Influence of SLD's power attenuation on scale factor of closed-loop fiber optic current transformer

According to the analysis of relations between optical power, center wavelength, sensing fiber Verdet constant, and Fiber Optic Current Transformer (FOCT) scale factor, it was demonstrated that the center wavelength excursion generated by power attenuation of SLD was the prime reason of FOCT scale factor error. In order to compensate the scale factor error caused by power attenuation, DC component of detector output was distilled to modify the digital output of FOCT. In the same situation of optical power attenuation, experimental results show that the scale factor error of FOCT was reduced from 1.53% to 0.45% by introducing the compensation method.