Omar Bashir Adam Yousif2018-10-012018-10-012011-03http://hdl.handle.net/123456789/12948Abstract This dissertation contains six chapters whereby, each chapter involve several sections, chapter one introduces overview about thesis, chapter two contains theoretical background. Chapter three displays the experiments and their executing methods, and the equipments and devices that are used. Chapter four displays graphs for the results. Chapter five discusses and analysis these results. Chapter six introduces conclusion, summary, problems, contributions, and the future vision for this study. This study is aimed to transmit data from transmitter to receiver through air by using laser beam as carrier wave. The laser propagation through a turbulent medium, is facing several challenges are represented in, the absorption , the scattering, the wandering, and the fluctuations in sending of signal. The parameters of laser diode have been obtained as follows : peak wavelength 650.11 nm, the wideband is ranged between (332 GHZ — 152GHz ), output power is ranged between (1.2Watt — 1.4 Watt), the quantum efficiency is 37.8% , and its FWHM is 0.0122. In side of LDR, the important parameter is sensitivity that is ranged between (0.24— 0.28). In lab, the atmospheric optical link has been developed as a channel to transmit information with speed 25OMb/s for a distance 2m.The refractive index structure function that describes fluctuation of optical signal is ranged between ((2.2oi1.0s)x1o"° - (2.16i2.1o)x1o"° ) m 1'3 ) in equatorial line. While the refractive index structure function that describes atmospheric turbulence in the path of the laser beam is equal to (3.7 X 10'7m'2/3). The total rate of loss of the optical signal that occurred by impact both of heat and the background of light on optical propagation through air, was arrived to 47.4% and 2.14% respectively. The methodology that is followed in this study, rely on designing electronic circuits, as well as to propose the atmospheric optical link. The data were analyzed by using origin 8 software, whereas the emission spectrum of laser diode has been graphed by using Ocean Optic USB 2000 Spectrometer. Through study of laser interaction with turbulence medium, the researcher have formulated a model can used for describing strength of turbulence as afunction in the temperature.enSpace communication systemsDATA TRANSFER THROUGH FREE SPACEDATA TRANSFERThesis