GB2134897A - Manufacture of optical fibres and preforms with reduced hydroxyl content - Google Patents
Manufacture of optical fibres and preforms with reduced hydroxyl content Download PDFInfo
- Publication number
- GB2134897A GB2134897A GB08403171A GB8403171A GB2134897A GB 2134897 A GB2134897 A GB 2134897A GB 08403171 A GB08403171 A GB 08403171A GB 8403171 A GB8403171 A GB 8403171A GB 2134897 A GB2134897 A GB 2134897A
- Authority
- GB
- United Kingdom
- Prior art keywords
- preform
- gas
- process according
- carbon
- glass
- 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
Links
Classifications
-
- 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
-
- 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
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Manufacture, Treatment Of Glass Fibers (AREA)
- Light Guides In General And Applications Therefor (AREA)
- Glass Melting And Manufacturing (AREA)
Abstract
During optical fibre or preform fabrication, the glass is treated while hot with a gas comprising a carbon tetrahalide (preferably CCl4 with, optionally, CBrCl3 and/or CCl2Br2) to remove hydroxyl entities. The gas may be introduced, for example into central void 10 of a preform tube undergoing collapse, and may include a dopant compensator e.g. GeCl4. <IMAGE>
Description
SPECIFICATION
Process for making optical fibers
This invention relates to the procedures employed in the manufacture of glass optical fibers.
In the manufacture of optical fibers, a glass preform, which is a selectively doped glass tube, is fabricated by a process such as MCVD (modified chemical vapor deposition), MCVD performed with a plasma, or PCVD described by D. Kuppers et al., in the Journal of the Electrochemical Society, 423, 1079 (1 976). The preform is either constricted or sealed on one end, collapsed into a solid body, and simultaneously with the collapse or subsequently after the collapse, an optical fiber is drawn from the solid body. Bound OH moieties in the preform and in the resulting fiber absorb in the wavelength region typically employed in optical communication systems and substantially increase the signal loss in such systems.Thus, during the formation of the preform great care is taken to substantially exclude the incorporation of OH moieties, e.g., SiOH, into the preform. Generally, the predominant source of OH moieties involves hydrogen-containing entities which at the collapse temperature are typically converted to water. The water, in turn, reacts with the preform to produce bound OH moieties. Thus, to maintain the quality of the fiber ultimately produced, substantial measures are also taken during preform collapse to exclude hydrogen-containing entities.
One predorninant method has been employed to prevent the incorporation of OH moieties during preform collapse. In this procedure described by
K. K. Walker et al., "Reduction of Hydroxyl
Contamination In Optical Fiber Preforms," Third
International Conference on Integrated Optics and
Optical Fiber Communications, San Francisco,
California, April 27-29,1981 (New York: IEEE, 1981) WA4, 86-88 (1981), molecular chlorine is introduced during the collapse procedure. The chlorine generally reacts with water, e.g., water formed from hydrogen-containing entities, to produce hydrogen chloride through the reaction H2O + Cl2 = 2HCI + 1/202. (1)
The resulting HCI is not incorporated into the preform and is removed in the effluent.This molecular chlorine collapse procedure has been found to produce fibers with relatively low losses due to OH absorption -- losses generally in the range 0.3 te 2 dB/km at the OH absorption peak wavelength of 1.39 ,um. Nevertheless, it is certainly advantageous despite the acceptable level of loss already achieved, to substantially decrease loss to even more desirable levels.
According to the present invention there is provided a process for fabricating a glass optical preform or fiber from a glass body, said process comprising the steps of providing a gas to the environment oF said body, said gas being chosen to lirnit the presence of OH entities in said glass body, heating said glass body to an elevated temperature, and modifying said glass body through said heating, wherein said gas comprises a carbon tetrahalide.
The loss produced due to incorporation of OH moieties is substantially decreased in the embodiment of the invention as compared to other techniques, through the introduction of carbon tetrahalide compounds, such as carbon tetrachloride, into the environment of a glass body being modified for ultimate use in fabricating glass optical fibers, e.g., into the embodiment of a preform environment being collapsed. In particular, OH absorption losses as low as 0.05 dB/km at 1.39 ym have been achieved. Thus, through the use of the inventive technique, it is possible to improve significantly the quality of the fiber ultimately produced as compared to that obtainable utilizing gases such as molecular chlorine.
Grief Description of the Drawing
The Figure is illustrative of an embodiment of the inventive technique.
