Differential Retro-Detection for Remote Sensing Applications

A retro-detection technique is introduced for simultaneous optical retroreflection, detection, and control in bidirectional sensor links. An architecture with three orthogonal photodiodes (PDs) is used to retroreflect incident light and sample the incident optical signals. Such a system establishes a two-way (bidirectional) optical link. Moreover, the three photocurrent signals can be used in differential combinations for active control and optimization of the alignment. The theory and methodology for the optical retroreflection, detection, and control characteristics are presented, and the technique is verified experimentally with a silicon PD retro-detection prototype. The active remote sensing capabilities of the retrodetector are found to be successful.