Frequency-Domain Volterra-Based Equalization Structures for Efficient Mitigation of Intrachannel Kerr Nonlinearities

Toward reduced-complexity digital implementation, frequency domain Volterra-based nonlinear equalization (VNLE) structures for multistep fiber nonlinearity compensation are proposed. In the cascade structures, nonlinear equalization is performed before (cascade-1) or after (cascade-2) the dispersion compensation in each step. Superior performance with the shorter discrete Fourier transform (DFT) lengths and fewer equalization steps compared to the conventional VNLE with parallel structure is demonstrated in a transmission experiment. The experimental results are obtained for 256 Gb/s single-carrier dual-polarization 16-ary quadrature-amplitude-modulation with root-raised-cosine pulse shaping and a roll-off factor of 0.1. The new cascade structures demonstrate superior robustness to insufficient DFT lengths and/or a limited complexity budget. Compared to the conventional parallel arrangement of linear and nonlinear compensation filters, the cascade-1 structure provides more than 90% complexity reduction without any notable performance penalty. The structure enables the extension of the transmission reach by 1570 km, a 48% increase compared to the linear solution that uses only electronic dispersion compensation.