JP6597177B2 - Manufacturing method of optical fiber preform - Google Patents

Manufacturing method of optical fiber preform Download PDF

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JP6597177B2
JP6597177B2 JP2015209826A JP2015209826A JP6597177B2 JP 6597177 B2 JP6597177 B2 JP 6597177B2 JP 2015209826 A JP2015209826 A JP 2015209826A JP 2015209826 A JP2015209826 A JP 2015209826A JP 6597177 B2 JP6597177 B2 JP 6597177B2
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和昌 牧原
司明 根岸
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Sumitomo Electric Industries 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]
    • C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering

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Description

本発明は、光ファイバ用母材の製造方法、特に多孔質母材の焼結工程に関する。   The present invention relates to a method for manufacturing an optical fiber preform, and more particularly to a porous preform preform sintering process.

特許文献１は、光ファイバ母材の多孔質スート体のガラス化方法に関する発明であって、多孔質スート体の下端部のガラス化温度をＴ１、多孔質スート体の上端部のガラス化温度をＴ３、下端部と上端部との間の中間部のガラス化温度をＴ２としたとき、Ｔ１＞Ｔ２≧Ｔ３となるようにガラス化温度を制御することが開示されている。 Patent Document 1 is an invention relating to a vitrification method for a porous soot body of an optical fiber preform, wherein the vitrification temperature at the lower end portion of the porous soot body is T 1 , and the vitrification temperature at the upper end portion of the porous soot body. the T 3, when the vitrification temperature of the intermediate portion between the lower end and the upper portion was T 2, to control the glass transition temperature such that T 1> T 2 ≧ T 3 is disclosed .

特開２００３−８１６５７号公報JP 2003-81657 A

特許文献１に記載の方法においては、多孔質スート体の上端部のガラス化温度が低いために上端部の透明ガラス化が不十分となる。その結果、後工程での多孔質スート体の割れや気泡の原因となりやすい。特に、光ファイバのコア用の多孔質スート体はＧｅが添加されているため焼結により作製される焼結体に歪みが多く、割れが発生しやすい。また、コア用多孔質スート体の中心には柔らかいガラス微粒子が堆積されているため、気泡が残りやすい。そのため、コア用多孔質スート体を焼結する焼結工程において、上端部のガラス化温度が低いと割れの発生や気泡の残留が顕著である。   In the method described in Patent Document 1, since the vitrification temperature of the upper end portion of the porous soot body is low, the transparent vitrification of the upper end portion becomes insufficient. As a result, the porous soot body is likely to be cracked or bubbles in the subsequent process. In particular, since the porous soot body for the core of the optical fiber is doped with Ge, the sintered body produced by sintering has a lot of distortion and is likely to crack. Further, since soft glass fine particles are deposited at the center of the core soot body, bubbles are likely to remain. For this reason, in the sintering step of sintering the porous soot body for the core, if the vitrification temperature at the upper end is low, the occurrence of cracks and residual bubbles are remarkable.

本発明は、割れや気泡等の製品不良の発生を防止可能な光ファイバ用母材の製造方法を提供することを目的とする。   An object of this invention is to provide the manufacturing method of the preform | base_material for optical fibers which can prevent generation | occurrence | production of product defects, such as a crack and a bubble.

本発明の光ファイバ用母材の製造方法は、
多孔質母材を加熱炉の上下方向に順次移動させることにより透明ガラス化を行う光ファイバ用母材の製造方法であって、
前記多孔質母材の上端部の加熱温度が前記多孔質母材の中間部の加熱温度よりも高くなるように前記加熱炉の温度を調整する、または前記多孔質母材の前記上端部を加熱するときの前記多孔質母材の移動速度が前記中間部を加熱するときの前記多孔質母材の移動速度よりも遅くなるように前記多孔質母材の移動速度を調整する。 The manufacturing method of the optical fiber preform of the present invention is as follows:
A method for producing a preform for an optical fiber that performs transparent vitrification by sequentially moving a porous preform in the vertical direction of a heating furnace,
The temperature of the heating furnace is adjusted so that the heating temperature of the upper end portion of the porous base material is higher than the heating temperature of the intermediate portion of the porous base material, or the upper end portion of the porous base material is heated. The moving speed of the porous base material is adjusted so that the moving speed of the porous base material is slower than the moving speed of the porous base material when the intermediate portion is heated.

本発明によれば、割れや気泡等の製品不良の発生を防止可能な光ファイバ用母材の製造方法を提供することができる。   ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the optical fiber preform | base_material which can prevent generation | occurrence | production of product defects, such as a crack and a bubble, can be provided.

本発明の光ファイバ用母材の製造方法で用いられる脱水焼結装置の一例を示す概略構成図である。It is a schematic block diagram which shows an example of the dehydration sintering apparatus used with the manufacturing method of the preform | base_material for optical fibers of this invention. 図１に示す光ファイバ用母材の脱水焼結工程における加熱温度の条件と従来例に係る加熱温度の条件とを示すグラフである。It is a graph which shows the conditions of the heating temperature in the spin-drying | dehydration sintering process of the optical fiber preform | base_material shown in FIG. 1, and the conditions of the heating temperature concerning a prior art example.

