GB2149779A - Manufacture of optical fibre preforms - Google Patents

Manufacture of optical fibre preforms Download PDF

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Publication number
GB2149779A
GB2149779A GB08429033A GB8429033A GB2149779A GB 2149779 A GB2149779 A GB 2149779A GB 08429033 A GB08429033 A GB 08429033A GB 8429033 A GB8429033 A GB 8429033A GB 2149779 A GB2149779 A GB 2149779A
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GB
United Kingdom
Prior art keywords
tube
substrate
perforations
annular space
perforated tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08429033A
Other versions
GB2149779B (en
GB8429033D0 (en
Inventor
Bruce Armstrong Nichols
Ronald Albert Evans
Adrian Clement Greenham
John Stephen Mccormack
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co PLC
Original Assignee
General Electric Co PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Electric Co PLC filed Critical General Electric Co PLC
Publication of GB8429033D0 publication Critical patent/GB8429033D0/en
Publication of GB2149779A publication Critical patent/GB2149779A/en
Application granted granted Critical
Publication of GB2149779B publication Critical patent/GB2149779B/en
Expired legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/50—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges
    • C23C16/511—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating using electric discharges using microwave discharges
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/01413—Reactant delivery systems
    • C03B37/0142—Reactant deposition burners
    • C03B37/01426—Plasma deposition burners or torches
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
    • C03B37/01815—Reactant deposition burners or deposition heating means
    • C03B37/01823—Plasma deposition burners or heating means
    • C03B37/0183—Plasma deposition burners or heating means for plasma within a tube substrate
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/04—Coating on selected surface areas, e.g. using masks
    • C23C16/045—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Plasma & Fusion (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Geochemistry & Mineralogy (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

In the method of making optical fibre preforms by a process in which a chemical reaction is caused to take place in a gaseous mixture passed radially through perforations (11) in a tube (3) towards a coaxially disposed glass surface (1) by means of a plasma column generated by a microwave generator (15), resulting in the deposition of a coating on said surface (1), the part of the plasma extending beyond the perforations can cause etching of the glass surface to occur, and impurities from this process are then carried into the deposition zone and thus contaminate the preform. By providing two microwave generators (15), one at each end of the apparatus, and by exhausting the deposition tube from both ends (2), this problem is overcome and a longer and more uniform preform can be made. <IMAGE>

