Performance Analysis of Terrestrial FSO Communication Under Typical Rain-Affected Environment of Bangladesh

Use of optical signal in primitive communication is very historic. The use of fire beacons as a means of signaling dates back to 800 BC. However, after the advent of electronics, unlicensed or free space optical (FSO) communication system came into being during 1960s. This system had limited capacity as well as low reliability. However, they had their uses during the demand of the time. Although FSO channel offers huge bandwidth, the development of high speed FSO system had to wait until the time the high demand of bandwidth and the rapid advancement of electronics had generated a renewed interest on the research activities. However, signal degradation due to environment is inherent and higher for near infra-red band than that with radio and microwave band. Many improvement techniques like spatial diversity, delay diversity and adaptive processing along with several modulation schemes have been introduced to reduce environmental impacts. This paper has dealt with only the modulation scheme. Particularly, we have reviewed analytical expression of FSO communication including channel model in order to analyze on how effectively the modulation scheme can address the environmental issue, particularly the rain effect – a predominant factor in Bangladesh environment. Here we have used Meijer G function based closed form expressions and MATLAB simulation for performance evaluation. This kind of FSO system analysis is rare for Bangladesh environmental condition. Our results confirmed that FSO system degrades heavily from low or moderate to strong rain condition by about 20 dB. Likewise, the strong turbulence degrades the FSO links thereby downgrading the link reliability.