JP4398114B2 - Manufacturing method of glass base material for optical fiber with less unevenness - Google Patents

Manufacturing method of glass base material for optical fiber with less unevenness Download PDF

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JP4398114B2
JP4398114B2 JP2001164038A JP2001164038A JP4398114B2 JP 4398114 B2 JP4398114 B2 JP 4398114B2 JP 2001164038 A JP2001164038 A JP 2001164038A JP 2001164038 A JP2001164038 A JP 2001164038A JP 4398114 B2 JP4398114 B2 JP 4398114B2
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optical fiber
glass
base material
straight body
glass base
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JP2002356342A (en
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哲也 乙坂
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Shin Etsu Chemical Co Ltd
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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]
    • C03B37/01413—Reactant delivery systems
    • C03B37/0142—Reactant deposition burners
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2207/00—Glass deposition burners
    • C03B2207/50—Multiple burner arrangements
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2207/00—Glass deposition burners
    • C03B2207/60—Relationship between burner and deposit, e.g. position
    • C03B2207/66—Relative motion
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2207/00—Glass deposition burners
    • C03B2207/70—Control measures
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a glass preform for an optical fiber capable of obtaining an optical fiber having stable core/clad ratio in the length direction and enabling to reduce ruggedness in the vicinity of an edge part of the straight body of a porous glass preform. SOLUTION: This method for producing an optical fiber preform comprises piling up glass microparticles generated by flame-hydrolyzing silicon-containing compounds around the outer circumferential surface of a target rod 1 while one or several burners 2 and 2 for synthesizing the glass microparticles repeatingly reciprocating relative to each other along the rotating target rod 1, characterized in that the bulk density in the vicinity of an edge part of the straight body of a porous glass preform 3 in the course of being piled up is made higher than that in the intermediate part.

Description

【０００１】
【発明の属する技術分野】
本発明は、火炎加水分解反応によって生成するガラス微粒子をターゲット棒に堆積させる光ファイバ用ガラス母材の製造に係り、特に、透明ガラス化後、紡糸することで長手方向に安定したコア／クラッド比を有する光ファイバが得られる、凹凸の少ない光ファイバ用ガラス母材の製造方法に関する。
