Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—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]
  • C03B37/01413—Reactant delivery systems
• • 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]
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
  • C03B19/1415—Reactant delivery systems
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2207/00—Glass deposition burners
  • C03B2207/30—For glass precursor of non-standard type, e.g. solid SiH3F
  • C03B2207/32—Non-halide
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2207/00—Glass deposition burners
  • C03B2207/80—Feeding the burner or the burner-heated deposition site
  • C03B2207/81—Constructional details of the feed line, e.g. heating, insulation, material, manifolds, filters

Definitions

• the present invention relates to silica feedstock compositions. More particularly, the present invention relates to silica forming feedstocks, and the methods of manufacturing optical waveguide preforms.
• Such processes involve the production of metal oxides from a variety of feedstocks. Such processes require a feedstock and a means of catalyzing oxidation and combustion of the feedstock to convert the feedstock into finely divided aggregates called soot. This soot can be heat treated to form a high purity glass article. This process is usually carried out using specialized conversion site equipment including flame generating burners.
• silicon tetrachloride has been used as the main silicon containing feedstock that is converted to silica.
• This use of silicon tetrachloride as the silica in forming feedstock provides a high purity silica glass and has been the commercially preferred method of manufacturing silica glass for use in optical waveguide products and particularly the manufacturing of optical waveguide fibers and their preforms.
• Organometallic siloxane compounds such as octamethylcyclotetrasiloxane have been used in the manufacture of silica glass to avoid the byproduction of HC1.
• organometallic siloxane compounds such as octamethylcyclotetrasiloxane and chlorides such as GeCl 4 are chemically incompatible with each other in the vapor phase and can form particulates in the vapor transport system if mixed together before oxidation and that it is desirable to keep the vapor streams separated.
• U.S. Patent No. 5,296,012 discloses a complicated multiple burner method of making Ge0 2 doped silica glass with separate feedstock vapor streams wherein octamethylcyclotetrasiloxane vapor is delivered to a first burner and GeCl 4 vapor is delivered to a separate second burner.
• Another prior art method kept the organometallic compound vapors separated from the dopant halide compound in separate and different delivery conduits, such as a tube with a tube, until they exited the face of a combustion burner having multiple concentric fume tubes.
• Such a method produced a gas stream containing the organometallic compound vapor and the dopant halide compound vapor after delivery to the conversion site combustion burner, with the compounds mixing together after exiting the conversion site combustion burner face, and just prior to entering the flame of the burner.
• Such prior art methods are complicated and pose production problems .
• the present invention is directed to a silica forming feedstock and metho ⁇ of forming optical waveguides and optical waveguide preforms that substantially obviates one or more of the problems due to limitations and disadvantages of tne related art.
• the principal advantage of the present invention is to provide a silica forming feedstock fluid which produces a germanium doped silica glass whicn allows for convenient manufacturing of optical waveguides and preforms thereof without the production of large amounts oi hazardous HC1 while providing the benefits of using chloride dopant precursors .
• the invention is a silica forming feedstock fluid including a high purity siloxane fluid and a high purity germanium chloride fluid, witn the siloxane fluid preferably comprised of at least 95. by weight of octamethylcyclotetrasiloxane; preferably said germanium chloride fluid is comprised of at least 99. by weight of germanium tetrachloride.
• the silica forming feedstock fluid is a vapor mixture maintained at a temperature ranging from approximately 175°C to 200°C.
• the invention includes a method of using the inventive feedstock fluid m the formation of optical waveguide preforms and optical waveguides; preferably the method includes the steps of mixing a high purity siloxane with a high purity germanium chloride m a ratio ranging from 1-10 parts by weight of said siloxane to 1 part by weight of said germanium chloride to provide a fluid feedstock, delivering said fluid feedstock through a heated supply conduit having a temperature ranging from approximately 175°C to 200°C to a conversion site, converting said delivered fluid feedstock into germanium doped silica soot, depositing said germanium doped silica soot on a deposition surface, and forming said deposited germanium doped silica soot into an optical waveguide preform.
