English title

The idea of using free space optical communications in seas has developed extensively to investigate the natural water for scientific and financial interests. Underwater wireless optical communications (UWOC) is a new technology using optical carriers to transmit information in water. Usage of Optical carriers increases the rate and bandwidth of data transmission extremely compared to the previously method of acoustic communications. However, it is limited to short distances due to high water absorption in optical frequencies. In addition, other factors including multiple scattering and turbulence degrade the performance of UWOC system. The unique features of water cause the free space optical communications channel models not to be suitable for UWOC channels. To have acceptable data rate and bit error rate in UWOC, it is essential to investigate thoroughly the effect of key factors on light propagation in channel models. To achieve this goal, this paper is investigating the existing UWOC channel models in literature. In these models, the effects of absorption, scattering and turbulence have been considered. Studying the channel modelling techniques, is a great help for proposing a comprehensive and extensive channel model.