CA1054795A - Optical fibres - Google Patents
Optical fibresInfo
- Publication number
- CA1054795A CA1054795A CA172,817A CA172817A CA1054795A CA 1054795 A CA1054795 A CA 1054795A CA 172817 A CA172817 A CA 172817A CA 1054795 A CA1054795 A CA 1054795A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- layer
- bore
- index
- refraction
- 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.)
- Expired
Links
- 230000003287 optical effect Effects 0.000 title description 6
- 238000005253 cladding Methods 0.000 claims abstract description 29
- 239000000835 fiber Substances 0.000 claims abstract description 22
- 239000011521 glass Substances 0.000 claims abstract description 21
- 239000011248 coating agent Substances 0.000 claims abstract description 18
- 238000000576 coating method Methods 0.000 claims abstract description 18
- 238000006243 chemical reaction Methods 0.000 claims abstract description 13
- 239000007787 solid Substances 0.000 claims abstract description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 52
- 239000000377 silicon dioxide Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 16
- 238000004519 manufacturing process Methods 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 9
- 239000013307 optical fiber Substances 0.000 claims description 9
- 238000000151 deposition Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 6
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 claims description 5
- 239000005049 silicon tetrachloride Substances 0.000 claims description 5
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 2
- 239000001301 oxygen Substances 0.000 claims description 2
- 229910052760 oxygen Inorganic materials 0.000 claims description 2
- 239000010410 layer Substances 0.000 claims 31
- 239000012792 core layer Substances 0.000 claims 1
- 238000010494 dissociation reaction Methods 0.000 claims 1
- 230000005593 dissociations Effects 0.000 claims 1
- 238000007524 flame polishing Methods 0.000 claims 1
- 238000007789 sealing Methods 0.000 claims 1
- 239000003153 chemical reaction reagent Substances 0.000 abstract description 10
- 238000011109 contamination Methods 0.000 abstract description 3
- 239000011162 core material Substances 0.000 description 15
- 230000008021 deposition Effects 0.000 description 4
- 230000033001 locomotion Effects 0.000 description 4
- 239000005350 fused silica glass Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 101100293261 Mus musculus Naa15 gene Proteins 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000007496 glass forming Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000003455 independent Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4429—Means specially adapted for strengthening or protecting the cables
- G02B6/44382—Means specially adapted for strengthening or protecting the cables the means comprising hydrogen absorbing materials
-
- 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
-
- 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
- C03B37/01853—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
-
- 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
- C03B37/01861—Means for changing or stabilising the diameter or form of tubes or rods
-
- 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
- C03B37/01861—Means for changing or stabilising the diameter or form of tubes or rods
- C03B37/01869—Collapsing
-
- 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
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
- C03B37/02754—Solid fibres drawn from hollow preforms
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/20—Doped silica-based glasses doped with non-metals other than boron or fluorine
- C03B2201/28—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with phosphorus
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/32—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with aluminium
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
- C03B2201/42—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn doped with titanium
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2205/00—Fibre drawing or extruding details
- C03B2205/12—Drawing solid optical fibre directly from a hollow preform
- C03B2205/13—Drawing solid optical fibre directly from a hollow preform from a hollow glass tube containing glass-forming material in particulate form, e.g. to form the core by melting the powder during drawing
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2205/00—Fibre drawing or extruding details
- C03B2205/12—Drawing solid optical fibre directly from a hollow preform
- C03B2205/16—Drawing solid optical fibre directly from a hollow preform the drawn fibre consisting of circularly symmetric core and clad
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Manufacture, Treatment Of Glass Fibers (AREA)
- Surface Treatment Of Glass Fibres Or Filaments (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The bore of a glass tube is coated with a first layer of cladding glass of equal or higher refractive index than that of the tube and a second layer of core glass of higher refractive index than that of the first layer. The coated tube is then drawn into a fibre while collaps-ing the bore to form a solid core surrounded by cladding. An r.f. glow discharge vapor reaction with particular reagents in the tube produces the desired coating and provides reduced contamination.
The bore of a glass tube is coated with a first layer of cladding glass of equal or higher refractive index than that of the tube and a second layer of core glass of higher refractive index than that of the first layer. The coated tube is then drawn into a fibre while collaps-ing the bore to form a solid core surrounded by cladding. An r.f. glow discharge vapor reaction with particular reagents in the tube produces the desired coating and provides reduced contamination.
