IMPROVE NOISE REDUCTION AT RECEIVER USING NEW MODULATION TECHNIQUE FOR FREE SPACE OPTICAL COMMUNICATION

Free space optical (FSO) communication is now become a main communication due to the ability of propagation channel to operate up to Terabit per sec (Tbs) and can support high number user. However, FSO vulnerable when experience bad weather condition. In this research proposed new development of transmitter and receiver design in order to reduce the impact of atmospheric attenuation and increase receiver sensitivity. The proposed technique will use the combination balance receiver and subtraction signal at receiver. In this paper, the performance of proposed technique will consider scintillation turbulence effect and using Gamma Gamma Distribution. The analysis performance will compare with conventional amplitude shift keying (ASK) approach. Simulation result will be used to measure the performance and comparison between conventional and new proposed modulation double transmission balance receiver (DTBR) will also be presented. The measurement of result will involve the effect of geometrical loss, data bit rate and distance propagation. Four level of synchronous transport module (STM) which is STM1(155Mbps), STM4(622Mbps), STM16(2.5Gbps) and STM64(10Gbps) will be compare the performance of bit rate. Meanwhile two different distances will test to measure the ability system extend the range transmission. From the result, the DTBR can increase 25% improvement as compare to conventional ASK.