JP5311417B2 - Optical fiber manufacturing method, optical fiber preform and manufacturing method thereof - Google Patents

Optical fiber manufacturing method, optical fiber preform and manufacturing method thereof Download PDF

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JP5311417B2
JP5311417B2 JP2010033187A JP2010033187A JP5311417B2 JP 5311417 B2 JP5311417 B2 JP 5311417B2 JP 2010033187 A JP2010033187 A JP 2010033187A JP 2010033187 A JP2010033187 A JP 2010033187A JP 5311417 B2 JP5311417 B2 JP 5311417B2
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refractive index
quartz rod
optical fiber
quartz
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JP2011170062A (en
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泰志 坂本
隆 松井
茂 冨田
晋聖 齊藤
正則 小柴
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Hokkaido University NUC
Nippon Telegraph and Telephone Corp
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02042—Multicore optical fibres

Description

本発明は２つ以上のコア領域を有する光ファイバの製造方法と、前記光ファイバを製造するための光ファイバ母材と、前記光ファイバ母材の製造方法に関するものである。 The present invention is a method for producing a fiber-optic having more than one core region, and the optical fiber optical fiber preform for producing a method for manufacturing the optical fiber preform.

光ファイバ通信システムでは、光ファイバ中で発生する非線形効果やファイバヒューズが問題となり、伝送の大容量化が制限されている。これらの制限を緩和するためには、光ファイバに導波する光の密度を低減する必要があり、ラージコアファイバやマルチコアファイバといった種々の光ファイバ構造が検討されている。   In optical fiber communication systems, non-linear effects and fiber fuses that occur in optical fibers are problematic, and transmission capacity is limited. In order to relax these restrictions, it is necessary to reduce the density of light guided to the optical fiber, and various optical fiber structures such as a large core fiber and a multi-core fiber have been studied.

例えば、非特許文献１では、１本の光ファイバに複数のコア領域を導入したマルチコアファイバによる伝送容量拡大に関する検討がなされている。   For example, in Non-Patent Document 1, studies have been made on expansion of transmission capacity using a multi-core fiber in which a plurality of core regions are introduced into one optical fiber.

Masanori Koshiba, Kunimasa Saitoh and Yasuo Kokubun, "Heterogeneous multi-core fibers: proposal and design principle," IEICE Electronics Express, vol. 6, pp.98-103 (2009).Masanori Koshiba, Kunimasa Saitoh and Yasuo Kokubun, "Heterogeneous multi-core fibers: proposal and design principle," IEICE Electronics Express, vol. 6, pp. 98-103 (2009). C. K. Jen, J. E. B. Oliveira, N. Goto, K. Abe, "Role of guided acoustic wave properties in single-mode optical fiber design," Electronics Letters, vol. 24, no. 23, pp. 1419-1420, Nov. 1998.CK Jen, JEB Oliveira, N. Goto, K. Abe, "Role of guided acoustic wave properties in single-mode optical fiber design," Electronics Letters, vol. 24, no. 23, pp. 1419-1420, Nov. 1998 .

しかしながら、従来のマルチコアファイバでは、コア領域の空間多重数を増やすためにコア領域間の距離を小さくすると、コア領域間のクロストークが増加し、各コア領域を伝搬する信号が劣化するという問題があった。   However, in the conventional multi-core fiber, if the distance between the core regions is decreased in order to increase the number of spatial multiplexing in the core region, there is a problem that crosstalk between the core regions increases and a signal propagating in each core region is deteriorated. there were.

従って、本発明は上記の事情に鑑み、コア領域間のクロストークを低減し、コア領域間の距離を狭めて、コア領域の空間多重数を増やすことができる光ファイバの製造方法並びに光ファイバ母材及びその製造方法を提供することを課題としている。 Accordingly, the present invention has been made in view of the above circumstances, to reduce the cross talk between the core region, narrowing the distance between the core region, the manufacturing method and an optical fiber of the fiber optic which can increase the number of spatial multiplexing of the core region It is an object to provide a base material and a manufacturing method thereof.

