Optical fiber Fabry-Perot interferometric sensor for magnetic field measurement

A fiber-optic sensor based on the extrinsic Fabry-Perot interferometer (EFPI) is demonstrated to measure dc magnetic fields (100-35000 nT). A Metglas (Fe/sub 77.5/B/sub 15/Si/sub 7.5/) wire-based magnetostrictive transducer is used as the reflector in two quadrature-phase-shifted EFPI sensor elements which are used to overcome phase ambiguity in the interferometric sensor. The simple sensor geometry gives both relatively low-vibration sensitivity and better than 99% compensation for thermally induced fluctuations.