Simplified Volterra series-based nonlinear equalization for IM/DD systems

The frequency chirp of Direct modulation laser (DML) introduces nonlinear interference to the signal, and traditional linear equalizers such as FFE cannot handle nonlinear noise and perform poorly, so nonlinear equalizers are needed to process it. This paper proposes a new simplified Volterra nonlinear equalizer (VNLE) method for the chirp characteristics of DML systems-S-VNLE. We experimentally use AWG to generate 64Gb/s PAM4 signals on a 1550nm DML, and use a nonlinear equalizer VNLE, DP-VNLE, S-VNLE, and linear equalizer FFE at the receiver, results showed that S-VNLE had the highest sensitivity improvement of 0.5dB compared to DP-VNLE, with the same complexity as DP-VNLE and a 50% reduction compared to VNLE.