Fiber-linked Faraday effect current sensor by use of a flint glass cell with dielectric-coated retardation-compensated total reflection surfaces

A new type of Faraday effect optical current transformer has been developed that uses a single block of square flint glass with dielectric-coated total reflection surfaces as the sensing element. Numerical calculation has shown that the coating of two dielectric layers of 45.59-nm-thick Ta2O5 and 448.35-nm-thick SiO2 films on a flint glass surface produces zero retardation total reflection for the 45 degrees incident angle of light at lambda = 840 nm with great incident angle, wavelength, and film thickness tolerances. A fiber-linked current transformer has been constructed and experimentally demonstrated to exhibit high isolation from surrounding currents as well as high stability against mechanical disturbances.