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Analytical Model for 100 Gb/s
Discrete Multi-Tone Modulation
40Gb/s and 100Gb/s Fiber Optic Task Force
IEEE 802.3bm Interim Session
Phoenix, Arizona
23-24 January 2013
Ilya Lyubomirsky
Finisar Corp.
23-24 January 2013 Fiber Optic Task Force2
Outline
■ Objectives
■ DMT Analytical Model
■ Impact of Thermal and Shot Noise
■ Impact of Clipping Nonlinearity
■ Impact of RIN
■ Comparison of 100Gb/s DMT with PAM-M
■ Conclusion
23-24 January 2013 Fiber Optic Task Force3
Objectives
■ Continue higher order modulation analysis development in
nicholl_01b_0312, ghiasi_01a_0912, and
lyubomirsky_01a_1112_optx
■ Gain physical insights from analytical models
■ Compare performance of 802.3bm SMF PMD alternatives
23-24 January 2013 Fiber Optic Task Force4
100 Gb/s DMT System Architecture
Source: J. Wei, et. al., “Performance Studies of 100 Gigabit Ethernet Enabled by
Advanced Modulation Formats,” IEEE 802.3, Next Gen. 40Gb/s and 100Gb/s
Opt. Ethernet Study Group, ingham_01_0512_optx, May, 2012
23-24 January 2013 Fiber Optic Task Force5
DMT Effective SNR Model
23-24 January 2013 Fiber Optic Task Force6
DMT Effective SNR Model (continued)
Clipping
Qc(x)Laser
23-24 January 2013 Fiber Optic Task Force7
DMT Effective SNR Model (continued)
PD
23-24 January 2013 Fiber Optic Task Force8
DMT Effective SNR Model (continued)
Clipping
Qc(x)
Bussgang Theorem: Clipping noise ncl(t)
uncorrelated with x(t)
Closed form formulas derived in E. Vanin, “Performance evaluation of intensity
modulated optical OFDM system with digital baseband distortion,” Opt. Exp.,
Vol. 19, No. 5, pp. 4280-4293, 2011
23-24 January 2013 Fiber Optic Task Force9
Monte-Carlo Simulation Parameters
Parameter Value
Sampling rate, Fs 60 Gs/s
FFT size, N 128
Number of nonzero subcarriers, Nsc 55
High freq. subcarriers padded to zero 8
DC subcarriers padded to zero 1
Cyclic prefix, CP 4
Clipping ratio, Rcl 8 dB
QAM modulation order, M 16
Noise bandwidth, f 25.8 GHz
Thermal noise density, Sth 16 pA/sqrt(Hz)
Photodiode responsivity, 0.8 A/W
23-24 January 2013 Fiber Optic Task Force10
100 Gb/s DMT Analytical Model Results
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
-14.5 -13.5 -12.5 -11.5 -10.5 -9.5
BER
Average Optical Power (dBm)
Analytical Model, Thermal Noise
Monte-Carlo Simulation, Thermal Noise
Analytical Model, Thermal+Shot Noise
Monte-Carlo Simulation, Thermal+Shot Noise
23-24 January 2013 Fiber Optic Task Force11
Optimization of Clipping Ratio
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
0 2 4 6 8 10 12 14 16
BER
Clipping Ratio (dB)
P = -12 dBm
P = -11 dBm
P = -10 dBm
Clipping
Noise
Dominates Thermal
Noise
Dominates
23-24 January 2013 Fiber Optic Task Force12
Impact of RIN
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
-14 -13.5 -13 -12.5 -12 -11.5 -11 -10.5 -10 -9.5 -9
BER
Average Optical Power (dBm)
No RIN
RIN = -143 dB/Hz
RIN = -140 dB/Hz
RIN = -137 dB/Hz
Rcl = 8 dB
23-24 January 2013 Fiber Optic Task Force13
Analytical Model for PAM-M
For optimum receiver thresholds, the symbol error probability is determined
by an average over all the PAM eye Q-factors
2
0
21022
1
1
1
)(1
2
)()(
f)102(
1
1
1
2
2-M0,...,k, Q(k)
M
k
s
k
RIN
kthk
avkk
kk
kk
kPM
P
kQerfckP
IqIS
ER
ER
M
RPII
II
-0.5 0 0.5-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
Time (UI)
Am
plit
ude
PAM4 @50G with BT4 25G BW
0
1
2
3
I0
I1
I2
I3
23-24 January 2013 Fiber Optic Task Force14
100 Gb/s PAM-M Analytical Model Results
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
-16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5
BER
Average Optical Power (dBm)
PAM-8, no RIN
PAM-8, RIN = -143 dB/Hz
PAM-8, RIN = -140 dB/Hz
PAM-4, no RIN
PAM-4, RIN= -140 dB/Hz
PAM-4, RIN = -137 dB/Hz
ER= 10 dB
23-24 January 2013 Fiber Optic Task Force15
100 Gb/s DMT versus PAM-4 and PAM-8
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
-15 -14 -13 -12 -11 -10 -9 -8 -7
BE
R
Average Optical Power (dBm)
DMT, No RINDMT, RIN = -143 dB/HzPAM-8, No RINPAM-8, RIN = -143 dB/HzPAM-4, No RINPAM-4, RIN = -143 dB/Hz
23-24 January 2013 Fiber Optic Task Force16
Conclusions
■ We presented an analytical model for DMT modulation
based on an effective SNR approach
■ The model provides a useful baseline for performance, as
well as physical insight on the interplay of DMT system
parameters
