CA1084534A - Method of producing glass compositions for optical wave guides - Google Patents
Method of producing glass compositions for optical wave guidesInfo
- Publication number
- CA1084534A CA1084534A CA287,390A CA287390A CA1084534A CA 1084534 A CA1084534 A CA 1084534A CA 287390 A CA287390 A CA 287390A CA 1084534 A CA1084534 A CA 1084534A
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- glass
- content
- composing
- atoms
- silica
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C13/00—Fibre or filament compositions
- C03C13/04—Fibre optics, e.g. core and clad fibre compositions
- C03C13/045—Silica-containing oxide glass compositions
- C03C13/047—Silica-containing oxide glass compositions containing deuterium
-
- 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
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
- C03C1/02—Pretreated ingredients
-
- 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
- C03B2201/22—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with deuterium
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Optics & Photonics (AREA)
- Physics & Mathematics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Glass Compositions (AREA)
- Manufacture, Treatment Of Glass Fibers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Glass compositions suitable for optical waveguides which have the structural characteristics of O-H content type glass consist of a glass-composing oxide compound containing O-D groups. The glass compound consists primarily of one or more of the compounds SiO2, B2O3, GeO2, P2O5, SnO2, TiO2, Al2O3 and ZrO2 and the O-D groups.
This O-D content glass may be produced in a chemical vapor deposition,process by a hydrolysis reaction of D2O with one or more aprotic compound of glass-composing-atoms, or by the oxidation reaction of one or more deuterium compounds of glass-composing-atoms.
Glass compositions suitable for optical waveguides which have the structural characteristics of O-H content type glass consist of a glass-composing oxide compound containing O-D groups. The glass compound consists primarily of one or more of the compounds SiO2, B2O3, GeO2, P2O5, SnO2, TiO2, Al2O3 and ZrO2 and the O-D groups.
This O-D content glass may be produced in a chemical vapor deposition,process by a hydrolysis reaction of D2O with one or more aprotic compound of glass-composing-atoms, or by the oxidation reaction of one or more deuterium compounds of glass-composing-atoms.
Description
~` ~084S34 , . , BACKGROUND OF l'HE I~VENTION
This invention is directed to optical waveguides and in particular to glass fiber optical waveguides having low-loss characteristics in the infrared wavelength region at about 0.9 ~m.
A glass fiber optical waveguide is primarily composed of core and cladding. The core, which is the central portion of a glass fiber in the cross-section, has . - , . . .
either uniform or non-uniform refractive index distribution across the core. The electromagnetic wave is transmitted mainly in the core. The cladding, which is the outer portion of the glass fiber in the cross-section, has a lower refractive index than that of core material. The cladding in the glass fiber guides the electromagnetic wave.
In order to obtain low-loss optical waveguides it is important to use highly pure glass materials, especially in the core of glass fibers, because attenuation of light in the optical waveguides arises from the absorption of light by impurities in the glass materials as well as the light scattering by the spatial fluctuation of refractive index in the optical waveguides.
Intrinsically, fused silica is one of the best materials for the core or the cladding because both scattering loss and absorption loss of fused silica can be made very low. Other materials which are suited for low-loss optical waveguide production are high-silica-content glasses. The high-silica-content glasses normally contain SiO2 at more than 80 wt.~. High-silica-content glasses which contain B2O3 as an additive are useful as cladding materials of fused-silica core fibers. This type of glass-fiber 11 ' .
'. ~
-`" 1(1~4S3~
optical wa~;eguide has been described by D. Kato in the publication "Fused-silica~cGre glass fiber as a low-loss optical waveguide", Applied Physics Letters, Vol. 22, No. 1, pp. 3-4 (1973) and in U.K. Patent 1,435,523 to the Agency of Industrial Science and Technology and published on May 12, 1976. Materials which are suited for the cores of fused-silica-cladding glass fibers are high-silica-content glasses with additives such as TiO2, A1203, P205 and GeO2.
The latter type of glass fiber optical waveguide has been described by R.D. Maurer and P.C. Schultz in U.S. Patent 3,659,915, issued May 2, 1972. Refractive index of the high-silica-content glasses can be adjusted by selecting additive materials and controlling the contents.
Fused silica, which is also sometimes called fused quartz, is produced in conventioanl industrial process by fusing natural silica or quartz powder after a crushing and cleaning process. Other glasses are conventional~y made by melting mixed materials. Conventional fused silica as well as high-silica-content glasses are, however, not always useful at least as core materials for low-loss optical waveguides because these glasses still contain high levels of impurities such as transition metal ions.
Highly pure fused silica or high-silica-content glasses are conventionally produced by employing chemical reaction processes, which is called chemical vapor deposition (CVD). Chemical starting materials such as SiC14, Sill4, BC13, B2H4, GeC]3, POC13 can be highly purified by multiple-stage distillation because these materials can be vaporized at specific temperatures and pressures. It is noted, that their oxides such as SiO2, on the other harld, ' ' can not be purified by the distillation.