【０００２】
【従来の技術】
高純度石英ガラスや、光ファイバ用ガラス母材を製造する方法として、回転するターゲット棒に沿って繰り返し往復運動するガラス微粒子合成用バーナーを用いて、ターゲット棒の外周面に火炎加水分解で生成するガラス微粒子を堆積させて多孔質ガラス母材を合成し、これを約１５００℃でガラス化する方法がある。このガラス微粒子合成用バーナーには、Ｈ2等の可燃性ガスとＯ2等の助燃性ガス、ガラス微粒子の原料となるＳｉＣｌ4等の珪素含有化合物が供給され、火炎中で原料が加水分解されてガラス微粒子ＳｉＯ2が合成される。
【０００３】
この方法はＯＶＤ法と呼ばれ、これには、ターゲット棒を水平に設置して、バーナーを左右に往復運動させる方法や、バーナーを水平に設置して、ターゲット棒を上下に往復運動させる方法、さらに、バーナーを複数本配置したり、その配置の仕方を変える等、幾つかのバリエーションがある。
【０００４】
近年、紡糸工程の効率化・低コスト化をはかるため、光ファイバプリフォームの大口径化が進み、これに伴って、多孔質ガラス母材の外径もより大きなものが要求されている。
【０００５】
ＯＶＤ法で外径の大きな多孔質ガラス母材を製造する場合、単に堆積する層数を増すだけでも外径を大きくすることができるが、この場合、図２に示すように、ターゲット棒１にバーナー２，２ で生じたガラス微粒子流４を吹き付けて形成される多孔質ガラス母材３の直胴部の両端部分では、外径が増すにつれてガラス微粒子流４が乱れ、多孔質ガラス母材３の長手方向に滑らかとならず、形状が円柱状でなく、長手方向に外径が部分的に異なる凹凸形状となる。このような多孔質ガラス母材を透明ガラス化して紡糸すると、長手方向でコア／クラッド比が変化し、信号伝送特性が安定しないという問題が生じてきた。
【０００６】
そこで、本発明は、多孔質ガラス母材の直胴端部の凹凸を少なくすることができ、長手方向に安定したコア／クラッド比を有する光ファイバが得られる、光ファイバ用ガラス母材の製造方法を提供することを目的としている。
【０００７】
【問題を解決するための手段】
本発明の凹凸の少ない光ファイバ用ガラス母材の製造方法は、１乃至複数本のガラス微粒子合成用バーナーを回転するターゲット棒に沿って相対的に繰り返し往復運動させつつ、ターゲット棒の外周面に珪素含有化合物を火炎加水分解して生成するガラス微粒子を堆積させて光ファイバ用ガラス母材を製造する方法において、堆積中の多孔質ガラス母材の直胴端部の嵩密度をその中間部よりも上げることを特徴としている。
【０００８】
上記直胴端部の嵩密度を上げるには、ガラス微粒子の堆積が直胴端部付近でなされている間、ターゲット棒の回転数を下げるか、あるいは、バーナーへの可燃性ガス及び／又は助燃性ガスの供給量を増加するようにしても良い。
【０００９】
【発明の実施の形態】
本発明者は、多孔質ガラス母材の直胴端部に凹凸が生じる原因を詳細に調査検討した結果、バーナーから出たガラス微粒子流が多孔質ガラス母材にぶつかり、そこで長手方向成分の流れが生じ、これが直胴端部において、長手方向に不均一な堆積を生じて凹凸となり、その後、この凹凸が成長していくことを究明した。
【００１０】
そこで本発明者は、多孔質ガラス母材の直胴端部の形状をなだらかにし、直胴端部における長手方向の曲率半径を大きくすることで、長手方向への火炎の流れ、すなわちガラス微粒子流が滑らかになり、堆積の不均一性を緩和できるのではないかと考え、この直胴端部、特にテーパー部と直胴部の境目の密度を上げることで、堆積量を変えずに形状だけを変化させたところ、直胴端部の凹凸の大きさが非常に小さくなることを確認した。
その結果、直胴部の凹凸が減り、これを透明ガラス化した光ファイバ用プリフォーム及び紡糸して得られる光ファイバは、コア／クラッド比が長手方向で安定し、製品歩留まりが向上する。
【００１１】
嵩密度を上げる方法としては、Ｈ2等の可燃性ガス、Ｏ2等の助燃性ガスの供給量を増したり、多孔質ガラス母材の回転数を下げる方法が有効であることを確認した。すなわち、これは、多孔質ガラス母材に対して相対的に往復運動するバーナーが、多孔質ガラス母材の端部付近を通過する際に、火炎の温度を上げたり、火炎中を多孔質ガラス母材表面が通過する速度を落とすことで、嵩密度を上げる方法である。
【００１２】
火炎の温度を上げる方法は、左右に往復運動しているバーナーが多孔質ガラス母材の直胴端部付近にある間は、Ｈ2とＯ2の流量を直胴中央部の１．１〜１．８倍となるように流量制御するのが好ましい。
また、火炎中を多孔質ガラス母材表面が通過する速度を落とす方法としては、バーナーが多孔質ガラス母材の直胴端部付近にある間は、ターゲット棒の回転数を直胴中央部の０．９〜０．５倍となるように制御するのが好ましい。
以下、実施例を挙げて本発明の製造方法をさらに詳述する。
【００１３】
【実施例】
（実施例１）
図１に示すように、バーナーにＨ2等の可燃性ガス、Ｏ2等の助燃性ガス及びＳｉＣｌ4等の珪素含有化合物を供給し、火炎加水分解で生成されるガラス微粒子を回転する石英ガラス製のターゲット棒１の外周面に堆積させた。２本のバーナー２，２をターゲット棒１に沿って繰り返し左右に往復運動させ、多孔質ガラス母材３が所定の径に達するまで、ガラス微粒子の堆積を続けた。
【００１４】
堆積中、左右に往復運動しているバーナー２，２が多孔質ガラス母材３の直胴端部付近にある間は、Ｈ2とＯ2の流量を直胴中央部の１．２倍となるように流量制御して、直胴端部の嵩密度を上げ、凹凸の少ない多孔質ガラス母材を製造した。
この多孔質ガラス母材を、Ｈｅ雰囲気中で透明ガラス化して外径２１０ｍｍφのガラス母材（プリフォーム）を得た。このガラス母材の直胴端部での凹凸の深さは、最大でも０．５ｍｍであった。
【００１５】
（実施例２）
