To Investigate the performance of an outdoor free space optical communication link

Abstract

newline Due its high data rate, enormous bandwidth and large immunity to interference optical communication has received vital importance filed of telecommunication engineering. In traditional optical system, optical fiber acts as the transmission medium between transmitter and receiver. Optical fibers are delicate and require handling precaution. Also, installation of optical fiber is tedious task. Free space optics is another branch of optical communication in which optical fiber is replaced with wireless medium. Due to is more advantages free space optical communication has gained much importance. In this thesis performance of free space optical communication has been investigated. newlineFree space optical communication can be used for indoor and outdoor communication. For investigation of optical communication channel modeling is required. In this thesis investigations have been carried out for outdoor wireless communication system. Background radiations generated by sun and extended sources, Thermal noise and atmospheric turbulence effect the performance of free space optical communication link. newlineIn this thesis different turbulence models like Kruse Model , Kim s Model, Naboulsi Model, Log-Normal Model and Gamma Gamma Model have been studied and analyzed. From study of different turbulence models it has been concluded that Gamma-Gamma channel model is well suited for investigation of free space optical communication link under week, moderate and strong turbulence conditions. newlineDue to there simplicity in implementation and low cost as compared to digital modulation formats, analog intensity modulation formats are widely used in optical communication system, In this thesis the performance of multilevel modulation format called qurdrature amplitude modulation format has been used. Investigation have been carried out for 16 and 64 sub carrier levels. Also the performance of free space optical link range varying from 1 km to 5 km and different temperature rang varying from -20 °C to 60 °C has been investigated. In single input single output free space optical link the performance is very poor. Spatial diversity techniques can be used to improve the performance of single input single output free space optical link. Multi input multi output diversity schemes can be used to combat fading, reduces temporary blockage due to birds and localized fog etc. In this thesis performance of newline newlinemulti input multi output free space optical system has also been investigated using two transmitter and two receiver antennas. The performance of single input single output and multi input multi output system has also been investigated for optical wavelengths of 850 nm, 1064 nm and 1550 nm. It is hoped that the work presented in this thesis will be helpful for better understanding and design of free space optical communication system. newline