Orthogonal polarization coupling for transverse strain measurement using a polarimetric mirror

An inline fiber-optic polarimetric transverse strain sensor based on the coupling of two orthogonal modes is proposed and experimentally demonstrated. The sensing device comprises a section of polarization-maintaining (PM) fiber containing a fiber Bragg grating (FBG). Two resonant wavelengths corresponding to two orthogonal modes are reflected by the FBG along the fast- and slow-axes of the PM fiber. The transverse strain induced on a short PM fiber region effectively modulates the coupling of orthogonally polarized modes, resulting in the intensities redistribution of resonant wavelengths without producing a wavelength shift. Orientation and sensitivity of the transverse strain are unambiguously determined using this compact PM-FBG-based configuration.