JP4465530B2 - Optical fiber connection method - Google Patents

Optical fiber connection method Download PDF

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JP4465530B2
JP4465530B2 JP2005144710A JP2005144710A JP4465530B2 JP 4465530 B2 JP4465530 B2 JP 4465530B2 JP 2005144710 A JP2005144710 A JP 2005144710A JP 2005144710 A JP2005144710 A JP 2005144710A JP 4465530 B2 JP4465530 B2 JP 4465530B2
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optical fiber
optical fibers
core
optical
connection
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和人 斎藤
真樹 大村
修 茨木
雅夫 木下
宏 増田
修司 鈴木
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Sumitomo Electric Industries Ltd
Showa Denko Materials Co Ltd
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Hitachi Chemical Co Ltd
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Showa Denko Materials Co Ltd
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Description

本発明は光ファイバの接続方法に係り、例えば開口数（ＮＡ；Numerical Aperture）やコアの外径が互いに異なる光ファイバ同士を接続することができる光ファイバの接続方法に関するものである。   The present invention relates to an optical fiber connection method, for example, an optical fiber connection method that can connect optical fibers having different numerical apertures (NA) and different core outer diameters.

従来より、光ファイバ同士を接続する接続方法として光ファイバの融着接続方法が知られている（例えば特許文献１参照）。
図６（Ａ）および（Ｂ）に示すように、この光ファイバの融着接続方法では、第１の光ファイバ１０１の接続端面側と第２の光ファイバ１０２の接続端面側とを対向配置し、両光ファイバ１０１、１０２の接続端面側に対の放電電極１０３、１０３から発生する高電圧を加えて、高電圧によって両接続端面側を加熱溶融して接続する。両光ファイバ１０１、１０２のモードフィールド径が互いに異なる場合には、図６（Ａ）に示すように、放電電極１０３の電極先端１０３ａ間を結ぶ直線Ｂと、第１の光ファイバ１０１と第２の光ファイバ１０２の接続端面軸心間を結ぶ直線Ａとの成す角度を直交させて融着接続した後、図６（Ｂ）に示すように、直線Ｂと直線Ａとの成す角度θを直角とは異なる角度になるようにして、直線Ａと直線Ｂとを斜めに交差させ、光ファイバの加熱領域を広げて加熱して光ファイバのコアのドーパント拡散を行う。
特開平１１−３０５０６５号公報（図２） Conventionally, an optical fiber fusion splicing method is known as a connection method for connecting optical fibers (see, for example, Patent Document 1).
As shown in FIGS. 6A and 6B, in this fusion splicing method of optical fibers, the connection end face side of the first optical fiber 101 and the connection end face side of the second optical fiber 102 are arranged to face each other. A high voltage generated from the pair of discharge electrodes 103, 103 is applied to the connection end face side of both optical fibers 101, 102, and both connection end face sides are heated and melted by the high voltage to be connected. When the mode field diameters of the two optical fibers 101 and 102 are different from each other, as shown in FIG. 6A, a straight line B connecting the electrode tips 103a of the discharge electrode 103, the first optical fiber 101, and the second optical fiber 101 After the fusion-splicing is performed with the angle formed by the straight line A connecting between the connection end face axes of the optical fiber 102 being orthogonal, the angle θ formed by the straight line B and the straight line A is a right angle as shown in FIG. The straight line A and the straight line B are obliquely intersected so as to be at different angles, and the heating region of the optical fiber is widened and heated to perform dopant diffusion of the core of the optical fiber.
Japanese Patent Application Laid-Open No. 11-305065 (FIG. 2)

ところで、近年、曲げに強い光ファイバの要求に伴って、光の閉じ込めを強くした光ファイバの試みがあり、コア／クラッドの比屈折率差Δｎを大きくした（すなわち開口数を大きくした）光ファイバが登場している。これら高開口数の光ファイバと通常の汎用光ファイバとを接続する場合、コア径が一致している場合であってもＮＡが不一致のため、０．５ｄＢ〜１ｄＢもの過剰な接続損失が発生してしまう。
従って、マルチモード光ファイバ同士を接続する場合には、コア径のみならず、開口数を一致させないとモードミスマッチを生じて低損失な接続が得られないという不都合があった。 By the way, in recent years, with the demand for an optical fiber that is resistant to bending, there has been an attempt of an optical fiber in which light confinement has been strengthened. Has appeared. When these high numerical aperture optical fibers are connected to ordinary general-purpose optical fibers, even if the core diameters match, the NAs do not match, so an excessive connection loss of 0.5 dB to 1 dB occurs. End up.
Therefore, when connecting multi-mode optical fibers, there is a disadvantage that a low-loss connection cannot be obtained by causing a mode mismatch unless the numerical apertures are matched in addition to the core diameter.

