Design of a sensitivity-enhanced optical fiber magnetic field sensor based on magnetostrictive composite

In this paper, a magnetic field sensor with simple fabrication, high sensitivity and wide measurement range is proposed. The sensor consists of fiber Bragg grating, sensitivity enhancement structure (SES), magnetostrictive particles and epoxy resin matrix. Metal tube with length of 5 mm is glued onto both sides of the grating as SES, and the mental tube is covered with grooves. The FBG with mental tubes is coated with the matrix made of magnetostrictive particles and resin. During the curing process of matrix, a uniform magnetic field with 200mT and parallel to the fiber is applied to make the orientation of magnetostrictive particles constant. It also can make particles have uniform spatial distribution. Firstly, by comparing the performances of sensors made of three different resin without mental tube with the sensor made by gluing FBG onto Terfenol-D rod directly, it is found that the sensor with epoxy crystal adhesive has the highest sensitivity reaching 0.58 pm/mT. Secondly the sensor based on epoxy crystal adhesive with SES is evaluated. Compared with the sensor without SES and gluing diretly, the sensitivity increases 5.17 times to 3.58 pm/mT and the measurement expands ranging from 0 mT to 226 mT.