JP6447279B2

JP6447279B2 - Optical fiber manufacturing method

Info

Publication number: JP6447279B2
Application number: JP2015054827A
Authority: JP
Inventors: 拓志永島; 公明佐藤; 敬浩佐久間; 良二菱倉; 玲川井; 中西　哲也; 哲也中西; 佐々木　隆; 隆佐々木
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2015-03-18
Filing date: 2015-03-18
Publication date: 2019-01-09
Anticipated expiration: 2035-03-18
Also published as: JP2016175779A

Description

本発明は、光ファイバ製造方法に関するものである。 The present invention relates to an optical fiber manufacturing method.

共通クラッド中に複数のコアが軸方向に延在するマルチコア光ファイバ（以下「ＭＣＦ」という。）を製造する方法として、特許文献１〜３に記載された方法が知られている。この製造方法では、石英ガラス製の母材管の軸方向に形成された複数の空孔それぞれに石英ガラス製のコアロッドを挿入し、これら母材管とコアロッドとを一体化し線引してＭＣＦを製造する。母材管はＭＣＦの共通クラッドとなり、コアロッドはＭＣＦのコアおよび一部クラッドとなる。 As a method of manufacturing a multi-core optical fiber (hereinafter referred to as “MCF”) in which a plurality of cores extend in the axial direction in a common cladding, methods described in Patent Documents 1 to 3 are known. In this manufacturing method, a quartz glass core rod is inserted into each of a plurality of holes formed in the axial direction of the quartz glass base material tube, and the base material tube and the core rod are integrated and drawn to draw the MCF. To manufacture. The base material pipe serves as a common clad of MCF, and the core rod serves as the core and part of the MCF.

特開２００６−１６０５２８号公報JP 2006-160528 A 特開２０１０−１１１５５４号公報JP 2010-111554 A 特開２０１１−１６８４６４号公報JP 2011-168464 A

本発明は、母材管とコアロッドとを一体化する際に長手方向の両者の位置関係を固定した状態で母材管の空孔内を減圧してマルチコア光ファイバを製造することができる新たな光ファイバ製造方法を提供することを目的とする。 The present invention provides a new multi-core optical fiber capable of producing a multi-core optical fiber by depressurizing the inside of a hole in a base material tube in a state where the positional relationship between the longitudinal direction is fixed when the base material tube and the core rod are integrated. An object of the present invention is to provide an optical fiber manufacturing method.

本発明の光ファイバ製造方法は、石英ガラス製の母材管の軸方向に形成された複数の空孔それぞれに石英ガラス製のコアロッドを挿入する挿入工程と、前記挿入工程の前に、前記挿入工程以降の各工程において前記コアロッドが前記母材管から突出するのを防止するとともに前記空孔内を減圧する為の空孔窓を有する突出防止部を前記母材管の第１端側に形成する突出防止部形成工程と、前記挿入工程の後に、前記母材管の前記第１端に接続された支持管を介して前記母材管の前記空孔内を減圧する減圧工程と、前記減圧工程下で前記母材管の第２端側を加熱軟化させ前記母材管および前記コアロッドを一体化する一体化工程と、前記母材管および前記コアロッドを線引して光ファイバを製造する線引工程とを備える。 The optical fiber manufacturing method of the present invention includes an insertion step of inserting a core rod made of quartz glass into each of a plurality of holes formed in the axial direction of a base tube made of quartz glass, and the insertion before the insertion step. In each step after the step, the core rod is prevented from protruding from the base material pipe, and a protrusion preventing portion having a hole window for reducing the pressure in the hole is formed on the first end side of the base material pipe. A protrusion preventing part forming step, a pressure reducing step of reducing the pressure in the hole of the base material pipe via a support pipe connected to the first end of the base material tube, and the pressure reducing step An integration step of heating and softening the second end side of the base material tube to integrate the base material tube and the core rod, and a wire for drawing an optical fiber by drawing the base material tube and the core rod; A drawing step.

本発明によれば、母材管とコアロッドとを一体化する際に長手方向の両者の位置関係を固定した状態で母材管の空孔内を減圧してマルチコア光ファイバを製造することができる。 According to the present invention, when the base material tube and the core rod are integrated, a multi-core optical fiber can be manufactured by reducing the pressure in the hole of the base material tube in a state where the positional relationship between the two in the longitudinal direction is fixed. .

第１比較例の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of the 1st comparative example. 第１実施形態の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of a 1st embodiment. 第１実施形態の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of a 1st embodiment. 第２比較例の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of the 2nd comparative example. 第２比較例の光ファイバ製造方法の一部変形例を説明する図である。It is a figure explaining the partial modification of the optical fiber manufacturing method of the 2nd comparative example. 第２実施形態の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of 2nd Embodiment. 第２実施形態の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of 2nd Embodiment. 第３実施形態の光ファイバ製造方法を説明する図である。It is a figure explaining the optical fiber manufacturing method of 3rd Embodiment.

