Quasi-reciprocal reflective optical voltage sensor based on Pockels effect with digital closed-loop detection technique

A novel Pockels effect based optical voltage sensor (OVS) consisting of quasi-reciprocal reflective optical circuit is proposed and demonstrated in this paper. The quasi-reciprocal reflective optical circuit is realized so that a digital closed-loop detection technique adopted from fiber gyroscopes can be introduced to obtain the voltage-induced Pockels phase. Due to the digital closed-loop detection scheme, the proposed OVS is insensitive to the fluctuation of the light intensity and the dynamic range is independent of the half-wave voltage of the Pockels crystal compared to the conventional crystal bulk-type with the light intensity based detection scheme. A prototype of the proposed OVS is designed and evaluated. The calculated results of the electric field distribution show that the maximal measured voltage of the sensing element is up to 15 kV. The dc voltage from 0 to 3000 V and 50 Hz ac voltage from 0 to 5000 V are measured with good linearity. The proposed OVS achieves accuracy within ± 1% and ± 0.44% with the measured dc voltage above 800 V and ac voltage above 500 V, respectively. The influences of the alignment error in the sensing element on the measurement accuracy are also theoretically analyzed and experimentally verified.