Abstract

It has been shown theoretically^[1] and experimentally^[2] that solitons also emerge from pulses whose central frequencies straddle the zero dispersion wavelength of an optical fibre. In the process, due to the nonlinearity, a portion of the input pulse energy is shifted into the region of normal dispersion while the other fraction goes into the anomalous dispersive regime of the fibre. As a consequence, solitary and dispersive waves evolve on propagation. However, only qualitative agreement between theoretical^[1] and experimental^[2] results was obtained. The discrepancies were mainly due to the fact that in the experiment, femtosecond input pulses were utilized, while in the theory,^[1] a few picosecond input pulsewidths were assumed. The predictions of the nonlinear Schrödinger equation are accurate for picosecond pulses but need to be modified for femtosecond input pulses, as several higher-order nonlinear effects become important for such short pulses. The most important among them is intrapulse stimulated Raman scattering (ISRS).^[3]

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