Pattern-Dependent Nonlinear Phase Noise Pre-Compensation for Power Budget Improvement in High-Speed Coherent PONs

Coherent systems with large capacity and high receiver sensitivity are promising candidates for high-speed passive optical networks (PONs). However, increasing the launch power in high-speed coherent PONs to improve access capability leads to serious nonlinear phase noise due to the self-phase modulation (SPM). This nonlinear phase noise is exacerbated and becomes pattern-dependent in the presence of bandwidth limitation and chromatic dispersion (CD). The conventional nonlinear pre-compensation (NLPC) scheme, considering only the current state signal power, is insufficient for mitigating the pattern-dependent nonlinear phase noise. In this paper, we introduce a novel pattern-dependent NLPC (PD-NLPC) scheme implemented utilizing a low-complexity look-up table (LUT) to mitigate the impact of pattern-dependent nonlinear phase noise induced by SPM, bandwidth limitation, and CD in both single-polarization (SP) and dual-polarization (DP) systems. Both simulation and experiment are performed using 32 Gbaud SP and DP 16QAM signals over 40 km single-mode fiber (SMF) transmission in C-band to demonstrate the effectiveness of the proposed scheme. Experiment results show that the PD-NLPC scheme increases the achievable power budget by 1.3 dB and 1.1 dB for 32 Gbaud SP and DP 16QAM signals, respectively, compared to the uncompensated scheme, and by 0.8 dB and 0.6 dB compared to the conventional NLPC scheme.