EFPI-FBG hybrid sensor for simultaneous measurement of high temperature and large strain

We report an extrinsic Fabry–Perot interferometer-fiber Bragg grating(EFPI-FBG) hybrid sensor in this letter. The interferometric cavity of the proposed hybrid sensor is composed of a glass capillary tube, a section of single-mode fiber, and a section of single-mode metal fiber with one FBG. The FBG processed by high-temperature annealing is used to measure temperature, whereas the fiber EFPI is adopted for strain measurement. One of the two aligned fibers is free along the axial direction, which is different from the traditional structure that both the fibers are fixed to glass capillary tube. Experimental results show that the sensor can measure high temperature and large strain simultaneously. The measuring range of temperature and strain for the hybrid sensor is up to 500 °C and 10,000 με, respectively. Effective temperature compensation of the hybrid sensor is realized, too.