The loss produced by OH moieties in optical fibers is significantly reduced if a carbon tetrahalide based composition, i.e., carbon tetrachloride. CBrCl3, CBr2CI2, or mixtures of these compounds, is introduced into the environment of a glass body being modified either physically or chemicaily. Specifically, the inventive addition of carbon tetrahalide compounds is useful for reducing OH incorporation during a variety of processes involving modification of a glass body, e.g., alteration of physical form such as during the preform collapse process and chemical modification such as during the preform fabrication process. In either case the presence of a carbon tetrahalide during modification of a glass body produces a very low level of loss in the fiber ultimately fabricated from this body.Although the inventive technique is generally applicable to procedures involving modification of glass bodies in processes leading to fiber manufacture, this disclosure employs the preform collapse procedure as a pedagogic vehicle to delineate the parameters invoived in the inventive technique.
Nevertheless, the same parameters are applicable to other glass body modification procedures.
The desired carbon tetrahalide composition is introduced into the glass body environment, e.g., into the internal void, 10, of the preform tube during collapse. (The internal void is advantageously chosen since in most collapse processes the internal glass region forms the light guiding region where it is most critical to limit OH entities.) It is most desirable to use carbon tetrachloride (generally, but not necessarily, with a carrier gas) as the carbon tetrahalide based composition.The carbon tetrahalide composition is easily introduced into the environment of the preform by conventional expedients such as by passing a carrier gas through a bubbler containing the desired carbon tetrahalide composition and then flowing the carrier gas with its carbon tetrahalide composition into the preform environment. (When a combination of CCI4, CBrCI3 and/or CBr2CI2 is desired, the composition is produced by combining gas flows from separate bubblers or by using a bubbler containing all of the constituents. In the former case, the mole fraction of each component introduced depends on the individual gas flow rates through each bubbler and the bubbler temperature. In the latter case, the mole fraction of each material in the gas phase depends on, but is not equivalent to, its corresponding mole fraction in the bubbler and on the bubbler temperature.In either situation, a control sample is easily employed to determine the appropriate conditions to yield the desired ratio in the final gas flow.) Although the use of CBrCla and CBr2CI2 each separately or in combination is not precluded, it is more desirable to employ these carbon tetrahalides (if at all) in combination with Cm14. A contemplated explanation for this result is that HBr (the reaction product of a bromine-containing compound with water) is less stable than HCI. This relative instability of HBr necessitates the use of somewhat high concentrations of the halogen contributing species to achieve equivalent results.
The concentration of the carbon tetrahalide compound employed to scavenge hydrogencontaining entities in the preform collapse process affects other processes which are also in some situations used during the preform collapse process. For example, it is desirable at times to introduce a dopant compensator, e.g., germanium tetrachloride, together with oxygen into the preform environment during collapse. The oxygen reacts with the GeCI4 to maintain the desired GeO2 concentration at the inner surface of the preform.
If this procedure is employed, the halogen liberated from both the germanium tetrahalide and carbon tetrahalide affects the concentration of
GeO2 through the chemical equilibrium of the reaction represented by the following equation:
GeX4 + 2 GeO, + 2X2 (2) (X is a halogen). Therefore, if dopant compensation is to be utilized in conjunction with a carbon tetrahalide, the resulting equilibrium shift should be overcome by a corresponding increase in the amount of germanium tetrahalide composition which is employed.
Similarly, processes which produce 1) substantial halogen from a source other than a carbon or 2) oxygen in the preform environment, also have a potential effect on the equilibrium shown in equation (1) and thus, in turn, affect the amount of carbon tetrahalide required to remove the desired amount of water. For example, if oxygen is introduced, e.g., as a carrier gas, the equilibrium (equation (1)) is shifted toward the left.
side. Thus, the minimum amount of carbon tetrahalide required (for a given amount of hydrogen-containing entity) to avoid substantial
OH presence in the fiber increases with the increasing presence of oxygen. (In contrast, a gas such as helium or other inert gas has little effect.)
If halogen from sources other than carbon tetrahalides is also present, less carbon tetrahalide is needed. Although temperatures often affect equilibrium considerations. the temperature employed during preform collapse, e.g., 2000 to 2200 degrees C, has no substantial affect on the required level of carbon tetrahalide and, thus, on the level of OH absorption in the fiber formed from a preform produced using a carbon tetrahalide.
