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JP3498590B2 - Manufacturing method of preform for optical fiber - Google Patents

Manufacturing method of preform for optical fiber

Info

Publication number
JP3498590B2
JP3498590B2 JP28424598A JP28424598A JP3498590B2 JP 3498590 B2 JP3498590 B2 JP 3498590B2 JP 28424598 A JP28424598 A JP 28424598A JP 28424598 A JP28424598 A JP 28424598A JP 3498590 B2 JP3498590 B2 JP 3498590B2
Authority
JP
Japan
Prior art keywords
optical fiber
soot
glass
external
fiber preform
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.)
Expired - Lifetime
Application number
JP28424598A
Other languages
Japanese (ja)
Other versions
JP2000109333A (en
Inventor
毅 京極
宏記 長瀬
晴彦 相川
毅彦 鬼頭
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 JP28424598A priority Critical patent/JP3498590B2/en
Publication of JP2000109333A publication Critical patent/JP2000109333A/en
Application granted granted Critical
Publication of JP3498590B2 publication Critical patent/JP3498590B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01Manufacture of glass fibres or filaments
    • C03B37/012Manufacture of preforms for drawing fibres or filaments
    • C03B37/014Manufacture 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]
    • C03B37/01446Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01Manufacture of glass fibres or filaments
    • C03B37/012Manufacture of preforms for drawing fibres or filaments
    • C03B37/014Manufacture 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]
    • C03B37/01446Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
    • C03B37/0146Furnaces therefor, e.g. muffle tubes, furnace linings
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00Technologies relating to the processing of minerals
    • Y02P40/50Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57Improving the yield, e-g- reduction of reject rates

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Thermal 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)

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【発明の属する技術分野】本発明は、コア用ガラスロッ
ドの周辺に外スス付けを行い、これを透明ガラス化する
ことによる光ファイバ用母材の製造方法に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical fiber preform by applying a soot around the glass rod for core and making it into transparent glass.

【0002】[0002]

【従来の技術】従来、光ファイバ用母材の製造方法とし
てコア用ガラスロッドを作製し、該コア用ガラスロッド
の周囲に外付け法によるスス付けを行って外付けスス体
とし、このスス体を加熱透明化して光ファイバ用母材と
する方法がある。ここで外付けスス体の作製方法として
は、コア用ガラスロッドを回転させながら軸方向にガラ
ス微粒子合成用バーナに対し相対的に往復移動させ、ガ
ラス微粒子合成用バーナで合成されたガラス微粒子をガ
ラスロッドの外周に吹き付けて層状に堆積させるOVD
法(層状外付け法)、鉛直方向に配置したコア用ガラス
ロッドを回転させながら軸方向にガラス微粒子合成用バ
ーナを移動させ、コア用ガラスロッドの上部から下方に
向かって徐々にガラス微粒子を堆積させて行くVAD法
が行われている。これらの方法により作製した外付けス
ス体を、ゾーン加熱炉を使用して前記外付けスス体を一
端から徐々に加熱ゾーンを通過させ、一端から徐々に透
明化していく方法、均熱炉を使用して前記外付けスス体
の全体を均一に加熱し透明化する方法などによって加熱
透明化し、光ファイバ用母材とする。
2. Description of the Related Art Conventionally, as a method of manufacturing a base material for an optical fiber, a glass rod for a core is manufactured, and soot is attached around the glass rod for a core by an external attachment method to form an external soot body. There is a method of heating and transparentizing to form a preform for optical fibers. Here, as a method of manufacturing the external soot body, while rotating the glass rod for the core, the glass fine particles synthesized by the burner for synthesizing the glass fine particles are reciprocally moved in the axial direction relative to the burner for synthesizing the glass fine particles. OVD that sprays on the outer circumference of the rod and deposits in layers
Method (layered external attachment method), the burner for synthesizing glass fine particles is moved in the axial direction while rotating the glass rod for core arranged vertically, and glass fine particles are gradually deposited from the upper part of the glass rod for core to the lower part. The VAD method is being carried out. The external soot body produced by these methods is a method of gradually passing the external soot body through a heating zone from one end using a zone heating furnace and gradually making it transparent from one end, using a soaking furnace. Then, the external soot body is heated and made transparent by a method of uniformly heating and making the whole soot body transparent to obtain a base material for an optical fiber.

