Faraday current sensors and the significance of subtended angles

Abstract

A series of experiments, involving measurements of Faraday rotation for light beams in linear and closed-loop optical current sensors, confirms that the degree of Faraday rotation of the polarization azimuth of a linearly polarized light beam, travelling in the vicinity of a current-carrying wire, is a linear function of the angle subtended at the wire by the beam. The experiments have been used to demonstrate the magnitudes of the errors that occur for different path geometries in a triangular closed-loop bulk-glass current sensor. The results of this work should enable geometrical design criteria for bulk-glass current sensors to be more readily established in future.