Description
~054795 Background of the Invention Field of the Invention This invention relates to the manufacture of optical fibres and particularly to an improved method of coating the bore of a glass tube.
Description of the Prior Art United States Patent No. 3,659,915 issued May 2, 1972 describes a process for making optical fibres wherein a layer of doped fused silica is formed on the inside wall of a tube of pure fused silica and the composite structure is drawn to collapse the inner layer to form a solid core surrounded by pure fused silica. This process requires the use of a glass tube of high optical purity which is quite costly and the drawing step introduces un-desired contamination.
Summary of the Invention According to one aspect of the present invention there is provided in a method of making an optical fiber, the steps of: heat treating the bore of a hollow silica glass tube under vacuum to remove moisture and prevent formation of oxygen-hydrogen compounds in the fiber; coating the heat treated bore with a first silica glass layer in a hydrogen-free atmosphere;
coating a second silica layer on said first silica layer, said second silica layer having a higher refractive index than said first silica layer; and collapsing said tube and coated bore to form a solid structure having a core and cladding layer, said core having a higher index of refraction than said cladding layer.
The tube is not necessarily a self supporting structure but may take the form of a deposited layer lining the bore of another tube. Methods suitable for depositing the glass layer include evaporation, r.f. sputtering, and r.f. excited vapour reaction.
According to another aspect of the present invention there is pro-vided a method of making a coated tube suitable for drawing into an optical fiber including the steps of: depositing a core glass layer on the inside of a tube by introducing glass forming vapor reagents into the bore of said tube; and heating said vapor reagents in said tube by means of a vapor reaction heating excitor moving relative to said tube whereby the heated vapor reagents proximate the vapor reaction heating e~citor are converted to glass on the inside of the tube, the relative movement between the tube and excitor causing a relatively uniform layer of glass to be deposited through-out the length of the tube to thereby form a coated tube.
Brief Description of the Drawings In the accompanying drawings which illustrate exemplary embodiments lQ of the present invention:
Figure 1 showS a prior art structure having a single core glass coating;
Figure 2 depicts the novel structure of the twice coated tube before drawing into a fibre;
Figure 3 depicts apparatus for coating the bore of a tube; and Figure 4 depicts alternative apparatus for coating the bore of a tube simultaneously with drawing it into a fibre to reduce contamination.
Description of the Preferred Embodiments Figure 1 depicts a prior art structure produced by a simple manu-2Q facturing process involving the deposition of only one layer 10 upon thebore of a hollow tube 11. The core of the completed fibre is provided by the material of the deposited layer 10 while the cladding is provided by the material of the tube 11.
In a single mode optical fibre, a significant proportion of the op-tical signal propagates in the tube or cladding. The transmissivity of the cladding material is therefore an important factor affecting the optical loss of the fibre. Normally however for mechanical reasons the thickness of the cladding is made much greater than the depth to which any significant propor-tion of the optical energy penetrates. Thus it is only the region of the cladding nearest the core which really needs to have a high transmissivity.
Advantage of this factor is taken in the manufacturing process used to produce the present novel structure depicted in Figure 2. The bore of a hollow silica glass tube 20, which can be slightly impure and glossy, is lined with a first layer 21 of low absorption silica cladding glass and then a further layer 22 of doped silica core glass. The core of the completed fibre is provided by the material of the second deposited layer 22, while the inner and outer regions of the cladding are provided respectively by the material of the first deposited layer 21 and the ,~
1054~795 material of the tube 20. The tube is thus spaced from the core and is not involved to any extent in light propagation. The outer region of the cladding can safely be made mcre glossy and of a less expensive glass than the other remainder of the fibre, but energy should not be coupled into it from the core. Therefore the outer tube refractive index must be equal to or less than and no greater than that of the inner cladding. The refractive index of this inner cladding must, in its turn, be less than that of the core which is of a higher refractive index. It may be noted that the refractive index of an absorbing medium is strictly a complex quantity and that it is the real part of the refractive index of the tube 20 which must be not greater than the refractive index of the layer 21.
The manufacturing process can also be used to produce a succession of layers upon the bore of a tube whose composition is chosen to produce a substantially quadratic grading of refractive index required in the production of a self-focusing multi-mode fibre.