Description

SPECIFICATION Manufacture of optical fibre preforms This invention relates to the manufacture of glass preforms, from which optical fibre waveguides can be produced by drawing, by a method of the type (hereinafter referred to as the type specified) in which a chemical reaction is caused to take place between oxygen and the vapour or vapours of one or more compounds such as halides, which reaction results in the formation of a coating composed essentially of one or more oxides on a glass surface substrate; the substrate surface on which the coating is formed may be the interior surface of a glass tube or the exterior surface of a glass core.
This method, and forms of apparatus used for carrying out this method, is disclosed in our copending Patent Application No. 8204914 (Publication No. 2093829) and reference should be made to this for further details of the method.
In a first form of the method disclosed in the above patent application, the substrate consists of a glass tube, an inner tube which has a multiplicity of perforations through its wall is supported coaxially within the substrate tube, and the gaseous reaction mixture consisting of oxygen and the vapour or vapours, possibly carried by an additional carrier gas, is or are introduced into the annular space between the inner perforated tube and the substrate tube by being passed into the inner tube so as to emerge through said perforations into the space, the gas pressure within the inner tube being maintained higher than that in the space, while heat is applied to the exterior of at least a major part of the length of the substrate tube, and a chemical reaction is caused to take place throughout the said space by generating energy in said space, whereby a coating of solid material resulting from said reaction is formed simultaneously on the whole of the interior surface of the heated length of the substrate tube.
The gaseous mixture is usually introduced into the inner tube through one end, the other end being closed or restricted to ensure that the reactant gases leave the inner tube only through the perforations. in order to maintain the pressure differential between the inner tube and the annular space, the residual gaseous reactants, carrier gas and the gaseous reaction products are removed by constant exhaustion of this space by suitable pumping means.
In the method described in said co-pending patent application the energy is generated in the space by means of a microwave generator located at an end of the tube assembly and the waste reaction products are pumped out from the same end.
However it has been found that the part of the plasma which extends beyond the said perforations at the end of the assembly remote from that at which the gaseous products are removed gives rise to the etching away of the exposed surfaces of the glass substrate tube and perforated tube at that region, and this results in the release of metallic impurities which tend to be carried into the deposition zone where they may be deposited on the substrate with the required coating material and thus contaminate the preform.
It is thus an object of the present invention to provide a method of manufacturing an optical fibre preform in which the above disadvantage is overcome or at least alleviated.
It is a further object of the present invention to provide a method of manufacturing an optical fibre preform which can be made longer and with a more uniform core than has been possible up to now.
Accordingly, the present invention provides a method of manufacturing a glass optical fibre preform in which a coating composed essentially of one or more oxides is formed on a surface of an elongate cylindrical substrate by causing a chemical reaction to take place between oxygen and the vapour or vapours of one or more compounds capable of reacting with oxygen to produce the desired coating material, wherein a tube which has a multiplicity of perforations through its wall is supported coaxially with the substrate, an annular space being provided between said tube and the substrate, and a gaseous mixture consisting of oxygen and said vapour or vapours, and optionally an additional carrier gas, is or are introduced simultaneously at both ends of said tube and caused to flow through the perforations in said tube and into the annular space, a sufficient gas pressure differential being maintained between the interior and exterior of said tube to cause gas to flow through the perforations into said annular space, while at least a major part of the length of the substrate is maintained at an elevated temperature, and a chemical reaction is caused to take place within the annular space by providing a plasma in the gaseous mixture in the annular space between the substrate and the coaxial perforated tube by means of two microwave energy generators, one positioned at each end of the substrate, whereby a coating of solid material resulting from the said reaction is formed simultaneously on the whole of the said surface of the heated length of the substrate, while residual gases and gaseous reaction products are withdrawn from said annular space by constant exhaustion of said space from both ends of said space.
As mentioned above, the substrate may be a glass tube required to be coated on its internal surface, and the tube having a multiplicity of perforations may then be supported coaxially within the substrate. The gaseous reaction mixture is then passed into both ends of the inner tube and passes radially outwardly through the perforations into the annular space between the perforated tube and the substrate.
Alternatively, as disclosed in the above-mentioned patent application, the substrate may be an elongate seed core which is supported coaxially within a tube having a multiplicity of perforations through its wall. In this case the perforated tube is surrounded by a coaxial outer tube, an annular duct being provided between the inner perforated tube and the outer tube, and the said gaseous re action mixture is passed into both ends of said duct under sufficient pressure to cause passage thereof through the perforations of the inner tube into the annular space between the inner tube and the seed core, while the seed core is maintained at an elevated temperature and a chemical reaction is caused to take place within said space by generating a plasma in said space, whereby a coating of solid material resulting from the said reaction is formed on the whole surface of the seed core.
One application of the present invention to the method disclosed in the above-mentioned patent application will now be described by way of example with reference to the drawing which shows, in part-sectional elevation, the apparatus employed for carrying out the method in accordance with the invention.
Referring to the drawing, a vitreous silica substrate tube 1, supported vertically, has an inner tube 3 of vitreous silica supported coaxially within it forming an annular space 5 between the tubes 1 and 3.
The open ends 9 of the tube 3 are each connected to means (not shown) for supplying the required mixture of oxygen, carrier gas and reactant vapour or vapours to this tube, and the wall of the tube 3 is pierced by a multiplicity of perforations 11 to permit egress of the gases into the space 5 which constitutes the reaction zone. The ends 2 of the substrate tube 1 are connected to vacuum pumps (not shown) for exhaustion of the tube as indicated by the arrows.
Microwave cavities formed of an outer cylinder 13 and an inner cylinder 14 of predetermined height, are located adjacent to the gas exit ends 2 of the tube 1, each end of the tube being inserted through the cylinders 14. Power is supplied to the cavities from microwave generators 15 which should produce microwaves of slightly different frequencies in order to avoid problems of interference. The cylinder 14 may be formed in two portions enabling its height to be adjusted telescopically. A waveguide tube 16 of circular cross-section, formed of conductive, high temperature-resistant material, such as Inconel, or possibly graphite, as is described in our co-pending application No.8334014, is also positioned around the substrate tube, extending from the top of one microwave cavity to the other, and the tube 16 is sur rounded by a tubular electric furnace (not shown).
In a specific example of the invention, the appa ratus described above is employed in the products tion of a graded refractive index preform consisting of an undoped silica layer applied to the silica substrate tube 1, a cladding layer having a lower refractive index than that of silica and com prising, for example, silica doped with boron oxide (B2O3) and a graded index core layer of silica doped with germania and boron oxide, with the proportions of germania and boron oxide increasing and decreasing respectively with distance from the under lying cladding layer to give the required graded index, the various layers being formed as vitreous depositions on the interior surface of the tube wall.Initially argon and oxygen are passed into the inlets 9 of the inner tube 3 and pass through the perforations into the annular space 5 and power is supplied to the microwave cavities 12. When the plasma 18 (shaded portion) has been established in the space 5, and the furnace has heated up to the required temperature, a further stream of argon is bubbled through liquid silicon tetrachloride to entrain a vapour which provides the initial silica layer, and subsequently further streams are passed through liquids whose vapours provide the required dopants, these further streams which entrain the required vapours being mixed with the main argon stream and passed into the tube 3 at predetermined flow rates.The vapours are thus mixed with the oxygen and when they pass through the perforations into the plasma in the space 5, they dissociate and are deposited on the inner wall of the substrate tube 1 where they react to form the required coatings of glass.
The gaseous reaction products, carrier gas and remaining reactants are pumped out from the ends 2 of the tube 1 at a rate which provides a reduced pressure in the space 5 compared to that in the inner tube 3.
The tube with its deposited layers is then collapsed to form a longer preform with a more uniform core than has been possible up to now, and is easier to manufacture.
The perforations 11 in the tube 3 may be varied in respect of number, diameter or distribution along the length of the tube, if necessary, to obtain a more uniform gas flow and distribution into the annular space 5 between the tubes 1 and 3. Thus in some cases an increased number of perforations per unit length may be provided towards the central region of the tube 3 to counteract any drop in pressure along the tube from its ends; alternatively the diameter of the perforations may increase towards the central region of the tube for the same purpose.
The method may be used to provide other coatings than those described to provide preforms for the manufacture of different optical fibres, either graded index or step index fibres, the coating materials being selected accordingly. Among other dopants that could be employed are P2Os and fluorine.
It will be understood that the term "glass preform" includes within its scope glass tubes which may be used in the production of optical fibre waveguides, but which need to undergo further treatment or processing or to be combined with other glass structures before being drawn to form such waveguides.

