Tutorial Optical Transmission Systems Peter J Winzer

7/25/2019 Tutorial Optical Transmission Systems Peter J Winzer

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COPYRIGHT 2015 ALCATEL-LUCENT. ALL RIGHTS RESERVED.

Optic Communication Systems

For Non-Optical Communications EngineersPeter J. WinzerBell Labs, Alcatel-Lucent, USA


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ACKNOWLEDGMENT

Bell Labs

S.ChandrasekharA.R.ChraplyvyR.-J.EssiambreN.K.FontaineG.J.FoschiniH.KogelnikG.KramerA.LevenX.Liu

S.RandelG.RaybonR.RyfR.W.Tkach

AND MANY OTHERS

Univ. Tel Aviv

Univ. LAquilaC.AntonelliR.DarA.MecozziM.Shtaif

Politecnico di Torino

P.Poggiolini


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OVERVIEW

The role of optics in data networks

Linear and nonlinear impairments in optical networks

Optical modulation and detction techniques

Optical multiplexing techniques

Spatial multiplexing in optical communications

(MIMO and MIMO-SDM security)


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1

The role of opticsin data networks


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MASSIVE TRAFFIC GROWTHMULTI-MEDIA & MACHINE-TO-MACHINE APPLICATIONS

HiDef Video Communication Panasonics LifeWall

1995 2000 2005 2010

2 dB / year(58%/year)

10 Gb/s

100 Gb/s

1 Tb/s

10 Tb/s

US data network traffic

100 Tb/s

60% 10 log10(1.6) dB 2 dB

[R.W.Tkach, Bell Labs Tech. J., 2010]

3D manipulation

zspace.com


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Amdahls rule of thumb

1 Floating point operation (Flop) triggers ~1 Byte of transport

100 TFlops

10 TFlops

1 TFlops

100 GFlops

10 GFlops

1 GFlops

1995 2000 2005 2010

2.7 dB / year(86%/year)

2 dB / year(58%/year)

10 Gb/s

100 Gb/s

1 Tb/s

10 Tb/s

US data network traffic

Top 500 Supercomputers 100 Tb/s

60% 10 log10(1.6) dB 2 dB

http://www.circuitboards1.com

MASSIVE TRAFFIC GROWTHMULTI-MEDIA & MACHINE-TO-MACHINE APPLICATIONS

[P.J.Winzer, Proc. ECOC, 2010]

Cloud services turn the network into a giant multi-processor interface


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TRAFFIC GROWTH VARIATIONS: 20% TO 90%DEPENDING ON APPLICATION AND GEOGRAPHY

IEEE 802.3 Industry Connections Ethernet Bandwidth Assessment, http://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdfMetro Network Traffic Growth, Bell Labs Strategic White Paper, http://resources.alcatel-lucent.com/asset/171568M. Nowell, Cisco Visual Networking Index; 20102015, http://www.ieee802.org/3/ad_hoc/bwa/public/sep11/nowell_01_0911.pdf Cisco Visual Networking Index: Forecast and Methodology, 20132018, http://www.cisco.com

[P. J. Winzer, Bell Labs Tech. J., 2014]
http://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdfhttp://resources.alcatel-lucent.com/asset/171568http://www.ieee802.org/3/ad_hoc/bwa/public/sep11/nowell_01_0911.pdfhttp://www.cisco.com/c/en/us/solutions/collateral/service-provider/ip-ngn-ip-next-generation-network/white_paper_c11-481360.pdfhttp://www.cisco.com/c/en/us/solutions/collateral/service-provider/ip-ngn-ip-next-generation-network/white_paper_c11-481360.pdfhttp://www.cisco.com/c/en/us/solutions/collateral/service-provider/ip-ngn-ip-next-generation-network/white_paper_c11-481360.pdfhttp://www.cisco.com/c/en/us/solutions/collateral/service-provider/ip-ngn-ip-next-generation-network/white_paper_c11-481360.pdfhttp://www.ieee802.org/3/ad_hoc/bwa/public/sep11/nowell_01_0911.pdfhttp://www.ieee802.org/3/ad_hoc/bwa/public/sep11/nowell_01_0911.pdfhttp://www.ieee802.org/3/ad_hoc/bwa/public/sep11/nowell_01_0911.pdfhttp://resources.alcatel-lucent.com/asset/171568http://resources.alcatel-lucent.com/asset/171568http://resources.alcatel-lucent.com/asset/171568http://resources.alcatel-lucent.com/asset/171568http://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdfhttp://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdfhttp://www.ieee802.org/3/ad_hoc/bwa/BWA_Report.pdf


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DATA NETWORKING INFRASTRUCTUREOPTICAL COMMUNICATIONS EVERYWHERE

Core

Access

LAN

Satellites

Data center

SwitchingTransport


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WHY OPTICAL COMMUNICATIONS?

1 0 1 1 0 1 0 1 1 0

TX RXMetric: Maximum transmission distance that can be

bridged before digital regeneration becomes necessary.