前記母材管の前記第２端側において前記空孔を封止する封止部を形成する封止部形成工程を備えるのが好適である。前記一体化工程は、前記線引工程の前に、前記コアロッドの全体を前記母材管と一体化するコラプス工程であってもよい。また、前記一体化工程は、前記線引工程の開始時に前記母材管の前記第２端側で前記コアロッドと前記母材管とを一体化する工程であり、前記減圧工程下で前記線引工程を行うこととしてもよい。 It is preferable to provide a sealing portion forming step of forming a sealing portion that seals the holes on the second end side of the base material pipe. The integration step may be a collapse step in which the entire core rod is integrated with the base material tube before the drawing step. The integration step is a step of integrating the core rod and the base material tube on the second end side of the base material pipe at the start of the drawing step, and the drawing is performed under the decompression step. It is good also as performing a process.

前記突出防止部は、前記母材管の前記空孔が前記第１端側で前記コアロッドが突出できない形状又は大きさである第１条件、前記母材管の前記空孔が前記支持管により一部塞がれることにより前記コアロッドが突出できない第２条件、および、前記母材管と前記支持管との間に設けられたプレートにより前記コアロッドが突出できない第３条件、のうち何れか一つ又はこれら二以上の組合せにより形成されるのが好適である。 The protrusion preventing portion has a first condition that the hole of the base material pipe has a shape or a size that the core rod cannot protrude on the first end side, and the hole of the base material pipe is connected by the support pipe. Either one of a second condition in which the core rod cannot protrude due to clogging, and a third condition in which the core rod cannot protrude due to a plate provided between the base material tube and the support tube, or It is preferable to form a combination of these two or more.

前記封止部は、前記母材管の前記第２端側において全ての前記空孔を封止する支持棒であってもよいし、前記母材管の前記第２端側において全ての前記空孔を封止するキャップであってもよい。前記キャップは、前記母材管の前記第２端側において前記空孔の一部または全部の開口を連通させた状態であるのが好適である。 The sealing portion may be a support rod that seals all of the holes on the second end side of the base material pipe, or all of the voids on the second end side of the base material pipe. It may be a cap that seals the hole. The cap is preferably in a state where a part or all of the holes are communicated with each other on the second end side of the base material pipe.

以下、添付図面を参照して、本発明を実施するための形態を詳細に説明する。なお、図面の説明において同一または同様の要素には同一の符号を付し、重複する説明を省略する。本発明は、これらの例示に限定されるものではなく、特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or similar elements are denoted by the same reference numerals, and redundant description is omitted. The present invention is not limited to these exemplifications, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

（第１比較例）
図１は、第１比較例の光ファイバ製造方法を説明する図である。第１比較例の光ファイバ製造方法は、ロッドインコラプス（rod in collapse、以下「ＲＩＣ法」という。）法を用いる。 (First comparative example)
FIG. 1 is a diagram for explaining an optical fiber manufacturing method of a first comparative example. The optical fiber manufacturing method of the first comparative example uses a rod in collapse (hereinafter referred to as “RIC method”) method.

母材管１０、コアロッド２１〜２３および支持管３１，３２を準備する（同図（ａ））。母材管１０は、石英ガラス製であり、軸方向に貫通して形成された複数の空孔を有する。母材管１０はＭＣＦの共通クラッドとなる。コアロッド２１〜２３は、石英ガラス製であり、ＭＣＦのコアおよび一部クラッドとなる。支持管３１，３２は、母材管１０の外径と同程度の外径を有し、母材管１０の空孔を塞がない程度の内径を有する。 The base material pipe | tube 10, the core rods 21-23, and the support pipes 31 and 32 are prepared (the figure (a)). The base material tube 10 is made of quartz glass and has a plurality of holes formed so as to penetrate in the axial direction. The base material tube 10 is a common cladding of MCF. The core rods 21 to 23 are made of quartz glass and serve as an MCF core and a partial cladding. The support tubes 31 and 32 have an outer diameter that is approximately the same as the outer diameter of the base material tube 10 and an inner diameter that does not block the air holes of the base material tube 10.

母材管１０の第１端１１に支持管３１を接続するとともに、母材管１０の第２端１２に支持管３２を接続して、母材管１０の各空孔の内壁面を気相エッチングし、母材管１０の各空孔内に浄化ガス（塩素や酸素）を流しながらバーナ４０で母材管１０を加熱することによる浄化処理によって空孔内を清浄にする（浄化工程、同図（ｂ））。 The support pipe 31 is connected to the first end 11 of the base material pipe 10 and the support pipe 32 is connected to the second end 12 of the base material pipe 10, so that the inner wall surface of each hole of the base material pipe 10 is gas-phased. Etching and purifying the interior of the pores by a purification treatment by heating the preform tube 10 with the burner 40 while flowing a purification gas (chlorine or oxygen) into each pore of the preform tube 10 (purification step, same (B).

