Patent ID: 6687011
Filing Date: 2004-02-03
Classification: G01B,G01D,G01K

Abstract:
A transmission-type extrinsic Fabry-Perot interferometric optical fiber sensor comprising:a first single-mode optical fiber and a second single-mode optical fiber, the first single-mode optical fiber inserted into one end of a capillary quartz-glass tube and the second single-mode optical fiber inserted into the other end of the capillary quartz-glass tube, ends of the first single-mode optical fiber and the second single-mode optical fiber being perpendicular to the direction of the optical fibers, an air gap formed between the first single-mode optical fiber and the second single-mode optical fiber in the capillary quartz-glass tube, a gap length of the air gap varying in response to a transformation of the capillary quartz-glass tube attached to an object to be measured; a laser device for launching light into the first single-mode optical fiber; and an optical detector for detecting an occurrence of interferometric fringes of the light, having passed through the first single-mode optical fiber, the air gap, and the second single-mode optical fiber, and for monitoring the number of occurrences of the interferometric fringes and a slope sign of a series of signal levels, said signal level being a defined signal with data at a middle position between neighboring peaks and valleys of the occurring interferometric fringes, so that a magnitude and a direction of the transformation of the object could be determined on the basis of the number of occurrences of the interferometric fringes and the slope sign, respectively.