WO2008038298A2 - Procédé pour préparer un mandrin adapté à produire une préforme de fibre optique sans défaut et préforme produite à partir de celui-ci - Google Patents
Procédé pour préparer un mandrin adapté à produire une préforme de fibre optique sans défaut et préforme produite à partir de celui-ci Download PDFInfo
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- WO2008038298A2 WO2008038298A2 PCT/IN2007/000306 IN2007000306W WO2008038298A2 WO 2008038298 A2 WO2008038298 A2 WO 2008038298A2 IN 2007000306 W IN2007000306 W IN 2007000306W WO 2008038298 A2 WO2008038298 A2 WO 2008038298A2
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- WIPO (PCT)
- Prior art keywords
- mandrel
- soot
- porous body
- preform
- soot porous
- Prior art date
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Classifications
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- 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]
- C03B37/01486—Means for supporting, rotating or translating the preforms being formed, e.g. lathes
- C03B37/01493—Deposition substrates, e.g. targets, mandrels, start rods or tubes
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- 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
- C03B19/1484—Means for supporting, rotating or translating the article being formed
- C03B19/1492—Deposition substrates, e.g. targets
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- 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]
- C03B37/01466—Means for changing or stabilising the diameter or form of tubes or rods
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
Definitions
- the present invention relates to a process for preparing a mandrel for producing flawless optical fiber preform and a fiber preform produced therefrom.
- the present invention relates to a process for eliminating defects, such as voids, bubbles, impurities from centerline of optical fiber preform and a fiber preform produced therefrom.
- the present invention relates to a process for preparing a mandrel suitable for producing a preform wherein the mandrel can be easily removed without causing any defects, such as voids, bubbles, impurities in the centerline of the preform thus produced.
- Optical fibers are inherently versatile as a transmission medium for all forms of information, be it voice, video or data.
- Optical fiber comprises a core, to which essentially the entire signal is confined, and a clad surrounding the core.
- the optical fiber is manufactured in a way to have core with higher refractive index than clad in order to achieve light transmission inside the core region.
- the optical power also spreads in the cladding region near the core region.
- optical fibers for telecommunication are required to operate with the lowest possible attenuation loss.
- the requirement for optical performance of optical fibers is stringent, the source of attenuation loss in optical fiber needs to be eliminated.
- certain physical constraints in the process for producing optical fiber preform, from which optical fiber is produced can result in increase in attenuation loss of the fiber and an important one of these physical constraints is formation of defects, such as voids, bubbles, impurities in the centerline of the preform when mandrel is removed to create a centerline in the preform.
- defects, such as voids, bubbles, impurities in the centerline of the preform have also been observed to propagate cracks and breaks in the optical fiber produced from such preform. Therefore, if defects, such as voids, bubbles, impurities are formed in the centerline of the preform on removal of mandrel it results in increase in attenuation loss of the fiber and may also result in formation of cracks and breaks in the fiber produced from such preform.
- US Patent No. 3,823,995 teaches a process for producing a preform having reduced formation of defects, such as voids, bubbles, impurities in the centerline of the preform thus produced by carefully removing the mandrel by grinding with the help of a diamond reamer, or by drilling the centerline while removing the mandrel followed by etching with the help of hydrofluoric acid.
- the main drawback of this method is that the grinding or drilling leaves rough surface in the centerline which requires further processing by laser milling, mechanical polishing and/or fire polishing of the centerline and/or washing the centerline with hydrofluoric acid before further processing to collapsing step.
- Still another prior art [US Patent No. 4,204,850] method teaches that the mandrel can be easily removed if it is coated with carbon before depositing the soot particles.
- the mandrel is coated with carbon by directly exposing the mandrel to acetylene flame or by directly dipping the mandrel in carbon slurry or by directly dipping in wax and then charring the mandrel.
- the main drawback of this method is that it still requires etching of capillary at sintered glass preform stage with hydrofluoric acid, which is not only time consuming, but also makes the overall process uneconomical for commercial application.
- The> another drawback of this method is that if coating is done by dipping in carbon slurry or by dipping in wax, then it requires additional step of drying in air for several hours which unduly makes the process highly time consuming.
- the need of time is to have a process for preparing a mandrel which is suitable for producing a preform wherein the mandrel can be easily removed without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced which should be capable of producing a fiber having very low attenuation loss and almost no cracks and breaks therein.
- the main object of the present invention is to have a process for preparing a mandrel for producing a preform wherein the mandrel can be easily removed without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced which is then capable of producing a fiber having very low attenuation loss and almost no cracks and breaks therein.
- Another object of the present invention is to have an optical fiber preform having no defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region thereof.
- Still another object of the present invention is to have an optical fiber having very low attenuation loss and almost no cracks and breaks therein.
- Yet another object of the present invention is to have a process for producing a preform wherein the mandrel can be easily removed without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced which is then capable of producing a fiber having very low attenuation loss and almost no cracks and breaks therein.
- Figure IA illustrates mandrel suspension means in accordance with one preferred embodiment of the present invention.
- Figure IB illustrates suspension tube of mandrel suspension means of present invention as illustrated in Figure IA.
- FIG 1C illustrates mandrel of mandrel suspension means of present invention as illustrated in Figure IA.
- Figure ID illustrates holding means of mandrel suspension means of present invention as illustrated in Figure IA.
- Figure IE illustrates closing means of mandrel suspension means of present invention as illustrated in Figure IA.
- Figure 2 shows a schematic representation of deposition process over a mandrel prepared in accordance with present invention to produce a soot porous body.