High data rates

and

long distances

Fiber to the home

(FTTH)

Alcatel-Lucents1830 PSS

Reg

eneration-freetra

nsmissiondistanc

e

Aggregate link capacity

[P. J. Winzer et al., Proc. IEEE 94, 952-985 (2006)]


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WHY OPTICAL COMMUNICATIONS?REASON #1: LARGE NARROW BANDWIDTHS

1 kHz 1 MHz 1 GHz 1 THz 1 PHz

Frequency / wavelength of the electromagnetic field

VLF LF MF HF

1 km 1 m 1 mm 1 mm

VHF UHF SHF EHF

V

isible

Light

h

=

kT

~ 5 GHz

C L

At 200 THz (1.5mm) carrier frequency

Low-loss fiber

Efficient sources & detectors

Low-noise amplifiers (EDFAs)

5 50 THz of channel bandwidth

is still narrowbandat 200 THz(~a few % relative bandwidth)Thats where most digital radio happens


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WHY OPTICAL COMMUNICATIONS?REASON #2: VERY LOW PROPAGATION LOSSES

Loss[dB/km]

Accurate pointing needed

(~ mrad @ kHz vibrations)

K. H. Kudielka et al.,

Proc. IEEE Phased Array

Symposium, Boston, 419 (1996)

Attenuation of glass

Today: < 0.2 dB / km

(RF coax: ~ 100x to 1000x more loss)

Divergence angle ~ l/D

PRX~ PTXDTXDRX/ l222

E.g., 200 THz instead of 20 GHz

108x higher antenna gain (80dB)

Divergence in free space

D


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TELECOMMUNICATIONS BEFORE FIBER-OPTICSAT&TS LONG-HAUL BUSINESS

Technology Designation YearVoice circuits

per channel

2-way

channels

Repeater

distance

Total 2-way

voice circuits

Coax

L-1 1941 600 4 8 miles 2400

L-3 1950 1,860 6 4 miles 11,160

L-4 1967 3,600 10 2 miles 36,000

L-5E 1975 13,200 11 1 mile 145,200

Microwave

Relay

TD-2 (4 GHz) 1969 1,200 12 26 miles 14,400

TH-1 (6 GHz) 1961 1,860 8 26 miles 14,880

AR6A (6 GHz) 1981 4,000 8 26 miles 32,000

mm-

WaveguideWT4 (trial) 1975 4,032 57 25 miles 230,000


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Courtesy: H. Kogelnik

FIBER VS. COPPER - A CLEAR BUSINESS CASE

For 6x less in cable diameter,and 23x less in weight,and 25x longer repeater spacing,you got 156x more capacity!

Ca. 1977


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OPTICAL NETWORKS: WORKHORSE OF THE INTERNET

Lineinterface(e.g., 100 Gbit/s)

Router

Optical network

Reconfigurable opticaladd/drop multiplexer

(ROADM)

Clientinterface(e.g., 4 x 25 Gbit/s)

WDMsystem(e.g., 80 x 100 Gbit/s)

Increaseper-wavelength interface rateIncrease aggregateper-fiber capacityIncrease network flexibility

Spectral efficiency (SE) in [b/s/Hz]:

SE = per-channel bit rate / WDM spacing

Tx Rx

~ 5 THz bandwidth ~ 100 km of fiber


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HIGH-SPEED OPTICAL INTERFACESWHY A TERABIT IS CHALLENGING BUT NEEDED

1986 1990 1994 1998 2002 2006

10

100

1

10

100

SerialInterfaceRat

esandWDMCapacit

ies

Gb/s

Tb/s

2010 2014 2018

1

2022200G optical line interfacesare now available

Router interfacescaling has merged with transport rates

Router port aggregationno longer possible[P. J. Winzer, IEEE Comm. Mag. 26-30 (2010)]

Network processors available at 400G

1-port 100GigE

?

!


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HIGH-CAPACITY WDM SYSTEMSWHEN WILL WE NEED FASTER INTERFACES ?

20% 40% 60% 80%

400 Gb/s 2018 2014 2013 2012

1 Tb/s 2023 2017 2015 2014

10 Tb/s 2035 2024 2020 2018

(Simple extrapolation of higher interface needs)

Fact: Leading-edge providers started installing 100G interfaces in 2010.Question: When will such providers want higher-rate interfaces?

Assumedtrafficgrowth rate

Assumedinterface raterequirement

Extrapolated availability requirementfor higher-speed interfaces


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HIGH-CAPACITY WDM SYSTEMSCOMMERCIAL CAPACITY SATURATION AT ~ 50 TB/S

1986 1990 1994 1998 2002 2006

10

100

1

10

100

SerialInterfaceRat

esandWDMCapacit

ies

Gb/s

Tb/s

2010 2014 2018

1

2022

WDM capacity scaling has slowed from ~100%/year to ~20%/year in 2000

WDM systems available up to ~10 to 20 Tb/s

[P. J. Winzer, IEEE Comm. Mag. 26-30 (2010)]

?


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HIGH-CAPACITY WDM SYSTEMSWHEN WILL WE NEED FASTER INTERFACES ?

(Simple extrapolation of higher WDM capacity needs)

Fact: Leading-edge providers started installing 10T WDM systems in 2010.Question: When will such providers want higher-capacity systems?

