Free space optical (FSO) communication is a growing technology to handle high data rate
and it has very large information handling capacity. FSO communication systems are
presented as an available alternative to the fiber optics technology which is capable of full
duplex transmission of data, voice and video in certain applications. Even though light can
be competently inserted into fiber cables to route the light information, there are various
applications where only the free space between the transmitter and receiver is the only
available means to establish a communication link. This free space technique needs only a
clear line- of- sight (LOS) path between the transmitter and the remote receiver [1-4].
Actually, the use of light is a very old technique which was used earlier for signaling
purpose. Around 800 BC, ancients Greeks and Romans were using fire beacons for the
purpose of signaling. For the similar purpose, by 150BC the American Indians were using
smoke signals. During 1790-1794, French naval navigators were using optical telegraph
which was based on a chain of semaphores. The first wireless optical communication was
experimentally tested by Graham Bell. In 1880 Alexander Graham Bell demonstrated the
"photo-phone" communication which was modulated by sunlight. The system was
designed to transmit voice signal over a distance by modulating reflected light from the
sun on a foil diaphragm. In 1960 the invention of efficient optical sources such as laser
came into the existence and the technology of FSO has changed. Television signal was
transmitted upto about 48 km distance by researchers in the MIT Lincolns Laboratory
using GaAs LED source in 1962 [5]. In 1970s, FSO was used in secure military
