Polarization Mode Dispersion monitoring for phase-modulated optical signals utilizing parallel cross-phase modulation in a highly nonlinear fiber

We propose a first-order Polarization Mode Dispersion (PMD) monitoring technique for phase-modulated optical signals utilizing the cross-phase modulation (XPM) effect between the input signal and the inserted continuous-wave probe in parallel connection. Because of accumulation of PMD, the XPM effect in nonlinear fiber leads to variation of pump phase. This can cause spectrum broadening resulting in variation of pump power. The technique can suppress the influence of PMD in one branch of the two signals in parallel connection then use the difference of the two pump power at the same band to monitor PMD. The simulation shows that the technique can monitor PMD of 40-Gb/s non-return-To-zero differential quadrature phase-shift keying (NRZ-DQPSK) from 0-30ps.The dynamic range over 3dB can be used in accurate monitoring compared to existing methods. The applicability of this monitoring technique to higher bit-rate phase-modulated signals, such as 80-Gb/s NRZ-DQPSK, is also investigated via simulation.