Alternating-current measurement and noninvasive data ring utilizing the Faraday effect in a closed-loop fiber magnetometer

Abstract

A novel fiber-optic polarimetric configuration for a magnetometer utilizing the Faraday effect is described. The system is operated in a closed-loop mode using magneto-optic feedback through a simple current-driven solenoid to maintain the azimuth of the optical output from the polarimeter constant. In this mode of operation scale-factor errors due to changes in the Verdet constant of the fiber are effectively eliminated. The minimum detectable current was less than 1 mA, with linear operation up to several amperes. A multiplexed system was also demonstrated, with potential application as a multiaccess noninvasive data ring.