Performance analysis of a subcarrier multiplexed free space optical mimo transmission link through atmospheric turbulence

Abstract

Free space optical communications is a line-of-sight (LOS) technology that transmits a modulated beam of visible or infrared light through the atmosphere. Now a days, Free Space Optical (FSO) communication is a very much promising technology for communication. But the main weakness is atmospheric turbulence which causes major transmission impairment for an open air optical communication system. To overcome the effect of atmospheric turbulence, Multiple Input Multiple Output (MIMO) communication system has become a very important topic of research over the past few years, due to its capability to greatly enhance spectral efficiencies. So, free space Multiple Input Multiple Output (MIMO) optical communication system through atmospheric turbulence is studied in this thesis. The main objective of this thesis is to analyze the performance of Free Space optical (FSO) communication through atmospheric channel using QPSK Subcarrier Intensity Modulation. Here the performance analysis for a Subcarrier Multiplexed Intensity modulated OFS link with optical intensity modulation and direct detection considering single transmitter and single photo detector in the presence of atmospheric turbulence is carried out. Then the theoretical analysis is extended to a MIMO optical transmission link in the presence of the atmospheric turbulence effect considering Maximal Ratio Receive Combining (MRRC) technique. The performance of the FSO system is evaluated in the presence of atmospheric turbulence for both SISO and MIMO configurations. In this thesis, the performance results are evaluated and shown in terms of BER for several parameters and it is clearly found that BER performance is significantly improved for a Multiple Input Multiple Output (MIMO) system.