23

( )

Fiber

Wavelength collision

A B

C D No.3

No.2 No.1

No.2

No.1 No.3

24

( )

A B

C D

No.2

No.3 No.1

No.2

No.3

(i.e. )

Finding a coloring that minimizes the number of colors used. => NP-hard Finding a coloring that minimizes the number of fibers used subject to given color set. => NP-complete

No.1

25

Iterative ILP based Route Assignment [T.Takagi et.al., ECOC2010]

•

•

•

=>

29

[T.Takagi et.al., ECOC2010]

Average number of connection demands

0

200

400

600

800

1000

1200

1400

1 2 3 4 5 6 7 8 9 10

Num

ber o

f fib

ers

ITU-T grid method

nonDA-SLICE method

DA-SLICE method

Average number of connection demands

0

200

400

600

800

1000

1200

1400

1 2 3 4 5 6 7 8 9 10

Num

ber o

f fib

ers

ITU-T grid method

nonDA-SLICE method

DA-SLICE method

Link cost reduction by path elasticity (static)

18%

50%

6x6 mesh network Bandwidth of one fiber : 4, 400 GHz ITU-T grid bandwidth : 100 GHz Frequency slot : 12.5 GHz

# of slots necessary for shortest route ITU-T grid spacing

Without fragmentation

30

nonDA-SLICE : elastic optical path networks without distance adaptive modulation

Ratio of Accommodated Traffic

Because of the increase in # of wavelength candidates

7x7 polygrid topology

Acc

epte

d tra

ffic

dem

and

(nor

mal

ized

)

0 0.2 0.4 0.6 0.8

1 1.2 1.4 1.6 1.8

2 2.2 2.4

ITU-T nonDA-SLICE DA-SLICE

COST266 topology

Acc

epte

d tra

ffic

dem

and

(nor

mal

ized

)

0 0.2 0.4 0.6 0.8

1 1.2 1.4 1.6 1.8

2 2.2 2.4 2.6 2.8

ITU-T nonDA-SLICE DA-SLICE

The degradation due to the non-uniform path capacity is marginal.

32

[T.Takagi et.al., OFC2011]

10G 40G 100G

1

100

80

40G x 80 = 3.2T

100G x 100 = 10T Nonlinear Shannon limit Nonlinear impairments

Available bandwidth (ex. C+L)

400G

400G x 60 =24T

Transparent optical reach? Transponder cost?

Traffic: +30%/year 33

LSR O/E O/E O/E O/E

E/O E/O E/O E/O

WXC

1st stage : Bottleneck and prevent the constructing cost-effective networks

:

WXC: Wavelength Cross-Connect LSR: Label Switch Router

37

WSS 1

add drop

…… ……

: WSS

WSS

(LCOS )

(Wavelength Selective Switch)

Finisar 1x9 WSS (140mm x 220mm) 38

1x20WSS

The issues

WXC / ROADM

WXC: Wavelength Cross-Connect

optical fiber

WXC / ROADM

optical fiber

39

&

Ex.) VC-3/4 in SDH/SONET

VC-3/4 VC-1/2

A possible solution

41

( )

(2000 ~)

Grouped Routing Entity based Optical Networks (2011 ~)

2-stage Routing Optical Networks (2011 ~)

( )

add/drop

add/drop

Subsystem modular OXC Node Architecture (2011 ~)

OXC

BXC

WXC

WXC

optical fiber waveband path

wavelength path BXC: WaveBand Cross-Connect

Waveband Path = a group of wavelength paths

42

WXC

Hierarchical Optical Path Network Waveband Path = a group of wavelength paths

BXC

WXC

BXC: WaveBand Cross-Connect

• Reduce port counts• Large capacity optical paths

Single-layer

Hierarchical

waveband path

WXC WXC WXC

WXC

BXC

WXC

BXC

WXC

BXC

wavelength path

Optical Fiber Waveband Path

Wavelength Path

43

Benefit of Wavebands

87654321

04

812

16

0.5

1.5

1

2

2.5

Ratio of the total number of switch ports in the networks (R: Hierarchical/Single Layer)

0.5

1.5

1

2

2.5

0

waveband hops, H

bandwidth, W

Number of optical switch ports decreases

over a wide area

44

0

0.5

1.0

1.5

2.0

0 1 2 3 4 5 6 7 8 Average number of wavelength paths between node pairs

Nor

mal

ized

netw

ork

cost

Hi

erar

chic

al /

Sing

le-la

yer n

etw

ork

Performance Evaluation [I.Yagyu et.al. 2008]

