JPH0456907A - Optical fiber coupler - Google Patents
Optical fiber couplerInfo
- Publication number
- JPH0456907A JPH0456907A JP16773690A JP16773690A JPH0456907A JP H0456907 A JPH0456907 A JP H0456907A JP 16773690 A JP16773690 A JP 16773690A JP 16773690 A JP16773690 A JP 16773690A JP H0456907 A JPH0456907 A JP H0456907A
- Authority
- JP
- Japan
- Prior art keywords
- optical fiber
- refractive index
- fiber coupler
- core
- wavelength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 99
- 238000005253 cladding Methods 0.000 claims description 10
- 230000004927 fusion Effects 0.000 abstract description 5
- 230000008878 coupling Effects 0.000 description 22
- 238000010168 coupling process Methods 0.000 description 22
- 238000005859 coupling reaction Methods 0.000 description 22
- 239000000835 fiber Substances 0.000 description 16
- 230000005540 biological transmission Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 238000009826 distribution Methods 0.000 description 7
- 230000003287 optical effect Effects 0.000 description 5
- 238000004891 communication Methods 0.000 description 4
- 230000006866 deterioration Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000002457 bidirectional effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
Abstract
Description
【発明の詳細な説明】
「産業上の利用分野」
この発明は、複数本の光ファイバを伝搬する伝搬モード
間に電磁波的な結合を起こさせて、先の合流、分岐、合
波、分波などの光結合を行う光ファイバカプラに関する
。光ファイバカプラは、光フアイバ通信系や光フアイバ
センサなどの光ファイバを用いたシステムに使用され、
光フアイバ通信系においては、双方向波長多重通信、単
方向波長多重通信、複数の光送信機からの出力の合波、
複数の受信機への光信号の分配など種々の用途に使用さ
れる。[Detailed Description of the Invention] "Industrial Application Field" This invention causes electromagnetic coupling between propagation modes propagating through a plurality of optical fibers, and combines, branches, multiplexes, and demultiplexes. This invention relates to optical fiber couplers that perform optical coupling. Optical fiber couplers are used in systems using optical fibers, such as optical fiber communication systems and optical fiber sensors.
In optical fiber communication systems, bidirectional wavelength multiplexing communication, unidirectional wavelength multiplexing communication, multiplexing of outputs from multiple optical transmitters,
It is used for various purposes such as distributing optical signals to multiple receivers.
「従来の技術」
第１６図は、従来の融着延伸型の光ファイバカプラの一
例を示すものである。この光ファイバカプラ１は、２本
の光ファイバ２．２を平行に並べ、それらの一部を加熱
融着し、さらに融着部分を延伸して融着延伸部３（光結
合部）を形成して構成されている。"Prior Art" FIG. 16 shows an example of a conventional fusion-stretching type optical fiber coupler. This optical fiber coupler 1 arranges two optical fibers 2.2 in parallel, heat-fuses a part of them, and further stretches the fused part to form a fused and stretched part 3 (optical coupling part). It is configured as follows.
この光ファイバ２としては、第１４図に示すようにコア
４の屈折率分布がステップ型の先ファイバが用いられて
いる。また時には第１５図に示すような階段型屈折率分
布の先ファイバも用いられる。As this optical fiber 2, a fiber whose core 4 has a stepped refractive index distribution is used as shown in FIG. Further, a tip fiber having a stepped refractive index distribution as shown in FIG. 15 is sometimes used.
この光ファイバｌにおけるコア４は、５ｉＯｙにＧ ｅ
Ｏｘをドープした材料からなっている。またコア４の
周囲のクラッド５の材料はＳｉｎ、が用いられている。The core 4 in this optical fiber l is 5iOy G e
It is made of a material doped with Ox. Furthermore, the material of the cladding 5 surrounding the core 4 is Sin.
「発明が解決しようとする課題」
しかしながら、このような光ファイバ２を用いて光フア
イバカプラｌを作製すると、一般には、十分に延伸して
コア４を細めないと、各ファイバのモード間の結合が生
じないので、融着延伸部３の形状は、第１３図に示すよ
うに元のファイバ径よりはかなり細くなる。具体的には
、外径１２５μｍの光ファイバがおよそ２０〜３０μｍ
程度になるまで細められる。"Problems to be Solved by the Invention" However, when an optical fiber coupler l is produced using such an optical fiber 2, in general, unless the core 4 is thinned by sufficiently stretching, the coupling between the modes of each fiber will be reduced. Since this does not occur, the shape of the fused and stretched portion 3 becomes considerably thinner than the original fiber diameter, as shown in FIG. Specifically, an optical fiber with an outer diameter of 125 μm is approximately 20 to 30 μm
It is narrowed down to a certain degree.