AssumedTrafficgrowth rate

AssumedWDM capacityrequirement

Extrapolated availability requirementfor higher-capacity systems

20% 40% 60% 80%

50 Tb/s 2019 2015 2013 2012

200 Tb/s 2026 2019 2016 2015

1 Pb/s 2035 2024 2020 2018


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1986 1990 1994 1998 2002 2006

10

100

1

10

100

SerialInterfaceRat

esandWDMCapacit

ies

Gb/s

Tb/s

2010 2014 2018

1

2022




?

?


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2Impairments in opticalnetworks


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NOISE FROM OPTICAL AMPLIFIERSAMPLIFIED SPONTANEOUS EMISSION (ASE)

Fiber and optical component loss

Noise from in-line amplification (EDFA, Raman); proportional to gain G Lower bound on noise dictated by quantum mechanics

Optical signal-to-noise ratio (OSNR):

RXTX

Amplified spontaneous emission (ASE)

Optical signal power

Optical noise power

[R.-J. Essiambre et al., J. Lightwave Technol. (2010)]


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RXTX



Optical noise power

G amplifier gain = span lossNspan number of spans

Span length 100km 50km

Span loss (=G) 20dB 10dB

Spans Nspan 2 Nspan

Total noise 100 Nspan 20 Nspan


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RXTX



Optical noise power

[R.-J. Essiambre et al., J. Lightwave Technol. (2010)]


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FIBER NONLINEARITIESTHE ULTIMATE LIMIT OF FIBER TRANSMISSION Fiber and optical component loss


Increase signal power for better (O)SNR:

Fiber nonlinearities

(within a signal, between WDM signals, between signal and noise)

Signal power

(Optical) noise power

Core diam. ~8 mmMegawatt / cm2optical intensities

n = n0+n1Popt+ (Kerr effect)

Leads to nonlinear distortionsover hundreds of kilometers

A A ejznzA ejzn z ejzn P z0 1 opt


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FIBER NONLINEARITIESTHE ULTIMATE LIMIT OF FIBER TRANSMISSION Fiber and optical component loss


Increase signal power for better (O)SNR:

Fiber nonlinearities

(within a signal, between WDM signals, between signal and noise)

RXTX


Signal power

(Optical) noise power


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CHROMATIC DISPERSION AND PMD


Noise from in-line amplification (EDFA, Raman); proportional to gain G Signal-distortions

Fiber nonlinearity

Chromatic dispersion, polarization-mode dispersion


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CONCATENATED FILTERING IN OPTICAL NETWORKS



Fiber non-linearity


Optical filter concatenation

l1

lN

DEMUX MUX

Drop AddWDM multiplexer

WDM demultiplexer

l1

lN


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CROSSTALK IN OPTICAL NETWORKS



Fiber non-linearity


Optical filter concatenation

Crosstalk (WDM, inband)


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OPTICAL FIBER TRANSMISSION

Optical field propagating in the fibers transverse mode

(Nonlinear Schrdinger Equation)+ N

ROADM Reconfigurable optical add/drop multiplexer

FiberNonlinearity

FilteringEffects

Chromatic Dispersion

Optical Filtering (ROADMs)

Spontaneous emission from

in-line optical amplifiers

Noise


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Simulation steps

Step size DzDz

0 2 3 4 5 6 7 81 Distance

SPLIT-STEP FOURIER TRANSFORM METHOD

NUMERICAL SOLUTION OF FIBER PROPAGATIONConsider short pieces of fiber (dispersion only, nonlinearity only)

Alternate between simple solution in t and f

Nonlinearity (but no dispersion)

Dispersion (but no nonlinearity)

Courtesy: Pierluigi Poggiolini


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DISPERSION-MANAGED SYSTEMS

MANAGING NONLINEARITY WAS REALLY HARD

0.01

0.1

1

10

Spectralefficiency

perpolarization[b/s/

Hz]

1990 1994 1998 2002 2006

Year

2010

Laser & filter stability

x-pol

y-pol

x-pol

y-pol

Modulation

PDM

~1 dB/year

Detection


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y g gg

FINDING THE FACTOR


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FINDING THE FACTOR

Optics Express, 16335 (2014)

J. Lightwave Technology (2015)


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3Modulation inoptical communications

HIGH CAPACITY WDM SYSTEMS


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1986 1990 1994 1998 2002 2006

10

100

1

10

100

SerialInterfaceRa

tesandWDMCapaci

ties

Gb/s

Tb/s

2010 2014 2018

1

2022




?

?

THE COMMUNICATION ENGINEERS TOOLKIT


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THE COMMUNICATION ENGINEERS TOOLKIT

5 DIMENSIONS OF AN ELECTRO-MAGNETIC WAVE

Polarization

Time Quadrature

Modulation of the field in

Frequency

Space

Same 5 dimensions across communications technologies(Wireless, DSL, Optics, )

USING THE FIVE PHYSICAL DIMENSIONS


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USING THE FIVE PHYSICAL DIMENSIONSAN OPTICAL COMMUNICATIONS POINT OF VIEW

Polarization

Time Quadrature

Physical dimensions

FrequencySpace

t

f

O E S C L

1300

0

1400 1500 1600

0.3

0.6

0.9

1.2

Wavelength [nm]

Loss[dB]

13601260 1460 1530

1565

1625


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3.1Intensity modulation

MODULATING THE INTENSITY DIMENSION


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MODULATING THE INTENSITY DIMENSION

Easiest property to modulate

Use absorptionor interferenceprocesses

Intensity

p

in

datap

[P.J. Winzer et al., Proc. IEEE, p.952 (2006).]