In the manufacture of single mode fibre a deposited layer only 0.5 ~ thick may be required. This is within the known art of deposition of oxides without need for close matching of the expansion coefficients of the substrate and deposited layer glasses. More generally thicker layers are required, typically in the range 5 to 10 ~. in which case attention has to be paid to matching the various expansion coefficients. Suitable composit-ions can be selected from a wide range of known glasses, and in particular it is known that a variety of high silica content glasses can be adequately matched to a pure silica glass substrate.
A preferred manufacture for an optical fibre to carry GaAs laser radiation employs a silica tube 30, as shown in Figure 3, typically 7 mm external diameter with 1 mm wall thickness. The bore of the tube is flame polished and then vacuum baked to remove any traces of moisture. The pre-sence of moisture may produce -OH groups in the completed fibre with their attendant undesirable absorption in the region of 0.9 ~. After the tube has been baked it is placed so as to pass through the centre of an r.f. induction coil 31 and its ends are located in seals 32.
The higher refractive index core glass coating generally irst deposited upon the surface of the bore of the tube is the product of a known r.f. vapour reaction process producing a silica glass containing a few percent titania. The chemical reagents for this process are silicon tetrachloride, titanium tetrachloride, and oxygen. Both chlorides are liquids at room temperature, but are introduced to the reaction zone in vapour form by bubbl-ing dry nitrogen carrier gas through the liquid reagents maintained at con-stant temperature. The two liquid reagents are kept separate, and two inde-pendent gas streams are used for the entrainment. This enables the relative proportions of the two vapours at the reaction zone readily to be controlled merely by altering the relative flow rates. In the bore of the tube 30 the two vapours become mixed with a supply of dry oxygen gas. The reaction does not proceed spontaneously at room temperatures but is promoted in the local-i7ed region of the r.f. excited glow discharge.
A uniform coating along the length of the bore of the tube is pro-vided by progressive movement of the tube 30 through the coil 31 or by move-ment of the coil along the length of the tube. Uniformity of the deposited layer may be enhanced by rotating the tube about its axis during the deposit-ion process. A small reciprocating movement of the tube or coil in the axial direction may also be superimposed.
The drawing of the coated tube into a fibre in such a way as to collapse its bore is performed as a separate manufacturing step. The tip of the tube is introduced into a hot zone to soften it for pulling into a fibre.
Surface tension alone will suffice to convert the softened hollow tube into a solid structure, but may be assisted by maintaining the inside of the tube at a reduced pressure.
In the present case, where the quality of the initial silica tube is less pure, the supply of titanium tetrachloride vapour is shut off while a first cladding glass layer of pure silica of equal or higher refractive index than the tube is deposited in situ. The deposition process is then repeated using both titanium and silicon tetrachloride vapours so as to pro-duce a second doped silica layer of higher refractive index than that of the ~054795 first layer and which will form the core of the completed fibre.
The deposition of the core material layer upon the bore of a tube following the deposition of the first cladding layer may be arranged to take place concurrently with the drawing of the tube down into a fibre. Figure 4 depicts an example of this technique. A silica tube 40, typically in the range 15 to 25 mm external diameter and 1 to 3 mm wall thickness, is lowered through a ring heater 41 which softens the tip of the tube enabling it to be pulled into a fibre 42. The same reagents as were used in the example described above with reference to Figure 3 are also used in this reaction to deposit the first and second layers. These reagents are introduced into the tube 40 via a delivery pipe 43. The temperature required to soften the glass is also sufficient to promote the requisite chemical reaction of the reagents, and hence the second glass layer 44 is deposited which forms the central core 45 of the drawn fibre.
It is to be understood that the foregoing description of specific examples of this invention is made by way of example only and is not to be considered as a limitation on its scope.
Description of the Prior Art United States Patent No. 3,659,915 issued May 2, 1972 describes a process for making optical fibres wherein a layer of doped fused silica is formed on the inside wall of a tube of pure fused silica and the composite structure is drawn to collapse the inner layer to form a solid core surrounded by pure fused silica. This process requires the use of a glass tube of high optical purity which is quite costly and the drawing step introduces un-desired contamination.
