Path-average theory of intra-channel four-wave mixing

Summary form only given. Recently discovered intra-channel four-wave mixing (FWM) is one of the major limiting factor for dispersion-managed (DM) bit-overlapped return-to-zero transmission. Bit-overlapping due to huge pulse spreading during propagation is typical for systems using standard fibers at bit rates of 40 Gbit/s and more. Intra-channel FWM manifests itself by generation of shadow ("ghost") pulses in the middle of the "zero" time slots due to FWM between spectral components within a single channel. We develop a simple path-average theory of intra-channel FWM that describes initial growth and slow (path-averaged) oscillations of FWM components. Our theory is also capable to identify regimes with suppressed FWM. As a particular example we consider the fiber system design studied previously. At high bit rate of 40 Gbit/s and more carrier pulses periodically experience large spreading in time with corresponding reduction of the nonlinear effects. In the leading approximation the signal evolves in a quasi-linear way. Therefore, variations of signal parameters over one period can be averaged out.