A mechanical amplifier based high-finesse fiber-optic Fabry-Perot interferometric sensor for the measurement of static magnetic field

A high-finesse fiber-optic extrinsic Fabry-Perot interferometer (EFPI)-based sensor for the measurement of static magnetic fields is proposed and experimentally demonstrated. The high-finesse EFPI is composed of two aligned fiber ends, each of which has a micro-lens mirror. The high-finesse EFPI is mounted on a specially designed mechanical amplification structure which is driven by a TbDyFe rod. Under the applied bias magnetic field, the TbDyFe rod works in the linear region, and its length changes with the change of the magnetic field strength. The mechanical amplification structure amplifies the elongation of the TbDyFe rod in the magnetic field, thus changing the optical cavity length of the high-finesse fiber-optic EFPI. The magnetic field strength can be obtained by measuring the spectral resonance wavelength. Experimental results show that the wavelength sensitivity with the applied magnetic field is 0.218 nm µT-1, the magnetic field resolution is 4.59 nT, and the magnification of the mechanical amplifier is 5.66 times.