【0003】[0003]

【発明が解決しようとする課題】前記方法においては、
外付けスス体を加熱透明化する際にコア用ガラスロッド
と外付けしたススとの境界面に気泡が残りやすいという
問題点がある。これは、外付け技術では透明化時に大き
く収縮する外付けススと収縮しないコア用ガラスロッド
との間で引張力が生じ、ガラス構造内に空隙を作りやす
い状態となっている、外側から加熱するために表面から
透明化が進む傾向があり、母材全体の表面で透明化が先
に進んでしまうと空隙内に存在する残存ガスの逃げ道が
なくなり、気泡として残存する、などの理由による。な
お、両端の非有効部では熱源からの距離が遠くなるの
で、傾斜部分の表面からの熱と母材内部から伝導する熱
とのバランスで若干様子が異なる場合もある。特にVA
D法による外付けスス体の場合には、上方のスス付け開
始部分ではススとガラスを密着させるため、円柱状の有
効部に比較してススのかさ密度を高くしていることが多
く、この部分が先に透明化してしまい、気泡となるガス
の逃げ道を閉止してしまう場合があり、ゾーン加熱炉に
よる透明化の際に加熱終了側の非有効部近傍に気泡が多
く残りやすくなっている。このような気泡の残留は、光
ファイバとした際の光の伝送特性上好ましくなく、極力
取り除く必要がある。
SUMMARY OF THE INVENTION In the above method,
There is a problem that bubbles tend to remain on the boundary surface between the glass rod for core and the soot attached externally when the external soot body is heated and made transparent. This is because in the external technology, a tensile force is generated between the external soot that contracts significantly during the transparentization and the core glass rod that does not contract, and it is easy to create voids in the glass structure. Therefore, there is a tendency that the surface becomes transparent, and if the surface of the entire base material becomes transparent first, the residual gas existing in the voids will not escape and will remain as bubbles. In addition, since the distance from the heat source is long in the ineffective portions at both ends, the situation may be slightly different depending on the balance between the heat from the surface of the inclined portion and the heat conducted from the inside of the base material. Especially VA
In the case of an external soot body formed by the D method, the soot and glass are brought into close contact with each other at the upper sooting start portion, so that the bulk density of soot is often higher than that of the cylindrical effective portion. There is a case where the part becomes transparent first, and the escape path of gas that becomes bubbles may be closed, and it is easy for many bubbles to remain near the non-effective part on the heating end side when transparentizing by the zone heating furnace. . Such bubbles remain unfavorable in light transmission characteristics when used as an optical fiber and must be removed as much as possible.

【0004】特開昭49−9523号公報には、高品質
の光学的導波管、レンズなどに用いられるブランク(b
lank)の形の、水を含有しない光学的高品質の溶融
シリカを製造する方法として、芯材上に珪素含有ススを
付着させてプリフォームを形成し、前記ススを焼結する
のに十分な速度でかつ前記ススが焼結して芯の周りに収
縮するとき、取り込まれていたガスが炉の厚い区域に未
だきていないススの部分を通って逃げることが可能な速
度で、ススの層を徐々に炉中へ挿入していく方法が開示
されている。この方法では、ゾーン加熱法を用いること
により円柱状となる有効部分においてはガスの脱出経路
を維持できるが、加熱を終了する非有効部では気泡が閉
じ込められやすいという問題がある。また、特開昭53
−67447号公報には、ガラス形成用気相原料を酸化
あるいは加水分解してガラススートを合成し、これを回
転し移動する棒状出発部材上に積層させ、このスート積
層体を焼結し、透明ガラス体を得、これを光ファイバ用
母材とする方法において、前記スートを棒状出発部材上
に積層させた後の個所に集光された赤外線(CO2 レー
ザー)を照射しながらガラス膜を形成していくことを特
徴とする光ファイバ用母材の製造方法が開示されてい
る。この方法は本発明の方法と若干技術内容が異なるも
のであるが、この方法ではレーザーによる透明化が工程
の速度を決めることになり、生産性(堆積速度)の向上
が難しい。
Japanese Laid-Open Patent Publication No. 49-9523 discloses a blank (b) used for high-quality optical waveguides, lenses, etc.
A method of producing optically high quality fused silica containing no water in the form of a land) is sufficient to deposit a silicon-containing soot on a core material to form a preform and sinter the soot. A layer of soot at a rate that allows the entrapped gas to escape through the portion of the soot that is not yet in the thick zone of the furnace as the soot is sintered and contracts around the core. Is gradually inserted into the furnace. With this method, the gas escape path can be maintained in the cylindrical effective portion by using the zone heating method, but there is the problem that air bubbles are easily trapped in the ineffective portion where heating is terminated. In addition, JP-A-53
JP-A-67447 discloses that a glass-forming gas phase raw material is oxidized or hydrolyzed to synthesize glass soot, which is laminated on a rotating and moving rod-shaped starting member, and the soot laminate is sintered to obtain a transparent material. In a method of obtaining a glass body and using this as a base material for an optical fiber, a glass film is formed while irradiating a focused infrared ray (CO 2 laser) at a position after laminating the soot on a rod-shaped starting member. A method of manufacturing a preform for an optical fiber is disclosed. This method has a slightly different technical content from the method of the present invention, but in this method, the transparency by the laser determines the speed of the process, and it is difficult to improve the productivity (deposition rate).

【0005】本発明はこのような従来技術の実状に鑑
み、外付けスス体からの気泡の残留が少ない光ファイバ
用母材の製造方法を提供しようとするものである。
In view of the state of the art as described above, the present invention intends to provide a method of manufacturing a base material for an optical fiber in which air bubbles from the external soot body are less likely to remain.