この結果、融着延伸部３の補強に格段の注意を払わない
と、安定な光結合特性を得ることが出来なくなる。すな
わち、融着延伸部３に生じた僅かな曲がりが、光フアイ
バカプラ１の挿入損失を高めたり、結合度の波長依存性
を変化させてしまうことになる。また、急激に細められ
た融着延伸部３では、光ファイバ２のコア４の中心線は
、第１７図に示すように曲がりを生しており、その結果
、光ファイバカプラの特性が悪化してしまう。As a result, unless special attention is paid to reinforcing the fused and stretched portion 3, stable optical coupling characteristics cannot be obtained. That is, the slight bend that occurs in the fused and stretched portion 3 increases the insertion loss of the optical fiber coupler 1 or changes the wavelength dependence of the degree of coupling. Furthermore, in the rapidly narrowed fusion-stretching section 3, the center line of the core 4 of the optical fiber 2 is bent as shown in FIG. 17, and as a result, the characteristics of the optical fiber coupler deteriorate. It ends up.
本発明は、上記事情に鑑みてなされたもので、融着延伸
部を形成する際の延伸量を余り大きくすることなく、各
光ファイバのモード間の結合を生じさせ、融着延伸部の
変形を最小限としに光ファイバカプラの提供を目的とし
ている。The present invention has been made in view of the above circumstances, and it is possible to cause coupling between the modes of each optical fiber without increasing the amount of stretching when forming the fused and stretched portion, and to deform the fused and stretched portion. The aim is to provide an optical fiber coupler with a minimum of
「課題を解決するための手段」
この発明は、中心部のコアの外側に、クラットよりも屈
折率の高いリング状高屈折率層が１層以上形成されてな
る複数本の光ファイバの一部に、融着延伸部を形成して
光ファイバカプラを構成し、これによって上記課題を解
消した。"Means for Solving the Problems" This invention provides a part of a plurality of optical fibers in which one or more ring-shaped high refractive index layers having a higher refractive index than the crut are formed on the outside of a central core. Additionally, an optical fiber coupler was constructed by forming a fused and stretched portion, thereby solving the above problem.
また、上記構成の光ファイバカプラの端末に、２次モー
ドのカットオフ波長が、使用する光の波長よりも実質的
に短い単一モード光ファイバを接続して光フアイバカプ
ラを構成するのが望ましい。Furthermore, it is desirable to configure an optical fiber coupler by connecting a single mode optical fiber whose secondary mode cutoff wavelength is substantially shorter than the wavelength of the light used to the terminal of the optical fiber coupler having the above configuration. .
「作用 鷹
コア中心層の外側にリング状高屈折率層が存在すると、
モードのパワーは、このリング状の高屈折率層に引きず
られ、モードの広がりが大きくなり、各光ファイバのモ
ード間の結合が強められ、従来のものよりも少ない延伸
量でもモード間の結合を起こさせることができる。``Effect: When a ring-shaped high refractive index layer exists outside the central layer of the hawk core,
The power of the mode is dragged by this ring-shaped high refractive index layer, which increases the spread of the mode and strengthens the coupling between the modes of each optical fiber. You can make it happen.
また、このようにコアの外側にクラッドよりも屈折率の
高い層を設けた光ファイバは、原理的に２次モードが発
生し、これにより伝送特性の劣化を引き起こすことが考
えられる。これを防止するには、上記光ファイバカプラ
の端末に、伝送で使用する光の波長よりも２次モードの
カットオフ波長が短い単一モード光ファイバを接続する
ことにより、２次モードの伝搬を防止することができる
。Further, in an optical fiber in which a layer having a higher refractive index than the cladding is provided outside the core, a secondary mode is generated in principle, which may cause deterioration of transmission characteristics. To prevent this, the propagation of the secondary mode can be prevented by connecting a single mode optical fiber with a cutoff wavelength of the secondary mode shorter than the wavelength of the light used for transmission to the terminal of the optical fiber coupler. It can be prevented.
「実施例」
第１図ないし第３図は、この発明の一実施例を示すもの
で、図中符号１１は、光フアイバカプラである。この光
ファイバカプラ１１は、中心部のコア１２の外側に、ク
ラッド１３よりも屈折率の高い高屈折率層１４が形成さ
れて多層構造をなす光ファイバ１５を、２本手行に並べ
、その一部に融着延伸部１６を形成して構成されている
。Embodiment FIGS. 1 to 3 show an embodiment of the present invention, and reference numeral 11 in the figures indicates an optical fiber coupler. This optical fiber coupler 11 has two optical fibers 15 arranged in a row, each having a multilayer structure in which a high refractive index layer 14 having a higher refractive index than a cladding 13 is formed on the outside of a central core 12. It is constructed by forming a fused and stretched portion 16 in a part.
