Novel configurations in nonlinear fiber optics: Raman scattering and Bragg gratings.

Abstract

Nonlinear effects, either as the limiting factors or as the enabling tools, are of key importance for the modern high-performance optical networks. This dissertation represents a theoretical study of a number of practical or potentially practical fiber-optic systems involving the third-order nonlinearity of the fiber. The first part of this work considers the lightwave propagation in fiber Bragg gratings characterized by the presence of stimulated Raman scattering. The interplay of grating dispersion, Kerr nonlinearity and Raman amplification in this system is shown to give rise to a set of unique phenomena such as distributed feedback Raman oscillation with possibility of Q-switching, generation of slow-moving gap solitons, termed Raman gap solitons, and grating-enhanced pulse re-timing and amplification. Second part of the thesis considers all-optical signal processing based on Kerr nonlinearity in fibers and Bragg gratings. Efficient implementation of all-optical functionality including on-off pulse switching, wavelength conversion and signal regeneration, is numerically demonstrated. It is shown that the proposed framework of frequency shifting and matched filtering is superior to the well-established phase-shifting interferometric approach in terms of robustness, distortion-free operation, cascadability, power fluctuation and noise suppression, and pulse shaping capabilities. Third part of the thesis is devoted to the multi-pump distributed Raman amplification for the broadband and ultra-broadband wavelength division multiplexed systems. The problem of optimization of pumping configuration for the best gain flatness/bandwidth performance, and the problem of trade-off between noise accumulation and nonlinearity-induced signal degradation in such systems, are effectively solved.