Influence of angle misalignment on detection polarization coupling in white light interferometer

Abstract

A white light interferometer is designed to measure the distributed polarization coupling (DPC) in polarization-maintaining fiber (PMF). By using a Michelson interferometer to compensate the optical path difference induced by the modal birefringence of PMF, both the coupling strength and position of the coupling point can be acquired. The two reflective mirrors on the fixed and scanning arms should be vertical to each other. But in practice, the movable reflective mirror can't be vertically aligned exactly to the fixed mirror, which would lead to angle misalignment. The angle misalignment would induce the variance of the optical path difference (OPD), which would reduce the fringe visibility. Finally, the angle error would lead to a decrease on the signal noise ratio (SNR) and miscalculation of the polarization coupling intensity. The angle misalignment and diameter of the incident light beam both have an effect on the fringe visibility. The simulation results show that the requirement of angle error becomes stricter with the increasing of the light beam diameter. To decrease the angle misalignment, the two plane reflective mirrors should be replaced with the corner cube prisms. A revised coupling strength calculation equation was proposed to minimize the influence of angle misalignment.