Design Of Optical Pulse Compression System Based On Self-similarity

With the rapid progress and development in the field of mobile communications,people's urgent demand for information is also getting higher and higher,and obtaining high-quality ultrashort pulses has become a bottleneck in this field.At present,the research on high-quality ultrashort pulses has great potential,and the key research object is self-similarity.Therefore,studying how to obtain high-quality ultrashort pulses has always been a key issue in this field.The self-similarity formation that has been widely studied at present relies on two aspects.The first is the positive dispersion region of the dispersion-decreasing fiber,and the second is the positive dispersion region of the fiber amplifier.Self-similar have good transmission characteristics and will always maintain their self-similar characteristics during transmission,and the light wave will not split during high-power transmission.At the same time,the changes of pulse parameters only depend on the incident energy and fiber parameters,and have linear chirp characteristics.In the formation process of self-similar,distortion and broadening will occur due to the influence of dispersion,nonlinearity and gain.It is in this context that the paper proposes a pulse compression system design based on self-similar.The self-similar subcompression and compensation generated in the fiber amplifier have been studied in depth,aiming to obtain high-quality ultra-short pulses.The paper main research work is summarized as follows:(1)Use the nonlinear Schrodinger equation(NLSE)to model the evolution of the pulse,and the numerical and analytical solutions of the self-simulators are derived.Use Lie Algebra method to solve NLSE in fiber amplifier,and the evolution trend of the self-similarity in the fiber amplifier is obtained.(2)The evolution of self-similar in DDF of different function types is studied.The research shows that in the normal dispersion region of DDF,exponential DDF,Gaussian DDF,hyperbolic DDF,and super-Gaussian DDF can evolve into self-simulators.,And has good chirp characteristics.In the negative dispersion region,only the super-Gaussian DDF has good compression characteristics and can be used for pulse compression.In order to further study the formation of self-similar in fiber amplifiers,we use the Ginsburg-Landau equation to solve the evolution of self-similar.The results show that the pulses in the fiber amplifier evolve in the multi-function type DDF to form high-quality parabolic-like pulses,which can be used for distortion-free signal transmission.(3)Design an optical fiber compression system to achieve ultra-short pulse output.The paper introduces a compression factor to measure the quality of the pulse.At the same time,another concept-self-similarity factor is introduced to judge the evolution region of selfsimilarity.After repeated experiments,it is defined that when the self-similarity factor M?0.005,it means that the evolution of the self-similarity has been completed.The combined dispersion decreasing fiber loop mirror is used as the mode locking device in the fiber amplifier,and the multi-function type DDF is used as the transmission medium of the pulse and the dispersion extension line.This thesis is mainly composed of four chapters.The first chapter mainly describes the research background,current situation,goals and specific content.The second chapter mainly describes the basic theory of pulse transmission in optical fiber.Chapters 3 and 4 are mainly the experimental components of the dissertation.The main research contents are as follows:The first chapter first introduces the parabolic-like pulse and describes its transmission characteristics.Secondly,it elaborates on the main content and research objectives of this thesis.The second chapter is the relatively basic theoretical part.First,establish a pulse transmission model in the optical fiber and derive it theoretically.Secondly,the theoretical derivation of pulse evolution in fiber amplifier and the formation of self-similarity are introduced.The third chapter introduces the transmission characteristics of different function types DDF,and interprets the transmission characteristics of pulse pairs.The Ginsburg-Landau equation is introduced to model the evolution of the self-similarity in the fiber amplifier.Chapter 4 introduces the pulse compression system.We have improved the previous fiber amplifiers and introduced concepts such as self-similarity factor and compression factor to evaluate the evolution and quality of the pulse.