Abstract: An optical current transducer for measuring current in a high voltage transmission line includes a temperature compensated light source of nominal predetermined intensity and wavelength, a Faraday rotation device where Faraday rotation impressed on the light exiting the light source is proportional to the intensity of the electrical current to be measured. A hermetic tank encloses the Faraday rotation device to provide protection from the environment. An electronic circuit converts the optical output of the Faraday rotation device to an electrical signal in direct proportion to and in phase with the current to be measured.

Abstract: An improved method and apparatus for measuring a target electric current utilizing a Faraday effect in which an optical medium is magnetically coupled with the target electric current and light is passed through the optical medium at an orientation for which the effects of birefringence on the optical medium can be disregarded in comparison with the Faraday effect, and the light departing from the optical medium is measured and analyzed in a manner permitting the target current to be accurately determined.

Abstract: An electric current detector has a light source for generating light having substantially linear polarization and a predetermined polarization direction, a material substantially transparent to the light, the material having at least one characteristic direction, and the material exhibiting the Faraday effect in response to a magnetic field generated by the electric current. Also the light is launched into the material, and a predetermined angle established between the polarization direction and the characteristic direction, the predetermined angle chosen to permit separation of a rotation of the polarization of the light by the Faraday effect from polarization effects on the light by a birefringence of the material. A value of 22.5.degree. for the magnitude of the predetermined angle permits a separation of the rotation of the polarization due to the Faraday effect from polarization effects due to a birefringence of the material.

Abstract: A light detector measures the intensity of two different light beams, computes a ratio of an AC to a DC component for each light beam, and computes a quotient by dividing a first of the above ratios by a second of the above ratios. A light detector has a first photodetector, means, responsive to the first photodetector, for computing a first ratio of an AC component to a DC component of the intensity of a first light detected by the first photodetector, means for producing a first average value of the first ratio, a second photodetector, means, responsive to the second photodetector, for computing a second ratio of an AC component to a DC component of the intensity of the second light detected by the second photodetector, means for producing a second average value of the second ratio, and means for computing a quotient by dividing the first average value of the first ratio by the second average value of the second ratio.