Link budget optimization of free space optical systems in relation to the beam diverging angle

The performance of a Free Space Optical (FSO) communication system is highly dependent on the precise selection and adjustment of its operation parameters. The appropriate determination of the angle of divergence can noticeably compensate the negative impact of deviations of the optical beam from its main direction caused by a variety of deteriorative influences. Mathematical equations for calculating the optimum diverging angle are derived within this work. Regarding the obtained results, the link budget and the link margin of FSO systems are calculated. In addition, the dependence of the optimum divergence on the power and the wavelength of the optical source is investigated. In relation to this, enough figures showing evidently the better reliability of a FSO system in condition of beam wandering as well as other degradative impacts are attached.