Digital Nonlinear Compensation Based on the Modified Logarithmic Step Size

In this paper, we investigate the digital backward propagation (DBP) nonlinear compensation (NLC) based on the modified logarithmic step size distribution. Different from regular constant step size, we use the logarithmic non-constant step size distribution in DBP. The compensation performance is investigated with Nyquist wavelength division multiplexing (NWDM) system. The modified logarithmic step size distribution is proposed and studied by introducing an attenuation adjusting factor k. As a proof of the concept, the optimal k factor is studied by simulation results with the noise figure, the input power, the transmission distance, the fiber attenuation, the span length, the step number per span, the dispersion value, the baud rate, the calculated sub-channels, the pulse shape and the modulation formats. Reduced complexity and improved performance is observed by using the modified logarithmic step size distribution. Compared with constant step nonlinear compensation, the improved bit-error-ratio (BER) performance and Q-value for our scheme is demonstrated by 3 × 50-Gb/s NWDM polarization division multiplexing quadrature phase shift keying (PDM-QPSK) signal with 1120-km single-mode fiber-28 (SMF-28) transmission and Erbium-doped fiber amplifier (EDFA)-only amplification.