本発明は、前述した問題点に鑑みてなされたものであり、その目的は、コア径のみならず開口数が異なる光ファイバ同士を低接続損失で接続することができる光ファイバの接続方法を提供することにある。   The present invention has been made in view of the above-described problems, and an object thereof is to provide an optical fiber connection method capable of connecting optical fibers having different numerical apertures as well as core diameters with low connection loss. There is to do.

前述した目的を達成するために、本発明にかかる光ファイバの接続方法は、光ファイバ同士を接続する光ファイバの接続方法であって、開口数が異なる前記光ファイバの接続面を突き合わせて加熱融着し、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続した後、融着接続された前記光ファイバを、接続部で切断し、切断されたそれぞれの光ファイバに光コネクタを装着して光ファイバ同士を接続することを特徴としている。 To achieve the above object, a method of connecting an optical fiber according to the present invention is a method of connecting an optical fiber for connecting the optical fibers, heating fusion numerical aperture against the connecting surface of said different optical fiber And after diffusing the dopant of the core of the optical fiber having the larger numerical aperture and connecting the optical fibers so that the numerical apertures of the two optical fibers are close to each other , the fused optical fiber is cut at the connection portion, An optical connector is attached to each cut optical fiber, and the optical fibers are connected to each other .

このように構成された光ファイバの接続方法においては、光ファイバ同士を接続する際に、両接続面を突き合わせて加熱融着するが、このとき、開口数が大きい方の光ファイバのコアのドーパントをクラッドに拡散させるように加熱して開口数を小さくする。これにより、両光ファイバの開口数を近づけることができるので、開口数が異なる光ファイバ同士を低接続損失で接続することができることになる。   In the optical fiber connecting method configured as described above, when connecting the optical fibers, both connecting surfaces are abutted and heat-sealed. At this time, the dopant of the core of the optical fiber having the larger numerical aperture is used. To reduce the numerical aperture. Thereby, since the numerical apertures of both optical fibers can be made closer, optical fibers having different numerical apertures can be connected with low connection loss.

また、本発明にかかる光ファイバの接続方法は、前述したように、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続する接続方法であって、前記両光ファイバの開口数を接続面において一致させることを特徴としている。   In addition, as described above, the optical fiber connection method according to the present invention is a connection method in which the dopant of the core of the optical fiber having the larger numerical aperture is diffused so that the numerical apertures of both optical fibers are close to each other. In addition, the numerical apertures of the two optical fibers are matched at the connection surface.

このように構成された光ファイバの接続方法においては、開口数が異なる光ファイバ同士を接続する際に、接続面における両開口数が一致するようにしたので、開口数が異なる光ファイバ同士を低接続損失で接続することができることになる。   In the optical fiber connecting method configured as described above, when connecting optical fibers having different numerical apertures, the numerical apertures on the connection surface are made to coincide with each other. Connection can be made with connection loss.

また、本発明にかかる光ファイバの接続方法は、前述したように、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続する接続方法であって、前記両光ファイバのコア径が互いに異なることを特徴としている。   In addition, as described above, the optical fiber connection method according to the present invention is a connection method in which the dopant of the core of the optical fiber having the larger numerical aperture is diffused so that the numerical apertures of both optical fibers are close to each other. The core diameters of the two optical fibers are different from each other.

このように構成された光ファイバの接続方法においては、開口数のみならずコア径が互いに異なる光ファイバ同士を、低接続損失で接続することができることになる。   In the optical fiber connecting method thus configured, optical fibers having different core diameters as well as numerical apertures can be connected with low connection loss.