• the siloxane is comprised of at least 95 o by weight of octamethylcyclotetrasiloxane.
• the germanium chloride is comprised of at least 99o by weight of germanium tetrachloride.
• the method includes the step of expelling said delivered fluid feedstock through the center tube of a conversion site ourner, said center tube surrounded by an inner shield of 2, an outer shield of ⁇ ⁇ and an outer ring of O2 and fuel.
• the method includes the step of maintaining said fluid feedstock at a temperature ranging from approximately 190°C to 200°C prior to converting said feedstock into germanium doped silica soot.
• the invention includes the making of optical waveguide preforms, which are predecessors and physical embodiments of an optical /vaveguide product prior to the final forming of the preform into the optical waveguide produc 1" , such as by drawing a preform into an optical waveguide fiber.
• the invention includes the forming of optical waveguide preforms by such processes as depositing, cladding, drying, consolidating, stretching, caning, overcladding, and reconsolidating.
• the invention includes a method of making optical fiber by converting a siloxane and germanium chloride feedstock fluid into a Ge ⁇ 2 doped silica glass.
• the method of making an optical waveguide fiber comprises the steps of: providing a first fluid feedstock comprised of octamethylcyclotetrasiloxane and germanium tetrachloride, delivering said first fluid feedstock through a heated supply conduit having a temperature ranging from approximately 175°C to 200°C to a conversion site, converting said delivered first fluid feedstock into Ge ⁇ 2 doped Si ⁇ 2 soot, depositing said Ge ⁇ 2 doped Si ⁇ 2 soot on a deposition surface, providing a second fluid feedstock comprised of octamethylcyclotetrasiloxane, delivering said second fluid feedstock through a heated supply conduit having a temperature ranging from approximately 175°C to 200°C to a conversion site, converting said delivered second fluid feedstock into Si ⁇ 2 soot, depositing said Si ⁇ 2 soot over said deposited Ge ⁇ 2 doped Si ⁇ 2 soot, forming said deposited Si ⁇ 2 soot and said deposited Ge ⁇ 2 doped Si ⁇ 2 soo
• the invention includes an optical waveguide preform manufacturing apparatus comprised of: a conversion site wherein a fluid feedstock delivered to said conversion site is converted into germanium doped silica; a means for providing a fluid feedstock comprised of a siloxane and a germanium chloride; a means for delivering said provided fluid feedstock to said conversion site; wherein said means for providing said fluid feedstock includes a means for mixing said germanium chloride with said siloxane prior to delivering to said conversion site and said means for delivering said provided fluid feedstock includes a means for heating said fluid feedstock, preferably wherein said means for heating said fluid feedstock comprises a heated delivery conduit.
• FIG. 1 comprises a schematic representation of the method and apparatus set up of the invention.
• FIG. 2 is a conversion site burner embodiment used in practicing the invention.
• the silica forming feedstock fluid of the invention includes a high purity siloxane and a high purity germanium chloride.
• the siloxane component of the feedstock fluid is a polyalkysiloxane, more preferably a cyclic polyalkysiloxane, and most preferably octamethylcyclotetrasiloxane [SiO (CH 3 ) 2 ] 4 •
• the high purity siloxane is at least 95% by weight octamethylcyclotetrasiloxane, and more preferably at least 98% by weight octamethylcyclotetrasiloxane, and most preferably at least 99.
• the high purity germanium chloride is germanium tetrachloride (GeCl ) .
• chlorinated germanium compounds may be used as alternatives to the preferred GeCl - Trimethylgermanium chloride [ (CH ,ClGe] and Methyltrichlorogermane (CH ⁇ Cl ⁇ Ge) are examples of such chlorinated germanium compounds.
• the high purity germanium chloride is at least 99% by weight germanium tetrachloride, and more preferably contains less than 10 ppb (parts per billion) each of Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Ti, V and a combined maximum total of these less than 25 ppb, and less than 5 ppm (parts per million) OH, less than 1 ppm CH, and less than 1 ppm H 1.
