Underwater LED-Based Communication Links

The United States Navy and Marine Corps require more robust underwater wireless communication capabilities than current equipment can provide, as a small, but important part of future integrated and scalable sea-based networks. I suggest that a wireless alternative to short-range acoustic and radio frequency RF communication may be found in the visible light spectrum. This research investigates the feasibility of incorporating visible and infrared light-based links into tactical military scenarios in order to increase data rates, reduce risks to personnel and obviate the dependence on tethered communication links during underwater operations. A visible light communication VLC prototype was designed and tested in clear and ocean water using 100-W bluegreen light emitting diodes LED with an array of phototransistors. The prototype achieved communication ranges in seawater of up to 6.2 meters using a data rate of 4.8 Kbps. Near-field underwater communication was also possible at a range of 0.3 meters at a data rate of 9.6 Kbps using a 10-W infrared LED. Employing a phototransistor array enabled more freedom of movement by decreasing alignment requirements between the transmitter and receiver. The results demonstrate a substantive increase in communication range and suggest that an LED-based approach could enable sending messages between submerged mobile nodes in open water.