Phase Noise Monitor and Reduction by Parametric Saturation Approach in Phase Modulation Systems

Nonlinear phase noise (NLPN) is investigated theoretically and numerically to be mitigated by parametric saturation approach in DPSK systems. The nonlinear propagation equation that incorporates the phase of linear and nonlinear is analyzed with parametric saturation processing (PSP). The NLPN is picked and monitored with the power change factors in the DPSK system. This process can be realized by an optical PSP limiter and a novel apparatus with feedback MZI. The monitor range of phase noise is 0°–90°, which may be reduced to 0°–45° if the monitor factor is about the Stockes wave but not an anti-Stockes wave. It is shown that DPSK signal performance can be improved based on the parametric saturation approach.