図１において、バーナー２，２が多孔質ガラス母材３の直胴端部付近にある間は、ターゲット棒１の回転数を直胴中央部の０．７倍となるように制御して、直胴端部の嵩密度を上げ、凹凸の少ない多孔質ガラス母材を製造した。
この多孔質ガラス母材を、Ｈｅ雰囲気中で透明ガラス化して外径２１０ｍｍφのガラス母材を得た。このガラス母材の直胴端部での凹凸の深さは、最大でも０．７ｍｍであった。
【００１６】
（比較例１）
直胴端部の嵩密度を上げるような手段をとらず、長手方向への密度補正をかけない従来方法で多孔質ガラス母材を製造した。この多孔質ガラス母材は、図２に示すように、直胴端部に深い凹凸５を生じた。
この多孔質ガラス母材を、Ｈｅ雰囲気中で透明ガラス化して外径２１０ｍｍφのガラス母材を得た。このガラス母材の直胴端部での凹凸の深さは、最大３．２ｍｍであった。
【００１７】
【発明の効果】
本発明の製造方法によれば、直胴部の凹凸が減り、これを透明ガラス化した光ファイバ用プリフォーム及び紡糸して得られる光ファイバは、コア／クラッド比が長手方向で安定し、製品歩留まりが向上する。
【図面の簡単な説明】
【図１】 本発明の凹凸の少ない光ファイバ用ガラス母材の製造方法を説明する概略斜視図である。
【図２】 従来技術による光ファイバ用ガラス母材の製造方法を説明する概略斜視図である。
【符号の説明】
１． ターゲット棒、
２，２． バーナー、
３． 多孔質ガラス母材、
４． ガラス微粒子流、
５． 凹凸。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the production of a glass preform for optical fiber in which glass fine particles generated by a flame hydrolysis reaction are deposited on a target rod, and in particular, a core / cladding ratio that is stable in the longitudinal direction by spinning after forming a transparent glass. It is related with the manufacturing method of the glass base material for optical fibers with few unevenness from which the optical fiber which has this is obtained.
[0002]
[Prior art]
As a method for producing high-purity quartz glass and glass base material for optical fiber, it is generated by flame hydrolysis on the outer peripheral surface of the target rod using a burner for synthesizing fine glass particles that reciprocates repeatedly along the rotating target rod. There is a method of synthesizing a porous glass base material by depositing glass particles and vitrifying it at about 1500 ° C. This glass fine particle synthesis burner is supplied with a flammable gas such as H 2 , an auxiliary combustion gas such as O 2, and a silicon-containing compound such as SiCl 4 as a raw material for glass fine particles, and the raw material is hydrolyzed in a flame. Thus, glass fine particles SiO 2 are synthesized.
[0003]
This method is called the OVD method, which includes a method in which the target bar is horizontally installed and the burner is reciprocated left and right, a method in which the burner is horizontally installed and the target bar is reciprocated up and down, Furthermore, there are several variations, such as arranging a plurality of burners or changing the arrangement.
[0004]
In recent years, in order to increase the efficiency and cost of the spinning process, the diameter of the optical fiber preform has been increased, and accordingly, the outer diameter of the porous glass preform is required to be larger.
