Theoretical modeling of dispersion uncompensated CO-OFDM transmission with coarse-step DBP based intra-channel nonlinearity compensation

• We models the transmission of dispersion unmanaged CO-OFDM with coarse-step intra-channel DBP.
• Applying this model, system performance and optimum compensation factor can be obtained very fast.
• Q discrepancy between simulation and theory are within 0.62 dB, showing quite good accuracy.
• Our results also show negligible influence of ASE and nonlinear signal noise interaction.

In this paper, we derive an accurate analytical expression for evaluating the transmission performance of dispersion uncompensated coherent optical OFDM (CO-OFDM) systems with intra-channel fiber nonlinearity mitigation based on coarse-step digital back propagation (CS-DBP). This theoretical model is substantiated through numerical simulations for the polarization-division multiplexed (PDM) 16-QAM systems with various DBP step size and processing bandwidth. After 1000 km dispersion uncompensated SSMF transmissions, the maximum Q factor discrepancy between simulation and analytical results is only 0.62 dB, showing quite good evaluation accuracy. In addition to the theoretically modeling and numerically substantiations, the impacts of ASE and nonlinear signal–noise interaction (NSNI) on CS-DBP are also investigated. It is found that, unlike ideal DBP with fine enough processing step size, the influence of NSNI on 25 GHz dispersion uncompensated CO-OFDM transmissions with commonly used CS-DBP can be negligible. Moreover, our results also show that the influence of ASE on the optimum nonlinear compensation factor is only noticeable for very small launch power levels where the system performance would still not be impacted.