JP2004307235A - Method of manufacturing glass preform for optical fiber - Google Patents

Method of manufacturing glass preform for optical fiber Download PDF

Info

Publication number
JP2004307235A
JP2004307235A JP2003100290A JP2003100290A JP2004307235A JP 2004307235 A JP2004307235 A JP 2004307235A JP 2003100290 A JP2003100290 A JP 2003100290A JP 2003100290 A JP2003100290 A JP 2003100290A JP 2004307235 A JP2004307235 A JP 2004307235A
Authority
JP
Japan
Prior art keywords
glass
fine particle
weight
flow rate
growth
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2003100290A
Other languages
Japanese (ja)
Inventor
Tomohiro Ishihara
朋浩 石原
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sumitomo Electric Industries Ltd
Original Assignee
Sumitomo Electric Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sumitomo Electric Industries Ltd filed Critical Sumitomo Electric Industries Ltd
Priority to JP2003100290A priority Critical patent/JP2004307235A/en
Publication of JP2004307235A publication Critical patent/JP2004307235A/en
Pending legal-status Critical Current

Links

Images

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]
    • 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
    • C03B2207/36—Fuel or oxidant details, e.g. flow rate, flow rate ratio, fuel additives
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2207/00—Glass deposition burners
    • C03B2207/70—Control measures