【0006】[0006]

【課題を解決するための手段】本発明は、前記課題を解
決する手段として次の(1)〜(6)の態様を含むもの
である。 (1)コア用ガラスロッドの周囲に外付け法によりスス
付けを行い、得られた外付けスス体を熱処理して透明ガ
ラス化する光ファイバ用母材の製造方法において、透明
ガラス化の際に、光ファイバ用母材の両端の非有効部の
いずれか一方又は両方の少なくとも一部分を不透明ガラ
ス状態で残すことを特徴とする光ファイバ用母材の製造
方法。 (2)外付け法によるスス付けを、外付け法によるスス
付けを、鉛直方向にコア用ガラスロッドを配置し、縦方
向にススを成長させるVAD法により行うことを特徴と
する前記(1)の光ファイバ用母材の製造方法。 (3)不透明ガラス状態部分を残す非有効部として、上
方に位置するスス付け開始部分を選択することを特徴と
する前記(2)の光ファイバ用母材の製造方法。 (4)外付け法によるスス付けを、コア用ガラスロッド
の周囲に、層状にスス付けを行うOVD法により行うこ
とを特徴とする前記(1)の光ファイバ用母材の製造方
法。 (5)外付けスス体の透明ガラス化をゾーン加熱炉を用
いて行い、前記外付けスス体の加熱終了位置を調整する
ことにより不透明ガラス状態部分を形成させることを特
徴とする前記(1)〜(4)のいずれか1つの光ファイ
バ用母材の製造方法。 (6)外付けスス体の透明ガラス化を均熱炉を用いて行
い、両端の非有効部のいずれか一方又は両方の少なくと
も一部分が、均熱範囲に入らないようにすることによ
り、該非有効部に不透明ガラス状態部分を形成させるこ
とを特徴とする前記(1)〜(4)のいずれか1つの光
ファイバ用母材の製造方法。
The present invention includes the following aspects (1) to (6) as means for solving the above problems. (1) In a method for producing an optical fiber preform in which soot is attached around the glass rod for a core by an external attachment method, and the obtained externally attached soot body is heat-treated to be transparent vitrified. A method for producing an optical fiber preform, characterized in that at least a part of one or both of the ineffective portions at both ends of the optical fiber preform is left in an opaque glass state. (2) The soot attachment by the external attachment method is performed by the VAD method of arranging the glass rod for the core in the vertical direction and growing the soot in the vertical direction. Manufacturing method of optical fiber preform. (3) The method for producing an optical fiber preform according to (2) above, wherein the sooting start portion located above is selected as an ineffective portion that leaves the opaque glass state portion. (4) The method for producing an optical fiber preform according to the above (1), wherein the soot attachment by the external attachment method is performed by the OVD method in which the soot is layered around the glass rod for core. (5) The opaque glass state portion is formed by performing transparent vitrification of the external soot body using a zone heating furnace and adjusting the heating end position of the external soot body. (4) A method for manufacturing an optical fiber preform according to any one of (4). (6) By performing transparent vitrification of the external soot body using a soaking furnace, at least part of either or both of the ineffective portions at both ends is prevented from entering the soaking range, thereby making the ineffective portion. An opaque glass state portion is formed in the portion, and the method for producing an optical fiber preform according to any one of (1) to (4) above.

【0007】[0007]

【発明の実施の形態】本発明においては、先ずコア用ガ
ラスロッドを作製し、その表面に(ガラスロッドの周囲
に)VAD法、OVD法などの外付け法によりガラス微
粒子合成用バーナで合成したガラス微粒子を堆積させる
スス付けを行う。得られる外付けスス体(ガラス微粒子
堆積体)は図1に模式的に示すようにコア用ガラスロッ
ド2の周囲にガラス微粒子の堆積層(スス層)3が形成
されている。この外付けスス体1は中央部の有効部(光
ファイバとした際に製品として使用可能な部分)の両端
に非有効部(光ファイバとした際に特性が不安定で製品
として使用できない部分)が形成される。
BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, first, a glass rod for core is prepared and synthesized on the surface thereof (around the glass rod) by a burner for synthesizing glass particles by an external method such as VAD method or OVD method. Soot is applied to deposit fine glass particles. In the obtained external soot body (glass particulate deposit body), a glass particulate deposit layer (soot layer) 3 is formed around a core glass rod 2 as schematically shown in FIG. The external soot body 1 has a non-effective portion (a portion which cannot be used as a product due to unstable characteristics when used as an optical fiber) at both ends of an effective portion (a portion which can be used as a product when used as an optical fiber) in the central portion. Is formed.