＜本発明の実施形態の概要＞
最初に本発明の実施形態の概要を説明する。
本実施形態にかかる光ファイバ用母材の製造方法は、
（１）多孔質母材を加熱炉の上下方向に順次移動させることにより透明ガラス化を行う光ファイバ用母材の製造方法であって、
前記多孔質母材の上端部の加熱温度が前記多孔質母材の中間部の加熱温度よりも高くなるように前記加熱炉の温度を調整する、または前記多孔質母材の前記上端部を加熱するときの前記多孔質母材の移動速度が前記中間部を加熱するときの前記多孔質母材の移動速度よりも遅くなるように前記多孔質母材の移動速度を調整する。
この構成によれば、多孔質母材の加熱温度や移動速度を制御することで、特に多孔質母材の上端部における割れや気泡等の発生を防止することができる。 <Outline of Embodiment of the Present Invention>
First, an outline of an embodiment of the present invention will be described.
The manufacturing method of the optical fiber preform according to the present embodiment is as follows.
(1) A method for producing an optical fiber preform, in which transparent vitrification is performed by sequentially moving a porous preform in the vertical direction of a heating furnace,
The temperature of the heating furnace is adjusted so that the heating temperature of the upper end portion of the porous base material is higher than the heating temperature of the intermediate portion of the porous base material, or the upper end portion of the porous base material is heated. The moving speed of the porous base material is adjusted so that the moving speed of the porous base material is slower than the moving speed of the porous base material when the intermediate portion is heated.
According to this configuration, by controlling the heating temperature and the moving speed of the porous base material, it is possible to prevent the occurrence of cracks, bubbles and the like particularly at the upper end portion of the porous base material.

（２）前記加熱炉の前記温度を調整する場合には、前記多孔質母材の下端部の加熱温度が前記中間部の加熱温度よりも高くなるように前記加熱炉の前記温度を調整することが好ましい。
この構成によれば、多孔質母材の下端部における割れや気泡等の発生も防止することができる。 (2) When adjusting the temperature of the heating furnace, the temperature of the heating furnace is adjusted so that the heating temperature of the lower end portion of the porous base material is higher than the heating temperature of the intermediate portion. Is preferred.
According to this structure, generation | occurrence | production of the crack in the lower end part of a porous preform | base_material, a bubble, etc. can also be prevented.

（３）前記多孔質母材の前記上端部および前記下端部の加熱温度と、前記中間部の加熱温度との差が５℃以上１００℃以下であることが好ましい。
多孔質母材の両端部の加熱温度と中間部の加熱温度との差を上記範囲とすることで、多孔質母材の伸びや内部気泡の残留を防止しつつ、適切に透明ガラス化を行うことができる。 (3) It is preferable that the difference of the heating temperature of the said upper end part and the said lower end part of the said porous preform | base_material and the heating temperature of the said intermediate part is 5 to 100 degreeC.
By making the difference between the heating temperature at both ends of the porous base material and the heating temperature at the intermediate part within the above range, the glass is appropriately transparent vitrified while preventing the extension of the porous base material and the remaining of internal bubbles. be able to.

（４）前記加熱炉の前記移動速度を調整する場合には、前記多孔質母材の下端部を加熱するときの前記多孔質母材の移動速度が前記中間部を加熱するときの前記多孔質母材の移動速度よりも遅くなるように前記移動速度を調整することが好ましい。
この構成によれば、多孔質母材の下端部における割れや気泡等の発生も防止することができる。 (4) When adjusting the moving speed of the heating furnace, the porous speed when the moving speed of the porous base material when the lower end portion of the porous base material is heated heats the intermediate part. It is preferable to adjust the moving speed so as to be slower than the moving speed of the base material.
According to this structure, generation | occurrence | production of the crack in the lower end part of a porous preform | base_material, a bubble, etc. can also be prevented.

＜本発明の実施形態の詳細＞
以下、本発明に係る光ファイバ用母材の製造方法の実施の形態の例を、図面を参照して説明する。 <Details of Embodiment of the Present Invention>
Hereinafter, an example of an embodiment of a method for manufacturing an optical fiber preform according to the present invention will be described with reference to the drawings.

図１に示すように、本実施形態の光ファイバ用母材の製造方法を実施する加熱炉１０は、炉心管１１の中間部外周側にヒータ１２を備えている。この加熱炉１０は、ガラス微粒子堆積体１の脱水工程および焼結（透明ガラス化）工程に用いられ、ガラス微粒子堆積体１に与える単位時間当たりの熱量を制御することができる。   As shown in FIG. 1, a heating furnace 10 that implements the optical fiber preform manufacturing method of the present embodiment includes a heater 12 on the outer peripheral side of an intermediate portion of a furnace core tube 11. The heating furnace 10 is used for a dehydration process and a sintering (transparent vitrification) process of the glass fine particle deposit 1, and can control the amount of heat per unit time given to the glass fine particle deposit 1.

