Apparatus and method for measuring magnetic fields employing

Abstract

A magneto-optic element is employed to create an optical attenuator, an optical modulator and a magnetic field strength sensor. The magneto-optic element exhibits a multiple domain structure in a state where no magnetic field is applied, wherein magnetization components in adjacent domains of the element along a direction in which a light beam travels are different from one another. The optical attenuator further includes apparatus for applying a magnetic field of variable strength to the magneto-optic element. The optical modulator further includes apparatus for applying a modulated magnetic field to the magneto-optic element. The magnetic field strength sensor operates by placing the magneto-optic element in the vicinity of an object to be measured. A light beam is directed from an input optical fiber onto the magneto-optic element and the element diffracts the light beam. A portion of the light beam exiting the element impinges on a reflector and is received by a second optical fiber. In the optical attenuator, that portion of light is attenuated with respect to the light in the input optical fiber. In the optical modulator, that portion of light is modulated with respect to the light in the input optical fiber. In the magnetic field strength sensor, that portion of light is representative of the magnetic field of the object in the vicinity of the magneto-optic element.