Optical fiber magnetic field sensor with thermal and acoustic isolation
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorThomas G. Giallorenzi
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Abstract
An optical fiber sensor for detecting the presence of magnetic fields. Light carrying optical fibers are arranged in the form of a dual path interferometer wherein the separate paths define sensing and reference arms. The sensing arm is associated with magnetostrictive material for defining a sensing element which in the presence of a magnetic field undergoes dimensional changes to stretch the optical fiber to change its optical path length thus causing a detectable phase shift in light passing therethrough when compared with the same light passing through the optical fiber of the reference arm. The sensing element is isolated from thermal and acoustic perturbations thus permitting low frequency magnetic field detection.
Claims18
A magnetic field sensor comprising:
- optical fiber means for carrying light from a laser source;
- magnetostrictive means associated with a length of the optical fiber means for defining a sensing element;
- said magnetostrictive means in the presence of a magnetic field undergoes responsive dimensional changes to stretch the optical fiber for effecting light passing therethrough by causing a phase shift detectable by interferometry;
- means pervious to magnetic field lines isolating the sensing element from thermal and acoustic perturbations thereby permitting low frequency magnetic field detection.
A system for detecting a magnetic field comprising:
- a laser light source and a light detector means spaced therefrom;
- a pair of optical fibers, one defining a sensing arm and the other defining a reference arm, each communicating light from the light source to the detector means;
- magnetostrictive means associated with a length of the optical fiber in the sensing arm defining a sensing element whereby in the presence of a magnetic field the magnetostrictive means undergoes dimensional change to stretch the fiber longitudinally to lengthen its optical path to cause a detectable phase shift in light traveling therethrough compared with light traveling through the reference arm;
- and
- means pervious to ingress of magnetic field lines substantially surrounding the sensing element for isolating it from thermal and acoustic perturbations thereby permitting low frequency magnetic field detection.
Dependencies are inferred from the claim text.