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Comparative Analysis of Different Modulation Techniques in Coherent Optical Communication System

Amrinder Kaur , Sanjeev Dewra

This paper presents the comparison of QAM, DPSK and PSK modulation techniques for coherent optical communication system to achieve better performance. It is found that the signal can be transmitted with QAM modulation technique over a long distance without any degradation in the Q factor and BER. The acceptable value is achieved in terms of Q factor and BER at 60km distance with a bit rate of 10Gbps for different modulation techniques. By increasing the length of fiber, the signal points going to be closer in the constellation diagram. The power of QAM is constant, whereas the DPSK and PSK it exhibits fluctuations with time. The spectrum width of QAM is narrower than other techniques. QAM also provide highest Q factor of 12.11 and lowest BER of 4.66e-034 at 60km distance.