INTERFEROMETRIC VOLTAGE SENSOR WITH ERROR COMPENSATION

In order to measure a voltage, an electro-optic element (5) is placed in an electrical field generated by the voltage, and light is passed from a light source (9) through a Faraday rotator (4) and the electro-optic element (5) onto a reflector (6) and from there back through the electro-optic element (5) and the Faraday rotator (4), thereby generating a voltage-dependent phase shift between two polarizations of the light. The interference contrast as well as a principal value of the total phase shift between said polarizations are measured and converted to a complex value having an absolute value equal to the contrast and a phase equal to the principal value. This complex value is offset and scaled using calibration values in order to calculate a compensated complex value. The voltage is derived from the compensated complex value.