Enabling Technologies and Challenges in Coherent Transport Networks David Dahan, Ph.D. ECI Telecom Ltd

ʺ ʩʨɹ ʥʠʤɦ ʣhʤʬʱ ʰʫʤ 2014 OPTICAL ENGINEERING

ʡʤʩh̋ ʰʯʩʬʮʸ ʤʨy ʥʠʤʩʢʥʬʥhʫʨʥʤɦ ʣhʤʬʺ ʩʮʣ̫ ʠʤʤʬʬʫʮ ORT Hermelin College ʡʣ "ʲ ʹ ʺ ,'ʠʸ ʣʠʡʥ"ʫ ,ʣʭ ʥʩWednesday, February 26, 2014

Confidential , not for distribution

Drivers and Impact for Optical Networking Ecosystem

2

Shifting to the Cloud…Enterprise and personal IT are moving to

the cloud computing

Service Providers become “All Play” providers…

Technology challenges

Need more optical channel capacity :

100G/400G/1T

Other IP Traffic

IP Video Traffic

90%

Video and more Video….Internet streaming

2013 - IP at 5x 2008 levels with 90% Video

Dynamic Traffic Networks

Improve service provisioning, time and resource utilization :

SDT/ROADM/SDN

Slow Revenue Growth

Exponential Traffic Growth

Reduce cost /bit/switch/transport

Business challenges


Optical Network Evolution

2006

2008

2011

20122015-

SDH / Sonet Networks

Increase capacity Point-to-point CWDM/DWDM Up to 40 channels 2.5/10G channels

2.5GCWDM, DWDM

10G40 Channels

SDH / Sonet / EoS services support

Ring topology East/west protection Reconfigurable

OADM WDM over OTN 10G channels

40G80 Channels

IP over WDM Mesh topology ASON GMPLS-based ODU basednetworks 10G/40G channels,

ready for 100G coherent

Plug and play

40G/100GCoherent

100G Coherent networks support

DCFless networks Colorless /

directionless / contentionless

WSON GMPLS-based

400G/1TSuperchannel

Bandwidth on Demand

N:M ROADM configuration

Gridless ROADM 400G/1T

transceivers Fully automated

network

Continued demand for bandwidth from all applications

3

History and roadmap


From Direct Detection to Coherent Detection

4

Up to 10G (SE = 0.2 b/s/Hz)

40G non coherent solution (SE = 0.8 b/s/Hz)

40G/100G/200G coherent solution (SE > 2 b/s/Hz)

Intradyne Coherent detection

Phase and polarization diverse receiver Frequency Locked Lasers (<+/- 2 GHz) Digital Signal Processing at TX/RX

TXRX


Current 100G Coherent Transceiver architecture

5* Nelson et al, “A Robust Real-Time 100G Transceiver With Soft-Decision Forward Error Correction” J. OPT. COMMUN. NETW, vol 4, no. 11,2012

40 nm CMOS ASIC with 4 (8 bit resolution) x63 Gsamples/s ADC

Modulation format : DP-QPSK (Symbol Rate is ¼ Bit Rate : 2bit/s symbol x 2pol)

Integrated Coherent receiver

Integrated PDM QPSK MZM LiNBO3 Modulator


Ix

Qx

Qy

Iy

DSP block

ADCs

Coh. Rx

S

LO

90° Hybrid

& Detector

j

j Fre

quen

cy &

pha

se

reco

very

Slic

ing

Clo

ck r

eco

very

&

Inte

rpo

latio

n

Res

amp

ling

Sof

t S

ymbo

l es

timat

ion

SD

- F

EC

dec

oder

120G

OTU4112G

D>60000 ps/nm PMD>30 ps

Current 100G Coherent Transceiver architecture

6

6-8 bits 1 bit +reliability bit

infoGen Type Code FEC

Overhead

Pre-FEC BER TH. For post FEC<10-15

Coding gain [dB]

1st HD BCH (Bose-Chaudhuri-Hocquenghem) and RS (Reed-Solomon) codes

7% ~10-4 6-7 dB

2nd HD Concatenation of RS codes, Viterbi convolutional codes and BCH codes (CBCH)

7% ~1x10-3

(EFEC)8.5-10 dB

3rd SD BCT (Block Turbo code) or Turbo Product Code (TPC) and LDPC (Low Density Parity Check) codes

15%-20%

~2x10-2 10.5-11.5 dB


100G submarine Field trial over 4600 km

7

The 100G trial was carried out over Bezeq International’s live operational submarine fiber, in conjunction with the TeraSanta Consortium : demonstration of advanced capabilities of ECI 100G transmission system and technologies in compensating for non-linear channel impairments and chromatic dispersion utilizing advanced SD-FEC algorithms.

