Magneto-optic sensor by use of time-division-multiplexed orthogonal linearly polarized light

A magneto-optic sensor is proposed and experimentally demonstrated. The sensing unit is mainly composed of an electro-optic modulator, a Faraday magneto-optic glass, and two polarizers. Different from the conventional magneto-optic sensors, this sensor utilizes a time-division-multiplexed and alternately polarized light carrier whose azimuthal angle is periodically alterable between two orthogonal linear polarization states. In particular, this sensing scheme is suitable for dc magnetic field or current measurement, and the measurement result is free from the influences of light intensity fluctuation and environmental electromagnetic interference, due to the applications of square-wave modulation and lock-in amplification techniques. The dc magnetic field in the range of +/-(0.067 approximately 20) mT has been remotely measured and the nonlinear error is less than 1.0%.