MXPA01004298A - Methods of manufacturing soot for optical fiber preforms and preforms made bythe methods - Google Patents

Abstract

The present invention is directed to methods of producing soot used in the manufacture of optical waveguides. Both non-aqueous liquid reactants and aqueous solutions containing one or more salts are delivered through an atomizing burner assembly to form a homogenous soot stream containing the oxides of the selected elements contained within the non-aqueous liquid reactant and the aqueous solution. The resulting multi-component soot is collected by conventional methods to form preforms used in the manufacture of optical waveguide fibers. Alternatively, an aqueous solution may be atomized with a gas at a first burner assembly to form an aerosol and a reactant vaporized for delivery to a second burner assembly. Preforms produced by the methods are also disclosed. The aqueous solution is preferably one comprising a metal salt, e.g. acetate, nitrate, sulfate, carbonate, chloride, hydroxide. The metal of the metal salt is preferably an alkali metal, an alkaline earth metal, lead, lanthanum, cobalt, antimony, erbium, aluminum, neodymium, praeseodymium.

Description

METHODS FOR ELABORATING HOLLIN FOR PREFORMS OF OPTICAL FIBER AND PREFORMS PREPARED FROM THESE METHODS FIELD OF THE INVENTION The present invention relates to the formation of soot used in the manufacture of glass and, in particular, to a method for supplying liquid precursors and other reagents in a flame to create soot for use in the preparation of optical waveguides, and guides of optical wave elaborated by this method. Although the invention is subject to a wide range of applications of glass soot, it is particularly suitable for the deposition of soot on a lens to form preforms used in the manufacture of optical fibers, and will be particularly described with said relationship.

