This dissertation thesis deals with a long range free space optical links for communication over the distance of few tens of kilometers in the atmosphere. The problematic of the beam propagation and atmospheric effects influencing the beam and the quality of the communication protocol are discussed. The measuring link is also designed to study the parameters of the communication link work conditions. The measuring link consists of two heads. The transmitter head is designed to use two optical beams with laser diodes at the wavelength of the atmospheric windows 850 or 1550 nm and the overall power of hundredths of mW. The receiver head includes the Fressnel lens. For the detection of very weak signal, the avalanche photodiode is used. In the end of this work, due to the high power of the transmitting optical beam, the laser safety conditions are also discussed, including the deduced optical transmitters construction recommendations.

The aim of this thesis is to study the methods of a free space optical link design and its application in the communication technologies. The thesis describes possible intrusive influences on the transmitted optical signal, which are the signal noise, atmospheric attenuation and atmospheric turbulences. The thesis is particulary focused on the influence of the atmospheric turbulences and atmospheric attenuation on the optical beam.

This dissertation is focused on the determination of turbulent atmospheric transmission media properties. The concept of new method for turbulent attenuation designation is presented – the method of available power. This method comes from laser beam intensity profile analysis. The next point of this work is relative variance of optical intensity study. On the basis of experimental measurements relative variance of optical intensity is non-uniformly distributed in laser beam intensity profile. This non uniform distribution is subordinated to angular coefficient of intensity profile curve. Due to this information we can determine optimal laser beam shape to minimize influence of turbulent atmosphere.