Simultaneous Measurement of Temperature and Strain Using Spheroidal-Cavity-Overlapped FBG

We demonstrated a fiber-optic sensor using spheroidal-cavity-overlapped fiber Bragg grating (FBG) for simultaneous temperature and strain sensing. The spheroidal cavity is fabricated through splicing two sections of the photon-sensitive fiber together and located in the center of the FBG to act as a Fabry-Pérot interferometer (FPI). Experimental results demonstrate that the temperature sensitivity of the FPI part of the sensor is 0.67 pm/°C at the range of -70 °C-20 °C, and its strain sensitivity is 3.76 pm/με at the range of 0-500 με, while those of the FBG part are 8.40 pm/°C and 1.40 pm/με, respectively. The sensitivity difference ensures good simultaneous measurement performance.