BACKGROUND OF THE INVENTION Various processes are known in the art involving the production of oxides, and particularly, metal oxides from vaporous reactants. Such processes require a precursor or solution of supply materials, a means for generating and transporting vapors from the solution of supply materials (referred to from this. moment as vaporous reagents) and an oxidant to a reaction site for conversion (also known to those skilled in the art as a soot reaction zone or combustion zone), and a means to catalyze oxidation in a co-incidental manner to produce spherical aggregates finely divided, called soot. This soot can be collected in various ways, ranging from capture in a collection chamber to deposition on a rotating mandrel. The collected soot can be heat treated simultaneously or subsequently to form a non-porous, transparent, high purity glass article. Usually, this procedure is carried out with specialized equipment having a unique arrangement of nozzles, injectors, burners and / or burner assemblies. A large part of the initial research that led to the development of such procedures focused on the production of voluminous silica. Proper selection of supply materials was an important aspect of such work. Consequently, at that time it was determined that a material capable of generating a vapor pressure of 200 to 300 millimeters of mercury (mm Hg) at temperatures below about 100 ° C would be useful for making such bulky silicas. The high vapor pressure of silicon tetrachloride (SiCl) suggested its usefulness as a source of steam suitable for soot generation and prompted the discovery and use of a series of similar supply materials based on chloride. This factor, more than any other, is responsible for the currently accepted use of SiCU, GeC.4, POCI3, and BCI3 as steam sources of supply materials. However, the use of these and other supply materials based on halides as sources of steam has its drawbacks. The primary drawback is the formation of hydrochloric acid (HCl) as a byproduct of oxidation. HCl is not only harmful to the deposition substrates and the reaction equipment, but also to the environment. Solving this drawback, among others, leads to the use of halide-free compounds as precursors or supply materials for the production of soot for optical waveguides. Although the use of halide-free silicon compounds as sourcing materials for the production of fused silica glass, as described in U.S. Patent Nos. 5,043,002 and 5,152,819, for example, prevents the formation of HCl, other problems remain, particularly when soot has been created for the formation of optical waveguides. It has been found that, during the supply of vaporized polyalkylsiloxane to the burner, high molecular weight species can be deposited as gels in the lines that transport the vaporous reactants to the burner., or within the same burner. This produces a reduction in the rate of deposition of the soot which subsequently consolidates in a preform from which an optical waveguide fiber is extracted. It also causes imperfections in the preform which often produces useless and / or defective optical waveguide fibers from the portions made of the preform. A further problem that occurs while forming silica soot using a siloxane sourcing material is the deposition of particles having high molecular weights and high boiling points in the optical waveguide fiber preform. The accumulation of these particles results in "defective" or "cumulative defects" imperfections that adversely influence the optical and structural quality of the optical waveguides formed using the silica soot. Other supply materials, some of which are useful, and others may be so, in the formation of soot for the production of optical waveguides are not currently acceptable alternatives in the halide-free and halide-based supply materials for the supply by vapor deposition. Materials such as salts and those known as rare earth elements, for example, are extremely unstable as vapors and often decompose before they can be supplied to their vapor phase. Instead of being supplied from the burner as a vapor, these elements tend to form solids that level the solution. Although it is often possible to supply at least a percentage of these elements to the combustion zone as steam, it is technically very difficult. Elaborate systems that incorporate equipment that have very high costs are necessary to convert these elements to the steam phase, and, in addition, supply them to the combustion zone without leaving solids deposits in the lines that reach the burners and in the same burners . Additionally, if multiple elements are supplied as vapors and a specific percentage of each is necessary for the desired composition, it is difficult to control the supply to provide such a percentage, since different elements have different vapor pressures. The patent application E.U.A. with serial number 08 / 767,653, it discloses that these and other limitations can be overcome by supplying supply materials to an injector or burner in liquid form, atomizing the supply materials to form an aerosol containing small liquid drops of supply materials, and converting the liquid supply materials atomized in soot in the combustion zone. The injectors, burners, and burner assemblies described in patent application E.U.A. with serial number 08 / 767,653 are based on very small holes to supply the liquid in a fine stream for proper atomization. Because the supply materials are delivered directly to the burner flame as liquids instead of vapors, the vapor pressures of the supply materials are no longer limiting factors for supply. In this way, various elements can currently