Method for producing an optical preform with a POD cladding glass layer

Patent metadata

Field	Value
Publication number	US-9296639-B2
Application number	US-201314420572-A
Country	US
Kind code	B2
Filing date	Aug 8, 2013
Priority date	Aug 9, 2012
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

The invention relates to a plasma deposition process for producing an optical preform, which is characterized by a cladding glass layer having a non-round internal cross-section together with high fluorine doping and axially and radially specified dopant distribution, which in the simplest case is as uniform as possible. For this purpose, a two-stage method is proposed, wherein a substrate body having a non-round cross-section is first reshaped into a coated substrate body having a circular cross-section in that a POD filling layer made of quartz glass having the nominal fluorine concentration is deposited onto a present filling surface and rounded by grinding, and then in the second stage of the method a POD sheathing glass layer made of fluorine-doped quartz glass and having a circular-ring-shaped cross-section is deposited.

First claim

The invention claimed is:

1. A method for producing an optical preform with a POD cladding glass layer of fluorine-doped quartz glass, said method comprising:
forming SiO 2 particles with a plasma burner in the presence of fluorine,
depositing said SiO 2 particles on an outer cylinder surface of a cylindrical substrate body having a longitudinal axis, and
vitrifying said particles directly,
said substrate body having a non-round cross-section taken perpendicular to the longitudinal axis including at least one surface section that extends between support points of an enveloping circle of said cross-section and that either has no curvature or has a curvature that is different from the curvature of the enveloping circle,
wherein the forming, depositing and vitrifying steps include:
(a) producing a POD filling layer of quartz glass with fluorine in a nominal concentration on said surface section, so as to form a coated substrate body, said coated substrate body having a circular cross-section having a radius that is at least as great as a radius of the enveloping circle; and
(b) depositing a POD enveloping glass layer having a of circular cross-section, said POD enveloping glass layer being of fluorine-doped quartz glass on the coated substrate body.

2. The method according to claim 1 , wherein the producing of the POD filling layer on the surface section comprises:
(aa) depositing a POD precursor layer of the quartz glass with the nominal concentration of fluorine on the surface section;
(bb) removing the portions of the POD precursor layer projecting over the enveloping circle so as to form the coated substrate body with circular cross-section.

3. The method according to claim 2 , wherein during depositing of the POD precursor layer the substrate body is continuously rotated about the longitudinal axis to deposit a surrounding POD precursor layer annularly enclosing a cylinder jacket of the substrate body.

4. The method according to claim 2 , wherein the depositing of the POD precursor layer is exclusively or predominantly carried out on the surface section.

5. The method according to claim 2 , wherein all of the portions of the POD precursor layer that are projecting over the enveloping circle are removed.

6. The method according to claim 1 , wherein a substrate body is used that, viewed in the direction of its longitudinal axis, has a polygonal cross-section.

7. The method according to claim 6 , wherein all corners of the polygon are located on the enveloping circle.

8. The method according to claim 1 , wherein the substrate body, viewed in the direction of the longitudinal axis, comprises at least a portion with D-shaped cross-section.

9. The method according to claim 1 , wherein a substrate body is used that, viewed in the direction of the longitudinal axis, has a square, rectangular, hexagonal or octagonal cross-section.

Assignees

• Heraeus Quarzglas

Inventors

• Schoetz Gerhard
• Bräuer Karsten
• Schmidt Richard
• Bauer Peter
• Schultheis Andreas
• Bödiger Paul
• Langner Andreas

Classifications

• C03B2203/12

  Non-circular or non-elliptical cross-section, e.g. planar core · CPC title

• C03B37/01291 Primary

  by progressive melting, e.g. melting glass powder during delivery to and adhering the so-formed melt to a target or preform, e.g. the Plasma Oxidation Deposition [POD] process · CPC title

• C03B2201/12

  doped with fluorine (C03B2201/14 takes precedence) · CPC title