JP6560178B2

JP6560178B2 - Multi-core fiber preform manufacturing method and multi-core fiber manufacturing method

Info

Publication number: JP6560178B2
Application number: JP2016191693A
Authority: JP
Inventors: 智洋権田; 妙子渋田; 勝徳今村; 杉崎　隆一; 隆一杉崎
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 2016-09-29
Filing date: 2016-09-29
Publication date: 2019-08-14
Anticipated expiration: 2036-09-29
Also published as: JP2018052775A

Description

本発明は、マルチコアファイバ母材の製造方法及びこれを用いたマルチコアファイバの製造方法に関するものである。 The present invention relates to a method for producing a multi-core fiber preform and a method for producing a multi-core fiber using the same.

マルチコアファイバとは、長手方向の軸に沿って延びる複数のコア部を有する光ファイバである。マルチコアファイバの複数のコア部のそれぞれで信号光を伝送することで、空間多重伝送が実現される。この種のマルチコアファイバは、大容量伝送や、データセンタにおける高密度配線などへの適用が期待されている。 A multi-core fiber is an optical fiber having a plurality of core portions extending along a longitudinal axis. Spatial multiplexing transmission is realized by transmitting signal light through each of the plurality of core portions of the multi-core fiber. This type of multi-core fiber is expected to be applied to high-capacity transmission and high-density wiring in data centers.

マルチコアファイバを製造するための光ファイバ母材であるマルチコアファイバ母材の製造方法として、穿孔法を用いるものが知られている。穿孔法を用いたマルチコアファイバ母材の製造方法では、たとえば、はじめに円柱状のガラス母材をドリル加工などによって穿孔することで、ガラス母材の長手方向に延びる複数の貫通孔を形成し、クラッド母材とする。つづいて、クラッド母材の貫通孔のそれぞれにコア母材を挿入し、加熱一体化させることにより、マルチコアファイバ母材を作製する。穿孔法のうち、線引炉により加熱一体化しながら線引きすることにより、マルチコアファイバを製造する方法は線引き一体化法とも呼ばれる。 As a manufacturing method of a multi-core fiber preform that is an optical fiber preform for manufacturing a multi-core fiber, a method using a perforation method is known. In the method of manufacturing a multi-core fiber preform using the drilling method, for example, a cylindrical glass preform is first drilled by drilling or the like to form a plurality of through holes extending in the longitudinal direction of the glass preform, and then cladding Use as a base material. Subsequently, a core base material is inserted into each of the through holes of the clad base material and integrated by heating to produce a multi-core fiber base material. Among the perforating methods, a method of producing a multi-core fiber by drawing while heating and integrating in a drawing furnace is also called a drawing integrated method.

ここで、製造歩留まりや製造性を向上させるため、クラッド母材の貫通孔の内径は、コア母材を確実に挿入できるようにコア母材の外径よりもわずかに大きく形成されている。その結果、マルチコアファイバ母材においてはコア母材とクラッド母材との間にわずかに隙間ができる。このような隙間に空気が残存していると、線引き後にマルチコアファイバ内に気泡が存在する等の不具合が生じる虞がある。そのため、通常、線引き一体化法においては、コア母材とクラッド母材とを一体化する際に、コア母材とクラッド母材との隙間を真空ポンプ等で吸引し、隙間内を真空又は減圧状態としている。 Here, in order to improve the manufacturing yield and manufacturability, the inner diameter of the through hole of the clad base material is formed slightly larger than the outer diameter of the core base material so that the core base material can be reliably inserted. As a result, in the multi-core fiber preform, a slight gap is formed between the core preform and the clad preform. If air remains in such a gap, there is a risk that defects such as bubbles exist in the multi-core fiber after drawing. Therefore, normally, in the wire drawing integration method, when the core base material and the clad base material are integrated, the gap between the core base material and the clad base material is sucked with a vacuum pump or the like, and the inside of the gap is evacuated or decompressed. State.

そこで、隙間の吸引をするために、クラッド母材の一端に円筒部材を溶着接続し、この円筒部材を介して各コア母材とクラッド母材との隙間を一括して吸引する技術が知られている（特許文献１参照）。なお、円筒部材は貫通孔を塞がないようにクラッド母材に溶着接続される。 Therefore, in order to suck the gap, a technique is known in which a cylindrical member is welded and connected to one end of the clad base material, and the gap between each core base material and the clad base material is collectively sucked through the cylindrical member. (See Patent Document 1). The cylindrical member is welded and connected to the clad base material so as not to block the through hole.

特開２０１５−１５１２７９号公報Japanese Patent Laying-Open No. 2015-151279

ところで、近年、光ファイバに対する長尺化、低コスト化等の要求に応じて、光ファイバ母材の大型化（直径や長さの増加）の要求が高まっている。 By the way, in recent years, in response to demands for lengthening and cost reduction for optical fibers, there has been an increasing demand for larger optical fiber preforms (increases in diameter and length).

しかしながら、光ファイバ母材は大型化するほどその重量も増加する。特に、上記のようなマルチコアファイバ母材の場合、重量が増加するとクラッド母材と円筒部材との接合強度不足が懸念されるという問題がある。円筒部材の厚さ（すなわち外径と内径との差）を厚くすれば、クラッド母材と円筒部材との接合面積を増加させ、接合強度も増加させることはできる。しかしながら、従来技術では、円筒部材の厚さをあまり厚くすると、クラッド母材の貫通孔、特にクラッド母材の最外周側の貫通孔が、円筒部材によって一部又は全部が塞がれ、塞がれた貫通孔に対する吸引による隙間の減圧が効率的にできない又は不可能となる虞がある。 However, the weight of the optical fiber preform increases as the size of the optical fiber preform increases. In particular, in the case of the multi-core fiber preform as described above, there is a problem that when the weight is increased, the bonding strength between the clad preform and the cylindrical member may be insufficient. If the thickness of the cylindrical member (that is, the difference between the outer diameter and the inner diameter) is increased, the bonding area between the clad base material and the cylindrical member can be increased, and the bonding strength can be increased. However, in the prior art, if the thickness of the cylindrical member is made too thick, the through hole of the clad base material, in particular, the through hole on the outermost peripheral side of the clad base material is partially or entirely blocked by the cylindrical member. There is a possibility that the pressure reduction of the gap due to suction with respect to the through-holes may not be efficient or impossible.

本発明は、上記に鑑みてなされたものであって、クラッド母材と円筒部材との接合強度を増加させつつ、クラッド母材と各コア母材との隙間を効率的に減圧させることができるマルチコアファイバ母材の製造方法及びこれを用いたマルチコアファイバの製造方法を提供することを目的とする。 The present invention has been made in view of the above, and can efficiently reduce the gap between the clad base material and each core base material while increasing the bonding strength between the clad base material and the cylindrical member. It aims at providing the manufacturing method of a multi-core fiber preform, and the manufacturing method of a multi-core fiber using the same.

上述した課題を解決し、目的を達成するために、本発明の一態様に係るマルチコアファイバ母材の製造方法は、円柱状のガラス母材に、該ガラス母材の長手方向に延びる複数の貫通孔が形成されたクラッド母材を準備する準備工程と、前記クラッド母材の一方の端部に、該クラッド母材と同軸で円筒部材を接続する接続工程と、前記クラッド母材の複数の貫通孔のそれぞれにコア母材を挿入する挿入工程と、を含むマルチコアファイバ母材の製造方法であって、前記円筒部材の内径は、前記クラッド母材に形成された前記複数の貫通孔のうち最外周側に位置する貫通孔の外接円の直径よりも小さく、前記準備工程において、前記クラッド母材には、前記複数の貫通孔のうち上面視で前記円筒部材と少なくとも一部が重なる貫通孔と、前記円筒部材の内部と、を連通させるための連通構造が形成されていることを特徴とする。 In order to solve the above-described problems and achieve the object, a method for manufacturing a multi-core fiber preform according to one embodiment of the present invention includes a plurality of penetrations extending in a longitudinal direction of a glass preform in a cylindrical glass preform. A preparation step of preparing a clad base material in which holes are formed; a connecting step of connecting a cylindrical member coaxially with the clad base material to one end of the clad base material; and a plurality of penetrations of the clad base material An insertion step of inserting a core preform into each of the holes, wherein the cylindrical member has an inner diameter that is the largest among the plurality of through-holes formed in the cladding preform. The diameter of the circumscribed circle of the through hole located on the outer peripheral side is smaller than the diameter of the circumscribed circle of the through hole. The cylinder Wherein the communicating structure for communicating with the interior of the timber, a are formed.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記連通構造は、前記クラッド母材の前記一方の端部に形成された凹部により構成されていることを特徴とする。 In the method for manufacturing a multi-core fiber preform according to an aspect of the present invention, the communication structure is configured by a recess formed at the one end of the clad preform.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記凹部は、環状の溝部であることを特徴とする。 Moreover, the manufacturing method of the multi-core fiber preform which concerns on 1 aspect of this invention is characterized by the said recessed part being a cyclic | annular groove part.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記凹部は、円状の凹部であることを特徴とする。 Moreover, the manufacturing method of the multi-core fiber preform which concerns on 1 aspect of this invention is characterized by the said recessed part being a circular recessed part.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記凹部は、上面視で前記円筒部材と少なくとも一部が重なる貫通孔と、上面視で前記円筒部材と重ならない貫通孔と、を連通する連通溝部により構成されていることを特徴とする。 In the method for manufacturing a multi-core fiber preform according to one aspect of the present invention, the recess includes a through hole that overlaps at least a part with the cylindrical member in a top view, and a through hole that does not overlap with the cylindrical member in a top view. It is comprised by the communication groove part which connects these.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記連通構造は、前記クラッド母材の前記一方の端部側に設けられた連通部により形成されていることを特徴とする。 In the method for manufacturing a multi-core fiber preform according to one aspect of the present invention, the communication structure is formed by a communication portion provided on the one end side of the clad preform. .

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記連通構造は、前記連通部において、前記円筒部材の内部に対して開放されるように設けられた開口部と、それぞれの一端が前記貫通孔のそれぞれと接続され、それぞれの他端が前記開口部に接続された複数の連通孔とにより構成されていることを特徴とする。 Further, in the method for manufacturing a multi-core fiber preform according to one aspect of the present invention, the communication structure includes an opening provided in the communication portion so as to be open to the inside of the cylindrical member, One end is connected to each of the through holes, and the other end is constituted by a plurality of communication holes connected to the opening.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記連通構造は、前記連通部において、前記円筒部材の内部に対して開放されるように設けられた開口部と、前記複数の貫通孔と前記開口部とを一括して連通する連通空間と、により構成されていることを特徴とする。 Further, in the method for manufacturing a multi-core fiber preform according to one aspect of the present invention, the communication structure includes an opening provided in the communication portion so as to be open to the inside of the cylindrical member, and the plurality of the communication structures. It is comprised by the communicating space which connects the through-hole and the said opening part collectively.

