Axis alternation for signal propagation over polarization-maintaining fibers

When a signal is split over both axes of polarization-maintaining fibers (PMFs), alternation of axes is well known to cancel the impact of the differential group delay, e.g., in filtering functions such as modulators based on Kerr effect and a Sagnac loop. This solution seems not of concern if the signal remains on one axis as is the case for polarization-maintained signal transportation. As opposed to the common belief, we show experimentally and numerically that alternating the slow and the fast axes is also important to avoid signal distortions in that case. As a matter of fact, strong distortions of polarized signals are observed when the signals are transported with PMF because of the finite extinction ratio of connectors.