Fiber-Optic Current Sensor Based on FBG and Optimized Magnetostrictive Composite

In this letter, we present a compact, open-loop fiber-optic current sensor (FOCS) based on fiber Bragg gratings (FBG) and magnetostrictive composites of Terfenol-D (TD) optimized for enhanced sensitivity and linearity using small concentrations of this alloy. Using magnetic field concentration techniques and orientation of magnetic domains of the composites, a prototype of the proposed FOCS was built with different doping concentrations of TD (10%, 20%, and 40%) and characterized with currents of 15–700 Arms. The proposed FOCS showed a linear response for currents of up to 450 Arms with a linearity error of ±0.55%, a sensitivity of $201~\mu \text{V}$ /A, and 4.8 degrees of phase shift between output and input signals, which are competitive features compared to previous works, since it employs very small amounts of TD (1.5 g max.). The developed prototype also presented a fast response-time to a current transient and a rise time of 1.5 ms, allowing for the proposed FOCS to be applied not only for current sensing, but also to fault detection and monitoring in transmission and distribution lines.