Bell Telephone Laboratories

Thomas John Miller

Raymond Edward Jaeger

James W Fleming, Jr

John Burnette MacChesney

The modified chemical vapor deposition process is practiced using an rf source as the external heat source. An rf plasma is thus established within a glass tube through which appropriate glass precursor vapors are passed. As a result of the ensuing chemical reactions, particulate material is formed within the tube and deposits on it. The hot plasma zone may be used to consolidate this particulate material into a transparent glass, and onto the interior wall of the tube. The tube is subsequently drawn into an optical fiber.

Modified chemical vapor deposition of an optical fiber using an rf plasma

High silica content optical glasses, containing more volatile oxides such as GeO.sub.2 and B.sub.2 O.sub.3, are produced by plasma fusion of powders without inordinately high loss of the more volatile constituents. The powders are produced by a process including the heat treatment of intimately mixed materials, which include the glass forming constituents. Small quantities of GeO.sub.2 are included in borosilicate glass to suppress bubble formation. Pairs of glass compositions have been found, with sufficient index of refraction difference to produce guidance in optical transmission lines, while possessing sufficient thermal expansion match to reduce stresses in the line.

GeO.sub.2 -B.sub.2 O.sub.3 -SiO.sub.2  Optical glass and lightguides

A procedure is described for drawing glass fibers which are particularly suitable for use in optical waveguides. A laser is used as a souce of heat and an optical system is provided for focusing an annular beam around a glass preform from which the glass fiber is drawn. Particular attention is devoted to the optical focusing system to provide highly uniform distribution of heat and insure very precise short and long term fiber diameter control and precise control of the optical properties (freedom from scattering centers, profile of optical properties across the diameter) of the fiber. Precise diameter control of glass fibers for optical waveguides is highly desirable because it minimizes optical losses and facilitates low-loss splicing of individual glass fibers.

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Thomas John Miller