CN1318038A - Method of making soot for optical fiber preforms and preforms made therefrom - Google Patents

Abstract

The present invention relates to a method of preparing soot for use in the manufacture of light guides. Both non-aqueous liquid reactant containing one or more salts and aqueous solution are conveyed through an atomizing burner assembly to form a uniform coal plume containing oxides of selected constituents contained in the non-aqueous liquid reactant and aqueous solution. The resulting multi-component soot is collected by conventional methods to form preforms for use in the manufacture of optical fibers. Alternatively, the aqueous solution may be atomized with a gas in a first burner assembly to form an aerosol, and the reactant in the vapor state delivered to a second burner assembly. Preforms made by the method are also disclosed. The aqueous solution preferably contains metal salts, such as acetates, nitrates, sulfates, carbonates, chlorides, hydroxides. The metal of the metal salt is preferably an alkali metal, an alkaline earth metal, lead, lanthanum, cobalt, antimony, erbium, aluminum, neodymium, praseodymium.

Description

Method of making soot for optical fiber preforms and preforms made therefrom

field of invention

This invention relates to methods of forming soot for use in the manufacture of glass, and more particularly to methods of feeding liquid precursors and other reactants into a flame to form soot for use in the manufacture of light guides, and the resulting The light guide.

While the present invention is applicable to a wide variety of glass soot applications, it is particularly well suited for depositing soot onto a target to form a preform for the manufacture of optical fibers, as will be described in more detail below.

background of the invention

Various methods are known in the art involving the preparation of oxides, especially metal oxides, from gaseous reactants. This method requires a raw material solution or precursor, a gaseous raw material liquid (hereinafter referred to as gaseous reactant) and an oxidizing agent to the conversion reaction site (also known as soot reaction zone by those skilled in the art or combustion zone), a device that simultaneously catalyzes oxidation and combustion to produce fine spherical aggregates called soot. This soot can be collected in any manner, from capture in the collection chamber to deposition on the rotating shaft. The collected soot can be immediately or subsequently heat treated to form a high-purity, non-porous, transparent glass product. This method is usually carried out with specialized equipment having unique nozzles, injectors, burners and/or burner assembly arrangements.

Much of the initial research that led to the development of this method focused on the preparation of monolithic vitreous silica. Choosing the right raw materials is an important aspect of the job. Thus, at that time it was identified that a material capable of producing a vapor pressure of 200-300 millimeters of mercury (mmHg) at a temperature below about 100°C could be used to make the monolithic vitreous silica. The high vapor pressure of silicon tetrachloride (SiCl ₄ ) suggested that it could be used as a convenient source of vapors for the formation of soot, a discovery that subsequently led to the use of a series of similar halide-based feedstocks. More than any other factor, this factor has contributed to the currently accepted use of _SiCl4 , _GeCl4 , _POCl3 , and _BCl3 as feed vapor sources.

However, the use of these and other halide-based feedstocks as vapor sources has its drawbacks. The main disadvantage is the formation of hydrochloric acid (HCl) as a by-product of oxidation. Hydrochloric acid not only damages deposition substrates and reaction equipment, but is also harmful to the environment. In order to overcome this disadvantage and for other reasons, non-halide compounds have been used as precursors or raw materials for the preparation of photoconductive soot.

Although the use of non-halide silicon compounds as raw materials for making fused silica glass avoids the formation of hydrochloric acid, for example as described in U.S. Pat. , especially so. It has been found that during the delivery of vaporous polyalkylsiloxane vapors to the burner, in the delivery lines for the gaseous reactants to the burner or within the burner, polymeric substances are deposited in the form of gels. This results in a reduced deposition rate of soot that subsequently consolidates into a preform from which optical fibers are drawn. This also often creates defects from the preform, with the result that the optical fiber formed therefrom is defective or even unusable. Another problem encountered in making silica soot from siloxane feedstocks is the deposition of particles containing high molecular weight and high boiling points on optical fiber preforms. The formation of these particles leads to "defects" or "aggregate defects" which can have a detrimental effect on the optical and structural quality of lightguides made from silica soot.

