Sharif Digital Repository

In this thesis, we model and analyze coherent optical OFDM systems which are highly concerned as future fiber optic communication. To this end, we first introduce various applications of that in optical communication systems and investigate its probes and cones. In the rest of the thesis, we characterize the mathematical structure of the nonlinear phase noise and discuss the previous methods of compensation of that and propose some new ways of nonlinear phase noise compensation and equalization. And as we discuss each method we also investigate its computational complexity and BER performance. We propose three new phase noise compensation method, considering optical phase conjugation, we... 

The purpose of the thesis is to investigate the phonon localization in disordered media and in the presence of nonlinear effect. As a simple model, we consider a system of spring-coupled masses, where the value of mass in each site fluctuates around a positive mean. Using transfer matrix method, we calculate the frequency dependence of the localization length (in the absence of the nonlinear effect) for diffrent strength of disorder in one dimention. For given localized mode, by turning on the nonliner term, we study whether nonlinearity will enhance localization or extend the localized mode? To study the nonlinear effect, since the transfer matrix method is only applicable for the linear...