For the production of highly pure fused silica and high-silica-content glasses by the CVD process the - following chemical reactions have been used wherein the ,' starting materials or reactants are highly pure:
SiC14 + 2 ~ SiO2 + C12 (1) 4 22 ~-~ SiO2 + 2H2O (2) 2BC13 + 32 ~---~ 23 + 3C12 (3) SiC14 + 2H2 + 2 ) SiO2 etc.
Similar reactions are used for other compounds of glass-composing atoms. The reactions (1) to (3) are direct oxidation reactions, and the reaction (4) is known as flame ' hydrolysis because it ta};es place in an oxygen-hydrogen -flame.
Reactions such as (1) and (3) are called O~
free processes with which water-free glass materials can be produced. ',mall amount of water contained in glasses produced by the reaction (2) or (4) has a broad optical absorption spectrum of an O-H fundamental vibrational mode in infrared wavelength region at about 2.7 ~m. The broadening of the spectrum arises from the inhomogeneity of the environments of the bonds. The overtone absorption spectra appear in shorter wavelength regions, and are obstructive of low-attenuation light transmission in an important spectral region in which both sensitivity of Si diode-detector,devices and the emission spectrum of GaAlAs or GaAs diode light-source devices are available. Therefore, better attenuation characteristics in low-loss optical waveguides have been obtained by reducing or eliminating O-H
, .:
53~
content by the use of O-H free reactions. The elimination of O-H content by an O-H free CVD process, however, requires a higher temperature for oxidation to take place and yields a low deposition rate with the result that such O-H free method is rather costly. It has been found that O-H free fused silica or high-silica-content glasses are harder than O-H content glasses. The 0-H free glasses are also known to have an induced absorption spectrum that arises after some processing of the glass such as fiber drawing. These observed phenomena show that the content of small amount of silanol, i.e. Si-o-H, is important in the relaxation of local structure in glasses and thus in reducing local strains.
Solid products such as SiO2, B2O3 and GeO2 in reactions (1) to (4) are deposited onto a substrate.
Gaseous products such as C12, H2O and HCl as well as a part of fed starting gases are then taken away from the reaction region. Thus, highly pure fused silica or high-silica-content glasses are produced under contamination free circumstances. The CVD process was first applied to the production of g]ass and was described by M.E. Nordberg in U.S. Patent 2,326,039 which issued on August 3, 1943.
Reactions such as (1) and (3) produce glasses which do not contain water, i.e. O-H free. Other reactions such as (2) and (4) produce glass containing a small amount of water mainly in the form of silanol, i.e. -Si-o-H. The latter ~lasses are called O-I-I content glasses in contrast to O-H
free glasses~ U.S Patent 3,971,714 which issued to Maurer on February 12, 1974, describes a flame hydro1ysis glass producirg process wherein the startincJ material H2 is replaced by ~2 to produce a lo~ hydrox-71 ion content glass.
~s--108~534 This process however has the disadvantages that it requires D2, the isotope of H2 in the free state and that it takes place at a high temperature, i.e. in the order of 2000C, this increases the risk of product impurities due to the torch nozzle.
There are various ways for the fabrication of glass fibers. In the first method, a highly pure glass rod and a tubing either or both of which are the products of the CVD processes are fused to each other. This composite glass is called as a preform. The preform is then drawn into fibers. An examp]e of this method was described in the publication by D. Kato, and British Patent 1,435,523 mentioned above. In the second method, the CVD process is applied to form core and/or cladding glasses inside a tube substrate. Examples of the second type of method for the production of preforms were described by D.B. Keck and - -~-P.C. Schultz in U.S. Patent 3,711,262 which issed on January 16, 1973. In a third way, the CVD process is applied to form the cladding glass onto a rod substrate which is also a product of CVD process. An example of the third way for the production of a preform was described by D.B. Keck and R.D. Maurer in U.S. Patent 3,775,075 which issued on November 27, 1973. These preforms are softened at one end and then drawn into a thin glass fiber.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a glass composition suitable for optical waveguides having the structural characteristics of O-H content glasses.
It is a further object of this invention to provide a glass composition suitable for optical waveguides - : ~ . : --)134S34 ~' which does not have a s~rong optical absorption spectrum ~; of an o-~ overtone vibrational mode in infrared wave-length region at about 0.9 ~m.
It is another object of this invention to provide processes for producing O-H free glass having the structural characteristlcs of O-H content glass.