上記課題を解決する第１発明の光ファイバの製造方法は、２つ以上のコア領域と、前記コア領域の屈折率以下の屈折率を有するクラッド領域とを有する光ファイバにおいて、前記クラッド領域の屈折率より低い屈折率を有する低屈折率領域が、前記コア領域間に配置されていることを特徴とする光ファイバの製造方法であって、
第１の石英ロッド又は屈折率を増加させる不純物を部分的に添加した第１の石英ロッドの間又は周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド、又は、空孔を設けた第２の石英ロッドを配置し、その周囲に第３の石英ロッドを配置して、前記第１の石英ロッドと前記第２の石英ロッドと前記第３の石英ロッドの束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケットを装荷して、光ファイバ母材を製造し、
この光ファイバ母材を溶融延伸することによって、前記光ファイバを製造することを特徴とする。 An optical fiber manufacturing method according to a first aspect of the present invention that solves the above-described problem is an optical fiber having two or more core regions and a cladding region having a refractive index equal to or lower than the refractive index of the core region. A method of manufacturing an optical fiber , wherein a low refractive index region having a refractive index lower than the refractive index is disposed between the core regions ,
A first quartz rod or a second quartz rod partially doped with an impurity decreasing the refractive index between or around the first quartz rod partially doped with an impurity increasing the refractive index, or an empty space A second quartz rod provided with a hole is arranged, and a third quartz rod is arranged around the second quartz rod, and a bundle of the first quartz rod, the second quartz rod, and the third quartz rod. A quartz rod group is constructed, a pure quartz jacket is loaded around the quartz rod group, and an optical fiber preform is manufactured.
The optical fiber is manufactured by melt-drawing the optical fiber preform.

また、第２発明の光ファイバ母材は、２つ以上のコア領域と、前記コア領域の屈折率以下の屈折率を有するクラッド領域とを有する光ファイバにおいて、前記クラッド領域の屈折率より低い屈折率を有する低屈折率領域が、前記コア領域間に配置されていることを特徴とする光ファイバを製造するための光ファイバ母材であって、
第１の石英ロッド又は屈折率を増加させる不純物を部分的に添加した第１の石英ロッドの間又は周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド、又は、空孔を設けた第２の石英ロッドを配置し、その周囲に第３の石英ロッドを配置して、前記第１の石英ロッドと前記第２の石英ロッドと前記第３の石英ロッドの束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケットを装荷して成ることを特徴とする。 The optical fiber preform of the second invention is an optical fiber having two or more core regions and a cladding region having a refractive index less than or equal to the refractive index of the core region, and has a refractive index lower than the refractive index of the cladding region. An optical fiber preform for manufacturing an optical fiber , wherein a low refractive index region having a refractive index is disposed between the core regions ,
A first quartz rod or a second quartz rod partially doped with an impurity decreasing the refractive index between or around the first quartz rod partially doped with an impurity increasing the refractive index, or an empty space A second quartz rod provided with a hole is arranged, and a third quartz rod is arranged around the second quartz rod, and a bundle of the first quartz rod, the second quartz rod, and the third quartz rod. A quartz rod group is configured, and a pure quartz jacket is loaded around the quartz rod group.

また、第３発明の光ファイバ母材の製造方法は、２つ以上のコア領域と、前記コア領域の屈折率以下の屈折率を有するクラッド領域とを有する光ファイバにおいて、前記クラッド領域の屈折率より低い屈折率を有する低屈折率領域が、前記コア領域間に配置されていることを特徴とする光ファイバを製造するための光ファイバ母材の製造方法であって、
第１の石英ロッド又は屈折率を増加させる不純物を部分的に添加した第１の石英ロッドの間又は周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド、又は、空孔を設けた第２の石英ロッドを配置し、その周囲に第３の石英ロッドを配置して、前記第１の石英ロッドと前記第２の石英ロッドと前記第３の石英ロッドの束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケットを装荷して、前記光ファイバ母材を製造することを特徴とする。 According to a third aspect of the present invention, there is provided an optical fiber preform manufacturing method comprising: an optical fiber having two or more core regions; and a cladding region having a refractive index less than or equal to the refractive index of the core region. A method of manufacturing an optical fiber preform for manufacturing an optical fiber , wherein a low refractive index region having a lower refractive index is disposed between the core regions ,
A first quartz rod or a second quartz rod partially doped with an impurity decreasing the refractive index between or around the first quartz rod partially doped with an impurity increasing the refractive index, or an empty space A second quartz rod provided with a hole is arranged, and a third quartz rod is arranged around the second quartz rod, and a bundle of the first quartz rod, the second quartz rod, and the third quartz rod. A quartz rod group is formed, and a pure quartz jacket is loaded around the quartz rod group to manufacture the optical fiber preform.

