Modulation Formats Which Approach the Shannon …...Sakamoto, Sano, George Mdlti f tModulation...

Modulation Formats Which Approach the Shannon LimitShannon Limit

Andrew D. Ellis

Photonic Systems Group, Tyndall National Institute / Dept. of PhysicsUniversity College Cork – Irelandy g

[email protected]

www.tyndall.ie

OMM4.pdf © 2009 OSA/OFC/NFOEC 2009

978-1-55752-865-0/09/$25.00 ©2009 IEEE

2 Acknowledgements

• For help with putting the talk together:p p g g– Fatima C. Garcia Gunning, Selwan K. Ibrahim, Jian

Zhao, Emanuel Popovici, Christian Spagnol.• For material and support:

– Sebastien Bigo, Masataka Nakazawa, Itsuro Morita, Akihide Sano Selwan Ibrahim Peter Winzer JianjunAkihide Sano, Selwan Ibrahim, Peter Winzer, Jianjun Yu, Joseph Kahn, Etsushi Yamazaki, Akimasa Kaneko.

• For financial backing

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3 Symbols and Acronyms

EDFA: Erbium doped fibre amplifierWDM: Wavelength division multiplexingFEC: Forward error correctionC+L: Particular amplification wavelengths

C: Channel capacityB: Channel bandwidthN0: Noise spectral density

PDH: Plesiochronous Digital HierarchySDH: Synchronous Digital HierarchyIP: Internet ProtocolQAM: Quadrature Amplitude ModulationSSB: Single side band

Pb: Bit energysnr: Signal to noise ratioQ(x): Q function for a Gaussian random

variableSSB: Single side bandASK: Amplitude shift KeyingPSK: Phase shift keyingm: number of constellation pointsBER: Bit error ratio

Es: Energy value to quantify size of a constellation

Eb: Mean energy of a symbolei: Complex field value

LDPC: Low Density Parity CheckOSNR: Optical signal to noise ratioASE: Amplified spontaneous emissionDSP: Digital signal processingDFB: Distributed feedback laser

�: Wavelengthc: Speed of lightNamps: Number of amplifiersG: Amplifier gainDFB: Distributed feedback laser

MZM: Mach Zehnder modulatorRZ: Return to ZeroDPSK: Differential PSKCS: Carrier suppressedP l P l i ti

p gnsp: Spontaneous emission factorh: Plank’s constant�: FrequencyD: Dispersion

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Pol: PolaraisationOFDM: Orthogonal frequency domain multiplexingCoWDM: Coherent WDMASIC: Application specific integrated circuit

D: Dispersion�: Nonlinear coefficientLeff: Effective length

4 A small selection of related sessions

Short Courses Workshops Tutorials Sessions/Invited Speakers

Communication Digital Coherent FranceschiniCommunication Theory

Digital Coherent Receivers.

Franceschini

FEC Kschischang

Non linear effects Modeling & Design Electronic Signal Capacity Limits of Nakazawa BigoNon-linear effects Modeling & Design Electronic Signal Processing and the Design of Optical Transport Systems

Capacity Limits of Fibers.Impact and Mitigation of Non-Linear Effects.

Nakazawa, Bigo, Fuerst, Shieh, Sun, Sakamoto, Sano, George

M d l ti f t WDM i L H l Si l C i VModulation formats WDM in Long-Haul Modulation Format

Single-Carrier Versus Multiple-Carrier Modulation Formats for WDM Systems

New Technologies Photonic ICs 100Gbit/s for $100 Photonic Crystal Fib

Prevost, Brès, Krauss, K k Kl kiElectronic Circuits Fibers. Kaneko, Klamkin, Morse, Hauske, Yoo, Clarke,

Reinforce Consolidate Build on Highlight

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5 Introduction

• Trends in optical communicationTrends in optical communication• Shannon limit

Generic communication theory– Generic communication theory– Forward Error Correction CodesO ti l S t• Optical Systems– Capacity limit for non-linear systems– Multi-level modulation formats– Breaking the current limit

www.tyndall.ie

6 Maximum capacity (research)

1,000,000

m)

10,000

100,000

ct (T

bit/s

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1,000

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rodu

c

WDM

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10

100

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e D

ista

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OTDM-DDWDM-DDSoliton-DD

EDFA

Coherent Detection

WDM

0

1

83 85 87 89 91 93 95 97 99 01 03 05 07 09 11 13 15 17 19 21 23

Bit

R TDM-DD1550nm

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User Demand

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1M

10M

100M

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e (b

it/s)

10k

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Acc

ess

R

100

1k

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Year

8 Network Architecture

100G 105

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9 Switching Capacities

100G 105

10Tbit/s

1G

10G

1041Tbit/s

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s R

ate

ity

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10M

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itch

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101

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R

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1975 1980 1985 1990 1995 2000 2005 2010 2015

Year

10 Introduction



www.tyndall.ie

11 Shannon Limit

• Shannon’s Second Theorem – The Noisy Channel yCoding Theorem

– C.E.Shannon, “A Mathematical Theory of Communication”, Bell Syst. Tech. J., 27, pp379-423 & pp623-656

– “Reliable communication over a discrete memory-less channel is possible if the communication rate R satisfies R < C, where C is the channel capacity. At rates higher than the capacity, reliable communication is impossible.”communication is impossible.

