Optical communication with underwater snake robots : Design and implementation of an underwater wireless optical communication system

Eelume AS is a norwegian company that develops autonomous underwater vehicles. Their flagship model is an underwater snake robot that performs inspection, maintenance and repair operations. For the time being, Eelume has been using acoustic communications between their AUV's and the docking station, but it has a big drawback: bandwidth. Eelume is interested in streaming live high-quality video from their AUV's to the docking station, which requires several megabits per second. As underwater radio frequency communications are not possible, wireless optical communications seem to be the best available alternative. The focus of this Thesis is to design an underwater wireless optical communications system that could be implemented on the Eelume AUV, although it is designed as a standalone embedded system that could be integrated into any other platform. Two prototypes were designed and tested through-air: a low-cost system featuring a PIN photodiode that can stream a 1.5 Mbps video signal over 0.5 meters and a high-sensitivity system featuring an avalanche photodiode that can stream a 2.5 Mbps video signal over 10.5 meters. Even if further underwater testing is needed and some inherent limitations in the design like the precise calibration or the ambient light noise effects could be mitigated. The results achieved by this high-sensitivity system demonstrates that a high-bandwidth mid-range underwater wireless optical communication system featuring a blue/green LED array as the light source and an avalanche photodiode as the photodetector is a viable solution for streaming live high-quality video over several meters even in very turbid seawaters