また、本発明の一態様に係るマルチコアファイバ母材の製造方法は、前記連通部の外径が前記クラッド母材の外径より大きいことを特徴とする。 Moreover, the manufacturing method of the multi-core fiber preform which concerns on 1 aspect of this invention is characterized by the outer diameter of the said communication part being larger than the outer diameter of the said clad | crud base material.

また、本発明の一態様に係るマルチコアファイバの製造方法は、本発明の一態様に係るマルチコアファイバ母材の製造方法により製造されたマルチコアファイバ母材の前記貫通孔と前記クラッド母材との隙間を、前記円筒部材を介して減圧しながら、前記マルチコアファイバ母材の前記一方の端部とは反対に位置する他の端部を加熱溶融し、前記他の端部から、長手方向の軸に沿って延びる複数のコア部を有するマルチコアファイバを線引きすることを特徴とする。 In addition, a multicore fiber manufacturing method according to an aspect of the present invention includes a gap between the through-hole of the multicore fiber preform manufactured by the multicore fiber preform manufacturing method according to the aspect of the present invention and the clad preform. The other end portion of the multi-core fiber preform opposite to the one end portion is heated and melted while the pressure is reduced through the cylindrical member, and from the other end portion to the longitudinal axis. A multi-core fiber having a plurality of core portions extending along the line is drawn.

本発明によれば、クラッド母材と円筒部材との接合強度を増加させつつ、クラッド母材と各コア母材との隙間を効率的に減圧させることができるという効果を奏する。 According to the present invention, it is possible to efficiently reduce the gap between the clad base material and each core base material while increasing the bonding strength between the clad base material and the cylindrical member.

図１は、実施形態１に係るマルチコアファイバの製造方法によって製造するマルチコアファイバの模式的な断面図である。FIG. 1 is a schematic cross-sectional view of a multicore fiber manufactured by the method for manufacturing a multicore fiber according to the first embodiment. 図２は、実施形態１に係る製造方法のフロー図である。FIG. 2 is a flowchart of the manufacturing method according to the first embodiment. 図３は、クラッド母材を説明する模式図である。FIG. 3 is a schematic diagram illustrating a clad base material. 図４は、接続工程を説明する模式図である。FIG. 4 is a schematic diagram illustrating the connection process. 図５は、コア母材の挿入工程を説明する模式図である。FIG. 5 is a schematic diagram for explaining the core base material insertion step. 図６は、線引工程を説明する模式図である。FIG. 6 is a schematic diagram for explaining a drawing process. 図７は、挿入工程後のマルチコアファイバ母材の構成を示す模式図である。FIG. 7 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step. 図８は、変形例１における挿入工程後のマルチコアファイバ母材の構成を示す模式図である。FIG. 8 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step in Modification 1. 図９は、変形例２における挿入工程後のマルチコアファイバ母材の構成を示す模式図である。FIG. 9 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step in Modification 2. 図１０は、変形例３における挿入工程後のマルチコアファイバ母材の構成を示す模式図である。FIG. 10 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step in Modification 3. 図１１は、変形例４における挿入工程後のマルチコアファイバ母材の構成を示す模式図である。FIG. 11 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step in Modification 4. 図１２は、変形例５、６における挿入工程後のマルチコアファイバ母材の構成を示す模式図である。FIG. 12 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step in Modifications 5 and 6.

以下に、図面を参照して本発明の実施形態を詳細に説明する。なお、この実施形態によりこの発明が限定されるものではない。また、各図面において、同一又は対応する要素には適宜同一の符号を付している。
また、本明細書において特に定義しない用語については、ＩＴＵ−Ｔ（国際電気通信連合）Ｇ．６５０．１及びＧ．６５０．２における定義、測定方法に従うものとする。 Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. Moreover, in each drawing, the same code | symbol is attached | subjected suitably to the same or corresponding element.
For terms not specifically defined in this specification, ITU-T (International Telecommunication Union) 650.1 and G.R. It shall follow the definition and measurement method in 650.2.

（実施形態１）
図１は、本発明の実施形態１に係る製造方法によって製造するマルチコアファイバの、長手方向と垂直な断面における模式的な断面図である。図１に示すように、被覆されたマルチコアファイバ１は、ガラスからなるマルチコアファイバ２の外周に樹脂などからなる被覆３が形成されたものである。マルチコアファイバ２は、断面が略円形の複数のコア部２ａと、コア部２ａの外周に形成された、断面が略円形のクラッド部２ｂとを備える。複数のコア部２ａは、正方格子状に配列しており、コア部２ａａ、２ａｂ、２ａｃからなる。コア部２ａａはマルチコアファイバ２において最外周側に位置し、マルチコアファイバ２の中心軸から等距離にある８個のコア部である。コア部２ａｂはコア部２ａａよりも少し内周側に位置し、マルチコアファイバ２の中心軸から等距離にある４個のコア部である。コア部２ａｃはコア部２ａｂよりもさらに内周側に位置する、正方格子状に配列した９個のコア部である。 (Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a multi-core fiber manufactured by the manufacturing method according to Embodiment 1 of the present invention in a cross section perpendicular to the longitudinal direction. As shown in FIG. 1, a coated multicore fiber 1 is formed by forming a coating 3 made of resin or the like on the outer periphery of a multicore fiber 2 made of glass. The multi-core fiber 2 includes a plurality of core portions 2a having a substantially circular cross section, and a clad portion 2b having a substantially circular cross section formed on the outer periphery of the core portion 2a. The plurality of core portions 2a are arranged in a square lattice pattern, and include core portions 2aa, 2ab, and 2ac. The core portions 2aa are eight core portions located on the outermost peripheral side in the multi-core fiber 2 and equidistant from the central axis of the multi-core fiber 2. The core portion 2ab is four core portions that are located slightly closer to the inner periphery than the core portion 2aa and are equidistant from the central axis of the multi-core fiber 2. The core portion 2ac is nine core portions arranged in a square lattice shape, located further on the inner peripheral side than the core portion 2ab.

コア部２ａは、いずれもゲルマニウム（Ｇｅ）などの屈折率を高めるためのドーパントが添加された石英系ガラスからなる。クラッド部２ｂは、コア部２ａよりも屈折率が低い石英系ガラス、たとえば屈折率調整用のドーパントを含まない純石英ガラスからなる。 Each of the core portions 2a is made of quartz glass to which a dopant for increasing the refractive index such as germanium (Ge) is added. The clad portion 2b is made of quartz glass having a lower refractive index than that of the core portion 2a, for example, pure silica glass not containing a dopant for adjusting the refractive index.

つぎに、本実施形態１に係る製造方法の概略を説明する。図２は、実施形態１に係る製造方法のフロー図である。本製造方法では、はじめに、クラッド母材を準備する準備工程を行う（ステップＳ１０１）。クラッド母材は、円柱状のガラス母材に、該ガラス母材の長手方向に延びる複数の貫通孔が形成されたものである。つづいて、クラッド母材の一方の端部に円筒部材を接続する接続工程を行う（ステップＳ１０２）。つづいて、クラッド母材の複数の貫通孔のそれぞれにコア母材を挿入する挿入工程を行う（ステップＳ１０３）。つづいて、クラッド母材の端部のうち円筒部材を接続した一方の端部とは反対に位置する他の端部を封止する封止工程を行う（ステップＳ１０４）。これによりマルチコアファイバ母材が作製される。つづいて、マルチコアファイバ母材の封止した他の端部を加熱溶融し、マルチコアファイバを線引きする線引工程を行う（ステップＳ１０５）。これによりマルチコアファイバ２が線引きされる。線引きされたマルチコアファイバ２に被覆３が形成され、被覆されたマルチコアファイバ１が製造される。 Next, an outline of the manufacturing method according to the first embodiment will be described. FIG. 2 is a flowchart of the manufacturing method according to the first embodiment. In this manufacturing method, first, a preparation process for preparing a clad base material is performed (step S101). The clad base material is a cylindrical glass base material in which a plurality of through holes extending in the longitudinal direction of the glass base material are formed. Subsequently, a connecting step of connecting the cylindrical member to one end of the clad base material is performed (step S102). Subsequently, an insertion step of inserting the core base material into each of the plurality of through holes of the clad base material is performed (step S103). Subsequently, a sealing step of sealing the other end located opposite to the one end connected to the cylindrical member among the ends of the clad base material is performed (step S104). As a result, a multi-core fiber preform is produced. Subsequently, the other end portion sealed with the multi-core fiber preform is heated and melted, and a drawing process for drawing the multi-core fiber is performed (step S105). Thereby, the multi-core fiber 2 is drawn. A coated core 3 is formed on the drawn multi-core fiber 2, and the coated multi-core fiber 1 is manufactured.

なお、本実施形態１では、取り扱い性の観点から、接続工程（ステップＳ１０２）後に挿入工程（ステップＳ１０３）を設けているが、挿入工程と接続工程の順序は逆にしてもよい。すなわち、クラッド母材の複数の貫通孔のそれぞれにコア母材を挿入した後、一方の端部に円筒部材を接続してもよい。 In the first embodiment, from the viewpoint of handling, the insertion step (step S103) is provided after the connection step (step S102). However, the order of the insertion step and the connection step may be reversed. That is, after inserting the core base material into each of the plurality of through holes of the clad base material, the cylindrical member may be connected to one end.

つぎに、本製造方法について具体的に説明する。図３は、ステップＳ１０１において準備するクラッド母材を説明する模式図である。クラッド母材４は以下のように準備される。まず、図３（ａ）に示す、クラッド部２ｂと同じガラス材料からなる円柱状のガラス材４´に、ドリルなどを用いて、図３（ｂ）に上面図を示すように、ガラス材４´の長手方向に延びる複数の貫通孔４ａを形成する。つづいて、図３（ｃ）に上面図、図３（ｄ）に斜視図を示すように、環状の溝部としての溝部４ｂをガラス材４´の一方の端部４ｃａに形成し、クラッド母材４とする。なお、溝部４ｂは端部４ｃａに対する機械的加工等で形成することができる。 Next, the production method will be specifically described. FIG. 3 is a schematic diagram illustrating the clad base material prepared in step S101. The clad base material 4 is prepared as follows. First, a cylindrical glass material 4 ′ made of the same glass material as that of the clad portion 2b shown in FIG. 3A is drilled, and a glass material 4 as shown in FIG. A plurality of through-holes 4a extending in the longitudinal direction of 'are formed. Subsequently, as shown in a top view in FIG. 3C and a perspective view in FIG. 3D, a groove portion 4b as an annular groove portion is formed on one end portion 4ca of the glass material 4 ′, and the clad base material is formed. 4. The groove 4b can be formed by mechanical processing or the like on the end 4ca.