母材管１０の複数の空孔それぞれにコアロッド２１〜２３を挿入する（挿入工程、同図（ｃ））。母材管１０の空孔にコアロッド２１〜２３が挿入された状態で、支持管３２の側から母材管１０の空孔内を減圧し、母材管１０を軸周りに回転させ、母材管１０の第１端１１側をバーナ４０で加熱し、支持管３１と支持管３２とを互いに引っ張ることで、母材管１０とコアロッド２１〜２３とを一体化する（減圧工程、一体化工程、同図（ｄ））。これにより、母材管１０の加熱部が延伸し、母材管１０とコアロッド２１〜２３とが一体化するための起点部分を形成する。 The core rods 21 to 23 are inserted into the plurality of holes of the base material pipe 10 (insertion step, FIG. 10C). In a state where the core rods 21 to 23 are inserted into the holes of the base material pipe 10, the inside of the holes of the base material pipe 10 is depressurized from the support pipe 32 side, and the base material pipe 10 is rotated around the axis to The first end 11 side of the tube 10 is heated by the burner 40, and the base tube 10 and the core rods 21 to 23 are integrated by pulling the support tube 31 and the support tube 32 together (decompression process, integration process). (D) of FIG. Thereby, the heating part of the base material pipe | tube 10 is extended | stretched, and the starting point part for the base material pipe | tube 10 and the core rods 21-23 to integrate is formed.

起点部分は、母材管１０の空孔を大気圧に対し減圧した状態で母材管１０をコラプスする上での封止部としても機能する。封止部が形成されることにより、以後は延伸をせずに、加熱および減圧状態化のみで母材管１０とコアロッド２１〜２３とを一体化することが可能となる。 The starting point portion also functions as a sealing portion for collapsing the base material pipe 10 in a state where the holes of the base material pipe 10 are depressurized with respect to the atmospheric pressure. By forming the sealing portion, it is possible to integrate the base material pipe 10 and the core rods 21 to 23 only by heating and reducing the pressure without extending thereafter.

この第１比較例では、挿入工程以降の工程において、母材管１０の回転の際の振動によりコアロッド２１〜２３が移動したり、加熱により軟化したコアロッド２１〜２３が延伸したりすることにより、母材管１０の空孔に挿入されていたコアロッド２１〜２３は母材管１０の空孔から突出する可能性がある。 In the first comparative example, in the steps after the insertion step, the core rods 21 to 23 are moved by vibration during the rotation of the base material tube 10, or the core rods 21 to 23 softened by heating are stretched. The core rods 21 to 23 inserted in the holes of the base material pipe 10 may protrude from the holes of the base material pipe 10.

（第１実施形態）
図２および図３は、第１実施形態の光ファイバ製造方法を説明する図である。図３は、母材管１０と支持管３１との接続部分を拡大して示す。第１実施形態の光ファイバ製造方法はＲＩＣ法を用いる。 (First embodiment)
2 and 3 are diagrams for explaining the optical fiber manufacturing method of the first embodiment. FIG. 3 shows an enlarged connection portion between the base material pipe 10 and the support pipe 31. The optical fiber manufacturing method of the first embodiment uses the RIC method.

母材管１０、コアロッド２１〜２３、支持管３１および支持棒３３を準備する（図２（ａ））。母材管１０は、石英ガラス製であり、軸方向に貫通して形成された複数の空孔を有する。母材管１０はＭＣＦの共通クラッドとなる。コアロッド２１〜２３は、石英ガラス製であり、ＭＣＦのコアおよび一部クラッドとなる。母材管１０の空孔は、第１端１１側でコアロッド２１〜２３が突出できない形状または大きさを有する突出防止部とされている（突出防止部形成工程、図３）。 The base material pipe | tube 10, the core rods 21-23, the support pipe 31, and the support bar 33 are prepared (FIG. 2 (a)). The base material tube 10 is made of quartz glass and has a plurality of holes formed so as to penetrate in the axial direction. The base material tube 10 is a common cladding of MCF. The core rods 21 to 23 are made of quartz glass and serve as an MCF core and a partial cladding. The hole of the base material pipe 10 is a protrusion preventing part having a shape or size that the core rods 21 to 23 cannot protrude on the first end 11 side (protrusion preventing part forming step, FIG. 3).

母材管１０の第１端１１に支持管３１を接続して、母材管１０の各空孔の内壁面を気相エッチングし、母材管１０の各空孔内に浄化ガス（塩素や酸素）を流しながらバーナで母材管１０を加熱することによる浄化処理によって空孔内を清浄にする（浄化工程）。 The support pipe 31 is connected to the first end 11 of the base material pipe 10, and the inner wall surface of each hole of the base material pipe 10 is vapor-phase etched, and the purified gas (chlorine or The pores are cleaned by a purification process by heating the base material tube 10 with a burner while flowing (oxygen) (purification process).

母材管１０の複数の空孔それぞれに第２端１２側からコアロッド２１〜２３を挿入する（挿入工程、図２（ｂ）、図３）。挿入されたコアロッド２１〜２３は、母材管１０の第１端１１側に形成された突出防止部に突き当てられる。 The core rods 21 to 23 are inserted into the plurality of holes of the base material pipe 10 from the second end 12 side (insertion step, FIGS. 2B and 3). The inserted core rods 21 to 23 are abutted against a protrusion preventing portion formed on the first end 11 side of the base material pipe 10.

