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.