本発明の光ファイバ製造方法によって製造した光ファイバによれば、コア領域間にクラッド領域の屈折率より低い屈折率を有する低屈折率領域を配置したことにより、各コア領域を伝搬する信号間のクロストークが低減されるため、コア領域間の距離を狭めることが可能であり、コア領域の空間多重数を増加することが可能であるという効果を奏し、光学特性の優れた光ファイバを実現することができる。そして、この光ファイバを光ファイバ通信システムに適用してコア領域の空間多重数を増加させれば、非線形効果やファイバヒューズを発生させることなく、大容量通信が可能となる。 According to the optical fiber manufactured by the optical fiber manufacturing method of the present invention, a low refractive index region having a refractive index lower than the refractive index of the cladding region is disposed between the core regions, so that signals transmitted through each core region can be transmitted. Since the crosstalk is reduced, the distance between the core regions can be reduced, and the spatial multiplexing number of the core regions can be increased, thereby realizing an optical fiber having excellent optical characteristics. be able to. If this optical fiber is applied to an optical fiber communication system to increase the number of spatial multiplexing in the core region, large-capacity communication can be performed without generating nonlinear effects and fiber fuses.

本発明の参考例に係る光ファイバの構成を示す断面図である。It is sectional drawing which shows the structure of the optical fiber which concerns on the reference example of this invention. 本発明の参考例に係る光ファイバの結合長の構造依存性を表す図である。It is a figure showing the structure dependence of the coupling length of the optical fiber which concerns on the reference example of this invention. 本発明の参考例に係る光ファイバの他の構成（低屈折率領域の配置例）を示す断面図である。It is sectional drawing which shows the other structure (example of arrangement | positioning of a low refractive index area | region) of the optical fiber which concerns on the reference example of this invention. 本発明の参考例に係る光ファイバの他の構成（低屈折率領域の配置例）を示す断面図である。It is sectional drawing which shows the other structure (example of arrangement | positioning of a low refractive index area | region) of the optical fiber which concerns on the reference example of this invention. 本発明の実施の形態例に係る光ファイバ母材の構成を示す断面図である。It is sectional drawing which shows the structure of the optical fiber preform which concerns on the example of embodiment of this invention. 前記光ファイバ母材を用いて製造した光ファイバの構成を示す断面図である。It is sectional drawing which shows the structure of the optical fiber manufactured using the said optical fiber preform | base_material.

以下、本発明の実施の形態例を図面に基づいて詳細に説明する。   Embodiments of the present invention will be described below in detail with reference to the drawings.

図１に示すように、本発明の参考例に係る光ファイバ１は、屈折率がｎ１である複数（図示例では２つ）のコア領域２と、屈折率がｎ２であるクラッド領域３と、屈折率がｎ３である低屈折率領域４とを有しており、各領域２，３，４の屈折率ｎ１，ｎ２，ｎ３の関係がｎ１≧ｎ２＞ｎ３である。なお、コア領域２及び低屈折率領域４は断面形状が円形状である。 As shown in FIG. 1, an optical fiber 1 according to a reference example of the present invention includes a plurality (two in the illustrated example) of core regions 2 having a refractive index n1, and a cladding region 3 having a refractive index n2. And a low refractive index region 4 having a refractive index of n3, and the relationship between the refractive indexes n1, n2, and n3 of the regions 2, 3, and 4 is n1 ≧ n2> n3. The core region 2 and the low refractive index region 4 have a circular cross section.

そして、低屈折率領域４は、各コア領域２を中心として、各コア領域２の周りに離散的に配置されて正六角形状を成している。即ち、このようにコア領域２の周りに低屈折率領域４を正六角形状に配置することにより、クラッド領域３の屈折率ｎ２より低い屈折率ｎ３を有する低屈折率領域４が、コア領域２間に配置された構造になっている。
また、コア領域２の直径を２ａ、コア領域２とクラッド領域３の比屈折率差をΔ、コア領域２の間隔をD、低屈折率領域４の間隔と直径をΛ，ｄとしている。 The low refractive index regions 4 are discretely arranged around each core region 2 around each core region 2 to form a regular hexagon. That is, by arranging the low refractive index region 4 in the shape of a regular hexagon around the core region 2 in this way, the low refractive index region 4 having a refractive index n3 lower than the refractive index n2 of the cladding region 3 becomes the core region 2. It has a structure arranged between them.
Further, the diameter of the core region 2 is 2a, the relative refractive index difference between the core region 2 and the cladding region 3 is Δ, the interval between the core regions 2 is D, and the interval and diameter between the low refractive index regions 4 are Λ and d.

