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Differential optical receiver for free space laser communication with ambient light compensation

Photo detectors are used to detect laser signals to support high-speed data communications for Unmanned Aerial Vehicle (UAV). However, there is one potential problem, which is the unwanted ambient light that causes detector to saturate. This is not a problem at night-time. However, at day time, the sun-light causes a D.C photo current and causes the photo detector to saturate and makes the laser signal undetectable. While optical filters are used to reduce the problem, additional techniques are needed to further reduce this problem. In this paper, we present a differential optical receiver to cancel ambient light and other atmospheric noise. In the proposed technique, two photo diodes are configured as a differential receiver to cancel ambient light. Experimental results are presented to validate the concept.