Summary of the Invention According to one aspect of the present invention there is provided in a method of making an optical fiber, the steps of: heat treating the bore of a hollow silica glass tube under vacuum to remove moisture and prevent formation of oxygen-hydrogen compounds in the fiber; coating the heat treated bore with a first silica glass layer in a hydrogen-free atmosphere;
coating a second silica layer on said first silica layer, said second silica layer having a higher refractive index than said first silica layer; and collapsing said tube and coated bore to form a solid structure having a core and cladding layer, said core having a higher index of refraction than said cladding layer.
The tube is not necessarily a self supporting structure but may take the form of a deposited layer lining the bore of another tube. Methods suitable for depositing the glass layer include evaporation, r.f. sputtering, and r.f. excited vapour reaction.
According to another aspect of the present invention there is pro-vided a method of making a coated tube suitable for drawing into an optical fiber including the steps of: depositing a core glass layer on the inside of a tube by introducing glass forming vapor reagents into the bore of said tube; and heating said vapor reagents in said tube by means of a vapor reaction heating excitor moving relative to said tube whereby the heated vapor reagents proximate the vapor reaction heating e~citor are converted to glass on the inside of the tube, the relative movement between the tube and excitor causing a relatively uniform layer of glass to be deposited through-out the length of the tube to thereby form a coated tube.
Brief Description of the Drawings In the accompanying drawings which illustrate exemplary embodiments lQ of the present invention:
Figure 1 showS a prior art structure having a single core glass coating;
Figure 2 depicts the novel structure of the twice coated tube before drawing into a fibre;
Figure 3 depicts apparatus for coating the bore of a tube; and Figure 4 depicts alternative apparatus for coating the bore of a tube simultaneously with drawing it into a fibre to reduce contamination.
Description of the Preferred Embodiments Figure 1 depicts a prior art structure produced by a simple manu-2Q facturing process involving the deposition of only one layer 10 upon thebore of a hollow tube 11. The core of the completed fibre is provided by the material of the deposited layer 10 while the cladding is provided by the material of the tube 11.
In a single mode optical fibre, a significant proportion of the op-tical signal propagates in the tube or cladding. The transmissivity of the cladding material is therefore an important factor affecting the optical loss of the fibre. Normally however for mechanical reasons the thickness of the cladding is made much greater than the depth to which any significant propor-tion of the optical energy penetrates. Thus it is only the region of the cladding nearest the core which really needs to have a high transmissivity.
Advantage of this factor is taken in the manufacturing process used to produce the present novel structure depicted in Figure 2. The bore of a hollow silica glass tube 20, which can be slightly impure and glossy, is lined with a first layer 21 of low absorption silica cladding glass and then a further layer 22 of doped silica core glass. The core of the completed fibre is provided by the material of the second deposited layer 22, while the inner and outer regions of the cladding are provided respectively by the material of the first deposited layer 21 and the ,~
1054~795 material of the tube 20. The tube is thus spaced from the core and is not involved to any extent in light propagation. The outer region of the cladding can safely be made mcre glossy and of a less expensive glass than the other remainder of the fibre, but energy should not be coupled into it from the core. Therefore the outer tube refractive index must be equal to or less than and no greater than that of the inner cladding. The refractive index of this inner cladding must, in its turn, be less than that of the core which is of a higher refractive index. It may be noted that the refractive index of an absorbing medium is strictly a complex quantity and that it is the real part of the refractive index of the tube 20 which must be not greater than the refractive index of the layer 21.
The manufacturing process can also be used to produce a succession of layers upon the bore of a tube whose composition is chosen to produce a substantially quadratic grading of refractive index required in the production of a self-focusing multi-mode fibre.
In the manufacture of single mode fibre a deposited layer only 0.5 ~ thick may be required. This is within the known art of deposition of oxides without need for close matching of the expansion coefficients of the substrate and deposited layer glasses. More generally thicker layers are required, typically in the range 5 to 10 ~. in which case attention has to be paid to matching the various expansion coefficients. Suitable composit-ions can be selected from a wide range of known glasses, and in particular it is known that a variety of high silica content glasses can be adequately matched to a pure silica glass substrate.
A preferred manufacture for an optical fibre to carry GaAs laser radiation employs a silica tube 30, as shown in Figure 3, typically 7 mm external diameter with 1 mm wall thickness. The bore of the tube is flame polished and then vacuum baked to remove any traces of moisture. The pre-sence of moisture may produce -OH groups in the completed fibre with their attendant undesirable absorption in the region of 0.9 ~. After the tube has been baked it is placed so as to pass through the centre of an r.f. induction coil 31 and its ends are located in seals 32.