また、本発明にかかる光ファイバの接続方法は、前述したように、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続する接続方法であって、前記コア径が小さい方の光ファイバの開口数が、コア径が大きい方の光ファイバの開口数よりも大きいことを特徴としている。   In addition, as described above, the optical fiber connection method according to the present invention is a connection method in which the dopant of the core of the optical fiber having the larger numerical aperture is diffused so that the numerical apertures of both optical fibers are close to each other. The numerical aperture of the optical fiber having the smaller core diameter is larger than the numerical aperture of the optical fiber having the larger core diameter.

このように構成された光ファイバの接続方法においては、コア径が細い方を加熱処理することにより、コア径を拡径化して太い方のコア径に近づけることができると同時にドーパントをクラッドに拡散させて開口数を低下させ太い方の開口数に近づけることができる。   In the optical fiber connection method configured in this way, the core diameter can be increased by heating the one with the smaller core diameter, and the dopant can be diffused into the cladding at the same time. Thus, the numerical aperture can be reduced to approach the larger numerical aperture.

また、本発明にかかる光ファイバの接続方法は、前述したように、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続する接続方法であって、前記両光ファイバのコア径が同じことを特徴としている。   In addition, as described above, the optical fiber connection method according to the present invention is a connection method in which the dopant of the core of the optical fiber having the larger numerical aperture is diffused so that the numerical apertures of both optical fibers are close to each other. The core diameters of the two optical fibers are the same.

このように構成された光ファイバの接続方法においては、コア径は同じだが開口数が異なる光ファイバ同士を、低接続損失で接続することができることになる。   In the optical fiber connecting method configured as described above, optical fibers having the same core diameter but different numerical apertures can be connected with low connection loss.

また、本発明にかかる光ファイバの接続方法は、前述したように、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続する接続方法であって、前記両光ファイバは、マルチモード光ファイバであることを特徴としている。   In addition, as described above, the optical fiber connection method according to the present invention is a connection method in which the dopant of the core of the optical fiber having the larger numerical aperture is diffused so that the numerical apertures of both optical fibers are close to each other. The two optical fibers are multimode optical fibers.

このように構成された光ファイバの接続方法においては、種々のコア径を有するマルチモード光ファイバ同士を、低接続損失で接続することができる。   In the optical fiber connection method configured as described above, multimode optical fibers having various core diameters can be connected with low connection loss.

本発明によれば、開口数が大きい方の光ファイバのコアのドーパントを拡散させるように加熱して融着させることにより、両光ファイバの開口数を近づけることができるので、開口数が異なる光ファイバ同士を低接続損失で接続することができることになるという効果が得られる。   According to the present invention, the numerical apertures of both optical fibers can be made close to each other by heating and fusing so that the dopant of the core of the optical fiber having the larger numerical aperture is diffused. The effect is obtained that the fibers can be connected with a low connection loss.

以下、本発明に係る実施形態を図面に基づいて詳細に説明する。
図１は本発明の前提となる光ファイバの接続方法に係る実施形態を示す断面図、図２は開口数の説明図、図３は本発明に係る光ファイバの接続方法を実行する接続装置の概略構成図、図４（Ａ）はコア径が互いに異なる光ファイバ同士の接続を示す断面図、図４（Ｂ）は（Ａ）により接続した接続部を示す断面図である。 DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of an optical fiber connecting method as a premise of the present invention, FIG. 2 is an explanatory view of a numerical aperture, and FIG. 3 is a connection device for executing the optical fiber connecting method according to the present invention. FIG. 4A is a schematic configuration diagram, FIG. 4A is a cross-sectional view showing connection between optical fibers having different core diameters, and FIG. 4B is a cross-sectional view showing a connection portion connected by (A).