DETECTING THE INTENSITY DIMENSION


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DETECTING THE INTENSITY DIMENSION

Practical detection schemes are important for high-speed optical systems.

Practical modulation techniques are important for high-speed optical systems.

Photodetection

Electrical signalOptical intensity

1)Demodulation refers to the process of moving an (optical) passband signal to (electrical) baseband, while

detection refers to the extraction of digital information out of the baseband signal.

Easiest property to modulate

Use absorptionor interference

Easiest property to demodulate

'Direct detection' (better1): 'demodulation) = optical intensity detection,photodetection

Intensity

THE #1 TRANSPONDER DESIGN STRATEGY


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THE #1 TRANSPONDER DESIGN STRATEGYMODULATE AS FAST AS ECONOMICALLY FEASIBLE

Space

PolarizationFrequency

Time Quadrature

Physical dimensions

10 Gb/s25 Gb/s

53.5 Gb/s 107 Gb/s

Research:

107-Gb/s electrical signal

[Winzer et al., ECOC05]100G Photo-receiver

[Sinsky et al., OFC07]

100G CDR Demux

[Derksen et al., OFC06]


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3.2Phase modulation

OPTO ELECTRONIC CONVERTERS DETECT INTENSITIES


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OPTO-ELECTRONIC CONVERTERS DETECT INTENSITIES

Photodetection

Electrical signalOptical intensity

Intensity PhasePhase-to-amplitude conversion at detection

Also known as interference in optics

Local oscillator laser (coherent receiver)

Signal self-reference (differential mod.)

Direct detection with delay demodulation

Differential phase modulation

Information in phase difference

Coherent receiver

BINARY DIFFERENTIAL PHASE MODULATION


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constructive

destructive

balanced

Detector amplitude imbalanceOSNR

penalty

[dB]

BINARY DIFFERENTIAL PHASE MODULATIONNEED BALANCED DETECTION TO GAIN 3 dB

[Gnauck et al., JLT, 115 (2005)]

Im{E}

Re{E}

OOK DPSK

Im{E}

Re{E}


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3.3Multi-level modulation

NEED HIGHER BIT RATES ?


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NEED HIGHER BIT RATES ?ONE OPTION: MULTI-LEVEL

Space


Time Quadrature

Physical dimensions

10 Gb/s

25 Gb/s

53.5 Gb/s 107 Gb/s

50 Gb/s

Multilevel (PAM)

PAM: Pulse amplitude modulation

10

11

01

00

NEED HIGHER BIT RATES ?


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NEED HIGHER BIT RATES ?ONE OPTION: MULTI-LEVEL

Space


Time Quadrature

Physical dimensions

10 Gb/s

25 Gb/s 50 Gb/s

Multilevel (PAM)

PAM: Pulse amplitude modulation

[Gnauck et al., OFC 2011]

56 Gb/s (28 GBd) 112 Gb/s (56 GBd) 160 Gb/s (80 GBd)

[Winzer et al., ECOC 2011] [Raybon et al., PTL 2012] [Raybon et al., ECOC 2013]

214 Gb/s (107 GBd)

QUADRATURE PHASE SHIFT KEYING (QPSK)


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QUADRATURE PHASE SHIFT KEYING (QPSK)MULTI-LEVEL IN BOTH QUADRATURES

Im{E}

Re{E}

16-QAM TRANSMITTER


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16-QAM TRANSMITTERUSING A DAC AND AN I/Q MODULATOR

6 dB6 dB

2-bit arbitrary waveform generator

Multiple-bitdelay

Im{E}

Re{E}4

4

IntegratedI/Q Modulator

p/2

PRBS: Pseudo-random bit sequence

I/Q: In-phase/quadrature (or: Re{E} / Im{E})

215

-1PRBS at14.0 Gb/s

D1

D1

D2

D2

6 dB

6 dB

(D2outputshalf-patterndelayed wrtD1 outputs)

11-GHz LPF

11-GHz LPF

Laser

[Winzer et al., ECOC08]

HIGHER-LEVEL FORMATS


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p/2

N-level Electronic Signal I

N-level Electronic Signal Q

Laser N2QAM Signal

Format N Bits/symbol

QPSK 2 216-QAM 4 4

64-QAM 8 6

256-QAM 16 8

N2-QAM N 2 log2(N)

8-level drive for 64-QAM

HIGHER-LEVEL FORMATSUSING A DAC AND AN I/Q MODULATOR

[A. Sano et al., ECOC2010, PD2.4]

[J. Godin et al., BLTJ, 2013] 21.4 GBaud

10 GBaud

[J. Godin et al., BLTJ, 2013]

50 GBaud

CONSTELLATION SIZE VERSUS SYMBOL RATE


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CONSTELLATION SIZE VERSUS SYMBOL RATE

1 2 3 4 5 6 7 8 9

100

200

300

Bits per symbol

Linera

te[Gb/s]

