Internal rotation of the birefringence axes in polarization-holding fibers

An internal rotation of the birefringence axes has been measured in a variety of polarization-holding fibers. The rotation of the axes causes coupling of the major-field components of the fundamental modes, which limits the polarization-extinction ratio in short lengths of birefringent fibers to -45 dB in some cases. A practical consequence of the rotation of the axes is a reduction of the polarization-holding ability of devices such as fiber couplers that are made with these fibers.