複数の貫通孔４ａは、図１に示すマルチコアファイバ２におけるコア部２ａａ、２ａｂ、２ａｃの配列と同じ、正方格子状の配列で形成される。複数の貫通孔４ａは、貫通孔４ａａ、４ａｂ、４ａｃからなる。貫通孔４ａａはクラッド母材４において最外周側に位置し、クラッド母材４の中心軸から等距離にある８個の貫通孔である。貫通孔４ａｂは貫通孔４ａａよりも少し内周側に位置し、クラッド母材４の中心軸から等距離にある４個の貫通孔である。貫通孔４ａｃは貫通孔４ａｂよりもさらに内周側に位置する、正方格子状に配列した９個の貫通孔である。 The plurality of through holes 4a are formed in a square lattice-like arrangement that is the same as the arrangement of the core portions 2aa, 2ab, and 2ac in the multi-core fiber 2 shown in FIG. The plurality of through holes 4a include through holes 4aa, 4ab, and 4ac. The through holes 4aa are eight through holes that are located on the outermost peripheral side of the clad base material 4 and are equidistant from the central axis of the clad base material 4. The through-holes 4ab are four through-holes that are located slightly on the inner peripheral side of the through-hole 4aa and are equidistant from the central axis of the cladding base material 4. The through-holes 4ac are nine through-holes arranged in the form of a square lattice and located further on the inner peripheral side than the through-hole 4ab.

溝部４ｂは、クラッド母材４と略同軸に形成される。
また、図３（ｃ）に示す外接円Ｃ１は、複数の貫通孔４ａのうち最外周側に位置する貫通孔４ａａの外接円を示している。外接円Ｃ１もクラッド母材４と略同軸である。溝部４ｂの外径は外接円Ｃ１の直径Ｄ１よりも小さくなっているが、これについては後ほど詳述する。 The groove portion 4 b is formed substantially coaxially with the clad base material 4.
A circumscribed circle C1 shown in FIG. 3C is a circumscribed circle of the through hole 4aa located on the outermost peripheral side among the plurality of through holes 4a. The circumscribed circle C1 is also substantially coaxial with the cladding base material 4. The outer diameter of the groove 4b is smaller than the diameter D1 of the circumscribed circle C1, which will be described in detail later.

図４は、ステップＳ１０２の接続工程を説明する模式図である。この工程では、図４に示すように、クラッド母材４の、溝部４ｂが形成された一方の端部４ｃａに、クラッド母材４と略同軸で円筒部材５を接続する。接続はたとえば溶着接続によって行うことができる。溶着によって接続を行う場合は、円筒部材５はクラッド母材４と同じガラス材料からなるものであることが好ましい。また、円筒部材５は、外径がクラッド母材４の外径と略等しいものであるが、クラッド母材４の外径よりも大きい外径を有していてもよい。ここで、円筒部材５の内径をＤ２とする。 FIG. 4 is a schematic diagram for explaining the connection process in step S102. In this step, as shown in FIG. 4, a cylindrical member 5 is connected substantially coaxially with the cladding base material 4 to one end 4 ca of the cladding base material 4 where the groove 4 b is formed. The connection can be made, for example, by welding connection. When the connection is made by welding, the cylindrical member 5 is preferably made of the same glass material as that of the clad base material 4. The cylindrical member 5 has an outer diameter substantially equal to the outer diameter of the clad base material 4, but may have an outer diameter larger than the outer diameter of the clad base material 4. Here, the inner diameter of the cylindrical member 5 is D2.

図５は、ステップＳ１０３の挿入工程を説明する模式図である。この工程では、図５に示すように、クラッド母材４の複数の貫通孔４ａのそれぞれにコア母材６を挿入する。なお、図５では図面の簡略化のために貫通孔４ａ及び挿入されるコア母材６のうちそれぞれ一つのみ示している。コア母材６は、本実施形態１では、マルチコアファイバ２においてコア部２ａとなるコア形成部と、コア形成部の外周に形成され、マルチコアファイバ２においてクラッド部２ｂの一部となるクラッド形成部とを備えるものである。このようなコア母材６は、ＶＡＤ（Vapor phase Axial Deposition）法、ＯＶＤ（Outside Vapor Deposition）法、ＭＣＶＤ（Modified Chemical Vapor Deposition）法などの周知の方法を用いて作製できるものである。その後、クラッド母材４の端部のうち円筒部材５を接続した一方の端部４ｃａとは反対に位置する他の端部４ｃｂを加熱溶融して封止する。これによりマルチコアファイバ母材１０が作製される。 FIG. 5 is a schematic diagram for explaining the insertion step of step S103. In this step, as shown in FIG. 5, the core base material 6 is inserted into each of the plurality of through holes 4 a of the clad base material 4. In FIG. 5, only one of the through hole 4a and the core base material 6 to be inserted is shown for simplification of the drawing. In the first embodiment, the core base material 6 is formed on the core forming portion that becomes the core portion 2a in the multi-core fiber 2 and the cladding forming portion that is formed on the outer periphery of the core forming portion and becomes a part of the cladding portion 2b in the multi-core fiber 2. Are provided. Such a core base material 6 can be manufactured using a known method such as a VAD (Vapor phase Axial Deposition) method, an OVD (Outside Vapor Deposition) method, or an MCVD (Modified Chemical Vapor Deposition) method. Thereafter, the other end portion 4cb located opposite to the one end portion 4ca to which the cylindrical member 5 is connected among the end portions of the clad base material 4 is heated and melted and sealed. Thereby, the multi-core fiber preform 10 is produced.

つぎに、このマルチコアファイバ母材１０からマルチコアファイバ２を線引きする。図６は、線引工程を説明する模式図である。図６に示す線引装置１００は、ヒータ１０１ａを有する線引加熱炉１０１と、吸引機構１０２と、外径測定器１０３と、被覆樹脂塗布装置１０４と、樹脂硬化装置１０５と、キャプスタンローラ１０６と、ガイドロール１０７と、制御器Ｃとを備える。なお、線引装置１００は、マルチコアファイバ母材１０の回転昇降機構（図示せず）も備えている。吸引機構１０２は、吸引用コネクタ１０２ａと、吸引用コネクタ１０２ａに接続した吸引路１０２ｂと、吸引路１０２ｂに接続した吸引装置１０２ｃとを備える。吸引装置１０２ｃはたとえば真空ポンプで構成される。 Next, the multi-core fiber 2 is drawn from the multi-core fiber preform 10. FIG. 6 is a schematic diagram for explaining a drawing process. A drawing apparatus 100 shown in FIG. 6 includes a drawing heating furnace 101 having a heater 101a, a suction mechanism 102, an outer diameter measuring device 103, a coating resin coating apparatus 104, a resin curing apparatus 105, and a capstan roller 106. And a guide roll 107 and a controller C. The drawing apparatus 100 also includes a rotary lifting mechanism (not shown) for the multi-core fiber preform 10. The suction mechanism 102 includes a suction connector 102a, a suction path 102b connected to the suction connector 102a, and a suction device 102c connected to the suction path 102b. The suction device 102c is constituted by a vacuum pump, for example.

以下、マルチコアファイバ２の線引工程をより具体的に説明する。
はじめに、マルチコアファイバ母材１０を線引加熱炉１０１にセットし、マルチコアファイバ母材１０の上端にある円筒部材５に吸引用コネクタ１０２ａを接続する。つぎに、マルチコアファイバ母材１０の下端（端部４ｃｂ側）をヒータ１０１ａにて加熱溶融して、線引きする。これによって、マルチコアファイバ母材１０からマルチコアファイバ２が線引きされる。 Hereinafter, the drawing process of the multi-core fiber 2 will be described more specifically.
First, the multi-core fiber preform 10 is set in the drawing heating furnace 101, and the suction connector 102a is connected to the cylindrical member 5 at the upper end of the multi-core fiber preform 10. Next, the lower end (end portion 4cb side) of the multi-core fiber preform 10 is heated and melted by the heater 101a and drawn. As a result, the multicore fiber 2 is drawn from the multicore fiber preform 10.

線引きの間、マルチコアファイバ母材１０のコア母材とクラッド母材との隙間は減圧状態とされる。減圧は、吸引装置１０２ｃが吸引路１０２ｂ、吸引用コネクタ１０２ａ、円筒部材５を介して、矢印Ｙ１の方向に隙間内の気体を吸引することにより実現される。吸引装置１０２ｃの動作は制御器Ｃによって制御される。 During the drawing, the gap between the core preform and the clad preform of the multi-core fiber preform 10 is in a reduced pressure state. The decompression is realized by the suction device 102c sucking the gas in the gap in the direction of the arrow Y1 through the suction path 102b, the suction connector 102a, and the cylindrical member 5. The operation of the suction device 102c is controlled by the controller C.

線引きされたマルチコアファイバ２は、公知の被覆樹脂塗布装置１０４と樹脂硬化装置１０５とによって被覆を形成されて、被覆されたマルチコアファイバ１となる。被覆されたマルチコアファイバ１は、その後、キャプスタンローラ１０６とガイドロール１０７とによって送られ、不図示の巻取り器に巻取られる。制御器Ｃは、外径測定器１０３によって測定されるマルチコアファイバ２の外径が所望の値になるようにキャプスタンローラ１０６の回転速度（すなわちマルチコアファイバ２の線引き速度）及び回転昇降機構によるマルチコアファイバ母材１０の昇降速度を制御する。 The drawn multi-core fiber 2 is coated with a known coating resin coating device 104 and resin curing device 105 to form a coated multi-core fiber 1. The coated multi-core fiber 1 is then fed by a capstan roller 106 and a guide roll 107 and wound around a winder (not shown). The controller C is configured so that the rotation speed of the capstan roller 106 (that is, the drawing speed of the multicore fiber 2) and the multicore by the rotary lifting mechanism so that the outer diameter of the multicore fiber 2 measured by the outer diameter measuring device 103 becomes a desired value. The raising / lowering speed of the fiber preform 10 is controlled.

ここで、本製造方法では、円筒部材５の内径Ｄ２が、クラッド母材４の最外周側に位置する貫通孔４ａａの外接円Ｃ１の直径Ｄ１よりも小さいので、従来技術のように内径Ｄ２が直径Ｄ１以上の場合と比較して、円筒部材５とクラッド母材４との接合面積が大きい。その結果、円筒部材５とクラッド母材４との接合強度を増加させることができる。したがって、クラッド母材４を大型化できる。 Here, in the present manufacturing method, the inner diameter D2 of the cylindrical member 5 is smaller than the diameter D1 of the circumscribed circle C1 of the through hole 4aa located on the outermost peripheral side of the clad base material 4, so that the inner diameter D2 is the same as in the prior art. Compared with the case of diameter D1 or more, the joining area of the cylindrical member 5 and the clad base material 4 is large. As a result, the bonding strength between the cylindrical member 5 and the clad base material 4 can be increased. Therefore, the clad base material 4 can be enlarged.

