A Linear Optical Current Transducer Implemented With a Strip Aluminum Polarization Grating

There are some significant defects in the existing optical current transducers (OCTs), such as optical power dependence, non-linear demodulation with Malus law, linear birefringence, etc. These defects severely hurt the reliability, stability, and accuracy of OCTs in long-term applications. The main idea to become free of these defects is to have a linear sense of the Faraday rotation angle. To this end, the paper presents a linear OCT based on a strip aluminum polarization grating, which directly converts the Faraday rotation angle into a synchronous line movement of a light spot. It then positions the spot to measure the current. It has no optical power dependence, realizes a linear sense of the Faraday rotation angle, reduces the effect of temperature drift, almost eliminates linear birefringence, improves long-term stability, and achieves a 0.2S class accuracy.