図１に示すように、本発明の前提となる光ファイバの接続方法は、光ファイバ１０、１１の接続面１０ａ、１１ａを突き合わせて加熱し、開口数ＮＡ１、ＮＡ２（ＮＡ１＞ＮＡ２）が大きい方の光ファイバ１０のコア１２のドーパントをクラッド１３に拡散させて、両光ファイバ１０、１１の開口数ＮＡ１、ＮＡ２を近づけるように接続するものである。なお、このとき、両光ファイバ１０，１１の開口数ＮＡ１、ＮＡ２を接続面１０ａ、１１ａにおいて一致させるようにするのが望ましい。
なお、図１中、光ファイバ１０、１１は、コア１２の周囲にクラッド１３を設けたものである。また、光ファイバ１０、１１としては、マルチモードの光ファイバを用いるのが望ましい。 As shown in FIG. 1, the method for connecting optical fibers, which is a premise of the present invention, heats the connection surfaces 10a and 11a of the optical fibers 10 and 11 and heats them, and has a larger numerical aperture NA1 and NA2 (NA1> NA2). The dopant of the core 12 of the optical fiber 10 is diffused into the clad 13 so that the numerical apertures NA1 and NA2 of the optical fibers 10 and 11 are close to each other. At this time, it is desirable to make the numerical apertures NA1 and NA2 of the optical fibers 10 and 11 coincide on the connection surfaces 10a and 11a.
In FIG. 1, optical fibers 10 and 11 are provided with a cladding 13 around a core 12. As the optical fibers 10 and 11, it is desirable to use multimode optical fibers.

開口数（ＮＡ；Numerical Aperture）とは、光ファイバの光を集める能力を示すものであり、図２に示すように、一般に、開口数ＮＡは、ＮＡ＝ｓiｎθであらわされる。ここで、θは受入角２θの半分の角度である。
図２（Ａ）は低い開口数を有する光ファイバ１０に対する受入角θおよび光の反射の状態を示す断面図で、図２（Ｂ）は高い開口数を有する光ファイバ１１に対する受入角θおよび光の反射の状態を示す断面図である。 The numerical aperture (NA) indicates the ability of the optical fiber to collect light, and as shown in FIG. 2, the numerical aperture NA is generally expressed as NA = sin θ. Here, θ is half of the acceptance angle 2θ.
FIG. 2A is a cross-sectional view showing the acceptance angle θ and the light reflection state for the optical fiber 10 having a low numerical aperture, and FIG. 2B is the acceptance angle θ and the light for the optical fiber 11 having a high numerical aperture. It is sectional drawing which shows the state of reflection.

図３は、本発明に係る光ファイバの接続方法を実行する装置の概略構成図である。
図に示すように、両光ファイバ１０、１１の接続面１０ａ、１１ａを加熱するための、例えば電磁誘導加熱炉１４が設けられており、この電磁誘導加熱炉１４を制御する制御部１５を有している。両接続面１０ａ、１１ａは電磁誘導加熱炉１４の位置に位置決めされる。 FIG. 3 is a schematic configuration diagram of an apparatus for executing the optical fiber connection method according to the present invention.
As shown in the figure, for example, an electromagnetic induction heating furnace 14 is provided for heating the connection surfaces 10a and 11a of both optical fibers 10 and 11, and a control unit 15 for controlling the electromagnetic induction heating furnace 14 is provided. is doing. Both connection surfaces 10 a and 11 a are positioned at the position of the electromagnetic induction heating furnace 14.

図４（Ａ）には、コア１２の径が異なる光ファイバ１０、１１の接続面１０ａ、１１ａを合わせた状態が示してある。また、図４（Ｂ）には、細いコア１２径を有する光ファイバ１０のコア１２を予め熱拡散で拡径して拡径部１２ａを作成しておき、太い方のコア１２径を有する光ファイバ１１と接続面１０ａ、１１ａを突き合わせた状態が示してある。このとき、同時に開口数ＮＡについても同様に調整して、接続面１０ａ、１１ａにおいて近づけるか一致させるようにするのが望ましい。   FIG. 4A shows a state in which the connection surfaces 10a and 11a of the optical fibers 10 and 11 having different core 12 diameters are combined. In FIG. 4B, the core 12 of the optical fiber 10 having the thin core 12 diameter is expanded in advance by thermal diffusion to create the expanded diameter portion 12a, and the light having the thick core 12 diameter. A state in which the fiber 11 and the connection surfaces 10a and 11a are abutted is shown. At this time, it is desirable to adjust the numerical aperture NA in the same manner so that the connection surfaces 10a and 11a approach or coincide with each other.

