Fiber coupling efficiency of vortex beam in underwater turbulent medium

Underwater optical wireless communication is a encouriging technology for high-bandwidth data transmission in oceanic environments. Nevertheless, the performance of underwater optical wireless communication (UOWC) systems is typically hampered by oceanic turbulence, which causes signal degradation and reduces link reliability. This thesis investigates the potential of vortex beams, a special class of laser beams carrying orbital angular momentum, to enhance the efficiency and robustness of UOWC systems. In turbulent underwater channels, conventional Gaussian beams are vulnerable to beam spreading and scattering. Vortex beams, due to their unique phase structure, offer potential advantages in mitigating turbulenceinduced impairments. Moreover, since its great capacity, resistance to turbulence, and ability to work with sophisticated multiplexing techniques, vortex beams are an essential component of optical communication systems of the future. These benefits are especially helpful in settings like undersea communication, where conventional optical beams encounter several difficulties. This research focuses on analyzing the FCE of vortex beams propagating through underwater turbulent channels. The concept of vortex beam propagation in oceanic turbulence is based on the extended Huygens-Fresnel principle. The analysis considers the effects of key turbulence parameters, including the rate of dissipation of kinetic energy, the rate of dissipation of mean squared temperature, and the temperature-salinity gradient. Numerical simulations are guided in MATLAB to evaluate the FCE under varying environmental conditions and vortex beam parameters. The simulations take into account a variety of source sizes, receiver aperture diameters, wavelengths, and link distances. Additionally, the effect of the vortex beam's topological charge on the coupling efficiency is examined. The results of the simulations reveal that higher topological charges in vortex beams lead to better resistance to turbulence-induced beam spreading. Furthermore, the study quantifies the relationship between the FCE and key environmental parameters, such as temperature and salinity. The design and implementation of UOWC systems that use vortex beams can be optimized with the help of these discoveries. The study highlights the potential of vortex beams to strengthen the performance and accuracy of underwater optical communication links. Finally, this thesis aims to improve the performance of UWOC employing vortex beams and to provide the best conditions for FCE in underwater turbulent environments.