Optical current sensor for DC measurement

A high-accuracy optical current transformer (optical CT) for DC current measurement has been developed. The optical CT uses the Faraday effect of silica optical fiber. To suppress the DC offset drift error caused by electronics instability, we proposed the use of a serrodyne modulation Sagnac interferometer. The optical CT shows good linearity within /spl plusmn/ 0.5%. The temperature drift of the optical CT sensitivity was less than /spl plusmn/ 0.5% (-20/spl deg/C /spl sim/ 60/spl deg/C).