Development of a magneto-optic current sensor for high, pulsed currents

Abstract

A description is given of a current-measurement system based on the Faraday rotation in a one-turn fiber coil. It is shown that an ultralow birefringence ‘‘spun’’ single-mode fiber is extremely suitable in a magneto-optic current sensor. The properties of this fiber were investigated. Measurements of high, pulsed currents (Imax∼1 MA; f=25 kHz), with good accuracy (1%), and in agreement with a conventional method, are presented. Because of the low birefringence, this good accuracy was also reached in the low-current region (ϑ≤π/4 rad). In order to be able to compute the value of large currents unambiguously from the Faraday rotation, a setup with a beam-splitter prism and a second detector was constructed. Some measurements were carried out with this setup.