Fiber-optic current sensor utilized for DC high current calibration

A fiber-optic current sensor based on the Faraday effect is proposed as a value transfer standard to calibrate the direct high current for the electrowinning industry. The spun high birefringence optical fiber with strong resistance to accumulative bend-birefringence in the case of multi-turns sensing coil is packaged into a sensing element. The closed-loop signal-detecting scheme is utilized to improve the linearity of the sensor over the large dynamic range. The good linearity between the sensor output and current-induced Faraday phase shift is proved experimentally. The sensor achieves accuracy within ±0.1% for the equivalent current between 10 kA and 200 kA.