Patent ID: 8461822
Filing Date: 2013-06-11
Classification: G01R

Abstract:
1. A fiber optic current sensor or magnetic field sensor comprising: a sensing fiber exposed to a magnetic field of a current I, wherein said sensing fiber is looped in a sensor coil plane, and wherein said sensing fiber has a Verdet constant V, at least one retarder arranged between a polarization-maintaining fiber and said sensing fiber for converting light between linear and elliptical polarization, wherein a principal axis of said polarization-maintaining fiber is rotated with respect to a normal of said sensor coil plane by an angle β and wherein said retarder introduces a retardation ρ=π/2+ε between light waves polarized along its principal axes, with ε being an additional, non-zero phase shift; and a control unit generating a signal proportional to a phase shift Δφ, which signal is proportional to 4 S(ε, δ, β, φ wherein β, ε and are such that is fulfilled over a range of values of φ at least at a temperature T 0 , in particular in a center of an operating temperature range of the sensor, with t 1 being a first threshold value smaller than 7*10 −5 1/K, in particular smaller than 2*10 −5 1/K.