Sensing of magnetic fields using fiber-optic interferometers has been demonstrated recently.1–3 In these devices, a two-arm Mach-Zehnder fiber interferometer is used (Fig. 1). One of the fiber-optic interferometer arms serves as a sensor arm on which some magnetostrictive material is deposited. When exposed to a magnetic field, the magnetostrictive material will stretch the sensor fiber while the reference fiber remains unaffected. As a result, a magnetically induced differential path length change or phase shift is introduced at the output of the interferometer.
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