- Figure 3 shows a schematic representation of hollow soot porous body having centerline therethrough after removal of mandrel, prepared in accordance with present invention, from the soot porous body.
- Figure 4 shows a schematic cross-sectional view of hollow soot porous body having centerline therethrough after removal of mandrel, prepared in accordance with present invention, from the soot porous body.
- Figure 5 shows a schematic representation of hollow soot porous body in side the sintering furnace after removal of mandrel, prepared in accordance with present invention, from the soot porous body.
- Figure 6 shows a hollow soot porous body having centerline therethrough after removal of mandrel, prepared in accordance with present invention, from the soot porous body which is subjected to steps of dehydration, sintering and collapsing to produce a sintered [solid] glass preform.
- the optical fiber preform produced by the mandrel prepared in accordance with methods known in the prior art suffers from various drawbacks, disadvantages and limitations as described herein.
- the prior art methods as described herein have been observed to produce a preform wherein the mandrel cannot be easily removed from soot porous body without causing certain defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced, and hence, the preform thus produced cannot produce a fiber having very low attenuation loss, and almost no cracks and breaks therein.
- mandrel employed for producing a preform is preheated before depositing one or more coatings from a group consisting of carbon and soft soot before start of soot deposition to prepare soot porous body, then the mandrel can be easily removed from the soot porous body without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced which has been found to be suitable for producing a fiber having very low attenuation loss, and almost no cracks and breaks therein meaning thereby the above-described problems of the prior art methods can be overcome to a greater extent.
- the present invention relates to a process for preparing the mandrel suitable for producing flawless optical fiber preform, wherein the mandrel can be easily removed from the soot porous body without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced, which has been found to be suitable for producing a fiber having very low attenuation loss and, almost no cracks and breaks therein, wherein the process is characterized by heating the mandrel before the start of soot deposition to form a soot porous body having core and clad.
- the carbon coating is deposited on the heated mandrel before the start of soot deposition to form a soot porous body having core and clad.
- the present invention relates to a process for preparing the mandrel suitable for producing flawless optical fiber preform, wherein the mandrel can be easily removed from the soot porous body without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced, which has been found to be suitable for producing a fiber having very low attenuation loss and, almost no cracks and breaks therein f wherein the process is characterized by heating the mandrel and depositing carbon coating thereon before the start of soot deposition to form a soot porous body having core and clad.
- the soft soot coating is deposited on the heated mandrel ⁇ which is subsequently removed to have smooth and clean surface before the start of soot deposition to form a soot porous body having core and clad.
- the present invention relates to a process for preparing the mandrel suitable for producing flawless optical fiber preform, wherein the mandrel can be easily removed from the soot porous body without causing any defects, such as voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced, which has been found to be suitable for producing a fiber having very low attenuation loss and, almost no cracks and breaks therein, wherein the process is characterized by heating the mandrel and depositing coating of soft soot thereon which is subsequently removed to have smooth and clean surface of mandrel before the start of soot deposition to form a soot porous body having core and clad.
- the carbon coating and soft soot coating are deposited on the heated mandrel which are subsequently removed to have smooth and clean surface of mandrel before the start of soot deposition to form a soot porous body having core and clad.
- the present invention relates to a process for preparing the mandrel suitable for producing flawless optical fiber preform, wherein the mandrel can be easily removed from the soot porous body without causing any defects, such as > voids, bubbles, impurities, uncollapsed portion in the centerline region of the preform thus produced, which has been found to be suitable for producing a fiber having very low attenuation loss and, almost no cracks and breaks therein, wherein the process is characterized by heating the mandrel and depositing carbon coating followed by coating of soft soot thereon which are subsequently removed to have smooth and clean surface of the mandrel before the start of soot deposition to form a soot porous body having core and clad.
- the mandrel prepared in accordance with any one of the above embodiments is employed for producing soot porous body which is dehydrated, sintered and collapsed to produce flawless optical fiber preform [also referred to as mother preform].
- the process for producing flawless optical fiber preform comprises :- i) providing a cylindrical and tapered mandrel; ii) • depositing soot particles over said mandrel to form soot porous body having core and clad; iii) detaching said mandrel from the soot porous body to form hollow soot porous body; iv) dehydrating the hollow soot porous body in an environment suitable to completely remove the moisture therefrom; v) sintering and collapsing dehydrated hollow soot porous body inside the sintering furnace to form solid glass preform having collapsed capillary therein; characterized in that said mandrel is heated before the start of step of deposition of soot particles thereon.
- the process for producing flawless optical fiber preform comprises :- i) providing a cylindrical and tapered mandrel; ii) depositing soot particles over said mandrel to form soot porous body having core and clad; iii) detaching said mandrel from the soot porous body to form hollow soot porous body; iv) dehydrating the hollow soot porous body in an environment suitable to completely remove the moisture therefrom; v) sintering and collapsing dehydrated hollow soot porous body inside the sintering furnace to form solid glass preform having collapsed capillary therein; characterized in that said mandrel is heated and carbon coating is deposited thereon before the start of step of deposition of soot particles thereon.
- the process for producing flawless optical fiber preform comprises :- i) providing a cylindrical and tapered mandrel; ii) depositing soot particles over said mandrel to form soot porous body having core and clad; iii) detaching said mandrel from the soot porous body to form hollow soot porous body; iv) dehydrating the hollow soot porous body in an environment suitable to completely remove the moisture therefrom; v) sintering and collapsing dehydrated hollow soot porous body inside the sintering furnace to form solid glass preform having collapsed capillary therein; characterized in that said mandrel is heated and soft soot coating is deposited thereon, which is subsequently removed to have smooth and clean surface of mandrel before the start of step of deposition of soot particles thereon.
