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

Abstract 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 μm 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 μm 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.