Nortel Confidential Information

BUSINESS MADE SIMPLE

1

DSPA Disruptive Technologyfor Optical Transceivers

Kim RobertsIan Roberts

2

NoiseLimited

Transmission

> Early fibers had losses measured in dB/meter> Given the very finite amount of optical power that could be

coupled into the fibers, received powers quickly became very low.

> Thermal noise in the receiver limited the bandwidth and distance for optical transmission.• E.g. 1 Mb/s along 10 meters, experiments at Harlow Labs

FD-135 used Duobinary Coding in 1983to mitigate Modal Dispersion on

Multimode fiber

Proakis, Digital Communications

SuperDecoder

Decision Feedback

Winters et al, IEEE Communications Magazine, June 1993

6

Forward Error Correction to Mitigate Noise

1 2 3 4 5 6 7 810

−15

10−10

10−5

100

Uncoded

Q

BE

R

Uncoded

1 2 3 4 5 6 7 810

−15

10−10

10−5

100

Uncoded

Q

BE

R

BCH−1BCH-1

Uncoded

1 2 3 4 5 6 7 810

−15

10−10

10−5

100

Uncoded

Q

BE

R

BCH−1

BCH−3BCH-3

BCH-1

Uncoded

1 2 3 4 5 6 7 810

−15

10−10

10−5

100

Uncoded

Q

BE

R

BCH−1

BCH−3RSG.975 BCH-3

BCH-1

Uncoded

1 2 3 4 5 6 7 810

−15

10−10

10−5

100

Uncoded

Q

BE

R

BCH−1

BCH−3RS

BCH−20

G.975

BCH-20

BCH-3

BCH-1

Uncoded

1 2 3 4 5 6 7 810

−15

10−10

10−5

100

Uncoded

Q

BE

R

BCH−1

BCH−3RS

BCH−20BCH−2⊗BCH−3

G.975

P-FECBCH-20

BCH-3

BCH-1

Uncoded

Peak Signal to RMS Noise Ratio

Log

Bit

Erro

r Rat

e af

ter F

EC

7

Traditional Solution for Dispersion:Optical Compensation Modules

Maximum Likelihood Sequence EstimationMLSE

> M.Cavallari, C.R.S.Fludger, P.J.Anslow, Electronic signal processing for differential phase modulation formats, Optical Fiber Communication Conference, (Feb 2004)

Coherent to the E-Field

> Major sources of degradation are linear with respect to the optical E-field.• Linear and invertible functions• Linear functions are commutative

> Linear transducers can be built• Digital to E-field• E-field to digital

> Therefore, linear digital filtering can fully compensate

Linear Conversion from Digital to E-Field

11

Dispersion Eliminator: WARP ASIC

0.13 μm BiCMOS

2.5 Mb High Speed Memory2.0 M Gates

6 T Ops per second

Two 20 Gs/s 6 bit DAC

17 Watts

Linear and nonlinear pre-compensation of 10 Gb/s±80,000 ps/nm (2 dB penalty point)

12

Dispersion Precompensation

Signal Transmitted Signal after 1600 km of NDSFWith no optical compensation.

13

10 Gb/swith no Traditional Dispersion Compensation

Eye diagrams after transmission over standard G.652 fiber with Nortel WARP processing.

0 Km 1600 km 3200 km 5120 km

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SPM Precompensation, 1280 km

5.0

7.0

9.0

11.0

13.0

15.0

-5.0 -3.0 -1.0 1.0 3.0 5.0

Average Launch Power dBm

Req

uire

d O

SNR

at 1

E-3 Linear Compensation Only

With SPM CompensationReference Line

15

E-Field to Digital Transducer

> Two phases: Real and Imaginary (I and Q)• Best detected by mixing with a local oscillator

> Two polarizations

> Four dimensions fully span the E-field in a single mode fiber.

16

Coherent Detection

QX Pol

I

I Y Pol

Q

17

18

A/D and Filter ASIC

90 nm CMOS

20 M Gates

12 T Ops per second

Four 20 Gs/s 6 bit ADC

21 Watts

Linear and nonlinear post-compensation of 40 Gb/s±80,000 ps/nm, 25 ps mean PMD, 2 dB mean PDL

19

40G/100G Agile Optical EngineBinary to dual polarization E-field

Full E-field to Digital Transducer

20

40 Gb/s Coherent Dual Pol QPSK Modem

Real-time PMD tracking> 1000 km of NDSF

> 10G, 40G, and 100G at 50 GHz spacing

> JDS PMD emulator

22

PMD Tracking

2323

100G Dual Carrier

10G10GeDCO eDCO

AgileAgile100G100G

AgileAgile40G40G

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100 Gb/sModem

200G, 400G, 1000G

>Lower cost per bit

>More bits per fiber

>Larger packet streams

(From here on are my personal speculations and not product delivery commitments.)

Lightpath Bit Rate

The bit rate is the product of three dimensions

More Symbols per Second

>Faster A/D•11, 28, 56, … GBaud

>More gates of DSP

>CMOS riding Moore’s Law• Bipolar is too hot and does not have the gate count

Electronics for Processing

More Bits per Symbol

-2 -1 0 1 2-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

DP 16-QAM

4 bits x 2 Pol=8 bits per Baud

x 28.5 Gbaud= 228 Gb/s

I

Q

● 40 G

Spectral Efficiency

20

0.2

2

6

0.8

● 10 G

● 100 G

Spectral Efficiency is ultimately determined by OSNR

“The Channel Capacity of a Multispan DWDM System Employing Dispersive Nonlinear Optical Fibers and an Ideal Coherent Optical Receiver”, Jau Tang, JLT, Vol. 20, No. 7, July 2002

Multiple Carriers

>Coherent Frequency Selection• Two carriers with 16-QAM = 400 Gb/s

>OFDM

>New ideas are needed

OFDM

> Jolley et al, OFC 2005

> First Optical OFDM: Multimode fiber in Nortel lab.

Spectral Efficiency

Year of Product Introduction

Tb/sinC Band

Bits/sperHz

1995 2000 2005 2010 Future…0

1

2

3

4

0

5

10

15

20

● 10G10.7 Gb/s @ 50 GHz

●

● 46 Gb/s @ 50 GHz

112 Gb/s @ 50 GHz ●

224 Gb/s @ 50 GHz ●

448 Gb/s @ 80 GHz ●

525

1000 Gb/s @ 170 GHz ●6

100G Dual Carrier Real Time Data> 1000 km of NDSF

> 10G, 40G, and 100G at 50 GHz spacing

> JDS PMD emulator