- the process for producing flawless optical fiber preform comprises :- i) providing a cylindrical and tapered mandrel; ii) depositing soot particles over said mandrel to form soot porous body having core and clad; iii) detaching said mandrel from the soot porous body to form hollow soot porous body; iv) dehydrating the hollow soot porous body in an environment suitable to completely remove the moisture therefrom; v) sintering and collapsing dehydrated hollow soot porous body inside the sintering furnace to form solid glass preform having collapsed capillary therein; characterized in that said mandrel is heated, and carbon coating and soft soot coating are deposited thereon, which are subsequently removed to have smooth and clean surface of mandrel before the start of step of deposition of soot particles thereon.
- soft soot as employed herein means depositing soot layer having low density varying between about 0.3 to about 0.45 gm/cm 3 .
- the mandrel is heated in a furnace after suspending it in a suspension means to avoid contamination of its surface.
- the present invention relates to a mandrel suspension means suitable for suspending the mandrel in a furnace [not shown] comprising a suspension tube including neck portion and mouth wherein mandrel is suspended in suspension tube after fixing a holding means on one end thereof and suspension tube is closed with a closing means before placing in the furnace.
- a mandrel suspension means 200 suitable for suspending the mandrel 201 in a furnace comprises a suspension tube 202 having a cylindrical body 203 including neck portion 204 and a mouth portion 205 wherein mandrel 201 is suspended in suspension tube 202 after fixing a holding means 206 on one end thereof and suspension tube is closed with a closing means 207 provided with an opening 208 for release of expanded air on heating.
- the mandrel 201 fitted with holding means 206 is made to rest above neck portion 204.
- the suspension tube, holding means and closing means can be made of any suitable material capable of withstanding a temperature of about 900 0 C.
- the suspension tube, holding means and closing means are made of quartz glass capable of withstanding a temperature of about 900 0 C.
- the mandrel is cleaned for removal of sticky material therefrom prior to a step of heating thereby producing a cleaned mandrel suitable for heat treatment in accordance with present invention.
- the cleaning of the mandrel may be carried out by any known method, preferably it is carried out with an acid.
- the acid selected is preferably hydrochloric acid having concentration varying from about 20% by weight to about 30% by weight, preferably of about 25% by weight.
- the mandrel is heated at a temperature varying from about 400 0 C to about 800 0 C, preferably at a temperature varying from about 500 0 C to about 700 0 C.
- the mandrel is heated in a suitable heating furnace for a period varying from about 90 mins to about 210 mins, preferably for a period varying from about 120 mins to about 180 mins.
- the mandrel can be selected from the conventionally available mandrels.
- the mandrel made from a refractory material, preferably alumina or fused carbon material.
- carbon coating on the heat treated mandrel can be done by any known method.
- the carbon coating is done by employing acetylene flame preferably with flow rate varying from about 3 lpm [liters per minute] to about 5 lpm for thickness varying from about 1 mm to about 3 mm to achieve a carbon coating making its removal comfortable.
- soft soot coating on the heat treated mandrel can be done by any known method.
- the soft soot coating is done by employing hydrogen-oxygen flame having silica flow at central line.
- the flow rate of hydrogen varies from about 35 lpm to about 45 lpm and flow rate of oxygen varies from about 10 lpm to about 20 lpm. It has been observed that if flow rate of hydrogen is less than 35 lpm, the soft soot does not get deposited on the mandrel and if it is greater than 45 lpm, the density of soot deposited increases meaning thereby the soot deposited will not be soft in nature.
- the soft soot coating is deposited for at least a thickness of about 8 mm. It has been observed that if thickness of soft soot coating is less than 8 mm, the mandrel prepared does not have desired level of smoothness, and hence its removal becomes difficult.
- soft soot coating, and carbon coating followed by soft soot coating is prepared in accordance with present invention, it has been found that peeling of these coatings is easier to achieve desired smooth and clean surface of mandrel.
- the mandrel prepared employing method of this invention can be employed in any conventional method for preparing soot porous body.
- the mandrel prepared is employed in atmospheric chemical vapour deposition [ACVD] method as described herein.
- soot porous body 1 can be prepared by ACVD method.
- the preparation of soot porous body 1 comprises the following steps.
- the glass-forming precursor compounds are oxidized and hydrolyzed to form porous silica based materials 2.
- the porous silica based materials 2 are deposited on a tapered cylindrical member referred as mandrel 3 which has been prepared in accordance with any one of the embodiments described herein.
- the mandrel is provided with a handle rod 4 and fitted on a lathe 5 to form soot porous body 1.
- the process for preparing a mandrel suitable for producing flawless preform is characterized by heating the mandrel made from a refractory material or from a fused carbon material by suspending it in a mandrel suspension means before subjecting it to a step of deposition of soot particles thereon to produce soot porous body.
- the process for preparing a mandrel suitable for producing flawless preform is characterized by heating the mandrel made from a refractory material or from a fused carbon material by suspending it in a mandrel suspension means and depositing carbon coating on the heat treated mandrel before subjecting the mandrel to a step of deposition of soot particles to produce ,soot porous body.