• the preferred silica forming feedstock fluid of the invention is a vapor mixture of octamethylcyclotetrasiloxane and germanium chloride, with a further preferred vapor mixture including oxygen to improve the conversion of the feedstock into Ge0 2 doped Si0 2 soot at the conversion site burner flame.
• the silica forming feedstock fluid vapor mixture of octamethylcyclotetra- siloxane and germanium chloride should be maintained at a temperature of at least 175°C, preferably at least 185°C, and more preferably at least 190°C. Preferably this vapor mixture should be maintained at a temperature no greater than approximately 200°C. These elevated temperatures provide for the silica forming feedstock fluid vapor mixture to remain in the vapor state for efficient delivery to the conversion site burner without complications. It is preferred that the temperature not be too high in order to avoid any adverse reactions prior to reaching the conversion site flame.
• the silica forming feedstock fluid consists essentially of a siloxane and germanium chloride, preferably with octamethylcyclotetrasiloxane as the siloxane and germanium tetrachloride as the germanium chloride.
• the optical waveguide silica feedstock fluid consists of octametr.ylcylotetra- siloxane and germanium chloride.
• FIG. 1 An exemplary schematic representation of the method of making an optical waveguide preform utilizing the inventive fluid feedstock is shown in FIG. 1.
• the inventive method of making an optical waveguide preform includes the steps of providing a fluid, preferably vapor, feedstock comprised of a high purity siloxane and a high purity germanium chloride and delivering the fluid feedstock through a heated supply conduit having a temperature ranging from about 175°C to 250°C, to maintain the feedstock temperature in this range, to a conversion site.
• a siloxane liquid which comprises the siloxane component of the feedstock is contained in siloxane liquid container 20.
• Controllable pump 22 delivers siloxane liquid through conduits and valve 24 to siloxane vaporizer 26.
• Means 28 for supplying a controllable flow of N 2 (nitrogen) carrier gas provides nitrogen carrier gas which aids in the vaporization of the siloxane liquid and delivery of the siloxane vapor to conversion site 30, which preferably is comprised of a burner and a conversion flame.
• Siloxane vapors are delivered through heated siloxane vapor conduit 32, which is preferably stainless steel tubing heated and maintained at 190°C.
• oxygen is added to the siloxane vapor to assist the conversion of the fluid feedstock.
• oxygen supply means 34 supplies a controllable amount of oxygen vapors which are heated to an elevated temperature, preferably about 200°C. Heated oxygen from conduit 36 is added to the siloxane vapor flowing to conversion site 30 at oxygen addition junction 38.
• Germanium chloride vapors from germanium chloride vapor conduit 40 are mixed with the siloxane vapors at germanium chloride addition junction 42.
• the mixing of germanium chloride vapors with siloxane vapors provides the homogeneous fluid feedstock comprised of siloxane and germanium chloride.
• Germanium chloride vapors are provided through conduit 40 by a means for controllably supplying germanium chloride such as germanium chloride vaporizer 44 which comprises a heated container of liquid germanium chloride 48 and an oxygen supply 46 wherein oxygen is bubbled through the liquid germanium chloride to assist in the formation of germanium chloride vapors.
• Valves 24 provide a means for controlling the amount of germanium chloride delivered through conduit 40 and mixed with siloxane vapors at junction 42.
• liquid germanium chloride in container 48 is heated to 45°C and germanium chloride vapor conduit 40 is maintained at 190°C.
• the mixture of siloxane vapor and germanium chloride vapor fluid feedstock s provided and delivered through heated burner supply conduit 50, which is heated to 190°C, to the single fume tube of burner 52, along with the oxygen and nitrogen gases.
• Burner face 51 of burner 52 is shown m FIG. 2.
• Conversion site 30 includes conversion site flame 68 produced by conversion site burner 52.
• the fluid vapor feedstock of siloxane and germanium chloride vapors delivered to conversion site 30 is converted by conversion site flame 68 into germanium (GeO ) doped silica (S ⁇ O_) soot.
• the germanium doped silica soot is then deposited on deposition surface 70.