炉心管１１内には、火炎加水分解反応によりガラス微粒子を出発ガラスロッド２に堆積させた多孔質体であるガラス微粒子堆積体１（多孔質母材の一例）が吊り下げられている。本実施形態におけるガラス微粒子堆積体１は、例えば光ファイバのコア部分のガラスロッドとなる部分であり、屈折率を高めるためのドーパントとしてＧｅが添加されている。ガラス微粒子堆積体１は、その上端部が支持棒１３を介して昇降機構１４に固定されている。支持棒１３は、制御装置１５によって制御される昇降機構１４により上下方向（ガラス微粒子堆積体１の長手方向）に移動可能である。昇降機構１４は、脱水時および焼結時に、ガラス微粒子堆積体１をあらかじめ設定された下降速度でヒータ１２のヒートゾーンに対して上方から下方へ向けて移動させる。昇降装置１４によるガラス微粒子堆積体１の上下方向への移動はガラス微粒子堆積体１の全長にわたってほぼ一定の速度で行われる。   A glass particulate deposit 1 (an example of a porous base material), which is a porous body in which glass particulates are deposited on the starting glass rod 2 by a flame hydrolysis reaction, is suspended in the furnace core tube 11. The glass particulate deposit 1 in the present embodiment is, for example, a portion that becomes a glass rod of a core portion of an optical fiber, and Ge is added as a dopant for increasing the refractive index. The upper end of the glass particulate deposit 1 is fixed to the elevating mechanism 14 via a support bar 13. The support bar 13 can be moved in the vertical direction (longitudinal direction of the glass particle deposit 1) by the lifting mechanism 14 controlled by the control device 15. The elevating mechanism 14 moves the glass particulate deposit 1 from the upper side to the lower side with respect to the heat zone of the heater 12 at a preset lowering speed during dehydration and sintering. The vertical movement of the glass particulate deposit 1 by the elevating device 14 is performed at a substantially constant speed over the entire length of the glass particulate deposit 1.

炉心管１１の下部には、処理ガス供給管１６が設けられている。この処理ガス供給管１６から炉心管１１内に、脱水時および焼結時に処理ガスが不図示のガス供給制御装置によって供給される。また、炉心管１１の上部には、不図示の排ガス処理装置に接続された処理ガス排気管１７が設けられている。この処理ガス排気管１７から炉心管１１の外に、処理ガスや脱水時や焼結時にガラス微粒子堆積体１から放出された水分等が排出される。   A processing gas supply pipe 16 is provided at the lower part of the core tube 11. A processing gas is supplied from the processing gas supply pipe 16 into the core tube 11 at the time of dehydration and sintering by a gas supply control device (not shown). Further, a processing gas exhaust pipe 17 connected to an exhaust gas processing apparatus (not shown) is provided on the upper portion of the core tube 11. From the processing gas exhaust pipe 17, the processing gas, moisture released from the glass particulate deposit 1 during dehydration and sintering, and the like are discharged out of the furnace core tube 11.

本実施形態の光ファイバ用母材の製造方法では、図２の例１（実施例）のグラフに示されるように、脱水工程の後工程である焼結（透明ガラス化）工程が行われる際に、ガラス微粒子堆積体１の上端部１Ａ（図１参照）および下端部１Ｂの加熱温度（すなわち、ヒータ１２の設定温度）Ｔ１がガラス微粒子堆積体１の中間部１Ｃの加熱温度Ｔ２よりも高くなるように、加熱炉１０の温度を調整している。ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂの加熱温度Ｔ１は、例えば１４００℃〜１６００℃、中間部１Ｃの加熱温度Ｔ２は例えば１３５０℃〜１５５０℃となるように調整される。ここで、ガラス微粒子堆積体１の上端部１Ａとは上側のテーパ部分を示し、下端部１Ｂとは下側のテーパ部分を示し、中間部１Ｃとは上端部１Ａと下端部１Ｂとの間の外径が一定な外径定常部を示す。   In the optical fiber preform manufacturing method of the present embodiment, as shown in the graph of Example 1 (Example) in FIG. 2, a sintering (transparent vitrification) step, which is a subsequent step of the dehydration step, is performed. Further, the heating temperature T1 of the upper end portion 1A (see FIG. 1) and the lower end portion 1B of the glass fine particle deposit 1 (that is, the set temperature of the heater 12) T1 is higher than the heating temperature T2 of the intermediate portion 1C of the glass fine particle deposit 1. Thus, the temperature of the heating furnace 10 is adjusted. The heating temperature T1 of the upper end portion 1A and the lower end portion 1B of the glass fine particle deposit 1 is adjusted to be, for example, 1400 ° C. to 1600 ° C., and the heating temperature T2 of the intermediate portion 1C is, for example, 1350 ° C. to 1550 ° C. Here, the upper end portion 1A of the glass particulate deposit 1 indicates an upper tapered portion, the lower end portion 1B indicates a lower tapered portion, and the intermediate portion 1C is between the upper end portion 1A and the lower end portion 1B. An outer diameter steady portion having a constant outer diameter is shown.