These and other objects are achieved in accordance with the present invention by a glass composition suitable for optical waveguides consisting of a glass-composing oxide compound containing O-D groups. This composition provides an O-H content type glass wherein the presence of a number of O-H groups are substituted by O-D groups. The O-D
groups may be in the form of -Si-o-D , and the glass-composing oxide compound may be one or more of the compounds selected from the group consisting of SiO2, B2O3, GeO2~ P2O5, SnO2~ TiO2~ A12O3 and ZrO2.
The chemical vapor deposition process is used to produce the O-D content glass either by a hydrolysis reaction of D2O with an aprotic compouncl of glass-compo~ing-atoms or by the oxidation of a deuterium compound of glass-composing-atoms. The glass may then be stabilized by fire polishlng it with a hydrogen-ox~yen flame.
Glass fiber optical waveguides may be produced having a core made of O-D content glass or both a core and a cladding made of O-D content glass.
~RIEF DESCRIPTION OF THE D~AWINGS
In the drawings:
Figure 1 is a schematic diagram of a chemical vapor deposition apparatus for proclucing O-D content glass;
3p Figure 2 is a cross-sectioral view of a preform .
. :
10~4534 for a glass fiber optical waveguidei and Figure 3 is a cross-sectional view of a glass fiber optical waveguide.
DESCRIPTION OF PREFERRED EMBODI~ENTS
In order to overcome the disadvantages encountered in conventional O-H fr~e glass fiber optical waveguides in terms of its optical transmission characteristics while at the same time maintaining the advantages of an O-H content type of glass, the glass compound in accordance with the present invention from which glass fiber optical waveguides are formed, are made to contain small amounts of the hydrogen isotope (D) as an O-D group in a process other than the flame hydrolysis deposition process.
The O-D content glass materials is produced most effectively by the use of chemical vapor deposition (CVD) techniques. In accordance with the present invention, however, isotopic starting materials are used in the CVD
process. In acldition, it is found that the use of heavy water, i.e. D2O, is a preferable isotopic starting material for the production of O-D content glasses because it is economical. Heavy water is available at a lower price than other isotopic compounds because it is a primary product and is obtained in a mass enrichment process for natural-uranium heavy-water nuclear reactors such as CANDU
in Canada.
As a first embodiment of the me-thod of producing O-D content glass in accordance with the present invention, the following are examp]es of CVD reaction schemes which can .
, ~; - 1084534 be emploved:
SiCl4 + 2D20 -~ SiO2 + 4DCl (5) 3 + 3D2O ~ B2O3 + 6DCl (6) GeC14 + 2D20---~ GeO2 + 4DC1 (7) where D is an isotope of hydrogen. These reaction schemes as given in (5) to (7)lcan proceed without necessity of heat and at lower temperatures than direct oxidations, and may be called cold hydrolysis reactions. Materials in the , lefthand side of reactions t5) to (7) can be transported in certain carrier gases such as Ar when they are in liquid state at a given temperature. Reaction schemes (5) to (7) ' are essentially reactions between aprotic compounds of glass-composing atoms and heavy water. Other compounds such as POC13, TiCl4, AlCl3, SnCl4 and ZrCl4;can also be used , in similar CVD xeaction schemes to obtain different glass compositions in accordance with the present invention.
The isotopic starting material need not however be limited to D2O. As a second em~odiment oE the method of producing O-D content glass.in accordance with this invention, the following are examples of other CVD reaction schemes which can be employed:
SiD4 + 2O2 --~ SiO2 + 2D2O (8) GeD4 + 202---~ GeO2 + 2D2o (9) B2D6 + 32 ~~~~ B203 + 3D20 (10) These reaction schemes are essentially oxidation reactions of deuterium compounds of glass-composing-atorns. Other deuterium compounds of glass-composing-atoms such as SnD4 can also be used in the simil?.r oxidation reaction schemes. This second ernbodiment of the .:
-` 10~4S39~
present invention for the fabrication method would be useful if the deuteration of compounds of glass-composing-atoms were performed economically. Although deuterium compounds of glass-composing atoms are presently rather expensive J the cost could be lowered if the deuteration processes are optimumly industrialized. Under such circumstance this second method may be superior to the first method because carrier gases of heavy water vapor and the aprotic compounds vapor which are necessary in the first method are not always needed in the second method. Heavy water solutions of compounds of glass-composing atoms such as D3PO4 can also be used, if it is necessary for the modification of glass properties, by transporting the mixed vapor by the use of carrier gas in the second method.
The glass layer or layers resulting from bo-th of the above methods, undergoes a normal structure relaxation over a period of time wherein trapped vapor of the starting materials such as D2O are released. ~his relaxation process may be accelerated by fire polishing the glass layer or layers using a hydrogen-oXygen :Elame.
Figure 1 is a schematic diagram of C~D apparatus for producing O-D content glass using D2O as a starting material. The starting materials SiCl~ and D2O which are in their liquid state at room temperature, are located in separate flasks 1 and 2. A supply (not shown) of carrier qas, such as Ar or 2' is provided via feeders 3 and ~
respectively under the control of valves 5 and 6 to flasks 1 and 2. The carrier gas is further transported to the reaction region 7 in a furnace represented by fvrnace heaters 8, via a feeder 9 under the control of valve 10.