- the process for preparing a mandrel suitable for producing flawless preform is characterized by heating the mandrel made from a refractory material or from a fused carbon material by suspending it in a mandrel suspension means and depositing soft soot coating on the heat treated mandrel followed by removal of soft soot coating from the surface of mandrel to achieve smooth and clean surface of the mandrel before subjecting the mandrel to a step of deposition of soot particles to produce soot porous body.
- the process for preparing a mandrel suitable for producing flawless preform is characterized by heating the mandrel made from a refractory material or from a fused carbon material by suspending it in a mandrel suspension means, and depositing carbon coating followed by depositing soft soot coating on the heat treated mandrel followed by removal of carbon coating and soft soot coating from the surface of mandrel to achieve smooth and clean surface thereof before subjecting the mandrel to a step of deposition of soot particles to produce soot porous body.
- the mandrel 3 prepared in accordance with present invention is rotated in a direction as illustrated by an arrow 6 and also moved along its length with reference to burner 7 to deposit the soot particles 2 on said mandrel 3 for producing soot porous body 1.
- the dopant chemicals for example Ge ⁇ 2 may also deposited to form the core of the preform and later the dopant chemicals may be terminated to form clad of the preform.
- soot porous body 1 After completion of deposition, the soot porous body 1 is removed from lathe 5 along with said mandrel 3 and handle rod 4, and thereafter said mandrel 3 which was prepared in accordance with process of present invention is detached from the soot porous body 1 thereby resulting in formation of.
- a hollow cylindrical soot porous body 8 (herein after may also be referred to as hollow soot porous body) having a centerline 9 therethrough [Figure 3], which upon visual inspection did not reveal any physical defects confirming that it is free from physical defects.
- the hollow soot porous body 8 thus formed comprises a core region
- a centerline 9 free from physical defects is created inside the soot porous body 1.
- the amount of deposition of the clad region 11 and core region 10 is achieved to have any desired ratio diameter of clad region 11 to the diameter of core region 10.
- the prepared hollow soot porous body 101 is transferred to the sintering furnace 100 in order to achieve dehydration and sintering of the hollow soot porous body 101, and collapsing of the centerline 102 of the hollow soot porous body 101 to form a solid glass preform 103 [Figure 6]. It is observed that desired solid glass preform is prepared when employing mandrel prepared in accordance with present invention without requiring any step of drilling or grinding or etching of the centerline 9/ 102 of sintered glass preform.
- the prepared hollow soot porous body 101 is dehydrated, sintered and collapsed to convert it into solid glass preform 103 without any step of drilling or grinding or etching with acid, the present process has been found to be highly time saving as well as highly economical for commercial applications.
- FIG. 5 shows exemplary embodiment to illustrate a general arrangement of the apparatus used in the present invention for dehydration, sintering and collapsing of the hollow soot porous body 101.
- the hollow soot porous body 101 one end of which is provided with a plug 116 is inserted inside the furnace 100 with the help of the handle rod 106.
- the driving mechanism (not shown) facilitates lowering of the hollow soot porous body 101 into the furnace 100.
- the furnace 100 comprises a muffle tube 110 having a diameter sufficient to accommodate the preform 101 and to adequately provide the environment necessary for dehydration, sintering and collapsing.
- the muffle tube 110 is heated to temperatures necessary for dehydration, sintering and collapsing process steps with the heating means (not shown) that are fitted to the sintering furnace 100.
- the heating means selected may be suitable to create three heat zones inside the muffle tube 110 over a length.
- a thermocouple (not shown) provided in the furnace 100 measures the temperature of the hot zones inside the furnace created by the heating means, and the data measurement is fed to the temperature controller (not shown) that controls the temperature inside the muffle tube 110.
- the furnace 100 is provided with an inlet port 115 located suitably on the furnace, preferably near the bottom of the muffle tube 110 for inserting desired gases in the furnace.
- the top end of the muffle tube 110 is closed with the lid 113 to achieve the preferred temperature profile inside the muffle tube 110 and to maintain the same during the dehydration, sintering and collapsing process steps, and to avoid leakage of gases from the muffle tube 110 to the outside environment.
- a suction port 114 is suitably provided near the top of muffle tube 110 to facilitate evacuation of the gases from the muffle tube 110 as and when required or on completion of the process.
- the bottom end of the soot porous body 101 is closed with glass frustum 116 before inserting inside the sintering furnace 100.
- the top end of the hollow soot porous body 101 supported with the handle rod 106 is mounted over the coupler 108 with the help of ball 109.
- the coupler 108 is connected with the assembly rod 111.
- the inside of the assembly rod 111 consists of smaller dimension tube 112 which is connected to the top end of the hollow soot porous body 101 through ball 109 and its opposite end 116A is connected to the vacuum generator (not shown) provided for achieving the required negative pressure inside the capillary 102 of the hollow soot porous body 101.
- the sintered glass preform produced after dehydration and sintering of the hollow soot porous body is examined for physical defects and surprisingly no physical defects were observed in the capillary region of the sintered glass preform.
- the sintered glass preform was subjected to step of collapsing of the centerline 9/ 102 therein to produce solid glass preform 103.
- the prepared solid glass preform 103 [ Figure 6] was also examined for physical defects and surprisingly no physical defects were observed in centerline region of the solid glass preform.
- the removal of mandrel 3 prepared in accordance with present invention from the soot porous body 1 has been found to be very easy and convenient, and hollow soot porous body thus produced was found suitable for further processing to prepare dehydrated and sintered glass preform, which was examined to evaluate physical defects in capillary region therein, and surprisingly no physical defects were observed.