母材管１０の第２端１２に支持棒３３を接続し、母材管１０の第２端１２側において空孔を封止して、第２端１２側でコアロッド２１〜２３の突出を防止する突出防止部とするとともに、母材管１０の空孔内を減圧する際の封止部とする（封止部形成工程、図２（ｃ））。 A support rod 33 is connected to the second end 12 of the base material pipe 10, and a hole is sealed on the second end 12 side of the base material pipe 10 to prevent the core rods 21 to 23 from protruding on the second end 12 side. It is set as the protrusion prevention part to perform, and it is set as the sealing part at the time of decompressing the inside of the void | hole of the base material pipe | tube 10 (sealing part formation process, FIG.2 (c)).

支持管３１の側から母材管１０の空孔内を減圧し、母材管１０を軸周りに回転させ、母材管１０の第２端１２側をバーナで加熱し、支持管３１と支持棒３３とを互いに引っ張ることで、母材管１０とコアロッド２１〜２３とを一体化する（減圧工程、一体化工程、図２（ｄ））。これにより、母材管１０の加熱部が延伸し、母材管１０とコアロッド２１〜２３とが一体化するための起点部分を形成する。その後、線引工程により、母材管１０およびコアロッド２１〜２３を線引してＭＣＦを製造する。 The inside of the hole of the base material tube 10 is depressurized from the support tube 31 side, the base material tube 10 is rotated around the axis, and the second end 12 side of the base material tube 10 is heated by a burner, and the support tube 31 and the support tube 31 are supported. By pulling the rod 33 to each other, the base material tube 10 and the core rods 21 to 23 are integrated (decompression step, integration step, FIG. 2D). Thereby, the heating part of the base material pipe | tube 10 is extended | stretched, and the starting point part for the base material pipe | tube 10 and the core rods 21-23 to integrate is formed. Then, MCF is manufactured by drawing the base material pipe 10 and the core rods 21 to 23 by a drawing process.

本実施形態では、母材管１０の第１端１１側に突出防止部を形成するとともに、母材管１０の第２端１２側に封止部を形成する。封止部形成工程前にコアロッド２１〜２３が母材管１０の空孔から突出しないようにする。封止部は、減圧のための補助だけでなく、突出防止部としての機能をも有する。 In the present embodiment, the protrusion preventing portion is formed on the first end 11 side of the base material tube 10, and the sealing portion is formed on the second end 12 side of the base material tube 10. The core rods 21 to 23 are prevented from protruding from the holes of the base material tube 10 before the sealing portion forming step. The sealing part has not only an auxiliary for pressure reduction but also a function as a protrusion preventing part.

コアロッド２１〜２３が突出しないように封止部（突出防止部）を形成できる場合は、支持棒３３に替えて第１比較例と同様に支持管３２を用いてもよい。支持管３２の内径を小さくして肉厚にし、この支持管３２により母材管１０の空孔の一部または全部を塞ぐようにしてもよい。また、母材管１０の中心に空孔がある場合は、支持管３２の内部に何等かの突出防止部を設けてもよい。 When the sealing portion (protrusion prevention portion) can be formed so that the core rods 21 to 23 do not protrude, the support tube 32 may be used instead of the support rod 33 as in the first comparative example. The inner diameter of the support tube 32 may be reduced to increase the thickness, and the support tube 32 may block part or all of the holes of the base material tube 10. Further, when there is a hole in the center of the base material pipe 10, any protrusion preventing part may be provided inside the support pipe 32.

第１比較例のように、母材管１０の空孔の径が長手方向に一定であると、そのままでは母材管１０の空孔からコアロッド２１〜２３が突出することを防止することはできない。そこで、母材管１０と支持管３１とを互いに接続する際に母材管１０の第１端１１側において空孔の形状または大きさを限定することで、コアロッド２１〜２３の突出を防止するようにしてもよい。この場合、母材管１０の中心にある空孔は限定することができないので、何らかの手段で空孔の径を調節する。例えば、空孔にコアロッドを挿入した後に、空孔に開口を狭くする栓をすることで調整可能である。 If the diameter of the hole of the base material pipe 10 is constant in the longitudinal direction as in the first comparative example, the core rods 21 to 23 cannot be prevented from protruding from the hole of the base material pipe 10 as it is. . Therefore, when the base material pipe 10 and the support pipe 31 are connected to each other, the shape or size of the holes is limited on the first end 11 side of the base material pipe 10 to prevent the core rods 21 to 23 from protruding. You may do it. In this case, since the hole in the center of the base material pipe 10 cannot be limited, the diameter of the hole is adjusted by some means. For example, it can be adjusted by inserting a core rod into the hole and then plugging the hole to narrow the opening.

