The Primary Scheme Of Coherent Optical Space Communication And The Research Of Heterodyne Efficiency

Compared to conventional microwave communication, satellite laser com- munication has some advantages such as bigger communication capacity, lower cost, smaller bulk, better anti-jamming capacity, better secrecy and so on. Recently, people have done a large quantity of research on it. For the scheme with intensity modulation/direct detection can't reach the limitation of detection sensitivity, as a result, it can't make full use of bandwidth of optical carrier wave. So, coherent optical communication would be a potential choice as space laser communication technology developed in the future.At first, this paper introduces the concept of coherent optical space com- munication system and its developing status, it also describes the composing of space optical communication system and proposes a scheme for APT subsystem and communication subsystem; Then, on the base of analyzing principles of coherent receiver, it compares the performance among several coherent optical systems and presents an optical coherent receiver that can achieve tracking; And then, it discusses the meaning of heterodyne efficiency, by analyzing the characteristic of space optical channel, it establishes a model of optical distribution on detector surface, based on the established model, it analyzes heterodyne efficiency when the two optical beams are at either optimal status or unmatched status, and calculated the heterodyne efficiency with matlab; At last, it takes the Rayleigh distribution as satellite's vibration model, then analyzes the coherent receiving loss when there are aiming errors exist both on receiving antenna and transmitting antenna, then calculate the bit error rate in the end.For it is very difficult to achieve optical space communication, in our country, it is only on the phase of theoretic now research, so this paper only did some work on primary scheme, and analyzed some influences in order tooffering some theoretic supports when it transforms to project realization. However, only do a lot of detailed demonstrations and some feasible trial, can this project realization come true.