Optimal Modulation Technique for MIMO FSO Link

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In recent years, free space optical communication (FSO) has gained amorous importance and become an interesting alternative to radio frequency communication because of its numerous benefits over radio frequency communication. It is efficient, low power, high data rate, unlicensed spectrum, and large bandwidth wireless technology. Despite, these advantages FSO is prone to the atmospheric attenuation, but in order to compensate this problem the MIMO FSO system is considered to be a good solution. This paper analyzes the performance of 4*4 MIMO FSO system using different modulation schemes, NRZ, RZ, and CSRZ. The impact of varying, Link range, attenuation factor and transmits power on the performance of 4*4 MIMO FSO has been observed in terms of Quality factor and eye diagram while keeping the other parameters constant. The results show that the RZ modulation scheme using 4*4 MIMO FSO technique show better performance as compare to NRZ and CSRZ. For low attenuation and small link, RZ is superior to NRZ and CSRZ while for higher attenuation and larger link the performance of RZ and NRZ is equivalent. Overall RZ performs better than NRZ and CSRZ. It is also evident from the results that as the number of transmitter and receiver are increased, the efficiency of the system increases. With MIMO technology the performance of FSO system improves to a larger extent.