The higher refractive index core glass coating generally irst deposited upon the surface of the bore of the tube is the product of a known r.f. vapour reaction process producing a silica glass containing a few percent titania. The chemical reagents for this process are silicon tetrachloride, titanium tetrachloride, and oxygen. Both chlorides are liquids at room temperature, but are introduced to the reaction zone in vapour form by bubbl-ing dry nitrogen carrier gas through the liquid reagents maintained at con-stant temperature. The two liquid reagents are kept separate, and two inde-pendent gas streams are used for the entrainment. This enables the relative proportions of the two vapours at the reaction zone readily to be controlled merely by altering the relative flow rates. In the bore of the tube 30 the two vapours become mixed with a supply of dry oxygen gas. The reaction does not proceed spontaneously at room temperatures but is promoted in the local-i7ed region of the r.f. excited glow discharge.
A uniform coating along the length of the bore of the tube is pro-vided by progressive movement of the tube 30 through the coil 31 or by move-ment of the coil along the length of the tube. Uniformity of the deposited layer may be enhanced by rotating the tube about its axis during the deposit-ion process. A small reciprocating movement of the tube or coil in the axial direction may also be superimposed.
The drawing of the coated tube into a fibre in such a way as to collapse its bore is performed as a separate manufacturing step. The tip of the tube is introduced into a hot zone to soften it for pulling into a fibre.
Surface tension alone will suffice to convert the softened hollow tube into a solid structure, but may be assisted by maintaining the inside of the tube at a reduced pressure.
In the present case, where the quality of the initial silica tube is less pure, the supply of titanium tetrachloride vapour is shut off while a first cladding glass layer of pure silica of equal or higher refractive index than the tube is deposited in situ. The deposition process is then repeated using both titanium and silicon tetrachloride vapours so as to pro-duce a second doped silica layer of higher refractive index than that of the ~054795 first layer and which will form the core of the completed fibre.
The deposition of the core material layer upon the bore of a tube following the deposition of the first cladding layer may be arranged to take place concurrently with the drawing of the tube down into a fibre. Figure 4 depicts an example of this technique. A silica tube 40, typically in the range 15 to 25 mm external diameter and 1 to 3 mm wall thickness, is lowered through a ring heater 41 which softens the tip of the tube enabling it to be pulled into a fibre 42. The same reagents as were used in the example described above with reference to Figure 3 are also used in this reaction to deposit the first and second layers. These reagents are introduced into the tube 40 via a delivery pipe 43. The temperature required to soften the glass is also sufficient to promote the requisite chemical reaction of the reagents, and hence the second glass layer 44 is deposited which forms the central core 45 of the drawn fibre.
It is to be understood that the foregoing description of specific examples of this invention is made by way of example only and is not to be considered as a limitation on its scope.
Claims (12)
1. A method of making an optical fiber including the steps of:
heat treating the bore of a hollow silica glass tube under vacuum to remove moisture and prevent formation of oxygen-hydrogen compounds in the fiber;
coating the heat treated bore with a first silica glass layer in a hydrogen-free atmosphere;
coating a second silica layer on said first silica layer, said second silica layer having a higher refractive index than said first silica layer; and collapsing said tube and coated bore to form an optical fiber having a core and cladding layer, said core having a higher index of refraction than said cladding layer.
heat treating the bore of a hollow silica glass tube under vacuum to remove moisture and prevent formation of oxygen-hydrogen compounds in the fiber;
coating the heat treated bore with a first silica glass layer in a hydrogen-free atmosphere;
coating a second silica layer on said first silica layer, said second silica layer having a higher refractive index than said first silica layer; and collapsing said tube and coated bore to form an optical fiber having a core and cladding layer, said core having a higher index of refraction than said cladding layer.
2. The method of claim 1 wherein said first layer is of cladding glass, and including the step of coating the first layer with a second layer of silica glass of higher refractive index than the first layer in said hydrogen-free atmosphere, and collapsing the tube and bore so that said second layer forms the core of said fiber.
3. The method of claim 2 including depositing said first and second layers by R.F. excited vapor reaction in a hydrogen-free atmosphere.
4. The method of claim 3 wherein the first layer is deposited by a reaction involving oxygen and silicon tetrachloride and the second layer is deposited by a reaction further including titanium tetrachloride.