図１の構造においてｎ１≧ｎ２＞ｎ３の屈折率条件は、各領域２，３，４の材料を純石英、又は酸化ゲルマニウム（ＧｅＯ2）や酸化アルミニウム（Ａｌ2Ｏ3）、酸化リン（Ｐ2Ｏ5）などの屈折率を増加させる不純物を添加した石英や、フッ素（Ｆ2）、酸化ほう素（Ｂ2Ｏ3）など屈折率を低減させる不純物を添加した石英を用いることで実現できる。
例えば、コア領域２を構成する材料は屈折率を増加させる不純物を添加した石英とし、クラッド領域３を構成する材料は純石英とし、低屈折率領域４は屈折率を低減させる不純物を添加した石英とした場合、ｎ１＞ｎ２＞ｎ３となるため、前記屈折率条件を実現することができる。また、コア領域２を構成する材料は純石英とし、クラッド領域３を構成する材料は純石英とし、低屈折率領域４は屈折率を低減させる不純物を添加した石英とした場合にも、ｎ１＝ｎ２＞ｎ３となるため、前記屈折率条件を実現することができる。
なお、屈折率を変化（増減）させる添加物の代表的なものが非特許文献２に示されているが、屈折率を増減させる働きをする添加物であれば、ここに記載されている物質に限定されない。
また、前記屈折率条件を実現するためには、低屈折率領域４を空孔とすることもできる。 In the structure of FIG. 1, the refractive index condition of n1 ≧ n2> n3 is that the materials of the regions 2, 3, and 4 are pure quartz, germanium oxide (GeO 2 ), aluminum oxide (Al 2 O 3 ), phosphorus oxide (P This can be realized by using quartz to which an impurity for increasing the refractive index such as 2 O 5 ) is added, or quartz to which an impurity for reducing the refractive index such as fluorine (F 2 ) or boron oxide (B 2 O 3 ) is added. .
For example, the material constituting the core region 2 is quartz added with an impurity for increasing the refractive index, the material constituting the cladding region 3 is pure quartz, and the low refractive index region 4 is a quartz added with an impurity for reducing the refractive index. In this case, since n1>n2> n3, the refractive index condition can be realized. In addition, when the material constituting the core region 2 is pure quartz, the material constituting the cladding region 3 is pure quartz, and the low refractive index region 4 is quartz added with an impurity for reducing the refractive index, n1 = Since n2> n3, the refractive index condition can be realized.
In addition, although the typical thing of the additive which changes (increases / decreases) a refractive index is shown by the nonpatent literature 2, if it is an additive which acts to increase / decrease a refractive index, the substance described here It is not limited to.
Moreover, in order to implement | achieve the said refractive index conditions, the low refractive index area | region 4 can also be made into a void | hole.

図２に本発明の参考例の光ファイバ１における結合長の構造依存性を示す。結合長とは、コア領域２から他のコア領域２へ光パワーが最も移行するために必要な光ファイバ長であり、各コア領域２を独立した伝送路として用いるためには結合長を長くする必要がある。 FIG. 2 shows the structure dependence of the coupling length in the optical fiber 1 of the reference example of the present invention. The coupling length is an optical fiber length necessary for the optical power to most transfer from the core region 2 to another core region 2, and in order to use each core region 2 as an independent transmission path, the coupling length is increased. There is a need.

ここでは、２ａ＝８．０μｍ、Δ＝０．３５％、Ｄ＝４Λとし、低屈折率領域４は空孔（ｎ３＝１）とした。動作波長を１５５０ｎｍとした場合、空孔（低屈折率領域）の間隔Λ＝１１μｍ程度、ｄ／Λ＞０．５０とすれば、結合長を１０ｋｍ以上に設定でき、低屈折率層が存在しない従来型のマルチコアファイバの場合(ｄ／Λ＝０の場合)の結合長が約１００ｍであることと比較して、結合長を１００倍以上に長くできることがわかる。
なお、この計算結果は光ファイバの長手方向に全く摂動がなく、光ファイバ１が直線の状態で伝搬できた場合の結合長であり、実際は前記長手方向にミクロな構造揺らぎやわずかな曲がり部分が存在することからパワーの移行率が急減するため、実用上は、理論的な結合長よりも長い距離の伝送が可能である。 Here, 2a = 8.0 μm, Δ = 0.35%, D = 4Λ, and the low refractive index region 4 is a hole (n3 = 1). When the operating wavelength is 1550 nm, the coupling length can be set to 10 km or more if there is a gap (low refractive index region) interval Λ = 11 μm and d / Λ> 0.50, and there is no low refractive index layer. It can be seen that the coupling length can be increased by a factor of 100 or more compared to the coupling length of the conventional multi-core fiber (d / Λ = 0) being about 100 m.
This calculation result is the coupling length when there is no perturbation in the longitudinal direction of the optical fiber and the optical fiber 1 can propagate in a straight line. Actually, there are micro structural fluctuations and slight bends in the longitudinal direction. Since the power transfer rate rapidly decreases because of the existence, transmission over a distance longer than the theoretical coupling length is possible in practice.

