We developed a fiber-optic CT for large current monitoring in power systems. We used a FRG fiber sensor coil to suppress CT output degradation caused by linear birefringence, and different optical sources were used to compare their noise characteristics. From the experiments, we obtained output variation less than $pm$0.4(%) when the sensor coil suffered mechanical perturbations, and the ASE source showed -23(㏈) less noise in the output than singlemode laser diode.