Remote Fiber Optic AC Magnetometer

Fiber optic AC magnetic field sensors have been reported utilizing the Faraday effect [1], the magnetostrictive effect [2] and the Lorentz force effect [3]. In general, these sensors have exhibited either large bandwidth and low resolution or medium-to-high resolution but with strong in-band variations in the frequency response. In some cases active elements were required in the transducer either for magnetic biasing or for interferometer stabilization. In this paper we describe a magnetostrictive sensor for the measurement of AC magnetic fields. The transducer is totally passive in nature, shows flat (± 3 dB) response over the frequency range 1 kHz - 45 kHz, and exhibits resolution of 1.8 × 10-7 G/√Hz over the entire frequency range.