A new type of Faraday effect current sensor consisting of a single SF57 glass block having dielectric multilayer mirrors coated to have polarization-preserving perfect reflection and containing no parasitic field sensitive parts is developed. A good isolation froffi the external current and field is demonstrated.

A new scheme is proposed for achieving a closed, homogeneous, and isotropic optical circuit necessary for high-accuracy optical-current sensors. It makes use of a single solid polygonal solid with reflection surfaces coated by quarter-wavelength dielectric thin-film layers for the Faraday cell. We derive the design principle and show numerically its applicability in various Faraday materials. The cross talk with the surrounding current is investigated in particular detail both theoretically and experimentally. In the example experiment with a SF57 Faraday material, a low cross talk is demonstrated for nearby currents.

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