Influence of ghost coupling points on distributed polarization crosstalk measurements in high birefringence fiber and its solution.

Ghost coupling points in distributed polarization crosstalk measurements adopting a white light interferometric method are analyzed under the circumstances of anisotropy perturbation induced polarization crosstalk and principal axis misalignment induced polarization crosstalk in polarization-maintaining fiber. The relationship between the intensities of the ghost coupling points and the real crosstalk points, as well as the relationship between their positions, are theoretically analyzed and proved by experiment. A simple method has been developed to identify the ghost coupling points by using a rotatable half-wave plate to adjust the angle between the principal axis of the analyzer and the exciting mode propagating in the polarization-maintaining fiber. The experimental results have a good agreement with the theoretical results.