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).