A novel sparse Volterra model based fiber nonlinear equalization method for polarization-division-multiplexed CO-OFDM systems

In this paper, we address the challenges posed by fiber nonlinearity, specifically self-phase modulation (SPM) and cross-phase modulation (XPM), for a polarization-division-multiplexed coherent optical orthogonal frequency division multiplexing (PDM CO-OFDM) system using a novel sparse Volterra method. Though COOFDM combined with PDM offers high spectral efficiency and is a promising technology for next-generation optical communication, it is susceptible to fiber nonlinear effects. We introduced an improved sparse Volterra method, employing the orthogonal search approach to simplify the model's coefficients. This approach helps manage the complexity associated with compensating nonlinear impact for PDM CO-OFDM system. Additionally, a multi-train sequence method is proposed to enhance the compensator's effectiveness, especially in the context of wavelength-division multiplexing (WDM) systems. The designed compensator is validated through numerous simulations, and a comparative analysis of bit error rate (BER) performance is conducted, considering sparse Volterra compensator, 1-th order Volterra method, and 3-th order Volterra method. The results demonstrated the efficacy of the proposed sparse Volterra model in mitigating nonlinear effects with evidently reduced complexity.