The effect of second order signal-noise interactions in nonlinearity compensated optical transmission systems

  • Mohammad Al-Khateeb (Creator)
  • Mary McCarthy (Creator)



We have simulated (using VPITransmissionMaker 9.3 and Matlab) 112Gbps PM-QPSK system operating at 1550nm carrying two Pseudo Random Bit Sequences (PRBS) on each polarization. The transmitted signals were Nyquist pulse shaped with a roll off factor of 0.01, and the total number of transmitted bits were 215 bits per polarization. The modulated optical signals have been simulated with 16 samples per symbol, and we have simulated two types of systems: (system A) propagates signals into 12x100km dispersion uncompensated fiber (α=0.2dB/km) with EDFA installed at the end of each span that have Noise Figures (NF) of 6 dB equivalent to noise power spectral density of 5.1x10-17W/Hz; (system B) propagates the signals in 12x100km lossless fiber (α=0dB/km) with noise power spectral density injected by the end of each span equal to 1.1x10-17W/Hz; this noise power spectral density was selected so that (system B) achieves the same optimum received SNR as (system A) in the case of electronic dispersion compensated (EDC) system. The fiber in both systems had a nonlinear factor γ0=1.33/W/km, chromatic dispersion of 16ps/nm/km, zero PMD, and the step size of the fiber was calculated with a maximum nonlinear phase change of 0.01degree. Convergence tests with larger simulated fiber step size (0.5 degree as maximum phase change) resulted in inaccurate results (degraded SNR) for optical signal powers above 10dBm regardless of the noise power. The ideal OPC modules were simulated by conjugating the optical field.
At the receiver side, signals were coherently detected with 8 samples per symbol to enable DBP of full deterministic signal-signal nonlinearity compensation, convergence test have been conducted to conclude that sampling rate over 6 samples per symbol will have the same maximum Q2 factor. Coherently detected signals were passed to the DSP module, implemented in Matlab, to: compensate for dispersion (in the case of EDC), or to perform DBP with 120 steps/span (in case of DBP nonlinearity compensated system), or nothing (in the case of OPC nonlinearity compensated system). The signals then were down-sampled to 2 samples per symbol; then passed to a phase recovery block which was performed using Viterbi-Viterbi algorithm with an averaging window of 21. The Q2 of received signals were calculated from the Error Vector Magnitude (EVM). System A uses DBP to fully compensate signal-signal nonlinear interactions, OPC solution will not be used in this system since power profile symmetry condition is not satisfied to allow full compensation of signal-signal nonlinear interactions. System B deploys different ideal nonlinearity compensation techniques: DBP, 1-OPC, 3-OPC’s, and 11-OPC’s.

Funding: Engineering and Physical Sciences Research Council (EP/J017582/1, EP/L000091/1)

Projects: UNLOC, PEACE
Date made available14 Apr 2016
PublisherAston Data Explorer
Temporal coverage1 Nov 2015 - 14 Jan 2016
Date of data production14 Jan 2016
Geographical coverageBirmingham, United Kingdom

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