すなわち、コア１２への熱付与によってコア１２径を拡大することができること、および開口数ＮＡが大きな光ファイバについては、加熱によりコア１２の屈折率自体がドーパント拡散によってそのピーク値を下げることができることは実験的に確認されている。
従って、コア１２径が細い方の光ファイバとして開口数ＮＡが大きいものを用いることにより、熱付与によって、コア１２の径拡大と同時にコア１２の屈折率を下げる（すなわち開口数ＮＡを下げる）ことができるので、接続前の処理が容易になる。なお、加熱融着の際の熱拡散によるコア１２の拡径および開口数ＮＡの低下により、両光ファイバ１０、１１の接続面におけるコア１２径および開口数ＮＡが一致するように、コア径および開口数ＮＡの初期値を設計しておけばよい。 That is, the diameter of the core 12 can be enlarged by applying heat to the core 12, and the optical fiber having a large numerical aperture NA can reduce the peak value of the refractive index of the core 12 by dopant diffusion due to heating. Has been confirmed experimentally.
Accordingly, by using an optical fiber having a smaller core 12 diameter and a larger numerical aperture NA, by applying heat, the refractive index of the core 12 is lowered at the same time as the diameter of the core 12 is increased (that is, the numerical aperture NA is lowered). Therefore, processing before connection becomes easy. It should be noted that the core diameter and the numerical aperture NA on the connecting surfaces of both optical fibers 10 and 11 are matched by the expansion of the core 12 and the decrease of the numerical aperture NA due to thermal diffusion during heat fusion. The initial value of the numerical aperture NA may be designed.

拡径部１２ａの拡径の勾配およびドーパントの拡散による開口数ＮＡの調整等は、例えば電磁誘導炉１４を制御して温度勾配を設定して行うことができる。
なお、図４においては、コア１２径が異なる光ファイバ１０、１１について接続する場合を示してあるが、コア１２径が同じ場合にも同様に適用できる。この場合には、前述した拡径部１２を設ける必要はないが、開口数ＮＡの調整は行うのが望ましい。 The adjustment of the numerical aperture NA by expanding the diameter of the enlarged diameter portion 12a and the diffusion of the dopant can be performed by controlling the electromagnetic induction furnace 14 to set the temperature gradient, for example.
Although FIG. 4 shows a case where the optical fibers 10 and 11 having different core 12 diameters are connected, the present invention can be similarly applied to the case where the core 12 diameters are the same. In this case, it is not necessary to provide the aforementioned enlarged diameter portion 12, but it is desirable to adjust the numerical aperture NA.

図５は、ＴＥＣによるコア径３０μｍの光ファイバのコアにおける屈折率分布の変化を示すグラフである。縦軸は比屈折率差Δｎ、横軸は光ファイバの中心からの距離（すなわち半径）であり、加熱開始からの時間（０→２００秒）における比屈折率差の分布を２０秒ごとに示してある。
図５からわかるように、まず初期の屈折率分布として、Ｒ＝１５μｍのところでステップ状に矩形の分布を出発点（ｔ＝０）としたが、加熱時間の経過とともに、矩形分布からガウシアン分布に近づいていることがわかる。比屈折率差Δｎは、半径位置０（すなわち光ファイバの中心軸）のところの屈折率が減少していることから、ドーパントの熱拡散とともに減少する傾向があることがわかる。一方、時間の経過とともに、Ｒ＝１５μｍの外側にも屈折率が上昇する部分が広がっており、モードフィールド径の拡大傾向が読み取れる。 FIG. 5 is a graph showing changes in the refractive index distribution in the core of an optical fiber having a core diameter of 30 μm by TEC. The vertical axis is the relative refractive index difference Δn, the horizontal axis is the distance from the center of the optical fiber (that is, the radius), and the distribution of the relative refractive index difference in the time from the start of heating (0 → 200 seconds) is shown every 20 seconds. It is.
As can be seen from FIG. 5, as an initial refractive index distribution, a rectangular distribution in a stepped manner is used as a starting point (t = 0) at R = 15 μm, but as the heating time elapses, the rectangular distribution changes to a Gaussian distribution. You can see that you are approaching. It can be seen that the relative refractive index difference Δn tends to decrease with the thermal diffusion of the dopant because the refractive index at the radial position 0 (that is, the central axis of the optical fiber) decreases. On the other hand, with the passage of time, the portion where the refractive index rises also spreads outside of R = 15 μm, and the expansion tendency of the mode field diameter can be read.