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Information Spectral Density of ideal memory-less AWGN channel

n C

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per

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1.0

0.5

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0 10 20 30

0.2

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SNR (dB)

13 Calculation of required SNR

• Linear (coherent) detectionLinear (coherent) detection • Hard decision • Assume memory-less AWGN channel• Assume memory less AWGN channel• Signal-independent noise

– Thermal noise, local oscillator shot noise limited systeme al o se, local osc llato s ot o se l ted syste

• Calculate probability that each bit “escapes”

www.tyndall.ie

14Calculation of required SNR

1: Bit Error RateQuadrature

Decision Threshold

In-phaseab

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1: Signal to Noise RatioQuadrature

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16 Information Spectral Density

Information Spectral Density of ideal memory-less AWGN channel

10 0

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pola

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1 bit per symbol

acity

per

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0 10 20 30

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SNR (dB)

17 Extending to higher order modulation

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20 Calculating modulation scheme performance

1. Calculate minimum distance (e1-e2, 2�Es)( 1 2, s)2. Determine symbol noise level (No)3. Calculate BER using symbol probability and effective

number of boundaries4. Calculate energy per bit Eb as a function of Es

5 Substitute E for E and snr for E /N to give BER as a5. Substitute Eb for Es and snr for Eb/N0 to give BER as a function of snr

6. Calculate ISD from number of levels and symbol yprobability

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21 Signal Constellations

ASK QAM

PSK

www.tyndall.ie

PSK

22Information Spectral Density of common

multi-level modulation formats

SSB-QAMSSB PSKn

C/B

SSB-ASKSSB-Bi-Polar ASKSSB-PSK

pola

risat

io

Increasing number of levels

acity

per

p

SNR (dB)

BER = 10-12

Cap

a

www.tyndall.ie

SNR (dB)

23Impact of Optical Demultiplexing and

Practical Optical Modulation

20% Guard Band for FilteringDouble Side Band Modulation for ASK and PSK

Orthogonal QAMn C

/B

Orthogonal QAM

ASKBi-Polar ASK

QAMPSK

olar

isat

ion

ASK

acity

per

po

BER = 10-12

20% filter margin

Cap

a

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SNR (dB)

24 Fundamental limits1

• Unconstrained modulation (amplitude + phase) with direct detection

C � snrBC

�� 1log2• Phase modulation with coherent detection

� 11log1�� snrC

• Unconstrained modulation (amplitude + phase) with coherent detection

� 1.1log2 2 �� snr

B( p p )

� 0.1log21

2 �� snrBC

www.tyndall.ie

� 2 2B

1: J.M.Kahn, K-P.Ho, JQE 10 2 pp259 (2004)

25 Fundamental Limits2

� ��

��22

1 xErfcxQDefinition

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snrm

mQmmPe 1

)(log.612 22Bi-polar ASK

�� mm 1

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i

rre

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Uni-polar ASK

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msnrQsnrQ

snrQ

Pe 42

,

2

22112

2

��

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�PSK (low BER)

www.tyndall.ie1: J.G.Proakis, Digital Communications (4th Edition) McGraw-Hill (2000)

� � otherwisem

SinmsnrQm

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22

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26 Bibliography – 1:Communication Theory

1. H.Nyquist, AIEE Trans. 47pp617 (1928)2. C.E.Shannon, Bell Syst. Tech. J., 27 pp379- (1948)3. J.J.Bussgang et.al., Trans. Comm. Systems 12 pp18- (1964)4. J.G.Proakis, Trans. Comm. Tech., 16 pp71- (1968)5 H A Haus JQE QE 23 pp212 (1987)5. H.A.Haus, JQE, QE-23 pp212 (1987)6. S.Haykin, “Digital Communications”, Wiley (1988)7. J.M.Geist, Proc MILCOM 1990, pp768- (1990)8. J.P.Adis et.al., Trans.Inform.Theory, 39 pp184- (1993), y, pp ( )9. J.G.Proakis, Digital Communications (4th Edition) McGraw-Hill (2000) 10. J.Rebola et.al., Proc SPIE 4087 pp49- (2000) 11. Mecozzi et.al., PTL, 13 pp1029- (2001)12. J.M.Kahn, K-P.Ho, JQE 10 2 pp259- (2004)13. K.P.Ho, PTL, 17 pp858- (2005)14. E.Ip et.al., JLT, 23 12 pp4110- (2005)15 E Ip et al Optics Express 16 2 pp753 (2008)

www.tyndall.ie

15. E.Ip et.al., Optics Express, 16 2 pp753- (2008)

27 Introduction



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28Error Correction Codes

Current Status

Binary FECencoder

MappingUp-conversion(modulation)