母材管１０の部分的に封止すべき空孔の端面と支持管３１との間に突出防止用のプレートを配し、これを突出防止部としてもよい。この場合、プレートは空孔窓を有し、その空孔窓は、コアロッド２１〜２３が挿入される各空孔の空間を小さくし、コアロッド２１〜２３が通過できない形状とする。プレートに空孔窓があることで、浄化工程や一体化工程の際に空孔の減圧処理に寄与する。支持管３１へのプレートの接続に際しては、断面がプレートと同じ形状のガラスロッドを用意し、このガラスロッドを支持管３１に加熱溶着し、ガラスロッドを所定の厚さを残して切断することで、プレートを形成することが可能となる。また、プレートの各空孔窓に対応して、各空孔窓から支持管３１の中心の空間に向かって連通する溝を支持管３１の端面に施しておけば、支持管３１を厚肉としても、各空孔内を減圧することが可能である。 A protrusion prevention plate may be provided between the end face of the hole to be partially sealed of the base material pipe 10 and the support pipe 31 and this may be used as a protrusion prevention portion. In this case, the plate has a hole window, and the hole window reduces the space of each hole into which the core rods 21 to 23 are inserted so that the core rods 21 to 23 cannot pass through. The presence of the hole window in the plate contributes to the hole pressure reduction process during the purification process and the integration process. When connecting the plate to the support tube 31, a glass rod having the same cross section as the plate is prepared, this glass rod is heated and welded to the support tube 31, and the glass rod is cut leaving a predetermined thickness. A plate can be formed. Further, if a groove communicating from each hole window toward the center space of the support tube 31 is formed on the end surface of the support tube 31 corresponding to each hole window of the plate, the support tube 31 is made thick. It is also possible to depressurize the inside of each hole.

（第２比較例）
図４は、第２比較例の光ファイバ製造方法を説明する図である。第２比較例の光ファイバ製造方法は、ロッドイン線引（rod in drawing、以下「ＲＩＤ法」という。）法を用いる。 (Second comparative example)
FIG. 4 is a diagram illustrating an optical fiber manufacturing method of the second comparative example. The optical fiber manufacturing method of the second comparative example uses a rod in drawing (hereinafter referred to as “RID method”) method.

母材管１０、コアロッド２１〜２３、支持管３１およびキャップ３４を準備する（同図（ａ））。母材管１０は、石英ガラス製であり、軸方向に貫通して形成された複数の空孔を有する。母材管１０はＭＣＦの共通クラッドとなる。コアロッド２１〜２３は、石英ガラス製であり、ＭＣＦのコアおよび一部クラッドとなる。支持管３１は、母材管１０の外径と同程度の外径を有し、母材管１０の空孔を塞がない程度の内径を有する。キャップ３４は、概略円錐形状を有し、底面が母材管１０の空孔を塞ぐことができる大きさを有する。 A base material pipe 10, core rods 21 to 23, a support pipe 31 and a cap 34 are prepared (FIG. 1A). The base material tube 10 is made of quartz glass and has a plurality of holes formed so as to penetrate in the axial direction. The base material tube 10 is a common cladding of MCF. The core rods 21 to 23 are made of quartz glass and serve as an MCF core and a partial cladding. The support tube 31 has an outer diameter that is approximately the same as the outer diameter of the base material tube 10, and has an inner diameter that does not block the air holes of the base material tube 10. The cap 34 has a substantially conical shape, and has a size such that the bottom surface can block the holes of the base material pipe 10.

母材管１０の第１端１１に支持管３１を接続するとともに、母材管１０の第２端１２にキャップ３４を接続する（封止部形成工程、同図（ｂ））。母材管１０の各空孔の内壁面を気相エッチングし、母材管１０の各空孔内に浄化ガス（塩素や酸素）を流しながら母材管１０を加熱することによる浄化処理によって空孔内を清浄にしてもよい（浄化工程）。 The support pipe 31 is connected to the first end 11 of the base material pipe 10, and the cap 34 is connected to the second end 12 of the base material pipe 10 (sealing part forming step, FIG. 5B). The inner wall surface of each hole of the base material pipe 10 is vapor-phase etched, and the base material pipe 10 is heated by purifying the base material pipe 10 while purifying gas (chlorine or oxygen) flowing through the holes. The inside of the hole may be cleaned (cleaning step).

母材管１０の複数の空孔それぞれに第１端１１側からコアロッド２１〜２３を挿入する（挿入工程、同図（ｃ））。母材管１０の第２端１２側が下になるように母材管１０，コアロッド２１〜２３，支持管３１およびキャップ３４を鉛直方向に配置して、支持管３１の側から母材管１０の空孔内を減圧しながら、キャップ３４および母材管１０の第２端１２側を加熱軟化し紡糸して、ＭＣＦを製造する（減圧工程、線引工程、同図（ｄ））。 The core rods 21 to 23 are inserted into the plurality of holes of the base material pipe 10 from the first end 11 side (insertion step, FIG. 10C). The base material pipe 10, the core rods 21 to 23, the support pipe 31 and the cap 34 are arranged in the vertical direction so that the second end 12 side of the base material pipe 10 is down, and the base material pipe 10 is arranged from the support pipe 31 side. The cap 34 and the second end 12 side of the base material tube 10 are heated and softened and spun while the inside of the air hole is decompressed to produce an MCF (a decompression process, a drawing process, FIG. 4D).

