Influence of residual fiber birefringence and temperature on the high-current performance of an interferometric fiber-optic current sensor

Abstract

A highly accurate reflective interferometric fiber-optic current sensor for alternating and direct currents up to 500 kA is investigated. The magnetic field of the current introduces a differential phase shift between right and left essentially circularly polarized light waves in a fiber coil wound around the conductor. Technology adopted from fiber gyroscopes is used to measure the current-induced phase shift. The sensor achieves accuracy to within ±0.1% over at least two orders of magnitude of current and for temperatures from -40 to 80°C with inherent temperature compensation by means of a non-90°-retarder. The paper analyzes the influence of key parameters on the sensor accuracy as well as linearity as a function of magneto-optic phase shift. Particularly, we consider residual birefringence in the sensing fiber and its effect on the high-current performance of the sensor as well as optimum parameters for the temperature compensation scheme. Applications of the sensor are in high-voltage substations and in the electrolytic production of metals such as aluminum.