Retroreflective free-space optical communication. System analysis and performance

Free space optical communication shows several interesting features for military applications such as transfer of large data quantities, covert data transfer, low jamming risk and overhearing, small volume and low weight etc. In retroreflective free-space optical communication a passive receiver is used to intensity modulate light and transfer data to a transceiver unit. The transceiver unit can be implemented with a non-mechanical beam steering feature for link establishment, tracking and signal optimisation. The retromodulating receiver can use multiple quantum well modulators to optically modulate the intensity of the light. This report describes a system analysis of a retromodulating free-space optical communication system using MQW modulators for the retroreflecting receiver and non-mechanical beam steering using liquid crystal spatial light modulators. Different system designs and technics are reviewed and discussed. Performance calculations including effects from atmospheric attenuation, turbulence and diffraction have been carried out. Problems related to the atmospheric effects and different designs of the retroreflecting receiver are emphasised.