以上、前述した光ファイバの接続方法によれば、光ファイバ１０、１１同士を接続する際に、両接続面１０ａ、１１ａを突き合わせて加熱融着するが、このとき、開口数ＮＡが大きい方の光ファイバ１０のコア１２のドーパントを拡散させるように加熱することにより両光ファイバ１０、１１の開口数ＮＡを近づけることができるので、開口数ＮＡが異なる光ファイバ同士を低接続損失で接続することができることになる。
（実施例） As described above, according to the optical fiber connection method described above, when connecting the optical fibers 10 and 11, the connection surfaces 10a and 11a are abutted and heat-sealed. At this time, the one with the larger numerical aperture NA is used. By heating so that the dopant of the core 12 of the optical fiber 10 is diffused, the numerical apertures NA of the optical fibers 10 and 11 can be made closer, so that optical fibers having different numerical apertures NA can be connected with low connection loss. Will be able to.
(Example)

具体例として、図４に示すように、通常の汎用光ファイバ１１と、この汎用光ファイバ１１に比べてコア１２径が小さいと同時に開口数ＮＡが大きい光ファイバ１０との接続を行う場合について説明する。このような細径な光ファイバ１０とは、曲げに強い光ファイバであり、小さな配線領域に小径で曲げて布設できるメリットがある。この光ファイバ１０を汎用光ファイバ１１と接続する場所で、光ファイバ１０の接続部を予め熱拡散でコア１２径および開口数ＮＡを局所的に整合させておくことにより、低損失で汎用光ファイバ１１と接続することができる。汎用光ファイバ１１は、コア径５０μｍ、比屈折率差が１．０％であるが、細径な光ファイバ１０としては、コア径３０μｍ、比屈折率差を１．５％程度のものを用いるとちょうどよい。
このように、細径な光ファイバ１０として開口数ＮＡが大きな光ファイバを用いることにより、加熱により拡径させるとともに開口数ＮＡを低下することができるので、太径で開口数ＮＡが小さな汎用の光ファイバ１１と小さい接続損失で接続することができる。 As a specific example, as shown in FIG. 4, a description will be given of a case where a normal general-purpose optical fiber 11 is connected to an optical fiber 10 having a smaller core 12 diameter and a larger numerical aperture NA than the general-purpose optical fiber 11. To do. Such a small-diameter optical fiber 10 is an optical fiber that is resistant to bending, and has an advantage that it can be bent and installed in a small wiring area with a small diameter. By connecting the optical fiber 10 to the general-purpose optical fiber 11 at a location where the core 12 diameter and the numerical aperture NA are locally matched in advance by thermal diffusion, the general-purpose optical fiber can be obtained with low loss. 11 can be connected. The general-purpose optical fiber 11 has a core diameter of 50 μm and a relative refractive index difference of 1.0%, but the thin optical fiber 10 has a core diameter of 30 μm and a relative refractive index difference of about 1.5%. And just right.
Thus, by using an optical fiber having a large numerical aperture NA as the thin optical fiber 10, the diameter can be increased by heating and the numerical aperture NA can be reduced. The optical fiber 11 can be connected with a small connection loss.

本発明の光ファイバの接続方法の実施形態は、前述した前提においては、開口数ＮＡが互いに異なる光ファイバ１０、１１同士を直接接続した場合について説明したが、さらに、前述した光ファイバの接続方法により接続された光ファイバを接続部で切断し、それぞれに光コネクタを装着して、光コネクタにより接続する。このようにしても、接続面において開口数ＮＡが近いかもしくは同じ光ファイバ同士を接続することになるので、低接続損失で接続することができるとともに、容易に切り離すこともできる。 In the embodiment of the optical fiber connection method of the present invention, the case where the optical fibers 10 and 11 having different numerical apertures NA are directly connected to each other has been described based on the above-mentioned premise. the connected optical fiber is cut at the junction result, the optical connector is attached to each, to connect the optical connectors. Even in this case, optical fibers having close numerical apertures NA or the same optical fibers are connected to each other on the connection surface, so that they can be connected with low connection loss and can be easily separated.