10110 1011010 a+jb

encoder (modulation)

Down-conversion(receiver)

DemappingBinary FEC

decoder

a’+jb’101001010110

www.tyndall.ie

LO

29 Forward Error Correction

Orthogonal QAM

C/B

g

1st Generation: Reed Solomon

Overhead

3rd Generation: Block Turbo Codes2nd Generation: Concatenated Codes

BER = 10-12

20% filter marginCoding Gain

www.tyndall.ie

SNR (dB)

30Error Correction CodesSoft decision decoding

Binary FECencoder


10110 101101 a+jb


• Eg Low Density Parity Check (LDPC) Codes– Within 0.005 of Shannon limit (100% overhead)


DemappingSoft DecisionBinary FEC

decoder

a’+jb’70531710110

www.tyndall.ie

LO

31 Performance of RS & LDPC codes1

100

10-1

10-6

10-2

10-3

rror

Rat

e

Reed Solomon

C

10-4

10 5

Er

LDPC

3 4 5 6 7 8 9 10

10-5

10-7

www.tyndall.ie1: B.Zhou, et.al., Information theory and Applications Workshop, 2008

Eb/N0

32Error Correction Codes

Current Status

Binary FECencoder


10110 101101 a+jb


• Multi-level (c.f. binary) coded LDPC• Additional refinements for soft decision based systems


DemappingLDPC overGalois Field

a’+jb’10110

www.tyndall.ie

LO

33 Short LDPC codes over GF(q) 1

• LDPC over GF(q) easily outperform same length binary codes (length n=720)

• Moreover they perform as well as much longer gbinary codes (n=5760)

www.tyndall.ie1: C.Spagnol Ph.D. Thesis: Aspects of LDPC codes for hardware implementation

34 Bibliography –FEC

1. G.D.Forney et.al., J.Select.Areas Commun., 7pp941- (1989)2. S-Y Chung, IEEE Commun Lett., 5 pp58- (2001)3. P.V.Kumar et.al., “Optical Fiber Telecommunications IV B” Academic (2002)4. T.Mizuochi, OFC2003, paper PD21 (2003)5 B Vasic et al JLT 21 pp438 (2003)5. B.Vasic et.al., JLT, 21 pp438- (2003)6. C.Berrou, IEEE Commun Mag., 41 pp110- (2003)7. C.Spagnol Ph.D. Thesis: Aspects of LDPC codes for hardware implementation8. B.Zhou, et.al., Information theory and Applications Workshop, 2008, , y pp p,

www.tyndall.ie

35 Introduction



www.tyndall.ie

36 Signal to Noise Ratio in Optical Systems1

• Capacity limits expressed in terms of SNR = Eb/N0p y p b 0

• Convert to optical signal to noise ratio OSNR =Ps/Pn

RE 2�c

RNEOSNR b

..2.

0 ��

nmnmsGbitdBdBdB OSNRSNR 1.0,1550,/6.104�

• Noise accumulation well known

� �� 1 hnGNP l i iN � �� ....1. hnGNP spampsonpolarisatiN

Add input insertion loss to gain

www.tyndall.ie1: J.M.Kahn, K-P Ho, JQE 10 2, pp259 (2004)

Add input insertion loss to gain

37 Capacity limit for a 2,000km optical system

8Hz/

pol)

~ Damage threshold O ti t ll tiHz/

pol)

6

8

y Li

mit

(b/s

/H ~ Damage threshold

Limit ~ 6 b/s/Hz

Optimum constellationPSK signalDirect Detection

8

10

12

14

y Li

mit

(b/s

/H

2

4

ctra

l Effi

cien

cy

2

4

6

ctra

l Effi

cien

cy2000km, 80km spacing, 4.5dB noise figure, 20% guard bands,

50GHz channel spacing

1.00.5 2.00.2 5.00.1 10.0

Transmitted Power Density (W/THz)Spe

c

1´ 104100 200 500 1000 2000 5000

System Reach (km)S

pec

80km spacing, 4.5dB noise figure, 1dB input loss, 500mW over C band, 50GH h l i50GHz channel spacing 50GHz channel spacing

But optical communication links are characterised by a distributed nonlinear response

www.tyndall.ie

38Origin of fundamental capacity limit for

optical fibres1,2,3

T 1

Rx-2

R 3

DSP

Tx-1 Rx-3

Rx-1Tx-2Tx-3

Rx-1x N DSP

• Per channel DSP– Dispersion (Chromatic + Polarisation)– Coherent Detection– Self Phase Modulation Correction3