なお、図１では低屈折率領域４の配置を各コア領域２に対して正六角形状としたが、低屈折率領域４の配置は各コア領域２に対して、正六角形以外の正多角形状又は図３（ａ）に示すような円環状にしてもよい。
また、図３（ｂ）に示すように低屈折率領域４はコア領域２間にのみ配置してもよい。 また、図３（ｃ）に示すように低屈折率領域４は、複数のコア領域２で低屈折率領域４を共有するような正多角形状の配置でもよい。 In FIG. 1, the low refractive index region 4 is arranged in a regular hexagonal shape with respect to each core region 2, but the low refractive index region 4 is arranged in a regular polygonal shape other than a regular hexagon with respect to each core region 2. Alternatively, an annular shape as shown in FIG.
Further, the low refractive index region 4 may be disposed only between the core regions 2 as shown in FIG. Further, as shown in FIG. 3C, the low refractive index region 4 may be arranged in a regular polygon shape such that the plurality of core regions 2 share the low refractive index region 4.

また、低屈折率領域４の正多角形状や円環状の配置については、各コア領域２に対して、図１や図３（ａ）のように１層の場合に限らず、２層以上設けてもよい。
また、低屈折率領域４の正多角形状や円環状の配置については、図１，図３（ａ），図３（ｃ）のようにコア領域２間の延長線上（隣り合うコア領域２の断面中心同士を結ぶ線上）に低屈折率領域４が存在している必要はなく、図４（ａ）、図４（ｂ）に示すようにコア領域２間に平均的な低屈折率領域が存在していればよい。即ち、図４（ａ）や図４（ｂ）に例示するような状態でコア領域２間に低屈折率領域４が配置されて、隣り合うコア領域２間の部分に低屈折率領域４が存在することにより、この隣り合うコア領域２間の部分おける平均的な屈折率が、クラッド領域３の屈折率よりも低くなっていればよい。
同様に、コア領域２間にのみ低屈折率領域４を配置する場合にも、図３（ｂ）のようにコア領域２間の延長線上（隣り合うコア領域２の断面中心同士を結ぶ線上）に低屈折率領域４が存在している必要はなく、コア領域２間に平均的な低屈折率領域が存在していればよい。
また、図１などにはコア領域２を２つ設けた例を示しているが、コア領域２の数は３つ以上でもよい。 Further, the regular polygonal shape and the annular arrangement of the low refractive index region 4 are not limited to the case of one layer as shown in FIG. 1 and FIG. May be.
In addition, the regular polygonal shape and the annular arrangement of the low refractive index region 4 are on the extension line between the core regions 2 as shown in FIG. 1, FIG. 3A and FIG. It is not necessary that the low refractive index region 4 exists on the line connecting the cross-sectional centers, and an average low refractive index region is present between the core regions 2 as shown in FIGS. 4 (a) and 4 (b). It only has to exist. That is, the low refractive index region 4 is disposed between the core regions 2 in the state illustrated in FIG. 4A and FIG. 4B, and the low refractive index region 4 is provided between the adjacent core regions 2. By being present, the average refractive index in the portion between the adjacent core regions 2 only needs to be lower than the refractive index of the cladding region 3.
Similarly, when the low refractive index region 4 is disposed only between the core regions 2, on the extension line between the core regions 2 (on the line connecting the cross-sectional centers of the adjacent core regions 2) as shown in FIG. It is not necessary that the low refractive index region 4 exists in the core layer 2, and an average low refractive index region may exist between the core regions 2.
Moreover, although the example which provided two core area | regions 2 is shown in FIG. 1 etc., the number of the core area | regions 2 may be three or more.

次に、図５に基づき、本発明の実施の形態例に係る光ファイバの製造方法について説明する。図５に例示する本発明の実施の形態例に係る光ファイバ母材１０は、７つのコア領域を有する光ファイバ（図６参照）を製造するためのものである。 Next, based on FIG. 5, the manufacturing method of the optical fiber which concerns on the embodiment of this invention is demonstrated . An optical fiber preform 10 according to an embodiment of the present invention illustrated in FIG. 5 is for manufacturing an optical fiber (see FIG. 6) having seven core regions.

