Real-time first- and second-order PMD characterization using averaged state-of-polarization of filtered signal and polarization scrambling

A real-time estimation technique for first- and second-order polarization-mode dispersion (PMD) is presented. It makes use of the spectrum of telecommunication signals. At the output of the transmission fiber, the signal is tapped and filtered. Three filters are used: a high-pass filter, a low-pass filter, and a narrow-band filter. The averaged states of polarization (SOPs) of the filtered signals are then measured using a polarimeter. We repeat the measurement for several different input SOPs using a polarization scrambler at the input of the fiber. From these measurements, we deduce the first-order PMD and, subsequently, the second-order PMD.