Nonlinearity Compensation of 224 Gb/s Dual-Polarization 16-QAM Transmission Over 2700 km

Long-haul transmission for distances greater than 2000 km is investigated for a 224 Gb/s dual-polarization 16-ary quadrature-amplitude-modulation signal, using ultralarge effective area fiber with span lengths of 75.5 km and distributed Raman amplification. By using nonlinear compensation (NLC) based on the low-pass filter (LPF) assisted digital back propagation (DBP) algorithm, a transmission distance of 2700 km is demonstrated with moderate complexity (0.25 backpropagation steps/span) and good robustness to deviation of the algorithm parameters from their optimum values. Compared to the standard DBP algorithm, the LPF assisted DBP algorithm can allow a reduction in the number of NLC 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 for a given level of performance.