40-GHz pulse source based on XPM-induced focusing in normally dispersive optical fibers

We theoretically and experimentally investigate the design of a high-repetition rate source delivering well-separated picosecond pulses thanks to the nonlinear compression of a dual-frequency beat signal within a cavity-less normally dispersive fiber-based setup. This system is well described by a set of two coupled NLS equations for which the usual normally dispersive defocusing regime is turned in a focusing temporal lens through a degenerated cross-phase modulation effect. More precisely, the temporal compression of the initial beating is performed by the combined effects of normal GVD and XPM-induced nonlinear phase shift yield by an intense beat-signal on its weak out-of-phase replica copropagating with orthogonal polarizations. This adiabatic reshaping process allows us to generate a 40GHz well-separated 3.3ps pulse train at 1550nm in a 5km long normally dispersive fiber.