Fiber optics device for measuring the intensity of an electric current utilizing the Faraday effect

A fiber optics device for measuring the intensity of an electric current along a current path using the Faraday effect, said device including an optical fiber having first and second ends which fiber surrounds the current path in a number of windings to mark an optical path which is exposed to the magnetic field of the current, wherein when a light flux generated by a light source and having a defined polarization state is fed into the fiber at its first end, a current-dependent alteration of this polarization state is produced along this optical path because of the Faraday effect, and wherein said device further includes a polarization measurement unit by which the polarization state of the light can be detected after it has traversed the optical path subjected to the magnetic field, and by which a polarization measurement signal characteristic of the current intensity can be generated, wherein the device further comprises an adaptive reflection unit located, substantially, at the second end of the optical fiber which reflection unit comprises a partially transparent mirror reflecting a first part of the light emerging from the second end back into the fiber, and transmitting a second part of the light emerging from the second fiber end to an analyzer unit which detects the polarization state of said second part of the light which is transmitted by the mirror and generates an output signal which is characteristic of this polarization state, and wherein the reflection unit further comprises a polarization servo means which receives the output signal of the analyzer unit as a control signal and which acts on the optical fiber to adjust the polarization state of the light emerging from the second end of the fiber to maintain the polarization state of the light transmitted and reflected by the mirror at a linear polarization state.