[0005]
When a porous glass base material having a large outer diameter is manufactured by the OVD method, the outer diameter can be increased simply by increasing the number of deposited layers. In this case, as shown in FIG. At both ends of the straight body portion of the porous glass base material 3 formed by spraying the glass fine particle stream 4 generated by the burners 2 and 2, the glass microparticle stream 4 is disturbed as the outer diameter increases, and the porous glass base material 3 It is not smooth in the longitudinal direction, and the shape is not a columnar shape, and an uneven shape having a partially different outer diameter in the longitudinal direction. When such a porous glass base material is spun into a transparent glass, the core / cladding ratio changes in the longitudinal direction, causing a problem that the signal transmission characteristics are not stable.
[0006]
Accordingly, the present invention can reduce the irregularities at the end of the straight body of the porous glass preform, and can produce an optical fiber having a stable core / cladding ratio in the longitudinal direction. It aims to provide a method.
[0007]
[Means for solving problems]
The method for producing an optical fiber glass base material with less unevenness according to the present invention causes one or a plurality of glass fine particle synthesis burners to reciprocate relatively repeatedly along a rotating target bar, while moving the outer peripheral surface of the target bar. In a method for producing a glass preform for optical fiber by depositing glass fine particles produced by flame hydrolysis of a silicon-containing compound, the bulk density of the straight barrel end of the porous glass preform being deposited is determined from the middle portion thereof. It is also characterized by raising.
[0008]
In order to increase the bulk density at the end of the straight cylinder , the glass rod is deposited near the end of the straight cylinder while the rotation speed of the target rod is decreased, or the combustible gas and / or auxiliary combustion to the burner is reduced. The supply amount of the property gas may be increased.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As a result of detailed investigation and investigation of the cause of unevenness at the end of the straight body of the porous glass base material, the present inventor hit the porous glass base material with the flow of fine glass particles from the burner, where the flow of the longitudinal component It has been clarified that at the end of the straight cylinder, uneven deposition occurs in the longitudinal direction to form irregularities, and thereafter these irregularities grow.
[0010]
Therefore, the present inventor has made the flow of the flame in the longitudinal direction, that is, the flow of the glass fine particles, by smoothening the shape of the end of the straight body of the porous glass base material and increasing the radius of curvature in the longitudinal direction at the end of the straight body. By increasing the density of this straight cylinder end, especially the boundary between the taper part and the straight cylinder part, the shape can be changed without changing the deposition amount. As a result of the change, it was confirmed that the size of the irregularities at the end of the straight body was very small.
As a result, the unevenness of the straight body portion is reduced, and the optical fiber preform and the optical fiber obtained by spinning the optical fiber preform are stabilized in the core / cladding ratio in the longitudinal direction, and the product yield is improved.
[0011]
As a method for increasing the bulk density, it has been confirmed that a method of increasing the supply amount of a combustible gas such as H 2 and an auxiliary combustible gas such as O 2 or a method of decreasing the rotational speed of the porous glass base material has been confirmed. That is, when the burner that reciprocates relative to the porous glass base material passes near the end of the porous glass base material, the temperature of the flame is increased or the porous glass is passed through the flame. This is a method of increasing the bulk density by reducing the speed at which the surface of the base material passes.
[0012]
The method of raising the temperature of the flame is that the flow rate of H 2 and O 2 is changed from 1.1 to 1.1 at the center of the straight cylinder while the burner reciprocating left and right is in the vicinity of the straight cylinder end of the porous glass base material. It is preferable to control the flow rate so as to be 1.8 times.
In addition, as a method of reducing the speed at which the surface of the porous glass base material passes through the flame, while the burner is near the straight body end of the porous glass base material, the rotational speed of the target rod is It is preferable to control to 0.9 to 0.5 times.
Hereinafter, an Example is given and the manufacturing method of this invention is explained in full detail.
[0013]
【Example】
Example 1
As shown in FIG. 1, a quartz glass in which a combustible gas such as H 2 , an auxiliary combustible gas such as O 2, and a silicon-containing compound such as SiCl 4 are supplied to a burner to rotate glass particles generated by flame hydrolysis. It was deposited on the outer peripheral surface of the target rod 1 made of metal. The two burners 2 and 2 were repeatedly reciprocated left and right along the target rod 1, and the glass fine particles were continuously deposited until the porous glass base material 3 reached a predetermined diameter.
