CD-insensitive PMD monitoring using electronic domain orthogonal coherent processing for OOK optical link at 40 Gbits/s

We theoretically and experimentally demonstrated the polarization mode dispersion (PMD) monitoring of 40 Gbit/s NRZ and RZ links by using a electronic domain orthogonal coherent technique; this method can detect the spectrum phase difference between the fast axes and slow axes. In my experiments, the radio frequency (RF) of local oscillator (LO) is set to 5 GHz, the monitoring range is around 0–100  ps, the maximum fluctuation range of measured phase difference is better than 0.05 rad for 40 Gbit/s NRZ link. This method is independent on data rate for intensity modulation direct detection (IM/DD) links.