Geometrical Fiber Configuration for Isolators and Magnetometers

Due to the Faraday effect, the presence of a longitudinal magnetic field (math) modifies the phase of a circularly polarized light wave, by an amount determined by the Verdet coefficient of the medium. The sign of this phase shift depends on the left or right handed character of the polarization, and also on the relative senses of the field and light propagation vectors. The phase shift may be detected in a ring interferometer where identical circularly polarized waves counterpropagate around the ring, or it may manifest itself as a change in the orientation of linearly polarized light resulting from the opposite phase shifts of its co-propagating left and right hand circularly polarized components.