High sensitivity demodulation of a reflective interferometer-based optical current sensor using an optoelectronic oscillator

A novel, to the best of our knowledge, interrogation scheme based on an optoelectronic oscillator (OEO) with high sensitivity and high speed response for a fiber optical current sensor utilizing a reflective interferometer is proposed and experimentally demonstrated. Due to the Faraday effect, a magneto-optic phase shift induced by current variation is generated between two orthogonal light waves. The polarization-dependent properties of the Mach-Zehnder modulator are used to convert the magneto-optic phase shift into the phase difference between the optical carrier and sideband, which is then mapped to the oscillating frequency shift by closing an OEO loop. A high current sensitivity of 152.5 kHz/A with a range of 0-2.5 A is obtained in the experiment.