Performance Study on Closed-Loop Controlled Fiber Optic Current Sensor Based on Grating Light Valve

Benefiting from the key advantages of micro-opto-electro-mechanical system (MOEMS) technology, including low cost, excellent process consistency, high optical efficiency, and fast modulation speed, a novel MOEMS-based fiber optic current sensing scheme using a grating light valve (GLV) is proposed. A fully reciprocal architecture is adopted to effectively suppress the influence of common-mode interferences such as temperature and stress on the transmission optical path. A closed-loop modulation-demodulation algorithm combining square-wave and step-wave signals is designed to enhance the system's sensitivity and dynamic range. A high-resolution all-fiber temperature sensor based on the temperature-birefringence effect of polarization-maintaining fiber is integrated to enable real-time temperature monitoring of the GLV probe and correct temperature-related errors. A prototype with a rated current (Ir) of 1000 A is fabricated, and the system's accuracy, temperature performance, and transient characteristics are tested. The results show that the ratio error fluctuation ranges are –0.49%–0.57% at 1%Ir and 0.02%–0.05% at 100%Ir​, respectively, and the composite error at 40,000 A is 1.105%, meeting the error limit requirements of class 0.2s and 5TPE specified in IEC 60044-8:2002. This study provides a new reference method for the research of passive current transformers.