Optical electric-power sensor by use of one bismuth germanate crystal

An optical electric-power sensor is presented that allows active and apparent powers to be measured simultaneously using one block of bismuth germanate (Bi₄Ge₃O₁₂) crystal as sensing element, which exhibits both the Faraday effect and the Pockels effect. It is based on the fact that the polarization-related intensity of the light wave passing through the crystal can be modulated by the product signal of applied electric and magnetic fields. When load current and voltage are simultaneously applied to the sensing crystal, the instantaneous electric power signal can be directly obtained from the intensity-modulated light wave. The simultaneous measurements of active power and apparent power, as well as the direction of power flow, have been carried out in experiments. Measurement uncertainty is theoretically analyzed. The potential applications of the proposed optical electric-power sensor are also discussed.