Variations of magnetic field measurement with an extrinsic Fabry-Perot interferometer by double-beam technique

The magnetic field variations were measured by a designed optical fiber magnetic field sensor based on the extrinsic Fabry-Perot interferometric sensor with both single and double beam techniques. Behavior of a giant magnetostrictive material Terfenol-D rod was examined at room temperature, under magnetic field variations and varying applied force. In both techniques, as the force increased, the full width half maximum of the peaks decreased; therefore, a larger number of bright and dark fringes occurred with the magnetic field. The displacements increase from 9.24 +/- 0.03 to 13.20 +/- 0.03 mu m for the single beam for 8.65, 9.75, 11.47 and 13.35 N. For the double beam, the displacements are found to be 3.69 +/- 0.02, 3.69 +/- 0.02, and 4.51 +/- 0.02 mu m for 8.65, 9.75, and 11.47, respectively. While Terfenol-D is under different forces, the orientations of magnetic domains are investigated. In summary, the magnetic field could be measured precisely at both short and long ranges by these techniques. (C) 2019 Elsevier Ltd. All rights reserved.