Apollo Platform100G

100G

DMUX

MUX


Next Generation of Coherent Transceiver : : Software Defined Transceiver (SDT)

8

Si Photonics IC with Electronic and Optical functionality

28 or 20 nm CMOS ASIC with DAC/ADC and DSP capabilities in both TX/RX

Power reduction Higher computational strength Adapt modulation format/Symbol

rate

Client Data Rate

100G/150G/200G/400G/1T

FEC overhead

0%-30%

Modulation format

BPSK/QPSK/8-QAM/16QAM

TXDSP

Pulse Shaping

Optical Carrier

Flexgrid tunable laser (C/L band)

Technol. Gate ADC

(8bits)DAC

(8bits)GA

28 nm150-200M

110-130 GS/s1.7W

110-130 GS/s0.7W

2013

20 nm200-250M

110-130 GS/s1.2W

110-130 GS/s0.5W

2014


New DSP features

■ Nyquist spectral shaping at TX : increases of the spectral efficiency by reducing the channel bandwidth to ~ symbol rate

9

1 2 3 4 5 6 7 8-4

-3

-2

-1

0

1

2

3

4

symbol index

In p

hase

sym

bol v

alue

Raised Cosine FIR filter

0 2 4 6 8 10 12 14 16 18-0.2

0

0.2

0.4

0.6

0.8

Tap index

Tap

coe

ffcie

nt


■ Self diagnostic monitoring features :■ Accumulated Chromatic Dispersion monitor

■ PMD monitor

■ OSNR monitor

■ ESNR monitor

■ Still missing : Efficient nonlinear compensation technique■ Current state of the art techniques based on digital back

propagation or Volterra Series are too complex for real time ASIC implementation

■ Nonlinear optical impairments are the ultimate limitations in optical network

10

New DSP features


Transmission Technology options for 400 Gb/s

11

Symbol Rate

Constellation size

Subcarriers/band

30 Gbaud

60 Gbaud

90 Gbaud

1

2

3

QPSK 8-QAM 16-QAM 32-QAM 64-QAM

Lim

itat

ions

of

DA

Cs/

AD

C a

nd

elec

tron

ics

Reach Limited <<100km

256-QAM

Modulation Gbit/s OSNR min [dB]

DP-QPSK 120 12.5

DP-16QAM 240 18.5

DP-16QAM 480 21.5

DP-256QAM 480 >30

4 1 bands with DP-256 QAM (30 Gbaud)Extremely high spectral efficiencyReach Limited (~100 km)

f

1x480G

2 bands with DP-16 QAM (30 Gbaud) High spectral efficiencyReach Metro /Long Haul distances

f

2x240G

f

4x120G

4 bands with DP-QPSK (30Gbaud)No spectral efficiency improvement over 100GSuitable for long haul (>2000 km)

1x480G

1 bands with DP-16 QAM (60 Gbaud)High spectral efficiencyReach Limited to Metro (~700 km)


0 20 40 60 80 100-25

-20

-15

-10

-5

0

5

10

Fiber Length [km]

Opt

ical

sig

nal p

ower

[dBm

]

Hybrid Raman Amplifiers

■ Complex Coherent modulation formats like 200G DP-16QAM require for 6-8 dB OSNR improvement with respect with current 100G DP-QPSK modulation format

■ The use of hybrid Raman-EDFA amplification schemes is required to improve the received OSNR or mitigate the nonlinear penalties by lowering the launched power into the fiber : can improve the transmission reach by 100%

12

Non linear impairments

Low OSNR 0 20 40 60 80 100

-25

-20

-15

-10

-5

0

5

10

Fiber Length [km]

Opt

ical

sig

nal p

ower

[dBm

]


Low OSNR

ROADMTX EDFA EDFA

L kmRX

x N times

ROADM EDFA

0 20 40 60 80 100-25

-20

-15

-10

-5

0

5

10

Fiber Length [km]

Optic

al sig

nal p

ower

[dBm

]


