Performance analysis for optical CPFSK transmission system impaired by self-phase modulation

A detailed theoretical analysis is presented to evaluate the combined influence of self-phase modulation (SPM) and group velocity dispersion (GVD) of an optical fiber on the bit error rate (BER) performance of a direct detection optical CPFSK system. Performance results are evaluated at a bit rate of 10 Gb/s taking into considerations the random phase fluctuations at the receiver output due to GVD and SPM. The power penalty suffered by the system due to the combined influence of GVD and SPM is then determined at a BER of 10.9. The results show that the performance of optical direct detection CPFSK is highly degraded due to SPM at an input power of more than 5 dBm and the penalty is minimum at a modulation index of 0.5.