Other materials, some of which are currently available and some of which may be used to form soot for the manufacture of light guides, are not currently accepted for delivery by vapor deposition in place of the halide-based and non-halide materials described above. For example, salts and those substances called rare earth elements, whose vapors are extremely unstable, often break down in the vapor state before they can be transported. These components will come out of solution as solids rather than being delivered as gas from the burner.

While it is often possible to deliver at least some percentage of this component as a vapor to the combustion zone, it is technically difficult. It is necessary to have elaborate systems with expensive equipment to convert these components into vapors and transport them further to the combustion zone without leaving solid deposits in the delivery lines to the burners and in the burners themselves. In addition, if multiple components are delivered in vapor form, and a certain percentage of each component is required for the desired glass composition, it is difficult to control the delivery to provide that percentage of the vapor mixture because different components have different vapor pressure.

U.S. Patent Application No. 08/767,653 discloses: feeding the raw material in liquid form to an injector or burner, atomizing the raw material to form an aerosol containing liquid raw material droplets, and converting the atomized liquid raw material into soot in the combustion zone , these and other disadvantages can be overcome. US Patent Application No. 08/767,653 discloses injectors, burners and burner assemblies that rely on very fine orifices to deliver a fine stream of liquid for proper atomization. Because the feedstock is fed directly to the burner flame in a liquid state, rather than in a vapor state, the vapor pressure of the feedstock is no longer the limiting factor for delivery. Therefore, many other components can now be delivered as raw materials or dopants to form soot for the manufacture of light guides.

However, many components, especially those generally classified as salts, are not readily transported to the flame as organometallic compounds in liquid form. The required purity is often extremely high, and the steps to obtain the compound at the required purity are cost prohibitive.

Accordingly, there is a need for a method of making soot for use in making optical guides, and in particular optical fiber preforms, that precisely controls the amounts of components being delivered while avoiding gel formation in the delivery lines. Further, what is needed is a liquid delivery method that can produce glass soot containing the desired stoichiometric amounts of metal oxides, conventional dopants and salts, without the need for expensive and elaborate equipment.

Overview of the invention

The present invention relates to a method of delivering liquids and other reactants to a combustion zone adjacent a burner assembly to produce soot for glass production. In the liquid delivery system, the liquid reactant that can be transformed into glass by thermal oxidative decomposition is provided and directly introduced into the combustion zone of the burner, thereby forming fine amorphous soot in an amorphous form. Examples of such liquid delivery systems are described in the following patent application: U.S. Patent Application No. 08/1996, entitled "Method and Apparatus for Forming Fused Silica by Combustion of Liquid Reactants," filed October 17, 1996. 767,653; U.S. Patent Application No. 08/903,501, filed July 30, 1997, entitled "Method of Combusting Liquid Reactants to Form Silicon Oxide Using Oxygen"; U.S. Patent Application No. 09/089,869, "Method and Apparatus for Forming Silicon Oxide from Liquid Reactants"; U.S. Provisional Patent Application No. .60/068,255 and US Provisional Patent Application, filed July 31, 1998, entitled "Apparatus and Method for Making Soot for Glassmaking," the specifications of which patent applications are hereby incorporated by reference. The amorphous soot can be collected by any method, but is generally deposited onto a receiver surface where the soot is consolidated into a fused glass body, either substantially simultaneously with or after deposition. This glass body can then be directly formed into an article, or the fused body can be further processed, such as stretched to form a light guide, such as an optical fiber, as described, for example, in the article entitled "Methods for Purifying Polyalkylsiloxanes and Formed Articles." is further described in U.S. Patent Application No. 08/574/961, the specification of which is incorporated herein by reference.

The method of the present invention has many advantages over other glass soot manufacturing methods known in the industry. The present invention enables precise variation and control of the composition of the soot formed, thereby providing optical fibers with well-defined and very accurate exponential profile and other characteristics. The present invention also provides the industry with a method for simultaneously delivering many types of components into a flame to produce multicomponent glass soot. Any number of organometallics, rare earth elements, and now salts can all be delivered simultaneously into the flame, creating a uniform soot. Similarly, these components can be delivered simultaneously or selectively in the same soot preparation process to produce preforms meeting specific layer requirements. Therefore, optical fiber preforms made by the method of the present invention have the advantage of precise amounts of components, some of which are never present in a single optical fiber preform.