なお、焼結時の加熱炉１０の温度の調整に関しては、ガラス微粒子堆積体１の両端部（上端部１Ａおよび下端部１Ｂ）の加熱温度Ｔ１と、ガラス微粒子堆積体１の中間部１Ｃの加熱温度Ｔ２との差が５℃以上１００℃以下であることが好ましい。さらに好ましくは、加熱温度Ｔ１と加熱温度Ｔ２との差は２０℃程度である。両端部１Ａ，１Ｂの加熱温度Ｔ１と、中間部１Ｃの加熱温度Ｔ２との差が５℃以下であると、両端部１Ａ，１Ｂが十分に焼結できないか、あるいは中間部１Ｃに熱がかかり過ぎてしまう。また、両端部１Ａ，１Ｂの加熱温度Ｔ１と、中間部１Ｃの加熱温度Ｔ２との差が１００℃以上であると、逆に、両端部１Ａ，１Ｂに熱がかかり過ぎてしまうか、中間部１Ｃが十分に焼結できない。   In addition, regarding adjustment of the temperature of the heating furnace 10 at the time of sintering, the heating temperature T1 of the both ends (upper end 1A and lower end 1B) of the glass fine particle deposit 1 and the heating of the intermediate portion 1C of the glass fine particle deposit 1 are performed. The difference from the temperature T2 is preferably 5 ° C. or more and 100 ° C. or less. More preferably, the difference between the heating temperature T1 and the heating temperature T2 is about 20 ° C. If the difference between the heating temperature T1 of the both end portions 1A and 1B and the heating temperature T2 of the intermediate portion 1C is 5 ° C. or less, the both end portions 1A and 1B cannot be sufficiently sintered, or the intermediate portion 1C is heated. It will pass. On the other hand, if the difference between the heating temperature T1 of the both end portions 1A and 1B and the heating temperature T2 of the intermediate portion 1C is 100 ° C. or more, the two end portions 1A and 1B are excessively heated or the intermediate portion 1C cannot be sintered sufficiently.

次に、ガラス微粒子堆積体１の脱水方法および焼結方法について説明する。
まず、炉心管１１内部の温度を所定温度に保持した状態で、図１に示すように、ガラス微粒子堆積体１を炉心管１１内に挿入し、炉心管１１内の所定位置にガラス微粒子堆積体１がセットされるように吊り下げる。 Next, a dehydration method and a sintering method of the glass fine particle deposit 1 will be described.
First, in a state where the temperature inside the core tube 11 is maintained at a predetermined temperature, as shown in FIG. 1, the glass particle deposit 1 is inserted into the core tube 11, and the glass particle deposit is placed at a predetermined position in the core tube 11. Suspend so that 1 is set.

次に、ヒータ１２のヒートゾーンの設定温度を約１３００℃に上げ、ガラス微粒子堆積体１をあらかじめ設定された下降速度でヒータ１２のヒートゾーンに対して上方から下方へ向けて移動させつつ、ガラス微粒子堆積体１の全長にわたって加熱することで脱水処理が行われる。   Next, the set temperature of the heat zone of the heater 12 is raised to about 1300 ° C., and the glass particulate deposit 1 is moved from the upper side to the lower side with respect to the heat zone of the heater 12 at a preset lowering speed. The dehydration process is performed by heating the entire length of the particulate deposit 1.

次に、ヒータ１２のヒートゾーンの設定温度を温度Ｔ１、例えば１４００℃〜１６００℃に上げるとともに、ガラス微粒子堆積体１の下端部１Ｂがヒータ１２の上端付近の高さになるように位置合わせをし、ガラス微粒子堆積体１を昇降機構１４により所定の設定速度で下降させる。そして、ガラス微粒子堆積体１の中間部１Ｃがヒートゾーンに到達するまでガラス微粒子堆積体１を下方向に移動させながら、ヒートゾーンの設定温度を温度Ｔ１よりも低い温度Ｔ２、例えば１３５０℃〜１５５０℃に下げる。その後、ガラス微粒子堆積体１をさらに下方向に移動させながらガラス微粒子堆積体１の外径定常部（中間部１Ｃ）を設定温度Ｔ２のまま加熱する。そして、ガラス微粒子堆積体１の上端部１Ａがヒートゾーンに到達したら、ガラス微粒子堆積体１を下方向に移動させながらヒートゾーンの設定温度を再び温度Ｔ１へ上げる。ガラス微粒子堆積体１が炉心管１１内の最下部（終了位置）に到達したら、焼結工程（透明ガラス化工程）を終了する。   Next, the set temperature of the heat zone of the heater 12 is raised to a temperature T1, for example, 1400 ° C. to 1600 ° C., and alignment is performed so that the lower end portion 1B of the glass particulate deposit 1 is at a height near the upper end of the heater 12. Then, the glass particulate deposit 1 is lowered by the elevating mechanism 14 at a predetermined set speed. Then, while the glass particulate deposit body 1 is moved downward until the intermediate portion 1C of the glass particulate deposit body 1 reaches the heat zone, the set temperature of the heat zone is set to a temperature T2 lower than the temperature T1, for example, 1350 ° C to 1550 ° C. Reduce to ℃. Then, the outer diameter steady portion (intermediate portion 1C) of the glass fine particle deposit 1 is heated with the set temperature T2 while moving the glass fine particle deposit 1 further downward. When the upper end portion 1A of the glass fine particle deposit 1 reaches the heat zone, the set temperature of the heat zone is raised again to the temperature T1 while moving the glass fine particle deposit 1 downward. When the glass particulate deposit 1 reaches the lowermost part (end position) in the furnace core tube 11, the sintering process (transparent vitrification process) is finished.