- the sintered glass preform was subjected to step of collapsing to produce solid glass preform [may also be referred to as mother preform], which was also examined for physical defects and surprisingly no physical defects were found in the capillary region thereof. Accordingly, the solid glass preform was processed to produce core rods of reduced diameter, which were also examined for physical defects and surprisingly no physical defects were found in the capillary region thereof. Accordingly, the fiber was drawn from the core rod, which was also examined for physical defects and other characteristics, and surprisingly no physical defects were observed and fiber produced had other characteristics including attenuation loss, mode field diameter and cutoff wavelength within desired ranges.
- the present process has also been found to be suitable for effecting the removal of mandrel 3 without causing shearing of the core layer 10 and without forming flaky pitted centerline 9/ 102, and hence, has been observed to produce a preform without formation of defects, such as voids, bubbles, impurities, uncollapsed capillary in its centerline region.
- Example 1 [First Embodiment of Present Invention] :- A mandrel made of alumina [refractory material] was cleaned with a cleaning solution comprising 20% diluted hydrochloric acid solution for 20 min to remove foreign particles sticked on the mandrel. The cleaned mandrel was taken in the mandrel suspension means of present invention.
- the mandrel suspension means with mandrel was inserted inside the refractory furnace for heating it at a temperature of 550 0 C for 160 min. After heating, the mandrel suspension means was removed from refractory furnace and allowed to cool down to room temperature. After cooling, the heated treated mandrel was removed from the mandrel suspension means and fixed on the deposition lathe after fixing a handle tube on one end thereof.
- the soot comprising SiU2 and dopant Ge ⁇ 2 was deposited on a rotating mandrel by employing conventional ACVD method described hereinabove. After deposition of desired layers of core to form 40 mm diameter, the dopant was discontinued and clad layers were deposited to form soot porous body of 160 mm diameter. After formation of soot porous body of 160 mm diameter, it was removed from the deposition lathe and allowed to cool down to room temperature followed by removal of mandrel therefrom to form a hollow soot porous body having a centerline therein. The removal of mandrel was observed to be very easy and convenient without causing any shearing and formation of flaky pitted centerline.
- the hollow soot porous body was physically examined by visual inspection and no physical defects were observed therein.
- the hollow soot porous body was transferred to sintering furnace after fixing a glass plug in open end of capillary therein and was subjected to a step of dehydration at a temperature of 1250 degree C to form dehydrated hollow soot porous body followed by sintering at a temperature of 1500 degree C to form sintered glass preform.
- the sintered glass preform was removed out of furnace and allowed to cool down in a closed and filled with nitrogen clean room environment. After cooling, the sintered glass preform was also examined by CCD [Charged Couple Device] Camera for physical defects in its capillary region thereof.
- the sintered glass preform was transferred back to the sintering furnace for collapsing of capillary therein at a temperature of 1530 degree C to form solid glass preform [also known as mother preform].
- the solid glass preform was removed from the sintering furnace and allowed to cool down to room temperature. After cooling, the solid glass preform was also examined by CCD Camera for physical defects in its capillary region. Surprisingly, no physical defects were observed in the capillary region of the solid glass preform.
- the examined solid glass preform was transferred to rod draw furnace for drawing 9 nos. of core rods at a temperature of 1800 degree C, each having average diameter of about 20 mm.
- the drawn core rods were removed from rod draw furnace and allowed to cool down to room temperature.
- the cooled core rods were also examined by CCD Camera for physical defects in its capillary region. Surprisingly, physical defects were observed in the capillary region of 7% of the core rods drawn from a solid glass preform prepared by employing mandrel prepared in accordance with present invention.
- One of the examined core rods was transferred to deposition lathe to overclad by depositing clad layers to form soot porous body with core rod of 180 mm diameter, which was dehydrated and sintered by employing sintering furnace to form sintered glass preform [also known as daughter preform].
- the daughter preform was transferred to fiber draw furnace to draw optical fiber therefrom.
- the drawn optical fiber was examined for attenuation loss at 1310 nm and 1550 nm, and its cutoff wavelength and mode field diameter.
- the optical fiber drawn exhibited attenuation loss of 0.325 dB/km at 1310 nm and attenuation loss of 0.19 dB/km at 1550 nm, and cutoff wavelength of 1230 nm with mode field diameter of 9.13 ⁇ m.
- the method of present invention is suitable for preparation of mandrel for producing soot porous body, sintered glass preform, solid glass preform, core rod, daughter preform and optical fiber having no physical defects.
- Example 2 [Second Embodiment of Present Invention]:-
- a mandrel made of alumina [refractory material] was cleaned with a cleaning solution comprising 20% diluted hydrochloric acid solution for 20 min to remove foreign particles sticked on the mandrel.
- the cleaned mandrel was taken in the mandrel suspension means of present invention.
- the mandrel suspension means with mandrel was inserted inside the refractory furnace for heating it at a temperature of 550 0 C for 160 min. After heating, the mandrel suspension means was removed from refractory furnace and allowed to cool down to room temperature. After cooling, the heated treated mandrel was removed from the mandrel suspension means and fixed on the deposition lathe after fixing a handle tube on one end thereof for carbon coating 1.5 mm thickness using acetylene flame.
- the soot comprising Si ⁇ 2 and dopant Ge ⁇ 2 was deposited on a rotating mandrel having carbon coating deposited thereon by employing conventional ACVD method described hereinabove. After deposition of desired layers of core to form 41 mm diameter, the dopant was discontinued and clad layers were deposited to form soot porous body of 162 mm diameter. After formation of soot porous body of 162 mm diameter, it was removed from the deposition lathe and allowed to cool down to room temperature followed by removal of mandrel therefrom to form a hollow soot porous body having a centerline therein. The removal of mandrel was observed to be very easy without causing any shearing and formation of flaky pitted centerline.
