TW200600762A - A superstructure fiber grating pressure and temperature sensor of lateral pressure - Google Patents

Abstract

Previous publications of fiber pressure sensors using a uniform fiber Bragg grating is based on the center-wavelength shift of the grating toward the shorter wavelength side due to the pressure directly to pressurize the fiber. Therefore the slope of the center-wavelength shift to the pressure is negative. Recently, the fiber sensors based on a SFBG have been developed to simultaneously measure multi-parameters for improving the function of a sensor system. The fabrication of a SFBG is generally utilized by exposing UV light going through a periodic low-spatial-frequency amplitude mask and a phase mask into the fiber. Thus a SFG includes the characteristics both of a FBG and a LPG, which can be used for measuring pressure and temperature simultaneously. We propose a high-sensitivity fiber sensor with the function of simultaneously measuring temperature and pressure, which based on a superstructure fiber grating (SFG) encapsulated in a polymer-half-filled metal cylinder with its end bonded to the central of a round plate attached to the surface of polymer. The cylinder has two openings on opposite side of the wall at the polymer part. In this way, the polymer can be pressurized along one radial direction only, and responds an axial force acting on the round plate, producing an axial strain on the SFG. The pressure sensitivity of our proposed sensors is greatly improved for comparing with that of a bare SFG. The scheme of this sensor is the combination of the structure of our previous lateral pressure sensor and the characteristics of a SFG for simultaneously measuring pressure and temperature. This sensor should be applied potentially for the measurement of the pressure and temperature of a boiler, and the underwater depth or the axial strain.