• But not non-linear mixing between signal & ASE (early dispersion maps)But not non linear mixing between signal & ASE (early dispersion maps)• Multiple transmitters

– Don’t actually communicate– Are not always co-located

Inter channel nonlinearity gives the fundamental limit

www.tyndall.ie1: P.P.Mitra, J.B.Stark, Nature, 411, pp1027, (2001)2: L.G.L.Wegener et.al., Physica D, 189, pp81, (2004)3: R-J, Essiambre et.al., ECOC 2008, We1E1(2008)

• Inter channel nonlinearity gives the fundamental limit

39Example of simple receiver based

nonlinearity compensation.

CoherentCoherentReceiver

www.tyndall.ieK.Kikuchi, Optics Express, 16 2 pp889- (2008)

40 Cross phase modulation

• Signal processing to mitigate SPM• Dispersion management to reduce signal –ASE interaction

All other channels act as noise so rces to a elength of interest• All other channels act as noise sources to wavelength of interest• Appropriate Dispersion Map

– High local dispersion to degrade phase matching– Dispersion management to control PAPDispersion management to control PAP– Sufficient residual dispersion per span– Dispersion map is key

Quadrature

In-phase

www.tyndall.ie

41 Impact of cross phase modulation

• Random walk process– Sub-linear accumulation with number of amplifiersp

• Depends on dispersion map• Proportional to fibre non-linearity and effective length

effa

XPM

LNDBI

��

��

2ln.2

..2�

�

• Adds noise to the signal

IP

PePPPP XPM

S

��

��

�

1 sNXPMNN PePPPP ��

�� 1

• Leaches power from the signalP

www.tyndall.ie1: P.P.Mitra, J.B.Stark, Nature, 411, pp1027, (2001)

XPM

SIP

sS ePP�

�

42 Four Wave Mixing1

• Similar treatment to XPM• Is dominant for PSK with certain dispersion maps (constant intensity)

DB ��

1cnqp

effa

XPM

LNDBI

��

��

2ln.2

..2�

��

2

0,

1qp

qpA

FWM

NI � 2222

22

.2 cpqfD

Dpq

�� !

�

qpqp

Dpq

,2,1

• XPM typically dominates and is considered hereafter• XPM typically dominates and is considered hereafter.

www.tyndall.ie1: J.M.Kahn, K-P Ho, JQE 10 2, pp259 (2004)

43 Capacity limit with non-linear transmission

8

z/po

l)

G l

Linear

6

mit

(b/s

/Hz

Coherent Detection

Goal

Non-Linear

4

icie

ncy

Lim

Linear

2

pect

ral E

ffi

Direct Detection

Non-Linear

1.00.5 2.00.2 5.00.1 10.0

Transmitted Power Density (W/THz)

Sp Direct Detection

www.tyndall.ie


2000km, 80km spacing, 4.5dB noise figure, 50 GHz channels at 50 baud

44 Numerical simulations

l) 8y

Lim

it (b

/s/H

z/po

4

6

8Linear

Spe

ctra

l Effi

cien

c

2

4Non-Linear

www.tyndall.ie

Transmitted Power Density (W/THz)0.01 0.1 1 10 100

R-J Essiambre et.al., OFC2008 paper OTuE1 (2008)

45 Bibliography –Nonlinearity and its mitigation

1. D.M.Pepper et.al., Opt.Lett., 5 pp59- (1980) 2 J P G d t l O t L tt 15 1351 (1990)2. J.P.Gordon et.al., Opt.Lett., 15, pp1351 (1990)3. S.Watanabe et.al., JLT, 14 3 pp243- (1996)4. A.Mecozzi et.al., PTL, 12, pp392, (2000)5. X.Liu et.al., Opt. Lett., 27, pp1616 (2002)6. K-P.Ho et.al., JLT, 22 pp779 (2004)7. D-S Ly-Gagnon, Proc OECC/COIN2004, paper14C3-3 (2004)8. K-P.Ho, “Phase modulated optical communication systems”, Springer, (2005)9 G Charlet et al ECOC 2006 paper Th4 3 4 (2006)9. G.Charlet et.al., ECOC 2006, paper Th4.3.4 (2006)10. G.Zhu et.al., PTL, 18 pp1007 (2006)11. D.Boivin et.al., J.Opt.Soc.Am.A B 23 pp2019 (2006)12. K.Kikuchi et.al., OFC 2007, paper OTuA2 (2007)13 A J L PTL 19 1556 (2007)13. A.J.Lowery, PTL, 19 pp1556 (2007)14. A.J.Lowery, Optics Express, 15 pp12965 (2007)15. E.Ip et.al., Optics Express, 16 2 pp753- (2008)16. K.Kikuchi, Optics Express, 16 2 pp889- (2008)

www.tyndall.ie

p p pp ( )