To achieve these and other advantages, a non-aqueous liquid reactant and an aqueous solution are atomized to form an aerosol of liquid droplets. This aerosol is fed into the combustion zone where it reacts within the flames of the combustion zone to form fine glass soot particles.

In another aspect of the invention, a non-aqueous liquid reactant and an aqueous solution are delivered to the combustor assembly. The non-aqueous liquid reactant and aqueous solution are discharged from the burner assembly into the flame where they react to form soot. The soot is deposited onto the target, forming a preform.

In yet another aspect of the invention, an optical fiber preform is formed by delivering a non-aqueous liquid reactant and an aqueous solution to a burner assembly. The non-aqueous liquid reactant and aqueous solution are discharged from the burner assembly into the flame in the form of an aerosol consisting of many droplets of the non-aqueous liquid reactant and many droplets of the aqueous solution. The liquid droplets react in the flame to form soot and deposit on the target, becoming a preform.

In yet another aspect of the invention, the delivery of an aqueous solution is combined with the delivery of conventional steam. The aqueous solution is atomized with gas in the burner assembly to form an aerosol of many liquid droplets while vaporizing another reactant into the burner assembly. The reactants in the vapor state react with the gas mist in the combustion zone adjacent to the burner assembly to form fine glass soot.

Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part may be obvious from the description, or may be learned by practice of the invention. It will be appreciated by those skilled in the art that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to further explain the invention as claimed herein.

For further understanding of the present invention, some accompanying drawings are included in this specification, and the accompanying drawings constitute a part of this specification. The drawings illustrate several embodiments of the invention and together with the description serve to explain the principles of the invention.

Brief description of the drawings

Figure 1 schematically illustrates a first preferred embodiment of the liquid delivery system used in the method of the present invention.

Figure 2 schematically illustrates a second preferred embodiment of a liquid delivery system for use in the method of the present invention.

Figure 3 schematically illustrates a preferred embodiment of a mixed vapor and liquid delivery system for use in the process of the present invention.

Detailed Description of the Preferred Embodiment

A number of soot collection and soot deposition techniques are used to create glass products. While the present invention can be used in many such techniques, it is particularly suitable for those techniques for depositing soot on a target to form a glass preform for making light guides, especially optical fibers. However, it will be apparent to those skilled in the art that the method of the present invention can also be used to fabricate planar waveguides.

During the manufacture of optical fibers, soot is generally deposited uniformly on or into the target. The collected soot is consolidated into a high-purity glass preform, which is then subjected to further processing steps such as stretching to form thin fibers that transmit and guide light. Accordingly, the invention will be described in this regard. However, those skilled in the fiber optic industry will appreciate that there are other systems, and systems with some variation from those described herein, that can employ the present invention to perform the functions described above and claimed herein. Preferred embodiments of the invention will now be described in detail, examples of which are schematically illustrated in the accompanying drawings.

A first preferred embodiment of a system for feeding liquid into a combustion zone to form multicomponent soot for glassmaking is schematically illustrated in FIG. 1 . Liquid delivery system 10 includes an aqueous solution container 12 containing an aqueous solution 14, a non-aqueous liquid reactant container 16 containing a non-aqueous liquid reactant 18, and an optional dopant container 20 containing a dopant 22. Additionally, the liquid delivery system 10 includes an atomizing burner assembly 26, such as an atomizing burner assembly and associated delivery mechanism, (hereinafter collectively referred to as "the burner assembly"). For such burner assemblies, U.S. Patent Application No. 08/767,653, entitled "Method and Apparatus for Forming Fused Silica from Combustion of Liquid Reactants," filed October 17, 1996; July 30, 1997 Application, U.S. Patent Application No. 08/903,501, entitled "Method of Combusting Liquid Reactants to Form Silicon Oxide Using Oxygen"; filed June 3, 1998, entitled "Method of Combusting Liquid Reactants to Form Silicon Oxide Using a Heater" U.S. Patent Application No. 09/089,869, and Apparatus"; U.S. Provisional Patent Application No. 60/068,255, filed October 19, 1997, entitled "Burner and Method for Producing Metal Oxide Soot"; All are described in the US Provisional Patent Application, filed on March 31, entitled "Apparatus and Method for Preparing Soot for Making Glass", the specification of which is hereby incorporated by reference.