be supplied as supplying or doping materials to form soot for use in the preparation of optical waveguides. However, various elements, particularly those that are typically classified as salts, are not readily supplied to a flame in liquid form as an organometallic compound. Frequently, the purity requirements are extremely high, as well as the costs associated with the attempt to obtain compounds of the required purity. Therefore, there is a need for a method for making soot to be used in the preparation of optical waveguides, and particularly preforms for optical waveguide fibers that allow the user to accurately control the amount of elements that will be supplied., and at the same time eliminate the gelling in the supply lines. Additionally, a liquid supply method that produces a glass soot containing metal oxide, traditional dopants and salts in the required stoichiometry without expensive and elaborate equipment is necessary.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to a method for supplying liquids and other reagents to a combustion zone adjacent to a burner assembly to produce soot for use in glassmaking. In a liquid supply system, a liquid reagent, which can be converted by thermal oxidant decomposition to a glass, is provided and is introduced directly into the combustion zone of a combustion burner, thereby forming finely divided amorphous soot. Examples of such liquid delivery systems are described in the patent application E.U.A. with serial No. 08 / 767,653 filed on December 17, 1996, and entitled "Method and Apparatus for Forming Fused Silica by Combustion of Liquid Reactants"; patent application E.U.A. with serial No. 08 / 903,501, filed July 30, 1997, entitled "Method for Forming Silica by Combustion of Liquid Reactans Using Oxygen"; patent application E.U.A. with serial No. 09 / 089,869, filed on June 3, 1998, and entitled "Method and Apparatus for Forming Silica by Combustion of Liquid Reactants Using a Heater"; provisional application E.U.A. with serial No. 60 / 068,955, filed December 19, 1997, entitled "Burner and Method for Producing Metal Oxide Soot"; and the provisional application E.U.A. filed on July 31, 1998, and entitled "Method and Apparatus for Forming Soot for the Manufacture of Glass", the specifications of which are incorporated herein by reference. The amorphous soot can be captured in various ways, but typically is deposited on a receptor surface where, either substantially simultaneously or subsequent to its deposition, the soot consolidates into a fused glass body. The glass body can then be used to make products directly from the fused body, or the fused body can be further processed, for example by forming an optical waveguide by extraction to make the optical waveguide fiber, for example as further described in the US patent application No. 08 / 574,961 entitled "Method for Purifying polyalkylsiloxane and the Resulting Products", the specification of which is incorporated herein by reference. The method of the present invention provides several advantages over other glass soot production methods known in the art. The present invention provides the ability to accurately vary and control the composition of the produced soot, which in turn provides the optical waveguide fibers with well-defined index profiles and high accuracy, in addition to other features. The present invention also provides the industry with a method for concurrently supplying the largest number of elements to a flame to produce a multi-component glass soot. Any number of organometallic elements, rare earth elements, and now salts all can be supplied concurrently to a flame to produce homogeneous soot. Similarly, these elements can be supplied concurrently or selectively during the same soot production to produce a preform that meets the specific requirements of layering. In this way, a fiber optic preform made by the method of the present invention has the advantage of containing precise amounts of elements, some of which have never been combined within a single optical waveguide fiber preform. To achieve these and other utilities, a non-aqueous liquid reagent and an aqueous solution are atomized to form an aerosol made of numerous liquid droplets. The aerosol is supplied to the combustion zone and reacted in the flame of the combustion zone to form finely divided glass soot particles. In another aspect of the invention, a non-aqueous liquid reagent and an aqueous solution are supplied to a burner assembly. The non-aqueous liquid reagent and the aqueous solution are discharged from the burner assembly in a flame, where they are reacted to form soot. The soot is deposited on a target to form a preform. In a further aspect of the present invention, an optical fiber preform is formed by the process of supplying a non-aqueous liquid reagent and an aqueous solution to a burner assembly. The non-aqueous liquid reagent and the aqueous solution are discharged from the burner assembly into the flame as an aerosol formed from a plurality of drops of non-aqueous liquid reagent and a plurality of drops of liquid aqueous solution. The drops are reacted in the flame to produce soot and the soot is deposited on a target to form the preform. In a further aspect of the invention, the supply of an aqueous solution is combined with a conventional steam supply. The aqueous solution is atomized with a gas in a burner assembly to form an aerosol made from several liquid drops and another reagent is vaporized to supply it to the burner assembly. The vaporous reagent and the aerosol are reacted in a combustion zone adjacent to the burner assembly to form finely divided glass soot.

