The variations in the optical properties of ocean water lead to interesting problems when considering the feasibility and reliability of underwater optical links. Radio waves do not propagate underwater, however with the proliferation of unmanned autonomous vehicles the need to communicate large amounts of data is quickly increasing. Making physical connections underwater to transfer data is often impractical operationally or technically hard to do. Traditionally most underwater communication systems have been acoustic and relatively low bandwidth. However, the development of high brightness blue/green LED sources, and laser diodes suggest that high speed optical links can be viable for short range applications. Underwater systems also have severe power, and size constraints compared to land or air
based systems. Underwater vehicles also encounter a wide range of optical environments. In shallow water the effects of absorption by organic matter and scattering by inorganic particulates can be severe compared to deep ocean water.