We describe a novel optical sensor based on the Faraday effect for measuring ac. The sensing element is a piece of material of high Verdet constant placed between polarizers. When the angle between the polarizers differs by 45°, a signal of twice the frequency of the ac is generated—in addition to the usual signal with the same frequency as the current. The quotient of these two signals allows a normalized output to be obtained that is proportional to the amplitude of the current. Experimental results demonstrating the practicality of the procedure are presented.
© 2000 Optical Society of America
(040.2840) Detectors : Heterodyne
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(230.2240) Optical devices : Faraday effect
(280.0280) Remote sensing and sensors : Remote sensing and sensors
José A. Ferrari, César D. Perciante, Alfredo Dubra, Alfredo Arnaud, and Erna M. Frins, "Alternating Current Sensor with Second-Harmonic Detection," Appl. Opt. 39, 4638-4640 (2000)