16-QAM

[Winzer, J. Lightwave Technol. 30, 3824 (2012)]

PDM 512-QAM

3 GBaud (27 Gb/s)[Okamoto et al., ECOC10]

PDM 256-QAM

4 GBaud (32 Gb/s)[Nakazawa et al., OFC10]

PDM 64-QAM

21 GBaud (128 Gb/s)[Gnauck et al., OFC11]

PDM 16-QAM

80 GBaud (320 Gb/s)[Raybon et al., PTL12]

PDM QPSK

107 GBaud (224 Gb/s)[Raybon et al., PTL12]

ADC & DAC resolution Bandwidth

[R. H. Walden, JSAC (1999), and Proc. CSIC (2008)][A. Khilo et al., Opt. Ex. (2012)]

SCALING THROUGH MORE LEVELS OR SYMBOL RATE ?


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SCALING THROUGH MORE LEVELS OR SYMBOL RATE ?

PDM 512-QAM

3 GBaud (54 Gb/s)[Okamoto et al., ECOC10]

PDM 256-QAM

4 GBaud (64 Gb/s)[Nakazawa et al., OFC10]

PDM 64-QAM

21 GBaud (256 Gb/s)[Gnauck et al., OFC11]

PDM 16-QAM

80 GBaud (640 Gb/s)[Raybon et al., IPC12]

Logarithmic scaling Linear scaling

PDM QPSK

107 GBaud (448 Gb/s)[Raybon et al., ECOC12]

[T. Pfau et al., J. Lightwave Technol. 27(8), 989 (2009)]


PRACTICAL CONSIDERATIONS


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PRACTICAL CONSIDERATIONSIMPLEMENTATION PENALTY

98

7

6

54

3

2

1Bitspersymbol(perpolarization)

2.0

1.5

1.5

0.70.9

0.5

0.6

3.3

1.6

1.0

2.1

0.72.4

1.3

0.9

0.6

2 2

2.4

1.7

2.8

0.6

0.5

4.3

10 100

Symbol rate [Gbaud]

5 20 50


EVOLUTION OF HIGH-SPEED TRANSPONDERS


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EVOLUTION OF HIGH SPEED TRANSPONDERSTOWARDS 1 TB/S ON A SINGLE CARRIER

Space

Polarization

Frequency

Time Quadrature

Physical dimensions

1986 1990 1994 1998 2002 2006

10

100

2010 2014 2018

1

2022

107 Gbaud QPSK

1000

Serialinterfacerates[Gb/s]

107 Gbaud 16-QAM (856 Gb/s)

72 GBd PDM-64-QAM (864 Gb/s)

[Randel et al, 2014]

[Raybon et al, 2013]

SPECTRAL EFFICIENCY AND ITS PRICE IN SNR


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SPECTRAL EFFICIENCY AND ITS PRICE IN SNR

20 years ago:Device physics set engineeringlimitson spectral efficiency

Today:Information theory sets fundamentallimitson spectral efficiency

Simple on-off modulation,direct detection

Higher-order modulation,coherent detection

0.01

0.1

1

10

Spectralefficiency

perpolarizatio

n[b/s/Hz]

1990 1994 1998 2002 2006Year

2010

Laser & filter stability

x-pol

y-pol

x-pol

y-pol

Modulation

PDM

~1 dB/year

Detection

0 5 10 15 20 25

1

10

Required SNR per bit [dB]

Spectralefficiency

perpolarization[b/s/Hz]

3.7 dB 8.8 dB

2x

2x16

64

4

256SE = log

2(1 + SNR)

LOW SPECTRAL EFFICIENCY MODULATION


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LOW SPECTRAL EFFICIENCY MODULATION(SPACEBORNE APPLICATIONS)

0 5 10 15 20 25

0.1

1

10

SNR (photons)per bit [dB]

Sp

ectralefficiency[b/s/Hz]

Sensitivity-constrained

Capacity-constrained

Intensity

Pulse Position Modulation (PPM)

1 0 0 1 1 1

Position within PPM symbolTime

0 0

4

8

16

32

64

PPM

256

LOW SPECTRAL EFFICIENCY MODULATION


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LOW SPECTRAL EFFICIENCY MODULATION(SPACEBORNE APPLICATIONS)

0 5 10 15 20 25

0.1

1

10

SNR (photons)per bit [dB]

Sp

ectralefficiency[b/s/Hz]

Sensitivity-constrained

Capacity-constrained

4

8

16

32

64

PPM

256

Shot-noise limited

channels

Intensity

Pulse Position Modulation (PPM)

1 0 0 1 1 1

Position within PPM symbolTime

0 0

FROM CLASSICAL TO QUANTUM TECHNIQUES


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FROM CLASSICAL TO QUANTUM TECHNIQUES[J. Gordon, Quantum effects in communication systems, Proc. IRE 50, 1898 (1962)]

[A. S. Holevo, The capacity of a quantum channel with general signal states, Trans. Inf. Theory 44, 269 (1998)]

0.001 0.01 0.1 1 10 100Spectral efficiency [bits/s/Hz]

-20

-10

0

10

Sensitivity[dBbits/photon]

Linear Shannon

Photon counting

Gordon/Holevoquantum capacity

???