The apparatus further includes feeder lines 11 and 12 leading from flasks 1 and 2 to the reaction region 7. The 1()84S34 apparatus ~ay also include a supply of a further s-tarting material such as BC13 if a high silica content glass is desired. If this material is a liquid, it can be arranged to be carried to the reaction region 7 via the carrier gas, however, if it is gaseous such as BC13, it may be fed directly to the reaction region via a feeder line 13 under the eontrol of a valve 14. By the present invention, both preforms of glass fiber and slab optical waveguides may be fabrleated.
To make a fiber preform, a glass tubing substrate 15 upon which deposition takes place, is placed into the reaetion region. Reaetions (5) and (6) are obtained by setting the direct flow rates for Ar and BC13 to the reaction region and by bubbling Ar into the liquids in flasks 1 and 2 at eertain flow rates, vapor of SiC14 and D2O are thus transported to the reaction region 7. A wide range of flow rates of materials ean be used for this CVD
proeess. An example ~f the flow rates is 200 e.c./min. of Ar through SiC14, 400 e.e./rnin. of Ar through D2O
respeetively. In order to obtain a high--siliea~-content glass which is composed of SiO2 and B2O3 about 1 c.c./min.
of BC13 is flown. A wide range of furnaee temperatures can be used to obtain clear CVD layers. Clear CVD layers by the present invention were obtained even at furnace temperatures lower than 600C.
The preform is fabricated by depositing a first layer of eladding material onto inner wall of a glass ;
tubing substrate 15 and -then depositing core material onto the first la~er. This process is similar to conventional techni~ues for the fabrication of preforms, though the materials used in accordance with the present invention differ. A cross~s~ctional vi~w o,~ the resul-tant pre:Eonn is .
4S3~ :
.. .
shown in rigure 2 wherein the substrate tubing 15 is on the outside, followed by a first layer 16 of high-silica-content glass and a second layer 17 of glass having a higher refractive index. The center 18 of the core is hollow. After the preform is drawn, a fiber shown in figure 3 is formed by reducing the diameter and collapsing the center space. The layer 17 forms the core 19 of the fiber and the layer 16 forms the cladding 20 of the fiber.
In the above fiber, the core 19 may consist of an O-D
content fused silica glass and the cladding may consist of an O-D content high-silica content glass composed of SiO2 and B2O3, however, other combinations may also be produced having other glass composing atoms-oxide compounds.
Slab optical waveguides may be obtained by placing a substrate plate in the CVD reaction region 7 within a tubing and depositing the glass onto the plate. Two layered waveguides were formed on a substrate under the ; following conditions. Using oxygen as a carrier gas, D~O, at a temperature of 50C, was transported to the reaction region at a flow rate of 250 c.c./min., SiC14 was transported to the reaction region at 112 c.c./min., and BC13, a gas, was allowed to flow to the reaction region at a rate of 8 c.c./min. for 1~ hours and at a rate of ~ c.c./min. for 31 hours, to form two distinct layers of glass. These conditions were maintained in the formation of two samples of two layered glass at each of seven different furnace temperatures. The thicknesses of the two layered glass formed are tabu]ated below which shows a maximum layer thickness at a reaction temperature of approximately 525C.
~0~4S34 FURNACE OVERALL THICKNESS (~m) TE~PERATURE (C) 1st Sample 2nd Sample 1, Though the example reaction conditions are described with respect to a specific substrate, such as a plate or a tubing, it is recognized that the substrates are interchangeable and other glass fiber preforms can be fabricated in a similar way such as by depositing cladding material onto a rod substrate which is core material. Glass fiber optical waveguides are then obtained by reducing the diameter of the preform. Other fibers may be made by shaping O--D corltent glass into a rod and a tubing and inserting the rod into the tubing where it is fused, eliminating the air space between the rod and the tubing.
The composite glass rod is then drawn into a fiber by reducing its diameter.
This invention is directed to optical waveguides and in particular to glass fiber optical waveguides having low-loss characteristics in the infrared wavelength region at about 0.9 ~m.
A glass fiber optical waveguide is primarily composed of core and cladding. The core, which is the central portion of a glass fiber in the cross-section, has . - , . . .
either uniform or non-uniform refractive index distribution across the core. The electromagnetic wave is transmitted mainly in the core. The cladding, which is the outer portion of the glass fiber in the cross-section, has a lower refractive index than that of core material. The cladding in the glass fiber guides the electromagnetic wave.
