Optical solitons induced by cross-phase modulation

We investigated the nonlinear propagation in an optical fiber of two light beams of different frequency, opposite sign of GVD and comparable intensity. We found that cross-phase modulation may have a profound influence on the evolution of short pulses. Specifically, a bright soliton can propagate even in the otherwise forbidden normal dispersion regime, as long as it is coupled to a dark pulse in the anomalous dispersion regime. Numerical investigations have shown that this configuration can be destabilized by modulational instabilities after a relatively long distance. Conversely, cross-phase modulation may lead to the formation of a stable and compressed soliton in the anomalous dispersion regime when two short 'brigth' pulses are injected into the fiber.