PERFORMANCE LIMITATIONS OF A FREE-SPACE OPTICAL COMMUNICATION SATELLITE NETWORK OWING TO VIBRATIONS - HETERODYNE-DETECTION

Free-space optical communication between satellites in a distributed n etwork can permit high data rates of communication between different p laces on Earth. To establish optical communication between any two sat ellites requires that the line of sight of their optics be aligned dur ing the entire communication time. Because of the large distance betwe en the satellites and the alignment accuracy required, the pointing fr om one satellite to another is complicated because of vibrations of th e pointing system caused by two fundamental stochastic mechanisms: tra cking noise created by the electro-optic tracker and vibrations derive d from mechanical components. Vibration of the transmitter beam in the receiver plane causes a decrease in the received optical power. Vibra tions of the receiver telescope relative to the received beam decrease the heterodyne mixing efficiency. These two factors increase the bit- error rate of a coherent detection network. We derive simple mathemati cal models of the network bit-error rate versus the system parameters and the transmitter and receiver vibration statistics. An example of a practical optical heterodyne free-space satellite optical communicati on network is presented. From this research it is clear that even low- amplitude vibration of the satellite-pointing systems dramatically dec reases network performance. (C) 1998 Optical Society of America.