[0014]
During deposition, while the burners 2 and 2 reciprocating left and right are in the vicinity of the end of the straight body of the porous glass base material 3, the flow rates of H 2 and O 2 are 1.2 times the center of the straight body. The flow rate was controlled so that the bulk density at the end of the straight body was increased to produce a porous glass base material with few irregularities.
This porous glass base material was made into transparent glass in a He atmosphere to obtain a glass base material (preform) having an outer diameter of 210 mmφ. The depth of the irregularities at the end of the straight body of the glass base material was 0.5 mm at the maximum.
[0015]
(Example 2)
In FIG. 1, while the burners 2 and 2 are in the vicinity of the straight barrel end of the porous glass base material 3, the rotational speed of the target bar 1 is controlled to be 0.7 times that of the central portion of the straight barrel, The bulk density of the end portion of the straight body was increased to produce a porous glass base material with less unevenness.
This porous glass base material was made into a transparent glass in a He atmosphere to obtain a glass base material having an outer diameter of 210 mmφ. The depth of the irregularities at the end of the straight body of the glass base material was 0.7 mm at the maximum.
[0016]
(Comparative Example 1)
A porous glass base material was manufactured by a conventional method without taking a means for increasing the bulk density at the end of the straight body and applying no density correction in the longitudinal direction. As shown in FIG. 2, this porous glass base material had deep irregularities 5 at the end of the straight body.
This porous glass base material was made into a transparent glass in a He atmosphere to obtain a glass base material having an outer diameter of 210 mmφ. The depth of the unevenness at the end of the straight body of the glass base material was 3.2 mm at the maximum.
[0017]
【The invention's effect】
According to the manufacturing method of the present invention, the unevenness of the straight body portion is reduced, and the optical fiber preform obtained by spinning this into a transparent glass and the optical fiber obtained by spinning have a stable core / cladding ratio in the longitudinal direction. Yield is improved.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic perspective view illustrating a method for producing a glass preform for optical fiber with less unevenness according to the present invention.
FIG. 2 is a schematic perspective view for explaining a method for producing a glass preform for an optical fiber according to the prior art.
[Explanation of symbols]
1. Target stick,
2,2. burner,
3. Porous glass base material,
4). Glass particulate flow,
5). Unevenness.

Claims (3)

１乃至複数本のガラス微粒子合成用バーナーを回転するターゲット棒に沿って相対的に繰り返し往復運動させつつ、ターゲット棒の外周面に珪素含有化合物を火炎加水分解して生成するガラス微粒子を堆積させて光ファイバ用ガラス母材を製造する方法において、堆積中の多孔質ガラス母材の直胴端部の嵩密度をその中間部よりも上げることを特徴とする凹凸の少ない光ファイバ用ガラス母材の製造方法。One or more glass fine particle synthesis burners are relatively reciprocated along a rotating target rod, and glass fine particles generated by flame hydrolysis of a silicon-containing compound are deposited on the outer peripheral surface of the target rod. In a method for producing a glass preform for an optical fiber, an optical fiber glass preform with less unevenness, characterized in that the bulk density of the straight barrel end of the porous glass preform being deposited is higher than its middle portion. Production method. ガラス微粒子の堆積が直胴端部付近でなされている間、ターゲット棒の回転数を下げることにより、直胴端部の嵩密度を上げる請求項１に記載の凹凸の少ない光ファイバ用ガラス母材の製造方法。The glass base material for optical fibers with less unevenness according to claim 1, wherein the bulk density of the end portion of the straight body is increased by lowering the number of revolutions of the target rod while the glass particles are deposited near the end portion of the straight body. Manufacturing method. バーナーへの可燃性ガス及び／又は助燃性ガスの供給量を増加することにより、直胴端部の嵩密度を上げる請求項１に記載の凹凸の少ない光ファイバ用ガラス母材の製造方法。The method for producing a glass preform for an optical fiber with less irregularities according to claim 1, wherein the bulk density of the end portion of the straight body is increased by increasing the supply amount of the combustible gas and / or auxiliary combustion gas to the burner.
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