【0008】次にこの外付けスス体1をゾーン加熱炉あ
るいは均熱炉などの加熱炉を用いて加熱し、透明ガラス
化して光ファイバ母材とするが、この際に図2に示すよ
うにコア用ガラスロッド2の周囲の透明ガラス層4との
境界部分に気泡5が残留しやすい。なお、図2には光フ
ァイバ母材の全長にわたって気泡が残存する例を示した
が、ゾーン加熱炉を使用する場合には加熱終了端部の非
有効部の近傍に集中する傾向がある。本発明の方法にお
いては、このような気泡の残留を抑制するため、外付け
スス体の両端部の非有効部のいずれか一方又は両方の少
なくとも一部分を不透明ガラス状態で残すことを特徴と
する。これにより透明化の最終段階まで残存ガスの逃げ
道が確保でき、気泡の残留を抑制することができる。こ
こで不透明ガラス状態とはスス付けままの状態から、一
部焼結は進行しているが残存ガスは通過できる程度に多
孔質性を残した状態までを意味する。また、不透明ガラ
ス状態で残す部分の割合は、厳密に規定する必要はなく
残存ガスが排出できる量とすればよいが、目安としては
非有効部体積の0.5〜50%、好ましくは5〜30%
程度の範囲である。
Next, the external soot body 1 is heated in a heating furnace such as a zone heating furnace or a soaking furnace to be transparent vitrified into an optical fiber preform. At this time, as shown in FIG. Bubbles 5 tend to remain at the boundary between the glass rod 2 for core and the transparent glass layer 4. Note that FIG. 2 shows an example in which bubbles remain over the entire length of the optical fiber preform, but when a zone heating furnace is used, it tends to concentrate near the ineffective portion at the end of heating. The method of the present invention is characterized in that, in order to suppress such bubbles from remaining, at least a part of one or both of the ineffective portions of both ends of the external soot body is left in an opaque glass state. As a result, an escape route for residual gas can be secured until the final stage of transparency, and bubbles can be prevented from remaining. Here, the opaque glass state means a state in which the soot is still attached, to a state in which some sintering is in progress but the remaining gas is porous enough to pass through. Further, the proportion of the portion left in the opaque glass state does not have to be strictly defined and may be an amount capable of discharging the residual gas, but as a guide, it is 0.5 to 50%, preferably 5 to 5% of the ineffective portion volume. 30%
It is a range of degrees.

【0009】非有効部に不透明ガラス状態部分を残すパ
ターンの例を図3に模式的に示す。図3において2はコ
ア用ガラスロッド、4は透明ガラス層、6は不透明ガラ
ス状態部分である。なお、不透明ガラス状態部分の形状
は加熱方法、スス体の半径方向密度分布などによって異
なり、ここには典型的な例を示した。図3(a)は一方
の非有効部の表面付近を透明ガラス化せずに不透明ガラ
ス状態で残したものである。このパターンはゾーン加熱
炉を使用し、外付けスス体の下端部から徐々に加熱ゾー
ン内に挿入して加熱ゾーンを通過させる方法の際に、上
端の非有効部を十分透明ガラス化せずに残す場合などに
形成される。具体的には、従来技術のように非有効部を
含む外付けスス体全体が加熱ゾーンを通過する前に加熱
を終了させる、加熱終了付近で炉の温度を下げるなどの
手法を採ることができる。図3(b)は一方の非有効部
の大部分を透明ガラス化せずに不透明ガラス状態で残し
たものである。このパターンは均熱炉を使用し、一方の
非有効部を均熱範囲外として加熱し、透明ガラス化する
場合等に形成される。図3(c)はゾーン加熱炉を使用
し、外付けスス体を加熱ゾーンの下方に位置させて徐々
に上昇させながら透明化を進め、透明化終了時に下端の
非有効部が不透明ガラス状態で残るようにしたものであ
る。VAD法により作製された外付けスス体の場合、上
部のスス付け開始部分にガスの残留が生じやすい傾向が
あるので、この手法により上部非有効部を先に透明化
し、ガスの残留を防ぐことが考えられる。
An example of a pattern in which an opaque glass state portion is left in an ineffective portion is schematically shown in FIG. In FIG. 3, 2 is a glass rod for core, 4 is a transparent glass layer, and 6 is an opaque glass state portion. The shape of the opaque glass state portion depends on the heating method, the radial direction density distribution of the soot body, and the like, and a typical example is shown here. FIG. 3 (a) shows that the vicinity of the surface of one ineffective portion is not made into transparent glass but is left in an opaque glass state. This pattern uses a zone heating furnace and gradually inserts into the heating zone from the lower end of the external soot body and allows it to pass through the heating zone without sufficiently vitrifying the ineffective part at the upper end. It is formed when leaving. Specifically, as in the prior art, it is possible to adopt a method such as ending the heating before the entire external soot body including the ineffective portion passes through the heating zone, and lowering the temperature of the furnace near the end of heating. . FIG. 3 (b) shows that most of the non-effective portion is left as an opaque glass state without being made transparent glass. This pattern is formed, for example, when a soaking furnace is used and one of the ineffective portions is heated outside the soaking range to form transparent glass. In FIG. 3 (c), a zone heating furnace is used, and the external soot body is positioned below the heating zone to gradually raise the transparency so that the ineffective portion at the lower end is in an opaque glass state. It is the one that remains. In the case of an external soot body produced by the VAD method, gas tends to remain at the soot starting portion of the upper part, so this method should be used to make the upper ineffective part transparent first to prevent gas residue. Can be considered.