- the hollow soot porous body was physically examined by visual inspection and no physical defects were observed therein.
- the hollow soot porous body was transferred to sintering furnace after fixing a glass plug in open end of capillary therein and was subjected to a step of dehydration at a temperature of 1250 degree C to form dehydrated hollow soot porous body followed by sintering at a temperature of 1500 degree C to form sintered glass preform.
- the sintered glass preform was removed out of furnace and allowed to cool down in a closed and filled with nitrogen clean room environment. After cooling, the sintered glass preform was also examined by CCD Camera for physical defects in its capillary region thereof. Surprisingly, no physical defects were observed in the capillary region of the sintered glass preform.
- the sintered glass preform was transferred back to the sintering furnace for collapsing of capillary therein at a temperature of 1530 degree C to form solid glass preform [also known as mother preform].
- the solid glass preform was removed from the sintering furnace and allowed to cool down to room temperature. After cooling, the solid glass preform was also examined by CCD Camera for physical defects in its capillary region. Surprisingly, no physical defects were observed in the capillary region of the solid glass preform.
- the examined solid glass preform was transferred to rod draw furnace for drawing 9 nos. of core rods at a temperature of 1800 degree C, each having average diameter of about 20 mm. The drawn core rods were removed from rod draw furnace and allowed to cool down to room temperature.
- the cooled core rods were also examined by CCD Camera for physical defects in its capillary region. Surprisingly, physical defects were observed in the capillary region of 3% of the core rods drawn from a solid glass preform prepared by employing mandrel prepared in accordance with present invention.
- One of the examined core rods was transferred to deposition lathe to overclad by depositing clad layers to form soot porous body with core rod of 182 mm diameter, which was dehydrated and sintered by employing sintering furnace' to form sintered glass preform [also known as daughter preform].
- the daughter preform was transferred to fiber draw furnace to draw optical fiber therefrom.
- the drawn optical fiber was examined for attenuation loss at 1310 nm and 1550 nm, and its cutoff wavelength and mode field diameter.
- the optical fiber drawn exhibited attenuation loss of 0.327 dB/km at 1310 nm and attenuation loss of 0.188 dB/km at 1550 nm, and cutoff wavelength of 1242 nm with mode field diameter of 9.18 ⁇ m.
- this method of present invention is also suitable for preparation of mandrel for producing soot porous body, sintered glass preform ⁇ solid glass preform, core rod, daughter preform and optical fiber having no physical defects.
- Example 3 [Third Embodiment of Present Invention] :-
- a mandrel made of alumina [refractory material] was cleaned with a cleaning solution comprising 20% diluted hydrochloric acid solution for 20 min to remove foreign particles sticked on the mandrel.
- the cleaned mandrel was taken in the mandrel suspension means of present invention.
- the mandrel suspension means with mandrel was inserted inside the refractory furnace for heating it at a temperature of 550 0 C for 160 min. After heating, the mandrel suspension means was removed from refractory furnace and allowed to cool down to room temperature.
- the heated treated mandrel was removed from the mandrel suspension means and fixed on the deposition lathe after fixing a handle tube on one end thereof for depositing coating of 150 layers of soft soot by employing ACVD method.
- the soft soot coating was removed to achieve smooth and clean surface of the heat treated mandrel.
- the soot comprising Si ⁇ 2 and dopant Ge ⁇ 2 was deposited on a rotating mandrel having soft soot deposited thereon by employing conventional ACVD method described hereinabove.
- the dopant was discontinued and clad layers were deposited to form soot porous body of 163 mm diameter.
- soot porous body After formation of soot porous body of 163 mm diameter, it was removed from the deposition lathe and allowed to cool down to room temperature followed by removal of mandrel therefrom to form a hollow soot porous body having a centerline therein. The removal of mandrel was observed to be very easy without causing any shearing and formation of flaky pitted centerline. The hollow soot porous body was physically examined by visual inspection and no physical defects were observed therein.
- the hollow soot porous body was transferred to sintering furnace after fixing a glass plug in open end of capillary therein and was subjected to a step of dehydration at a temperature of 1250 degree C to form dehydrated hollow soot porous body followed by sintering at a temperature of 1500 degree C to form sintered glass preform.
- the sintered glass preform was removed out of furnace and allowed to cool down in a closed and filled with nitrogen clean room environment. After cooling, the sintered glass preform was also examined by CCD Camera for physical defects in its capillary region thereof. Surprisingly, no physical defects were observed in the capillary region of the sintered glass preform.
- the sintered glass preform was transferred back to the sintering furnace for collapsing of capillary therein at a temperature of 1530 degree C to form solid glass preform [also known as mother preform].
- the solid glass preform was removed from the sintering furnace and allowed to cool down to room temperature. After cooling, the solid glass preform was also examined by CCD Camera for physical defects in its capillary region. Surprisingly, no physical defects were observed in the capillary region of the solid glass preform.
- the examined solid glass preform was transferred to rod draw furnace for drawing 9 nos. of core rods at a temperature of 1800 degree C, each having average diameter of about 20 mm. The drawn core rods were removed from rod draw furnace and allowed to cool down to room temperature.
