Logarithmic step-size based digital backward propagation in N-channel 112Gbit/s/ch DP-QPSK transmission

We propose and numerically investigate logarithmic step-size distribution for implementing efficient digital backward propagation (DBP) algorithm using split-step Fourier method (SSFM). DBP is implemented in N-channel 112Gbit/s/ch dual-polarization quadrature-phase-shift-keying (DP-QPSK) transmission over 2000km standard single mode fiber (SMF) with no in-line optical dispersion compensation. This algorithm is compared with 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-efficiency transmission systems with 28GBaud and 56GBaud per-channel rates. The logarithmic step-size based DBP algorithm depicts efficient mitigation of chromatic dispersion (CD) and non-linear (NL) impairments. Benefit of the logarithmic step-size is the reduced complexity and computational time for higher baud rates.