In operation, the aqueous solution 14, the non-aqueous liquid reactant 18 and the dopant 22 are mixed according to the desired stoichiometry and stored in their respective containers 12, 16 and 20. The aqueous solution 14 is preferably filled with a water-soluble salt such as an alkali metal nitrate, alkali metal carbonate, alkali metal sulfate, alkali metal acetate, alkaline earth metal nitrate, alkaline earth metal carbonate, alkaline earth metal sulfate or alkaline earth metal acetylene. salt. More specifically, the aqueous solution 14 contains one or more water soluble salts such as barium nitrate, barium acetate, barium chloride, strontium nitrate, strontium acetate, strontium chloride, antimony nitrate, antimony acetate, lead nitrate, lead carbonate, sulfuric acid Lead, lead acetate, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, potassium nitrate, potassium chloride, praeseodymium nitrate, cesium nitrate, Cesium chloride, cesium sulfate, cesium hydroxide, calcium chloride, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride and erbium sulfate, but may also contain other salts and/or other Element.

The non-aqueous liquid reactant 18 is preferably a liquid organometallic compound such as octamethylcyclotetrasiloxane, but may also be a silicon alkoxide, a metal alkoxide or be made soluble with a suitable organic solvent such as ethylene glycol monomethyl ether. soluble other silicon-containing substrates. Dopant 22, if used, can be a ketone salt, alkoxide, acetate, beta-diketone salt, or fluorine-beta of praseodymium, holmium, and thulium dissolved in a suitable organic solvent such as ethylene glycol monomethyl ether. - diketone salts. Preferred dopants 22 are generally erbium, germanium and other rare earth elements whose properties are favorable for optical fibers.

Aqueous solution 14, non-aqueous liquid reactant 18 and dopant 22 are delivered to burner assembly 26 via liquid delivery line 24 in the desired quantities, if desired. Liquids 14 , 18 , and 22 are discharged from burner assembly 26 into flame 28 in the form of atomized droplets 30 . The droplets 30 are homogeneously mixed during atomization and react in the flame 28 to create a soot stream 32 . The soot stream 32 is preferably directed toward a target, such as the axis of rotation 34, while the burner assembly 26 moves back and forth along the length of the axis of rotation 34 to deposit the soot onto the axis of rotation 34 to form a desired amount of water contained in the aqueous solution 14. , the non-aqueous liquid reactant 18 and the uniform soot body 36 of oxides of the elements within the dopant 22.

A second preferred embodiment of a system for feeding liquid into a combustion zone to form multicomponent soot for glassmaking is shown in FIG. 2 . Like the first preferred embodiment, the liquid delivery system includes an aqueous solution container 42 for storing an aqueous solution 44, a non-aqueous liquid reactant container 46 for storing a non-aqueous liquid reactant 48, and an optional adulterant container for storing an adulterant 52 50. However, unlike the first preferred embodiment of the present invention, the liquid delivery system 40 includes a first burner assembly 56 in selective communication with the non-aqueous liquid reactant container 46 and the dopant container 50, and also includes The second burner assembly 66 communicates with the aqueous solution container 42 . As will be described below, those skilled in the art will appreciate that the aqueous solution 44 and the non-aqueous liquid reactant 48 may contain one or more of the compounds described above for the first preferred embodiment of the present invention.