• the deposited germanium doped silica soot is collected or deposition surface 70 which may comprise a rotating oait rod.
• the deposited doped soot forms the core of an optical waveguide preform.
• Forming the deposited germanium doped silica soot includes the steps of overcladdmg the germanium doped silica soot core preform with silica soot, removing the bait rod, and consolidating the porous soot preform into a nonporous soot preform.
• the step of providing a flu_.d feedstock comprised of a high purity siloxane and a high purity germanium chloride preferably comprises the step of providing a fluid feedstock of octamethylcyclotetrasiloxane and germanium tetrachloride, and more preferably comprises the step of mixing vapors of octamethylcyclotetrasiloxane and germanium chloride prior to being delivered to conversion site 30 and burner 52.
• oxygen is mixed with the vapors of octamethylcyclotetrasiloxane and germanium chloride.
• the steps of providing and delivering a fluid feedstock of siloxane and germanium chloride preferably include the step of maintaining the fluid feedstock at a temperature range of about 175°C to 200°C, more preferably 190°C to 200 C C, preferably by heating tie feedstock delivery supply conduits.
• the step of forming the deposited germanium doped silica soot into an optical waveguide preform includes the step of cladding the germanium doped silica soot with silica (S O_) soot.
• the step of cladding with silica soot includes the steps of providing a fluid feedstock of siloxane, delivering the fluid siloxane feedstock to conversion site 30 through heated supply conduits, converting the delivered fluid siloxane feedstock into silica soot, and depositing the silica soot on top of the germanium doped silica soot.
• the invention includes the method of making an optical waveguide fiber which includes the steps of providing a fluid feedstock comprised of siloxane and germanium chloride, delivering the fluid feedstock to a conversion site, converting the delivered fluid feedstock into germanium (Ge0 2 ) doped silica (S ⁇ 0 2 ) "-not, depositing the GeO_ doped S ⁇ 0 2 soot on a deposition surface, forming the deposited Ge0 2 doped SiO soot into an optical waveguide preform, and drawing the optical waveguide preform into a fiber.
• the fluid feedstock of siloxane and germanium chloride which may further include oxygen and the nitrogen (N 2 ) carrier gas, is delivered through heated delivery conduit 50 to the center fume tube 60 of burner 52.
• the fluid feedstock of siloxane and germanium chloride is delivered through center fume tube 60 to conversion site flame 68.
• Conversion site flame 68 and the conversion of the fluid feedstock into GeO doped S ⁇ O_ soot is maintained by delivering nitrogen (N_ gas to inner shield 62, oxygen (0_) gas to outer shield 64, and a premixture of 0 2 and fue_, preferably CH 4 , to fuel-oxygen outer ring 66.
• Inner shield N_ supply 58 provides N_ gas, preferably heated and maintained at about 200°C, to nitrogen inner shield 62.
• Outer shield 0_ supply 54 provides 0_ gas to oxygen outer shield 64.
• Pre ix fuel- oxygen supply 56 provides a mixture of oxygen and fuel, preferably CH 4 , to fuel-oxygen outer ring 66. This provides for a beneficial conversion of the siloxane and germanium feedstock into GeO_ doped SiO soot.
• the method of the invention includes the step of depositing the Ge0 2 doped S ⁇ 0 2 soot on a deposition surface. The GeO t doped S ⁇ 0 2 soot is deposited and collected on deposition surface 70 of bait rod 72 to form the preform of an optical waveguide core. When a sufficient amount of Ge0 2 doped S ⁇ 0 2 soot is deposited on the deposition surface to form an optical waveguide core, the delivery of the germanium chloride and siloxane fluid feedstock mixture to burner 52 is halted.
• the method of the invention further includes the step of forming the deposited GeO ⁇ doped S ⁇ 0 2 soot into an optical waveguide preform.
• Siloxane fluid 20 can be delivered to burner 52 m place of the feedstock mixture of siloxane and germanium chloride in order to form a cladding over the deposited Ge0 2 doped SiO soot.
