An optical sensing method of current based on annular graded-index magneto-optical glass

We propose a novel optical element for bulk glass Faraday current sensor to avoid the influences of the reflection phase shift in traditional bulk glass current sensors. An annular graded-index magnetic-optic glass with an opening is designed as the sensing head, in which the inner and outer layers possess gradient indices, while the center layer is uniform. The theoretical analyses show that since the light propagating in the sensing head can not reach the interface between the magnetic glass and air, the reflection phase shift could be avoided essentially, resulting in dramatically enhancement of the sensitivity. The influences of the geometrical parameters on the beam traces and the effective range of the initial angle are numerically simulated. It is revealed that this sensing head with high sensitivity, large effective range of the initial angle and no reflection phase shift can be obtained by choosing proper parameters of the annular magnetic-optic glass.