Efficient compensation of chromatic dispersion and nonlinearities using logarithmic digital backward propagation in N-channel DWDM 1.12Tbit/s DP-QPSK transmission

We propose and numerically investigate the logarithmic step-size distribution for implementing an efficient digital backward propagation (DBP) algorithm using the split-step Fourier method (SSFM). DBP is implemented in N-channel dual-polarization quadrature-phase-shift-keying (DP-QPSK) transmission over 2000 km standard single-mode fiber (SMF) with no in-line optical dispersion compensation. This algorithm is compared with the constant step-size modified DBP (M-SSFM) algorithm in terms of efficiency, complexity and computational time. Furthermore, we investigate the same-capacity and same-bandwidth transmission systems with 14 Gbaud (GBd), 28GBd and 56GBd per-channel rates. The logarithmic step-size based DBP algorithm depicts efficient mitigation of chromatic dispersion (CD) and nonlinear (NL) impairment. The benefit of the logarithmic step-size is the reduced complexity and computational time for higher baud rates.