【0010】図3には非有効部の一方のみに不透明ガラ
ス状態部分を残す例を示したが、必要により両方の非有
効部に不透明ガラス状態部分を残すようにしてもよい。
なお、外付けスス体がVAD法により作製されたもので
ある場合、上方のスス付け開始部分ではススとガラスを
密着させるため、円柱状の有効部に比較してススのかさ
密度を高くしていることが多く、通常の透明化方法では
この部分が先に透明化してしまい、気泡となるガスの逃
げ道を閉止してしまう場合があるので、透明化時の剥が
れを防ぎつつ、気泡の発生を防止するためには、不透明
ガラス状態部分を残す非有効部としてスス付けを開始し
た端部の非有効部を選択するのが好ましい。また、非有
効部に不透明ガラス状態部分を残す方法は上記の例に限
定されるものではなく、外付けスス体の両端に形成され
る非有効部のいずれか一方又は両方の少なくとも一部に
不透明ガラス状態部分を残すことができるものであれば
いかなる手法を採ることもできる。
Although FIG. 3 shows an example in which the opaque glass state portion is left on only one of the non-effective portions, the opaque glass state portion may be left on both of the non-effective portions if necessary.
If the external soot body is made by the VAD method, the soot and glass are brought into close contact with each other at the upper part of the soot attachment, so that the bulk density of the soot is made higher than that of the cylindrical effective portion. In many cases, this part becomes transparent first in the usual clearing method, and it may close the escape path of gas that becomes bubbles, so while preventing peeling at the time of clearing, generation of bubbles is prevented. In order to prevent this, it is preferable to select the ineffective portion at the end where the sooting is started as the ineffective portion that leaves the opaque glass state portion. Further, the method of leaving the opaque glass state portion in the ineffective portion is not limited to the above example, and it is opaque to at least a part of one or both of the ineffective portions formed at both ends of the external soot body. Any method can be adopted as long as it can leave the glass state portion.

【0011】透明ガラス化を行う際には、できるだけ分
子直径の小さいガスの雰囲気中で行い、スス体形成時に
残った大気や水分等を除去することが望ましく、ゾーン
加熱炉及び均熱炉などいずれの炉の場合であっても、H
e雰囲気とするのが好ましい。また、Heは高価である
ことから、炉体内の雰囲気ガス気圧を下げて透明ガラス
化を行うのも効果的である。
It is desirable to carry out the transparent vitrification in an atmosphere of a gas having a molecular diameter as small as possible to remove the air, moisture and the like remaining at the time of forming the soot body. Even in the case of
An e atmosphere is preferable. Moreover, since He is expensive, it is also effective to lower the atmospheric gas pressure in the furnace body to perform transparent vitrification.

【0012】[0012]

【実施例】以下、実施例により本発明の方法をさらに具
体的に説明する。 (実施例1、比較例1)コア用ガラスロッドの有効部分
として、VAD法で製造したステップ状屈折率分布を持
つ光学コア部(比屈折率0.35%、純シリカガラスに
二酸化ゲルマニウムを微量添加したもの)と、その周囲
に光学クラッド部(純シリカガラス)を持つ2層構造の
石英ガラスロッドを有効部長さ:500mm、直径27
mmに仕上げ、その両端に非有効部用の純シリカガラス
棒を接続した。このロッドの周囲に、VAD法によりス
ス付けを行った。スス付けのガラス微粒子生成には、S
iCl4 を気化して酸素水素火炎内に導入する加水分解
法を用いた。その結果、有効部の直径が165mmの外
付けスス体を得た。有効部長さはロッドの有効部長さと
同じく500mmであり、非有効部長さは上部、下部と
もに約150mmであった。この外付けスス体をゾーン
加熱炉を使用して透明ガラス化した。図4は加熱方式及
び得られた光ファイバ母材の状態を示す模式図である。
図4の(a)に示すようにコア用ガラスロッド2の周囲
にガラス微粒子のスス層3が形成された外付けスス体1
を、スス付けを開始した上端部を上にしてゾーン加熱炉
にセットし、下端部から5mm/分の下降速度で163
0℃に調整した加熱ゾーンを通過させた。この間、加熱
ゾーンはHe雰囲気に保持した。
EXAMPLES The method of the present invention will be described in more detail below with reference to examples. (Example 1, Comparative Example 1) As an effective part of the glass rod for core, an optical core part having a stepwise refractive index distribution manufactured by the VAD method (specific refractive index 0.35%, a small amount of germanium dioxide in pure silica glass) (Added) and a quartz glass rod of a two-layer structure having an optical cladding (pure silica glass) around the effective portion length: 500 mm, diameter 27
mm, and pure silica glass rods for ineffective portions were connected to both ends thereof. Soot was applied around the rod by the VAD method. To generate soot glass particles, S
A hydrolysis method was used in which iCl 4 was vaporized and introduced into an oxygen-hydrogen flame. As a result, an external soot body having an effective portion diameter of 165 mm was obtained. The effective length was 500 mm, which was the same as the effective length of the rod, and the ineffective length was about 150 mm for both the upper and lower parts. The external soot body was vitrified into a transparent glass by using a zone heating furnace. FIG. 4 is a schematic diagram showing the heating method and the state of the obtained optical fiber preform.
As shown in FIG. 4A, an external soot body 1 in which a soot layer 3 of fine glass particles is formed around a glass rod 2 for a core.
Is set in the zone heating furnace with the upper end portion where the sooting is started up, and 163 at a descending speed of 5 mm / min from the lower end portion.
It was passed through a heating zone adjusted to 0 ° C. During this period, the heating zone was kept in He atmosphere.