In operation, the aqueous solution 44 is selectively delivered to the second burner assembly 66 and the non-aqueous liquid reactant 48 and dopant 52 (if desired) are selectively delivered to the first burner assembly 56 . The first burner assembly 56 discharges the atomized liquid droplets 60 into the flame 58 where the liquid droplets 60 burn to form a soot stream 62 containing the selected non-aqueous liquid reactants 48 and dopants A homogeneous mixture of oxides produced by the oxidation of the components in 52. The second burner assembly 66 can be activated simultaneously with the first burner assembly 56 or separately to discharge the atomized liquid droplets 70 into the flame 68 to form a uniform soot stream 72 containing the components contained in the aqueous solution 44. oxides formed by oxidation. The soot streams 62 and 72 are preferably directed toward a target such as the axis of rotation 74, and as the first burner assembly 56 and the second burner assembly 66 move back and forth along the length of the axis of rotation 74, the soot from the soot streams 62 and 72 are A uniform layer is deposited onto the rotating shaft 74 . The resulting soot body 76 contains all of the oxides from the soot streams 62 and 72, depending on the delivery rate.

The multiple burner assembly used with this embodiment of the invention generally facilitates a greater soot deposition rate than the first embodiment of the invention. Additionally, the spatial arrangement of the burner assemblies 56 and 66 enables the soot to be deposited in discrete layers, which can provide a controlled and cost-effective method of producing light guide.

Figure 3 schematically illustrates a preferred embodiment of a mixed vapor and liquid delivery system 80 for carrying out the method of the present invention. The mixed vapor and liquid delivery system 80 includes an aqueous solution vessel 82 that stores an aqueous solution 84 , and a liquid delivery line 90 that delivers the aqueous solution 84 to a first burner assembly 94 . In addition, the vapor and liquid mixed delivery system 80 also includes a vapor delivery system 86 that delivers the vapor reactant 88 to a second combustor assembly 96 via a vapor delivery line 92 . The steam delivery system 86 may be any steam delivery system known in the industry, such as, but not limited to, those disclosed in US Patent Nos. 5,043,002 and 3,698,936, the descriptions of which are incorporated herein by reference. Vapor reactant 88 is preferably a halide-based feedstock, such as, but not limited to, _SiCl4 , or a non-chloride-based feedstock, such as, but not limited to, octamethylcyclotetrasiloxane. The aqueous solution 84 preferably contains a water-soluble salt such as an alkali metal nitrate, alkali metal carbonate, alkali metal sulfate, alkali metal acetate, alkaline earth metal nitrate, alkaline earth metal carbonate, alkaline earth metal sulfate, or alkaline earth metal acetylene. salt. More specifically, the aqueous solution 84 contains one or more water soluble salts such as barium nitrate, barium acetate, barium chloride, strontium nitrate, strontium acetate, strontium chloride, antimony nitrate, antimony acetate, lead nitrate, lead carbonate, sulfuric acid Lead, lead acetate, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, potassium nitrate, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride , cesium sulfate, cesium hydroxide, calcium chloride, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride and erbium sulfate, but may also contain other salts and/or other ingredients that can be mixed and delivered in aqueous solution.

In operation, aqueous solution 84 is selectively delivered to burner assembly 94 and vaporized reactant 88 is delivered to second burner assembly 96 . At the first burner assembly 94, the aqueous solution 84 is atomized with a gas such as air, but preferably with oxygen or with an inert gas such as nitrogen, to form a gas consisting of a plurality of droplets, typically about 10-200 microns in size. fog. The particle size of most droplets is generally about 20 microns. The atomized liquid droplets 98 are discharged into a first flame formed adjacent to the first burner assembly 94, wherein the atomized liquid droplets 98 burn to form a first soot stream 102 containing the selected Oxidation of the constituents forms a homogeneous mixture of oxides. Steam reactant 88 is delivered through steam delivery line 92 and second burner assembly 96 as steam 104 that is exhausted into a second flame 106 formed proximate to second burner assembly 96 . The steam 104 is combusted in the second flame 106 to form a soot stream 108 containing a homogeneous mixture of oxides formed by the oxidation of selected components contained in the steam reactant 88 . The first and second soot streams 102, 108 are respectively directed at a target, such as the axis of rotation 110; The soot within and 108 is deposited onto the rotating shaft 110 in a uniform layer. Depending on the delivery rate, the resulting soot body 112 contains all of the oxides from the first and second soot streams 102 and 108, respectively.

