Characterization of fiber wave retarders for interferometric fiber-optic current sensors

Fiber-optic wave retarders made from a short section of polarization-maintaining (pm) fiber are crucial components of interferometric fiber-optic current sensors for high-voltage substations. Another potential application of such retarders is in chiral spectroscopy, e. g. for the detection of specific molecules. In a fiber optic current sensor, as considered here, the magnetic field of the current introduces a differential optical phase shift between left and right circularly polarized light waves during their round trip through a fiber coil that encloses the current conductor (Faraday-effect). Closed-loop fiber gyroscope technology is used to measure the current-induced optical phase shift.