Fibre Bragg grating sensor for simultaneous measurement of current and temperature

A fiber optic sensor based on Fiber Bragg Grating (FBG) Fabry-Perot Interferometer (FPI) is designed and experimentally demonstrated for simultaneous measurement of alternating current and temperature, in which a laser with single-frequency is used as the light source. The cavity of the FPI is affixed to magnetostrictive material and the pair of (FBG) as the cavity reflectors is placed freely. The length of the cavity is changed cyclically due to the influence of magnetic field around the current on magnetostrictive material, and the peak reflectivity of the FPI is affected by the temperature because of the thermal expansion and the thermo-optic effect. Theoretical analysis indicate that, the temperature and the current can be simultaneously measured by detecting the peaks and frequences of the signal. The experimental results of measuring the current of a coil and the environmental temperature agree well with the theory. This sensor has a wide application prospect due to its simple manufacture and easy demodulation.