以上のように、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂの加熱温度Ｔ１がガラス微粒子堆積体１の中間部１Ｃの加熱温度Ｔ２よりも高くなるように加熱炉１０の温度を調整しながら、ガラス微粒子堆積体１をその下端部１Ｂから上端部１Ａにかけて順次ヒータ１２によるヒートゾーンを通過させることで焼結する。これにより、ガラス微粒子堆積体１は、その長手方向に沿って下端部１Ｂから上端部１Ａにかけて順次加熱され、透明ガラス化された光ファイバ用母材（コア用ガラス母材）が作製される。   As described above, the temperature of the heating furnace 10 is adjusted so that the heating temperature T1 of the upper end portion 1A and the lower end portion 1B of the glass fine particle deposit 1 is higher than the heating temperature T2 of the intermediate portion 1C of the glass fine particle deposit 1. However, the glass fine particle deposit 1 is sintered by sequentially passing through the heat zone of the heater 12 from the lower end 1B to the upper end 1A. As a result, the glass fine particle deposit 1 is sequentially heated from the lower end 1B to the upper end 1A along the longitudinal direction thereof to produce a transparent glass-made optical fiber preform (core glass preform).

ところで、従来は、図２の例２（従来例）に示されるように、ガラス微粒子堆積体の全長にわたってヒータのヒートゾーンの設定温度が一定の温度（例えば、約１５００℃）に維持されたまま、ガラス微粒子堆積体を上下方向に移動させつつ透明ガラス化処理が行われていた。この場合、ガラス微粒子堆積体の中間部よりも開放端である上端部および下端部は放熱されやすいため、両端部を十分に加熱することができない。そのため、ガラス微粒子堆積体の両端が未焼結となり十分に透明ガラス化できず、後工程での割れや気泡の原因となってしまう。また、ガラス微粒子堆積体の両端部を十分に透明ガラス化するためにヒートゾーンの設定温度を上げると、ガラス微粒子堆積体の中間部に熱がかかり過ぎて、伸び等の変形が生じてしまったり、またはガラス微粒子堆積体が速く収縮しすぎてガスが閉じ込められて気泡が残留したりしてしまう。特に、コア用のガラス微粒子堆積体はドーパントとしてＧｅが添加されているため歪みが多く割れが発生しやすく、また嵩密度が低いため気泡が残りやすい。   By the way, conventionally, as shown in Example 2 (conventional example) of FIG. 2, the set temperature of the heater heat zone is maintained at a constant temperature (for example, about 1500 ° C.) over the entire length of the glass particulate deposit. The transparent vitrification process was performed while moving the glass particulate deposit in the vertical direction. In this case, the upper end portion and the lower end portion, which are open ends, are more easily radiated than the intermediate portion of the glass fine particle deposit, so that both end portions cannot be heated sufficiently. For this reason, both ends of the glass fine particle deposit are unsintered and cannot be sufficiently transparent vitrified, causing cracks and bubbles in the subsequent process. Also, if the temperature of the heat zone is increased to make both ends of the glass particulate deposit sufficiently transparent, the heat will be applied to the middle portion of the glass particulate deposit and deformation such as elongation may occur. Or, the glass particulate deposits contract too quickly and the gas is trapped, leaving bubbles. In particular, the glass fine particle deposit for the core contains Ge as a dopant, so that it is distorted and easily cracked, and bubbles are likely to remain because the bulk density is low.

これに対して、本実施形態によれば、透明ガラス化工程において、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂの加熱温度Ｔ１がガラス微粒子堆積体１の中間部１Ｃの加熱温度Ｔ２よりも高くなるように加熱炉１０の温度を調整している。これにより、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂについては十分に焼結できるような高い温度で加熱しつつ、ガラス微粒子堆積体１の中間部１Ｃには熱がかかり過ぎないように両端部１Ａ，１Ｂよりも低い温度で加熱する構成としているため、ガラス微粒子堆積体１の割れや気泡等の発生を防止することができる。なお、本実施形態のガラス微粒子堆積体１はコア用多孔質体であるため、焼結時に中間部１Ｃの加熱温度Ｔ２よりも両端部１Ａ，１Ｂの加熱温度Ｔ１を高くすることで割れの発生や気泡の残留を防止することが特に好ましい。   On the other hand, according to this embodiment, in the transparent vitrification step, the heating temperature T1 of the upper end portion 1A and the lower end portion 1B of the glass fine particle deposit 1 is higher than the heating temperature T2 of the intermediate portion 1C of the glass fine particle deposit 1. The temperature of the heating furnace 10 is adjusted so as to be higher. As a result, the upper end portion 1A and the lower end portion 1B of the glass fine particle deposit 1 are heated at a high temperature that can be sufficiently sintered, and the intermediate portion 1C of the glass fine particle deposit 1 is not excessively heated. Since it is set as the structure heated at temperature lower than both ends 1A and 1B, generation | occurrence | production of the crack, bubble, etc. of the glass fine particle deposit 1 can be prevented. Since the glass fine particle deposit 1 of the present embodiment is a porous body for cores, cracks are generated by increasing the heating temperature T1 of both end portions 1A and 1B higher than the heating temperature T2 of the intermediate portion 1C during sintering. It is particularly preferable to prevent residual bubbles.

さらに、本実施形態においては、ガラス微粒子堆積体１の下端部１Ｂがヒートゾーンに到達するときのヒータ１２の設定温度Ｔ１を高くしているため、中間部１Ｃを加熱する際のヒータ１２の設定温度Ｔ２を従来よりも低くしても、炉心管１１内の温度をある程度高温に維持しつつ中間部１Ｃを十分に加熱することができる。そのため、従来と比べて加熱温度を下げた時間を長くすることができ、ガラス微粒子堆積体１の焼結処理時の消費電力を低減させることができる。   Furthermore, in this embodiment, since the set temperature T1 of the heater 12 when the lower end portion 1B of the glass particulate deposit 1 reaches the heat zone is increased, the setting of the heater 12 when heating the intermediate portion 1C is performed. Even if the temperature T2 is lower than the conventional temperature, the intermediate portion 1C can be sufficiently heated while maintaining the temperature in the core tube 11 at a high temperature to some extent. Therefore, it is possible to lengthen the time during which the heating temperature is lowered as compared with the conventional case, and it is possible to reduce the power consumption during the sintering process of the glass fine particle deposit 1.

