Method and apparatus for optically measuring a current

An optical current measuring apparatus comprising:

• a conductor for conducting a current under measurement;
• a Faraday effect glass disposed to link perpendicularly to said conductor and having at least two total reflection areas at corners thereof;
• a light source for directing a light to a light input section of said Faraday effect glass;
• a polarizer for linearly polarizing the light from said light source and directing the linearly polarized light to said Faraday effect glass;
• said linearly polarized light being reflected at said total reflection areas of said Faraday effect glass such that said linearly polarized light circulates around said conductor and emits from a light output section of said Faraday effect glass, whereby said current is measured based on a Faraday rotation angle of the light by a magnetic field created by said current flowing in said conductor;
• said Faraday effect glass being planar and having an opening through which said conductor extends;
• each of said total reflection areas at the corners of said Faraday effect glass having two closely arranged reflection planes;
• an analyzer disposed to face said light output section of said Faraday effect glass for splitting the light from said light output section into two light beams;
• a pair of condenser lenses disposed to condense said two light beams from said analyzer;
• a pair of optical fibers disposed to face said condenser lenses;
• a pair of light detectors arranged to receive lights transmitted through said optical fibers;
• and
• an arithmetic unit for calculating said Faraday rotation angle based on outputs from said light detectors.

An optical current measuring apparatus for measuring a current flowing through a conductor by detecting a Faraday rotation angle, said apparatus comprising:

• a Faraday effect glass having an opening through which said conductor is passed thereby to inter-link said Faraday effect glass with a current flow in said conductor, said Faraday effect glass having three total internal reflection portions disposed in a light path, said light path looping around a periphery of said conductor;
• a light source emitting said light into said light path in said Faraday effect glass;
• a polarizer disposed between said light source and said Faraday effect glass for linearly polarizing the light from said light source, said linearly polarized light being passed through said light path for reflection at said total internal reflection portions of said Faraday effect glass and then for exciting from said Faraday effect glass;
• an analyzer for splitting said polarized light excited from said Faraday effect glass into two light beams;
• a pair of optical fibers in which said two light beams converged by said condenser lenses are guided therealong;
• a pair of light detectors for detecting said two light beams guided by said optical fibers;
• and
• means for calculating said Faraday rotation angle on the basis of the detected two light beams so that said current flowing through said conductor is determined according to said Faraday rotation angle,
• wherein each of said total internal reflection portions is formed by adjoining two total internal reflection planes, incident planes of the light at each of said total internal reflection planes being perpendicular to each other and said light being total internally reflected at each of said total internal reflection planes so that said light reflected by said total internal reflection portions is maintained as linearly polarized light.