さらに、本製造方法では、クラッド母材４には、複数の貫通孔４ａのうち上面視で円筒部材５と少なくとも一部が重なる貫通孔４ａａと、円筒部材５の内部と、を連通させるための連通構造を構成する凹部としての溝部４ｂが、クラッド母材４の端部４ｃａに形成されている。その結果、クラッド母材４と各コア母材６との隙間を効率的に減圧させることができる。
ここで、上面視とは、クラッド母材４を、その中心軸に沿って、円筒部材５を接続する端部側から視ることを意味する。 Further, in the present manufacturing method, the cladding base material 4 communicates with the inside of the cylindrical member 5 and the through hole 4aa at least partially overlapping the cylindrical member 5 in the top view among the plurality of through holes 4a. A groove portion 4 b as a concave portion constituting the communication structure is formed in the end portion 4 ca of the clad base material 4. As a result, the gap between the clad base material 4 and each core base material 6 can be efficiently decompressed.
Here, the top view means that the cladding base material 4 is viewed from the end side connecting the cylindrical member 5 along the central axis.

以下、具体的に説明する。図７は、挿入工程後のマルチコアファイバ母材１０の構成を示す模式図である。図７（ａ）は端部４ｃａ側からみた上面図、図７（ｂ）は図７（ａ）のＡ−Ａ線一部断面図、図７（ｃ）は図７（ａ）のＢ−Ｂ線一部断面図である。図７（ａ）において、符号４ｂａは溝部４ｂの外径を規定する内壁、符号４ｂｂは溝部４ｂの内径を規定する内壁を示している。したがって、溝部４ｂの幅ｗ１は、（溝部４ｂの外径−溝部４ｂの内径）／２、すなわち内壁４ｂａと内壁４ｂｂとの距離となる。また、溝部４ｂは、最外周側に位置する貫通孔４ａａと一部が重なり、貫通孔４ａａよりも少し内周側に位置する貫通孔４ａｂと完全に重なり、貫通孔４ａｂよりもさらに内周側に位置する貫通孔４ａｃとは重ならないように形成されている。また、符号５ａは円筒部材５の内壁を示している。本実施形態１では、溝部４ｂの内壁４ｂａと円筒部材の内壁５ａが図７（ｃ）において一致しており、溝部４ｂの外径と円筒部材５の内径Ｄ２とが同じである。また、図７（ｂ）に示すように、貫通孔４ａを含め、複数の貫通孔４ａの直径はそれぞれｄである。また、図７（ｃ）では貫通孔４ａの外接円Ｃ１の位置も示してある。 This will be specifically described below. FIG. 7 is a schematic diagram showing the configuration of the multi-core fiber preform 10 after the insertion process. 7A is a top view as viewed from the end 4ca side, FIG. 7B is a partial cross-sectional view taken along the line AA in FIG. 7A, and FIG. 7C is a cross-sectional view taken along line B- in FIG. FIG. In FIG. 7A, reference numeral 4ba denotes an inner wall that defines the outer diameter of the groove 4b, and reference numeral 4bb denotes an inner wall that defines the inner diameter of the groove 4b. Therefore, the width w1 of the groove 4b is (outer diameter of the groove 4b−inner diameter of the groove 4b) / 2, that is, the distance between the inner wall 4ba and the inner wall 4bb. The groove 4b partially overlaps with the through hole 4aa located on the outermost peripheral side, completely overlaps with the through hole 4ab located slightly on the inner peripheral side of the through hole 4aa, and further on the inner peripheral side of the through hole 4ab It is formed so as not to overlap with the through-hole 4ac located at. Reference numeral 5 a denotes an inner wall of the cylindrical member 5. In the first embodiment, the inner wall 4ba of the groove 4b and the inner wall 5a of the cylindrical member coincide with each other in FIG. 7C, and the outer diameter of the groove 4b and the inner diameter D2 of the cylindrical member 5 are the same. Moreover, as shown in FIG.7 (b), the diameter of the several through-holes 4a including the through-hole 4a is each d. FIG. 7C also shows the position of the circumscribed circle C1 of the through hole 4a.

図７（ａ）、（ｃ）に示すように、円筒部材５の内径Ｄ２は、外接円Ｃ１の直径Ｄ１よりも小さい。したがって、内径Ｄ２と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−内径Ｄ２）／２の幅である幅Ｗ１の環状領域から、貫通孔４ａａと重なる部分を除いた領域（図７（ａ）において斜線を付した領域）の面積だけ、円筒部材５とクラッド母材４との接合面積が増加し、接合強度も増加する。 As shown in FIGS. 7A and 7C, the inner diameter D2 of the cylindrical member 5 is smaller than the diameter D1 of the circumscribed circle C1. Therefore, compared with the case where the inner diameter D2 and the diameter D1 are equal, a region obtained by removing a portion overlapping the through-hole 4aa from the annular region having the width W1 having a width of (diameter D1−inner diameter D2) / 2 (FIG. 7 ( The bonding area between the cylindrical member 5 and the clad base material 4 increases by the area of the hatched area in a), and the bonding strength also increases.

しかし、内径Ｄ２が直径Ｄ１よりも小さい場合、図７（ｂ）に示すように、貫通孔４ａａの一部が円筒部材５によって塞がれてしまう。これに対して、本実施形態１では、クラッド母材４には、貫通孔４ａａと円筒部材５の内部とを連通させる溝部４ｂが形成されている。また、貫通孔４ａａは溝部４ｂを介して、円筒部材５で塞がれていない貫通孔４ａｂとも連通している。その結果、溝部４ｂや貫通孔４ａｂを介して、貫通孔４ａａにおけるクラッド母材４と各コア母材６との隙間が効率的に吸引され、減圧される。また、その他の貫通孔４ａｂ、４ａｃは、円筒部材５で塞がれることなくクラッド母材４と各コア母材６との隙間が効率的に減圧される。このようにして、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 However, when the inner diameter D2 is smaller than the diameter D1, a part of the through hole 4aa is blocked by the cylindrical member 5 as shown in FIG. On the other hand, in the first embodiment, the clad base material 4 is formed with a groove 4b that allows the through hole 4aa and the inside of the cylindrical member 5 to communicate with each other. Further, the through hole 4aa communicates with the through hole 4ab not covered by the cylindrical member 5 through the groove 4b. As a result, the gap between the clad base material 4 and each core base material 6 in the through hole 4aa is efficiently sucked and decompressed through the groove 4b and the through hole 4ab. Further, the other through holes 4ab and 4ac are not blocked by the cylindrical member 5, and the gap between the clad base material 4 and each core base material 6 is efficiently decompressed. In this way, since all the gaps are efficiently depressurized, it is possible to suppress or prevent problems such as the presence of bubbles in the multi-core fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

なお、溝部４ｂについては、その外径が外接円Ｃ１の直径Ｄ１より小さく、かつその内径が円筒部材５の内径Ｄ２より小さいと、接合面積及び接合強度の増加と、効率的な減圧とを両立できるので好ましい。 In addition, about the groove part 4b, when the outer diameter is smaller than the diameter D1 of the circumscribed circle C1, and the inner diameter is smaller than the inner diameter D2 of the cylindrical member 5, an increase in the joining area and joining strength and efficient decompression are compatible. It is preferable because it is possible.

（変形例１）
つぎに、上記実施形態１に係る製造方法の変形例１〜６について説明する。まず、変形例１に係る製造方法について説明する。実施形態１の製造方法と変形例１に係る製造方法とでは、準備工程において準備するクラッド母材の構成が異なり、それ以外の接続工程、挿入工程、封止工程及び線引工程は同じである。 (Modification 1)
Next, modifications 1 to 6 of the manufacturing method according to the first embodiment will be described. First, the manufacturing method according to Modification 1 will be described. In the manufacturing method according to the first embodiment and the manufacturing method according to the first modification, the configuration of the clad base material prepared in the preparation process is different, and the other connection process, insertion process, sealing process, and drawing process are the same. .

図８は、変形例１における挿入工程後のマルチコアファイバ母材１０Ａの構成を示す模式図である。図８（ａ）は端部４ｃａ側からみた上面図、図８（ｂ）は図８（ａ）のＣ−Ｃ線一部断面図、図８（ｃ）は図８（ａ）のＤ−Ｄ線一部断面図である。図８に示すように、変形例１に係る製造方法において準備するクラッド母材４Ａでは、実施形態１に係る製造方法におけるクラッド母材４の溝部４ｂと比較して、連通構造を構成する凹部としての環状の溝部である溝部４Ａｂの外径及び内径が大きく形成されている。具体的には、溝部４Ａｂの外径は、円筒部材５の内径Ｄ２よりも大きい。ただし、（溝部４Ａｂの外径−溝部４Ａｂの内径）／２、すなわち溝部４Ａｂの内壁４Ａｂａと内壁４Ａｂｂとの距離である溝部４Ａｂの幅は、溝部４ｂと同じｗ１である。 FIG. 8 is a schematic diagram showing the configuration of the multi-core fiber preform 10A after the insertion step in the first modification. 8A is a top view seen from the end 4ca side, FIG. 8B is a partial cross-sectional view taken along the line C-C in FIG. 8A, and FIG. 8C is a cross-sectional view taken along the line D- in FIG. It is D line partial sectional drawing. As shown in FIG. 8, in the clad base material 4 A prepared in the manufacturing method according to the modified example 1, compared to the groove 4 b of the clad base material 4 in the manufacturing method according to the first embodiment, The outer and inner diameters of the groove portion 4Ab, which is an annular groove portion, are formed large. Specifically, the outer diameter of the groove 4Ab is larger than the inner diameter D2 of the cylindrical member 5. However, the width of the groove 4Ab, which is (the outer diameter of the groove 4Ab−the inner diameter of the groove 4Ab) / 2, that is, the distance between the inner wall 4Aba of the groove 4Ab and the inner wall 4Abb, is the same w1 as that of the groove 4b.

本変形例１においても、図８（ａ）、（ｃ）に示すように、円筒部材５の内径Ｄ２は、外接円Ｃ１の直径Ｄ１よりも小さい。したがって、内径Ｄ２と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−溝部４Ａｂの外径）／２の幅である幅Ｗ２の環状領域から、貫通孔４ａａと重なる部分を除いた領域（図８（ａ）において斜線を付した領域）の面積だけ、円筒部材５とクラッド母材４Ａとの接合面積が増加し、接合強度も増加する。したがって、クラッド母材４Ａを大型化できる。 Also in the first modification, as shown in FIGS. 8A and 8C, the inner diameter D2 of the cylindrical member 5 is smaller than the diameter D1 of the circumscribed circle C1. Therefore, compared with the case where the inner diameter D2 and the diameter D1 are equal, a region obtained by removing a portion overlapping the through-hole 4aa from the annular region having the width W2 (diameter D1—the outer diameter of the groove 4Ab) / 2. The bonding area between the cylindrical member 5 and the clad base material 4A increases by the area of the hatched area in FIG. 8A, and the bonding strength also increases. Therefore, the cladding base material 4A can be enlarged.