【0013】図4の(b)に示すように、上部非有効部
の末端から30mmの位置まで加熱ゾーンを通過させて
スス層3の全体を透明ガラス化した比較例(従来技術)
では、コア用ガラスロッド2の周囲の透明ガラス層4と
の境界付近の上端に近い部分に気泡5の残存が認められ
た。これに対し、図4の(c)に示すように本発明の方
法により、図4の(b)の比較例よりも40mm上方で
加熱処理を終了させて上部非有効部の表面付近に白い多
孔質状態部分(不透明ガラス状態部分6)が残るように
した(コア用ガラスロッド界面付近は透明ガラス化)実
施例では、光ファイバ母材の有効部には気泡の残存は認
められなかった。
As shown in FIG. 4 (b), a comparative example in which the soot layer 3 is entirely made into transparent glass by passing through a heating zone to a position 30 mm from the end of the upper non-effective portion (prior art).
Then, it was confirmed that the bubbles 5 remained at the portion near the upper end near the boundary with the transparent glass layer 4 around the glass rod for core 2. On the other hand, as shown in FIG. 4 (c), the method of the present invention terminated the heat treatment 40 mm above the comparative example of FIG. In the example in which the quality state portion (opaque glass state portion 6) was left (the vicinity of the glass rod interface for the core was made into transparent glass), no bubbles were observed in the effective portion of the optical fiber preform.

【0014】(実施例2、比較例2)コア用ガラスロッ
ドとしては実施例1で使用したものと同様の構造を持つ
石英ガラスロッドを使用し、これを有効部長さ:550
mm、直径25mmに仕上げ、その両端に非有効部用の
純シリカガラス棒を接続した。このロッドの周囲に、O
VD法によりスス付けを行った。スス付けのガラス微粒
子生成には、SiCl4 を気化して酸素水素火炎内に導
入する加水分解法を用い、長手方向に10往復の堆積を
行い、有効部の直径が120mmの外付けスス体を得
た。有効部長さはロッドの有効部長さと同じく550m
mであり、非有効部長さは上部、下部ともに約170m
mであった。この外付けスス体を均熱炉を使用して透明
ガラス化した。図5及び図6はこの実施例、比較例にお
ける加熱方式及び得られた光ファイバ母材の状態を示す
模式図である。先ず比較例として、図5の(a)に示す
ようにコア用ガラスロッド2の周囲にガラス微粒子のス
ス層3が形成された外付けスス体1を非有効部及び有効
部の全体が均熱範囲内に入るように、1500℃に維持
したHe雰囲気の均熱炉内にセットし、90分間保持し
て透明ガラス化した。その結果得られた光ファイバ母材
には、図5の(b)に示すように、コア用ガラスロッド
2の周囲の透明ガラス層4との境界付近に気泡5の残存
が認められた。これに対し、図6の(a)に示すように
本発明の方法により、図5の比較例よりも110mm上
方に外付けスス体1をセットし、上部非有効部の大半が
均熱範囲外になるようにして加熱処理し、図6の(b)
に示すように上部非有効部の大部分を不透明ガラス状態
部分6として残した実施例では、光ファイバ母材の有効
部に気泡の残存は認められなかった。なお、この実施例
ではOVD法による外付けスス体の製造をSiCl4
酸水素火炎で行った例を示したが、これをSiCl4
メタンガス(CH4 )とした場合でも同様の結果が得ら
れた。
(Example 2, Comparative Example 2) As the glass rod for core, a quartz glass rod having the same structure as that used in Example 1 was used, and the effective portion length was 550.
mm and diameter 25 mm, and pure silica glass rods for ineffective portions were connected to both ends thereof. O around this rod
Sooting was performed by the VD method. To produce soot glass particles, a hydrolysis method in which SiCl 4 is vaporized and introduced into an oxygen-hydrogen flame is used, and 10 reciprocating depositions are performed in the longitudinal direction to form an external soot body having an effective portion diameter of 120 mm. Obtained. The effective length is 550m, which is the same as the effective length of the rod.
m, and the length of the ineffective part is about 170 m for both upper and lower parts
It was m. This soot body attached to the outside was made into transparent glass by using a soaking furnace. 5 and 6 are schematic diagrams showing the heating method and the state of the obtained optical fiber preform in Examples and Comparative Examples. First, as a comparative example, as shown in FIG. 5A, an external soot body 1 having a soot layer 3 of glass fine particles formed around a glass rod 2 for a core is uniformly heated over the non-effective portion and the effective portion. The glass was set in a soaking furnace in a He atmosphere maintained at 1500 ° C. so as to be within the range, and kept for 90 minutes to be transparent vitrified. In the optical fiber preform obtained as a result, as shown in FIG. 5 (b), bubbles 5 were observed to remain near the boundary with the transparent glass layer 4 around the core glass rod 2. On the other hand, as shown in FIG. 6A, by the method of the present invention, the external soot body 1 is set 110 mm above the comparative example of FIG. 5, and most of the upper non-effective portion is outside the soaking range. Heat treatment as shown in FIG.
In the example in which most of the upper non-effective portion was left as the opaque glass state portion 6 as shown in (4), no bubbles remained in the effective portion of the optical fiber preform. In this embodiment, the production of the external soot body by the OVD method was performed using SiCl 4 +.
An example of using an oxyhydrogen flame was shown, but this was performed using SiCl 4 +
Similar results were obtained when using methane gas (CH 4 ).

