Mitigating Nonlinear Impairments in High-speed Optical Communication Systems via Volterra Nonlinear Equalizer

Abstract

This paper presents an in-depth investigation into applying a frequency domain Volterra series nonlinear equalizer
(FD-VNLE) to mitigate nonlinear impairments in optical communication systems operating at high speeds. The study
aims to address the issues presented by nonlinear effects, specifically self-phase modulation (SPM), which significantly
degrades system performance at higher power levels. A comprehensive mathematical model of the FD-VNLE was
developed to provide theoretical insight, while its implementation was carried out using MATLAB co-simulated with
OptiSystem. The performance of the 40 Gbps dual-polarization quadrature phase shift keying (DP-QPSK) system was
rigorously evaluated, focusing on critical performance metrics like bit error rate (BER) and quality factor (Q-factor).
Simulation results indicated that without nonlinear compensation, the system experienced performance degradation
beyond an input power of 12 dBm, where the optimum BER was 10¡77 and the Q-factor was 18. However, deploying FDVNLE and applying digital signal processing (DSP) successfully reduced the BER to 10¡300 and improved the Q-factor to
100, maintaining consistent performance up to an input power of 17 dBm. The DSP further diminished residual phase
noise and significantly improved the reliability of the system. These findings highlight the promise of FD-VNLE as a
powerful tool for enhancing the efficiency and scalability of next-generation high-speed, long-distance optical networks.