Long-term measurement of PMD and polarization drift in installed fibers

We report the most detailed long-term measurement of polarization mode disp ersion (PMD) made to date. We measured two separate fibers under the same t ime period, which makes it possible to compare the drift properties of two similar fibers in the same environment, The measured Jones matrices suffers from both random and systematic errors, a generic problem which we discuss in detail and solve. The results confirmed the well-known statistical prop erties of the PMD-vector, Furthermore, the drift averaged over wavelength i s very well (96%) correlated between the two fibers. We finally quantified the temporal drift by computing the autocorrelation function of the PMD-vec tor analytically, both with respect to wavelength and to drift time. The an alytical theory shows good agreement with the measurements.