図５に示すように、光ファイバ母材１０は、第１の石英ロッド１１と第２の石英ロッド１４と第３の石英ロッド１５と純石英ジャケット１６とを有して成るものである。
第１の石英ロッド１１には、ＧｅＯ2、Ａｌ2Ｏ3、Ｐ2Ｏ5などの屈折率を増加させる不純物を部分的（図示例では第１の石英ロッド１１の断面中央部）に添加して、屈折率を増加させた部分１２を設けている。或いは、屈折率を増加させる不純物を添加していない石英ロッド（即ち純石英のロッド）を、第１の石英ロッド１１として用いてもよい。
第２の石英ロッド１３には、Ｆ2、Ｂ2Ｏ3などの屈折率を減少させる不純物を部分的（図示例では第２の石英ロッド１３の断面中央部）に添加して、屈折率を減少させた部分１４を設けている。或いは、屈折率を減少させた部分１４を設けた第２の石英ロッド１３に代えて、空孔を設けた第２の石英ロッド１３を用いてもよい。
第３の石英ロッド１５は、屈折率を増減する不純物を添加していない石英ロッド（即ち純石英のロッド）である。 As shown in FIG. 5, the optical fiber preform 10 includes a first quartz rod 11, a second quartz rod 14, a third quartz rod 15, and a pure quartz jacket 16.
Impurities that increase the refractive index, such as GeO 2 , Al 2 O 3 , and P 2 O 5, are partially added to the first quartz rod 11 (in the illustrated example, the central portion of the cross section of the first quartz rod 11). Thus, a portion 12 having an increased refractive index is provided. Alternatively, a quartz rod to which an impurity for increasing the refractive index is not added (that is, a pure quartz rod) may be used as the first quartz rod 11.
Impurities that reduce the refractive index, such as F 2 and B 2 O 3, are partially added to the second quartz rod 13 (in the illustrated example, the central portion of the cross section of the second quartz rod 13), thereby adjusting the refractive index. A reduced portion 14 is provided. Alternatively, the second quartz rod 13 provided with holes may be used in place of the second quartz rod 13 provided with the portion 14 having a reduced refractive index.
The third quartz rod 15 is a quartz rod (that is, a pure quartz rod) to which an impurity that increases or decreases the refractive index is not added.

第１の石英ロッド１１（純石英のロッド）、又は、屈折率を増加させる不純物を部分的に添加した第１の石英ロッド１１は、中心部とその周辺部に正六角形状に配置する。
そして、各第１の石英ロッド１１を中心として、各第１の石英ロッド１１の周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド１３、又は空孔を設けた第２の石英ロッド１３を正多角形状又は円形状（図示例では正六角形状）に配置し、その周囲に第３の石英ロッド１５を配置して、第１の石英ロッド１１と第２の石英ロッド１３と第３の石英ロッド１５の束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケット１６を装荷することによって、光ファイバ母材１０を形成する。なお、図示例では、石英ロッド群の周縁部に比較的細い第３の石英ロッド１５を配置して、石英ロッド群が円柱状を成すようにしている。 The first quartz rod 11 (pure quartz rod) or the first quartz rod 11 to which an impurity for increasing the refractive index is partially added is arranged in a regular hexagonal shape at the central portion and its peripheral portion.
Then, a second quartz rod 13 in which an impurity for reducing the refractive index is partially added or a hole is provided around each first quartz rod 11 around each first quartz rod 11. Two quartz rods 13 are arranged in a regular polygonal shape or a circular shape (regular hexagonal shape in the illustrated example), and a third quartz rod 15 is arranged around the quartz rod 13, and the first quartz rod 11 and the second quartz rod are arranged. The optical fiber preform 10 is formed by forming a quartz rod group which is a bundle of the 13 and the third quartz rod 15 and loading a pure quartz jacket 16 around the quartz rod group. In the illustrated example, a relatively thin third quartz rod 15 is disposed at the peripheral edge of the quartz rod group so that the quartz rod group has a cylindrical shape.

