Simultaneous measurement of strain and temperature using interferometrically interrogated fiber Bragg grating sensors

The potential of different fiber Bragg grating pairs for simultaneous sensi ng of strain and temperature is analyzed. We demonstrate that interferometr ic interrogation of a fiber grating written in bow-tie fiber enables strain and temperature to be simultaneously determined. This is achieved by indep endent measurement of the shift in the wavelengths of the reflected light f rom the grating components along the fast and the slow axes of the hi-bi fi ber. A detailed theoretical analysis is presented that includes the basic s ensing principle, sensor design and demodulation scheme. The performance of the proposed technique in simultaneous measurement of temperature and stra in is experimentally demonstrated and resolutions of +/-2.5 degrees C/root Hz and +/-26 mu epsilon/root Hz are obtained for a fiber with birefringence of B = 5.5 x 10(-4). (C) 2000 Society of Photo-Optical Instrumentation Eng ineers. [S0091-3286(00)00808-4].