Temperature compensation of optical fiber Bragg grating pressure sensor

A temperature-insensitive sensing scheme for pressure measurement is presented. In the sensing scheme, a single optical fiber Bragg grating (FBG) is axially strained by its surrounding pressure, and is thermally compensated by a bimaterial effect. The FBG is kept tight (i.e., in a positive strain) initially in the sensing structure. When the surrounding temperature increases, a negative strain (to loosen the FBG) is incurred on the FBG and produces a blue shift of the Bragg wavelength. Temperature compensation is, thus, made by balancing such blue shift and the inherent thermally induced red shift of the FBG. Experimental results show a pressure sensitivity of the fractional change in the Bragg wavelength of 1.8/spl times/10/sup -2/ (MPa)/sup -1/, and demonstrate quite a low response to the temperature varying from 10/spl deg/C to 60/spl deg/C.