PRINCIPLES AND DESIGN OF BIDIRECTIONAL OPTICAL ISL USING GAALAS LASER AT LAMBDA = O.85 MU-M AND DIRECT DETECTION PPM

This paper gives a general introduction to bidirectional optical intersatellite links. The design, principles and link budget are presented, and the four subsystems - transmitter, receiver, optical channel and acquisition/tracking system - are described. GaAlAs semiconductor laser and a silicon avalanche photodiode are used as the optical transmitter and receiver. Pulse polarization position modulation is used to obtain a higher sensitivity. The acquisition/tracking signal is extracted from the top-modulation data stream. The effect of background noise is analyzed, and direct detection and heterodyne detection are compared.