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a glass preform for optical fiber by the VAD method which realize the stabilized outside diameter (D/d when a plurality of burners are used) and refraction factor in a lot and between the lots. <P>SOLUTION: In the method of manufacturing the glass preform for a optical fiber performed by forming a glass fine particle deposited body by the VAD method and heating the resultant glass fine deposited body at high temperature to manufacture a transparent glass preform, the weight and the axial growth length of the glass fine particle deposited boy are measured successively during the deposition of the glass fine particle and the quantity of the deposited glass fine particle in the diameter direction is controlled by feed-backing the deviation between the measured increased weight per unit length of the glass fine particle and the desired increasing weight to the flow rate of at least one selected from a gaseous starting material, a combustible gas and an assistant gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ＶＡＤ法を用いたガラス母材の製造方法であって、外径（複数本のバーナーを使用する場合にはクラッド外径Ｄとコア外径ｄの比Ｄ／ｄ）並びに屈折率（複数本のバーナーを使用する場合にはコア屈折率Δｎ）がロット内及びロット間で安定する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】
ＶＡＤ法による光ファイバ用ガラス母材製造の重量増加速度の安定化方法としては、成長母材の重量を逐次監視し、重量増加量の偏差を酸水素量、原料供給量、排気量にフィードバックし、成長母材の成長密度が常に均一になるようにするものが提案されている（特許文献１参照）。
しかし、この方法では、単位時間当たりの堆積ガラス重量が全体として一定になるようにガラス母材を成長させるため、径方向のガラス微粒子実着量が安定化されているとは限らない。すなわち、径方向のガラス微粒子実着量が目標に対して少なく（多く）とも、軸方向でガラス微粒子が多く（少なく）実着されれば、全体としての堆積ガラス重量は一定になってしまうためである。
【０００３】
径方向のガラス微粒子実着量が安定しないと、ガラス微粒子堆積体を加熱して透明ガラス化した後、ガラス母材の外径、もしくはクラッドの外径とコアの外径の比率（Ｄ／ｄ）が安定せず、さらに屈折率も母材外径の変化に伴って変動することとなるので、光ファイバにしたときの品質に悪影響を及ぼす。
また、このような径方向のガラス微粒子実着量は、ロット内での安定が望ましいのはもちろんのこと、ロット間でもばらつきなく安定して製造されるのが望ましい。
【０００４】
【特許文献１】
特公昭６１−３２９６号公報（２頁３欄２０行〜４欄１４行）
【０００５】
【発明が解決しようとする課題】
本発明は、上記の問題点を解消し、ロット内及びロット間で外径（複数本のバーナーを使用する場合にはＤ／ｄ）が安定し、屈折率が安定する、ＶＡＤ法による光ファイバ用ガラス母材の製造方法を提供しようとするものである。
【０００６】
【課題を解決するための手段】
本発明者は、下記の構成を採用することにより前記の課題の解決を可能にした。
１．ＶＡＤ法によりガラス微粒子堆積体を作製し、得られたガラス微粒子堆積体を高温加熱して透明ガラス母材を製造する光ファイバ用ガラス母材の製造方法において、ガラス微粒子の堆積中に逐次ガラス微粒子堆積体の重量と軸方向の成長長さを測定し、ガラス微粒子堆積体の単位長さあたりの測定増加重量と目標増加重量の偏差を原料ガス、可燃性ガス及び助燃性ガスから選ばれる少なくとも一種の流量にフィードバックして、径方向のガラス微粒子堆積量を調整することを特徴とするガラス母材の製造方法。
２．下記式（１）の値が０．００４〜１．２（Ｌ／ｇ）となるよう原料ガス流量を調整することを特徴とする前記１記載のガラス母材の製造方法。
（｜調整後の原料ガス流量−調整前の原料ガス流量｜×成長長さ）／（｜測定増加重量−目標増加重量｜×成長速度） （１）
（成長長さは測定開始からフィードバック時までのガラス微粒子堆積体の軸方向の成長長さ（ｍｍ）を指し、成長速度はこの間のガラス微粒子堆積体の軸方向の平均成長速度（ｍｍ／分）を指す。目標増加重量は予め定めた前記成長長さにおける増加重量（ｇ）であり、測定増加重量は測定開始時からフィードバック時までのガラス微粒子堆積体の増加重量（ｇ）である。原料ガス流量は単位時間当たりの原料ガス流量（ＳＬＭ）とする。なお、測定増加重量が目標増加重量と等しいときは、原料ガス流量の調整は行わず、そのままの原料ガス流量で製造を継続するものとする。）
３．ガラス微粒子の堆積開始後、ガラス微粒子堆積体の成長が定常状態になったところでガラス微粒子堆積体の軸方向の成長長さの測定を開始し、予め定めた一定の長さ成長したところでガラス微粒子堆積体の成長長さ測定開始時からの増加重量をフィードバックすることを特徴とする前記１又は２記載のガラス母材の製造方法。
４．前記一定の長さが２００ｍｍ以下である前記３記載のガラス母材の製造方法。
【０００７】
【発明の実施の形態】
本発明のガラス母材製造方法においては、ガラス微粒子堆積体の製造時に、ガラス微粒子堆積体の重量とともにその軸方向への成長長さ（いわゆる引上げ長であり、コア、クラッド同時合成であればコアの軸方向の成長長さをいう。以下、これらを単に成長長さという）を測定、監視し、単位長さ当りの増加重量が予め定めた目標値に近づくようにガラス堆積量を調整する。たとえば、フィードバックを行うためのガラス微粒子堆積体の成長長さ（単位長さ）と、その長さ分の目標増加重量を予め定めておき、測定開始後、単位長さまでガラス堆積体が成長したときに、目標増加重量と実際のガラス堆積体の増加重量との偏差をとり、これをガス流量にフィードバックしてガラス微粒子の堆積量の調整に反映させるという方法をとることができる。
【０００８】