- the cooled core rods were also examined by CCD Camera for physical defects in its capillary region. Surprisingly, physical defects were observed in the capillary region of 7% of the core rods drawn from a solid glass preform prepared by employing mandrel prepared in accordance with present invention.
- One of the examined core rods was transferred to deposition lathe to overclad by depositing clad layers to form soot porous body with core rod of 181 mm diameter, which was dehydrated and sintered by employing sintering furnace to form sintered glass preform [also known as daughter preform].
- the daughter preform was transferred to fiber draw
- this method of present invention is also suitable for preparation of mandrel for producing soot porous body, sintered glass preform, solid glass preform, core rod, daughter preform and optical fiber having no physical defects.
- Example 4 [Fourth Embodiment of Present Invention] :- A mandrel made of alumina [refractory material] was cleaned with a cleaning solution comprising 20% diluted hydrochloric acid solution for 20 min to remove foreign particles sticked on the mandrel. The cleaned mandrel was taken in the mandrel suspension means of present invention. The mandrel suspension means with mandrel was inserted inside the refractory furnace for heating it at a temperature of 550 0 C for 160 min. After heating, the mandrel suspension means was removed from refractory furnace and allowed to cool down to room temperature.
- the heated treated mandrel was removed from the mandrel suspension means and fixed on the deposition lathe after fixing a handle tube on one end thereof for carbon coating of 1.5 mm followed by depositing coating of 150 layers of soft soot by employing ACVD method.
- the carbon coating and soft soot coating were removed to achieve smooth and clean surface of the heat treated mandrel.
- the soot comprising S-O2 and dopant Ge ⁇ 2 was deposited on a rotating mandrel having carbon coating of 1.5 mm and 150 layers of soft soot deposited thereon by employing conventional ACVD method described hereinabove.
- soot porous body of 161 mm diameter After deposition of desired layers of core to form 43 mm diameter, the dopant was discontinued and clad layers were deposited to form soot porous body of 161 mm diameter. After formation of soot porous body of 161 mm diameter, it was removed from the deposition lathe and allowed to cool down to room temperature followed by removal of mandrel therefrom to form a hollow soot porous body having a centerline therein. The removal of mandrel was observed to be very easy without causing any shearing and formation of flaky pitted centerline. The hollow soot porous body was physically examined by visual inspection and no physical defects were observed therein.
- the hollow soot porous body was transferred to sintering furnace after fixing a glass plug in open end of capillary therein and was subjected to a step of dehydration at a temperature of 1250 degree C to form dehydrated hollow soot porous body followed by sintering at a temperature of 1500 degree C to form sintered glass preform.
- the sintered glass preform was removed out of furnace and allowed to cool down in a closed and filled with nitrogen clean room environment. After cooling, the sintered glass preform was also examined by CCD Camera for physical defects in its capillary region thereof. Surprisingly, no physical defects were observed in the capillary region of the sintered glass preform.
- the sintered glass preform was transferred back to the sintering furnace for collapsing of capillary therein at a temperature of 1530 degree C to form solid glass preform [also known as mother preform].
- the solid glass preform was removed from the sintering furnace and allowed to cool down to room temperature. After cooling, the solid glass preform was also examined by CCD Camera for physical defects in its capillary region. Surprisingly, no physical defects were observed in the capillary region of the solid glass preform.
- the examined solid glass preform was transferred to rod draw furnace for drawing 9 nos. of core rods at a temperature of 1800 degree C, each having average diameter of about 20 mm. The drawn core rods were removed from rod draw furnace and allowed to cool down to room temperature.
- the cooled core rods were also examined by CCD Camera for physical defects in its capillary region. Surprisingly, no physical defects were observed in the capillary region of any of the core rod drawn from a solid glass preform prepared by employing mandrel prepared in accordance with present invention.
- One of the examined core rods was transferred to deposition lathe to overclad by depositing clad layers to form soot porous body with core rod of 183 mm diameter, which was dehydrated and sintered by employing sintering furnace to form sintered glass preform [also known as daughter preform].
- the daughter preform was transferred to fiber draw furnace to draw optical fiber therefrom.
- the drawn optical fiber was examined for attenuation loss at 1310 nm and 1550 nm, and its cutoff wavelength and mode field diameter.
- the optical fiber drawn exhibited attenuation loss of 0.326 dB/km at 1310 nm and attenuation loss of 0.187 dB/km at 1550 nm, and cutoff wavelength of 1240 nm with mode field diameter of 9.11 ⁇ m.
- this method of present invention is also suitable for preparation of mandrel for producing soot porous body, sintered glass preform, solid glass preform, core rod, daughter preform and optical fiber having no physical defects.
- Example 5 [Prior Art]: -
- a mandrel made of alumina [refractory material] was cleaned with a cleaning solution comprising 20% diluted hydrochloric acid solution for 20 min to remove foreign particles sticked on the mandrel.
- the cleaned mandrel was fixed on the deposition lathe after fixing a handle tube on one end thereof.
- the soot comprising Si ⁇ 2 and dopant Ge ⁇ 2 was deposited on a rotating mandrel by employing conventional ACVD method described - hereinabove. After deposition of desired layers of core to form 40 mm diameter, the dopant was discontinued and clad layers were deposited to form soot porous body of 160 mm diameter.
- soot porous body After formation of soot porous body of 160 mm diameter, it was removed from the deposition lathe and allowed to cool down to room temperature followed by removal of mandrel therefrom to form a hollow soot porous body having a centerline therein. The removal of mandrel was observed to be very difficult and it appeared to have caused shearing and formed flaky pitted centerline. The hollow soot porous body was physically examined by visual inspection and few physical defects were observed therein.