次に、この光ファイバ母材１０を（即ち石英ロッド群及び純石英ジャケット１６を一括して）溶融延伸することにより、図６に示すような光ファイバ１を製造する。なお、図５の状態の光ファイバ母材１０を、一旦、溶融延伸し、この溶融延伸後の光ファイバ母材１を更に溶融延伸して（即ち２段階の溶融延伸をして）、光ファイバ１を製造してもよい。
図６では、純石英の第１の石英ロッド１１又は第１の石英ロッド１１の屈折率を増加させた部分１２に相当するコア領域２が、中心部とその周辺部に正六角形状に配置され、第２の石英ロッド１３の屈折率を減少させた部分１４又は空孔に相当する低屈折率領域４が、コア領域２を中心として正多角形状又は円形状（図示例では正六角形状）に配置されている。 Next, the optical fiber preform 10 is manufactured by melting and stretching the optical fiber preform 10 (that is, the quartz rod group and the pure quartz jacket 16 collectively), thereby producing the optical fiber 1 as shown in FIG. The optical fiber preform 10 in the state shown in FIG. 5 is once melt-stretched, and the melt-stretched optical fiber preform 1 is further melt-stretched (that is, two-stage melt-stretching) to obtain an optical fiber. 1 may be manufactured.
In FIG. 6, the core region 2 corresponding to the first quartz rod 11 of pure quartz or the portion 12 where the refractive index of the first quartz rod 11 is increased is arranged in a regular hexagonal shape at the central portion and its peripheral portion. The low-refractive index region 4 corresponding to the portion 14 or the hole in which the refractive index of the second quartz rod 13 is reduced is a regular polygon or circle (regular hexagon in the illustrated example) with the core region 2 as the center. Has been placed.

なお、低屈折率領域４をコア領２域間にのみ配置した光ファイバ（図３（ｂ）参照）を製造する場合には、上記の光ファイバ母材１０の製造方法において、第１の石英ロッド１１の間にのみ、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド１３、又は空孔を設けた第２の石英ロッド１３を配置すればよい。   In the case of manufacturing an optical fiber (see FIG. 3B) in which the low refractive index region 4 is disposed only between the two core regions, the first quartz is used in the manufacturing method of the optical fiber preform 10 described above. Only between the rods 11, the second quartz rod 13 to which an impurity for reducing the refractive index is partially added or the second quartz rod 13 provided with holes may be disposed.

本発明の光ファイバ製造方法によって製造した光ファイバによれば、コア領域２間にクラッド領域３の屈折率ｎ２より低い屈折率ｎ３を有する低屈折率領域４を配置したことにより、各コア領域２を伝搬する信号間のクロストークが低減されるため、コア領域２間の距離を狭めることが可能であり、コア領域２の空間多重数を増加することが可能であるという効果を奏し、光学特性の優れた光ファイバ１を実現することができる。そして、この光ファイバ１を光ファイバ通信システムに適用してコア領域２の空間多重数を増加させれば、非線形効果やファイバヒューズを発生させることなく、大容量通信が可能となる。 According to the optical fiber manufactured by the optical fiber manufacturing method of the present invention, the low refractive index region 4 having the refractive index n3 lower than the refractive index n2 of the cladding region 3 is disposed between the core regions 2, thereby providing each core region 2. Since the crosstalk between signals propagating in the core region 2 is reduced, the distance between the core regions 2 can be reduced, and the spatial multiplexing number of the core region 2 can be increased. An excellent optical fiber 1 can be realized. If this optical fiber 1 is applied to an optical fiber communication system and the number of spatial multiplexing in the core region 2 is increased, large-capacity communication can be achieved without generating non-linear effects and fiber fuses.

本発明は光ファイバ製造方法並びに光ファイバ母材及びその製造方法に関するものであり、光伝送システムにおける伝送媒体として利用される光ファイバ及びその母材に適用して有用なものである。 The present invention relates to fiber optic Manufacturing method and an optical fiber preform and a manufacturing method thereof, is useful when applied to the optical fiber and its preform is utilized as a transmission medium in an optical transmission system.

１ 光ファイバ
２ コア領域
３ クラッド領域
４ 低屈折率領域
１０ 光ファイバ母材
１１ 第１の石英ロッド
１２ 屈折率を増加させた部分
１３ 第２の石英ロッド
１４ 屈折率を減少させた部分
１５ 第３の石英ロッド
１６ 純石英ジャケット DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Core area | region 3 Clad area | region 4 Low refractive index area | region 10 Optical fiber preform | base_material 11 1st quartz rod 12 The part which increased the refractive index 13 2nd quartz rod 14 The part which decreased the refractive index 15 3rd Quartz rod 16 pure quartz jacket

Claims (3)

