Overview and trend of steady tracking in free-space optical communication links

The tracking is mainly used to maintain the established optical communication links (OCLs) in pointing, acquisition and tracking (PAT) ensuring the reliability of date transmission. The structure of pointing and tracking assembly, implementation methods and performances of beacon detector are reviewed. Analysis results show that reducing beam divergence and emission power, using closed-loop composite axis structure tracking system, removing acquisition beacon, analyzing far-filed characters of bidirectional tracking beam are critical to achieve high reliability of data transmission and long steady tracking in free-space optical communication.