Spectral-domain analysis of white light propagation in new sensor configuration comprising birefringent fiber

We analyze theoretically and experimentally spectral interference of a white light in a tandem configuration of a birefringent crystal and a sensing birefringent fiber. We express analytically the spectral interference law taking into account the dispersion of birefringence in the crystal and in the fiber. We reveal that the visibility of spectral interference fringes is highest for the group optical path difference (OPD) in the crystal compensating the group OPD in the fiber. We model two types of spectral interferograms knowing dispersion characteristics of the sensing fiber and using a quartz crystal of the positive or a calcite crystal of the negative birefringence. Sensing capabilities of the configuration are demonstrated by the change of the phase of spectral interference fringes due to the change of fiber length. We perform two experiments with a highly birefringent fiber of a suitable length and a birefringent quartz crystal of two suitable thicknesses. We confirm, in accordance with the theory, that the wavelength-dependent phases of spectral interference fringes vary with the fiber length.