Optical wave breaking in optical fibres with cubic–quintic nonlinearity

Based on the extended nonlinear Schrödinger equation in an optical fibre with cubic–quintic nonlinearity, evolutions of the frequency chirps, shapes and spectra of Gaussian pulses are numerically investigated in the normal dispersion regime of an optical fibre. And the approximate analytical descriptions for the developing chirps are presented by adopting two methods. The distances of wave breaking are correspondingly obtained as well. The results show that, the positive (negative) quintic nonlinearity increases (decreases) the chirp amount and the fine structures and then makes the optical wave-breaking phenomena appear earlier (later).