5. The method of claim 4 wherein the second layer is deposited simultaneously as the bore {s being collapsed and the tube is being drawn into a fiber.
6. The method of claim 5 wherein the tube is introduced into a hot zone to soften the tip for collapsing the bore and drawing into a fiber while the inside of the tube is maintained at a reduced pressure.
7. The method of claim 6 including flame polishing the bore of the hollow silica glass tube before heat treating.
8. The method of claim 7 including reducing residual pressure within said tube, and drawing the tube and coated bore to collapse the tube and bore to form said optical fiber.
9. The method of claim 4 including the steps of: attaching airtight enclosure members to both ends of said tube prior to heat treating; placing said tube proximate a heating element without exposing the bore of said tube to air; passing said silicon tetrachloride and said titanium tetrachloride through said enclosure members; and moving said tube relative to said heating element to provide a uniform coating along the length of said tube by thermal dissociation of said silicon tetrachloride and said titanium tetrachloride.
10. A method of making a solid structure for pulling into an optical fiber having an outer layer having a first index of refraction and a core having a higher index of refraction including the steps of: selecting a hollow silica glass tube having said first index of refraction; treating the bore of said tube to remove from said bore substantially all traces of moisture; sealing the ends of said bore; introducing a cladding material into said bore to form a cladding layer on the inside of said bore said cladding layer having an index of refraction which is the same as or slightly higher than said first index of refraction and is lower than the index of refraction of said core; introducing into said bore a core forming material having an index of refraction which is higher than the cladding index of refraction; coating said bore by depositing said core forming material thereon; heating said tube and deposited coating; and collapsing said tube cladding and coating so as to form a solid structure having an outer layer having said first index of refraction, a cladding layer having either said first index of refraction or a slightly higher index of refraction and surrounding a core having an index of refraction which is higher than either of said cladding layer or said outer layer.
11. The method of claim 10 which further includes the additional step of rotating said tube about its axis during the period of time when said cladding layer and said core layer are being deposited so as to uniformly coat the bore of said tube.
12. In a method of making an optical fiber, the steps of: heat treating the bore of a hollow silica glass tube under vacuum to remove moisture and prevent formation of oxygen-hydrogen compounds in the fiber; coating the heat treated bore with a first silica glass layer in a hydrogen-free atmosphere;
coating a second silica layer on said first silica layer, said second silica layer having a higher refractive index than said first silica layer; and collapsing said tube and coated bore to form a solid structure having a core and cladding layer, said core having a higher index of refraction than said cladding layer.
coating a second silica layer on said first silica layer, said second silica layer having a higher refractive index than said first silica layer; and collapsing said tube and coated bore to form a solid structure having a core and cladding layer, said core having a higher index of refraction than said cladding layer.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA314,701A CA1066570A (en) | 1972-06-08 | 1978-10-30 | Optical fibres |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB2677072A GB1427327A (en) | 1972-06-08 | 1972-06-08 | Glass optical fibres |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1054795A true CA1054795A (en) | 1979-05-22 |
Family
ID=10248922
