Volume 18, No. 5, 2021
Free Space Optical Communication System -A Comprehensive Review
Kamal Malik , Kulwant Singh
Abstract
In this paper the complete comprehensive analysis of free space optical communication system has been done. The free space optical communication system is a modernized technology where superficial environment acts as transmission medium between transmitter & receiver and for successful transmission of optical signals both the source and the destination should be in LOS. The outer environment, which acts as a channel, can be any outer space, it can be vacuum or modestly air. The FSO system provides attractive bandwidth enhancement with unlicensed bands optical communication spectrum. The transmission & reception in FSO system is mostly rely on the outer channel i.e. the external environment because the presence of external elements like rain (light, medium, heavy), fog, snow, etc. The reliability of the FSO link is immensely dependent on outer or superficial weather conditions that attenuate the optical signal strength travelling in free space. The strength of optical signals gets weakened with the rising or surging of bad weather conditions. For numerous sources wavelength multiplexers can be used which combines the various wavelength optical signals into single source and similarly at destination wavelength de-multiplexers can be used which separates the combined wavelength optical signals. The other aspects which affects the transmission system may encompass the type of light source with particular wavelength of decided band spectrum, modulation formats, amount of data to be send, type of photodetector used etc. The amount of data to be transmitted on particular wavelength is to be either in Mbps or Gbps. The study essentially focuses on the various weather conditions which acts like an obstacle in the FSO system. The weather conditions and amount of data combined are the main consideration for deciding the travelling distance of optical signals from transmitter to receiver. By optimization the FSO system, it maximizes the distance between source and destination by reducing the Bit Error Rate (BER) in output signal. The final conclusion of FSO system can be checked by Q-Factor i.e. the quality of signals and by analyzing the Eye diagrams using Eye analyzer.
Pages: 76-90
Keywords: Free space optical (FSO), Line of sight (LOS), Quality factor (Q-Factor), Megabits per second (Mbps), Giga bits per second (Gbps).