Low OSNR

With Hybrid Raman –EDFA amplification

Improving transmission reach


Superchannels

■ Future services of 400Gb/s and 1T will be packed into super channels, in order to provide optimum flexibility and reach performance tradeoffs :■ 400G : 2 channels spaced by 37.5 GHz

■ 1T : 5 channels spaced by 37.5 GHz

■ For optimized spectral efficiency, Super channels use Nyquist spectral shaping and Flexgrid WSS ROADMs

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Improving spectral efficiency beyond 100G


Flexgrid Networks

■ To increase spectral efficiency, we move from a fixed channel grid (50GHz/100GHz) to flexible channel grid management :■ 6.25 GHz grid

■ 12.5 GHz bandwidth granularity

■ The channel spectral slot is adapted on a per channel basis using :■ 10G/ 40G on 25 GHz slot

■ 100G and 200G on 37.5 GHz slot

■ 400G on 75 GHz slot

■ 1T on 187.5 GHz slot

14

Increase by 25 % the available useable fiber bandwidth

400G 1T100G

50 GHzf

Fixed 50GHz grid

10G40G

50 GHz

400G 1T100G

f

Flex grid

40G

10G


Flex Grid Technology enablers

■ Very stable tunable lasers compatible with 6.25 GHz grid resolution

■ Flexgrid ROADMs :■ First generation of WSS allocated a channel on a single MEM based pixel

■ Flexible WSS based on LCoS technology use a flexible matrix based wavelength switching platform with megapixel matrices allowing programmable channel bandwidth

15* EXFO Webinar : “400G Technologies: the new challenges that lie ahead”,04/02/2014http://www.exfo.com/library/multimedia/webinars/400g-technologies-challenges


■ Network node capabilities are enhanced with new features allowing full flexibility :■ Flexgrid : any channel/ superchannel can be directed

towards any other node

■ Colorless

■ Directionless

■ Contentionless

16

Fle

xgrid

WS

S

Optical Network Node with Full Flexibility


■ Network node capabilities are enhanced with new features allowing full flexibility :■ Flexgrid

■ Colorless : any wavelength can be added or dropped at any port

■ Directionless

■ Contentionless

17





■ Colorless

■ Directionless : any wavelength can be directed at any direction an reach a given port

■ Contentionless

18




■ Colorless

■ Directionless

■ Contentionless : Multiple channels of the same wavelength can be dropped or added by a single module

19


Optimum management of the optical spectrum resources

Optimized routing and resource allocation algorithms for flexible optical networking Conventional Routing and Wavelength Assignment (RWA) algorithms can

be used only for rigid grid networking New paradigms based on Routing and Spectral allocation Assignment

(RSA) algorithms should be developed for flexible grid networking Physical Impairment awareness and optimal combination of Software

Defined Transceiver parameters (modulation format/symbol rate, FEC overhead) will be required

20

Rigid grid networkFlex grid network

Need to find optimum strategies for spectrum

defragmentation


Software Defined Networking : Why ?

■ Bandwidth hungry services (video, mobile data, cloud services) lead to new traffic characteristics :■ Rapidly changing traffic patterns

■ High Pic to average traffic ratio

■ Large Data chunk transfers

■ Asymmetric traffic between nodes

■ SDN will turn the networks into programmable virtualized resource for better efficiency and automation

21

Flexible Multi-layer Networking

Confidential , not for distribution 22

Software Defined Networking

User I/FsNetwork

Apps

SND Control Plane

Open APIs

Multi layer netw

ork elem

ents

OpenFlow

Hardware Abstraction& Virtualization

Application requirementsDynamic connectivityBandwidthQoSResiliency

SDN Control PlaneAware of Application requirementOptimized resource and configuration

Flexible Multi-layer Networking

Multi layer Network Elements

Ethernet switch/MPLS routerOTN switch ROADM, SDT Fiber switch


Conclusion

■ The future optical transport networking will provide better■ Capacity : coherent modulation formats, superchannel, better SE

■ Flexibility : software defined transceivers, flexible grid, flexible CDC ROADMs nodes

■ Resource utilization : impairment aware- RSA algorithms, SDN

■ The future optical transport networking needs to provide :■ Efficient nonlinear optical impairment compensation techniques

■ Strategies for pro-active and re-active spectrum defragmentation and fragmentation awareness in service expansion and contraction policies

■ Energy efficient strategies

■ Capex and Opex reductions

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Documents

Enabling Technologies and Challenges in Coherent Transport Networks David Dahan, Ph.D. ECI Telecom Ltd