フィードバックは１ロットの間に複数回繰り返して行っても良いが、１回で十分効果があり、特に、各ロットにおいて同じタイミングで同じ目標増加重量を設定して行うことでロット間のばらつきを減少させることができる。このタイミングとしては、ガラス微粒子の堆積開始後、ガラス微粒子体積体の成長が定常状態になったところ、もしくはスタートガラスロッドの下端から測定を開始して一定の成長長さになったところでフィードバックを行うのが効果的である。堆積初期が最も堆積密度と外径が不安定なためである。この場合のフィードバックを行う成長長さはガラス微粒子堆積体の成長が定常状態になってから２００ｍｍ以下が好ましく、スタートガラスロッドの下端から３００ｍｍ以下がより好ましく、スタートガラスロッドの下端から１００〜３００ｍｍがさらに好ましい。フィードバックを行うときの成長長さが長すぎると、フィードバックを行うまでの部分が不良となったときに不良部分が長くなる。短すぎると、重量の測定精度不足により所望の増加重量にうまく調整できない。
複数回繰り返してフィードバックを行う場合には、ガラス微粒子体積体の成長が定常状態になったところで測定を開始して上記の成長長さごとにフィードバックを行うのが好ましい。
【０００９】
ガラス微粒子の堆積量の調整方法としては、原料ガス、可燃性ガス及び助燃性ガスから選ばれる少なくとも一種の流量の調整があり、コア用とクラッド用の複数本のバーナーを用いる場合は、いずれのバーナーのガス流量を調整してもよく、また、すべてのバーナーで調整してもよいが、クラッド用バーナーで調整するのが好ましい。
【００１０】
ガス流量の調整においては、上記成長長さとガラス微粒子堆積体の増加重量のほかに、さらにその長さの成長に要した時間もフィードバックして行うことができる。
具体的には例えば、下記の式（１）の値が０．００４〜１．２（Ｌ／ｇ）となるように原料ガス流量を調整するのが好ましく、０．４〜０．８（Ｌ／ｇ）となるように行うのがさらに好ましい。複数本のバーナーで流量を調整する場合は、各々の原料流量が前記条件を満たすようにするのが好ましい。
【００１１】
（｜調整後の原料ガス流量−調整前の原料ガス流量｜×成長長さ）／（｜測定増加重量−目標増加重量｜×成長速度） （１）
式中、成長長さは測定開始からフィードバック時までのガラス微粒子堆積体の軸方向の成長長さ（ｍｍ）を指し、成長速度はこの間のガラス微粒子堆積体の軸方向の平均成長速度（ｍｍ／分）を指す。目標増加重量は予め定めた前記成長長さにおける目標増加重量（ｇ）であり、測定増加重量は測定開始時からフィードバック時までのガラス微粒子堆積体の増加重量（ｇ）である。原料ガス流量は単位時間当たりの原料ガス流量（ＳＬＭ）とする。なお、測定増加重量が目標増加重量と等しいときは、原料ガス流量の調整は行わず、そのままの原料ガス流量で製造を継続するものとする。
【００１２】
なお、式（１）の値を上記範囲として原料流量を調整する場合は、ガラス微粒子堆積体の平均成長速度が０．８３〜２．５０ｍｍ／分であることが好ましく、１．３３〜２．００ｍｍ／分であることがさらに好ましい。
式（１）の値が小さすぎたり大きすぎたりすると、調整量が小さすぎたり大きすぎたりすることになるので、ガラス微粒子堆積体の増加重量が目標をはずれ、ガラス微粒子堆積体の外径（あるいはＤ／ｄ）や屈折率が安定しなくなる。
上記式（１）において、１ロットで複数回フィードバックを行う場合は、その都度、測定開始されるとして扱う。
【００１３】
次に本発明のガラス母材製造方法を、図１を参照して説明する。
図１において１はダミーガラスロッド２上に堆積しているガラス微粒子堆積体であり、４は反応容器、５は排気管である。ガラス微粒子堆積体１が堆積したダミーガラスロッド２は支持棒３によって昇降装置６に接続され、ガラス微粒子堆積体１の成長に応じて引上げられていく。このときの引上げ速度は、レーザー発振器８からのレーザー光を受ける受光器９からの入射光強度の情報を受けた引上げ速度制御装置７によって、ガラス微粒子堆積体１の下端が同じ位置にあるように制御される。堆積されていくガラス微粒子堆積体１の重量は、逐次チャック部に設置されたロードセル（重量測定器）１４で監視され、測定開始時に演算装置１０へ送られる。そして成長長さは引上げ速度制御装置７から演算装置１０へ、ガラス微粒子堆積体１の重量はチャック部に設置されたロードセル１４から演算装置１０へ送られ、演算装置１０では予め設定された成長長さに実際の成長長さが達した段階で、測定増加重量、及び予め設定された単位長さ分の目標増加重量の情報から、ガス流量の調整量を算出し、ガス供給装置１１にこの調整量が指令値として伝えられ、コア用バーナー１２及び／又はクラッド用バーナー１３の原料流量等が調整される。この原料流量の調整量の算出においては、上述の式（１）を用いることができる。
【００１４】
【実施例】
次に本発明を実施例及び比較例により更に具体的に説明する。なお、本発明は下記実施例中に記述した材料、組成、及び作成方法に何等限定されるものではない。
【００１５】
実施例１
図１に示す装置を用いてガラス微粒子の堆積を行う。ダミーガラスロッド２に直径２５ｍｍ、長さ４００ｍｍの純石英ガラスを使用する。反応器４下部に設置されたレーザー発振器８からガラス微粒子堆積体１の最下端付近へレーザーを出射し、受光器９で受け、受光パワーを一定に保つように引上げ速度制御装置７にて引上げ速度を制御しながら昇降装置６でガラス微粒子堆積体１を引上げる。同時に引上げ速度の情報を演算装置１０に送る。さらに昇降装置６の支持棒を掴むチャック部に設置されたロードセル１４でガラス微粒子堆積体１の増加重量がモニターできるようにし、得られた増加重量も演算装置１０に転送する。ガラス微粒子堆積体１の成長が定常状態になってから軸方向で２００ｍｍ成長するまでの増加重量を測定し、目標の増加重量１０００ｇ／２００ｍｍに対し、９００ｇ／２００ｍｍの増加重量を得、クラッドバーナーの原料ガス流量を３．３ＳＬＭから３．７ＳＬＭに調整する。なお、２００ｍｍ成長する間の平均成長速度は１．５ｍｍ／分である。作製したガラス微粒子堆積体をＨｅ／Ｏ２／塩素の混合雰囲気中で１１００℃に加熱した後、Ｈｅ雰囲気中で１５５０℃に加熱して透明ガラス化し、ガラス母材の製造を行う。（サンプルＮｏ．１）
同様に、初期のクラッドバーナーの原料ガス流量は３．３ＳＬＭとして、成長定常化後、表１に示した一定長さ成長後に１回クラッドバーナーの原料ガス流量を調整し、サンプルＮｏ．２〜６を作製する。
サンプル数（Ｎ）６において、製造されたガラス母材のコアの屈折率は、目標値０．３５％に対し０．３５±０．００３％と安定している。また、コア外径（ｄ）とクラッド外径（Ｄ）の比率（Ｄ／ｄ）は４±０．０２である。
各々のフィードバック時の目標増加重量に対する増加重量の偏差、原料流量調整量、測定時間内の成長長さ及び成長速度、式（１）で求められる値、屈折率、Ｄ／ｄを表１に示した。
【００１６】
比較例１
単位長さあたりに増加するガラス微粒子堆積体の重量の測定、管理を行わず、クラッドバーナーの原料ガス流量を３．３ＳＬＭのまま変えなかった以外は実施例１と同様にして、サンプルＮｏ．７〜１１の５本のガラス母材の製造を行うと、屈折率は０．３５±０．０１５％、Ｄ／ｄは４±０．０４である。
【００１７】
実施例２
実施例１と同様にガラス母材の製造を行い、成長の定常化後２００ｍｍ成長したときの増加重量が、目標増加重量１０００ｇ／２００ｍｍであるのに対し９００ｇ／２００ｍｍの増加重量を得、クラッドバーナーの原料流量を３．３ＳＬＭから４．５ＳＬＭに調整する。この間の成長速度は１．５ｍｍ／分である。実施例１と同様にして透明ガラス化を行い、サンプルＮｏ．１２のガラス母材の製造を行うと、屈折率は０．３６％、Ｄ／ｄは４．０４である。
【００１８】
【表１】