- the hollow soot porous body was transferred to sintering furnace after fixing a glass plug in open end of capillary therein and was subjected to a step of dehydration at a temperature of 1250 degree C to form dehydrated hollow soot porous body followed by sintering at a temperature of 1500 degree C to form sintered glass preform.
- the sintered glass preform was removed out of furnace and allowed to cool down in a closed and filled with nitrogen clean room environment. After cooling, the sintered glass preform was also examined by CCD Camera for physical defects in its capillary region thereof. Several physical defects were observed in the capillary region of the sintered glass preform. Therefore, the further processing was discarded.
- the above experimental studies confirm that if a cleaned mandrel is heated before start of further processing, it has surprising advantages of easy and convenient removal and of avoiding formation of physical defects in the capillary region of the hollow soot porous body.
- the above findings also confirm that the mandrel prepared in accordance with present invention is suitable for producing a flawless preform without requiring any step of drilling or grinding or etching with acid or mechanical milling or fire polishing etc. of capillary region of sintered glass preform, and hence, the overall process for producing a flawless preform not only becomes highly time saving, but also highly economical for commercial applications.
- the presently disclosed process for preparing a mandrel suitable for producing a flawless preform makes the process for producing optical fiber having very low attenuation loss and almost no cracks and breaks therein not only highly time saving, but also highly economical by avoiding steps of grinding and/or drilling and/or etching with an acid, and/or laser miling and/or mechanical polishing and/or fire polishing of the centerline created by easy removal of mandrel from the soot porous body.
- the present method has been described for ACVD method wherein sintering and collapsing steps have been performed one after the another.
- mandrel prepared in accordance with present invention has been found suitable for ACVD wherein sintering and collapsing steps can be performed simultaneously. Further, the mandrel prepared in accordance with present invention has been found suitable for all other known methods for manufacturing optical performs.
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Abstract
L'invention concerne un procédé pour préparer un mandrin adapté à produire la préforme de fibre optique sans défaut, le mandrin pouvant être facilement retiré du corps poreux à la suie sans causer de défauts, tels que des vides, bulles, impuretés, une partie non affaissée dans la région médiane de la préforme ainsi produite. Ledit procédé est caractérisé en ce que le mandrin avant le début de la déposition de suie forme un corps poreux à la suie ayant un cœur et une gaine.
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IN1351MU2006 | 2006-08-25 | ||
IN1351/MUM/2006 | 2007-03-20 |
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PCT/IN2007/000306 WO2008038298A2 (fr) | 2006-08-25 | 2007-07-24 | Procédé pour préparer un mandrin adapté à produire une préforme de fibre optique sans défaut et préforme produite à partir de celui-ci |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011054574A1 (fr) * | 2009-11-09 | 2011-05-12 | Heraeus Quarzglas Gmbh & Co. Kg | Procédé de fabrication d'un cylindre en verre de quartz ainsi que support pour mettre en oeuvre le procédé |
WO2016141129A1 (fr) * | 2015-03-04 | 2016-09-09 | Corning Incorporated | Procédé de fabrication d'une préforme de suie de silice poreuse pour fibre optique par revêtement d'un substrat d'amorce |
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US4204850A (en) * | 1977-08-26 | 1980-05-27 | Corning Glass Works | Carbon coating for a starting member used in producing optical waveguide |
JP2000203862A (ja) * | 1999-01-14 | 2000-07-25 | Furukawa Electric Co Ltd:The | 光ファイバ母材製造用加熱炉のタ―ゲット棒吊下げ保持部 |
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JP2898705B2 (ja) * | 1990-05-30 | 1999-06-02 | 古河電気工業株式会社 | 光ファイバ母材の製造方法 |
JPH1171125A (ja) * | 1997-08-26 | 1999-03-16 | Sumitomo Electric Ind Ltd | 光ファイバ用プリフォームの製造方法 |
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2007
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US4204850A (en) * | 1977-08-26 | 1980-05-27 | Corning Glass Works | Carbon coating for a starting member used in producing optical waveguide |
JP2000203862A (ja) * | 1999-01-14 | 2000-07-25 | Furukawa Electric Co Ltd:The | 光ファイバ母材製造用加熱炉のタ―ゲット棒吊下げ保持部 |
Non-Patent Citations (2)
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DATABASE WPI Week 199212, Derwent Publications Ltd., London, GB; AN 1992-093668 & JP 04 037623 A (FURUKAWA ELECTRIC CO LTD) 07 February 1992 * |
DATABASE WPI Week 199921, Derwent Publications Ltd., London, GB; AN 1999-248324 & JP 11 071125 A (SUMITOMO ELECTRIC IND CO) 16 March 1999 * |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2011054574A1 (fr) * | 2009-11-09 | 2011-05-12 | Heraeus Quarzglas Gmbh & Co. Kg | Procédé de fabrication d'un cylindre en verre de quartz ainsi que support pour mettre en oeuvre le procédé |
US8783069B2 (en) | 2009-11-09 | 2014-07-22 | Heraeus Quarzglas Gmbh & Co. Kg | Process for producing a quartz glass cylinder and also support for carrying out the process |
WO2016141129A1 (fr) * | 2015-03-04 | 2016-09-09 | Corning Incorporated | Procédé de fabrication d'une préforme de suie de silice poreuse pour fibre optique par revêtement d'un substrat d'amorce |
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WO2008038298A3 (fr) | 2008-05-15 |
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