Research Of Fine Tracking Technology Based On Differential Wavefront Sensing

Space optical communication has advantages of high transmission speed, strong anti-interference ability and high security. But ordinary optical communication can not make full use of the advantages of the large bandwidth, has lower frequency utilization,and lower receiving sensitivity. So coherent optical communication technology has been a hot spot in space optical communication research for the past few years.In this paper, APT system is summarized, the traditional method of fine tracking detection is introduced, and the research of fine tracking technology based on differential wavefeont sensing is proposed for the problem of the weak signal energy at the receiving end, because it is hard to make a precision tracking in coherent optical communication system. The relevant theory of fine tracking technology based on differential wavefeont sensing is explained and the heterodyne efficiency of coherent optical frequency mixing is mathematical modelled. The influence of beam radius, collimating mismatch, and wave area bending are analyzed. And the measures of raising the heterodyne efficiency are proposed respectively. The key technology of fine tracking in coherent optical communication system including phase meter of digital phase-locked loop and the system servo of fine tracking are analyzed and designed. The hardware is selected and designed. The devices of testing system are selected and setted up for testing fine tracking system. The result shows that the tracking precision of the fine tracking technology based on differential wavefeont sensing is 5-10 urad, which can satisfy the design index of the system. The research has a very high reference value for the coherent optical communication system to establish a reliable communication link.