Figure 2004307235
【００１９】
実施例１及び２ではクラッドバーナーの原料ガス流量のみを調整したが、同時に酸素、水素流量等を調整しても同様の効果が得られる。このときは原料ガス流量の上下にあわせるように酸素、水素流量等を調整する。
また、コアバーナーの原料ガス流量、酸素、水素の流量等も同様に調整可能である。
【００２０】
【発明の効果】
以上説明したように、本発明によれば、単位長さ当りのガラス微粒子の実着量を一定範囲内とすることができ、ガラス母材の外径（あるいはクラッド径Ｄ／コア径ｄ）の安定したガラス母材が得られ、それにより屈折率も目標値に近づけることができる。各ロットで同様に本発明を適用することにより、ロット間での外径や屈折率のばらつきを抑制できるという効果を奏する。
【図面の簡単な説明】
【図１】本発明のガラス母材製造方法を用いた装置を模式的に示した説明図である。
【符号の説明】
１ ガラス微粒子堆積体
２ ダミーガラスロッド
３ 支持棒
４ 反応容器
５ 排気管
６ 昇降装置
７ 引上げ速度制御装置
８ レーザー発振器
９ 受光器
１０ 演算装置
１１ 原料ガス、一般ガス供給装置
１２ コア用バーナー
１３ クラッド用バーナー
１４ ロードセル（重量測定器）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a glass base material using a VAD method, and includes an outer diameter (a ratio D / d of a clad outer diameter D to a core outer diameter d when a plurality of burners are used) and a refractive index. The present invention relates to a method for manufacturing a glass preform for an optical fiber in which the core refractive index Δn when a plurality of burners is used is stable within and between lots.
[0002]
[Prior art]
As a method of stabilizing the rate of weight increase in the production of glass preforms for optical fibers by the VAD method, the weight of the growth base material is monitored sequentially, and the deviation of the weight increase is fed back to the oxyhydrogen amount, the raw material supply amount, and the exhaust amount. Japanese Patent Application Laid-Open No. H11-163,087 proposes a technique for making the growth density of a growth base material always uniform.
However, in this method, the glass base material is grown such that the weight of the deposited glass per unit time is constant as a whole, and thus the actual amount of glass particles deposited in the radial direction is not necessarily stabilized. That is, even if the actual amount of glass particles deposited in the radial direction is smaller (larger) than the target, if a large amount (small) of glass particles is deposited in the axial direction, the weight of the deposited glass as a whole becomes constant. It is.
[0003]
If the actual deposition amount of the glass fine particles in the radial direction is not stable, the glass fine particle deposit is heated to be transparently vitrified, and then the outer diameter of the glass base material or the ratio of the outer diameter of the clad to the outer diameter of the core (D / d). ) Is not stable, and the refractive index fluctuates with a change in the outer diameter of the base material, which adversely affects the quality of the optical fiber.
In addition, it is desirable that the amount of glass particles deposited in the radial direction is not only stable within a lot, but is also stable and stable between lots.
[0004]
[Patent Document 1]
JP-B-61-3296 (page 2, line 3, column 20 to column 4, line 14)
[0005]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems, and has a stable outer diameter (D / d when a plurality of burners are used) within a lot and between lots, and has a stable refractive index. It is an object of the present invention to provide a method for manufacturing a glass base material for use.
[0006]
[Means for Solving the Problems]
The inventor has made it possible to solve the above-mentioned problem by adopting the following configuration.
1. In a method of manufacturing a glass base material for an optical fiber, a glass fine particle deposit is produced by a VAD method, and the obtained glass fine particle deposit is heated to a high temperature to produce a transparent glass preform. The weight of the deposit and the growth length in the axial direction are measured, and the deviation between the measured increase weight and the target increase weight per unit length of the glass fine particle deposit is determined by at least one selected from a raw material gas, a combustible gas, and a combustible gas. Wherein the amount of glass particles deposited in the radial direction is adjusted by feeding back to the flow rate of the glass base material.
2. 2. The method for producing a glass base material according to the above item 1, wherein the flow rate of the raw material gas is adjusted so that the value of the following formula (1) is 0.004 to 1.2 (L / g).
(| Source gas flow rate after adjustment-source gas flow rate before adjustment | x growth length) / (| measured increase weight-target increase weight | x growth rate) (1)
(The growth length refers to the axial growth length (mm) of the glass fine particle deposit from the start of measurement to the time of feedback, and the growth rate is the average growth speed (mm / min) of the glass fine particle deposit during this period. The target increased weight is the increased weight (g) at the predetermined growth length, and the measured increased weight is the increased weight (g) of the glass fine particle deposit from the start of the measurement to the feedback. The flow rate is a source gas flow rate per unit time (SLM) .If the measured increase weight is equal to the target increase weight, the production gas flow rate is not adjusted and the production is continued at the raw gas flow rate. Yes.)
3. After the start of the deposition of the glass fine particles, when the growth of the glass fine particle deposit becomes a steady state, the measurement of the axial growth length of the glass fine particle deposit is started. 3. The method for producing a glass base material according to the above 1 or 2, wherein the weight increase from the start of the measurement of the growth length of the body is fed back.
