Spectral efficiency and quantum limit of BPSK transmission in a WDM system in presence of multiple interferers

In this paper, the spectral efficiency and quantum limit for transmission of a BPSK signal in a WDM system are computed after analyzing the error probability in the presence of component crosstalk. The analysis of bit error rate (BER) is derived from the non-Gaussian probability density function for finite (N) interferers obtained using a new mathematical formulation employing Maclaurin series expansion of the Nth power of zero-order Bessel function. The model is verified with the experimental data taken from the literature. The effects of number of interfering channels, SNR and data rate on BER are studied. Results show how spectral efficiency and quantum limit deviate from ideal values due to the presence of interferers. The spectral efficiency decreases with the appearance of interferers, thus escalating the transmission cost per bit. From the study of quantum limit, it is seen that the minimum number of photons per bit required for BPSK transmission is to be increased to maintain a fixed BER as the number of interferers increases.