In this paper, a method and a device are proposed that allow measurement of the polarization mode dispersion (PMD) in a transmission line without data traffic interruption. The PMD vector information is extracted from the optical data signal spectrum. The method is experimentally verified by measuring of first-order PMD.
Lothar ller and Larry Buhl, "Method for PMD Vector Monitoring in Picosecond Pulse Transmission Systems," J. Lightwave Technol. 19, 1125- (2001)