Improved Compensation of Intrachannel Four-Wave Mixing in Dispersion-Managed Transmission Links with Mid-Span Optical Phase Conjugation

Abstract

Recently, a novel approach to satisfy the nonlinearity compensation criteria by mid-span optical-phase-conjugation (OPC) was proposed and excellent transmission performance was achieved, there the OPC propagation symmetry was obtained through optimized dispersion management with inverse-dispersion fiber (IDF). In this work, we numerically investigate the possibilities of using dispersion-compensating fiber (DCF) instead of IDF for construction of the link. Nonlinearity compensation effectiveness of the two links are compared with respected to the intrachannel four-wave mixing (IFWM) induced intensity fluctuation of the ‘1’ bits and the generation of the ghost pulse. We find that, by launching different powers (or energy of a limited bits) into the spans before and after the OPC, nonlinearity mismatch between the spans of the DCF-managed link can be counterbalanced with significantly improved transmission performance. For a given input energy, there exists an optimum ratio of the energies into the spans before and after the OPC, at which optimum nonlinearity compensation can be achieved, and the compensation effectiveness is very close to that of the IDF-managed link. Further studies show that the optimum energy ratio increases with the input energy but is independent of the span number of the link.

Keywords: optical-phase-conjugation, dispersion management, dispersion-compensating fiber, inverse-dispersion fiber, intrachannel four-wave mixing, nonlinearity compensation