Corning Incorporated

Jerald B Dotson

Bruce Warren Reding

Leslie J Button

Jerry D Nease

Christopher W Wightman

A method for measuring the diameter of a transparent filament is provided which is substantially insensitive to ellipticity of the filament. The method comprises using an interference technique to measure the filament diameter at two locations which are spaced apart by an amount such that a plot of diameter versus angle of rotation for an elliptical filament calculated at the first location is approximately 90.degree. out of phase from the same plot calculated at the second location. Due to the phase difference, the average of the two measurements is substantially insensitive to ellipticity. For measurement apparatus comprising one laser and two detectors and for optical waveguide fibers having a cladding composed of fused silica, the two locations can be about 123.degree. apart. In other embodiments, a method for characterizing the non-circularity of a filament is provided. Apparatus for practicing the foregoing methods is also disclosed.

Method for measuring diameters of non-circular fibers

Methods for deteting defects, such as, holes or voids, in optical waveguide fibers are provided. The methods employ far-field interference patterns produced by transversely illuminating the fiber with a laser beam. Holes in the fiber produce a characteristic peak in the spatial frequency spectrum of the interference pattern which subdivides into two peaks which migrate in opposite directions as a hole grows in size. Holes also produce a characteristic increase in the total power of the interference pattern, the amount of the increase being a linear function of the size of the hole for holes having a diameter less than about 60% of the diameter of the fiber. The hole detection methods are incorporated in an overall system for controlling the drawing of optical waveguide fibers.

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Los Angeles, CA, United States of America

Jerald B Dotson