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA172,817A Expired CA1054795A (en) | 1972-06-08 | 1973-05-31 | Optical fibres |
Country Status (9)
Country | Link |
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JP (2) | JPS539740B2 (en) |
AU (1) | AU475394B2 (en) |
CA (1) | CA1054795A (en) |
CH (1) | CH586165A5 (en) |
DE (2) | DE2328930C2 (en) |
ES (1) | ES415658A1 (en) |
GB (1) | GB1427327A (en) |
IT (1) | IT988974B (en) |
NL (1) | NL7307907A (en) |
Families Citing this family (37)
Publication number | Priority date | Publication date | Assignee | Title |
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JPS4983453A (en) * | 1972-12-14 | 1974-08-10 | ||
DE2463016C2 (en) * | 1973-08-21 | 1982-05-06 | International Standard Electric Corp., 10022 New York, N.Y. | Method of manufacturing a fiber optic light guide |
DE2402270C2 (en) * | 1974-01-18 | 1983-05-26 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Process for the internal coating of a quartz tube and device for carrying out the process |
CA1050833A (en) * | 1974-02-22 | 1979-03-20 | John B. Macchesney | Optical fiber fabrication involving homogeneous reaction within a moving hot zone |
US4217027A (en) | 1974-02-22 | 1980-08-12 | Bell Telephone Laboratories, Incorporated | Optical fiber fabrication and resulting product |
US4360250A (en) * | 1974-05-31 | 1982-11-23 | National Research Development Corp. | Optical waveguides |
DE2444100C3 (en) * | 1974-09-14 | 1979-04-12 | Philips Patentverwaltung Gmbh, 2000 Hamburg | Process for the production of internally coated glass tubes for drawing optical fibers |
JPS5174647A (en) * | 1974-12-24 | 1976-06-28 | Sumitomo Electric Industries | HIKARIDENSOYOFUAIBAASOZAINOSEIZOHOHO |
JPS51127743A (en) * | 1975-04-30 | 1976-11-08 | Nippon Telegr & Teleph Corp <Ntt> | Optical fiber and its manufacturing method |
JPS51138449A (en) * | 1975-05-26 | 1976-11-30 | Sumitomo Electric Ind Ltd | Light transmission fiber and method for fabricating the same |
CA1029993A (en) * | 1975-09-11 | 1978-04-25 | Frederick D. King | Optical fibre transmission line |
AU504423B2 (en) * | 1975-11-14 | 1979-10-11 | International Standard Electric Corporation | Optical fibre |
JPS5621777Y2 (en) * | 1976-02-04 | 1981-05-22 | ||
GB1578826A (en) * | 1976-03-25 | 1980-11-12 | Western Electric Co | Methods for fabricating optical fibre preforms |
GB1559097A (en) * | 1976-06-01 | 1980-01-16 | Standard Telephones Cables Ltd | Optical fibre manufacture |
DE2648702C3 (en) * | 1976-10-27 | 1980-08-21 | Jenaer Glaswerk Schott & Gen., 6500 Mainz | Infrared-permeable optical fiber made from oxygen-poor or oxygen-free GUs and process for their production |
JPS5395649A (en) * | 1977-02-02 | 1978-08-22 | Hitachi Ltd | Production of optical fiber |
CA1080562A (en) * | 1977-02-10 | 1980-07-01 | Frederick D. King | Method of and apparatus for manufacturing an optical fibre with plasma activated deposition in a tube |
JPS5413350A (en) * | 1977-07-02 | 1979-01-31 | Fujikura Ltd | Production of optical fiber |
US4334903A (en) | 1977-08-29 | 1982-06-15 | Bell Telephone Laboratories, Incorporated | Optical fiber fabrication |
JPS5748214Y2 (en) * | 1978-05-11 | 1982-10-22 | ||
GB1603949A (en) * | 1978-05-30 | 1981-12-02 | Standard Telephones Cables Ltd | Plasma deposit |
CA1128739A (en) * | 1978-06-08 | 1982-08-03 | Corning Glass Works | Method of making large diameter optical waveguide preforms |
DE2929166A1 (en) * | 1979-07-19 | 1981-01-29 | Philips Patentverwaltung | METHOD FOR THE PRODUCTION OF OPTICAL FIBERS |
US4425146A (en) * | 1979-12-17 | 1984-01-10 | Nippon Telegraph & Telephone Public Corporation | Method of making glass waveguide for optical circuit |
US4331462A (en) | 1980-04-25 | 1982-05-25 | Bell Telephone Laboratories, Incorporated | Optical fiber fabrication by a plasma generator |
DE3203349A1 (en) * | 1981-11-28 | 1983-06-09 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | METHOD AND DEVICE FOR PRODUCING AN OPTICAL GLASS FIBER WITH A LOW OH ION CONTENT |
JPS5883573U (en) * | 1981-12-03 | 1983-06-06 | ダイハツディーゼル機器 | Door closer stop device |
