Optical fiber magnetometer

• US 5,038,103 A
• Filed: 04/22/1985
• Issued: 08/06/1991
• Est. Priority Date: 04/22/1985
• Status: Expired due to Fees

• Current Assignee: Navy The United Stated of America As Represented By The Secretary of The
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Finkel, Jack, Scarzello, John F.
• Primary Examiner(s): ISSING, GREGORY C
• Assistant Examiner(s): ISSING, GREGORY C
• Application Number:
  US06/725,709
• Time in Patent Office: 2,297 Days
• Field of Search: 324/244, 324/245, 324/246, 324/247, 324/256, 324/257, 324/96, 324/260, 250/227, 350/377
• US Class Current: 324/244.1
• CPC Class Codes: G01R 33/0322 using the Faraday or Voigt effect

Abstract

An optical fiber magnetometer having omnidirectional capability is disclo herein for measuring a total magnetic field independent of its physical orientation or the direction of the field or fields. A relatively long optical fiber defining a sensing arm for exposure to a magnetic field is wound in the form of a spheroid (like rubber bands on a golf ball or yarn threads on a baseball) to provide optical path lengths of substantially the same total length in every direction through the spheroid winding. The plane of polarization of light transmitted through the optical fiber winding is caused to rotate (Faraday effect) when the fiber or components thereof is exposed parallel to a magnetic field. The extent of plane rotation is determined, inter alia, by the total magnetic field passing through the spheroid winding.

Claims

1. A magnetometer for measuring total components of a magnetic field, comprising:

an optical fiber of considerable length wound upon itself in the form of a spheroid, whereby, in any linear direction through the spheroid winding, the total optical path lengths and components of path lengths which lie parallel to that linear direction are substantially equal;

means introducing plane polarized light into one end of the elongate optical fiber, whereby the plane polarized light in passing through the optical path lengths parallel to a magnetic field is caused to be additively rotated according to the Faraday effect; and

means for sensing the plane rotation at the other end of the optical fiber for measuring the total components making up the magnetic field passing through the spheroid winding.

2. A total field magnetometer comprising:

A source of light;

first means detecting a portion of the light and converting it into an electrical reference signal having amplitude variations according to the source;

means plane polarizing another portion of the source light;

a polarization analyzer;

an elongate optical fiber of considerable length having one end optically connected to the polarized light and its other end optically connected to the polarization analyzer;

said elongate optical fiber having an intermediate portion wound upon itself in the form of a spheroid to define a sensing arm with total optical path lengths and components of optical path lengths substantially equal in every direction through the winding;

whereby upon exposure to a magnetic field Faraday rotation is imparted to the plane of polarized light independent of orientation of the winding;

second means detecting rotated polarized light output from the polarization analyzer and converting it into another electrical signal; and

,

means comparing the electrical reference signal and said another electrical signal for eliminating low frequency light source noise.

3. A method of detecting total components of a magnetic field comprising the steps of:

winding an elongate optical fiber upon itself in the form of a spheroid whereby total optical paths extending in every linear direction through the spheroid are of substantially equal length;

exposing the spheroid winding of optical fiber to magnetic fields;

introducing plane polarized light into one end of the optical fiber whereby said plane in passing through the windings which lie parallel and have components which lie parallel to the magnetic field is rotated by the Faraday effect; and

measuring the total rotation of the plane of polarized light at the other end of the optical fiber for determining the total magnetic fields passing through the spheroid winding.