２つ以上のコア領域と、前記コア領域の屈折率以下の屈折率を有するクラッド領域とを有する光ファイバにおいて、前記クラッド領域の屈折率より低い屈折率を有する低屈折率領域が、前記コア領域間に配置されていることを特徴とする光ファイバの製造方法であって、
第１の石英ロッド又は屈折率を増加させる不純物を部分的に添加した第１の石英ロッドの間又は周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド、又は、空孔を設けた第２の石英ロッドを配置し、その周囲に第３の石英ロッドを配置して、前記第１の石英ロッドと前記第２の石英ロッドと前記第３の石英ロッドの束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケットを装荷して、光ファイバ母材を製造し、
この光ファイバ母材を溶融延伸することによって、前記光ファイバを製造することを特徴とする光ファイバ製造方法。 In an optical fiber having two or more core regions and a cladding region having a refractive index less than or equal to the refractive index of the core region, the low refractive index region having a refractive index lower than the refractive index of the cladding region is the core region. An optical fiber manufacturing method characterized by being disposed between ,
A first quartz rod or a second quartz rod partially doped with an impurity decreasing the refractive index between or around the first quartz rod partially doped with an impurity increasing the refractive index, or an empty space A second quartz rod provided with a hole is arranged, and a third quartz rod is arranged around the second quartz rod, and a bundle of the first quartz rod, the second quartz rod, and the third quartz rod. A quartz rod group is constructed, a pure quartz jacket is loaded around the quartz rod group, and an optical fiber preform is manufactured.
An optical fiber manufacturing method comprising manufacturing the optical fiber by melt-drawing the optical fiber preform. ２つ以上のコア領域と、前記コア領域の屈折率以下の屈折率を有するクラッド領域とを有する光ファイバにおいて、前記クラッド領域の屈折率より低い屈折率を有する低屈折率領域が、前記コア領域間に配置されていることを特徴とする光ファイバを製造するための光ファイバ母材であって、
第１の石英ロッド又は屈折率を増加させる不純物を部分的に添加した第１の石英ロッドの間又は周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド、又は、空孔を設けた第２の石英ロッドを配置し、その周囲に第３の石英ロッドを配置して、前記第１の石英ロッドと前記第２の石英ロッドと前記第３の石英ロッドの束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケットを装荷して成ることを特徴とする光ファイバ母材。 In an optical fiber having two or more core regions and a cladding region having a refractive index less than or equal to the refractive index of the core region, the low refractive index region having a refractive index lower than the refractive index of the cladding region is the core region. An optical fiber preform for manufacturing an optical fiber, characterized in that it is disposed between ,
A first quartz rod or a second quartz rod partially doped with an impurity decreasing the refractive index between or around the first quartz rod partially doped with an impurity increasing the refractive index, or an empty space A second quartz rod provided with a hole is arranged, and a third quartz rod is arranged around the second quartz rod, and a bundle of the first quartz rod, the second quartz rod, and the third quartz rod. An optical fiber preform comprising a group of quartz rods and a pure quartz jacket loaded around the group of quartz rods. ２つ以上のコア領域と、前記コア領域の屈折率以下の屈折率を有するクラッド領域とを有する光ファイバにおいて、前記クラッド領域の屈折率より低い屈折率を有する低屈折率領域が、前記コア領域間に配置されていることを特徴とする光ファイバを製造するための光ファイバ母材の製造方法であって、
第１の石英ロッド又は屈折率を増加させる不純物を部分的に添加した第１の石英ロッドの間又は周りに、屈折率を減少させる不純物を部分的に添加した第２の石英ロッド、又は、空孔を設けた第２の石英ロッドを配置し、その周囲に第３の石英ロッドを配置して、前記第１の石英ロッドと前記第２の石英ロッドと前記第３の石英ロッドの束である石英ロッド群を構成し、この石英ロッド群の周りに純石英ジャケットを装荷して、前記光ファイバ母材を製造することを特徴とする光ファイバ母材の製造方法。 In an optical fiber having two or more core regions and a cladding region having a refractive index less than or equal to the refractive index of the core region, the low refractive index region having a refractive index lower than the refractive index of the cladding region is the core region. An optical fiber preform manufacturing method for manufacturing an optical fiber, wherein the optical fiber preform is disposed between
A first quartz rod or a second quartz rod partially doped with an impurity decreasing the refractive index between or around the first quartz rod partially doped with an impurity increasing the refractive index, or an empty space A second quartz rod provided with a hole is arranged, and a third quartz rod is arranged around the second quartz rod, and a bundle of the first quartz rod, the second quartz rod, and the third quartz rod. A method of manufacturing an optical fiber preform, comprising a group of quartz rods and loading a pure quartz jacket around the quartz rod group to produce the optical fiber preform.
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