Perturbation-Based Joint SPM and XPM Compensation for Superchannel System

In contrast to digital backpropagation (DBP), perturbation-based nonlinear compensation (PB-NLC) is a low-complexity alternative to mitigate fiber Kerr nonlinearity. In this letter, we experimentally demonstrate a novel receiver-side perturbation approach to cancel the self-phase modulation and cross-phase modulation for superchannel systems using three independent receivers. With the inverse perturbation theory, we develop a nonlinear compensation model that does not require knowing the transmitted symbols and therefore avoids the penalty from the estimation error. We implement the PB-NLC in a $3\times 24.5$ GBaud 64-QAM comb-based superchannel system spaced at 25 GHz. Compared to chromatic dispersion compensation, the full PB-NLC achieves a 0.2 dB Q2 factor gain after 1200 km transmission, which is equivalent to the single-channel DBP operating at 1 step per span.