Channel Characterisation for Underwater Optical Wireless Vertical Links

We provide a detailed description of depth-dependent effects that affect the propagation of light in underwater optical wireless communication links. Absorption and scattering properties of water are evaluated for realistic chlorophyll profiles versus depth for all the visible spectrum, with particular attention to the wavelengths corresponding to practically feasible laser sources. Results show which visible wavelength is the less affected by propagation loss in specific water conditions, thus being the most suitable to improve the performance of vertical links in underwater optical wireless communications. The developed model is useful also to optimise the distribution of optical channels in systems based on dense wavelength division multiplexing technology, according to the type of water and the depth reached in the vertical communication link.