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

We report the most detailed long-term measurement of polarization mode dispersion (PMD) made to date. We measured two separate fibers under the same time 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 properties of the PMD-vector, Furthermore, the drift averaged over wavelength is very well (96%) correlated between the two fibers. We finally quantified the temporal drift by computing the autocorrelation function of the PMD-vector analytically, both with respect to wavelength and to drift time. The analytical theory shows good agreement with the measurements.