Low-complexity nonlinear equalizer based on absolute operation for C-band IM/DD systems

Abstract: The intensity-modulation/direct-detection transmission system operating in the Cband suffers from nonlinear waveform distortions induced by fiber chromatic dispersion due to the square-law detection. The Volterra nonlinear equalizers (VNLEs) can be used at the receiver to compensate for such distortions. However, the major concern about the equalizers is their huge implementation complexity. In this paper, we propose and demonstrate a low-complexity nonlinear equalizer based on the absolute operation for a cost-sensitive IM/DD system. In this equalizer, the cross-beating product terms (required in VNLE) are replaced with the absolute operation of the sum of two input samples. We evaluate the performance of the proposed equalizer over a 56-Gb/s 4-ary pulse amplitude modulation transmission system implemented by using 1.5-μm directly modulated laser or electro-absorption modulated laser. The results show that the proposed equalizer performs similar to the 2nd-order diagonally-pruned VNLE, but lowers the implementation complexity by >20%. We also show that the proposed equalizer outperforms the VNLE when the implementation complexities of the two nonlinear equalizers are similar.