Analyze The Impact Of Focusing Sysytem On Single Mode Fiber Coupling Efficiency

The satellite laser communication has developed quickly in recent years due toall its advantages over microwave communication, such as large transmission capacity,high transmission rate, long transmission distance, strong anti-jamming capability,high communication confidentiality and so on. It is an important condition forwireless optical communication to make full use of the existing mature fiber-opticcommunications, and its development trend for wireless laser communication toconnect with wired communication to form communication network. Coupling spacelight into single mode fibers is one of the key issues in satellite laser communication.The aim of this paper is studying the effect of coupling system on single-mode fibercoupling efficiency, and carrying on the study on the influence of efficiency of GRINlenses for coupling space light into single mode fiber. In this paper, the mainachievements are as follows:First, this paper introduced the purpose and significance of this subject and study,discussed the domestic and foreign research progress in single mode fiber couplingand the technical development. This paper states the theoretical model of couplingspace light into single mode fibers and made the expression of coupling efficiency,which is derived by means of the theory of pattern matching under ideal conditions,and considered the change of single-mode fiber coupling efficiency when optical fiberin transverse and axial displacement in changing optimal coupling parameter. Whenfocusing system coupling parameter is less than the optimal coupling parameters, thesystem of optical fiber systems have good tolerance, and the correctness of thetheoretical analysis is verified by optical simulation.Second, the paper analyzes the change of single mode fiber coupling efficiencyin the condition of random angle jitter and considers the change of single mode fibercoupling efficiency along with the change of lateral migration normalized standarddeviation under the optimal coupling parameter. It also analyzes the change of singlemode fiber coupling efficiency along with lateral migration normalized standarddeviation when coupling parameters changes. When the coupling parameter offocusing system is smaller than the optimal coupling parameter, the optical systemswill have good tolerance to jitter. The paper also analyzes other factors which haveinfluence on single mode fiber coupling efficiency.Finally, the paper introduces the origin and development of GRIN lenses, thedifference of variable refractive index lenses and ordinary lenses, and deduces theimaging principles of GRIN lenses. The imaging features of beams passing throughthe self-focusing lens can be changed by controlling the length and diameter of theGRIN lenses. According to the theoretical analysis of single mode fiber couplingefficiency under GRIN lenses conditions, the experiment of the space light into single mode fiber is carried out. The GRIN lenses have good tolerance to the deviation ofbeam.The research work of this paper has fundamental function to the coupling ofspace light into single mode fiber in satellite laser communication, and providetheoretical and experimental basis for optimal design.