【0015】上記実施例1及び2で得られた光ファイバ
母材をファイバ化したところ、光ファイバのガラス径は
125μm±1μmの範囲内で安定しており、また、こ
の光ファイバを1550nm帯のOTDRで分析したと
ころ伝送損失段差も極めて小さく、良好な品質の光ファ
イバが得られた。これに対し、比較例1及び2で得られ
た気泡が残存する光ファイバ母材をファイバ化したとこ
ろ、気泡に該当する部分で光ファイバのガラス径が局所
的に急変動し、125μm±1μmの範囲を超えてしま
い、良好な製品とするためにはこれを除去する必要があ
り、歩留りの低下を招く結果となった。また、これらの
気泡を含むファイバを1550nm帯のOTDRで分析
したところ、気泡に該当する部分で0.1dB程度の伝
送損失段差が見られた。
When the optical fiber preforms obtained in Examples 1 and 2 were made into a fiber, the glass diameter of the optical fiber was stable within the range of 125 μm ± 1 μm, and the optical fiber of 1550 nm band was used. When analyzed by OTDR, the transmission loss step was extremely small, and an optical fiber of good quality was obtained. On the other hand, when the optical fiber preform obtained in Comparative Examples 1 and 2 in which the bubbles remain was made into a fiber, the glass diameter of the optical fiber suddenly changed locally at the portion corresponding to the bubbles, and the glass diameter was 125 μm ± 1 μm. This exceeds the range, and it is necessary to remove this in order to obtain a good product, resulting in a decrease in yield. Further, when the fiber including these bubbles was analyzed by OTDR in the 1550 nm band, a transmission loss step of about 0.1 dB was observed in the portion corresponding to the bubbles.

【0016】[0016]

【発明の効果】本発明の方法によれば、コア用ガラスロ
ッドの周囲にOVD法やVAD法によりスス付けを行っ
た外付けスス体を過熱透明化して光ファイバ母材を製造
する方法において、コア用ガラスロッドの周囲に生じや
すい気泡の残存を抑制することができる。
According to the method of the present invention, a method for producing an optical fiber preform by heat-transparentizing an external soot body, which is sooted around the glass rod for core by the OVD method or the VAD method, It is possible to suppress the remaining of bubbles that are likely to occur around the core glass rod.

【図面の簡単な説明】[Brief description of drawings]

【図1】外付けスス体の構造を模式的に示す説明図。FIG. 1 is an explanatory view schematically showing the structure of an external soot body.

【図2】外付けスス体を従来の方法により加熱透明化し
て光ファイバ母材とする際に残存する気泡を模式的に示
す説明図。
FIG. 2 is an explanatory view schematically showing bubbles that remain when an external soot body is heated and made transparent by a conventional method to form an optical fiber preform.

【図3】本発明の方法において、非有効部に不透明ガラ
ス状態部分を残すパターンの例を模式的に示す説明図。
FIG. 3 is an explanatory view schematically showing an example of a pattern which leaves an opaque glass state portion in a non-effective portion in the method of the present invention.

【図4】実施例1、比較例1における加熱方式及び得ら
れた光ファイバ母材の状態を示す模式図。
FIG. 4 is a schematic diagram showing a heating method in Example 1 and Comparative Example 1 and a state of the obtained optical fiber preform.

