Key Technologies For Space Optical Communication Link

Compared with microwave communication, optical space communication (OSC) has more superiorities: much greater communication capability, narrow beam, good direction, much greater power density functions, lesser antenna size and whole mass, and high capability of anti-electromagnetic disturbances. Because of its high function-price ratio, under the condition of transmitting same information and same data rate, it is very fit for high data transmission ratio between satellite and satellite, satellite and space shuttle, and so on. So the developed nations pay important attention to OSC research, development and deployment.This paper is not meant to describe technical details, but will try to present the critical issues, the complicated trade-offs and inter-relationships between subsystems, i.e., communication subsystem, APT (acquisition, pointing and tracking) subsystem and satellite interface subsystem, of OSC system. Since OSC systems are very complex engineering systems, much more so than terrestrial fiber optical communication systems, proper design approachs and practical solutions need to be taken carefully for their architectural construct and analysis. Breaking down the complex system into interacting but logically separate subsystems for their conceptual design and analysis is the key to suceess. According to the request of the whole system, we have studied possible schemes for applying long wavelength fiber components in communication subsystem, and a promising solution of APT subsystem based on the electronic-controlled liquid crystal (LC) grating. This paper includes a computer simulation of communication link, an experiment of 1550nm band transceiver, a numerical analysis of an LC grating, and a prototype of APT assembly, and finally, presents research concerning the performance of fiber components exposed in space radiation environments.