The dissertation thesis deals with a free space optical links, especially is focused directly to the transmission optical beams. The influence of environmental conditions like atmospheric turbulence, buildings movement and vibration is described. As a possibility to reduce these undesirable influences, the generation of the transmission beam by the help of the two-mode optical fiber is proposed. A possibility to drive the shape of the resulting transmission beam by means of the change of power ration of individual modes in fiber is described. The coherence features of the proposed beam are analyzed considering the possibility to reduce the influence of atmospheric turbulence. In the thesis there are introduced beam quality parameters that enable to evaluate the quality of the optical beam for the free space optical link. These parameters give the relationship between the shape of the optical beam and the power balance of the optical link and the statistical evaluation of the optical link.