• Siloxane delivery can operate m the same manner as the germanium chloride and siloxane vapor feedstock mixture delivery system but only deliver siloxane, preferably octamethylcyclotetrasiloxane, 0_, and N 2 to burner 52 which is converted at conversion site 30 by flame 68 into undoped S ⁇ O_ soot. This undoped S ⁇ 0 2 soot is deposited over the Ge0 2 doped S ⁇ 0 2 soot to form the preform of the optical waveguide cladding.
• the porous soot optical waveguide preform which has formed around the bait rod is removed from the bait rod.
• the porous soot preform is dried in a helium and chlorine atmosphere and sintered into a clear, f_.lly dense consolidated glass cylindrical optical wavegui ⁇ e preform that is comprised of a GeO doped silica waveguiding core structure surrounded by a silica cladding structure.
• This consolidated preform is stretched into an optical waveguide cane preform.
• This preform is overcladded with additional undoped silica soot such as produced during the formation of the cladding soot.
• the overcladded preform is reconsolidated and may be drawn into an optical waveguide fiber.
• FIG. 1 and 2 were used to produce Ge0 2 doped Si0 2 soot in accordance with the following table.
• High purity liquid octamethylcyclotetrasiloxane which was comprised of at least 95% by weight of octamethylcyclotetrasiloxane was pumped from container 20 to inclined plane flash vaporizer 26 which was heated above the boiling point of octamethylcyclotetrasiloxane .
• the octamethylcyclotetrasiloxane vapors were delivered towards conversion site 30 by the nitrogen carrier gas from N_ supply 28.
• Delivery supply conduits 32, 50, and 40, and delivery conduit junctions 38 and 42 comprised stainless steel tubing that was heated to 190°C. F ⁇ .
• GeCl vaporizer 44 comprised a GeCl bubbler.
• High purity liquid GeCl comprised of at least 99% by weight of GeCl 4 contained in container 48 was heated to 45°C and 0 2 from 0 2 source 46 was bubbled through the heated liquid GeCl .
• the amount of GeCl_ vapor produced could be controlled by changing the flow rate of 0 through the bubbler.
• This fluid feedstock vapor mixture was delivered to conversion site flame 68 through center fume tube 60 of burner 52. This delivered fluid feedstock was converted into Ge0 doped Si0 2 soot by conversion site flame 68 and deposited on deposition surface 70. GeO_ doped S ⁇ 0 soot was produced using the following conditions table:
• This method was able to produce germanium doped silica soot doped with about 7% to 36% Ge0 2 by weight.
• the preferred weight ratio of octamethylcyclotetrasiloxane to germanium tetrachloride of the feedstock is in -the range of 1.5-7.5 parts of octamethylcyclotetrasiloxane to 1 part germanium tetrachloride, and more preferred 1.9-3.6 parts of octamethylcyclotetrasiloxane to 1 part germanium tetrachloride.
• the preferred delivery rates to provide the fluid feedstock is about 6-10 grams/mm .

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• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacture, Treatment Of Glass Fibers (AREA)
• Glass Melting And Manufacturing (AREA)

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• 1998
  • 1998-06-24 JP JP2000501993A patent/JP2001509469A/ja not_active Withdrawn
  • 1998-06-24 WO PCT/US1998/013401 patent/WO1999002459A1/en not_active Application Discontinuation
  • 1998-06-24 CA CA002288769A patent/CA2288769A1/en not_active Abandoned
  • 1998-06-24 EP EP98935493A patent/EP0996597A1/en not_active Withdrawn
  • 1998-06-24 CN CN98805831A patent/CN1259109A/zh active Pending
  • 1998-06-24 AU AU84730/98A patent/AU743831B2/en not_active Ceased
  • 1998-06-24 KR KR1020007000150A patent/KR20010021592A/ko not_active Application Discontinuation
  • 1998-06-24 BR BR9810379-2A patent/BR9810379A/pt not_active IP Right Cessation
  • 1998-06-24 ID IDW20000242A patent/ID24873A/id unknown
  • 1998-07-07 TW TW087111179A patent/TW460424B/zh not_active IP Right Cessation

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