Optical current sensor by self-compensating the Faraday effect

We present a new optical current sensor architecture, which is based on a polarimetric configuration and a control system for self-compensation of the Faraday effect taking place at the sensor head. After passing through a bulk Faraday sensor head, the light travels through the free space reaching a Faraday modulator placed some distance away from the conductor carrying the current. The first device acts a current transducer and the second one acts as a magneto-optical element operated in a closed-loop mode to compensate the angle of rotation of the polarization introduced by the sensor head. The control system operates in closed loop feedback through a simple current-driven solenoid, and this way, the optical output from the current sensor is maintained at a constant intensity. Considering that the optical and electrical parameters of the sensor head and the Faraday modulator are known, the electrical current applied to the solenoid can be measured, and thus the current flowing through the conductor can be calculated. Experimental results demonstrate the feasibility of the proposed device to measure remotely the current carried by the conductor.