Research On Diversity Combining Technology Of Mode Diversity Free Space Optical Communication System

Nowadays,the information and communication technology has pushing forward into a great development period.Communication both in wired and wireless microwave and optical fiber has been fully developed.Those achievement makes people ask for better communication network with better performance while boosting civilizations of mankind.The strong desire for better equipment and system performance pushes scientific community and relevant industry to explore on and on.In contrast to this,microwave communication and optical fiber communication are going through their periods of stagnation: Microwave resource has been adequately exploited,and there is jamming problem;Paving equipment of Optical fiber communication system is difficult,route planning also cost a lot.The deficiencies above force communication industry to find a potential communication method,meanwhile,the free space optical communication(FSO)technology fit this demand well.Free space optical communication combine advantages of wireless microwave and optical communication,such as high transmission speed,enormous capacity,flexible network,good security,low power dissipation.Free space optical communication is a potential transmission method.Beam from free space optical system goes through atmosphere,which means compositions of atmosphere influence the beam with scattering and absorption effect,which cause power fading,light flashing,multipath effect,and so on.Effects above affect system performance badly.Mode diversity multiplexing(MDM)is able to restrain those influence,improve system performance and targets.The main work and achievement in the subject are as follows:Firstly,the constituent parts of free space optical communication system is studied,the system is analyzed in a comprehensive and systematic way.Analysis the influence of atmosphere channel,and study in every effect.Study the feasibility of mode diversity multiplexing free space optical communication system,and come up with a kind of conception.Secondly,we study diversity reception combining algorithm,analysisimprovements of different algorithms.Finally,we analysis the second and fourth moment matrix(M2M4)algorithm,use a sixth moment matrix algorithm based on parameters,set up an experimental verification system and conduct an experiment.We study the influences of parameters through trial and error,and compare the new algorithm with M2M4 algorithm in mean square error.