46 Bibliography –Non-linear Limit

1. P.P.Mitra &J.B.Stark, Nature, 411 pp1027 (2001)2. J.B.Stark et.al., Opt.Fiber Technol., 7 pp275- (2001)3. J.Tang, JLT, 19 pp1104- (2001)4. E.E.Narimanov et.al., JLT 20 pp530- (2002)5 K S Turitsyn Phys Rev Lett 91 20 pp203 (2003)5. K.S.Turitsyn, Phys.Rev.Lett., 91 20 pp203- (2003)6. L.G.L.Wegener et.al., Physics D, 189 pp81- (2004)7. J.M.Kahn et.al., J.Sel.Top.Quantum Electron, 10 2 pp259- (2004)8. J.M.Kahn et.al., ECOC 2005 paper Th2.2.1 (2005), p p ( )9. E.B.Desurvire, JLT, 24 12 pp4697- (2006)10. R-J Essiambre et.al., OFC2008 paper OTuE1 (2008)11. R-J, Essiambre et.al., ECOC 2008, We1E1(2008)

www.tyndall.ie

47 Introduction



www.tyndall.ie

48 Progress towards the capacity limit

Coherent Detection Direct Detection

ol)

ol)

Linear

ficie

ncy

(b/s

/Hz/

po

ficie

ncy

(b/s

/Hz/

po

span

Non-linear

Linear

Non-linear

Spe

ctra

l Eff

Spe

ctra

l Eff span

Transmission distance (Mm) Transmission distance (Mm)

www.tyndall.ie

Solid lines calculated for; 80km spacing, 4.5dB noise figure, 50 GHz channels at 50 Gbaud, Optimum powerDots plotted for notable experimental results, per polarisation

49Direct Detection 1: Filtered CS-RZ DPSK2

8,000km 0.8 b/s/Hz

• Long Haul Transmission (mitigate non-linearity)

Im

– RZ format – dispersion management

• For spectral efficiencyDPSK for sensitivity benefit

Re

– DPSK for sensitivity benefit– Pre-filtering for SSB– FEC

DFB MZM 50/100 GHz ol)

PSKSSB-PSK

DFB MZM 50/100 GHzInterleaver

ncy

(b/s

/Hz/

p

ASK

ectra

l Effi

cien

www.tyndall.ie1: I.Morita, N.Edagawa, ECOC 2003, PDP page 60 (2003)

Spe

SNR (dB)

50Direct Detection 2: Coherent WDM1

1,200km 1 b/s/Hz

• High Capacity Transmission – Low symbol rate (impairments)

Im

• For spectral efficiency– Orthogonal Carriers– FEC

�mod

Re

Laser MZM MZM

~

��

modmodmodmodmod

mod

ol)

CoWDM

�mod

ncy

(b/s

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p

ASK

ectra

l Effi

cien

www.tyndall.ie1: T. Healy, et.al., ECOC’07, Mo1.3.5 (2007).

Spe

SNR (dB)

51Direct Detection 3: PM-QPSK1

240km 1.6 b/s/Hz/pol

• For spectral efficiency– RZ DPSK for sensitivity benefit

Pre filtering to approach SSB

Im

– Pre-filtering to approach SSB– DQPSK for enhanced efficiency– Optical equaliser– FEC

Re

C

DFB MZM 50/100 GHzInterleaver

ol)

PSKSSB-PSK

MZM �/2

ncy

(b/s

/Hz/

p

ASK

ectra

l Effi

cien

www.tyndall.ie1: A.H.Gnauck, OFC 2007, PDP19 (2007)

Spe

SNR (dB)

52 Direct Detection Modulation formats

• When amplifier spacing taken into accountAll th lt 2 f th li it

Direct Detection– All three results ~ x2 from the limit– Independent of

• Bi-polar / Uni-polar modulation• Single or dual quadrature ol

) 80km100km

Amplifier Spacing

• Polarisation multiplexing• Key features

– FEC– Techniques approaching SSB fic

ienc

y (b

/s/H

z/po 100km

40kmLinear

N liTechniques approaching SSB • 80% there using RZ pre-filtering• 100% there using Coherent WDM

• Promising approachFEC

Spe

ctra

l Eff Non-linear

– FEC– Polarisation multiplexed (x2)– Dual Quadrature (x2)– Coherent WDM (x2)

Transmission distance (Mm)

www.tyndall.ie

( )• Little scope beyond ~2 b/s/Hz/pol

53 Coherent Detection

8

Hz)

