High sensitivity inter-satellite optical communications using LEDs and single photon receivers

High data rate communication links are difficult to perform with radio frequency technology under the strict size, mass and power (SMaP) constraints of small satellites. Transmitting data using the optical spectrum can permit higher data rates with more power efficient systems. Single photon avalanche diodes (SPADs) provide receivers with exceptional sensitivity levels, while light-emitting diodes (LEDs) bonded to electronic driver chips provide digitally controllable optical transmitters capable of high bandwidth spatial and temporal modulation. Data rates of 100 Mb/s have been demonstrated at a sensitivity of -55.2 dBm, and ray-tracing simulations indicate ranges in excess of 1 km are feasible with simple optical systems. Additionally, the divergent nature of LEDs can provide a level of spatial coverage, relaxing pointing and alignment requirements. The low electrical power requirements and compact, semiconductor nature of these devices may therefore bring high data rate, high sensitivity communications to small satellite platforms.