Measurement of a parameter limiting the analysis of the first-order polarization-mode dispersion effect

A necessary condition to guarantee the existence of the principal state of polarization is experimentally examined. The P parameter, which is defined as the product of the differential group delay and the bandwidth of the principal state of polarization, is measured. The P parameter of long single-mode fibers is assessed. Average P values of 0.26 for dispersion-shifted fiber and 0.45 for conventional single-mode fiber were obtained. Combining these results with published results, one finds that P is not determined solely from the state of the polarization-mode coupling.