An ultra-high-sensitivity direct detection optical receiver for intersatellite communications

Describes such a receiver developed as part of the ESA SILEX project. The system specified uses direct detection at wavelengths in the 850 nm band. Modulation at data rates from 15 to 120 Mb/s using the QPPM format is specified. The receiver described shows frequency response and signal-to-noise ratio performance enabling a bit error rate of 10^-6 to be achieved at all bit rates at input power levels of less than 120 photons/bit, whilst also satisfying the important requirements on size, mass, power consumption and reliability which are critical for space applications. The receiver consists of a module containing a silicon PAD and a hybrid preamplifier, coupled with a PCB incorporating the APD bias generator and telemetry outputs. After a discussion of the overall design approach, the two sections of the receiver are described separately, before assessment results of the complete unit are presented