An alternative approach to free space optical communication link

Abstract

In recent years commercial and military interest in free-space optical (FSO) communication has been growing due to advantages of high bandwidths, portability and high security. Despite of the numerous advantages, atmospheric events such as attenuation and scintillation severely affects the link quality. Novel methods of mitigating atmospheric events have been applied. Usage of large aperture lenses and high transmitted power decreases the degradation effects, but increases the overall system cost. Fresnel lenses, as an alternative to the classical optic system for mitigating scintillation effects would be a low-cost solution. As a result of the technological improvements on output power and divergence angles of VCSEL (Vertical Cavity Surface Emitting Laser) high-speed cost effective FSO communication system design became possible. In this thesis commercially available FSO systems are reviewed and an alternative low-cost system relying on Fresnel lens optical unit is theoretically and experimentally investigated. The system has been tested and compared for two-day periods with various configurations under atmospheric effects. The results indicated that the Fresnel lenses perform comparably well in contrast to bulk optic lenses. Thus, the large aperture Fresnel optic unit can be deployed for better performance at the scintillation dominating situation without a penalty at the cost.