Fiber-optic magnetic field sensor using a phase-shifted fiber Bragg grating assisted by a TbDyFe bar

A compact fiber-optic magnetic field sensor based on edge filtering method is proposed and experimentally demonstrated by using low-cost intensity interrogation. A phase-shifted fiber Bragg grating (PS-FBG) with two extremely narrow notches is bonded on a TbDyFe bar by epoxy resin oriented along the longitudinal direction. As the TbDyFe acts as a magnetic field transducer and PS-FBG as a strain sensor, the magnetic field strength distribution of two permanent magnets can be measured by monitoring the reflected intensity variations of the PS-FBG probe. The magnetic field sensing device shows a detection resolution of 0.023 mT and a measured magnetic domain ranging from 2.43 mT to 22.54 mT. The reversibility and orientation-dependence of the proposed sensor are also experimentally investigated.