A Low-Power Optical Communication Modem For Compact Autonomous Underwater Vehicles

The design and implementation of a low-power, optical communication system for compact underwater autonomous vehicles are presented for short-range, high-bandwidth data transmission, with an emphasis on identifying optimal hardware configurations for maximizing transmission distance or link misalignment tolerance. Theoretical power and misalignment models are investigated for a single static, light-emitting diode as transmission source, with optical lenses on both transmitting and receiving ends of the system. The maximum misalignment tolerance, while performing digital data communication, is discussed. It is shown that the trade-off between transmission distance and misalignment tolerance is largely determined by the focus level of the receiver lens, which can be controlled by the position of the receiver photodiode on the optical axis. While defocusing the receiver lens permits a larger misalignment tolerance, the signal strength and effective communication distance are decreased. The transmitter beam width is a limiting factor in finding the maximum misalignment tolerance by defocusing the receiver lens.