A linear optical current transducer based on radial polarization demodulation

A linear optical current transducer (OCT) based on radial polarization demodulation was proposed. A magnetic concentration ring with an air gap was selected as the sensing head, in which two magnetizer plates were used to lead out the magnetic field of air gap, and the straight optical path passed through the air gap by light apertures. The reflecting prism was not needed so that the reflection-induced retardation was eliminated, which helped to improve the stability of the transducer. A radially polarized grating was employed to convert the Faraday rotation angle into the rotation of a circular facula, which was detected by a four-quadrant detector, and then the measured current could be obtained after signal processing. The theoretical analysis and experimental results show that this new OCT has a measurement range of 43 in Faraday rotation angle and the advantage of optical power independent, meeting the national standard of 0.2S accuracy class.