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Terfenol based optical phase modulator and magnetometer
Two new fiber optic magnetostrictive phase modulators and magnetometers using the
highly magnetostrictive rare-earth iron compound TbxDyl-xFe2 are investigated. They
demonstrated to have a high sensitivity, dynamic range, minimum field detectability, and a
better structural suitability than metallic glasses. For the first sensor, the experimental
linear phase shifting coefficient was 1.102 rad/Vp-m with the corresponding phase shift
nonnalized to the magnetic field of 0.306 radiO-m. For the second sensor, the
experimental linear phase shifting coefficient was 0.5 rad/Vp-m with the corresponding
phase shift nonnalized to the magnetic field of 0.136 rad/G-m. A minimum detectable
phase shift of better than 1 Î¼rad was obtained, which corresponds to 2 Î¼G/m for a 4 Hz
bandwidth and 1 Î¼G/â HZ per meter of fiber interaction length. The projected minimum
detectable magnetic field for 30 meters, for the first sensor, is thus seen to be 3pT/â HZ.
The experimental results presented have clearly demonstrated the utility of the Terfenol
based magnetostrictive fiber optic phase modulator and magnetometer.