Experimental Evaluation of the Birefringence Effect on Faraday-Based Fiber-Optic Current Sensors

The results of an experimental investigation of the impact of the bending-induced linear birefringence on a fiber-optic current sensor are presented. A polarimetric configuration is used for measuring a 50-Hz ac current, exploiting the Faraday effect in a coil of standard optical fiber. Different values of diameter and number of turns of the coil are considered, evaluating the loss of sensitivity due to the birefringence as reduction of an effective value of the Verdet constant. It will be experimentally demonstrated that for a coil with a diameter sufficiently large, i.e., equal or larger than 14 cm, the effect of the linear birefringence plays only a marginal role and it can be neglected.