An Ultra-Sensitive Magnetic Field Sensor Based on Extrinsic Fiber-Optic Fabry–Perot Interferometer and Terfenol-D

We report a fiber-optic magnetic field sensor with ultra-high sensitivity based on a precisely configured extrinsic fiber-optic Fabry–Perot interferometer (EFFPI) and Terfenol-D slab. The EFFPI was simply formed by placing two well-cleaved single-mode fibers with carefully designed spacing and it was bonded to the surface of a Terfenol-D slab by epoxy resin. The experiments demonstrate good linear relationship between the applied magnetic field strength and the wavelength shift up to 560 Oe and the measurement range is only limited by the available bandwidth of the light source. The maximal sensitivity of the magnetic field measured by the proposed sensor is 854.73 pm/Oe through monitoring the shift of wavelength dip of the spectrum reflected from the EFFPI, which is significantly larger than most of the reported results. We also evaluated the repeatability of the proposed sensor and the performance of the proposed sensor working at a direct-current (dc)-biased magnetic field. Results indicated that the proposed fiber-optic magnetic field sensor exhibits good restorable measurement performance up to 140 Oe and a preapplied dc magnetic field can be used to extend the linear measurement dynamic range.