Post on 03-Feb-2022
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
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
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
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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)
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Dispersion Precompensation
Signal Transmitted Signal after 1600 km of NDSFWith no optical compensation.
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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
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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.
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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
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40G/100G Agile Optical EngineBinary to dual polarization E-field
Full E-field to Digital Transducer
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.)
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
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
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