A novel design of the sensor head for avoiding the influence of the reflection phase shift in optical current transducer

We propose a novel structure of the sensor head for optical current transducer (OCT), which consists of a bulk magneto-optic glass with graded index (GRIN) and a ferromagnetic ring acting as magnetic field concentrator. According to the transmission properties of the light in GRIN medium, under certain conditions the light beam propagates along a periodical curved track inside the sensor head and hence is unable to achieve the medium-air interface. Hence, this sensor head can effectively avoid the system error caused by reflection phase shift in the traditional bulk glass optical current transducer (BGOCT). Moreover, the track equation of the light beam, the effective optical path, and the effective range of the incident angle are analyzed and numerically simulated. The results show that the sensitivity of the proposed sensor head can be further improved by appropriately increasing the incident angle and the refractive index difference as well as coating a polarization-maintaining reflective film on the surface of the magneto-optic glass.