| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 89 === We propose a theoretical model of nonlinear switching in binary long period fiber gratings (LPFG’s). In contrast to the previous model of nonlinear switching in sinusoidal LPFG’s based on nonlinear coupled-mode theory, this model illustrates how nonlinear phase modulations change the phase-matching condition, and also exhibits the influences of the number of periods on transmission. Based on this binary model, we investigate the dependence of pulse shapes on nonlinear switching performance, and then demonstrate that the complete switching can be achieved by use of an ideal square pulse with a given intensity. We further find out the general conditions for either linear or nonlinear complete switching in LPFG’s. Moreover, by applying the binary model to studying the nonlinear switching performances in quasi-periodic LPFG’s, we predict the existence of nonlinear switching in these LPFG’s as well as the achievement of their complete switching when an ideal square pulse is used.
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