Claims (4)

1. A method of manufacturing a glass optical fibre preform in which a coating composed essentially of one or more oxides is formed on a surface of an elongate cylindrical substrate by causing a chemical reaction to take place between oxygen and the vapour or vapours of one or more com pounds capable of reacting with oxygen to pro duce the desired coating material, wherein a tube which has a multiplicity of perforations through its wall is supported coaxially with the substrate, an annular space being provided between said tube and the substrate, and a gaseous mixture consisting of oxygen and said vapour or vapours, and optionally an additional carrier gas, is or are introduced simultaneously at both ends of said tube and caused to flow through the perforations in said tube and into the annular space, a sufficient gas pressure differential being maintained between the interior and exterior of said tube to cause gas to flow through the perforations into said annular space, while at least a major part of the length of the substrate is maintained at an elevated temperature, and a chemical reaction is caused to take place within the annular space by providing a plasma in the gaseous mixture in the annular space between the substrate and the coaxial perforated tube by means of two microwave energy generators, one positioned at each end of the substrate, whereby a coating of solid material resulting from the said reaction is formed simultaneously on the whole of the said surface of the heated length of the substrate, while residual gases and gaseous reaction products are withdrawn from said annular space by constant exhaustion of said space from both ends of said space.
2. A method according to Claim 1 wherein said substrate is a glass tube and said perforated tube is supported coaxially within the substrate, the gaseous reaction mixture being passed into both ends of the perforated tube and passing radially outwardly through the perforations into the annular space between the substrate and the perforated tube.
3. A method according to Claim 1 wherein said substrate is an elongate seed core supported coaxially within said perforated tube and wherein said perforated tube is surrounded by a coaxial outer tube, an annular duct being provided between the inner perforated tube and the outer tube, and the said gaseous reaction mixture is passed into both ends of the duct under sufficient pressure to cause passage thereof through the perforations of the inner perforated tube into the annular space between the substrate and said inner perforated tube.
4. A method of manufacturing a glass optical fibre preform substantially as hereinbefore described with reference to the drawing.
GB08429033A 1983-11-18 1984-11-16 Manufacture of optical fibre preforms Expired GB2149779B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB838330821A GB8330821D0 (en) 1983-11-18 1983-11-18 Manufacture of optical fibre preforms