線引端（第２端１２側）は、母材管１０とコアロッド２１〜２３とが一体化され、キャップ３４の脱落後も封止された状態となる。逆の端（第１端１１側）は、非封止である。線引工程中、コアロッド２１〜２３は、引き伸ばされる状態で母材管１０と一体化され、逆の端（上端）から一部が突出することがある。 The drawing end (second end 12 side) is in a state where the base material pipe 10 and the core rods 21 to 23 are integrated and sealed after the cap 34 is removed. The opposite end (first end 11 side) is unsealed. During the drawing process, the core rods 21 to 23 are integrated with the base material pipe 10 in a stretched state, and a part thereof may protrude from the opposite end (upper end).

図５は、第２比較例の光ファイバ製造方法の一部変形例を説明する図である。この変形例では、母材管１０の第１端１１側に接続される支持管３１が、母材管１０の周辺孔の一部を塞ぐことで、周辺孔の開口からのコアロッドの突出を防止することができる。しかし、母材管１０の中心孔からのコアロッドの突出を防止するには別の対策が必要である。 FIG. 5 is a diagram for explaining a partial modification of the optical fiber manufacturing method of the second comparative example. In this modification, the support tube 31 connected to the first end 11 side of the base material pipe 10 closes a part of the peripheral hole of the base material pipe 10, thereby preventing the core rod from protruding from the opening of the peripheral hole. can do. However, another measure is required to prevent the core rod from protruding from the center hole of the base material pipe 10.

（第２実施形態）
図６および図７は、第２実施形態の光ファイバ製造方法を説明する図である。図７は、母材管１０の第１端１１側の部分を拡大して示す。第２実施形態の光ファイバ製造方法はＲＩＤ法を用いる。 (Second Embodiment)
6 and 7 are diagrams for explaining an optical fiber manufacturing method according to the second embodiment. FIG. 7 shows an enlarged portion of the base material pipe 10 on the first end 11 side. The optical fiber manufacturing method of the second embodiment uses the RID method.

母材管１０、コアロッド２１〜２３、支持管３１およびキャップ３４を準備し、母材管１０の空孔にコアロッド２１〜２３を挿入する（図６（ａ））。母材管１０は、石英ガラス製であり、軸方向に貫通して形成された複数の空孔を有する。母材管１０はＭＣＦの共通クラッドとなる。コアロッド２１〜２３は、石英ガラス製であり、ＭＣＦのコアおよび一部クラッドとなる。母材管１０の空孔は、第１端１１側でコアロッド２１〜２３が突出できない形状または大きさを有する突出防止部とされている（突出防止部形成工程、図７）。母材管１０の複数の空孔それぞれに第２端１２側からコアロッド２１〜２３を挿入する（挿入工程）。 The base material pipe 10, the core rods 21 to 23, the support pipe 31 and the cap 34 are prepared, and the core rods 21 to 23 are inserted into the holes of the base material pipe 10 (FIG. 6A). The base material tube 10 is made of quartz glass and has a plurality of holes formed so as to penetrate in the axial direction. The base material tube 10 is a common cladding of MCF. The core rods 21 to 23 are made of quartz glass and serve as an MCF core and a partial cladding. The hole of the base material pipe 10 is a protrusion preventing part having a shape or size that the core rods 21 to 23 cannot protrude on the first end 11 side (protrusion preventing part forming step, FIG. 7). The core rods 21 to 23 are inserted into the plurality of holes of the base material pipe 10 from the second end 12 side (insertion step).

支持管３１は、母材管１０の外径と同程度の外径を有し、母材管１０の空孔を塞がない程度の内径を有する。キャップ３４は、概略円錐形状を有し、底面が母材管１０の空孔を塞ぐことができる大きさを有する。母材管１０の第２端１２にキャップ３４を接続するとともに（封止部形成工程、図６（ｂ））。母材管１０の第１端１１に支持管３１を接続する（図６（ｃ））。母材管１０の各空孔の内壁面を気相エッチングし、母材管１０の各空孔内に浄化ガス（塩素や酸素）を流しながら母材管１０を加熱することによる浄化処理によって空孔内を清浄にしてもよい（浄化工程）。 The support tube 31 has an outer diameter that is approximately the same as the outer diameter of the base material tube 10, and has an inner diameter that does not block the air holes of the base material tube 10. The cap 34 has a substantially conical shape, and has a size such that the bottom surface can block the holes of the base material pipe 10. While connecting the cap 34 to the 2nd end 12 of the base material pipe | tube 10 (sealing part formation process, FIG.6 (b)). A support tube 31 is connected to the first end 11 of the base material tube 10 (FIG. 6C). The inner wall surface of each hole of the base material pipe 10 is vapor-phase etched, and the base material pipe 10 is heated by purifying the base material pipe 10 while purifying gas (chlorine or oxygen) flowing through the holes. The inside of the hole may be cleaned (cleaning step).

