Research on measurement and control system of APT for free space optical communication

Abstract

The measurement and control system of APT (Acquisition Pointing Tracking) which maintained the central line of sight (LOS) between transmitter and receiver is one of the foremost and complicated technologies for free space optical communication. The composition and work flow of measurement and control system of APT hardware system was proposed firstly; a novel method was advanced for the purpose of measuring technical indices of each unit; two techniques of multithreading synchronization and event-driven mode were performed to solve the problem of real-time data processing or reduce the delay time of acquisition. by using the transform matrix to realize the process of the high-speed pointing. The results with real data from field experimentation indicates that coarse pointing error is less than 1 and acquisition time is less than 30 minutes; in the cases of weak atmospheric turbulence, coarse tracking precision is less than 60 mu rad and fine tracking precision is less than 5 mu rad, the accuracy and efficiency of free space optical communication can be improved by this system.