Polarimetric and intermodal interference sensitivity to hydrostatic pressure, temperature, and strain of highly birefringent optical fibers.

The sensitivity to hydrostatic pressure, temperature, and strain of elliptical-core, D-shaped, bow-tie highly birefringent fibers is experimentally investigated. Both polarimetric and polarization sensitive LP(01)-LP(11) intermodal interferometric responses are studied. The sensitivities are expressed in terms of the experimental parameters T(x,j) describing a 2pi phase shift in the cosine response. It is found that bow-tie fibers exhibit a linear response to all the studied external perturbations except for the polarimetric response of the fundamental mode to temperature, while elliptical-core and D-shaped fibers are characterized by a nonlinear sensitivity to both temperature and hydrostatic pressure. The application to fiber-optic sensors of each type of fiber is discussed.