Classical Quantum

[C. Antonelli et al., J. Lightwave Technol. (2014)]

SOME MORE ADVANCED TRICKS


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[Karlsson & Agrell, ECOC10]

[Cai et al., ECOC10]

ISI

MAP

SOME MORE ADVANCED TRICKS4D, CODING, SHAPING, OVER-FILTERING

Whatever you do, Shannon will be the limit[C. E. Shannon, BLTJ (1948)]

0 5 10 15 20 25

1

10

Required SNR per bit [dB]

16-QAM

64-QAM

4-QAM

256-QAMConstellationshaping

Over-filtering

Coded modulation[Liu et al., OFC12]

Spectralefficiency[b/s/H

z]

ISI: Inter-symbol interference; MAP: Maximum a posteriori

4-DIMENSIONAL MODULATION


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4 DIMENSIONAL MODULATIONCLOSER SYMBOL PACKING THROUGH CORRELATIONS

Re{E}

4

Simple 2D example:16-QAM, viewed as 2 independent, orthogonally muxed 4-PAMs

Im{E}

Re{E}4

4

Im{E}

Re{E}4

Im{E}

+ =

Re{E}4

4

Im{E}

Here, the two dimensionsare no longer independent2D modulationSacrifice SE for performance [Karlsson & Agrell, ECOC10]

In 4D space:(Ix/Qx/Iy/Qy)

[H. Buelow et al., OFC 2013]

+ =

DIGITAL PULSE SHAPING


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DIGITAL PULSE SHAPINGPULSE BANDWIDTH AND SPECTRAL EFFICIENCY

10 dB

56 GHzSpectrum[dB]

Frequency

Spectral efficiency =Information bits

Signal spectral width

MODERN OPTICAL TRANSPONDERS


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MODERN OPTICAL TRANSPONDERSDIGITAL PULSE SHAPING

DAC

DAC

DAC

DAC

TransmitDSP

PDMI/Q-MOD

TX Laser

t

f

First 200G 16-QAM coherent interfaceAlcatel-Lucent 2013

Modern coherent transponders use pulse shaping for: Spectral efficiency Pre-compensation of various fiber impairments

(dispersion, nonlinearity, filtering)


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4Coherent detection and

digital signal processing

COHERENT DETECTION BASICS


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Local

Oscillator (LO)

Signal|ESig(t) + ELO|

2 = |ESig(t)|2+ |ELO|

22 Re{ESig(t) ELO e }

Beat term

90-deg shifted LO

Signal

Second signal quadrature Im{ESig(t) ELO e }

90-deg hybrid

Requires signal-LOpolarization alignment

j2pfIFt+jfSig(t)

j2pfIFt+jfSig(t)



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Local

Oscillator (LO)

Signal

90-deg shifted LO

Signal

Local

Oscillator (LO)

Signal

90-deg shifted LO

Signal

x-polarization y-polarization

The good news:Polarization multiplexing

comes for free

Polarization-diversity 90-degree hybrid



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THE ROLE OF THE INTERMEDIATE FREQUENCY

Heterodyne Homodyne Intradyne

Front-end bandwidth ~ 5* Symbol rate Symbol rate ~Symbol rate

Phase/frequency locking Frequency locking Analog optical PLLDigital electronic PLL

(free-running LO)

Spectral sketch

Constellation sketch

fIF0 f0 IF

LocalOscillator (LO)

f

Signal|ESig(t) + ELO|2: 2 Re{ESig(t) ELO e }

Beat term

Im{E}

Re{E}

Im{E}

Re{E}

Im{E}

Re{E}

j2pfIFt +jfSig(t)

MODERN COHERENT DETECTION


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DO AS MUCH AS YOU CAN DIGITALLY, IN CMOS

LO Local oscillator

DSP Digital signal processing

Coherent optical front-end

Im{E}

Re{E}

90 degHybrid

90 degHybrid

PBS

LO laserPBS

Signal

In-phase component

Quadrature component

In-phase component

Quadrature component

x-pol.

y-pol.

f0

PBS Polarization beam splitter

A/D Analog-to-digital conversion

x pol.

y pol.



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A/D

A/D

A/D

A/D

Ix

Qx

Iy

Qy

Digitization

HIGH-SPEED A/D CONVERSIONIN THE LAB

Agilent90000 Q-Series

160 GS/s @ 63GHz

LeCroyLabMaster 10Zi

160 GS/s @ 65 GHzLO Local oscillatorDSP Digital signal processing

90 degHybrid

90 degHybrid

PBS

LO laserPBS

Signal




x pol.

y pol.



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A/D

A/D

A/D

A/D

Ix

Qx

Iy

Qy

Digitization

HIGH-SPEED A/D CONVERSIONON CHIP

LO Local oscillator

DSP Digital signal processing

90 degHybrid

90 degHybrid

PBS

LO laserPBS

Signal




x pol.

y pol.

