US 6,253,580 B1 · Method of making a tubular member for optical fiber production using plasma outside vapor deposition

Abstract

An apparatus and method for producing a tubular member, which is suitable for use as a starter tube or an optical fiber preform, on a rotating cylindrical target mounted on a lathe. The tubular member is made by means of plasma outside vapor deposition. In this process, a source gas comprising SiCl4 and, optionally, a fluorine-laden chemical, is introduced into an air plasma. Both the air and the source gas are dry gases and have low hydroxyl content. The air plasma is created by a high-frequency induction plasma torch which travels along the length of the target on a carriage. The torch is provided with a short U-shaped gutter on either side of its rim directly beneath the target and the growing tubular member. This gutter helps channel reaction products of the source gas and the plasma so as to enhance deposition on the growing tubular member. The torch is further provided with an induction coil having a plurality of windings, the uppermost winding being maintained a predetermined distance from the surface of the tubular member as the latter is built up.

Claims5

Dependent claims

A method for forming a substantially pure silica glass starter tube on a graphite target, the starter tube having a purity and index of refraction suitable for use in optical fiber formation, said method comprising steps of:

providing a high frequency induction plasma torch comprising a coil, said induction plasma torch being selectively positionable along a length of said target, a spacing of 30-35 mm separating the target from said coil;
introducing a plasma gas consisting essentially of a gas from a group consisting of (air, and a mixture of oxygen and nitrogen) and having a hydroxyl content of less than 2 ppm into the induction plasma torch to form a plasma within said coil;
injecting a source gas having at least SiCl4 and having a hydroxyl content of less than 0.5 ppm into said plasma;
depositing at least one reaction product of said plasma and said source gas onto the graphite target while maintaining said spacing between said target and the coil;
and
removing said graphite target to obtain said substantially pure silica glass tube.

3 more elements

Dependencies are inferred from the claim text.

Method of making a tubular member for optical fiber production using plasma outside vapor deposition

Life of this patent

Method of making a tubular member for optical fiber production using plasma outside vapor deposition

Life of this patent

Abstract

Claims5