また、本実施形態においては、ガラス微粒子堆積体１の両端部１Ａ，１Ｂの加熱温度Ｔ１と、中間部１Ｃの加熱温度Ｔ２との差が５℃以上１００℃以下であることが好ましい。このように、ガラス微粒子堆積体１の両端部１Ａ，１Ｂの加熱温度Ｔ１と中間部１Ｃの加熱温度Ｔ２との差を上記範囲とすることで、ガラス微粒子堆積体１の伸びや内部気泡の残留を防止しつつ、適切に透明ガラス化を行うことができる。   Moreover, in this embodiment, it is preferable that the difference between the heating temperature T1 of the both end portions 1A and 1B of the glass fine particle deposit 1 and the heating temperature T2 of the intermediate portion 1C is 5 ° C. or more and 100 ° C. or less. As described above, by setting the difference between the heating temperature T1 of the both end portions 1A and 1B of the glass fine particle deposit 1 and the heating temperature T2 of the intermediate portion 1C in the above range, the elongation of the glass fine particle deposit 1 and the remaining of internal bubbles remain. Thus, transparent vitrification can be appropriately performed.

次に、本実施形態に係る光ファイバ用母材の製造方法の一実施例を説明する。   Next, an example of the manufacturing method of the optical fiber preform according to the present embodiment will be described.

（実施例）
ガラス微粒子堆積体を加熱炉の炉心管内に吊り下げて、昇降装置によりガラス微粒子堆積体を下降させた。図２の例１に示すように、ガラス微粒子堆積体の下端部がヒートゾーンに到達する際にはヒータによるヒートゾーンの設定温度を１５２０℃とし、一定時間経過した後にガラス微粒子堆積体の下側テーパ部分（下端部）に対応する長さを下方向に移動させながらヒートゾーンの設定温度を１４８０℃まで下げた。その後、ガラス微粒子堆積体をさらに下降させながらガラス微粒子堆積体の外径定常部（中間部）全体をヒートゾーンの設定温度１４８０℃のまま加熱した。その後、ガラス微粒子堆積体の上側テーパ部分（上端部）に到達したら上側テーパ部分に対応する長さを下方向に移動させながらヒートゾーンの設定温度を１５２０℃まで上げて一定時間経過した後にガラス微粒子堆積体の焼結を終了した。
その結果、ガラス微粒子堆積体の上端部側における未焼結部分は、上側テーパ部分の長さの１／３程度にまで抑えることができ、外径定常部に気泡がない透明な光ファイバ用母材を得ることができた。また、ガラス微粒子堆積体の下端部（下側テーパ部分）においては未焼結となる部分はなかった。 (Example)
The glass fine particle deposit was suspended in the furnace tube of the heating furnace, and the glass fine particle deposit was lowered by the lifting device. As shown in Example 1 of FIG. 2, when the lower end of the glass particulate deposit reaches the heat zone, the set temperature of the heat zone by the heater is set to 1520 ° C. The set temperature of the heat zone was lowered to 1480 ° C. while moving the length corresponding to the taper portion (lower end) downward. Then, the whole glass particle deposit body was further lowered, and the entire outer diameter steady portion (intermediate portion) of the glass particle deposit body was heated at the set temperature of 1480 ° C. in the heat zone. Thereafter, when the upper taper portion (upper end portion) of the glass fine particle deposit is reached, the temperature corresponding to the upper taper portion is moved downward, the set temperature of the heat zone is increased to 1520 ° C., and after a certain time has elapsed, the glass fine particles are passed. Sintering of the deposit was finished.
As a result, the unsintered portion on the upper end portion side of the glass particulate deposit can be suppressed to about 1/3 of the length of the upper tapered portion, and the transparent optical fiber mother body having no bubbles in the outer diameter steady portion. The material could be obtained. Further, there was no unsintered portion at the lower end portion (lower tapered portion) of the glass particulate deposit.

（比較例）
図２の例２に示すように、ヒートゾーンの設定温度をガラス微粒子堆積体の全長にわたって１５００℃に維持したままで、ガラス微粒子堆積体を上方から下方へ向かって移動させてヒートゾーンを通過させ焼結を行った。
その結果、ガラス微粒子堆積体の上側テーパ部分のほぼ全体が未焼結となった。また、ガラス微粒子堆積体の下側テーパ部分も未焼結となり、外径定常部には直径５ｍｍ程度の気泡が１０個発生した。 (Comparative example)
As shown in Example 2 of FIG. 2, the glass particulate deposit is moved from above to below while passing through the heat zone while maintaining the set temperature of the heat zone at 1500 ° C. over the entire length of the glass particulate deposit. Sintering was performed.
As a result, almost the entire upper tapered portion of the glass fine particle deposit was not sintered. Further, the lower tapered portion of the glass fine particle deposit was also unsintered, and 10 bubbles having a diameter of about 5 mm were generated in the outer diameter steady portion.

