Error analysis and experiment for reflective sagnac interferometer-type fiberoptic current sensor

A reflective Sagnac interferometer-type fiber-optic current sensor (RS-FOCS) is presented with Y-branch integrated-optics phase modulator and polarization beam splitter. The digital closed-loop fiber gyroscope technology is employed for signal detection and processing. The variation of linear birefringence and Verdet constant of sensing fiber and phase retardation of quarter-wave retarder with temperature is indicated as the primary scale factor error source. The effect of linear birefringence was suppressed by winding the sensing fiber spirally, and the ratio error caused by the temperature dependence of the Verdet constant is reduced by elliptical-core fiber quarter-wave retarder. The performance of RS-FOCS is tested, and the results show that: the error is less 0.1% for high current whereas more than 1% for low current; the maximal variation of scale factor is 0.066% in a month; the scale factor error is less than 0.2% at -40°C~60°C.