Linear

6

Lim

it (b

/s/H

Coherent DetectionNon-Linear

4

Effi

cien

cy L

Significant room for performance enhancement

Linear

2

Spe

ctra

l E

Direct DetectionNon-Linear

1.00.5 2.00.2 5.00.1 10.0


S

www.tyndall.ie


2000km, 80km spacing, 4.5dB noise figure, 50 GHz channels at 50 Gbaud

54Coherent Detection 1: PSK

1,200km 3 b/s/Hz

Im• Long Distance High Data Rate– Constant Intensity Format

Re– Increased constellation size– Narrow Line-width Laser– FECFEC

ECL MZMMZM �/2

PMAxes to add and legend (all slides)

pol)

ency

(b/s

/Hz/

ppe

ctra

l Effi

cie

www.tyndall.ieM.Seimetz et.al.,, ECOC 2007 Tu1E1

Sp

SNR (dB)

55Coherent Detection 2: OFDM

4,160km 5.6 b/s/Hz

Orthogonal Frequency Domain Multiplexing• Data spread amongst many orthogonal carriers• Orthogonal carriers give SSB performance (less

overhead)• Modulate each subcarrier with QAM constellation• Increase constellation size electronically• FEC

Double side band

pol)

ncy

(b/s

/Hz/

pec

tral E

ffici

en

www.tyndall.ie

Spe

SNR (dB)

H. Takhashi et.al., , ECOC 2008 PDP Th3E4

56Coherent Detection 3: QAM

150km 10b/s/Hz

• Ultra high Spectral Density– Maximum QAM Constellation

• With Niquist filtersUl li id h l– Ultra narrow line-width laser

– FEC

ol)

cy (b

/s/H

z/po

ectra

l Effi

cien

www.tyndall.ie

Spe

SNR (dB)M. Yoshida, Optics Express, 16 2 pp829 (2008)

57 Coherent Detection Modulation Formats

• Performance2 f– > x2 performance gap

– Relative performance degrades with reach

• Key Features

/Hz/

pol) Linear

– All polarisation multiplexed• Often comes for “free”

– Multi-level modulation essential– PSK performs well ra

l Effi

cien

cy (

b/s Non-linear

S pe o s well• Is performance limited by

nonlinear effects?– Orthogonal modulation and/or

spectrum control usedS

pect

rp

• Optimum Solution– Still to be established– Perhaps

256 QAM over OFDM over CoWDM

Transmission distance (Mm)

www.tyndall.ie

• 256 QAM over OFDM over CoWDM

58 Latest Capacity Distance Results

• Coherent detection already outstripping direct detection• Record result is coherently detected OFDM

1,000,000

)1,000,000

)

• Post Deadline Papers?– > 0.1 Pbit/s.Mm

10,000

100,000uc

t (Tb

it/s.

km)

10,000

100,000uc

t (Tb

it/s.

km)

10

100

1,000

Dis

tanc

e Pr

od

OTDM-DDWDM DD10

100

1,000

Dis

tanc

e Pr

od

OTDM-DDWDM-DDS lit DD

0

1

10

Bit

Rat

e D WDM-DD

Soliton-DDTDM-DD

0

1

10

Bit

Rat

e D Soliton-DD

TDM-DDOFDM/CoWDMCoherent

www.tyndall.ie

83 85 87 89 91 93 95 97 99 01 03 05 07 09 11 13 15 17 19 21 23Date

83 85 87 89 91 93 95 97 99 01 03 05 07 09 11 13 15 17 19 21 23Date

59 Bibliography – Modulation Formats

1. R.C.Steele, Electron.Lett., 19 pp69- (1983)2. S.Norimatsu et.al., PTL, 4 pp765- (1992)3. S.Walklin et.al., JLT 17 11, pp.2235– (1999)4. B.Wedding et.al., . ECOC 1998, pp523– (1998)5 M I H t l PTL 13 8 881 (2001)

24. G.Charlet et.al., OFC 2008, paper PDP3 (2008)25. A.H.Gnauck et.al., JLT 26 1 (2008)26. N.Kikuchi et.al., JLT 26 1 (2008)27. Y.Mori et.al., ECOC 2008, Paper Tu.1.E.4 5. M.I.Hayee et.al., PTL, 13 8, pp881– (2001)

6. T.Nakamura et.al., OECC 2002, pp554– (2002)7. I.Morita, N.Edagawa, ECOC 2003, PDP page

60 (2003)8. X.Liu et.al., ECOC 2003, pp.1010– (2003)9 T Nakamura et al 22 pp733 (2004)

, , p(2008)

28. M.Nakamura et.al., ECOC 2008, Paper Tu.1.E5 (2008)

29. M.Nakazawa, ECOC 2008, Paper Tu.1.E.1 (2008) 9. T.Nakamura et.al., 22 pp733– (2004)

10. S.Tsukamoto et.al., OFC2005 Paper PDP29 (2005)

11. K.Sekine et.al., Electron. Lett., 41, pp430 (2005)

12. S.K.Ibrahim et.al., IEEE J. OF Select. Topics in

( )30. T.Sakamoto et.al., ECOC 2008, Paper

Tu.1.E.3 (2008)31. T.Tokle, OFC 2008, paper OMI1 (2008)32. P.J.Winzer et.al., ECOC2008, paper Th.3.E.5