なお、実施例は、比較例に比べてガラス微粒子堆積体の中間部を加熱する際の加熱温度を低くしている、すなわち比較例に比べて加熱温度を下げた時間が長くすることができるため、消費電力を３％程度低減することができた。   In the examples, the heating temperature at the time of heating the intermediate part of the glass fine particle deposit is lower than that in the comparative example, that is, the heating time can be increased as compared with the comparative example. The power consumption was reduced by about 3%.

以上、本発明を詳細にまた特定の実施態様を参照して説明したが、本発明の精神と範囲を逸脱することなく様々な変更や修正を加えることができることは当業者にとって明らかである。また、上記説明した構成部材の数、位置、形状等は上記実施の形態に限定されず、本発明を実施する上で好適な数、位置、形状等に変更することができる。   While the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. In addition, the number, position, shape, and the like of the constituent members described above are not limited to the above-described embodiments, and can be changed to a number, position, shape, and the like that are suitable for carrying out the present invention.

なお、上記実施形態においては、昇降装置１４によるガラス微粒子堆積体１の上下方向への移動はガラス微粒子堆積体１の全長にわたってほぼ一定の速度で行われているが、この例に限られない。例えば、加熱炉１０の加熱温度（ヒータ１２の設定温度）はガラス微粒子堆積体１の全長にわたってほぼ一定としつつ、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂを加熱する（すなわち、上端部１Ａおよび下端部１Ｂがヒータ１２のヒートゾーンを通過する）ときのガラス微粒子堆積体１の移動速度が、ガラス微粒子堆積体１の中間部１Ｃを加熱する（すなわち、中間部１Ｃがヒータ１２のヒートゾーンを通過する）ときのガラス微粒子堆積体１の移動速度よりも遅くなるように、昇降装置１４によるガラス微粒子堆積体１の移動速度を調整する構成としても良い。これにより、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂに与えられる単位面積あたりの熱量を中間部１Ｃよりも多くすることができ、上記実施形態と同様の効果を得ることができる。   In the above embodiment, the vertical movement of the glass particulate deposit 1 by the lifting device 14 is performed at a substantially constant speed over the entire length of the glass particulate deposit 1, but is not limited to this example. For example, the heating temperature of the heating furnace 10 (set temperature of the heater 12) is substantially constant over the entire length of the glass particulate deposit 1, and the upper end 1A and the lower end 1B of the glass particulate deposit 1 are heated (that is, the upper end). The moving speed of the glass fine particle deposit 1 when the 1A and the lower end 1B pass through the heat zone of the heater 12 heats the intermediate portion 1C of the glass fine particle deposit 1 (that is, the intermediate portion 1C heats the heater 12). It is good also as a structure which adjusts the moving speed of the glass fine particle deposit 1 by the raising / lowering device 14 so that it may become slower than the moving speed of the glass fine particle deposit 1 at the time of passing through the zone. Thereby, the calorie | heat amount per unit area given to the upper end part 1A and the lower end part 1B of the glass fine particle deposition body 1 can be made larger than the intermediate part 1C, and the effect similar to the said embodiment can be acquired.

また、上記実施形態においては、ガラス微粒子堆積体１は、昇降機構１４によりヒータ１２のヒートゾーンに対して設定された下降速度で上方から下方へ向けて移動させる構成となっているが、ガラス微粒子堆積体１を設定された上昇速度で下方から上方へ向けて移動させてヒータ１２のヒートゾーンを通過させる構成としても良い。この場合も、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂの加熱温度Ｔ１を、中間部１Ｃの加熱温度Ｔ２よりも高くなるように制御することで上記の実施形態と同様の効果を得ることができる。   In the above embodiment, the glass particulate deposit 1 is configured to move from the upper side to the lower side by the elevating mechanism 14 at the lowering speed set with respect to the heat zone of the heater 12. It is good also as a structure which moves the deposit body 1 toward the upper direction from the downward direction at the set ascending speed, and passes the heat zone of the heater 12. FIG. Also in this case, the same effect as that of the above embodiment is obtained by controlling the heating temperature T1 of the upper end portion 1A and the lower end portion 1B of the glass fine particle deposit 1 to be higher than the heating temperature T2 of the intermediate portion 1C. be able to.

