Adaptive optics corrections in improving the beam spread in underwater turbulent medium

The popularity of the underwater wireless optical communication has increased recently because optical systems have the advantage of providing transmission at high data rates with low latency. However, UWOC is challenging due to harsh environmental conditions and one of the main effects of in oceanic medium is the turbulence. Turbulence causes increase in the beam spread which reduces the performance of the UWOC. In this thesis, the effectiveness of adaptive optics correction for Gaussian beams in oceanic turbulence is studied. The beam size and beam spread were examined with adaptive optics method. The reductions in beam size and beam spread indicate that the adaptive optics correction is a very effective method for reducing the turbulence-caused signal degradations. When investigating the effect of underwater turbulence, the power spectrum in the oceanic medium is supposed to be isotropic and homogeneous. Using the extended Huygens Fresnel principle, average intensity is found. The beam size and beam spread were observed utilizing Carter's definition. Piston, focus, tilt and astigmatism components of adaptive optics corrections were utilized to find the beam size and the beam spread in turbulent oceanic medium. The reduction in the beam size and beam spread was investigated against the ratio of temperature to salinity contributions to the refractive index spectrum, rate of dissipation of mean squared temperature, rate of dissipation of kinetic energy per unit mass of fluid, inner scale, receiver aperture diameter, link length, source size and the wavelength. This reduction was compared with and without the adaptive optics method. Using the MATLAB program, graphs were presented and calculations were performed. In this thesis, it is aimed to provide the most suitable conditions for beam propagation in underwater turbulent environment and to increase the UWOC performance.