Interferometric Fiber-Optic Current Sensor with Phase Conjugate Reflector

Optical fiber current sensors based on Faraday effect have a lot of advantages over conventional current transducers and have been studied extensively. The intrinsic birefringence of the sensing fiber is the main cause which affects the measuring precision, and how to eliminate it is the key research topic. In this paper an interferometric optical fiber current sensor configuration with a conjugate reflector is presented. The linear birefringence of the sensing fiber is compensated by the conjugate reflector and the measuring sensitivity is improved by the non-reciprocal nature of Faraday effect. The theory model of the sensor is established and numerically simulated. The simulation results show that the configuration with a conjugate reflector is more insensitive to linear birefringence than the configuration with an ordinary reflector. The residual linear birefringence of the sensing coil, which can be tolerated in conjugate mirror configuration, is about 6 times than that in ordinary mirror configuration for plusmn0.2% measuring accuracy.