以上のように、本発明に係る光ファイバの接続方法は、開口数が大きい方の光ファイバのコアのドーパントを拡散させるように加熱して融着させることにより、両光ファイバの開口数を近づけることができるので、開口数が異なる光ファイバ同士を低接続損失で接続することができるという効果を有し、開口数やコアの外径が互いに異なる光ファイバ同士を接続することができる光ファイバの接続方法等として有用である。   As described above, in the optical fiber connection method according to the present invention, the numerical apertures of both optical fibers are made closer by heating and fusing so as to diffuse the dopant of the core of the optical fiber having the larger numerical aperture. Therefore, optical fibers having different numerical apertures can be connected with low connection loss, and optical fibers having different numerical apertures and core outer diameters can be connected. This is useful as a connection method.

本発明の前提となる光ファイバの接続方法に係る実施形態を示す断面図である。It is sectional drawing which shows embodiment which concerns on the connection method of the optical fiber used as the premise of this invention. （Ａ）は開口数が小さな光ファイバを示す断面図である。（Ｂ）は開口数が大きな光ファイバを示す断面図である。(A) is sectional drawing which shows an optical fiber with a small numerical aperture. (B) is sectional drawing which shows an optical fiber with a large numerical aperture. 本発明に係る光ファイバの接続方法を実行する接続装置の概略構成図である。It is a schematic block diagram of the connection apparatus which performs the connection method of the optical fiber which concerns on this invention. （Ａ）はコア径が互いに異なる光ファイバ同士の接続前の状態を示す断面図である。（Ｂ）は（Ａ）により接続した接続部を示す断面図である。(A) is sectional drawing which shows the state before the connection of the optical fibers from which core diameters mutually differ. (B) is sectional drawing which shows the connection part connected by (A). ＴＥＣによる光ファイバのコアにおける屈折率分布の変化を示すグラフである。It is a graph which shows the change of the refractive index distribution in the core of the optical fiber by TEC. 従来の光ファイバの接続方法を示す断面図である。It is sectional drawing which shows the connection method of the conventional optical fiber.

符号の説明Explanation of symbols

１０、１１ 光ファイバ
１０ａ、１１ａ 接続面
１２ コア
ＮＡ 開口数 10, 11 Optical fiber 10a, 11a Connection surface 12 Core NA Numerical aperture

Claims (6)

光ファイバ同士を接続する光ファイバの接続方法であって、
開口数が異なる前記光ファイバの接続面を突き合わせて加熱融着し、開口数が大きい方の光ファイバのコアのドーパントを拡散させて、両光ファイバの開口数を近づけるように接続した後、融着接続された前記光ファイバを、接続部で切断し、切断されたそれぞれの光ファイバに光コネクタを装着して光ファイバ同士を接続することを特徴とする光ファイバの接続方法。 An optical fiber connection method for connecting optical fibers,
Numerical aperture against the connecting surface of different said optical fiber and thermal bonding, by diffusing the dopant of the core of the optical fiber towards the numerical aperture is large, after connection to close the aperture of the optical fibers, fusion A method of connecting optical fibers, wherein the optical fibers that have been connected and connected are cut at connection portions, optical connectors are attached to the cut optical fibers, and the optical fibers are connected to each other . 前記両光ファイバの開口数を接続面において一致させることを特徴とする請求項１に記載の光ファイバの接続方法。   The optical fiber connection method according to claim 1, wherein the numerical apertures of the two optical fibers are matched on the connection surface. 前記両光ファイバのコア径が互いに異なることを特徴とする請求項１または請求項２に記載の光ファイバの接続方法。   The optical fiber connection method according to claim 1, wherein the core diameters of the two optical fibers are different from each other. 前記コア径が小さい方の光ファイバの開口数が、コア径が大きい方の光ファイバの開口数よりも大きいことを特徴とする請求項３に記載の光ファイバの接続方法。   The optical fiber connection method according to claim 3, wherein the numerical aperture of the optical fiber having the smaller core diameter is larger than the numerical aperture of the optical fiber having the larger core diameter. 前記両光ファイバのコア径が同じことを特徴とする請求項１または請求項２に記載の光ファイバの接続方法。   The optical fiber connecting method according to claim 1 or 2, wherein the core diameters of the two optical fibers are the same. 前記両光ファイバは、マルチモード光ファイバであることを特徴とする請求項１から請求項５のいずれかに記載の光ファイバの接続方法。 The optical fiber connection method according to claim 1 , wherein the both optical fibers are multimode optical fibers .
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