Based On Coherent Detection Of The Electro-optic Effect Inter-satellite Tracking Technology

An optical communication link between satellites will play an important role in future free space communications with its advantages over conventional microwave links in its lighter weight, lower power and smaller size.Acquisition, Tracking and Pointing (ATP) technology is one of the key technologies for free-space laser communication systems. The pointing error of ATP system, which will cause power fading of the optical carrier detected by the receiver, limits the performance of laser communications system. According to that, it's very necessary to carry out research on ATP technology.In the paper, a novel beam orienting mechanism utilizing no CCD or quadrant detectors is presented. High-precision and extreme-sensitivity beam orienting could be achieved by the application of beam nutating and coherent detecting technologies. LiNbO₃ crystals with linear electro-optic effect are utilized to perform the beam nutating function. The resulting periodic change in coherent optical power as the signal beam is scanned circularly contains the direction information of the beam. The direction information is fed back to control fine pointing mirror for inter-satellite tracking.Mathematical and computer simulation model of the entire orienting system is developed. The computer simulation results have shown high beam orienting precision provided low laser phase noises are maintained. An experimental system has been built to demonstrate the feasibility of using this technology for beam orienting.