MAIN COHERENT DSP BUILDING BLOCKS


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Chromaticdispersion

Front-endcorrec

tions

A/D

A/D

A/D

A/D

+j

+j

Ix

Qx

Iy

Qy

Digital computation ofexp(-j a f2 )

Transmit pulse Dispersed received pulse Compensated pulse

Fiber DSP



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Chromaticdispersion

Front-endcorrec

tions

A/D

A/D

A/D

A/D

+j

+j

Ix

Qx

Iy

Qy

Digital computation ofexp(-j a f2 )

Transmit pulse

Fiber

with LO phase noise

Dispersed received pulse

Received phase

Ideal

Compensated pulse

Local oscillator laser needs to be coherentacross dispersed pulse width

Electronically enhanced laser phase noise

[W. Shieh et al., Opt. Exp., vol. 16, 15718 (2008)][C. Xie, Proc. OFC, OMT4 (2009)]



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Chromaticdispe

rsion

Clockrecovery

Retiming,resam

pling

Front-endcorrec

tions

A/D

A/D

A/D

A/D

+j

+j

Ix

Qx

Iy

Qy

PBS

x

y Polarization rotationSignal 1

Signal 2

Axx

x + Axy

y

Ayxx + Ayyy

PBSFiber

Jones matrix inversion



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Chromaticdispe

rsion

Clockrecovery

Retiming,resam

pling Hxx

Hyy

+

Hxy

+

Hyx

Front-endcorrec

tions

A/D

A/D

A/D

A/D

+j

+j

Ix

Qx

Iy

Qy

PBS

x

y Polarization rotationSignal 1

Signal 2

Axx

x + Axy

y

Ayxx + Ayyy

PBSFiber



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Chromaticdispe

rsion

Clockrecovery

Retiming,resam

pling Hxx

Hyy

+

Hxy

+

Hyx

Front-endcorrec

tions

A/D

A/D

A/D

A/D

+j

+j

Ix

Qx

Iy

QyFrequencylock

ing

Phasetrackin

g

Im{E}

Re{E}f0



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[T. Mizuochi et al., Proc. OFC, 2012 ]

Chromaticdispe

rsion

Clockrecovery

Retiming,resam

pling Hxx

Hyy

+

Hxy

+

Hyx

Front-endcorrec

tions

A/D

A/D

A/D

A/D

+j

+j

Ix

Qx

Iy

QyFrequencylock

ing

Phasetrackin

g

D

ecision/Decod

ing

A WORD ON FEC IN OPTICAL SYSTEMS


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FEC

decoder

BER = 210-3 BER = 10-16

-Log(Uncorrected BER)

-Log(CorrectedBER)

Hard decision, 7% Overhead

FEC correction threshold

Thats how most optical communications engineers view FEC:

Assumes hard-decision FEC Assumes independent errors

(sufficient scrambling wrt burst errors)

Problem:Soft-decision FEC

A WORD ON SOFT FEC IN OPTICAL SYSTEMS


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Thats what nonlinearities can do:(Outside the assumptions leading to the Gaussian Noise model)

[J. Cho et al., Optics Express, 7915 (2012)]



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Thats what nonlinearities can do:(Outside the assumptions leading to the Gaussian Noise model)

[A. Leven et al., Phot. Technol. Lett., 1547 (2011)]



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Back-to-back After 1600-km transmission

Gaussian-like signal statistics down to ~1E-5 even after 1600-km transmission

The performance of SD-FEC expected to be fully obtained.

MAJOR DSP ASIC MILESTONES IN OPTICS


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2005 2006 2007 2008 2009 2010 201110

0

101

102

Year

GateCounts(Million) ~70% per year

2

3

4

5

6

7

8

9

0 10 20 30 40 50 60

Sample rate [GS/s]

Numberofbit

Stated

ENOB

Nortel electronic pre-EDC 10G Tx (2005)

20GS/s DAC

ADC resolution vs. sample rate

Nortel 40Gb/s PDM-QPSK (2007)

20GS/s ADC/DSP

Alcatel-Lucent 112Gb/s (2010)

56GS/s ADC/DSP

70M+ gates


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5Multiplexing in optical

communication systems

SAME 5 DIMENSIONS FOR MULTIPLEXING


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AN EXHAUSTIVE LIST

Polarization

Time Quadrature

Physical dimensions

FrequencySpace

t

f

O E S C L

13000

1400 1500 1600

0.3

0.6

0.9

1.2

Wavelength [nm]

Loss[dB]

13601260 1460 1530

1565

1625

WAVELENGTH-DIVISION MULTIPLEXING (WDM)


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Orthogonality through non-overlapping frequency bins (WDM)

VARIOUS SUPERCHANNEL DEMONSTRATIONS


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1 Tb/s(2 subcarriers) 16-QAM

5.2 bit/s/Hz

3200 km transmission[Raybon et al., IPC12]

263 GHz

1.5 Tb/s(8 subcarriers) 16-QAM

5.7 bit/s/Hz

5600 km transmission[Liu et al., ECOC12]

1.2 Tb/s(24 subcarriers) QPSK

3.74 bit/s/Hz

7200 km transmission[Chandrasekhar et al., ECOC09]

300 GHz

ADC&DAC bandwid th & resolut ion Opt ical paral lel ism

200 GHz

1 Tb/s(4 subcarriers) 16-QAM

5.0 bit/s/Hz

2400 km transmission[Renaudier et al., OFC12]

200 GHz

Few carriers

High symbol rate

Large # of carriers

Lower symbol rateMod.

f

Mod.

