On the Complexity Reduction of the Second-Order Volterra Nonlinear Equalizer for IM/DD Systems

To cope with the various nonlinear signal distortions in intensity-modulation/direct-detection transmission systems, a theoretical analysis on the Volterra nonlinear equalizer (VNLE) is provided, focusing on computational complexity aspects. The analysis yields a simple reduced-complexity scheme for the secondorder VNLE (R2-VNLE) based on a performance-complexity tradeoff. An experimental verification is performed with single-sideband 28-GBaud PAM-4 signals, generated by an electroabsorption modulated distributed-feedback laser, over transmission distances of up to 80 km of standard single-mode fiber in the C-band. A comparison of the results for different equalization schemes, including a signal-signal beat interference mitigation technique, shows superior performance for the R2-VNLE.