Laser diodes communications for the european data relay system

The use of optical communications for the high data-rate links of the future European Data Relay Satellite System has been receiving growing attention for the past few years. This paper presents a system design based upon GaALAs laser diodes transmitters and direct-detection receivers. A Wavelength Division Multiplexing technique is used to accomodate data-rates up to 500 Mb/s on the return link with moderate antenna diameters. Si CCD matrices are used as acquisition and tracking sensors, and angular error informations are extracted directly from the communication signal, thus avoiding the need for a dedicated tracking beacon. Expected performances are given; The system is shown to be capable of supporting variable user requirements. The architecture of the terminals, including adequate redundancies, is described. Mass estimates are given.