Polarization-mode-dispersion measurements with an all-fiber interferometer

Polarization-mode dispersion (PMD) has only recently become of interest because its effects are relevant only in the gigabits-per-second regime. However, our experience, summarized in Table 1, has taught us that polarization-mode delays in installed cables are often an order of magnitude larger than expected: 10 ps for approximately 100 km instead of the 1 ps extrapolated from measurements on uncabled fibers. This, together with the fact that PMD varies strongly from one fiber to another even within the same tube, suggests strongly that PMD measurements could also provide information about the fiber and cable quality.