Analysis of effects of rayleigh and Mie scatterings based attenuation occuring in troposphere layer in the performance of satellite laser communication systems

In this thesis, the effects of scattering, which is one of the atmospheric effects, were investigated on system losses in free-space optical communication systems. The scattering attenuation values of the determined atmospheric gases and water molecules are calculated. The communication system between ground and satellite has been designed, then the efficiency of the communication system is analyzed by performing the BER analysis. Selecting the troposphere layer where the most intense attenuating effects are determined, the scattering attenuation caused by three different wavelengths in the near-infrared region by hitting the gas molecule in the troposphere layer is investigated by Rayleigh and Mie analysis. The scattering values for 850 nm, 1064 nm and 1550 nm wavelengths are found as 0,0666 m^(-1), 0,7250 m^(-1) and 39,5545 m^(-1), respectively. It is observed that 850 nm wavelength is the most efficient wavelength in terms of attenuation of gases in the troposphere. Using Taguchi's experimental design method, parameters affecting attenuation are ranked according to their importance after a series of analysis. Thus, parameters, which are low priority, are eliminated and it is determined that visibility and wavelength are the most important factors for efficiency. The scattering efficiencies are analyzed for larger water molecules at 850 nm, 1064 nm, and 1550 nm by using Mie theory. The scattering efficiencies by selecting the particle radii of 0.1 μm, 1 μm, and 10 μm, are observed and it is concluded that the most efficient wavelength for large water molecules is 850 nm. By designing a ground-satellite communication system, the BER values of the system with the attenuation effect created by nitrogen gas are observed as (2,06x10)^(-15), (1,36x10)^(-15) and (2,17x10)^(-11) at 850 nm, 1064 nm and 1550 nm wavelengths, respectively. It has been observed that the designed system has smaller values than (10)^(-9) BER value accepted in the literature. Total SNR values were calculated by adding turbulence loss to the system.