In order to obtain low-loss optical waveguides it is important to use highly pure glass materials, especially in the core of glass fibers, because attenuation of light in the optical waveguides arises from the absorption of light by impurities in the glass materials as well as the light scattering by the spatial fluctuation of refractive index in the optical waveguides.
Intrinsically, fused silica is one of the best materials for the core or the cladding because both scattering loss and absorption loss of fused silica can be made very low. Other materials which are suited for low-loss optical waveguide production are high-silica-content glasses. The high-silica-content glasses normally contain SiO2 at more than 80 wt.~. High-silica-content glasses which contain B2O3 as an additive are useful as cladding materials of fused-silica core fibers. This type of glass-fiber 11 ' .
'. ~
-`" 1(1~4S3~
optical wa~;eguide has been described by D. Kato in the publication "Fused-silica~cGre glass fiber as a low-loss optical waveguide", Applied Physics Letters, Vol. 22, No. 1, pp. 3-4 (1973) and in U.K. Patent 1,435,523 to the Agency of Industrial Science and Technology and published on May 12, 1976. Materials which are suited for the cores of fused-silica-cladding glass fibers are high-silica-content glasses with additives such as TiO2, A1203, P205 and GeO2.
The latter type of glass fiber optical waveguide has been described by R.D. Maurer and P.C. Schultz in U.S. Patent 3,659,915, issued May 2, 1972. Refractive index of the high-silica-content glasses can be adjusted by selecting additive materials and controlling the contents.
Fused silica, which is also sometimes called fused quartz, is produced in conventioanl industrial process by fusing natural silica or quartz powder after a crushing and cleaning process. Other glasses are conventional~y made by melting mixed materials. Conventional fused silica as well as high-silica-content glasses are, however, not always useful at least as core materials for low-loss optical waveguides because these glasses still contain high levels of impurities such as transition metal ions.
Highly pure fused silica or high-silica-content glasses are conventionally produced by employing chemical reaction processes, which is called chemical vapor deposition (CVD). Chemical starting materials such as SiC14, Sill4, BC13, B2H4, GeC]3, POC13 can be highly purified by multiple-stage distillation because these materials can be vaporized at specific temperatures and pressures. It is noted, that their oxides such as SiO2, on the other harld, ' ' can not be purified by the distillation.
For the production of highly pure fused silica and high-silica-content glasses by the CVD process the - following chemical reactions have been used wherein the ,' starting materials or reactants are highly pure:
SiC14 + 2 ~ SiO2 + C12 (1) 4 22 ~-~ SiO2 + 2H2O (2) 2BC13 + 32 ~---~ 23 + 3C12 (3) SiC14 + 2H2 + 2 ) SiO2 etc.
Similar reactions are used for other compounds of glass-composing atoms. The reactions (1) to (3) are direct oxidation reactions, and the reaction (4) is known as flame ' hydrolysis because it ta};es place in an oxygen-hydrogen -flame.
Reactions such as (1) and (3) are called O~
free processes with which water-free glass materials can be produced. ',mall amount of water contained in glasses produced by the reaction (2) or (4) has a broad optical absorption spectrum of an O-H fundamental vibrational mode in infrared wavelength region at about 2.7 ~m. The broadening of the spectrum arises from the inhomogeneity of the environments of the bonds. The overtone absorption spectra appear in shorter wavelength regions, and are obstructive of low-attenuation light transmission in an important spectral region in which both sensitivity of Si diode-detector,devices and the emission spectrum of GaAlAs or GaAs diode light-source devices are available. Therefore, better attenuation characteristics in low-loss optical waveguides have been obtained by reducing or eliminating O-H
, .:
53~
content by the use of O-H free reactions. The elimination of O-H content by an O-H free CVD process, however, requires a higher temperature for oxidation to take place and yields a low deposition rate with the result that such O-H free method is rather costly. It has been found that O-H free fused silica or high-silica-content glasses are harder than O-H content glasses. The 0-H free glasses are also known to have an induced absorption spectrum that arises after some processing of the glass such as fiber drawing. These observed phenomena show that the content of small amount of silanol, i.e. Si-o-H, is important in the relaxation of local structure in glasses and thus in reducing local strains.
Solid products such as SiO2, B2O3 and GeO2 in reactions (1) to (4) are deposited onto a substrate.
Gaseous products such as C12, H2O and HCl as well as a part of fed starting gases are then taken away from the reaction region. Thus, highly pure fused silica or high-silica-content glasses are produced under contamination free circumstances. The CVD process was first applied to the production of g]ass and was described by M.E. Nordberg in U.S. Patent 2,326,039 which issued on August 3, 1943.
Reactions such as (1) and (3) produce glasses which do not contain water, i.e. O-H free. Other reactions such as (2) and (4) produce glass containing a small amount of water mainly in the form of silanol, i.e. -Si-o-H. The latter ~lasses are called O-I-I content glasses in contrast to O-H
free glasses~ U.S Patent 3,971,714 which issued to Maurer on February 12, 1974, describes a flame hydro1ysis glass producirg process wherein the startincJ material H2 is replaced by ~2 to produce a lo~ hydrox-71 ion content glass.