) BPHT : X.Cao et al., IEEE J-SAC ,2003

end-to-end BPHT ( )

Proposed

Single-layer

OFC2010 Post-deadline Paper 4/6 , , , ,

( ) (NTT ) (NTT ) 2010

BXC

WXC

WXC

optical fiber waveband path

wavelength path BXC: WaveBand Cross-Connect

Waveband Path = a group of wavelength paths

47

WXC

Grouped Routing Scheme

48

( )

Add/drop( )

Grouped Routing Entity (GRE)= The bundle of wavelength paths used for coarse granular routing

(GRE).BXC GRE

GREGRE

(“GRE ”)

Grouped Routing= Coarse granular routing with Fine granular add/drop

…

…

1x2 WSS 1x2 WSS or SC

Coupler

GR-OXC

1xN WBSS… ……

…

GRE

Dropped Wavelength path

AddedWavelength path

Wavelength path

GR-OXC

fiberSource

DestinationGRE pipe

No termination functions are definedGRE pipe is NOT “path” of ITU-T definition

GRE pipe

Virtual pipes carrying multiple wavelength paths connect multiple nodes.Wavelength paths can be added/dropped to/from virtual pipes at any arbitrary node.

Wavelength path

Any node can accommodate multiple wavelength paths having different s-d node pairs into a GRE pipe.

Grouped Routing Scheme

51

Wavelength Selective

Switch, WSS

WSS 2005

52

Brussels

COST266 network

Max degree

Req. on WBSS’s spec [K.Takaha et.al. 2013]

54

Higher degreePan-European network (COST266)

More wavelength paths 88 + 8 wavelengths 50GHz spacing( C-band + a part of S-band, L-band )

Broader WB/GRE capacityCompact implementation

Number of nodes 26

Node degree Min 2 Max 8 Ave. 3.92

Number of links 51

Link distance Min 200 Max 1712 Ave. 627.2

Hop count

Min 1 Max 6

Ave. 2.76 M : wavelengths of GRE capacity

Ratio of requred path # of selective switch † † Y.Taniguchi et al., JOCN 2013

Proposed 1x8 WBSS

55

Property Valuecenter wavelength error ‐0.04 to 0.02 (nm)

insertion loss 4.47 to 7.69 (dB)channel loss deviation

in each output loss 1.56 to 2.10 (dB)

polarization dependent loss 0.02 to 0.41 (dB)1dB channel bandwith > 0.10 (nm)3dB channel bandwith > 0.18 (nm)

adjacent crosstalk < ‐ 37.03 (dB)non‐adjacent crosstalk ≤ ‐ 37.67 (dB)

coherent crosstalk ≤ ‐ 32.19 (dB)1x8 cyclic AWG 1x8 Optical switch

WB1switch

WB3switchWB4

switchWB5

switchWB6

switchWB7

switchWB8

switch

WB2switch

z

WBSS

Transmission characteristics

Adaptation to 50 GHz spacing signals Larger WBSS Scale (1x5 WBSS → 1x8 WBSS)

by very small increase of WBSS PLC chip’s size

チップサイズ74.6mm x 48.4mm

Proposed 8x8 WBXC

56

8x8 WBXC

Optical coupler WBSS

Four WBSSs module 1x8 WBSS chip

Compared to previous device (5x5 WBXC) Number of ports   Size of WBXC module Capacity of wavelengths 

Specifications 8x8 WBXC 96 wavelengths / fiber

•50 GHz spacing on ITU-T grid• 8 wavebands / fiber•12 wavelengths / waveband

Throughput 7.68 Tbps

30 mm

:     1.60 times:     0.68 times:     1.50 times

チップサイズ74.6mm x 48.4mm

Experiment:spectra

57

まとめ

58

結論

通信量は依然として増加している(+30‐40%/年)。

エネルギー消費・装置コストには限度がある。

超低消費電力かつ超大容量を実現する上では、フォトニックネットワークを導入していくことが必要である。

フォトニックネットワークの導入では、依然として高価な装置コストをどのように抑制するかが鍵である。

限定的な能力しか持たない装置・ネットワークと、その特性を考慮した最適化手法を組み合わせることで大きな性能アップを実現できる。

ネットワークアーキテクチャ・新たな光デバイスの開発により、大幅な容量拡大が可能となった。 59

ご清聴ありがとうございました!!

60

謝辞：本研究の一部は KAKENHI (23246072)およびSCOPE により実施された。