Measurement and calibration of fiber coating geometry by grey-scaleanalysis

Measurement of the coating geometry of optical fibers is important in maintaining the optical and mechanical integrity of fibers and in the control of splice loss in multiple-fiber ribbons. A method of measuring coating geometry using a side-view system with a novel dark-field illumination technique is presented. A high contrast image is produced with this system from which the coating diameter noncircularity and concentricity error of a fiber can be determined. The measurement repeatabilities of coating diameter and concentricity error are typically 0.20 μm and 0.25 μm respectively. A means of calibrating the side-view system using a glass rod has been developed and comparison with an interferometric method has shown that a total uncertainty on outer coating diameter of 0.5 μm has been achieved