~s--108~534 This process however has the disadvantages that it requires D2, the isotope of H2 in the free state and that it takes place at a high temperature, i.e. in the order of 2000C, this increases the risk of product impurities due to the torch nozzle.
There are various ways for the fabrication of glass fibers. In the first method, a highly pure glass rod and a tubing either or both of which are the products of the CVD processes are fused to each other. This composite glass is called as a preform. The preform is then drawn into fibers. An examp]e of this method was described in the publication by D. Kato, and British Patent 1,435,523 mentioned above. In the second method, the CVD process is applied to form core and/or cladding glasses inside a tube substrate. Examples of the second type of method for the production of preforms were described by D.B. Keck and - -~-P.C. Schultz in U.S. Patent 3,711,262 which issed on January 16, 1973. In a third way, the CVD process is applied to form the cladding glass onto a rod substrate which is also a product of CVD process. An example of the third way for the production of a preform was described by D.B. Keck and R.D. Maurer in U.S. Patent 3,775,075 which issued on November 27, 1973. These preforms are softened at one end and then drawn into a thin glass fiber.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a glass composition suitable for optical waveguides having the structural characteristics of O-H content glasses.
It is a further object of this invention to provide a glass composition suitable for optical waveguides - : ~ . : --)134S34 ~' which does not have a s~rong optical absorption spectrum ~; of an o-~ overtone vibrational mode in infrared wave-length region at about 0.9 ~m.
It is another object of this invention to provide processes for producing O-H free glass having the structural characteristlcs of O-H content glass.
These and other objects are achieved in accordance with the present invention by a glass composition suitable for optical waveguides consisting of a glass-composing oxide compound containing O-D groups. This composition provides an O-H content type glass wherein the presence of a number of O-H groups are substituted by O-D groups. The O-D
groups may be in the form of -Si-o-D , and the glass-composing oxide compound may be one or more of the compounds selected from the group consisting of SiO2, B2O3, GeO2~ P2O5, SnO2~ TiO2~ A12O3 and ZrO2.
The chemical vapor deposition process is used to produce the O-D content glass either by a hydrolysis reaction of D2O with an aprotic compouncl of glass-compo~ing-atoms or by the oxidation of a deuterium compound of glass-composing-atoms. The glass may then be stabilized by fire polishlng it with a hydrogen-ox~yen flame.
Glass fiber optical waveguides may be produced having a core made of O-D content glass or both a core and a cladding made of O-D content glass.
~RIEF DESCRIPTION OF THE D~AWINGS
In the drawings:
Figure 1 is a schematic diagram of a chemical vapor deposition apparatus for proclucing O-D content glass;
3p Figure 2 is a cross-sectioral view of a preform .
. :
10~4534 for a glass fiber optical waveguidei and Figure 3 is a cross-sectional view of a glass fiber optical waveguide.
DESCRIPTION OF PREFERRED EMBODI~ENTS
In order to overcome the disadvantages encountered in conventional O-H fr~e glass fiber optical waveguides in terms of its optical transmission characteristics while at the same time maintaining the advantages of an O-H content type of glass, the glass compound in accordance with the present invention from which glass fiber optical waveguides are formed, are made to contain small amounts of the hydrogen isotope (D) as an O-D group in a process other than the flame hydrolysis deposition process.
The O-D content glass materials is produced most effectively by the use of chemical vapor deposition (CVD) techniques. In accordance with the present invention, however, isotopic starting materials are used in the CVD
process. In acldition, it is found that the use of heavy water, i.e. D2O, is a preferable isotopic starting material for the production of O-D content glasses because it is economical. Heavy water is available at a lower price than other isotopic compounds because it is a primary product and is obtained in a mass enrichment process for natural-uranium heavy-water nuclear reactors such as CANDU
in Canada.
As a first embodiment of the me-thod of producing O-D content glass in accordance with the present invention, the following are examp]es of CVD reaction schemes which can .
, ~; - 1084534 be emploved:
SiCl4 + 2D20 -~ SiO2 + 4DCl (5) 3 + 3D2O ~ B2O3 + 6DCl (6) GeC14 + 2D20---~ GeO2 + 4DC1 (7) where D is an isotope of hydrogen. These reaction schemes as given in (5) to (7)lcan proceed without necessity of heat and at lower temperatures than direct oxidations, and may be called cold hydrolysis reactions. Materials in the , lefthand side of reactions t5) to (7) can be transported in certain carrier gases such as Ar when they are in liquid state at a given temperature. Reaction schemes (5) to (7) ' are essentially reactions between aprotic compounds of glass-composing atoms and heavy water. Other compounds such as POC13, TiCl4, AlCl3, SnCl4 and ZrCl4;can also be used , in similar CVD xeaction schemes to obtain different glass compositions in accordance with the present invention.
