Intra-channel Fiber Nonlinearity Mitigation Based on DBP in Single Channel and WDM Coherent Optical Transmission Systems Using Different Pulse Shapes

摘要

We numerically investigate intra-channel fiber nonlinearity mitigation using single-span step size digital backward propagation (DBP) in 112 Gb/s polarization-division-multiplexed-quadrature-phase-shift-keying (PDM-QPSK) coherent optical transmission systems. The DBP performance in single channel and wavelength-division-multiplexed (WDM) systems using non-return-to-zero (NRZ) or 50% return-to-zero (RZ) pulses are analyzed and compared. Results show that, the DBP can benefit the transmission system with improved Q -factor and enlarged input optical power range. This improvement for WDM system is poorer than that for single channel system, and the DBP performs even worse in WDM system with narrower channel spacing. Further studies show that single-span step size DBP can bring more system improvement for NRZ-PDM-QPSK system than 50% RZ-PDM-QPSK system, although the 50% RZ pulse is more resistant to fiber nonlinearities.