Fiber-optic current sensors (FOCS) based on Faraday effect could potentially be exploited in several high voltage applications where the electromagnetic immunity is a mandatory requirement. Nevertheless their actual in-field exploitation has always been limited due to critical issues such as fiber residual birefringence that degrades the current measurement accuracy. To this purpose special low-birefringence fibers and spun fibers featuring minimal residual birefringence have been developed. Yet these solutions do not prevent the birefringence contribution induced by the curvature arising during the realization of the current sensing coil.
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