Magnetostrictive Fiber Sensors as Total Field Magnetometers

A novel magnetostrictive thin film fiber sensor is presented which can be utilized in an interferometric architecture. The magnetostrictive fiber sensor utilizes novel fiber and thin film technology to achieve high sensitivity in the sub-nanotesla regime. The base sensor architecture utilizes optical fiber wound in a novel low stress flat coil resembling a record, coated with a thin magnetostrictive film. Two prototype variants were fabricated, incorporating FeCo sputtered films of different thicknesses on 4 μm polyimide jacket single mode fiber. The sensors were incorporated into a fiber optic interferometric measurement apparatus to characterize time-varying magnetic field sensitivity. Device results are presented which demonstrate sensitivity is a function of film thickness. The experimental data exhibited a two-order magnitude sensitivity improvement as the thin film thickness was doubled. Sensitivity projections are made based on film thickness.