Analysis of under-water Optical Wireless Communication

Abstract

Underwater absorption, scattering and turbulence processes will introduce attenuation and fading
to light propagation and then degrade the performance of underwater wireless optical communications
(UWOC). As power consumption is an important issue in under- water missions, it is fundamental to
minimize the intensity loss by reducing the beam divergence , data transmission in relatively high turbidity
waters appeals for the use of energy-efficient modulations and powerful channel codes at the physical and
data link layers. The particular difficulty of developing such model resides in the fact that turbulence highly
depends on the operational scenario and also on the water conditions underwater wireless optical
communications (UWOC), pulse modulation technique has been widely used due to the high optical power
efficiency and relatively low system complexity. Compared with the simplest on-off keying (OOK) scheme,
digital pulse interval modulation (DPIM) improves both power efficiency and error performance and
requires no symbol synchronization. Polarization shift keying (Polk) is an another appropriate modulation
scheme which can effectively restrain background noise. A scheme named, polarized DPIM (P-DPIM) and
Po1SK , combining both to further improve the performance, and deriving its bit-error- rate (BER)
expression in additive white Gaussian noise (AWGN) channel. UWOC channel suggest that P-DPIM
scheme can improve both the power efficiency and error performance as well as communication distance
compared with traditional PPM and DPIM schemes.