Generally, the inventive process is not employed as a gross removal procedure for hydrogen-containing entities. Other precautions, such as purification of reactant material, are utilized to substantially reduce the level of the hydrogen-containing entities. For this reason, sufficient carbon tetrachloride, even in the presence of oxygen, is easily introduced to prevent the losses associated with the levels of hydrogencontaining entities present after these precautions are taken. (Generally, 1 to 10 ppm by weight of contaminating hydrogen, however bound, is present.) Nevertheless, as discussed previously, oxygen affects the minimum amount of carbon tetrachloride required for a given level of hydrogen-containing entity. Oxygen is generally present during collapse, at levels up to 0.1 atm, even if not purposely introduced.For such levels of oxygen, desirable results are obtained for typical hydrogen entity levels when a partial pressure of 0.015 atm or greater of carbon tetrachloride is introduced into the glass body environment. If oxygen is purposely introduced and thus the oxygen level is above 0.1 atm, it is typically desirable to maintain the fraction P1/22/Pcc,4 at levels below 20. (Po2 and PCCI4 are the partial pressures of 02 and introduced CCI4, respectively.)
When lower than usual hydrogen entity levels are present (less than 1 ppm) or when less than substantially total removal is acceptable, then a correspondingly smaller amount of carbon tetrahalide or Pol22/pCcl4 is employed. (In processes other than NCVD preform collapse, it is possible that a background of less than 0.1 atm of oxygen is present. For such cases, a correspondingly lower level of carbon tetrahalide introduction also produces desirable results.) A control sample is used to determine the precise amount of carbon tetrahalide necessary to yield the desired level of OH attenuation.
The presence of sources of oxygen and sources of halogen other than carbon tetrahalides are the primary influences introduced by processes not directly related to the inventive process. However, it is possible that other materials might be introduced for purposes outside the inventive process which might affect the reaction equilibrium between water (the composition resulting from hydrogen-containing entities) and the carbon tetrahalide composition, and thus which would require adjustment of the parameters employed in the inventive process. A control sample is easily employed to determine the corrections appropriate for each particular situation.
Irrespective of the previously discussed considerations, certain precautions should be taken. In the case of CCI4 use, it is generally desirable to limit the chlorine concentration expressed as molecular chlorine in the preform environment to less than 0.3 atm. Above these levels, the high concentration of chlorine tends to form bubbles in the preform and thus produce unacceptably high losses. Additionally, oxygen in the presence of carbon tetrahalides tends to avoid carbon deposits and induces the formation of gases such as carbon dioxide, carbon monoxide, and under some conditions, phosgene. The carbon tetrahalide material should also not have an excessive hydrogen-containing entity impurity level, i.e., a level greater than 40 ppm expressed as weight fraction of H.Thus, the carbon tetrahalide composition with hydrogen levels greater than 40 ppm should preferably be purified by conventional techniques such as photochlorination and sweeping with a dry inert gas to remove PX (X = Cl or Br) and H2O.
Purification which produces less than 6 ppm is preferred. (Extended photochlorination of CBrCI3 and CBr2CI2, if necessary to obtain the desired purity level, converts some of the bound Br to Cl.
However, the resulting carbon tetrahalides, as previously discussed, are quite acceptable for use in the inventive process.)
The following examples are illustrative of the subject invention.
EXAMPLE 1
Preforms produced by the MCVD process as described by S. R. Nagel et al., in IEEE Journal of
Ouantum Electronics, OE-18(4), 459-476 (1982) were employed. These preforms were first sealed at one end and then collapsed by repeated longitudinal traverses with a torch, 20, maintained at a temperature between 2000 and 2200 degrees C. Before one end of the preform was sealed, a gas flow of 330 cc per minute of oxygen was passed through a carbon tetrachloride bubbler maintained at a temperature of 40 degrees C. This CCI4 containing gas flow was combined with a second 1000 cc per minute flow of oxygen. The combined gas flow was introduced at one end of the preform, 25, and was maintained for a time sufficient to purge the tube. The end of the preform opposite the point of gas introduction was then sealed.The gas flow during sealing was gradually reduced to avoid a substantial pressure increase in the preform. This gradual decrease led to a flow rate of oxygen through the bubbier of 25 cc per minute and a secondary oxygen flow rate of 75 cc per minute. The torch was traversed across the length of the preform at rates varying from 6 to 10 cm per minute. During each pass the pressure in the tube was regulated by either controlling the escape, 1 5, from the preform of the gas geing introduced or the rate of introduction of the combined gas flow. The pressure through these expedients was regulated to avoid excessively rapid collapse but to allow total collapse to occur after approximately 5 to 7 passes. A fiber was then drawn from the preform by a standard technique such as that described by
L. L. Blyler, Jr. et al., in Proceedings of IEEE, 68, 1194-1198 (1980).The loss in the resulting fiber was measured through a procedure described in Chapter 11, Optical Fiber
Telecommunications, ed. by S. E. Miller et al.,
Academic Press (1979). The resulting fibers showed OH absorption losses of 0.05 dB/km to 0.1 dB/km at 1.39 ,um.