4. 4. The method for producing a glass base material according to the above item 3, wherein the predetermined length is 200 mm or less.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method of manufacturing a glass base material according to the present invention, the length of growth of the glass fine particle deposit in the axial direction (so-called pulling length; (Hereinafter referred to simply as the growth length) is measured and monitored, and the amount of glass deposition is adjusted so that the increased weight per unit length approaches a predetermined target value. For example, the growth length (unit length) of the glass fine particle deposit for performing feedback and the target increase weight for the length are determined in advance, and when the glass deposit has grown to the unit length after the start of measurement. In addition, a method can be adopted in which a deviation between the target increased weight and the actual increased weight of the glass deposit is obtained, and the deviation is fed back to the gas flow rate and reflected in the adjustment of the deposition amount of the glass fine particles.
[0008]
Feedback may be repeated a plurality of times during one lot, but once is sufficiently effective. In particular, setting the same target weight increase at the same timing in each lot reduces the variation between lots. Can be done. At this timing, after the deposition of the glass fine particles is started, feedback is performed when the growth of the glass fine particle volume has reached a steady state, or when the measurement has started from the lower end of the start glass rod and has reached a certain growth length. Is effective. This is because the deposition density and the outer diameter are most unstable in the initial stage of the deposition. In this case, the growth length for performing the feedback is preferably 200 mm or less after the growth of the glass fine particle deposit is in a steady state, more preferably 300 mm or less from the lower end of the start glass rod, and 100 to 300 mm from the lower end of the start glass rod. More preferred. If the growth length at the time of performing the feedback is too long, the defective portion becomes long when the portion until the feedback is performed becomes defective. If the length is too short, the weight cannot be adjusted to the desired increased weight due to insufficient measurement accuracy.
When feedback is performed a plurality of times repeatedly, it is preferable to start measurement when the growth of the glass fine particle volume has reached a steady state, and to provide feedback for each of the above growth lengths.
[0009]
As a method of adjusting the deposition amount of the glass fine particles, there is an adjustment of at least one flow rate selected from a raw material gas, a combustible gas, and a combustible gas, and when using a plurality of burners for a core and a clad, The gas flow rate of the burner may be adjusted, or may be adjusted for all burners, but is preferably adjusted for the clad burner.
[0010]
Adjustment of the gas flow rate can be performed by feeding back the time required for the growth of the length in addition to the growth length and the increased weight of the glass fine particle deposit.
Specifically, for example, it is preferable to adjust the flow rate of the source gas so that the value of the following equation (1) is 0.004 to 1.2 (L / g), and 0.4 to 0.8 (L / g). / G). When the flow rate is adjusted by a plurality of burners, it is preferable that each raw material flow rate satisfies the above condition.
[0011]
(| Source gas flow rate after adjustment-source gas flow rate before adjustment | x growth length) / (| measured increase weight-target increase weight | x growth rate) (1)
In the formula, the growth length refers to the axial growth length (mm) of the glass fine particle deposit from the start of measurement to the feedback, and the growth rate is the average axial growth rate (mm / mm) of the glass fine particle deposit during this period. Minutes). The target increase weight is the target increase weight (g) at the predetermined growth length, and the measurement increase weight is the increase weight (g) of the glass particle deposit from the start of measurement to the time of feedback. The source gas flow rate is a source gas flow rate per unit time (SLM). When the measured increase weight is equal to the target increase weight, the production is continued at the raw gas flow rate without adjusting the raw gas flow rate.
[0012]
When adjusting the flow rate of the raw material with the value of the formula (1) being in the above range, the average growth rate of the glass fine particle deposit is preferably 0.83 to 2.50 mm / min, preferably 1.33 to 2.3. More preferably, it is 00 mm / min.
If the value of the expression (1) is too small or too large, the adjustment amount will be too small or too large. Therefore, the increase in the weight of the glass fine-particle deposit is out of the target, and the outer diameter of the glass fine-particle deposit ( Alternatively, D / d) and the refractive index become unstable.
In the above equation (1), when feedback is performed a plurality of times in one lot, it is treated that measurement is started each time.
[0013]
Next, the method for producing a glass base material of the present invention will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes a glass fine particle deposit on the dummy glass rod 2, reference numeral 4 denotes a reaction vessel, and reference numeral 5 denotes an exhaust pipe. The dummy glass rod 2 on which the glass fine particle deposit 1 has been deposited is connected to the elevating device 6 by the support rod 3, and is pulled up as the glass fine particle deposit 1 grows. At this time, the pulling speed is controlled by the pulling speed control device 7 which has received the information on the intensity of the incident light from the light receiver 9 which receives the laser beam from the laser oscillator 8 so that the lower end of the glass particle deposit body 1 is at the same position. Controlled. The weight of the glass particle deposit body 1 to be deposited is sequentially monitored by a load cell (weight measuring device) 14 installed in the chuck unit, and sent to the arithmetic unit 10 at the start of measurement. The growth length is sent from the pulling speed control device 7 to the arithmetic device 10, and the weight of the glass fine particle deposit 1 is sent to the arithmetic device 10 from the load cell 14 installed in the chuck portion. At the stage when the actual growth length has reached, the adjustment amount of the gas flow rate is calculated from the measured increase weight and the information of the target increase weight for a preset unit length. The amount is transmitted as a command value, and the raw material flow rate of the core burner 12 and / or the clad burner 13 is adjusted. In calculating the adjustment amount of the raw material flow rate, the above equation (1) can be used.
