Design of fiber-optic magnetometer utilizing magnetostriction

A magnetometer for measuring a change in a magnetic field Such as the earth's by detecting the magnetostriction of amorphous metal strips with a fiber-optic interferometer has previously been presented. In spite of its high magnetostriction sensitivity, the demagnetizing field is,real owing to its high permeability. In addition. the mechanical load of bonded optical fibers is suspected to be significant for thin films. Assuming that a high sensitivity can be obtained by laminating magnetostrictive films as well as optical fibers and by maximizing the dither amplitude, the sensor sensitivity has been calculated where the most influential demagnetizing factor is estimated from an experimentally measured permeability. The reduction in the measurable range due to the increased dither amplitude is also taken into account. The sensitivity and measurable range are experimentally confirmed to depend on the number of laminated magnetostrictive films, as theoretically predicted.