母材管１０の第２端１２側が下になるように母材管１０，コアロッド２１〜２３，支持管３１およびキャップ３４を鉛直方向に配置して、支持管３１の側から母材管１０の空孔内を減圧しながら、キャップ３４および母材管１０の第２端１２側を加熱軟化し紡糸して、ＭＣＦを製造する（減圧工程、線引工程、図６（ｄ））。 The base material pipe 10, the core rods 21 to 23, the support pipe 31 and the cap 34 are arranged in the vertical direction so that the second end 12 side of the base material pipe 10 is down, and the base material pipe 10 is arranged from the support pipe 31 side. The cap 34 and the second end 12 side of the base material pipe 10 are heated and softened and spun while the inside of the pores is decompressed to produce an MCF (a decompression step, a drawing step, FIG. 6 (d)).

線引端（第２端１２側）は、母材管１０とコアロッド２１〜２３とが一体化され、キャップ３４の脱落後も封止された状態となる。逆の端（第１端１１側）は突出防止部となっている。線引工程中、コアロッド２１〜２３は、引き伸びが起き第１端１１側の突出防止部へ向かって進展するが、突出防止部により母材管１０の空孔から突出することはない。 The drawing end (second end 12 side) is in a state where the base material pipe 10 and the core rods 21 to 23 are integrated and sealed after the cap 34 is removed. The opposite end (the first end 11 side) serves as a protrusion preventing portion. During the drawing process, the core rods 21 to 23 are stretched and progress toward the protrusion preventing part on the first end 11 side, but are not protruded from the holes of the base material pipe 10 by the protrusion preventing part.

なお、母材管１０が中心孔を有しない場合は、図５に示されるように母材管１０の第１端１１側に接続される支持管３１が母材管１０の周辺孔の一部を塞ぐ構成としてもよい。また、母材管１０の第１端１１側において、上記のように全ての空孔に突出防止部を設ける必要はなく、中心孔のみ突出防止部を設けてもよく、この場合、図５に示されるように周辺孔に対しては開口部の一部を塞ぐ厚さを有する支持管３１を接続することにより、コアロッドの突出を防止してもよい。また、中心孔にプレートを突出防止部として使用してもよい。 When the base material pipe 10 does not have a center hole, the support pipe 31 connected to the first end 11 side of the base material pipe 10 is a part of the peripheral hole of the base material pipe 10 as shown in FIG. It is good also as a structure which plugs up. Further, on the first end 11 side of the base material pipe 10, it is not necessary to provide a protrusion preventing part in all the holes as described above, and a protrusion preventing part may be provided only in the center hole. As shown in the drawing, the core rod may be prevented from protruding by connecting a support tube 31 having a thickness that blocks a part of the opening to the peripheral hole. Moreover, you may use a plate as a protrusion prevention part in a center hole.

支持管３１と母材管１０との接続部の断面積は、母材管１０および全コアロッドの総重量に対する単位断面積あたりの引っ張り応力が０.１５ＭＰａ以下となるように設計されているのが好適である。 The cross-sectional area of the connecting portion between the support pipe 31 and the base material pipe 10 is designed so that the tensile stress per unit cross-sectional area with respect to the total weight of the base material pipe 10 and all the core rods is 0.15 MPa or less. Is preferred.

（第３実施形態）
図８は、第３実施形態の光ファイバ製造方法を説明する図である。第３実施形態の光ファイバ製造方法はＲＩＤ法を用いる。 (Third embodiment)
FIG. 8 is a diagram for explaining an optical fiber manufacturing method according to the third embodiment. The optical fiber manufacturing method of the third embodiment uses the RID method.

第２実施形態に対し、第３実施形態では、母材管１０の第２端１２側において複数の空孔を連通する空間部１３が設けられている点で相違し、支持管３１が厚肉で母材管１０の第１端１１側において周辺孔を支持管３１が塞ぐ点で相違する。 The third embodiment is different from the second embodiment in that a space 13 that communicates a plurality of holes is provided on the second end 12 side of the base material tube 10, and the support tube 31 is thick. The difference is that the support tube 31 closes the peripheral hole on the first end 11 side of the base material tube 10.

本実施形態では、線引開始端（第２端１２）側において母材管１０とコアロッド２１〜２３とが一体化されると母材管１０の周辺孔が密閉状態になるので、一体化前に母材管１０の周辺孔内の空間を十分減圧状態としておく。 In the present embodiment, when the base material pipe 10 and the core rods 21 to 23 are integrated on the drawing start end (second end 12) side, the peripheral hole of the base material pipe 10 is in a sealed state. In addition, the space in the peripheral hole of the base material pipe 10 is sufficiently decompressed.

本実施形態では、母材管１０の線引開始端（第２端１２）側で複数の空孔が互いにつながることにより、一部の空孔が第２端１２側で開放されていれば、コアロッドと母材管１０とが一体化される線引き開始までの間に、母材管１０に形成した全ての空孔の内部を減圧状態とすることが可能となる。唯一残っている中心孔の空間のみを継続して減圧すればよい。 In the present embodiment, if a plurality of holes are connected to each other on the drawing start end (second end 12) side of the base material pipe 10, a part of the holes are opened on the second end 12 side, It becomes possible to make the inside of all the holes formed in the base material pipe 10 into a reduced pressure state before the drawing starts when the core rod and the base material pipe 10 are integrated. Only the remaining central hole space needs to be continuously decompressed.

