A method and device for current measurement by means of a fibre optic in - line - - sagnac interferometer and suitable for this purpose, the phase modulator

摘要

A method for the measurement of current by means of a fibre optic in - line - - sagnac interferometer (20), in which between two orthogonal polarization modes of the interferometer (20) light beam passing through by a current to be measured a first non-reciprocal phase shift is generated, for the determination of the first phase shift, the phases of the polarization modes under utilization of the pockel - effect by a second non-reciprocal phase shift in addition be changed in such a way that, as the second phase shift a compensation of the first phase shift is effected, characterized in that the second phase shift by means of a plurality of graduated in binary form of electromagnetic fields takes place, by means of which the polarization modes, respectively, and the second phase shift of a displacement of the characteristic curve of the interferometer (20) in a range of maximum linearity, wherein the field strengths of the individual electromagnetic fields are varied in such a way that the characteristic curve of the interferometer (20) is stochastically independent about + / – 1,5 π or + / – 0,5 π is displaced in their phase.