The Pulse Trapping In Birefringent Photonic Crystal Fibers And Its Application In All Optical Switching

Photonic crystal fibers (PCFs), demonstrated in recent years, have some unique characteristics such as endlessly single mode, novel chromatic dispersion and easily achievable high birefringence compared with the conventional fibers. PCFs have exhibited wider application potentials in all-optical communication, and have become a hot research topic in optical communication. This combination of the unique dispersion properties and enhanced nonlinearities has made PCFs a promising medium for nonlinear interaction studies and all optical devices. In this thesis, pulse trapping resulting from different polarized angles in birefringent photonic crystal fibers is investigated and we have investigated the physical mechanism of all optical switching using pulse trapping in birefringent PCFs. The main research results are listed below:Firstly, by numerically solving the coupled nonlinear Schr?dinger equations under different conditions, we were able to present pulse trapping resulting from different polarized angles in birefringent photonic crystal fibers. We find that when the linear polarization of the input pulse matches with the direction of one of the polarization axes, the phenomenon of pulse trapping hasn't been observed. It is found that the phenomenon of pulse trapping occurs when the polarized angle is deviated from 0 degree and 90 degree of the fast axis of the fiber. The signal pulse suffers cross phase modulation by the pump pulse and it is trapped and copropagates with the pump pulse along the fiber. The different polarized angles have different effects on the pulse trapping. A minimum trapping efficiency is obtained when the polarized angle is at 45°. For two complementary polarized angles, higher trapping efficiency can be obtained for smaller angle. As the input power of pulse is increased, the red-shift of the Raman soliton is considerably enhanced, leading to further red-shift of the trapped pulse to satisfy the condition of group velocity matching.Secondly, by simulating the all optical switching, we find only one of the signal pulses in pulses train is trapped by the pump pulse and the wavelength of pump pulse and the trapped pulse is shifted toward longer wavelength side. Since the optical spectra of trapped pulse is distinctly separated from those of the untrapped signal pulses, we can pick off only the trapped pulse from the pulse train. It is interesting to note that although the other pulses are also overlapped with the soliton pulse, they are not trapped except for the trapped pulse.