PMD induced performance deterioration in NOLM switch

Performance deterioration induced by the first- and second-order PMD in the basic NOLM switch unit in the digital optical communication system and analog microwave photonic communication system is studied by using the split-step Fourier method that can solve the coupled nonlinear Schrödinger equation, the three-dimensional Poincare sphere theory and the Jones matrix method. The simulation results show that the switch performance is badly deteriorated by PMD and the impact of the second-order PMD is far more than that of the first-order PMD when NOLM is at a high working speed or a large modulation bandwidth. In the digital optical communication system, the optical eye graphs of pulses and the extinction ratio of NOLM are deteriorated by PMD and it can partially reduce the impact of PMD to use the right code pattern, in which the performance of CRZ code with positive chirp is better than that of RZ code and the performance of RZ code is better than that of NRZ code when they have the same average power. In the analog microwave photonic communication system, PMD induces the descent of the SNR and the side lobe leak of the signal.