[Influence of initial chirp on the evolution of spectra]

The influence of dispersion and nonlinearity on the spectra was analysed. The nonlinear Schrödinger equation was solved numerically in the frequency domain. The effect of the initial chirp on the spectra of different formats was simulated. It was found that the influence of the initial chirp on the spectra changed with different formats. The positive initial chirps make spectra spreading and negative initial chirps have little influence upon spectra for Gauss pulses. For super Gauss pulses, the spectra have some side tails, which cause energy loss, but the initial chirp has very little effect on the spectra. The initial chirps have a great influence on the spectra for soliton pulse, especially for high order soliton, which suggests that initial chirp must be decreased for stable pulse transmission.