Four-wave mixing in dispersion-managed return-to-zero systems

Four-wave mixing (FWM) in wavelength-division multiplexed systems with strong dispersion management and loss-amplification is comprehensively studied. The methods described apply to both soliton and quasilinear return-to-zero systems. A linear model is introduced that describes the resonant growth and saturation of the FWM products. The model yields a resonance condition between the channel separation and the amplifier spacing that, in certain parameter regions, reproduces for strongly dispersion-managed systems the phase-matching condition that is valid for classical solitons. As the dispersion map's strength increases, the residual FWM decreases, but the FWM amplitude is found to increase inversely to the average dispersion in the system. A reduced linear model is also introduced that contains the basic features of FWM processes. Comparisons of both models with direct numerical simulations of the full nonlinear system demonstrate excellent agreement.