Ultra sensitive vector magnetic field sensor based on Fabry-Perot cavity bonded with Terfenol-D rod

A novel high-sensitivity vector magnetic field (MF) sensor based on two parallel Fabry-Perot interferometers (FPIs) is proposed and experimentally validated. Firstly, a thin-core fiber is interposed into a quartz capillary to form a cantilever beam structure FPI₁. The experiment confirmed that FPI₁ achieved a high strain sensitivity of 52.21 p.m./με. Then, FPI₁ is firmly attached to the magnetostrictive material Terfenol-D, converting the MF action into linear axial strain applied to FPI₁, and the sensitivity of its MF intensity and direction reached 401.1 p.m./mT and −134.3 p.m./°, respectively. Finally, a reference interferometer FPI₂ was matched to FPI₁ to produce the harmonic vernier effect sensor S₁. The MF intensity and direction sensitivity of S₁ reaches −6.453 nm/mT and 2.8499 p.m./°, respectively, which enlarged the MF intensity and direction sensitivity of FPI₁ by 16.2 times and 21.2 times, respectively. In short, the proposed MF sensor can measure both MF strength and direction. This sensor is easy to manufacture, low-cost, structurally robust, highly sensitive, and has a wide measurement range. It is one of the important choices for vector MF sensors in practical applications.