また、クラッド母材４Ａには、貫通孔４ａａと円筒部材５の内部とを連通させる溝部４Ａｂが形成されている。貫通孔４ａａは溝部４Ａｂを介して、円筒部材５で塞がれていない貫通孔４ａｂとも連通している。その結果、溝部４Ａｂや貫通孔４ａｂを介して、貫通孔４ａａにおけるクラッド母材４Ａと各コア母材６との隙間が効率的に吸引され、減圧される。また、実施形態１の場合と同様に、その他の貫通孔４ａｂ、４ａｃについても隙間が効率的に減圧される。このようにして、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 The clad base material 4 A has a groove 4 Ab that communicates the through hole 4 aa with the inside of the cylindrical member 5. The through hole 4aa communicates with the through hole 4ab that is not blocked by the cylindrical member 5 through the groove 4Ab. As a result, the gap between the clad base material 4A and the core base material 6 in the through hole 4aa is efficiently sucked and decompressed through the groove 4Ab and the through hole 4ab. Further, as in the case of the first embodiment, the gaps are efficiently decompressed in the other through holes 4ab and 4ac. In this way, since all the gaps are efficiently depressurized, it is possible to suppress or prevent problems such as the presence of bubbles in the multi-core fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

（変形例２）
実施形態１の製造方法と変形例２に係る製造方法とでは、準備工程において準備するクラッド母材の構成が異なり、それ以外の接続工程、挿入工程、封止工程及び線引工程は同じである。 (Modification 2)
In the manufacturing method according to the first embodiment and the manufacturing method according to the modified example 2, the configuration of the clad base material prepared in the preparation process is different, and the other connection process, insertion process, sealing process, and drawing process are the same. .

図９は、変形例２における挿入工程後のマルチコアファイバ母材１０Ｂの構成を示す模式図である。図９（ａ）は端部４ｃａ側からみた上面図、図９（ｂ）は図９（ａ）のＥ−Ｅ線一部断面図、図９（ｃ）は図９（ａ）のＦ−Ｆ線一部断面図である。図９に示すように、変形例２に係る製造方法において準備するクラッド母材４Ｂでは、実施形態１に係る製造方法におけるクラッド母材４の溝部４ｂと比較して、連通構造を構成する凹部としての環状の溝部である溝部４Ｂｂの外径が小さく、かつ内径が大きく形成されている。具体的には、溝部４Ｂｂの外径は、円筒部材５の内径Ｄ２よりも小さい。さらには、図９（ａ）に示すように溝部４Ｂｂの内壁４Ｂｂａ、４Ｂｂｂ間の距離である幅ｗ２が、貫通孔４ａａの直径ｄよりも小さくなっている（図９（ｂ）も参照）。 FIG. 9 is a schematic diagram showing the configuration of the multi-core fiber preform 10B after the insertion step in Modification 2. 9A is a top view seen from the end 4ca side, FIG. 9B is a partial cross-sectional view taken along the line EE of FIG. 9A, and FIG. 9C is a cross-sectional view taken along line F- of FIG. It is F line partial sectional drawing. As shown in FIG. 9, in the clad base material 4B prepared in the manufacturing method according to the modified example 2, compared to the groove 4b of the clad base material 4 in the manufacturing method according to the first embodiment, The groove portion 4Bb, which is an annular groove portion, has a small outer diameter and a large inner diameter. Specifically, the outer diameter of the groove 4Bb is smaller than the inner diameter D2 of the cylindrical member 5. Furthermore, as shown in FIG. 9A, the width w2 that is the distance between the inner walls 4Bba and 4Bbb of the groove 4Bb is smaller than the diameter d of the through hole 4aa (see also FIG. 9B).

本変形例２においても、図９（ａ）、（ｃ）に示すように、円筒部材５の内径Ｄ２は、外接円Ｃ１の直径Ｄ１よりも小さい。したがって、内径Ｄ２と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−内径Ｄ２）／２の幅である幅Ｗ３の環状領域から、貫通孔４ａａと重なる部分を除いた領域（図９（ａ）において斜線を付した領域）の面積だけ、円筒部材５とクラッド母材４Ｂとの接合面積が増加し、接合強度も増加する。したがって、クラッド母材４Ｂを大型化できる。 Also in the second modification, as shown in FIGS. 9A and 9C, the inner diameter D2 of the cylindrical member 5 is smaller than the diameter D1 of the circumscribed circle C1. Therefore, compared with the case where the inner diameter D2 and the diameter D1 are equal, a region obtained by removing a portion overlapping the through-hole 4aa from the annular region having the width W3 having a width of (diameter D1−inner diameter D2) / 2 (FIG. 9 ( The bonding area between the cylindrical member 5 and the clad base material 4B increases by the area of the hatched area in a), and the bonding strength also increases. Therefore, the clad base material 4B can be enlarged.

また、クラッド母材４Ｂには、貫通孔４ａａと円筒部材５の内部とを連通させる溝部４Ｂｂが形成されている。また、貫通孔４ａａは溝部４Ｂｂを介して、円筒部材５で塞がれていない貫通孔４ａｂとも連通している。その結果、溝部４Ｂｂや貫通孔４ａｂを介して、貫通孔４ａａにおけるクラッド母材４Ｂと各コア母材６との隙間が効率的に吸引され、減圧される。また、実施形態１の場合と同様に、その他の貫通孔４ａｂ、４ａｃについても隙間が効率的に吸引される。このようにして、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 The clad base material 4B is formed with a groove 4Bb that allows the through hole 4aa and the inside of the cylindrical member 5 to communicate with each other. Further, the through hole 4aa communicates with the through hole 4ab not covered by the cylindrical member 5 through the groove 4Bb. As a result, the gap between the clad base material 4B and each core base material 6 in the through hole 4aa is efficiently sucked and depressurized through the groove 4Bb and the through hole 4ab. Further, as in the case of the first embodiment, the gaps are also efficiently sucked in the other through holes 4ab and 4ac. In this way, since all the gaps are efficiently depressurized, it is possible to suppress or prevent problems such as the presence of bubbles in the multi-core fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

（変形例３）
実施形態１の製造方法と変形例３に係る製造方法とでは、準備工程において準備するクラッド母材の構成が異なり、それ以外の接続工程、挿入工程、封止工程及び線引工程は同じである。 (Modification 3)
In the manufacturing method according to the first embodiment and the manufacturing method according to the modified example 3, the configuration of the clad base material prepared in the preparation process is different, and the other connection process, insertion process, sealing process, and drawing process are the same. .

図１０は、変形例３における挿入工程後のマルチコアファイバ母材１０Ｃの構成を示す模式図である。図１０（ａ）は端部４ｃａ側からみた上面図、図１０（ｂ）は図１０（ａ）のＧ−Ｇ線一部断面図、図１０（ｃ）は図１０（ａ）のＨ−Ｈ線一部断面図である。図１０に示すように、変形例３に係る製造方法において準備するクラッド母材４Ｃでは、実施形態１に係る製造方法におけるクラッド母材４と比較して、端部４ｃａにおいて溝部４ｂの代わりに凹部４Ｃｂが形成されている。凹部４Ｃｂは、連通構造を構成する凹部であって、上面視で円状であり、直径が深さ方向にわたって略一定の凹部である。凹部４Ｃｂの直径は本変形例３では円筒部材５の内径Ｄ２と同じであるが、凹部４Ｃｂの直径は外接円Ｃ１の直径Ｄ１より小さく、貫通孔４ａａと連通できる程度の直径であることが好ましい。なお、凹部４Ｃｂは端部４ｃａに対する機械的加工等で形成することができる。 FIG. 10 is a schematic diagram showing the configuration of the multi-core fiber preform 10C after the insertion step in Modification 3. 10A is a top view seen from the end 4ca side, FIG. 10B is a partial cross-sectional view taken along the line GG in FIG. 10A, and FIG. 10C is a cross-sectional view taken along line H- in FIG. FIG. As shown in FIG. 10, in the clad base material 4C prepared in the manufacturing method according to the modified example 3, compared to the clad base material 4 in the manufacturing method according to the first embodiment, a concave portion is provided instead of the groove portion 4b at the end 4ca. 4Cb is formed. The recess 4Cb is a recess that constitutes a communication structure, is circular when viewed from above, and has a substantially constant diameter across the depth direction. The diameter of the recess 4Cb is the same as the inner diameter D2 of the cylindrical member 5 in the third modification, but the diameter of the recess 4Cb is preferably smaller than the diameter D1 of the circumscribed circle C1 and can communicate with the through hole 4aa. . The recess 4Cb can be formed by mechanical processing or the like on the end 4ca.

本変形例３においても、図１０（ａ）、（ｃ）に示すように、円筒部材５の内径Ｄ２は、外接円Ｃ１の直径Ｄ１よりも小さい。したがって、内径Ｄ２と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−内径Ｄ２）／２の幅である幅Ｗ４の環状領域から、貫通孔４ａａと重なる部分を除いた領域（図１０（ａ）において斜線を付した領域）の面積だけ、円筒部材５とクラッド母材４Ｃとの接合面積が増加し、接合強度も増加する。したがって、クラッド母材４Ｃを大型化できる。 Also in the third modification, as shown in FIGS. 10A and 10C, the inner diameter D2 of the cylindrical member 5 is smaller than the diameter D1 of the circumscribed circle C1. Therefore, compared to the case where the inner diameter D2 and the diameter D1 are equal, a region obtained by removing a portion overlapping the through-hole 4aa from the annular region having a width W4 having a width of (diameter D1−inner diameter D2) / 2 (FIG. 10 ( The joining area between the cylindrical member 5 and the clad base material 4C increases by the area of the hatched area in a), and the joining strength also increases. Therefore, the cladding base material 4C can be enlarged.

また、クラッド母材４Ｃには、貫通孔４ａａと円筒部材５の内部とを連通させる凹部４Ｃｂが形成されている。また、貫通孔４ａａは凹部４Ｃｂを介して、円筒部材５で塞がれていない貫通孔４ａｂ、４ａｃとも連通している。その結果、凹部４Ｃｂや貫通孔４ａｂ、４ａｃを介して、貫通孔４ａａにおけるクラッド母材４Ｃと各コア母材６との隙間が効率的に吸引され、減圧される。また、実施形態１の場合と同様に、その他の貫通孔４ａｂ、４ａｃについても隙間が効率的に吸引される。このようにして、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 The clad base material 4C has a recess 4Cb that allows the through hole 4aa and the inside of the cylindrical member 5 to communicate with each other. Further, the through hole 4aa communicates with the through holes 4ab and 4ac not covered by the cylindrical member 5 through the recess 4Cb. As a result, the gap between the clad base material 4C and each core base material 6 in the through hole 4aa is efficiently sucked and depressurized through the recess 4Cb and the through holes 4ab and 4ac. Further, as in the case of the first embodiment, the gaps are also efficiently sucked in the other through holes 4ab and 4ac. In this way, since all the gaps are efficiently depressurized, it is possible to suppress or prevent problems such as the presence of bubbles in the multi-core fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

（変形例４）
実施形態１の製造方法と変形例４に係る製造方法とでは、準備工程において準備するクラッド母材の構成及び円筒部材の構成が異なり、それ以外の接続工程、挿入工程、封止工程及び線引工程は同じである。 (Modification 4)
The manufacturing method according to Embodiment 1 and the manufacturing method according to Modification 4 are different in the configuration of the clad base material and the cylindrical member prepared in the preparation step, and the other connection step, insertion step, sealing step, and drawing. The process is the same.

