Magnetic field sensing based on magneto-volume variation of magnetic fluids investigated by air-gap Fabry-Pérot fiber interferometers

A compact air-gap Fabry-Pérot fiber interferometer using magnetic fluids as the constituent material is constructed. The proposed structure possesses high sensitivity to magnetic field and is eligible for probing the tiny magnetic-field-induced volume variation of magnetic fluids. The underlying physical mechanisms for the magneto-volume variation are clarified in detail. The shift of the interference spectrum with magnetic field is employed for the magnetic field sensing applications. The highest sensitivity of magnetic field sensing for our experimental structure can reach 117.3 pm/mT when the sensing head is set at 45° azimuthal angle (with respect to the magnetic field direction).