Optical fiber current sensor based on BGO crystal with enhanced faraday rotation by reflections

An optical fiber current sensor (OCS) based on a BGO crystal with a magnetic field concentrator and enhanced Faraday rotation by critical angle reflections is designed and experimentally demonstrated. The influences of the phase shift caused by reflection, which is the main resource of the deviation between the measured and the real values, are theoretically analyzed and numerically simulated. It is demonstrated that the output is very sensitive to the degree of deviation from the reflection critical angle. The phase shift introduced by the reflections of the aluminium films changes linearly as the variations of magnetic field is also demonstrated. So the distortion of the output response due to aluminium coating can be corrected by multiplying a coefficient. It is demonstrated that an OCS based on BGO crystals with enhanced Faraday rotation could be developed into a practical OCS with a good linearity and a large dynamic range.