Optical detection of electric current

摘要

The method involves producing two elliptically polarised light signals having respective wavelengths and passing them through a Faraday element to rotate the polarisation based on an electric current. A measurement signal for the current is derived from the polarisation change in the two signals. When the two light signals are produced, they are intensity modulated with a first and second frequency. The polarisation of at least one of the signals is rotated by more than 45 degrees under the influence of a maximum electric current.