Ultrasensitive Magnetic Field Sensor Based on Fabry–Perot Interferometer and Magnetostrictive Material
Longfeng Deng, Chao Jiang, Jiawei Gao, Chuanju Hu, Li Li, Tingshui Cao, Hong Li, Simei Sun, Huiling Huang
Abstract
An ultrasensitive fiber optic magnetic field sensor based on Fabry–Perot interferometer (FPI1) and magnetostrictive material Terfenol-D is proposed. A low fineness FPI1 made by inserting a tapered two-mode fiber (TMF) into a hollow-core fiber (HCF). Due to the increased effective length of strain, FPI1 is particularly sensitive to axial strain. Then, the magnetostrictive material Terfenol-D is bonded to FPI1. Due to the excellent stretching properties of Terfenol-D under the action of a magnetic field, FPI1 adhered to Terfenol-D also has high sensitivity to the magnetic field. The experiment found that in the large magnetic field range of 9.7–92.4 mT, the magnetic field sensitivity of FPI1 reached 1.67 nm/mT. In order to further improve the sensitivity of FPI1 to magnetic fields, we connected a magnetic field insensitive air cavity FPI2 in parallel with FPI1 to form the Vernier effect, further amplifying the magnetic field sensitivity of FPI1. In the range of 13.08–21.93 mT, the magnetic field sensitivity was amplified to 36.43 nm/mT, which is 21.8 times the sensitivity of a single FPI1, which is currently the highest known magnetic field sensitivity. The sensor structure also has good repeatability and stability and low-temperature crosstalk. It is expected to become one of the best options for highly sensitive magnetic field detection.