6. Electro-optic and Magneto-optic Sensors

The basics of electro-optic and magneto-optic effects, also named after their discoverers, have been known for more than a century. The Pockels effect and the Kerr effect characterize the optical properties of certain crystals, liquids and gases under the influence of an electric field, whereby the polarization of a light wave propagating in the optical axis of the medium is affected. According to the Faraday effect, a magnetic field also changes the polarization of a passing light wave. For all effects, a rotation of the polarization plane of the light occurs in the medium, which is indicated by a downstream analyzer and photodetector as the corresponding electric or magnetic field strength. The optical processes in the medium take place in the nanosecond range, so that bandwidths from zero to the GHz range can generally be achieved with electro-optic or magneto-optic sensors. The clause discusses the nature and characteristics of various recently developed sensors. In conjunction with fiber optics, there are good prospects for the use of these sensors in the high-voltage area. After calibration of the sensors on site, the voltages or currents that generate the fields can be displayed directly. The technical realization of sensors based on the Pockels or Faraday effect has progressed in the last two decades thanks to the solution of many individual problems, resulting in a variety of electro-optic and magneto-optic transducers in the high-voltage network.