(2008), pQuantum Electron., 12 4 (2006)

13. T.Pfau et.al., PTL, 18 pp1907- (2006)14. R.A.Griffin et.al., OFC2002, paper WX6 (2006)15. K.Kikuchi, OFC2006, paper OTuI4 (2006)16. M.Nakazawa et.al., Electron.Lett., 42 pp710

(2008)33. M.Yoshida et.al., ECOC 2008, Paper Mo.4.D5

(2008)34. M.Yoshida et.al., Optics Express, 16 2 pp829-

(2008)35 J Yu et al ECOC 2008 paper Th 3 E3 (2008)pp

(2006)17. Y.Han et.al., Electron.Lett., 42 2 (2006)18. J.Hongo et.al., PTL, 19 pp638- (2007)19. Ip et.al., JLT, 25, pp2675- (2007)20. J.Hongo et.al., OFC2007, Paper OMP3 (2007)

35. J.Yu et.al., ECOC 2008, paper Th.3.E3 (2008)36. X.Zhou et.al., OFC 2008, paper PDP1 (2008)

www.tyndall.ie

21. A.H.Gnauck, OFC 2007, PDP19 (2007)22. M.Serbay et.al., OFC 2007 paper OThL2

(2007)23. M.Seimetz et.al.,, ECOC 2007 Tu1E1

60 Bibliography – OFDM & CoWDM

1. V.Jungnickel et.al., Proc Vehicular Technology, p861-, (2005)2. A.D.Ellis et.al., PTL, 17, pp 504- (2005)3. W.Shieh et.al., OFC 2007, paper OMP2 (2007)4. N.Cvijetic et.al., OFC 2007, paper OTuA5 (2007)5 A Lowery et al OFC 2007 paper OTuA4 (2007)5. A.Lowery et.al., OFC 2007, paper OTuA4 (2007)6. T.Healy et.al., ECOC’07, paper Mo1.3.5 (2007)7. F.C.Garcia Gunning et.al., CLEO Europe 2007, paper CI8-5 (2007)8. W.Shieh et.al., Optics Express, 15 pp9936 (2007), p p , pp ( )9. E.Ip et.al., Optics Express, 16 2 pp753- (2008)10. S.L.Jansen et.al., OFC 2008, paper PDP2 (2008)11. H.Takhashi et.al., ECOC 2008 PDP Th3E4 (2008)12. Q.Yang et.al., OFC 2008, paper PDP7 (2008)13. E.Yamada et.al., OFC 2008, paper PDP8 (2008)

www.tyndall.ie

61 Introduction



www.tyndall.ie

62How to increase the capacity further:

Optimisation of current technology

ain

(dB

)

/s/H

z/po

l)

~3dB / bit Com

p

16QAM

PSK, QAM

net c

odin

g g

Effic

ienc

y (b

/

128 QAM

8PSK

lexity of Implem

e

PSK

QPSK8PSK

16QAM

bit / b l/ l

Req

uire

d

Spe

ctra

l E

SNR (dB)

entation

PSK

PSK, QAM

bits/symbol/polSNR (dB)

• Multi-level modulation formats with coherent detection• Required FEC strength increases significantly with signal bits

– Maximise number of orthogonal channels first • Polarisation• Quadrature

S b i

www.tyndall.ie

• Subcarrier

– Expect significant (�100%) overhead for 128 QAM and above

63The Ultimate Quest

Maximum capacity for fixed installed plantz/

pol)

ding

Throughput of multilevel transmission at fixed SNRAssuming required overhead = 70 x achievable raw BER

@ SNR suitable for ASK transmission at 10-12

PSK QAM

cien

cy (b

/s/H

z

ymbo

l afte

r cod

PSK, QAM64QAM

16PSK

Spec

tral E

ffic

ASK, QAM

Net

bits

per

sy

• Fixed Plant – Terminal Changes Only

S

SNR (dB) Bits per symbol transmitted

– Fixed SNR– Modulation format changes– Coding (FEC) changes

www.tyndall.ie


Amplifier optimisation

• Amplifier bandwidth– Capacity scales ~linearly with bandwidth ��

�

��

��

BNPBC 1log. 2

• Amplifier Noise figure– Modest capacity increase ~ Log2 noise reduction

) pol)

��

�� BNo

cy (b

/s/H

z/po

l

ency

(b/s

/Hz/

p

ectr

al E

ffici

enc

Amplifier Bandwidth:96 THz (2 cycles per bit)4.8 THz (40 cycles per bit / C-band)1 THz Sp

ectr

al E

ffici

e

Amplifier Noise Figure:4.5dB Typical3dB Ideal0dB Phase sensitive*

Spe

Power spectral density (W/THz)

S


www.tyndall.ie

2000km, 80km spacing, (4.5dB noise figure), 50 GHz channels at 50 Gbaud, (5THz amplifier bandwidth), 0.2dB/km loss

* Phase sensitive amplifier: 0dB noise figure, but quantum noise for attenuation ~ ½ of 3dB noise figure case1

1: L.Thylen et.al., Channel capacity of optical fibres, Private communication (2002)


Multi-tone transmission

• Non-linear index effects may be compensated at the terminals.