本実施形態では、支持管３１を厚肉とすることが容易となる。それにより、光ファイバ内にコアを高密度に配置する場合、母材管１０の外周付近まで空孔を形成することが可能となり、また、より大きな母材の線引きも可能となる。 In the present embodiment, it is easy to make the support tube 31 thick. As a result, when the cores are arranged in the optical fiber at a high density, it is possible to form holes up to the vicinity of the outer periphery of the base material tube 10 and to draw a larger base material.

なお、連通させる空間は、必ずしも全ての空孔でなくてもよく、支持管３１により塞がれた空間と塞がれていない何れか一つの空孔とが連通されていればよい。また、連通する空間部は、母材管１０内だけでなく、キャップ３４内に設けられてもよい。 Note that the space to be communicated does not necessarily have to be all holes, and it is sufficient that the space closed by the support tube 31 and any one hole not closed are communicated. The communicating space may be provided not only in the base material pipe 10 but also in the cap 34.

また、接続強度に問題がなければ、図６に示されるように周辺孔を支持管３１で完全に塞がない構成としてもよい。支持管３１の厚さは、中心孔の開口を一部塞ぎ、中心孔のコアロッドが突出しない状態であれば、中心孔の開口を事前に狭くしておかなくてもよい。 If there is no problem in connection strength, the peripheral hole may not be completely blocked by the support tube 31 as shown in FIG. As long as the thickness of the support tube 31 is such that the opening of the central hole is partially blocked and the core rod of the central hole does not protrude, the opening of the central hole need not be narrowed in advance.

１０…母材管、１１…第１端、１２…第２端、１３…空間部、２１〜２３…コアロッド、３１，３２…支持管、３３…支持棒、３４…キャップ、４０…バーナ。 DESCRIPTION OF SYMBOLS 10 ... Base material pipe | tube, 11 ... 1st end, 12 ... 2nd end, 13 ... Space part, 21-23 ... Core rod, 31, 32 ... Support pipe, 33 ... Support rod, 34 ... Cap, 40 ... Burner.

Claims

A step of inserting a core rod made of quartz glass into each of a plurality of holes formed in the axial direction of the base material tube made of quartz glass;
Before the insertion step, a protrusion preventing portion having a hole window for preventing the core rod from protruding from the base material tube and depressurizing the inside of the hole in each step after the insertion step. A protrusion preventing part forming step formed on the first end side of the material pipe;
After the inserting step, a depressurizing step of depressurizing the inside of the base material tube through a support tube connected to the first end of the base material tube;
An integration step of heating and softening the second end side of the base material tube under the decompression step to integrate the base material tube and the core rod;
A drawing step of drawing an optical fiber by drawing the base material tube and the core rod;
Bei to give a,
The protrusion preventing portion includes a first condition in which the hole of the base material pipe has a shape or a size in which the core rod cannot protrude on the first end side, and the hole of the base material pipe is the support pipe. A second condition in which the core rod cannot protrude by being partially blocked by one of these or a combination thereof,
Optical fiber manufacturing method.

A sealing part forming step of forming a sealing part for sealing the holes on the second end side of the base material pipe;
The optical fiber manufacturing method according to claim 1.

The integration step is a collapse step for integrating the entire core rod with the base material pipe before the drawing step.
The optical fiber manufacturing method according to claim 1 or 2.

The integration step is a step of integrating the core rod and the base material tube on the second end side of the base material tube at the start of the drawing step,
Performing the drawing step under the decompression step;
The optical fiber manufacturing method according to claim 1 or 2.

The sealing portion is a support rod that seals all the holes on the second end side of the base material pipe.
The optical fiber manufacturing method according to claim 2.

A step of inserting a core rod made of quartz glass into each of a plurality of holes formed in the axial direction of the base material tube made of quartz glass;
Before the insertion step, a protrusion preventing portion having a hole window for preventing the core rod from protruding from the base material tube and depressurizing the inside of the hole in each step after the insertion step. A protrusion preventing part forming step formed on the first end side of the material pipe;
A sealing part forming step of forming a sealing part for sealing the holes on the second end side of the base material pipe;
A depressurizing step of depressurizing the pores of the base material pipe via a support pipe connected to the first end of the base material pipe;
An integration step of heating and softening the second end side of the base material tube under the decompression step to integrate the base material tube and the core rod;
A drawing step of drawing an optical fiber by drawing the base material tube and the core rod;
With
The sealing portion is a cap that seals all the holes in a state in which a part or all of the holes are communicated with each other on the second end side of the base material pipe.
Optical fiber manufacturing method.

The integration step is a collapse step for integrating the entire core rod with the base material pipe before the drawing step.
The optical fiber manufacturing method according to claim 6.

The integration step is a step of integrating the core rod and the base material tube on the second end side of the base material tube at the start of the drawing step,
Performing the drawing step under the decompression step;
The optical fiber manufacturing method according to claim 6.