Abstract
We present a compact in-line fiber interferometric sensor fabricated in a boron doped two-mode highly birefringent microstructured fiber using a CO2 laser. The intermodal interference arises at the fiber output due to coupling between the fundamental and the first order modes occurring at two fiber tapers distant by a few millimeters. The visibility of intermodal interference fringes is modulated by a polarimetric differential signal and varies in response to measurand changes. The proposed interferometer was tested for measurements of the strain and temperature, respectively, in the range of 20-700 degrees C and 0-17 mstrain. The sensitivity coefficients corresponding to fringe displacement and contrast variations are equal respectively for strain -2.51 nm/mstrain and -0.02561/mstrain and for temperature 16.7 pm/degrees C and 5.74 x 10(-5) 1/degrees C. This allows for simultaneous measurements of the two parameters by interrogation of the visibility and the displacement of interference fringes. (C) 2011 Optical Society of America

Abstract
This paper presents an overview of optical fiber sensors based on multimode interference with a focus on refractometric applications. A specific configuration is presented to measure the refractive index of the surrounding liquid based on the Fresnel reflection in the fiber tip, combined with a simple interrogation technique that uses two fiber Bragg gratings as discrete optical sources, with the measurand information encoded in the relative intensity variation of the reflected signals. A resolution of 1.75 x 10(-3) RIU is achieved. (C) 2011 Optical Society of America

Abstract
A new concept to measure rotation angles based on a fiber-optic modal Mach-Zehnder interferometer is demonstrated by using a nonadiabatic taper cascaded with a long-period fiber grating. Information about the magnitude of the rotation angle can be obtained from the measurement of the interference pattern visibility, and under certain conditions it is also possible to obtain the sign of the rotation angle from the induced phase variation in the fiber interferometer. (c) 2006 Optical Society of America.

Abstract
A novel in-fiber modal interferometer is presented that is based on a nonadiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fiber end. It is observed that the returned light from this fiber structure shows a channeled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fiber optic flowmeter sensor is demonstrated. 2007 (c) Optical Society of America.

Abstract
A novel Mach-Zehnder interferometer based on a fiber multimode interference structure combined with a long-period fiber grating (LPG) is proposed. The multimode interference is achieved through the use of a MMF section spliced between two single-mode fibers, with a length adjusted to couple a fraction of light into the cladding modes. A LPG placed after the MMF couples light back into the fiber core, completing the Mach-Zehnder interferometer. This novel configuration was demonstrated as a bending sensor. (c) 2007 Optical Society ofAmerica.

Abstract
A micrometric Fabry-Perot refractometer based on an end-of-fiber polymer tip is proposed. The fiber tip, with a length of 36 mu m, was fabricated by self-guiding photopolymerization. The two-wave interferometric operation was achieved by combining the light waves generated at the interface between the single-mode fiber and the polymer tip, and at the fiber tip end (Fresnel reflection). The Fabry-Perot interferometer is coherence addressed and heterodyne interrogated, resulting into a liquid refractive index resolution of approximate to 7.5 x 10(-4). (C) 2009 Optical Society of America