Study On The Theory Of Supercontinuum Generation In Optical Fibers

With the deep development of the optical communication, medical and study of optics, requirements for the ultra-short pulse optical sources and the continuous-spectrum optical sources grow further. Compared with the disadvantages of the conventional optical sources, which are costly, have large noise and low luminance, the advantages of Supercontinuum (SC) ultra-short pulse optical sources are stable and reliable, simple and cheap. Furthermore, SC source have wide broadened continuous spectrum. Thus, it has broad application prospects and more attention now. Recently, the main research of SC generation is on how to generate SC spectrum in order to achieve the purpose of application, and the key is to investigate the generation theory of SC as the base. Overall, most of the reports of SC generation at home and abroad are about experiments rather than theory of the mechanism.The primary coverage of this dissertation is the study on the mechanism of SC generation in optical fibers, including amending and achieving the theoretical framework, with both theoretical analysis and computer simulation methods. In addition, optimal design of the SC generation system will also be put in this paper and the effect of modulation instability (MI) on SC will be discussed finally.Firstly, a numerical solution of the theoretical model has been formed after the simplification and transformation of the light transport equation according to the solving steps of the Symmetry Split-step Fourier Method.Secondly, effects to SC generation in optical fibers of different parameters are introduced generally, especially the effect of dispersion coefficient is further explained. After a qualitative analysis focused on the SC spectrum broadening behavior changing with different values of the fiber length and the peak pump power, an approach of optimizing the SC generation system has been constituted, with a view to simplify the system and save resources.At last, process of MI in SC generation is theoretically explained. Modulation instability can induce the SC generation in the case of designed control, so that the threshold power can be reduced and the efficiency of the spectrum broadening can be advanced. The computer simulation of the MI effect in SC generation has been shown at the end.