Magneto-optic current sensor using a helical-fiber Fabry-Perot resonator.

The concept of a magneto-optic current sensor that employs a fiber-optic Fabry-Perot resonator shaped into a single-turn helix is presented. The helical shape permits construction of a compact device that has the required polarization properties. Compared with a single-pass sensor, a large increase in sensitivity is obtained as a result of the finesse of the resonator. Experimental results confirm the theory and show that for a finesse of F = 6 the sensitivity is four times larger than for a single-pass sensor.