Magnetic Garnets for Lightning Current Measurements

Magneto-optic phenomena are those in which the optical properties of certain materials are affected by external magnetic fields or the material's own magnetization. One of them is the Faraday effect, which occurs when linearly polarized light propagates through a material exposed to a magnetic field aligned parallel to the direction of propagation of the light. Ferromagnetic iron garnet crystals exhibit a magneto-optic sensitivity that is orders of magnitude higher than those of typical paramagnetic and diamagnetic materials. Based on magnetic garnets, a fiber-optic sensor for lightning current measurements has been developed that features reduced weight, a broad bandwidth, and immunity of the data transmission against electromagnetic interference (EMI).