Highly Sensitive Fiber-Optic Faraday-Effect Magnetic Field Sensor Based on Yttrium Iron Garnet

The principle and performance of a fiber-optic Faraday-effect magnetic-field sensor based on an yttrium iron garnet (YIG) and two flux concentrations are described. A single polarization-maintaining optical fiber links the sensor head to the source and detection system, in which the technique of phase shift cancellation is used to cancel the phase shift that accumulate in the optical fiber. Flux concentrators were exploited to enhance the YIG crystal magneto-optic sensitivity. The sensor system exhibited a noise-equivalent field of 8 pT/root Hz and a 3 dB bandwidth of similar to 10 MHz.