[0014]
【Example】
Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to the materials, compositions, and preparation methods described in the following examples.
[0015]
Example 1
Glass particles are deposited using the apparatus shown in FIG. Pure silica glass having a diameter of 25 mm and a length of 400 mm is used for the dummy glass rod 2. A laser is emitted from a laser oscillator 8 installed in the lower part of the reactor 4 to the vicinity of the lowermost end of the glass particle deposit body 1, received by a light receiver 9, and pulled up by a pulling speed control device 7 so as to keep the received light power constant. The glass particle deposit 1 is pulled up by the lifting device 6 while controlling. At the same time, information on the pulling speed is sent to the arithmetic unit 10. Further, the increase in the weight of the glass particulate deposit body 1 can be monitored by the load cell 14 installed on the chuck portion that grips the support bar of the elevating device 6, and the obtained increase in weight is also transferred to the arithmetic unit 10. The weight increase from the growth of the glass fine particle deposit 1 in a steady state to the growth of 200 mm in the axial direction was measured, and an increase in weight of 900 g / 200 mm was obtained with respect to the target increase in weight of 1000 g / 200 mm. The source gas flow rate is adjusted from 3.3 SLM to 3.7 SLM. The average growth rate during the growth of 200 mm is 1.5 mm / min. After heating the produced glass particle deposited body to 1100 ° C. in a mixed atmosphere of He / O 2 / chlorine, it is heated to 1550 ° C. in a He atmosphere to form a transparent glass, thereby producing a glass base material. (Sample No. 1)
Similarly, the raw material gas flow rate of the clad burner was initially set to 3.3 SLM, and after the growth was stabilized, the raw material gas flow rate of the clad burner was adjusted once after the growth of a constant length shown in Table 1 to obtain a sample No. Prepare 2 to 6.
With the number of samples (N) of 6, the refractive index of the core of the manufactured glass preform is stable at 0.35 ± 0.003% against the target value of 0.35%. The ratio (D / d) between the core outer diameter (d) and the clad outer diameter (D) is 4 ± 0.02.
Table 1 shows the deviation of the weight gain from the target weight gain at the time of each feedback, the raw material flow rate adjustment amount, the growth length and growth rate within the measurement time, the value obtained by the equation (1), the refractive index, and D / d. Was.
[0016]
Comparative Example 1
Sample No. was prepared in the same manner as in Example 1 except that the weight of the glass fine particle deposit increasing per unit length was not measured and controlled, and the raw material gas flow rate of the clad burner was not changed to 3.3 SLM. When five glass base materials 7 to 11 are manufactured, the refractive index is 0.35 ± 0.015% and D / d is 4 ± 0.04.
[0017]
Example 2
A glass base material was manufactured in the same manner as in Example 1, and the increased weight when growing 200 mm after the steady growth was 900 g / 200 mm, compared to the target increased weight of 1000 g / 200 mm. Is adjusted from 3.3 SLM to 4.5 SLM. The growth rate during this period is 1.5 mm / min. Transparent vitrification was performed in the same manner as in Example 1. When manufacturing the glass base material of No. 12, the refractive index is 0.36% and D / d is 4.04.
[0018]
[Table 1]
Figure 2004307235
[0019]
In Embodiments 1 and 2, only the flow rate of the raw material gas of the clad burner is adjusted. However, the same effect can be obtained by adjusting the flow rates of oxygen and hydrogen at the same time. At this time, the flow rates of oxygen, hydrogen, and the like are adjusted so as to match the flow rate of the raw material gas.
Also, the flow rate of the raw material gas of the core burner, the flow rates of oxygen and hydrogen, and the like can be similarly adjusted.
[0020]
【The invention's effect】
As described above, according to the present invention, the actual amount of glass particles per unit length can be kept within a certain range, and the outer diameter (or clad diameter D / core diameter d) of the glass base material can be reduced. A stable glass preform is obtained, so that the refractive index can also approach the target value. By applying the present invention similarly to each lot, there is an effect that variations in outer diameter and refractive index between lots can be suppressed.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing an apparatus using a glass base material manufacturing method of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Glass fine particle deposit 2 Dummy glass rod 3 Support rod 4 Reaction vessel 5 Exhaust pipe 6 Lifting device 7 Pulling speed control device 8 Laser oscillator 9 Optical receiver 10 Operation device 11 Raw material gas, general gas supply device 12 Core burner 13 For cladding Burner 14 load cell (weight measuring device)

