High-sensitivity simultaneous pressure and temperature sensor using a superstructure fiber grating

In this paper, we show that both pressure and temperature can be measured simultaneously by using a high-sensitivity fiber sensor. This sensor has a superstructure fiber grating (SFG) encapsulated in a polymer-half-filled metal cylinder, which has two openings on opposite sides of the wall of the polymer, to sense the pressure. The sensed pressure is transferred into axial extended-strain. The variation of pressures and temperatures will cause the variation of the center-wavelength and reflection of the SFG simultaneously due to the optical response of the SFG composed by the fiber Bragg grating (FBG) as well as long-period grating (LPG). Thus, the sensor can be used for measuring pressure and temperature simultaneously. It has a pressure sensitivity of 3 /spl times/ 10/sup -2/ MPa/sup -1/, better than that using only a bare FBG. Temperature sensitivities in both 0.02 nm per /spl deg/C and 0.16 dBm per /spl deg/C have experimentally been obtained. This fiber sensor can be applied for boiler as well as for the underwater depth measurement.