Additional features and utilities of the invention will be set forth in the detailed description, below, and in part will be apparent from the description or may be learned by practicing the invention. Those skilled in the art will understand that both the general description and the following detailed description are exemplary and explanatory in nature and were created to provide a further explanation of the invention as claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated and constitute a part of the present specification. The drawings illustrate various embodiments of the invention, and together with the description, function to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically describes a first preferred embodiment of a liquid delivery system used in the method of the present invention. Figure 2 schematically illustrates a second preferred embodiment of a liquid delivery system used in the method of the present invention.

Figure 3 schematically illustrates a preferred embodiment of a steam and liquid delivery system used in the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Some techniques of soot deposition and soot collection are used in the production of glass products. While the present invention can be employed in several of these techniques, it is particularly suitable for those techniques used to deposit soot on a lens to form glass preforms used in the manufacture of optical waveguides, and specifically optical waveguide fibers. However, those skilled in the art will understand that the method of the present invention can also be used in the preparation of flat waveguides. During the processing of optical waveguide fibers, soot is typically deposited uniformly on or within a target. The collected soot is consolidated into a high purity glass preform and then subjected to additional processing steps, such as extraction to form a thin fiber that can transport and direct light. In this way, the present invention will be described in this regard. However, those skilled in the art of waveguide fibers will understand that there are other systems and variations of the described systems wherein the present invention can be incorporated to perform the functions described and claimed herein. Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated schematically in the accompanying drawings. In FIG. 1, a first preferred embodiment of the system for supplying liquids in a combustion zone to form multi-component soot for use in glass making is illustrated schematically. The liquid delivery system 10 includes a reservoir 12 for an aqueous solution, which contains an aqueous solution 14, a reservoir 16 for aqueous liquid reagents, which contains a non-aqueous liquid reagent 18, and optionally, a reservoir 20 for dopants containing In addition, the liquid supply system 10 includes an atomizing burner assembly 26, such as an atomizing burner assembly and the associated delivery mechanisms (hereinafter referred to as "burner assembly") described in FIG. the US patent application with serial number 08 / 767,653, filed on December 17, 1996, entitled "Method and Apparatus for Forming Fused Silica by Combustion of Liquid Reactants"; patent application of E.U.A. with serial number 08 / 903,501, filed on July 30, 1997 entitled "Method for Forming Silica by Combustion of Liquid Reactants Using Oxygen"; the patent application of E.U.A. with serial number 09 / 089,869, filed on June 3, 1998, entitled "Method and Apparatus for Forming Silica by Combustion of Liquid Reactants Using a Heater"; provisional application of E.U.A. with serial number 60 / 068,255, filed on December 19, 1997, entitled "Burner and Method for Producing Metal Oxide Soot"; and provisional application of E.U.A. filed on July 31, 1998, and entitled "Method and Apparatus for Forming Soot for the Manufacture of Glass", the specifications of which are incorporated herein by reference. During operation, the aqueous solution 14, the non-aqueous liquid reagent 18, and the purifier 22 are mixed according to the desired stoichiometry and stored within the respective reservoirs, 12, 16 and 20. The aqueous solution 14 preferably contains a water-soluble salt such as an alkali metal nitrate, alkali metal carbonate, alkali metal sulfate, alkali metal acetate, alkalipto-earth metal nitrate, alkaline earth metal carbonate, alkaline earth metal sulfate or alkaline earth metal acetate. 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, lead sulfate, lead acetate, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, praseodymium chloride, nitrate potassium chloride, potassium chloride, nitrate, cesium nitrate, cesium chloride, cesium sulphate, cesium hydroxide, calcium chloride, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride and erbium sulfate, but it may contain other salts and / or other elements capable of being mixed and supplied as an aqueous solution. A non-aqueous liquid reagent 18 is preferably a liquid organometallic compound such as octamethylcyclotetrasiloxane, but may be a silicon alkoxide, a metal alkoxide or other silica matrix material made soluble with a suitable organic solvent, such as ethylene glycol monomethyl ether. The doping material 22, if used, may be ketones, alkoxides, acetates, β-diketonates or fluoro-β-diketonates of praseodymium, holmium, and thulium dissolved in a suitable organic solvent, such as ethylene glycol monomethyl ether. Typically, the preferred dopants 22 are erbium, germanium and other rare earth elements that have beneficial properties for use in the optical waveguide fibers. The aqueous solution 14, the non-aqueous liquid reagent 18, and if desired, the impurifier 22 are provided by liquid supply lines 24 to the burner assembly 26 in the desired quantities. The liquids 14, 18 and 22 are discharged from the burner assembly 26 in the flame 28 while liquid droplets 30 are atomized. The liquid droplets 30 are mixed uniformly in the atomization process and reacted in the flame 28 to produce a soot stream 32. The soot stream 32 is preferably directed toward a target, such as a rotating mandrel 34 while the burner assembly 26 traverses the length of the rotating mandrel 34, resulting in the deposition of soot on the mandrel. rotation 34, which at the time forms a homogenous soot body 36 containing the desired amounts of the oxides of the elements contained in the aqueous solution 14, the non-aqueous liquid reagent 18 and the doping 22. A second preferred embodiment of the system for supplying liquids in a combustion zone to form soothes of multiple components for use in the manufacture of glass is illustrated schematic As in the first preferred embodiment, the liquid delivery system 40 includes a reservoir 42 for aqueous solution for storing the aqueous solution 44, a reservoir 46 for the non-aqueous liquid reagent for storing a non-aqueous liquid reagent 48. , and optionally, a reservoir 50 for impurifier for storing a dopant 52. However, unlike the first preferred embodiment of the invention, a liquid delivery system 40 includes a first burner assembly 56 in selective fluid communication with a reagent reservoir 46 non-aqueous liquid and dopancy deposit 50, and a second burner assembly 66 in fluid communication with the aqueous solution tank 42. As described below, those skilled in the art will understand that the aqueous solution 44 and the non-aqueous liquid reagent 48 may include one or more of the compounds described in the preceding paragraphs with respect to the preferred embodiment of the present invention. In operation, the