Mod.

Mod.

Laser

f

+

Laser

Laser

Laser

f

f

f

OFDM IN OPTICAL COMMUNICATIONS


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Optical OFDM

f

All subcarriers modulated individually

Parallel optical hardware

f

Electrical OFDM

56 Gb/s net rate (65 Gb/s line rate)

32-QAM per subcarrier[Takahashi et al., OFC09]

All subcarriers modulated at oncef

f

Mod.Laser

Mod.

Comb

ff

f

f

f

Mod.

Mod.

Mod.

60 GHz

448 Gb/s (10 subcarrier) 16-QAM5 bit/s/Hz2000 km transm.[X. Liu et al., OFC10]

65 GHz

606 Gb/s (10 subcarrier) 32-QAM7 bit/s/Hz2000 km transm.[X. Liu et al., ECOC10]

1.2 Tb/s (24 subcarrier) QPSK3 bit/s/Hz7200 km transm.[S. Chandrasekhar et al., ECOC09]

300 GHz

POLARIZATION-DIVISION MULTIPLEXING (PDM)


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A standard single-mode fiber supports two orthogonal polarizations

One can transport independent signals in both polarizations, provided

that one can separate them again at the receiver in the presence of

random polarization rotations within the transmission fiber

Polarization diversity receivers detect both polarizations

(see section on coherent detection below)

PDM increases spectral efficiency by a factor of 2

SPACE-DIVISION MULTIPLEXING (SDM)


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Spatially disjoint optical beams are orthogonal

Multiple fiber strands

Multi-core fiber

http://www.occfiber.com/

Spatially overlapping optical beams can also be orthogonal

Multiple modes in multi-mode fiber

provided that one can selectively excite and detect those modes


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6Capacity limits

THE NONLINEAR SHANNON LIMIT


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96

Increasing the signal power (i.e. the SNR) creates signal distortions from fiber

nonlinearity, eventually limiting system performance

SNR [dB]

CapacityC

[bits/s] Maximum

capacity

Signal launch power [dBm]

Tx Rx

Distributed Noise

C = B log2(1 + SNR)

Nonlinear distortions

Quantum mechanics dictates a lower bound on amplifier noise

[R.-J. Essiambre et al., Phys. Rev. Lett. (2008) or J. Lightwave Technol. (2010)]

AN LOWER BOUND ESTIMATE FOR THE SHANNON LIMIT Assume ring constellations


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Assume ring constellations

Deterministic signal back-propagation to remove (most of the) channel memory

Numerical solution of nonlinear Schrdinger equation Numerical statistics

SNR [dB]

CapacityC

[bits/s] Maximum

capacity

Signal launch power [dBm]

Tx Rx

Distributed Noise

[R.-J. Essiambre et al., Phys. Rev. Lett. (2008) or J. Lightwave Technol. (2010)]

0 5 10 15 20 25 30 35 40

SNR (dB)

Capacityperunitbandwidt

h

(bits/s

/Hz)

0

1

2

3

4

5

6

8

71 ring2 rings4 rings8 rings

16 rings

Numerical statistics

SOME EXAMPLE RESULTS


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0 5 10 15 20 25 30 35 40

SNR (dB)

Capacityperun

itbandwidth

(bits/s/Hz)

0

1

2

3

4

5

6

8

7

1 ring2 rings4 rings8 rings16 rings-0.2 -0.1 0 0.1 0.2

-0.2

-0.1

0

0.1

0.2

Imagpartoffield

[mW1/

2]

Real part of field [ mW1/2

]

-1 -0.5 0 0.5 1

-1

-0.5

0

0.5

1


]

Imagpartoffield[mW1/

2]

-2 -1 0 1 2

-2

-1

0

1

2


]

Imagpartoffield[m

W1/

2]

R.-J. Essiambre et al., Phys. Rev. Lett. (2008) or J. Lightwave Technol. (2010)

Note:Capacity maximum occurs at fairly high SNRs

VARIOUS CONTRIBUTIONS TO CAPACITY


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R.-J. Essiambre et al., J. Lightwave Technol. (2010)

SENSITIVITY ANALYSIS TO FIBER PARAMETERS


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Capacity is fairly insensitive to (heroic!)

improvements of fiber loss, nonlinearity,

or dispersion

Dont waste your money improving

single-mode fiber...

[R.J.Essiambre and R.W.Tkach, Proc. IEEE, 2012]

THE RATE-REACH TRADE-OFF IN OPTICAL FIBER


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5

10

15

2100 1,000 10,000

Transmission distance [km]

Spectralefficiency[b/s/Hz]

Metro Long-haul Submarine

25

50

75

10

C-bandcapa

city[Tb/s]

THE RATE-REACH TRADE-OFF IN OPTICAL FIBER


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5

10

15

2100 1,000 10,000

Transmission distance [km]

Spectralefficiency[b/s/Hz]

Metro Long-haul Submarine

25

50

75

10

C-bandcapa

city[Tb/s]

Tutorial Optical Transmission Systems Peter J Winzer

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Transcript of Tutorial Optical Transmission Systems Peter J Winzer