Performance Limitations of an Optical Heterodyne CPFSK Transmission System Affected by Polarization Mode Dispersion in a Single Mode Fiber

A theoretical analysis is developed to evaluate the bit error rate (BER) performance degradation of an optical heterodyne CPFSK system caused by signal phase distortion due to polarization mode dispersion (PMD) in a single mode fiber. The average BER performance results are evaluated at a bit rate of 10 Gb/s considering Maxwellian distribution for the differential group delay (DGD). The results show that the performance of optical heterodyne CPFSK direct detection system suffers power penalty of 0.75 dB, 1.95 dB, 4.00 dB and 9.15 dB corresponding to mean DGD of 20 ps, 30 ps, 40 ps and 60 ps respectively at a BER of 10 ^-9 operating at 10 Gb/s. Furthermore, at increased values of the mean DGD there occur BER floors above 10^-9, which can not be lowered by further increasing the signal power. It is noticed that BER floors occur at about 2times10^-8, 10^-5 and 2.5times10^-4 corresponding to mean DGD of 60 ps, 70 ps and 80 ps respectively at 10 Gb/s and modulation index of 0.50. The effect of PMD is found to be more detrimental at higher modulation index