aqueous solution 44 is selectively supplied to a second burner assembly 66 and the non-aqueous liquid reagent 48, and the doping 52, if desired, are selectively supplied to the first burner assembly 56. The first burner assembly 56 discharges the atomized liquid droplets 60 into a flame 58, wherein the liquid droplets 60 are combusted to form a soot stream 62 which contains a homogeneous mixture of oxides produced from the oxidation of the elements. selected from within the non-aqueous liquid reagent 48 and the impurifier 52. The second burner assembly 66 may be activated concurrently or independently of the first burner assembly 56 to discharge atomized liquid droplets 70 into a flame 68 to form a homogeneous soot stream 72 that contains oxides of the element that is the result of the oxidation of elements contained in the aqueous solution 44. The soot stream 62 and 72 are preferably directed towards a target such as the rotation mandrel 74, and soot from the soot streams 62 and 72 are deposited on the rotation mandrel 74 in uniform layers, while the first assembly of burner 52 and second burner assembly 66 traverse the length of rotation mandrel 74. The resulting soot body 76 contains all the oxides of soot streams 62 and 72 in accordance with the speed at which they are supplied. The multiple burner assemblies of this embodiment of the present invention generally facilitate a higher rate of soot deposition than the first embodiment of the present invention. In addition, the separate arrangement of the burner assemblies 56 and 66 allows the soot to be deposited in separate layers that provide a controlled and cost-effective way to produce an optical waveguide having well-defined index profiles and other optical characteristics. Figure 3 schematically illustrates a preferred embodiment of a combined vapor and liquid delivery system 80 that is used in the practice of the method of the present invention. The combined steam and liquid supply system 80 includes a reservoir 82 for an aqueous solution for storing an aqueous solution 84 and a liquid supply line 90 for placing a first burner assembly 94 in communication with the aqueous solution 84. In addition, the combined steam and liquid supply system 80 includes a steam supply system 86 for supplying a vaporous reagent 88 through the liquid supply line 92 to a second burner assembly 96. The steam supply system 86 can any steam delivery system known in the art, for example, and without being limited thereto, the steam supply systems described in the US patent No. 5,043,002 and the US patent. No. 3,698,936, the specifications of which are incorporated herein by reference. Vaporized reagent 88 is preferably a halide-based supply material, for example, and without limitation thereto, SiCl 4, or a halide-free supply material, for example and without being limited thereto, octamethylcyclotetrasiloxane. The aqueous solution 14 preferably contains a water soluble salt such as 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 an alkaline earth metal acetate. 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, lead sulfate, lead acetate, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, nitrate potassium, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride, cesium sulphate, cesium hydroxide, calcium chloride, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride and erbium sulphate, but it may contain other salts and / or other elements that can be mixed and supplied as an aqueous solution. During operation, the aqueous solution 84 is selectively supplied to a burner assembly 94, and the vaporized reagent 88 is supplied to a second burner assembly 96. The aqueous solution 84 is atomized with a gas such as air, but preferably oxygen, or oxygen together with an inert gas such as nitrogen, in the first burner assembly 94 to form an aerosol formed by a plurality of liquid droplets ranging generally in size from about 10 microns to 200 microns. Most drops will typically have a size of 20 microns. The atomized liquid droplets 98 are discharged into a first flame 100 formed adjacent to the first burner assembly 94, wherein the atomized liquid droplets 98 are subjected to combustion to form a first soot stream 92 containing a homogeneous mixture of oxides produced from of the oxidation of the selected elements contained within the aqueous solution 84. The vaporous reagent 88 is supplied through a steam supply line 92 and the second burner assembly 96 as vapors 104 which discharge into the second flame 106 formed adjacent to the second burner assembly 96. The vapors 104 are subjected to combustion in a second flame 106 to form a second stream of soot 108 containing a homogeneous mixture of oxides produced from the oxidation of the selected elements contained within the reagent Vaporous 88. The first and second soot streams, -102 and 108 respectively, are directed towards a target, such as a rotating mandrel 110, and the soot within the soot streams 102 and 108 is deposited on the mandrel. rotation 110 in uniform layers while the first burner assembly 94 and the second burner assembly 96 traverse the length of the rotating mandrel 110. The resulting soot body 112 contains all the oxides of the first and second soot streams, 112 and 108 respectively, in accordance with the rate at which they are supplied. Although not shown in Figure 3, an additional burner assembly and associated delivery mechanisms may be incorporated in the system shown in Figure 3 to provide additional doping agents commonly used in soot processing for optical waveguide fibers . This embodiment of the present invention combines a higher rate of deposition of vapor deposition soot with the unique optical characteristics provided by salts supplied in an aqueous solution. Those skilled in the art will understand that the vaporous reagent 88 and the aqueous solution 84 can be supplied in a common flame to produce a homogeneous soot stream that can be collected in any manner already known in the art and then further processed to form optical waveguides and particularly preforms for optical waveguide fibers. Although not shown in the figures, those skilled in the art will understand that the systems illustrated schematically in Figures 1, 2 and 3, are not limited to the number of burner assemblies and associated supply mechanisms shown in the figures. . Each system may incorporate additional burner assemblies and associated delivery mechanisms to realize the methods of the present invention. In general, the greater the number of burner assemblies, the higher the rate of soot deposition. In addition, the present invention can be used in conjunction with other steam supply systems known in the art to provide greater flexibility in soot processing for optical waveguide fibers. It will be apparent to those skilled in the art that various modifications and variations may be made in the soot processing methods for the optical fiber preforms of the present invention without departing from the spirit or scope of the invention. In this manner, it is intended that the present invention cover the modifications and variations to the present invention as they fall within the scope of the appended claims and their equivalents. In addition, the structures, materials, acts and corresponding equivalents of all means or steps plus the elements of function in the claims below are intended to include any structure, material or act to perform the function together with other elements that are claimed from the way they are specifically claimed in the present.