Claims (4)

ＶＡＤ法によりガラス微粒子堆積体を作製し、得られたガラス微粒子堆積体を高温加熱して透明ガラス母材を製造する光ファイバ用ガラス母材の製造方法において、ガラス微粒子の堆積中に逐次ガラス微粒子堆積体の重量と軸方向の成長長さを測定し、ガラス微粒子堆積体の単位長さあたりの測定増加重量と目標増加重量の偏差を原料ガス、可燃性ガス及び助燃性ガスから選ばれる少なくとも一種の流量にフィードバックして、径方向のガラス微粒子堆積量を調整することを特徴とするガラス母材の製造方法。In a method of manufacturing a glass base material for an optical fiber, a glass fine particle deposit is produced by a VAD method, and the obtained glass fine particle deposit is heated to a high temperature to produce a transparent glass preform. The weight of the deposit and the growth length in the axial direction are measured, and the deviation between the measured increase weight and the target increase weight per unit length of the glass fine particle deposit is determined by at least one selected from a raw material gas, a combustible gas, and a combustible gas. Wherein the amount of glass particles deposited in the radial direction is adjusted by feeding back to the flow rate of the glass base material. 下記式（１）の値が０．００４〜１．２（Ｌ／ｇ）となるよう原料ガス流量を調整することを特徴とする請求項１記載のガラス母材の製造方法。
（｜調整後の原料ガス流量−調整前の原料ガス流量｜×成長長さ）／（｜測定増加重量−目標増加重量｜×成長速度） （１）
（成長長さは測定開始からフィードバック時までのガラス微粒子堆積体の軸方向の成長長さ（ｍｍ）を指し、成長速度はこの間のガラス微粒子堆積体の軸方向の平均成長速度（ｍｍ／分）を指す。目標増加重量は予め定めた前記成長長さにおける増加重量（ｇ）であり、測定増加重量は測定開始時からフィードバック時までのガラス微粒子堆積体の増加重量（ｇ）である。原料ガス流量は単位時間当たりの原料ガス流量（ＳＬＭ）とする。なお、測定増加重量が目標増加重量と等しいときは、原料ガス流量の調整は行わず、そのままの原料ガス流量で製造を継続するものとする。）The method according to claim 1, wherein the flow rate of the raw material gas is adjusted so that the value of the following equation (1) is 0.004 to 1.2 (L / g).
(| Source gas flow rate after adjustment-source gas flow rate before adjustment | x growth length) / (| measured increase weight-target increase weight | x growth rate) (1)
(The growth length refers to the axial growth length (mm) of the glass fine particle deposit from the start of measurement to the feedback, and the growth rate is the average axial growth rate (mm / min) of the glass fine particle deposit during this period. The target increased weight is the increased weight (g) at the predetermined growth length, and the measured increased weight is the increased weight (g) of the glass particle deposit from the start of the measurement to the feedback. The flow rate is a source gas flow rate per unit time (SLM) .If the measured increase weight is equal to the target increase weight, the production gas flow rate is not adjusted and the production is continued at the raw gas flow rate. Yes.) ガラス微粒子の堆積開始後、ガラス微粒子堆積体の成長が定常状態になったところでガラス微粒子堆積体の軸方向の成長長さの測定を開始し、予め定めた一定の長さ成長したところでガラス微粒子堆積体の成長長さ測定開始時からの増加重量をフィードバックすることを特徴とする請求項１又は２記載のガラス母材の製造方法。After the start of the deposition of the glass fine particles, when the growth of the glass fine particle deposit becomes a steady state, the measurement of the axial growth length of the glass fine particle deposit is started. 3. The method for producing a glass base material according to claim 1, wherein the weight increased from the start of the measurement of the growth length of the body is fed back. 前記一定の長さが２００ｍｍ以下である請求項３記載のガラス母材の製造方法。The method for producing a glass base material according to claim 3, wherein the predetermined length is 200 mm or less.
JP2003100290A 2003-04-03 2003-04-03 Method of manufacturing glass preform for optical fiber Pending JP2004307235A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2003100290A JP2004307235A (en) 2003-04-03 2003-04-03 Method of manufacturing glass preform for optical fiber

