The Evolutions Of Picosecond Bright Solitons And Dark Solitons In The Presence Of Raman Gain And Self-Steepening Effect

Solitons are nonlinear waves present in diverse physical systems including plasmas, liquid crystal and optical fibers. In optical fiber, solitons can keep its initial pulse shape in the temporal domain and initial spectrum in the frequency domain. It is this characteristic that optical solitons have potential applications in optical communication, and a fully investigation is thus highly demanded from a theoretical point of view. Based on the Wave Equation that the slowly varying amplitude follows, the nonlinear Schrodinger equation (NLSE) including Raman gain effect and Self-steepening (SS) effect are derived in detail. In the case of ignoring fiber loss effect, the linear operator and nonlinear operator specific expression have been given based on fractional Fourier numerical algorithm. Meanwhile, the evolutions of bright soliton and dark soliton are respectively simulated, to provide theoretical basis for soliton communication, the influence of Raman gain and SS effect on propagation characteristics is investigated.The thesis is composed with three parts including preface, main body, and conclusion. In the preface, we introduce the origin and classification of the optical soliton and the main research content of this article. The main body is organized as follows. The first section is the theoretical model, if ultrashort optical solitons propagate along fiber, higher-order nonlinear effects including Raman gain and SS effect will play a vital role. For picosecond soliton pulses, SS and Raman gain may not be ignored. Based on the Wave equation that the optical pulses meet in optical fiber, both high-order nonlinear Schrodinger equation considering the Raman gain and SS effect is derived in detail. Next, to establish the theoretical model, two operators are reduced by using the method of fast split-step Fourier. In Section Ⅱ, the propagation characteristics of picosecond bright soliton along the isotropic fiber with the combined effect between the Raman gain and SS effect are simulated through evolution process by numerical solving NLSE. In Section Ⅲ, the propagation characteristics of picosecond dark soliton along the isotropic fiber with the combined effect between the Raman gain and SS effect are simulated. In the last section, the comprehensive summaries and its application to practical production are list in detail.