Discriminating the role of Raman effects in the propagation of decelerating and accelerating Airy pulses by time–frequency analysis

We present a numerical study of the propagation dynamics of accelerating and decelerating truncated Airy pulses (TAPs) in the anomalous dispersion region of optical fibres, with inclusion of the Raman scattering effects, by analysing their cross-correlation frequency resolved optical gating traces. We identify the differences between the evolution dynamics of a decelerating and accelerating TAP. It is shown that the main lobe of the pulse is capable of shedding solitons, which are delayed due to the Raman effects. For the decelerating pulse, however, the soliton is dragged from the original pulse and never meets the input oscillatory Airy tail due to the deceleration of both the pulse and the soliton. The rest of the decelerating pulse rebuilds a new Airy waveform with a stronger degree of truncation compared with that of the incident pulse. For the accelerating TAP, the soliton collides continuously with the tail of the pulse and thus gains further energy by means of their nonlinear interaction. As a consequence, the remaining pulse cannot develop a new Airy waveform. In addition, under the same conditions, the Raman-induced frequency shift of the accelerating TAP is much larger compared with that of the decelerating one. (paper)