Fiber Nonlinearity Compensation: DBP Versus Link-Optimized OPC in Coherent Transmission

In this letter, we numerically compare the system performance of nonlinearity-compensated transmission based on digital back-propagation (DBP) and optical phase conjugation (OPC) technique in coherent transmission with lumped erbium doped fiber amplifiers (EDFAs). The tested transmission for DBP is a conventional dispersion-managed link, while it is an optimized design, the so-called dispersion inversion link for OPC-based system. Both of them have the same amount and type of fibers, and thus the same transmission reach. The numerical results show that DBP-aided systems have better performance for a shorter transmission reach while OPC technique presents its performance advantage when the transmission reach is increased. For a given transmission distance, the performance of OPC systems can further be improved by introducing additional OPCs. Results of 3840-km ( $48\times 80$ km) dispersion-managed transmission show that only mid-link OPC is enough to get similar performance with full-field DBP. By employing 6-OPCs in the links, the SNR of OPC-based system outperforms DBP by up to 1.9dB, while this SNR advantage will increase to 3dB after 5760-km ( $72\times 80$ km) transmission.