EXAMPLE 2
The same procedure as described in Example 1 was performed except that the preform was not initially sealed. As described in Example 1, the initial flow rate of oxygen through the bubbler was 330 cc per minute and the second oxygen flow was 1000 cc per minute. This ratio of flow rates between the carbon tetrachloride laden oxygen and the oxygen free from carbon tetrachloride was maintained. However, the combined total flow rate was decreased at a rate which allowed total collapse to occur in 7 passes. The resulting fibers showed OH absorption losses of 0.05 dB/k.m to 0.1 dB/km at 1.39 dum.
EXAMPLE 3
The procedure of Example 2 was followed except germanium tetrachloride was introduced simultaneously into the preform environment. This introduction was accomplished by passing oxygen at a rate of 1 5 cc per minute through a germanium tetrachloride bubbler held at a temperature of 40 degrees C. The flow rate through the germanium tetrachloride bubbler was not substantially changed through the entire collapse procedure.
The resulting fiber had a measured OH absorption loss of approximately 0.1 dB/km of 1.39 ym.
Claims (11)
1. A process for fabricating a glass optical preform or fiber from a glass body, said process comprising the steps of providing a gas to the environment of said body, said gas being chosen to limit the presence of OH entities in said glass body, heating said glass body to an elevated temperature, and modifying said glass body through said heating, wherein said gas comprises a carbon tetrahalide.
2. The process according to claim 1, wherein said carbon tetrahalide comprises at least one of carbon tetrachloride, CCI2Br2 and CCI3Br.
3. The process according to claim 1 or 2, wherein said liquid comprises carbon tetrachloride and at least one of CCI2Br2 and CCI3Br.
4. The process according to claim 1 or 2 or 3, wherein said carrier gas comprises oxygen.
5. The process according to any one of preceding claims 1-4, wherein said gas includes
GeCI4.
6. The process according to any one of preceding claims 1-5, wherein gas is provided to a void in the body by bubbling a carrier gas through a liquid.
7. The process according to any one of preceding claims 1-6, wherein said modification comprises collapsing the body to form the glass preform.
8. The process according to claim 7, including the step of drawing said fiber from said collapsed body.
9. The process according to any one of preceding claims 1-8, wherein said elevated temperature is in the range 2000 to 2200 degrees C.
10. A process for fabricating a glass optical preform or fiber, substantially as hereinbefore described with reference to any one of the
Examples.
11. A glass optical preform or fiber fabricated by the process according to any one of the preceding claims.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46629383A | 1983-02-14 | 1983-02-14 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8403171D0 GB8403171D0 (en) | 1984-03-14 |
| GB2134897A true GB2134897A (en) | 1984-08-22 |
| GB2134897B GB2134897B (en) | 1986-12-17 |
Family
ID=23851229
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08403171A Expired GB2134897B (en) | 1983-02-14 | 1984-02-07 | Manufacture of optical fibres and preforms with reduced hydroxyl content |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS59156931A (en) |
| DE (1) | DE3404781A1 (en) |
| FR (1) | FR2540997B1 (en) |
| GB (1) | GB2134897B (en) |
| NL (1) | NL8400455A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1986007347A1 (en) * | 1985-06-05 | 1986-12-18 | Hughes Aircraft Company | Method of fabricating optical fiber preforms having reduced susceptibility to radiation damage |
| EP2535318A3 (en) * | 2011-06-17 | 2013-09-11 | Draka Comteq B.V. | Device and method for manufacturing a preform of an optical glass fiber |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3733880A1 (en) * | 1987-10-07 | 1989-04-20 | Schott Glaswerke | METHOD FOR PRODUCING A LIGHT WAVE GUIDE |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB822868A (en) * | 1956-11-19 | 1959-11-04 | Corning Glass Works | Method of removing dissolved water from porous 96% silica glass |
