High-bandwidth underwater communications

The rapid exchange,of data with underwater sensors and systems is increasingly valuable for oceanography, oil exploration and other investigations of undersea phenomena. This paper reviews the potential, as well as the limitations,of acoustic, radio-frequency electromagnetic fiber-optical and free-space optical techniques for high-bandwidth, undersea communication. In particular, we discuss the environmental and hardware attributes that bound the performance of free-space optical communications in a variety of undersea scenarios. Free-space optical approaches are capable of providing data bandwidths approaching 10(9) bits per second (bps) under suitable environmental conditions, More commonly, 10-100 x 10(6) bps can be achieved over ranges approaching 100 meters. Turbid water and high-ambient light conditions (primarily from downwelling sunlight) pose a serious challenge to performance at moderate and long ranges.