Theoretical Investigation On Some Optical Pulse Compression Problems

The generation of ultra-short optical pulse with high repetition rate is one of the key techniques in the high-speed optical time-division multiplexing (OTDM) system. The higher the transmission speed is, the shorter the optical pulse width is expected to be. Nowadays, the optical pulse used in the OTDM system is often generated by the gain-switched distributed-feedback (GS-DFB) semiconductor laser, which has a large pulse width and negative chirp. Therefore, to satisfy the demand of the OTDM system, the technique of optical pulse compression must be applied. Based on the previous works, many schemes achieved easily have been proposed and investigated in this paper, through which the pulse can be compressed effectively.A novel designed model of the optical pulse compression, which is based on the dispersion-compensation fiber (DCF), the dispersion-shift fiber (DSF) and Erbium-doped nonlinear amplifying fiber loop mirror (ED-NALM) has been presented. The numerical simulations show, based on this scheme, the pulse generated from GS-DFB semiconductor laser can be compressed effectively, and the pulse energy is enlarged extremely. This scheme can be used to compress and amplify the pico-second pulses with negative chirp.In the process of the pulse compressed by the cross-phase modulation, when the pump pulse is a pulse pair, the pulse walk-off effect will generate an obvious destructive effect. Based on this reason, a new method, asymmetrical pulse pair method, is proposed to suppress the walk-off effect. Compared with the results obtained by the method of asynchronous coupling, the better pulse compression quality can be achieved by the method of asymmetrical pulse pair.