Detection of M-ary optical polarization modulation in a communication channel

The advantages of an M-ary scheme over that of binary is the increase in information transfer rate and the reduction in power requirement per unit information. But this is accompanied by an inherent drawback in the form of system performance degradation as the order M increases. The Probability of error of a symbol, which is a complex function of both signal and noise power and M, increases with increase in M, thus increasing the Bit Error Rate(BER).