Analysis of the effects of aperture averaging and beam width on a partially coherent Gaussian beam over free-space optical communication links

This chapter has examined the performance of partially coherent FSO communication links from the information theory perspective, taking into account the adverse effects of atmospheric loss, turbulence-induced scintillations and PEs. In particular, a spatially partially coherent Gaussian-beam wave and important link design criteria have been jointly considered, in which the latter consists of the receiver aperture dimension and its resulting aperture averaging effect, transmitter beam width, link range, knowledge of CSI and weather conditions. By using the combined optical slow-fading channel model to describe the optical channel characteristics, a comprehensive analysis of the error performance, average channel capacity and outage probability of the FSO system have been presented. Moreover, the lowest-order Gaussian-beam wave model has been introduced in the proposed study, to characterize the propagation properties of the optical signal through random turbulent medium in an accurate manner; taking into account the diverging and focusing of the PCB, and the scintillation and beam wander effects arising from the atmospheric turbulent eddies. Correspondingly, the proposed study have presented a holistic perspective for optimal planning and design of horizontal FSO links employing spatially partially coherent laser beams.