図１１は、変形例４における挿入工程後のマルチコアファイバ母材１０Ｄの構成を示す模式図である。図１１（ａ）は端部４ｃａ側からみた上面図、図１１（ｂ）は図１１（ａ）のＩ−Ｉ線一部断面図である。図１１に示すように、変形例４に係る製造方法において準備する円筒部材５Ｄは、内径Ｄ３が円筒部材５の内径Ｄ２より小さい点で異なるが、外径及び構成材料は円筒部材５と同じものである。変形例４に係る製造方法において準備するクラッド母材４Ｄでは、実施形態１に係る製造方法におけるクラッド母材４と比較して、端部４ｃａにおいて溝部４ｂの代わりに、連通構造を構成する凹部としての溝部である複数の連通溝部４Ｄｂが形成されている。 FIG. 11 is a schematic diagram showing the configuration of the multi-core fiber preform 10D after the insertion step in Modification 4. 11A is a top view seen from the end 4ca side, and FIG. 11B is a partial cross-sectional view taken along the line II of FIG. 11A. As shown in FIG. 11, the cylindrical member 5 D prepared in the manufacturing method according to the modification 4 is different in that the inner diameter D 3 is smaller than the inner diameter D 2 of the cylindrical member 5, but the outer diameter and the constituent material are the same as the cylindrical member 5. It is. In the clad base material 4D prepared in the manufacturing method according to the modified example 4, as compared with the clad base material 4 in the manufacturing method according to the first embodiment, a concave portion constituting the communication structure is used instead of the groove portion 4b in the end portion 4ca. A plurality of communication groove portions 4Db, which are the groove portions, are formed.

連通溝部４Ｄｂは、貫通孔４ａのうち、上面視で円筒部材５Ｄと少なくとも一部が重なる貫通孔と、上面視で円筒部材５Ｄと重ならない貫通孔と、を連通する溝である。具体的には、連通溝部４Ｄｂは、図１１（ａ）に示すように、円筒部材５Ｄと完全に重なる貫通孔４ａａと、円筒部材５Ｄと重ならない貫通孔４ａｃと、を連通する溝、又は、円筒部材５Ｄと一部が重なる貫通孔４ａｂと、円筒部材５Ｄと重ならない貫通孔４ａｃと、を連通する溝である。なお、連通溝部４Ｄｂは端部４ｃａに対する機械的加工等で形成することができる。 The communication groove portion 4Db is a groove that communicates between a through hole in the through hole 4a that at least partially overlaps the cylindrical member 5D in a top view and a through hole that does not overlap the cylindrical member 5D in a top view. Specifically, as shown in FIG. 11A, the communication groove 4Db is a groove that connects the through hole 4aa that completely overlaps the cylindrical member 5D and the through hole 4ac that does not overlap the cylindrical member 5D, or This is a groove that communicates the through hole 4ab that partially overlaps the cylindrical member 5D and the through hole 4ac that does not overlap the cylindrical member 5D. The communication groove 4Db can be formed by mechanical processing or the like on the end 4ca.

本変形例４においても、図１１（ａ）、（ｂ）に示すように、円筒部材５Ｄの内径Ｄ３は、外接円Ｃ１の直径Ｄ１よりも小さい。したがって、内径Ｄ３と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−内径Ｄ３）／２の幅である幅Ｗ５の環状領域から、貫通孔４ａａ、４ａｂと重なる部分を除いた領域（図１１（ａ）において斜線を付した領域）の面積だけ、円筒部材５Ｄとクラッド母材４Ｄとの接合面積が増加し、接合強度も増加する。したがって、クラッド母材４Ｄを大型化できる。 Also in the fourth modification, as shown in FIGS. 11A and 11B, the inner diameter D3 of the cylindrical member 5D is smaller than the diameter D1 of the circumscribed circle C1. Therefore, compared to the case where the inner diameter D3 and the diameter D1 are equal, a region obtained by removing a portion overlapping the through holes 4aa and 4ab from the annular region having the width W5 having a width of (diameter D1−inner diameter D3) / 2 (see FIG. 11 (a), the joining area between the cylindrical member 5D and the cladding base material 4D is increased by the area of the hatched area), and the joining strength is also increased. Therefore, the cladding base material 4D can be enlarged.

また、クラッド母材４Ｄに形成された連通溝部４Ｄｂは、円筒部材５Ｄによって完全に塞がれる貫通孔４ａａと貫通孔４ａｃとを連通している、又は、円筒部材５Ｄによって一部が塞がれる貫通孔４ａｂと貫通孔４ａｃとを連通している。その結果、図１１（ｂ）に貫通孔４ａａに関して示すように、矢印Ｙ２のように、連通溝部４Ｄｂ及び貫通孔４ａｃを介して、貫通孔４ａａにおけるクラッド母材４Ｄと各コア母材６との隙間が効率的に吸引され、減圧される。同様にして、連通溝部４Ｄｂ及び貫通孔４ａｃを介して、貫通孔４ａｂにおけるクラッド母材４Ｄと各コア母材６との隙間も効率的に吸引され、減圧される。また、実施形態１の場合と同様に、貫通孔４ａｃについても隙間が効率的に吸引される。このようにして、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 Further, the communication groove 4Db formed in the clad base material 4D communicates the through hole 4aa and the through hole 4ac that are completely blocked by the cylindrical member 5D, or is partially blocked by the cylindrical member 5D. The through hole 4ab and the through hole 4ac communicate with each other. As a result, as shown with respect to the through hole 4aa in FIG. 11B, as shown by the arrow Y2, the clad base material 4D and the core base material 6 in the through hole 4aa are connected via the communication groove 4Db and the through hole 4ac. The gap is efficiently sucked and depressurized. Similarly, the gap between the cladding base material 4D and each core base material 6 in the through hole 4ab is also efficiently sucked and decompressed through the communication groove 4Db and the through hole 4ac. Further, as in the case of the first embodiment, the gap is also efficiently sucked in the through hole 4ac. In this way, since all the gaps are efficiently depressurized, it is possible to suppress or prevent problems such as the presence of bubbles in the multi-core fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

（変形例５、６）
実施形態１の製造方法と変形例５、６に係る製造方法とでは、準備工程において準備するクラッド母材の構成及び円筒部材の構成が異なり、それ以外の接続工程、挿入工程、封止工程及び線引工程は同じである。 (Modifications 5 and 6)
In the manufacturing method according to the first embodiment and the manufacturing methods according to Modifications 5 and 6, the configuration of the cladding base material and the configuration of the cylindrical member that are prepared in the preparation step are different, and the other connection step, insertion step, sealing step, and The drawing process is the same.

図１２は、変形例５、６における挿入工程後のマルチコアファイバ母材の構成を示す模式図である。図１２（ａ）は変形例５のマルチコアファイバ母材１０Ｅについて、図１２（ｂ）は変形例６のマルチコアファイバ母材１０Ｆについて、クラッド母材４の中心軸と貫通孔４ａａの中心軸とを通る面における断面図を示す。変形例５、６は、クラッド母材の一方の端部側に連通部が設けられており、連通構造がその連通部により形成されている点で共通している。 FIG. 12 is a schematic diagram showing the configuration of the multi-core fiber preform after the insertion step in Modifications 5 and 6. 12A shows the multi-core fiber preform 10E of Modification 5 and FIG. 12B shows the center axis of the clad preform 4 and the center axis of the through hole 4aa for the multi-core fiber preform 10F of Modification 6. Sectional drawing in the surface which passes is shown. Modifications 5 and 6 are common in that a communication portion is provided on one end side of the clad base material and a communication structure is formed by the communication portion.

はじめに、変形例５について説明する。図１２（ａ）に示すように、変形例５に係る製造方法において準備する円筒部材５Ｅは、内径Ｄ４が円筒部材５の内径Ｄ２より小さく、外径が円筒部材５の外径よりも大きい点で異なるが、構成材料は円筒部材５と同じものである。変形例５に係る製造方法において準備するクラッド母材４Ｅは、実施形態１に係る製造方法におけるクラッド母材４の一方の端部４ｃａ側に、外径が円柱状の連通部４Ｅｄを設けたものである。連通部４Ｅｄは、たとえばクラッド母材４と同一のガラス材料からなるガラス体を機械加工して作製したものをクラッド母材４に溶着接続することで設けることができる。また、円筒部材５Ｅはクラッド母材４Ｅの一方の端部である端部４Ｅｃａに接続される。ここで、連通部４Ｅｄの外径はクラッド母材４の外径よりも大きい。また円筒部材５Ｅの外径は連通部４Ｅｄの外径と同じである。 First, Modification Example 5 will be described. As shown in FIG. 12A, the cylindrical member 5E prepared in the manufacturing method according to the modified example 5 has an inner diameter D4 smaller than the inner diameter D2 of the cylindrical member 5 and an outer diameter larger than the outer diameter of the cylindrical member 5. However, the constituent material is the same as that of the cylindrical member 5. The clad base material 4E prepared in the manufacturing method according to the modified example 5 is provided with a communication portion 4Ed having an outer diameter of a columnar shape on the one end 4ca side of the clad base material 4 in the manufacturing method according to the first embodiment. It is. The communication part 4Ed can be provided by welding and connecting a glass body made of the same glass material as that of the clad base material 4 to the clad base material 4, for example. The cylindrical member 5E is connected to an end portion 4Eca that is one end portion of the clad base material 4E. Here, the outer diameter of the communication portion 4 Ed is larger than the outer diameter of the clad base material 4. The outer diameter of the cylindrical member 5E is the same as the outer diameter of the communication portion 4Ed.

