Demonstration of in-line monitoring and compensation of polarization-dependent loss for multiple channels

We use polarization scrambling at the beginning of the link and monitor down stream the power fluctuation induced by in-line components that exhibit polarization-dependent loss (PDL). Compensation of PDL is realized by minimizing this power fluctuation when a variable PDL element is tuned. We demonstrate in-line monitoring and compensation of PDL for an 800-km optical link with a 2.4-dB average PDL and 14-ps average polarization-mode dispersion. By scrambling the polarization of an ancillary wavelength located at the center of a four-channel 10-Gb/s nonreturn-to-zero wavelength-division-multiplexing system, the 2% power-penalty distribution tail is reduced from 6.5 dB to <2 dB within a 6-nm PDL-compensation bandwidth.