Fiber optic magnetic sensors

• US 4,368,430 A
• Filed: 08/18/1980
• Issued: 01/11/1983
• Est. Priority Date: 08/18/1980
• Status: Expired due to Term

• Current Assignee: Sanders Associates, INC. (BAE Systems Plc)
• Original Assignee: Sanders Associates, INC. (BAE Systems Plc)
• Inventors: Fuller, Harrison W., Rines, Glen A., Dale, John C.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US06/179,346
• Time in Patent Office: 876 Days
• Field of Search: 324/244, 324/259, 324/260, 250/227
• US Class Current: 324/244.1
• CPC Class Codes: G01R 33/038 using permanent magnets, e.g. balances, torsion devices
• CPC Class Codes: Y10S 505/845 Magnetometer

Abstract

A magnetometer which includes a pair of spaced apart optical fibers at least one of which comprises a cantilevered beam having a dipolar magnet thereon such that fluctuations of the magnetic H field will cause fluctuating mechanical torque on the magnet which will be applied to the cantilevered optical fiber to deflect same and occasion modulation of an optical signal transmitted between the two fibers.

Claims

1. A magnetic sensor, comprising:

a first optical fiber, said first optical fiber being arranged as a cantilevered beam, and including a first dipolar magnet mounted on said cantilevered first optical fiber;

a second optical fiber spaced from said first optical fiber so as to produce a gap between the ends thereof, said second optical fiber being arranged as a cantilevered beam; and

a second dipolar magnet mounted on said cantilevered second optical fiber such that the optical coupling between said optical fibers varies proportionally to fluctuations of a component of the magnetic field substantially orthogonal to the longitudinal axes of said cantilevered beams which causes fluctuating magnetic torque on said magnets.

2. The sensor of claim 1 wherein the ends of said first and second fibers are misaligned to increase the sensitivity of said sensor.

3. The sensor of claims 1 or 2 further including means for applying light to said second optical fiber and means coupled to said first optical fiber to detect the amount of light transmitted from said second optical fiber to said first optical fiber.

4. A magnetic sensor, comprising:

a first optical fiber, said first optical fiber arranged as a cantilevered beam, and including a first dipolar magnet mounted on said cantilevered first optical fiber;

a second optical fiber spaced from said first optical fiber so as to produce a gap between the ends thereof, said second optical fiber being arranged as a cantilevered beam; and

a second dipolar magnet mounted on said cantilevered second optical fiber in polarity opposition to said first dipolar magnet such that the optical coupling between said optical fibers varies proportionally to fluctuations of a spacially varying component of the magnetic field substantially orthogonal to the longitudinal axes of said cantilevered beams which causes fluctuating magnetic torque on said magnets.

5. The sensor of claim 4, further including means for applying light to said second optical fiber and means coupled to said first optical fiber to detect the amount of light transmitted from said second optical fiber to said first optical fiber.

6. The sensor of claim 4 wherein the ends of said first and second optical fibers are misaligned to increase the sensitivity of said sensor.