Although not shown in FIG. 3, a burner assembly and associated delivery mechanism may be added to the system shown in FIG. 3 to deliver additional inclusions of soot commonly used in the manufacture of optical fibers. This embodiment of the invention combines the higher soot deposition rates of vapor deposition with the unique optical properties provided by salts delivered in aqueous solution. Those skilled in the art will understand that the vapor reactant 88 and the aqueous solution 84 can be fed into the same flame to create a uniform stream of soot that can be collected in any manner generally known in the art and can then be further processed into a light guide , especially optical fiber preforms.

Although not shown in the drawings, those skilled in the art will appreciate that the systems shown in Figures 1, 2 and 3 are not limited to the number of burner assemblies and associated delivery mechanisms shown in the figures. Each system can be supplemented with burner assemblies and associated delivery mechanisms to implement the method of the present invention. In general, the greater the number of burner assemblies, the greater the soot deposition rate. Additionally, the present invention can be used in conjunction with other vapor delivery systems commonly known in the industry to provide greater flexibility in the optical fiber soot manufacturing process.

Those skilled in the art will recognize that various changes and modifications can be made in the method of the present invention for making soot from an optical fiber preform without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers such changes and modifications as come within the scope of the appended claims and their equivalents. In addition, all the means or steps in the appended claims and the corresponding structures, materials, operations and gist of the devices or steps having the same effect include any structure, material, and combination with other gist specifically required herein to realize their functions. or operational.

Claims (22)