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2003100290A JP2004307235A (en) 2003-04-03 2003-04-03 Method of manufacturing glass preform for optical fiber

Publications (1)

Publication Number Publication Date
JP2004307235A true JP2004307235A (en) 2004-11-04

Family

ID=33464476

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2003100290A Pending JP2004307235A (en) 2003-04-03 2003-04-03 Method of manufacturing glass preform for optical fiber

Country Status (1)

Country Link
JP (1) JP2004307235A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103449716A (en) * 2013-08-28 2013-12-18 长飞光纤光缆有限公司 Device and method for manufacturing optical fiber preform rod with VAD (Vapor Axial Deposition) method
CN104513006A (en) * 2013-10-04 2015-04-15 住友电气工业株式会社 Method for manufacturing glass base materials for optical fibers

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103449716A (en) * 2013-08-28 2013-12-18 长飞光纤光缆有限公司 Device and method for manufacturing optical fiber preform rod with VAD (Vapor Axial Deposition) method
CN104513006A (en) * 2013-10-04 2015-04-15 住友电气工业株式会社 Method for manufacturing glass base materials for optical fibers

Similar Documents

Publication Publication Date Title
KR20010053022A (en) Method and apparatus for manufacturing a rare earth metal doped optical fiber preform
EP0634372A1 (en) Method of manufacturing single-mode optical fiber preform
JP2010024102A (en) Method and apparatus for producing quartz glass
JP5578024B2 (en) Manufacturing method of glass base material
JPH04317431A (en) Method of manufacturing optical fiber transmission path
US20070137256A1 (en) Methods for optical fiber manufacture
JP2004307235A (en) Method of manufacturing glass preform for optical fiber
JPH07215727A (en) Optical fiber preform and its production
US6923024B2 (en) VAD manufacture of optical fiber preforms with improved deposition control
US6834516B2 (en) Manufacture of optical fiber preforms using modified VAD
JP2005075682A (en) Method of manufacturing porous glass preform
JP2003261336A (en) Method for manufacturing transparent glass preform
US20030209516A1 (en) Optical fiber preform manufacture using improved VAD
JP5609050B2 (en) Method for producing synthetic quartz glass base material and synthetic quartz glass base material
JP5087929B2 (en) Method for producing glass particulate deposit
JP4483434B2 (en) Manufacturing method of glass base material
JPH09221335A (en) Production of precursor of optical fiber glass preform
JP2006096608A (en) Method for producing glass preform
JP3675581B2 (en) Method for synthesizing optical fiber base material and method for adjusting synthesis condition
JP4404214B2 (en) Manufacturing method of glass preform for optical fiber
JP4427425B2 (en) Method and apparatus for manufacturing optical fiber preform
JP2017043512A (en) Optical fiber preform manufacturing method, optical fiber manufacturing method, and lens manufacturing method
JP2001180959A (en) Manufacturing method of optical fiber
JP2938604B2 (en) Method of manufacturing preform for single mode optical fiber
CN111377605A (en) Method for manufacturing optical fiber preform

Legal Events

Date Code Title Description
A621 Written request for application examination

Effective date: 20050804

Free format text: JAPANESE INTERMEDIATE CODE: A621

RD03 Notification of appointment of power of attorney

Free format text: JAPANESE INTERMEDIATE CODE: A7423

Effective date: 20070319

A977 Report on retrieval

Effective date: 20080418

Free format text: JAPANESE INTERMEDIATE CODE: A971007

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20080507

A02 Decision of refusal

Free format text: JAPANESE INTERMEDIATE CODE: A02

Effective date: 20080916