Characterization of an APD-based OEO receiver architecture with the NRL SDA OCT reference modem

Beyond the development and proliferation of a Low-Earth-Orbit (LEO) constellation based on optical intersatellite links, the Space Development Agency (SDA) intends to explore ground station architectures for use in space-to-ground free space optical communication (FSOC) links. For more demanding SWaP constrained tactical platforms, ground receivers based on free-space coupled low noise, large area Avalanche Photodiodes (APD) provide increased tolerance to atmospheric impacts while also relaxing pointing requirements relative to single-mode and multimode fiber-coupled receivers. When used in tandem with a high-speed Single-Mode Fiber (SMF) output Electrical-to-Optical (EO) converter, this APD-based receiver architecture can more seamlessly integrate with SMF input SDA Optical Communication Terminal (OCT) compatible modems. In this work, we characterize the performance of an APD-based OEO receiver integrated with the U.S. Naval Research Laboratory’s (NRL) SDA OCT reference modem.