The isotopic starting material need not however be limited to D2O. As a second em~odiment oE the method of producing O-D content glass.in accordance with this invention, the following are examples of other CVD reaction schemes which can be employed:
SiD4 + 2O2 --~ SiO2 + 2D2O (8) GeD4 + 202---~ GeO2 + 2D2o (9) B2D6 + 32 ~~~~ B203 + 3D20 (10) These reaction schemes are essentially oxidation reactions of deuterium compounds of glass-composing-atorns. Other deuterium compounds of glass-composing-atoms such as SnD4 can also be used in the simil?.r oxidation reaction schemes. This second ernbodiment of the .:
-` 10~4S39~
present invention for the fabrication method would be useful if the deuteration of compounds of glass-composing-atoms were performed economically. Although deuterium compounds of glass-composing atoms are presently rather expensive J the cost could be lowered if the deuteration processes are optimumly industrialized. Under such circumstance this second method may be superior to the first method because carrier gases of heavy water vapor and the aprotic compounds vapor which are necessary in the first method are not always needed in the second method. Heavy water solutions of compounds of glass-composing atoms such as D3PO4 can also be used, if it is necessary for the modification of glass properties, by transporting the mixed vapor by the use of carrier gas in the second method.
The glass layer or layers resulting from bo-th of the above methods, undergoes a normal structure relaxation over a period of time wherein trapped vapor of the starting materials such as D2O are released. ~his relaxation process may be accelerated by fire polishing the glass layer or layers using a hydrogen-oXygen :Elame.
Figure 1 is a schematic diagram of C~D apparatus for producing O-D content glass using D2O as a starting material. The starting materials SiCl~ and D2O which are in their liquid state at room temperature, are located in separate flasks 1 and 2. A supply (not shown) of carrier qas, such as Ar or 2' is provided via feeders 3 and ~
respectively under the control of valves 5 and 6 to flasks 1 and 2. The carrier gas is further transported to the reaction region 7 in a furnace represented by fvrnace heaters 8, via a feeder 9 under the control of valve 10.
The apparatus further includes feeder lines 11 and 12 leading from flasks 1 and 2 to the reaction region 7. The 1()84S34 apparatus ~ay also include a supply of a further s-tarting material such as BC13 if a high silica content glass is desired. If this material is a liquid, it can be arranged to be carried to the reaction region 7 via the carrier gas, however, if it is gaseous such as BC13, it may be fed directly to the reaction region via a feeder line 13 under the eontrol of a valve 14. By the present invention, both preforms of glass fiber and slab optical waveguides may be fabrleated.
To make a fiber preform, a glass tubing substrate 15 upon which deposition takes place, is placed into the reaetion region. Reaetions (5) and (6) are obtained by setting the direct flow rates for Ar and BC13 to the reaction region and by bubbling Ar into the liquids in flasks 1 and 2 at eertain flow rates, vapor of SiC14 and D2O are thus transported to the reaction region 7. A wide range of flow rates of materials ean be used for this CVD
proeess. An example ~f the flow rates is 200 e.c./min. of Ar through SiC14, 400 e.e./rnin. of Ar through D2O
respeetively. In order to obtain a high--siliea~-content glass which is composed of SiO2 and B2O3 about 1 c.c./min.
of BC13 is flown. A wide range of furnaee temperatures can be used to obtain clear CVD layers. Clear CVD layers by the present invention were obtained even at furnace temperatures lower than 600C.
The preform is fabricated by depositing a first layer of eladding material onto inner wall of a glass ;
tubing substrate 15 and -then depositing core material onto the first la~er. This process is similar to conventional techni~ues for the fabrication of preforms, though the materials used in accordance with the present invention differ. A cross~s~ctional vi~w o,~ the resul-tant pre:Eonn is .
4S3~ :
.. .
shown in rigure 2 wherein the substrate tubing 15 is on the outside, followed by a first layer 16 of high-silica-content glass and a second layer 17 of glass having a higher refractive index. The center 18 of the core is hollow. After the preform is drawn, a fiber shown in figure 3 is formed by reducing the diameter and collapsing the center space. The layer 17 forms the core 19 of the fiber and the layer 16 forms the cladding 20 of the fiber.
In the above fiber, the core 19 may consist of an O-D
content fused silica glass and the cladding may consist of an O-D content high-silica content glass composed of SiO2 and B2O3, however, other combinations may also be produced having other glass composing atoms-oxide compounds.
