RESUMO
We investigate the combination of a nonlinear frequency division multiplexed (NFDM) transmission scheme with midpoint optical phase conjugation (OPC), and show that midpoint OPC introduces power enhancement by compensating for nonlinear impairments. It offers a degree of freedom to have a flexible power normalization factor, Pn. Optimizing Pn helps minimize the signal-noise mixing in nonlinear Fourier transform processing for a specific launch power, resulting in improving the system performance significantly. The mid-OPC NFDM system can provide 4.5 dB and 5.6 dB advantages in Q-factor as compared to the conventional NFDM system when the transmission fiber is standard single-mode fiber and a fiber with optimum dispersion, respectively. Mid-OPC NFDM can also offer higher spectral efficiency at a longer transmission reach due to the shorter guard interval.