B k d ti– Backwards propagation– For OFDM1

– Multiple coherent channels2

• Increase bandwidth of channel• Increase bandwidth of channel

pol)

10TH

ency

(b/s

/Hz/

p5THz

10THz

Spec

tral

Effi

cie

1GHz

100GHz1THz

3THz

www.tyndall.ie1: A.J.Lowery, Optics Express 15 20 pp12965 (2007)2: E.Yamazaki, WS-1, ECOC 2008

S

Power spectral density (W/THz)2000km, 80km spacing, 4.5dB noise figure, 10THz amplifier

66How to increase the capacity further:Multi-wavelength optical regeneration

• Multi-wavelength all optical regeneration � Breaks up noise accumulation– Dispersion managed Mamyshev regenerator1p g y g– Quasi continuously filtered regenerator2

– Bi-directional / dual polarisation3

– Parametric effects4

s/H

z/po

l)

Number of

Effic

ienc

y (b

/s

Regenerators3216842

Spec

tral

T i i R h (k )

21

www.tyndall.ie

2000km, 80km spacing, 4.5dB noise figure, 5THz amplifier

Transmission Reach (km)1: M. Vasilyev et.a., OFC 2005, OME62.2: B.Cuenot et.al., Optics Express 15 18 pp11492 (2007)3: L.Provost et.al., ECOC 2007, Tu4.5.14: B.Cuenot, OAA 2006, OWA4


Fibre Design

SMF-28TM LongLineTM

Fiber1Hollow Core PCF3

(prediction)

Loss (dB/km) 0.2 0.185 .13

Non-linear coefficient (W-1km-1)

~ 1 ~ .75 ~0.01(99% air propagation)

Waveband (nm) 1550 1550 1900Waveband (nm) 1550 1550 1900

m) 10Gb/s

12

10/Hz/

pol)

Dis

tanc

e (M

m 40Gb/s

80 to 160 Gb/s

10

8

6

4

ISDxD contours

Effic

ienc

y (b

/s

Information Spectral Density (b/s/Hz)0 1 2 3 4

2

Spec

tral

E


www.tyndall.ie1: M. Bigot-Astruc, Mo.4.B1, ECOC’082 :G.Charlet, Th3Ee, ECOC’083: P.J.Roberts et.al., Optics Express 13 1 pp236 (2005)


68 The Ultimate Capacity?

• Transmission link fabricated from hollow core PCF• Optical amplifiers replaced by ideal WDM regenerators• Ultimate limit ~ 17 b/s/Hz/pol

– ~170 Tbit/s in a 40nm bandwidthwith a higher bandwidth 1 Pbit/s Mm– with a higher bandwidth ~ 1 Pbit/s.Mm

s/H

z/po

l)

Ideal regen, ideal PCF

Effic

ienc

y (b

/s

Optical amplifiers, SMF

Spec

tral

E


Optical amplifiers, SMF

www.tyndall.ie


69Conclusions:

Reaching the limits of communication capacity

• What do we need to do (system design)?– Dispersion management– FEC

O th l i

• What do we need to make (components)?– Integrated arrays– High speed DSP, ASICs

N li idth l– Orthogonal carriers– Coherent detection– QAM– Non-linear compensation

– Narrow linewidth lasers– Linear modulators and drivers

• And to extend the limit…– Amplifier for waveband extension 10,000

100,000

1,000,000

(Tbi

t/s.k

m)

64 QAM CO-OFDM ?

Amplifier for waveband extension– Improved transmission medium– Undiscovered modulation techniques– Multi-wavelength regeneration 10

100

1,000

,

ate

Dis

tanc

e Pr

oduc

t (

OTDM-DDWDM-DDSoliton-DDTDM-DD

www.tyndall.ie

0

1

83 85 87 89 91 93 95 97 99 01 03 05 07 09 11 13 15 17 19 21 23Date

Bit

Ra TDM DD

OFDM/CoWDMCoherent

70

• Thank You

Ph t i S t G• Photonic Systems Group, Tyndall National Institute & Department of Physics, University College Cork, Ireland.

physics.ucc.ie/photonics/photonicsJobs.htm

www.tyndall.ie

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