さらに、上記実施形態においては、ガラス微粒子堆積体１の上端部１Ａおよび下端部１Ｂの加熱温度Ｔ１を、中間部１Ｃの加熱温度Ｔ２よりも高くなるように制御しているが、下端部１Ｂおよび中間部１Ｃの加熱温度は一定としつつ、上端部１Ａの加熱温度を下端部１Ｂおよび中間部１Ｃの加熱温度よりも高くする構成としても良い。この構成によれば、ガラス微粒子堆積体１の上端部１Ａにおける割れや気泡の発生を防止することができるが、上記の実施形態のように上端部１Ａだけではなく下端部１Ｂにおいても加熱温度を上げる構成とすれば、ガラス微粒子堆積体１の全体にわたって割れの発生や気泡の残留を抑えることができるため、より好ましい。なお、加熱温度の調整する代わりにガラス微粒子堆積体１の移動速度を調整する構成の場合も、上端部１Ａを加熱するときのみガラス微粒子堆積体１の移動速度を遅くする構成とすることができるが、上記と同様に上端部１Ａだけではなく下端部１Ｂを加熱するときのガラス微粒子堆積体１の移動速度を遅くする構成とすることがより好ましい。   Further, in the above embodiment, the heating temperature T1 of the upper end portion 1A and the lower end portion 1B of the glass particulate deposit 1 is controlled to be higher than the heating temperature T2 of the intermediate portion 1C. The heating temperature of the upper portion 1A may be higher than the heating temperatures of the lower end portion 1B and the intermediate portion 1C while the heating temperature of the intermediate portion 1C is constant. According to this configuration, it is possible to prevent generation of cracks and bubbles in the upper end portion 1A of the glass particulate deposit 1, but the heating temperature is set not only in the upper end portion 1A but also in the lower end portion 1B as in the above embodiment. If it is set as the structure to raise, since the generation | occurrence | production of a crack and the residual of a bubble can be suppressed over the whole glass fine particle deposit body 1, it is more preferable. In addition, in the case of a configuration in which the moving speed of the glass particulate deposit 1 is adjusted instead of adjusting the heating temperature, the moving speed of the glass particulate deposit 1 can be slowed only when the upper end portion 1A is heated. However, as described above, it is more preferable that the moving speed of the glass particulate deposits 1 is slowed when heating not only the upper end 1A but also the lower end 1B.

また、上記実施形態においては、コア用多孔質体であるガラス微粒子堆積体１について両端部１Ａ，１Ｂの加熱温度Ｔ１を中間部１Ｃの加熱温度Ｔ２よりも高くする構成としているが、この例に限られない。例えば、コア部分のガラスロッドの外周にクラッド層となるガラス微粒子が堆積された光ファイバ用母材を焼結する際にも、上記実施の形態と同様に上端部および下端部の加熱温度を中間部の加熱温度よりも高くするか、上端部および下端部の移動速度を中間部の移動速度よりも遅くする制御を行うことで、コアおよびクラッド層を備えた光ファイバ用母材の割れの発生や気泡の残留を防止することができる。   Moreover, in the said embodiment, although it is set as the structure which makes heating temperature T1 of both ends 1A and 1B higher than heating temperature T2 of the intermediate part 1C about the glass fine particle deposit body 1 which is a porous body for cores, Not limited. For example, when sintering an optical fiber preform in which glass fine particles serving as a cladding layer are deposited on the outer periphery of the glass rod in the core portion, the heating temperatures of the upper end portion and the lower end portion are intermediated as in the above embodiment. Occurrence of cracks in the optical fiber preform with the core and cladding layers by controlling the temperature higher than the heating temperature of the part or lowering the moving speed of the upper end and lower end than the moving speed of the intermediate part And residual air bubbles can be prevented.

１：ガラス微粒子堆積体（多孔質母材の一例）
１Ａ：上端部
１Ｂ：下端部
１Ｃ：中間部
２：ガラスロッド
１０：加熱炉
１１：炉心管
１２：ヒータ
１３：支持棒
１４：昇降装置
１５：制御装置
１６：処理ガス供給管
１７：処理ガス排気管
Ｔ１：上端部および下端部の加熱温度
Ｔ２：中間部の加熱温度 1: Glass particulate deposit (an example of a porous matrix)
1A: Upper end portion 1B: Lower end portion 1C: Intermediate portion 2: Glass rod 10: Heating furnace 11: Reactor core tube 12: Heater 13: Support rod 14: Lifting device 15: Control device 16: Processing gas supply tube 17: Processing gas exhaust Tube T1: Heating temperature at the upper and lower ends T2: Heating temperature at the middle

Claims (3)

多孔質母材を加熱炉の上下方向に順次移動させることにより透明ガラス化処理を行う光ファイバ用母材の製造方法であって、
前記透明ガラス化処理において、前記多孔質母材の中間部の加熱温度は一定となるように前記加熱炉の温度を調整するとともに、前記多孔質母材の上端部の加熱温度が前記多孔質母材の前記中間部の加熱温度よりも高くなるように前記加熱炉の温度を調整する、光ファイバ用母材の製造方法。 A method for producing a preform for an optical fiber that performs a transparent vitrification process by sequentially moving a porous preform in the vertical direction of a heating furnace,
In the transparent vitrification treatment, the temperature of the heating furnace is adjusted so that the heating temperature of the intermediate portion of the porous base material is constant, and the heating temperature of the upper end portion of the porous base material is set to the porous base material. adjust the furnace temperature to be higher than the heating temperature of the intermediate portion of the timber, a manufacturing method for an optical fiber preform. 前記加熱炉の前記温度を調整する場合には、前記多孔質母材の下端部の加熱温度が前記中間部の加熱温度よりも高くなるように前記加熱炉の前記温度を調整する、請求項１に記載の光ファイバ用母材の製造方法。   2. When adjusting the temperature of the heating furnace, the temperature of the heating furnace is adjusted so that a heating temperature of a lower end portion of the porous base material is higher than a heating temperature of the intermediate portion. The manufacturing method of the preform | base_material for optical fibers as described in any one of. 前記多孔質母材の前記上端部および前記下端部の加熱温度と、前記中間部の加熱温度との差が５℃以上１００℃以下である、請求項２に記載の光ファイバ用母材の製造方法。   The optical fiber preform according to claim 2, wherein a difference between a heating temperature of the upper end portion and the lower end portion of the porous preform and a heating temperature of the intermediate portion is 5 ° C or more and 100 ° C or less. Method.
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