【図5】比較例2における加熱方式及び得られた光ファ
イバ母材の状態を示す模式図。
FIG. 5 is a schematic diagram showing a heating method in Comparative Example 2 and a state of the obtained optical fiber preform.

【図6】実施例2における加熱方式及び得られた光ファ
イバ母材の状態を示す模式図。
FIG. 6 is a schematic diagram showing a heating method in Example 2 and a state of the obtained optical fiber preform.

【符号の説明】[Explanation of symbols]

1 外付けスス体(ガラス微粒子堆積体) 2 コア
用ガラスロッド 3 スス層(ガラス微粒子の堆積層) 4 透明ガラ
ス層 5 気泡 6 不透明ガラス状態部分
1 External soot body (glass particulate deposit body) 2 Glass rod for core 3 Soot layer (glass particulate deposit layer) 4 Transparent glass layer 5 Bubbles 6 Opaque glass state part

フロントページの続き (72)発明者 鬼頭 毅彦 神奈川県横浜市栄区田谷町1番地 住友 電気工業株式会社 横浜製作所内 (56)参考文献 特開 平5−58648(JP,A) 特開 昭61−86431(JP,A) (58)調査した分野(Int.Cl.7,DB名) C03B 37/00 - 37/16 C03B 20/00 Front page continuation (72) Inventor Takehiko Kitou 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (56) Reference JP-A-5-58648 (JP, A) JP-A-61-86431 (JP, A) (58) Fields surveyed (Int.Cl. 7 , DB name) C03B 37/00-37/16 C03B 20/00

Claims (6)

(57)【特許請求の範囲】(57) [Claims] 【請求項1】 コア用ガラスロッドの周囲に外付け法に
よりスス付けを行い、得られた外付けスス体を熱処理し
て透明ガラス化する光ファイバ用母材の製造方法におい
て、透明ガラス化の際に、光ファイバ用母材の両端の非
有効部のいずれか一方又は両方の少なくとも一部分を不
透明ガラス状態で残すことを特徴とする光ファイバ用母
材の製造方法。
1. A method for producing an optical fiber preform in which soot is attached to the periphery of a glass rod for a core by an external attachment method, and the obtained externally attached soot body is heat-treated to be transparent vitrified. At this time, at least a part of one or both of the ineffective portions at both ends of the optical fiber preform is left in an opaque glass state, and a method for producing an optical fiber preform.
【請求項2】 外付け法によるスス付けを、鉛直方向に
コア用ガラスロッドを配置し、縦方向にススを成長させ
るVAD法により行うことを特徴とする請求項1に記載
の光ファイバ用母材の製造方法。
2. The optical fiber mother board according to claim 1, wherein the soot attachment by the external attachment method is performed by a VAD method in which a glass rod for core is arranged in the vertical direction and the soot is grown in the vertical direction. Method of manufacturing wood.
【請求項3】 不透明ガラス状態部分を残す非有効部と
して、上方に位置するスス付け開始部分を選択すること
を特徴とする請求項2に記載の光ファイバ用母材の製造
方法。
3. The method for producing an optical fiber preform according to claim 2, wherein the sooting start portion located above is selected as the ineffective portion that leaves the opaque glass state portion.
【請求項4】 外付け法によるスス付けを、コア用ガラ
スロッドの周囲に、層状にスス付けを行うOVD法によ
り行うことを特徴とする請求項1に記載の光ファイバ用
母材の製造方法。
4. The method for producing an optical fiber preform according to claim 1, wherein the soot attachment by the external attachment method is performed by the OVD method in which the soot is layered around the glass rod for core. .
【請求項5】 外付けスス体の透明ガラス化をゾーン加
熱炉を用いて行い、前記外付けスス体の加熱終了位置を
調整することにより不透明ガラス状態部分を形成させる
ことを特徴とする請求項1〜4のいずれか1項に記載の
光ファイバ用母材の製造方法。
5. An opaque glass state portion is formed by performing transparent vitrification of an external soot body using a zone heating furnace and adjusting a heating end position of the external soot body. The method for manufacturing a preform for an optical fiber according to any one of 1 to 4.
【請求項6】 外付けスス体の透明ガラス化を均熱炉を
用いて行い、両端の非有効部のいずれか一方又は両方の
少なくとも一部分が、均熱範囲に入らないようにするこ
とにより、該非有効部に不透明ガラス状態部分を形成さ
せることを特徴とする請求項1〜4のいずれか1項に記
載の光ファイバ用母材の製造方法。
6. A soaking furnace is used for transparent vitrification of an external soot body so that at least a part of one or both of the ineffective portions at both ends does not fall within the soaking range. The method for producing an optical fiber preform according to any one of claims 1 to 4, wherein an opaque glass state portion is formed in the non-effective portion.
JP28424598A 1998-10-06 1998-10-06 Manufacturing method of preform for optical fiber Expired - Lifetime JP3498590B2 (en)

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