Patent ID: 7102757
Filing Date: 2006-09-05
Classification: G01R

Abstract:
1. In a method for measurement of current by means of an in-line Sagnac interferometer of the type in which a first non-reciprocal phase shift between two orthogonal polarization modes of a light beam passing through the interferometer is produced by a current, and the phases of the polarization modes changed by a second non-reciprocal phase shift in accordance with the Pockels effect to compensate for the first phase shift to determine the first phase shift, the improvement comprising the steps of: a) providing a plurality of binary-gradated electromagnetic fields; then b) passing the polarization modes through said binary-gradated electromagnetic fields to effect said second phase shift so that said second phase shift comprises a shift of a characteristic curve of the interferometer to a region of maximum linearity; and then c) varying the field strengths of said electromagnetic fields so that said characteristic curve is shifted independently by ±1.5 π or 0.5 π.