Claims (22)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for making soot from which an optical fiber preform is made, said method comprises the steps of: a) atomizing a non-aqueous liquid reagent and an aqueous solution to form an aerosol comprising numerous liquid drops, b) supplying said aerosol in a combustion zone; and c) reacting said aerosol in a flame that is provided in said combustion zone to form finely divided glass soot particles.

2. The method according to claim 1, further characterized in that said non-aqueous liquid reagent comprises a non-aqueous solution.

3. The method according to claim 1, further characterized in that it comprises the step of supplying said non-aqueous liquid reagent and said aqueous solution to a single burner assembly before atomizing said non-aqueous liquid reagent and said aqueous solution.

4. The method according to claim 1, further characterized in that before step a), the method further comprises the steps of: supplying said non-aqueous liquid reagent to said first burner assembly and supplying said aqueous solution to a second assembly. of burner separated from said first burner assembly.

5. The method according to claim 4, further characterized in that it comprises the steps of: atomizing said non-aqueous liquid reagent in said first burner assembly to form a first aerosol; and atomizing said aqueous solution in said second burner to form a second aerosol.

6. The method according to claim 5, further characterized in that it comprises the steps of: reacting said first aerosol in a first flame produced adjacent to said first burner assembly; and reacting said second aerosol in a second flame produced adjacent to said second burner assembly.

7. The method according to claim 1, further characterized in that said non-aqueous liquid reagent comprises at least one precursor and at least one dopant.

8. The method according to claim 1, further characterized in that said liquid non-aqueous reagent comprises a siloxane, and wherein said aqueous solution comprises a salt.

9. The method according to claim 8, further characterized in that said salt is selected from the group consisting of alkali metal nitrate, alkali metal carbonate, alkali metal sulfate, alkali metal acetate, alkaline earth metal nitrate, carbonate alkaline earth metal, alkaline earth metal sulphate, alkaline earth metal acetate, 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 sulphate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, nitrate potassium, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride, cesium sulfate, cesium hydroxide, calcium nitrate, calcium chloride, aluminum nitrate io, sodium nitrate, sodium chloride, erbium chloride, and erbium sulfate.

10. The method according to claim 9, further characterized in that said non-aqueous liquid reagent further comprises a dopant.

