Optical current sensing element with single medium layers for high voltage applications

The performance of a Faraday current sensing element with single medium layer coatings with potential for use at high voltage is reported, and the principle and the design parameters of the polarization-preserving, totally reflecting, single medium layer are given. The performance of the sensing element is demonstrated, showing a sensitivity of approximately 90% of the theoretically achievable maximum for an ideal case, a ratio error of 0.33% over a 7 h stability period and a 21 dB EMI immunity. Some of the advantages of this design are considered and discussed.