DE3206144A1 (en) * | 1982-02-20 | 1983-09-01 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | METHOD FOR PRODUCING A LIGHT WAVE GUIDE |
DE3206176A1 (en) * | 1982-02-20 | 1983-08-25 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Process for the production of a preform from which optical fibres can be drawn |
DE3206177A1 (en) * | 1982-02-20 | 1983-08-25 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Process for the production of a preform from which optical fibres can be drawn |
DE3222189A1 (en) * | 1982-06-12 | 1984-01-26 | Hans Dr.Rer.Nat. 5370 Kall Beerwald | Plasma process for coating the interior of tubes with dielectric material |
DE3302128A1 (en) * | 1983-01-22 | 1984-07-26 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Optical waveguide, and a process for the production thereof |
FR2543455B1 (en) * | 1983-03-30 | 1987-03-27 | Air Liquide | PROCESS FOR OPALIZING THE INTERIOR SURFACE OF OBJECTS OF LONG LENGTH IN RELATION TO THEIR SECTION |
CN1011227B (en) * | 1985-06-25 | 1991-01-16 | 占河电气工业有限公司 | Mfg. method for optics fibre |
DE3830364C1 (en) * | 1988-09-07 | 1990-01-18 | Schott Glaswerke, 6500 Mainz, De | |
DE3936006A1 (en) * | 1989-10-28 | 1991-05-02 | Rheydt Kabelwerk Ag | Low attenuation optical fibre preform - by internal tube coating, using low viscosity molten layer as first layer |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
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DE7202166U (en) * | 1972-05-04 | Heraeus Schott Quarzschmelze Gmbh | Optical fiber | |
BE438752A (en) * | 1939-04-22 | |||
DE1640559U (en) | 1949-07-07 | 1952-07-10 | Schloemann Ag | TRACTOR FOR ROLLED MATERIAL WITH ROPE-CONTROLLED TOWING PUMP. |
DE1085393B (en) * | 1956-02-11 | 1960-07-14 | Degussa | Process for depositing metal layers in pipes made of ceramic material |
US2967115A (en) * | 1958-07-25 | 1961-01-03 | Gen Electric | Method of depositing silicon on a silica coated substrate |
US3031338A (en) * | 1959-04-03 | 1962-04-24 | Alloyd Res Corp | Metal deposition process and apparatus |
US3127641A (en) * | 1961-10-05 | 1964-04-07 | Gen Electric | Tungsten tube manufacture |
NL128054C (en) * | 1963-01-29 | |||
GB1145630A (en) * | 1966-10-18 | 1969-03-19 | Standard Telephones Cables Ltd | Dielectric waveguide |
FR2002589A1 (en) * | 1968-02-26 | 1969-10-31 | Corning Glass Works | |
US3644607A (en) * | 1969-12-18 | 1972-02-22 | Texas Instruments Inc | Use of vapor phase deposition to make fused silica articles having titanium dioxide in the surface layer |
US3711262A (en) * | 1970-05-11 | 1973-01-16 | Corning Glass Works | Method of producing optical waveguide fibers |
US3737293A (en) * | 1972-01-03 | 1973-06-05 | Corning Glass Works | Method of forming an economic optical waveguide fiber |
-
1972
- 1972-06-08 GB GB2677072A patent/GB1427327A/en not_active Expired
-
1973
- 1973-05-31 CA CA172,817A patent/CA1054795A/en not_active Expired
- 1973-06-06 DE DE2328930A patent/DE2328930C2/en not_active Expired
- 1973-06-06 NL NL7307907A patent/NL7307907A/xx active Search and Examination
- 1973-06-06 DE DE2366295A patent/DE2366295C2/en not_active Expired
- 1973-06-06 AU AU56577/73A patent/AU475394B2/en not_active Expired
- 1973-06-07 CH CH823273A patent/CH586165A5/xx not_active IP Right Cessation
- 1973-06-07 ES ES415658A patent/ES415658A1/en not_active Expired
- 1973-06-08 JP JP6459573A patent/JPS539740B2/ja not_active Expired
- 1973-06-12 IT IT25115/73A patent/IT988974B/en active
-
1979
- 1979-04-19 JP JP4851479A patent/JPS54151633A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
GB1427327A (en) | 1976-03-10 |
AU475394B2 (en) | 1976-08-19 |
JPS4964447A (en) | 1974-06-21 |
ES415658A1 (en) | 1976-06-16 |
IT988974B (en) | 1975-04-30 |
NL7307907A (en) | 1973-12-11 |
JPS54151633A (en) | 1979-11-29 |
DE2328930C2 (en) | 1982-05-13 |
JPS539740B2 (en) | 1978-04-07 |
CH586165A5 (en) | 1977-03-31 |
AU5657773A (en) | 1974-12-12 |
DE2328930A1 (en) | 1974-01-03 |
DE2366295C2 (en) | 1982-05-13 |
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