Patent ID: 6798524
Filing Date: 2004-09-28
Classification: G01H

Abstract:
A phase difference calculation method using an optical fiber ring interference sensor including a light source, a plurality of photo detectors, an optical fiber loop, and a NÃ—N optical splitting coupler connected to the light source, the photo detectors, and open ends of the optical fiber loop, in which in order to detect a physical variation caused in the optical fiber ring interference sensor, the NÃ—N optical splitting coupler splits the light emitted by the light source, the optical fiber loop inputs split lights through both open ends of the optical fiber loop, the lights are propagated through the optical fiber loop in clockwise direction and counter clockwise direction, the NÃ—N optical splitting coupler couples the propagation lights in clockwise direction and counter clockwise direction, and the photo detectors detect the coupled propagation light, and then outputs signals indicating a variation of a light intensity of interference between the propagation lights having a phase difference in clockwise direction and counter clockwise direction,the phase difference calculation method comprising: measuring the light intensities of interference of a different non-reciprocal phase bias not less than two times detected from a plurality of the photo detectors; and calculating a phase difference based on the light intensities when the light intensity detected from each photo detector is within a predetermined section corresponding to each photo detector.