1. A method for preparing soot for making an optical fiber preform, the method comprising the steps of: a) atomizing the non-aqueous liquid reactant and the aqueous solution to form an aerosol comprising many droplets; b) sending the aerosol into the combustion zone; c) reacting said aerosol in a flame provided within said combustion zone to form fine glass soot particles. 2. The method of claim 1, wherein said non-aqueous liquid reactant comprises a non-aqueous solution. 3. The method of claim 1 further comprising the step of delivering said non-aqueous liquid reactant and said aqueous solution to a single burner assembly prior to atomizing said non-aqueous liquid reactant and said aqueous solution . 4. The method according to claim 1, before said step a), the method also comprises the steps of: delivering the non-aqueous liquid reactant to a first burner assembly; The aqueous solution is delivered to a second burner assembly spaced from the first burner assembly. 5. The method of claim 4, further comprising the steps of: atomizing the non-aqueous liquid reactant in the first burner assembly to form a first aerosol; The aqueous solution is atomized in the second burner assembly to form a second aerosol. 6. The method of claim 5, further comprising the steps of: reacting the first aerosol within a first flame formed adjacent the first burner assembly; The second aerosol is reacted within a second flame formed adjacent the second burner assembly. 7. The method of claim 1, wherein said non-aqueous liquid reactant comprises at least one precursor and at least one dopant. 8. 3. The method of claim 1, wherein said non-aqueous liquid reactant comprises siloxane, and wherein said aqueous solution comprises a salt. 9. The method of claim 8, wherein said salt is selected from the group consisting of: alkali metal nitrates, alkali metal carbonates, alkali metal sulfates, alkali metal acetates, alkaline earth metal nitrates, alkaline earth metal carbonates, Alkaline earth metal sulfates, alkaline earth metal acetates, barium nitrate, barium acetate, barium chloride, strontium nitrate, strontium acetate, strontium chloride, antimony nitrate, antimony acetate, lead nitrate, lead carbonate, lead sulfate, lead acetate, nitric acid Lanthanum, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, potassium nitrate, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride, cesium sulfate, hydroxide Cesium, calcium nitrate, calcium chloride, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride, and erbium sulfate. 10. 9. The method of claim 9, wherein said non-aqueous liquid reactant further comprises a dopant. 11. A method of manufacturing an optical fiber preform, the method comprising the steps of: a) delivering the non-aqueous liquid reactant and aqueous solution to the burner assembly; b) discharging said non-aqueous liquid reactant and said aqueous solution from said burner assembly into a flame; c) reacting said non-aqueous liquid reactant and said aqueous solution in said flame to produce soot; and d) Depositing the soot onto the rotating shaft. 12. The method of claim 11, wherein said step b) includes the step of atomizing said non-aqueous liquid reactant and said aqueous solution to form an aerosol comprising a mixture of a plurality of aqueous solution droplets Many non-aqueous liquid reactant droplets. 13. 12. The method of claim 12, wherein said atomizing step occurs while said non-aqueous liquid reactant and said aqueous solution are being discharged from said burner assembly. 14. The method of claim 11, wherein said burner assembly comprises a first burner assembly and a second burner assembly spaced from said first burner assembly, wherein said non-aqueous liquid reactant serves as A first mist containing droplets of a non-aqueous liquid reactant is discharged from the first burner assembly, wherein the aqueous solution is discharged from the second burner assembly as a second mist containing droplets of the aqueous solution. 15. The method of claim 14, wherein said flames include a first flame adjacent to said first burner assembly and a second flame adjacent to said second burner assembly, wherein said first aerosol is The reaction takes place in the first flame and the second aerosol reacts in the second flame. 16. The method of claim 11, wherein said non-aqueous liquid reactant comprises at least one precursor and at least one dopant. 17. 11. The method of claim 11, wherein said non-aqueous liquid reactant comprises siloxane, and wherein said aqueous solution comprises a salt. 18. The method of claim 17, wherein said salt is selected from the group consisting of: alkali metal nitrates, alkali metal carbonates, alkali metal sulfates, alkali metal acetates, alkaline earth metal nitrates, alkaline earth metal carbonates, Alkaline earth metal sulfates, alkaline earth metal acetates, barium nitrate, barium acetate, barium chloride, strontium nitrate, strontium acetate, strontium chloride, antimony nitrate, antimony acetate, lead nitrate, lead carbonate, lead sulfate, lead acetate, nitric acid Lanthanum, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, potassium nitrate, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride, cesium sulfate, hydroxide Cesium, calcium nitrate, calcium chloride, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride, and erbium sulfate. 19. An optical fiber preform made by the following process: a) delivering the non-aqueous liquid reactant and aqueous solution to the burner assembly; b) discharging said non-aqueous liquid reactant and said aqueous solution from said burner assembly into a flame in the form of an aerosol comprising a plurality of non-aqueous liquid reactant droplets and a plurality of aqueous solution droplets; c) reacting said plurality of non-aqueous liquid reactant droplets and said plurality of aqueous solution droplets in said flame to produce soot; d) Depositing the soot onto a target. 20. A method for preparing soot for making an optical fiber preform, the method comprising the steps of: a) atomizing the aqueous solution with a gas in the first burner assembly to form an aerosol comprising a plurality of liquid droplets having a particle size of about 10-200 microns; b) Vaporize the reactants and deliver them to the second burner assembly; c) reacting the vaporous reactants and the aerosol within the combustion zone adjacent the first and second burner assemblies to form at least one soot stream. twenty one. 20. The method of claim 20, wherein said reactant is selected from the group consisting of halide-based silicon-containing compounds and non-halide silicon-containing compounds. twenty two. The method of claim 20, wherein said aqueous solution contains a salt selected from the group consisting of: alkali metal nitrates, alkali metal carbonates, alkali metal sulfates, alkali metal acetates, alkaline earth metal nitrates, alkaline earth Metal carbonates, alkaline earth metal sulfates, alkaline earth metal acetates, barium nitrate, barium acetate, barium chloride, strontium nitrate, strontium acetate, strontium chloride, antimony nitrate, antimony acetate, lead nitrate, lead carbonate, lead sulfate , lead acetate, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, potassium nitrate, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride, Cesium Sulfate, Cesium Hydroxide, Calcium Nitrate, Calcium Chloride, Aluminum Nitrate, Sodium Nitrate, Sodium Chloride, Erbium Chloride, and Erbium Sulfate.

Images