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GB8429033D0 GB8429033D0 (en) 1984-12-27
GB2149779A true GB2149779A (en) 1985-06-19
GB2149779B GB2149779B (en) 1987-01-28

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GB08429033A Expired GB2149779B (en) 1983-11-18 1984-11-16 Manufacture of optical fibre preforms

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261742A1 (en) * 1986-09-26 1988-03-30 Philips Patentverwaltung GmbH Method and apparatus for coating the inside of tubes
EP0309117A1 (en) * 1987-09-25 1989-03-29 THE GENERAL ELECTRIC COMPANY, p.l.c. Manufacture of optical fibre preforms
US5000773A (en) * 1986-06-20 1991-03-19 Georges Le Noane Process for producing preforms for optical fibers
WO1999035304A1 (en) * 1997-12-31 1999-07-15 Plasma Optical Fibre B.V. Pcvd apparatus and a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
NL1019076C2 (en) * 2001-10-01 2003-04-02 Draka Fibre Technology Bv Method for applying one or more glass layers to the external surface of a rod-shaped molded part composed of glass, as well as a device suitable therefor.
US6715441B2 (en) 1997-12-31 2004-04-06 Plasma Optical Fibre B.V. PCVD apparatus and a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
WO2009118360A1 (en) * 2008-03-25 2009-10-01 Becton Dickinson France Apparatus for plasma treatment of hollow bodies

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5000773A (en) * 1986-06-20 1991-03-19 Georges Le Noane Process for producing preforms for optical fibers
EP0261742A1 (en) * 1986-09-26 1988-03-30 Philips Patentverwaltung GmbH Method and apparatus for coating the inside of tubes
US4877938A (en) * 1986-09-26 1989-10-31 U.S. Philips Corporation Plasma activated deposition of an insulating material on the interior of a tube
EP0309117A1 (en) * 1987-09-25 1989-03-29 THE GENERAL ELECTRIC COMPANY, p.l.c. Manufacture of optical fibre preforms
US4936889A (en) * 1987-09-25 1990-06-26 The General Electric Company, P.L.C. Apparatus for the manufacture of optical fibre preforms
US6260510B1 (en) 1997-12-31 2001-07-17 Plasma Optical Fibre B.V. PCVD apparatus and method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
WO1999035304A1 (en) * 1997-12-31 1999-07-15 Plasma Optical Fibre B.V. Pcvd apparatus and a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
US6372305B2 (en) 1997-12-31 2002-04-16 Plasma Optical Fibre B.V. PCVD apparatus and a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
US6715441B2 (en) 1997-12-31 2004-04-06 Plasma Optical Fibre B.V. PCVD apparatus and a method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
US6849307B2 (en) 1997-12-31 2005-02-01 Plasma Optical Fibre B.V. Method of manufacturing an optical fiber, a preform rod and a jacket tube as well as the optical fiber manufactured therewith
NL1019076C2 (en) * 2001-10-01 2003-04-02 Draka Fibre Technology Bv Method for applying one or more glass layers to the external surface of a rod-shaped molded part composed of glass, as well as a device suitable therefor.
WO2003029158A1 (en) 2001-10-01 2003-04-10 Draka Fibre Technology B.V. Method and device for depositing glass layers on the external surface of a rod-like preform
CN1313401C (en) * 2001-10-01 2007-05-02 德拉卡纤维技术有限公司 Method and device for depositing glass layers on the external surface of a rod-like preform
WO2009118360A1 (en) * 2008-03-25 2009-10-01 Becton Dickinson France Apparatus for plasma treatment of hollow bodies
FR2929294A1 (en) * 2008-03-25 2009-10-02 Becton Dickinson France Soc Pa APPARATUS FOR PLASMA TREATMENT OF HOLLOW BODIES

Also Published As

Publication number Publication date
GB2149779B (en) 1987-01-28
GB8429033D0 (en) 1984-12-27
GB8330821D0 (en) 1983-12-29

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19941116