The main application for magnetic and electric field fiber optic sensors has been the electric power industry. The ability to dielectrically isolate equipment and personnel from high power provides an attractive feature in terms of safety and, ultimately, cost for fiber optic systems versus those using conventional technology. In terms of performance, the theoretical bandwidth of the physical processes occurring within the optical techniques is much faster than the corresponding conducting devices. Also, effects such as hysteresis and saturation (dynamic range), which are common issues with magnetic materials, are, for all practical purposes, absent from the optical components. The size and weight of these devices are also an advantage over iron-corebased designs. All of these characteristics have inspired the vast amount of research and engineering devoted to the development and commercialization of optical-based products.
Several sensing approaches have been successfully conceived using fiber optics for both magnetic and electric field sensing. For magnetic field sensing (of which current is a special case), the majority of the designs exploit the Faraday effect and are polarization based. Interferometric approaches using metallic glass and other various magnetostrictive coatings on fibers have also been demonstrated in the past. More recently, the Sagnac interferometer configuration has proven to be the architecture that has found the most commercial acceptance. For electric field and voltage sensing, polarization-based schemes have been described using electro-optical materials to utilize the Pockels and Kerr effects. Interferometric phase-modulation techniques for electric field monitoring have centered on piezoelectric fiber coatings.
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