連通部４Ｅｄにおいては、連通構造は、開口部４Ｅｄａと複数の連通孔４Ｅｄｂとにより構成されている。開口部４Ｅｄａは、円筒部材５Ｅの内部に対して開放されるように設けられている。複数の連通孔４Ｅｄｂは、それぞれの一端が貫通孔４ａａ、図１２（ａ）では不図示の貫通孔４ａｂ、又は貫通孔４ａｃとそれぞれ接続され、それぞれの他端が開口部４Ｅｄａに接続されている。連通孔４Ｅｄｂは、端部４Ｅｃａに近づく程、互いの距離が小さくなる形状とされており、やがて合流して開口部４Ｅｄａに接続している。開口部４Ｅｄａの形状は本変形例５では円形であるが、特に限定はされない。なお、連通部４Ｅｄとクラッド母材４との接合面積は、クラッド母材４の端部４ｃａにおいて貫通孔４ａａ、４ａｂ、４ａｃを除いた部分の面積となる。したがって、連通部４Ｅｄとクラッド母材４との接合面積及び接合強度は十分に大きい。 In the communication portion 4Ed, the communication structure includes an opening 4Eda and a plurality of communication holes 4Edb. The opening 4Eda is provided so as to be open to the inside of the cylindrical member 5E. One end of each of the plurality of communication holes 4Edb is connected to the through-hole 4aa, the not-shown through-hole 4ab or the through-hole 4ac in FIG. 12A, and the other end is connected to the opening 4Eda. . The communication holes 4Edb are shaped so that the distance from each other decreases as they approach the end 4Eca, and eventually merge and connect to the opening 4Eda. The shape of the opening 4Eda is circular in the fifth modification, but is not particularly limited. The junction area between the communication portion 4Ed and the clad base material 4 is the area of the end portion 4ca of the clad base material 4 excluding the through holes 4aa, 4ab, and 4ac. Accordingly, the bonding area and bonding strength between the communication portion 4Ed and the clad base material 4 are sufficiently large.

本変形例５においても、図１２（ａ）に示すように、円筒部材５Ｅの内径Ｄ４は、外接円Ｃ１の直径Ｄ１よりも小さい。さらに、連通部４Ｅｄ及び円筒部材５Ｅの外径はクラッド母材４の外径よりも大きい。したがって、内径Ｄ４と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−内径Ｄ４）／２の幅の環状領域の面積と、（連通部４Ｅｄの端部４Ｅｃａにおける外径−クラッド母材４の外径）／２の幅の環状領域の面積とを加算した分だけ、円筒部材５Ｅとクラッド母材４Ｅとの接合面積が増加し、接合強度も増加する。また、上述したように、連通部４Ｅｄとクラッド母材４との接合面積及び接合強度は十分に大きい。したがって、クラッド母材４Ｅを大型化できる。 Also in this modification 5, as shown to Fig.12 (a), the internal diameter D4 of the cylindrical member 5E is smaller than the diameter D1 of the circumscribed circle C1. Furthermore, the outer diameters of the communication portion 4Ed and the cylindrical member 5E are larger than the outer diameter of the clad base material 4. Therefore, compared with the case where the inner diameter D4 and the diameter D1 are equal, the area of the annular region having a width of (diameter D1−inner diameter D4) / 2 and the outer diameter−cladding base material 4 at the end 4Eca of the communication portion 4Ed. ) / 2, and the area of the annular region having a width of ½, the joining area between the cylindrical member 5E and the clad base material 4E increases, and the joining strength also increases. Further, as described above, the bonding area and the bonding strength between the communication portion 4Ed and the clad base material 4 are sufficiently large. Therefore, the cladding base material 4E can be enlarged.

また、図１２（ａ）からもわかるように、上面視で円筒部材５Ｅと貫通孔４ａａとは完全に重なるが、貫通孔４ａａと接続された連通孔４Ｅｄｂと開口部４Ｅｄａとを介して、貫通孔４ａａにおけるクラッド母材４Ｅと各コア母材６との隙間が効率的に吸引され、減圧される。また、その他の貫通孔４ａｂ、４ａｃについても連通孔４Ｅｄｂと開口部４Ｅｄａとを介して隙間が効率的に吸引される。このような構成により、いずれの貫通孔も塞がれず、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 As can be seen from FIG. 12 (a), the cylindrical member 5E and the through hole 4aa completely overlap each other when viewed from above, but through the communication hole 4Edb and the opening 4Eda connected to the through hole 4aa. The gaps between the clad base material 4E and the core base material 6 in the holes 4aa are efficiently sucked and decompressed. Further, with respect to the other through holes 4ab and 4ac, the gap is efficiently sucked through the communication hole 4Edb and the opening 4Eda. With such a configuration, none of the through holes are blocked, and all the gaps are efficiently decompressed. Therefore, it is possible to suppress or prevent problems such as the presence of bubbles in the multicore fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

なお、本変形例５では、複数の連通孔４Ｅｄｂが合流して１つの開口部４Ｅｄａに接続しているが、複数の連通孔４Ｅｄｂが合流せずに、円筒部材５Ｅの内部に対して開放されるように各連通孔４Ｅｄｂに対して個別に設けられた開口部に接続していてもよい。さらには、開口部４Ｅｄａ及び連通孔４Ｅｄｂは、各貫通孔４ａｂ、４ａｃが円筒部材５Ｅの内部に対して、円筒部材５Ｅで塞がれない状態で開放されるように構成されていれば、その形状は特に限定はされない。 In the fifth modification, the plurality of communication holes 4Edb merge and connect to one opening 4Eda, but the plurality of communication holes 4Edb do not merge and are opened to the inside of the cylindrical member 5E. In this way, the connection holes 4Edb may be connected to openings provided individually. Furthermore, if the opening 4Eda and the communication hole 4Edb are configured so that each through-hole 4ab, 4ac is opened to the inside of the cylindrical member 5E without being blocked by the cylindrical member 5E, The shape is not particularly limited.

つぎに、変形例６について説明する。図１２（ｂ）に示すように、変形例６に係る製造方法において準備する円筒部材５Ｆは、内径Ｄ５が円筒部材５の内径Ｄ２より小さく、外径が円筒部材５の外径よりも大きい点で異なるが、構成材料は円筒部材５と同じものである。変形例６に係る製造方法において準備するクラッド母材４Ｆは、実施形態１に係る製造方法におけるクラッド母材４の一方の端部側に、外径が円柱状の連通部４Ｆｄを設けたものである。連通部４Ｆｄは、たとえばクラッド母材４と同一のガラス材料からなるガラス体を機械加工して作製したものをクラッド母材４に溶着接続することで設けることができる。また、円筒部材５Ｆはクラッド母材４Ｆの一方の端部である端部４Ｆｃａに接続される。ここで、連通部４Ｆｄの外径はクラッド母材４の外径よりも大きい。また円筒部材５Ｆの外径は連通部４Ｆｄの外径と同じである。 Next, Modification 6 will be described. As illustrated in FIG. 12B, the cylindrical member 5 F prepared in the manufacturing method according to the modified example 6 has an inner diameter D 5 smaller than the inner diameter D 2 of the cylindrical member 5 and an outer diameter larger than the outer diameter of the cylindrical member 5. However, the constituent material is the same as that of the cylindrical member 5. The cladding base material 4F prepared in the manufacturing method according to the modified example 6 is provided with a communication portion 4Fd having an outer diameter of a columnar shape on one end side of the cladding base material 4 in the manufacturing method according to the first embodiment. is there. The communicating portion 4Fd can be provided by welding and connecting a glass body made of the same glass material as that of the clad base material 4 to the clad base material 4, for example. The cylindrical member 5F is connected to an end 4Fca that is one end of the clad base material 4F. Here, the outer diameter of the communication portion 4Fd is larger than the outer diameter of the clad base material 4. The outer diameter of the cylindrical member 5F is the same as the outer diameter of the communication portion 4Fd.

連通部４Ｆｄにおいては、連通構造は、開口部４Ｆｄａと連通空間４Ｆｄｂとにより構成されている。開口部４Ｆｄａは、円筒部材５Ｆの内部に対して開放されるように設けられている。連通空間４Ｆｄｂは、貫通孔４ａａ、図１２（ｂ）では不図示の貫通孔４ａｂ、及び貫通孔４ａｃと開口部４Ｆｄａとを一括して連通するように構成されている。開口部４Ｆｄａの形状は本変形例６では円形であるが、特に限定はされない。また、連通空間４Ｆｄｂの形状は本変形例６では円柱形状であるが、特に限定はされない。連通空間４Ｆｄｂの直径は、連通部４Ｆｄによって最外周側の貫通孔４ａａが塞がれないように、外接円Ｃ１の直径Ｄ１と同じ程度であることが好ましい。なお、連通部４Ｆｄとクラッド母材４との接合面積は、クラッド母材４の端部４ｃａにおいて貫通孔４ａａ、４ａｂ、４ａｃを除いた部分の面積となる。したがって、連通部４Ｆｄとクラッド母材４との接合面積及び接合強度は十分に大きい。 In the communication part 4Fd, the communication structure is constituted by an opening 4Fda and a communication space 4Fdb. The opening 4Fda is provided so as to be open to the inside of the cylindrical member 5F. The communication space 4Fdb is configured to collectively communicate the through hole 4aa, the through hole 4ab (not shown in FIG. 12B), and the through hole 4ac and the opening 4Fda. The shape of the opening 4Fda is circular in the sixth modification, but is not particularly limited. In addition, the shape of the communication space 4Fdb is a cylindrical shape in the sixth modification, but is not particularly limited. The diameter of the communication space 4Fdb is preferably about the same as the diameter D1 of the circumscribed circle C1 so that the through hole 4aa on the outermost peripheral side is not blocked by the communication portion 4Fd. The junction area between the communication portion 4Fd and the clad base material 4 is the area of the end portion 4ca of the clad base material 4 excluding the through holes 4aa, 4ab, and 4ac. Therefore, the bonding area and bonding strength between the communication portion 4Fd and the clad base material 4 are sufficiently large.

本変形例６においても、図１２（ｂ）に示すように、円筒部材５Ｆの内径Ｄ５は、外接円Ｃ１の直径Ｄ１よりも小さい。さらに、連通部４Ｆｄ及び円筒部材５Ｆの外径はクラッド母材４の外径よりも大きい。したがって、内径Ｄ５と直径Ｄ１とが等しい場合と比較して、（直径Ｄ１−内径Ｄ５）／２の幅の環状領域の面積と、（連通部４Ｆｄの端部４Ｆｃａにおける外径−クラッド母材４の外径）／２の幅の環状領域の面積とを加算した分だけ、円筒部材５Ｆとクラッド母材４Ｆとの接合面積が増加し、接合強度も増加する。また、上述したように、連通部４Ｆｄとクラッド母材４との接合面積及び接合強度は十分に大きい。したがって、クラッド母材４Ｆを大型化できる。 Also in the sixth modification, as shown in FIG. 12B, the inner diameter D5 of the cylindrical member 5F is smaller than the diameter D1 of the circumscribed circle C1. Furthermore, the outer diameters of the communication portion 4Fd and the cylindrical member 5F are larger than the outer diameter of the clad base material 4. Therefore, compared with the case where the inner diameter D5 and the diameter D1 are equal, the area of the annular region having a width of (diameter D1−inner diameter D5) / 2 and the outer diameter-cladding base material 4 at the end portion 4Fca of the communication portion 4Fd. The outer area of the annular region having a width of / 2 is added to the area of the annular region, the bonding area between the cylindrical member 5F and the clad base material 4F increases, and the bonding strength also increases. Further, as described above, the bonding area and the bonding strength between the communication portion 4Fd and the clad base material 4 are sufficiently large. Therefore, the clad base material 4F can be enlarged.

