A stabilization method of the Sagnac optical fiber current sensor with twist control

We present for the first time a stabilization method for the Sagnac optical fiber current sensor possessing temperature-dependent birefringences. The stabilization is achieved by simply adjusting an additional twist-induced circular birefringence in the Sagnac loop with an automatic active twist control. A simple equation derived for the Sagnac output agrees well to the experimental results. Employing the proposed method, stability of the Sagnac current sensor was demonstrated within /spl plusmn/1.2% in a three-hour temperature stability test between 33/spl deg/C and 70/spl deg/C.