Slab optical waveguides may be obtained by placing a substrate plate in the CVD reaction region 7 within a tubing and depositing the glass onto the plate. Two layered waveguides were formed on a substrate under the ; following conditions. Using oxygen as a carrier gas, D~O, at a temperature of 50C, was transported to the reaction region at a flow rate of 250 c.c./min., SiC14 was transported to the reaction region at 112 c.c./min., and BC13, a gas, was allowed to flow to the reaction region at a rate of 8 c.c./min. for 1~ hours and at a rate of ~ c.c./min. for 31 hours, to form two distinct layers of glass. These conditions were maintained in the formation of two samples of two layered glass at each of seven different furnace temperatures. The thicknesses of the two layered glass formed are tabu]ated below which shows a maximum layer thickness at a reaction temperature of approximately 525C.
~0~4S34 FURNACE OVERALL THICKNESS (~m) TE~PERATURE (C) 1st Sample 2nd Sample 1, Though the example reaction conditions are described with respect to a specific substrate, such as a plate or a tubing, it is recognized that the substrates are interchangeable and other glass fiber preforms can be fabricated in a similar way such as by depositing cladding material onto a rod substrate which is core material. Glass fiber optical waveguides are then obtained by reducing the diameter of the preform. Other fibers may be made by shaping O--D corltent glass into a rod and a tubing and inserting the rod into the tubing where it is fused, eliminating the air space between the rod and the tubing.
The composite glass rod is then drawn into a fiber by reducing its diameter.
Claims (3)
1. A method of producing a glass composition suitable for optical waveguides comprising:
- providing an aprotic compound of glass-composing atoms;
- providing D2O; and - reacting the D2O and the aprotic compound of glass-composing-atoms in a chemical vapor deposition process by hydrolysis to provide a glass compound having O-D groups.
- providing an aprotic compound of glass-composing atoms;
- providing D2O; and - reacting the D2O and the aprotic compound of glass-composing-atoms in a chemical vapor deposition process by hydrolysis to provide a glass compound having O-D groups.
2. A method as claimed in claim 1 wherein the aprotic compound of glass-composing-atoms consist of one or more of the compounds selected from the group consisting of SiCl4, BCl3, POCl3, SnCl4, TiCl4, AlCl3, GeCl4 and ZrCl4.
3. A method as claimed in claims 1 or 2 wherein the hydrolysis temperature is below 600°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US78006077A | 1977-03-22 | 1977-03-22 | |
| US780,060 | 1977-03-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084534A true CA1084534A (en) | 1980-08-26 |
Family
ID=25118453
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA287,390A Expired CA1084534A (en) | 1977-03-22 | 1977-09-23 | Method of producing glass compositions for optical wave guides |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS53117439A (en) |
| CA (1) | CA1084534A (en) |
| FR (1) | FR2384725A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5567537A (en) * | 1978-11-17 | 1980-05-21 | Hitachi Ltd | Production of unmolten glass of low hydroxyl ion content |
| JPS56117206A (en) * | 1980-02-22 | 1981-09-14 | Nippon Telegr & Teleph Corp <Ntt> | Optical fiber and its manufacture |
| IT1130481B (en) * | 1980-06-16 | 1986-06-11 | Cselt Centro Studi Lab Telecom | PROCEDURE FOR THE REDUCTION OF THE CONTENT OF OXYDRY GROUPS IN PREFORMS FOR OPTICAL FIBERS MADE ACCORDING TO THE MCVD METHOD |
| IT1145157B (en) * | 1981-06-22 | 1986-11-05 | Cselt Centro Studi Lab Telecom | PROCEDURE AND DEVICE FOR THE IN-LINE DEHYDROGENATION OF PREFORMS FOR OPTICAL FIBERS |
| JPS6086043A (en) * | 1983-10-14 | 1985-05-15 | Nippon Telegr & Teleph Corp <Ntt> | Manufacture of optical fiber preform |
| CA2310219A1 (en) * | 2000-05-29 | 2001-11-29 | Nu-Wave Photonics Inc. | Application of deuterium oxide in producing silicon containing and metal containing materials |
| NL1022140C2 (en) * | 2002-12-11 | 2004-06-15 | Draka Fibre Technology Bv | Deposition of glass layers inside tube using reactive gases, useful for preparing optical fibres, comprises treating glass forming compounds with deuterium before deposition |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3722981A (en) * | 1971-05-17 | 1973-03-27 | Bell Telephone Labor Inc | Low melting point optical transmission line |
| US3791714A (en) * | 1972-03-30 | 1974-02-12 | Corning Glass Works | Method of producing glass for optical waveguides |
-
1977
- 1977-09-23 CA CA287,390A patent/CA1084534A/en not_active Expired
-
1978
- 1978-02-06 JP JP1223178A patent/JPS53117439A/en active Pending
- 1978-02-13 FR FR7804024A patent/FR2384725A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FR2384725A1 (en) | 1978-10-20 |
| JPS53117439A (en) | 1978-10-13 |
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