11. A process for making an optical fiber preform, said method comprises the steps of: a) supplying a non-aqueous liquid reagent and an aqueous solution to a burner assembly; b) discharging said non-aqueous liquid reagent and said aqueous solution from said burner assembly in a flame; c) reacting said non-aqueous liquid reagent and said aqueous solution in said flame to produce soot; and d) depositing said soot on a rotating mandrel.

12. The method according to claim 11, further characterized in that step b) includes the step of atomizing said non-aqueous liquid reagent and said aqueous solution to form an aerosol comprising a plurality of non-aqueous liquid reagent drops mixed with a plurality of aqueous liquid drops of solution.

13. The method according to claim 12, further characterized in that the step of atomizing is performed while said non-aqueous liquid reagent and said aqueous solution is discharged from said burner assembly.

14. The method according to claim 11, further characterized in that said burner assembly comprises a first burner assembly and a second burner assembly separated from said first burner assembly, and wherein non-aqueous liquid reactant is discharged from said burner assembly. first burner assembly while a first aerosol comprises a plurality of non-aqueous liquid drops of reagent, and wherein said aqueous solution is discharged from said second burner assembly while a second aerosol comprises a plurality of aqueous liquid drops of solution.

15. The method according to claim 14, further characterized in that said flame comprises a first flame adjacent to said first burner assembly and a second flame adjacent said second burner assembly, and wherein said first spray is reacted at said first flame, and wherein said second spray is reacted in said second flame.

16. - The method according to claim 11, further characterized in that said non-aqueous liquid reagent comprises at least one precursor and at least one dopant.

17. The method according to claim 11, further characterized in that said liquid non-aqueous reagent comprises a siloxane, and wherein said aqueous solution comprises a salt.

18. The method according to claim 17, further characterized in that said salt is selected from the group consisting of alkali metal nitrate, alkali metal carbonate, alkali metal sulfate, alkali metal acetate, alkaline earth metal nitrate, carbonate alkaline earth metal, alkaline earth metal sulphate, alkaline earth metal acetate, 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 sulphate, lanthanum acetate, cobalt nitrate, cobalt acetate, cobalt chloride, neodymium nitrate, neodymium chloride, nitrate potassium, potassium chloride, praseodymium nitrate, cesium nitrate, cesium chloride, cesium sulfate, cesium hydroxide, calcium nitrate, calcium chloride, aluminum nitrate child, sodium nitrate, sodium chloride, erbium chloride and erbium sulfate.

19. A fiber optic preform formed by the method of: a) supplying a non-aqueous liquid reagent and an aqueous solution to a burner assembly; b) discharging said non-aqueous liquid reagent and said aqueous solution of said burner assembly into a flame as an aerosol comprising a plurality of non-aqueous liquid drops of reagent and a plurality of aqueous liquid drops of solution; c) reacting said plurality of non-aqueous liquid reagent drops and said plurality of aqueous liquid drops of solution in said flame to produce soot; and d) deposit said soot on a target.

20. A method for making soot from which an optical fiber preform is made, said method comprises the steps of: a) atomizing an aqueous solution with a gas in a first burner assembly to form an aerosol comprising a plurality of drops which have a size ranging from about 10 microns to 200 microns; b) vaporizing a reagent to supply it to a second burner assembly; and c) reacting the vaporous reagent and the aerosol within a combustion zone adjacent to the first and second burner assemblies to form at least one soot stream.

21. The method according to claim 20, further characterized in that said reagent is selected from the group consisting of halide-based silicon containing a compound and a silicon-containing compound without halide.

22. The method according to claim 20, further characterized in that said aqueous solution comprises a salt selected from the group consisting of alkali metal nitrate, alkali metal carbonate, alkali metal sulfate, alkali metal acetate, metal nitrate alkaline earth metal, alkaline earth metal carbonate, alkaline earth metal sulphate, alkaline earth metal acetate, barium nitrate, barium acetate, barium chloride, strontium nitrate, strontium acetate, strontium chloride, antimony nitrate, antimony acetate, nitrate lead, lead carbonate, lead sulfate, lead acetate, lanthanum nitrate, lanthanum carbonate, lanthanum sulphate, 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, chlorine calcium uro, aluminum nitrate, sodium nitrate, sodium chloride, erbium chloride and erbium sulfate.