また、図１２（ｂ）からもわかるように、上面視で円筒部材５Ｆと貫通孔４ａａとは完全に重なるが、連通空間４Ｆｄｂと開口部４Ｆｄａとを介して貫通孔４ａａ、４ａｂ、４ａｃにおけるクラッド母材４Ｆと各コア母材６との隙間が一括して効率的に吸引され、減圧される。このような構成により、いずれの貫通孔も塞がれず、全ての隙間が効率的に減圧されるので、線引き後にマルチコアファイバ１内に気泡が存在する等の不具合を抑制又は防止できる。さらに、隙間が効率的に減圧されることにより、線引き時の母材破損、変形等抑制又は防止にも寄与する。 As can be seen from FIG. 12B, the cylindrical member 5F and the through hole 4aa completely overlap with each other when viewed from above, but the cladding in the through holes 4aa, 4ab, and 4ac through the communication space 4Fdb and the opening 4Fda. The gaps between the base material 4F and each core base material 6 are efficiently sucked together and decompressed. With such a configuration, none of the through holes are blocked, and all the gaps are efficiently decompressed. Therefore, it is possible to suppress or prevent problems such as the presence of bubbles in the multicore fiber 1 after drawing. Furthermore, since the gap is efficiently decompressed, it contributes to suppression or prevention of damage to the base material, deformation, and the like during drawing.

なお、上記実施形態及びその変形例における溝の内外径、凹部の直径、及び円筒部材の内径、連通部における開口部、連通孔及び連通空間の形状、サイズは、クラッド母材の重量及び貫通孔の直径、数、及び配列等を考慮して、円筒部材とクラッド母材との間で所望の接合強度が得られ、かつ隙間に対する吸引、減圧が所望の効率で実現できるように適宜設定すればよい。吸引、減圧の効率は、たとえば、図６における吸引装置１０２ｃの動作開始時刻から吸引路１０２ｂ内が所望の気圧まで減圧される時刻までの時間を指標とすることができる。 Note that the inner and outer diameters of the grooves, the diameter of the recesses, the inner diameter of the cylindrical member, the shape of the opening in the communication part, the shape of the communication hole and the communication space, and the size in the above embodiment and its modifications are the weight of the clad base material and the through hole. In consideration of the diameter, number, arrangement, and the like, it is possible to appropriately set so that a desired bonding strength can be obtained between the cylindrical member and the clad base material, and suction and decompression to the gap can be realized with a desired efficiency. Good. The efficiency of suction and decompression can be, for example, the time from the operation start time of the suction device 102c in FIG. 6 to the time when the suction path 102b is decompressed to a desired pressure.

また、上記実施形態及びその変形例では、コア部が正方格子状に配列しているが、本発明はコア部の配列にかかわらず適用できる。たとえば、本発明は、コア部が円状、同心円状、三角格子状などの規則的な配列、又は不規則な配列をしているマルチコアファイバ母材又はマルチコアファイバを製造する際にも適用できる。また、上記実施形態及びその変形例では、コア部の数は２１個であるが、本発明はコア部の数にかかわらず適用できる。たとえば、本発明は、コア部の数が４、５、６、７、８、９、１２、１６、１９、２４、２５・・・等公知のマルチコアファイバ母材又はマルチコアファイバを製造する際にも適用できる（当然、例示したコア部の数に限定されるものではない。）。 Moreover, in the said embodiment and its modification, although the core part is arranged in square lattice shape, this invention is applicable irrespective of the arrangement | sequence of a core part. For example, the present invention can also be applied to the production of a multicore fiber preform or a multicore fiber in which the core portions are regularly arranged in a circular shape, a concentric shape, a triangular lattice shape, or an irregular shape. Moreover, in the said embodiment and its modification, although the number of core parts is 21, this invention is applicable regardless of the number of core parts. For example, in the present invention, the number of core portions is 4, 5, 6, 7, 8, 9, 12, 16, 19, 24, 25. (Of course, it is not limited to the number of core parts illustrated).

また、上記実施形態及びその変形例により本発明が限定されるものではない。上述した各構成要素を適宜組み合わせて構成したものも本発明に含まれる。また、さらなる効果や変形例は、当業者によって容易に導き出すことができる。よって、本発明のより広範な態様は、上記の実施形態に限定されるものではなく、様々な変更が可能である。 In addition, the present invention is not limited by the above-described embodiment and its modifications. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

１被覆されたマルチコアファイバ
２マルチコアファイバ
２ａ、２ａａ、２ａｂ、２ａｃコア部
２ｂクラッド部
３被覆
４、４Ａ、４Ｂ、４Ｃ、４Ｄ、４Ｅ、４Ｆクラッド母材
４ｂ、４Ａｂ、４Ｂｂ溝部
４ｂａ、４ｂｂ、４Ａｂａ、４Ａｂｂ、４Ｂｂａ、４Ｂｂｂ、５ａ内壁
４Ｃｂ凹部
４Ｄｂ連通溝部
４Ｅｄ、４Ｆｄ連通部
４ｃａ、４ｃｂ、４Ｅｃａ、４Ｆｃａ端部
４Ｅｄａ、４Ｆｄａ開口部
４Ｅｄｂ連通孔
４Ｆｄｂ連通空間
４ａ、４ａａ、４ａｂ、４ａｃ貫通孔
４´ ガラス材
５、５Ｄ、５Ｅ、５Ｆ円筒部材
６コア母材
１０、１０Ａ、１０Ｂ、１０Ｃ、１０Ｄ、１０Ｅ、１０Ｆマルチコアファイバ母材
１００線引装置
１０１線引加熱炉
１０１ａヒータ
１０２吸引機構
１０２ａ吸引用コネクタ
１０２ｂ吸引路
１０２ｃ吸引装置
１０３外径測定器
１０４被覆樹脂塗布装置
１０５樹脂硬化装置
１０６キャプスタンローラ
１０７ガイドロール
Ｃ制御器
Ｃ１外接円
Ｙ１、Ｙ２矢印 DESCRIPTION OF SYMBOLS 1 Coated multi-core fiber 2 Multi-core fiber 2a, 2aa, 2ab, 2ac Core part 2b Clad part 3 Coated 4, 4A, 4B, 4C, 4D, 4E, 4F Clad base material 4b, 4Ab, 4Bb Groove part 4ba, 4bb, 4Aba 4Abb, 4Bba, 4Bbb, 5a Inner wall 4Cb Recess 4Db Communication groove 4Ed, 4Fd Communication part 4ca, 4cb, 4Eca, 4Fca End 4Eda, 4Fda Opening 4Edb Communication hole 4Fdb Communication space 4a, 4aa, 4ab, 4ac, 4ac Glass material 5, 5D, 5E, 5F Cylindrical member 6 Core base material 10, 10A, 10B, 10C, 10D, 10E, 10F Multi-core fiber base material 100 Drawing apparatus 101 Drawing heating furnace 101a Heater 102 Suction mechanism 102a Suction connector 102b Suction passage 102c Suction device 1 3 the outer diameter measuring device 104 covering the resin coating device 105 resin curing device 106 capstan roller 107 guide roll C controller C1 circumcircle Y1, Y2 arrow

Claims

A preparation step of preparing the clad base material having a plurality of through holes are formed extending in the long side direction,
A connecting step of connecting a cylindrical member coaxially with the clad base material to one end of the clad base material;
An insertion step of inserting a core base material into each of the plurality of through holes of the cladding base material;
A method for producing a multi-core fiber preform comprising:
An inner diameter of the cylindrical member is smaller than a diameter of a circumscribed circle of a through hole located on the outermost peripheral side among the plurality of through holes formed in the clad base material,
In the preparation step, the clad base material has a communication structure for communicating a through hole at least partially overlapping the cylindrical member in a top view among the plurality of through holes and the inside of the cylindrical member. Formed ,
The multi-core fiber preform manufacturing method , wherein the communication structure includes a recess formed at the one end of the clad preform .

The method for manufacturing a multi-core fiber preform according to claim 1 , wherein the recess is an annular groove.

The method for manufacturing a multi-core fiber preform according to claim 1 , wherein the recess is a circular recess.

The concave portion is configured by a communication groove portion that communicates a through hole that at least partially overlaps the cylindrical member in a top view and a through hole that does not overlap the cylindrical member in a top view. 2. A method for producing a multi-core fiber preform according to 1 .

Preparing a clad base material in which a plurality of through-holes extending in the longitudinal direction is formed;
A connecting step of connecting a cylindrical member coaxially with the clad base material to one end of the clad base material;
An insertion step of inserting a core base material into each of the plurality of through holes of the cladding base material;
A method for producing a multi-core fiber preform comprising:
An inner diameter of the cylindrical member is smaller than a diameter of a circumscribed circle of a through hole located on the outermost peripheral side among the plurality of through holes formed in the clad base material,
In the preparation step, the clad base material has a communication structure for communicating a through hole at least partially overlapping the cylindrical member in a top view among the plurality of through holes and the inside of the cylindrical member. Formed,
The communication structure is formed by a communication portion provided on the one end side of the clad base material ,
In the communication structure, in the communication portion, an opening provided to be open to the inside of the cylindrical member, one end of each is connected to each of the through holes, and the other end is the opening. features and to luma Ruchi core fiber manufacturing method of the preform that is formed by a plurality of communication holes which are connected to the part.

6. The method of manufacturing a multi-core fiber preform according to claim 5 , wherein an outer diameter of the communication portion is larger than an outer diameter of the clad preform.

Preparing a clad base material in which a plurality of through-holes extending in the longitudinal direction is formed;
A connecting step of connecting a cylindrical member coaxially with the clad base material to one end of the clad base material;
An insertion step of inserting a core base material into each of the plurality of through holes of the cladding base material;
A method for producing a multi-core fiber preform comprising:
An inner diameter of the cylindrical member is smaller than a diameter of a circumscribed circle of a through hole located on the outermost peripheral side among the plurality of through holes formed in the clad base material,
In the preparation step, the clad base material has a communication structure for communicating a through hole at least partially overlapping the cylindrical member in a top view among the plurality of through holes and the inside of the cylindrical member. Formed,
The communication structure is formed by a communication portion provided on the one end side of the clad base material,
Manufacturing method of the communicating portion outer diameter the clad base material that features and to luma Ruchi core preform larger than the outer diameter of.

The communication structure includes an opening provided in the communication portion so as to be open to the inside of the cylindrical member, a communication space that collectively communicates the plurality of through holes and the opening, The manufacturing method of the multi-core fiber preform according to claim 7 , wherein:

The gap between the claims 1-8 any one in the through-hole of the multi-core fiber preform produced by the production method according to the clad base material, while reducing the pressure through the cylindrical member, the multi-core fiber Heating and melting the other end portion of the base material opposite to the one end portion, and drawing a multi-core fiber having a plurality of core portions extending along a longitudinal axis from the other end portion. A method for producing a multi-core fiber.