| GB1492920A (en) * | 1975-08-16 | 1977-11-23 | Heraeus Schott Quarzschmelze | Manufacture of synthetic transparent fused silica |
| GB1497215A (en) * | 1974-04-22 | 1978-01-05 | Corning Glass Works | Forming glass bodies by flame hydrolysis |
| GB2084988A (en) * | 1980-10-02 | 1982-04-21 | Post Office | Methods of Etching Materials Containing Silicon |
-
1984
- 1984-02-06 FR FR8401760A patent/FR2540997B1/en not_active Expired
- 1984-02-07 GB GB08403171A patent/GB2134897B/en not_active Expired
- 1984-02-10 DE DE19843404781 patent/DE3404781A1/en not_active Withdrawn
- 1984-02-13 NL NL8400455A patent/NL8400455A/en not_active Application Discontinuation
- 1984-02-14 JP JP2454584A patent/JPS59156931A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB822868A (en) * | 1956-11-19 | 1959-11-04 | Corning Glass Works | Method of removing dissolved water from porous 96% silica glass |
| GB1497215A (en) * | 1974-04-22 | 1978-01-05 | Corning Glass Works | Forming glass bodies by flame hydrolysis |
| GB1492920A (en) * | 1975-08-16 | 1977-11-23 | Heraeus Schott Quarzschmelze | Manufacture of synthetic transparent fused silica |
| GB2084988A (en) * | 1980-10-02 | 1982-04-21 | Post Office | Methods of Etching Materials Containing Silicon |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1986007347A1 (en) * | 1985-06-05 | 1986-12-18 | Hughes Aircraft Company | Method of fabricating optical fiber preforms having reduced susceptibility to radiation damage |
| EP2535318A3 (en) * | 2011-06-17 | 2013-09-11 | Draka Comteq B.V. | Device and method for manufacturing a preform of an optical glass fiber |
Also Published As
| Publication number | Publication date |
|---|---|
| NL8400455A (en) | 1984-09-03 |
| JPS59156931A (en) | 1984-09-06 |
| FR2540997A1 (en) | 1984-08-17 |
| DE3404781A1 (en) | 1984-08-16 |
| GB2134897B (en) | 1986-12-17 |
| FR2540997B1 (en) | 1987-02-27 |
| GB8403171D0 (en) | 1984-03-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4125388A (en) | Method of making optical waveguides | |
| CA2056271C (en) | Uv light-permeable glass and article comprising the same | |
| US4668263A (en) | Method for producing glass preform for optical fiber | |
| KR20050031110A (en) | Low loss optical fiber and method for making same | |
| EP0196671A1 (en) | Method of producing glass preform for optical fiber | |
| JPH1053423A (en) | Production of synthetic silica glass | |
| EP0177040B1 (en) | Method for producing glass preform for optical fiber | |
| US4335934A (en) | Single mode fibre and method of making | |
| US4842626A (en) | Process for making optical fibers | |
| US5022904A (en) | Method of making optical glass article | |
| EP0164103A2 (en) | Method for producing glass preform for optical fiber containing fluorine in cladding | |
| GB2134897A (en) | Manufacture of optical fibres and preforms with reduced hydroxyl content | |
| US20020108404A1 (en) | Drying agent and improved process for drying soot preforms | |
| EP0164127B1 (en) | Method for producing glass preform for optical fibers | |
| US4655808A (en) | Method for producing glass preform for optical fiber | |
| US20050244119A1 (en) | Method of manufacturing fluorine doped silica glass article, and method of manufacturing optical fiber preform and optical fiber using the method, and optical fiber made by such method | |
| US4539033A (en) | Method for drying oxide glasses | |
| JP2005206452A (en) | Method of manufacturing fluorine-added silica glass body, optical fiber preform, method of manufacturing optical fiber and optical fiber | |
| FI79084B (en) | FOERFARANDE FOER FRAMSTAELLNING AV EN RIKTAD AEROSOLSTROEM. | |
| US20130291602A1 (en) | Optical fiber preform manufacturing method | |
| JPS6289B2 (en) | ||
| EP0185975A1 (en) | Process for fabricating a glass preform | |
| JPS60239339A (en) | Preparation of parent material for optical fiber | |
| KR940007219B1 (en) | Uv light-permeable glass and article comprising the same | |
| JPS6120491B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20020207 |