Assessment of Intrachannel Nonlinear Compensation for 112 Gb/s Dual-Polarization 16QAM Systems

For 112 Gb/s dual-polarization 16-ary quadrature amplitude modulation systems, the performance and complexity of the low-pass filter (LPF)-assisted digital back-propagation (DBP) algorithm for mitigating intrachannel fiber nonlinearity are investigated. Comparison is made with both linear equalization and the standard DBP algorithm for single-channel transmission (simulation and experiment) and for wavelength division multiplexed (WDM) transmission with channel spacings of 50 and 35 GHz (simulation). With optimized values for the algorithm parameters, the simulation results show that, compared to linear equalization, the 0.2 steps/span LPF-assisted DBP algorithm can increase the transmission distance by 84%, 40%, and 17% for a single-channel, 50 GHz channel-spaced WDM, and 35 GHz channel-spaced WDM transmission, respectively. These improvements in the transmission distance are 54%, 75%, and 77% of those achieved with the 4 steps/span standard DBP algorithm but at considerably lower complexity. Single-channel experimental results show that the 0.25 steps/span LPF-assisted DBP algorithm can increase the transmission distance by 43%, which is 68% of the improvement achieved with the 4 steps/span standard DBP algorithm. Compared to the standard DBP algorithm, the LPF-assisted DBP algorithm can allow a reduction in the number of steps/span, but with an increased computational complexity for each step. The two DBP algorithms are compared in terms of the number of real multiplications per bit, thus allowing the algorithm with lower complexity to be determined at a given level of performance.