この光ファイバを用いて光フアイバカプラ１１を作製し
た時のモードの定性的な振舞いを説明すると、第２図に
示すように、光ファイバ１５が延伸を受けていない場合
には、コア１２の中心層のみにモードのパワーＰが集中
しており、その外側のリング状の高屈折率層１４は、光
ファイバ１５の伝送特性に影響を与えていない。この先
ファイバ１５が融着延伸されて細められた融着延伸部１
６では、第３図に示すように、コア中心層に集中してい
ｆこパワーＰが外側に広がっている。このとき、コア１
２の外側にクラッド１３よりも屈折率の高い高屈折率層
１４が存在すると、モードのパワーＰはこの高屈折率層
１４に引きずられ、より広かろうとする。すなわち、い
わゆる単峰性のコア、例えば、単純なステップ型屈折率
分布と比へ、延伸時のモードの広がりが大きくなり、２
つのコアのモード間の結合が強化される。To explain the qualitative behavior of the mode when the optical fiber coupler 11 is manufactured using this optical fiber, as shown in FIG. 2, when the optical fiber 15 is not stretched, the center of the core 12 is The mode power P is concentrated only in the layer, and the ring-shaped high refractive index layer 14 outside the layer does not affect the transmission characteristics of the optical fiber 15. Fused and drawn portion 1 where the fiber 15 is fused and drawn to be narrowed.
6, as shown in FIG. 3, the power P is concentrated in the central layer of the core and spreads outward. At this time, core 1
If a high refractive index layer 14 having a higher refractive index than the cladding 13 is present outside the cladding 13, the mode power P is dragged by the high refractive index layer 14 and tends to become wider. In other words, for a so-called unimodal core, for example, a simple step-type refractive index distribution and ratio, the mode broadening during stretching increases, and 2
The coupling between the two core modes is strengthened.
なお、本実施例では、第４図（ａ）に示すように中心部
のコア１２の外側に、クラッド１３より屈折率の高い高
屈折率層１４を１層形成した光ファイバ１５を用いたが
、高屈折率層１４は１層に限定されることなく第４図（
ｂ）に示すように２層、もしくはそれ以上形成しても良
い。In this example, as shown in FIG. 4(a), an optical fiber 15 was used in which one high refractive index layer 14 having a higher refractive index than the cladding 13 was formed outside the core 12 at the center. , the high refractive index layer 14 is not limited to one layer, but is shown in FIG.
As shown in b), two or more layers may be formed.
コア１２の外側に高屈折率層１４を形成した光ファイバ
１５を用いて形成された光ファイバカプラ１１は、結合
度の波長依存性が、第５図に示すように平坦なものとす
ることが可能である。このような光ファイバカプラは一
般にＷＩＣ型カプラ（Ｗａｖｅｌｅｎｇｔｈ Ｉｎｄ
ｅｐｅｎｄｅｎｔＣｏｕｐｌｅｒ）と呼称されている。The optical fiber coupler 11 formed using the optical fiber 15 in which the high refractive index layer 14 is formed on the outside of the core 12 can have a flat wavelength dependence of the degree of coupling as shown in FIG. It is possible. Such optical fiber couplers are generally WIC type couplers (Wavelength Ind.
(ependentCoupler).
上記光ファイバ１５を用いてＷＩＣ型光ファイバカプラ
が得られ４原因は、光ファイバカプラの結合を決定する
次式（１）において、このような屈折率分布を採用する
ことによって、２本の光ファイバのモードの重なりを示
す項が、光の波長に比例するような特性を有するように
なり、結果として波長依存性が相殺されているものと考
えられる。The reason why a WIC type optical fiber coupler is obtained using the above optical fiber 15 is that in the following equation (1) that determines the coupling of the optical fiber coupler, by adopting such a refractive index distribution, two light beams are It is considered that the term indicating the overlap of the fiber modes has a characteristic that is proportional to the wavelength of light, and as a result, the wavelength dependence is canceled out.
４に’ Ｓ φａ’ｄｓ ５ φｂ’ｄｓたたし、
ξ 第１図に示す各ボートのうちボート■−ボート■
への結合を表す式
％式％
ｇ・カブラ結合部の長さ、
φａ、φｂ：ファイバａ、ファイバｂの電磁界強変分布
φａ（ｘ、ｙ）、φｂ（ｘ、ｙ）。（なお座標は第６図
に示すように設定する）
ｄｓ ＝ ｄｘ−ｄｙ
ｋ＝２π／λ （λは波長）
Ｂａ、Ｂｂ： コアａ、コアｂの間に結合がないときの
伝搬定数
第７図は、この発明の他の実施例を示すものである。こ
の実施例による光ファイバカプラ２１は、先の実施例の
光ファイバカプラ１１の端部２２・・・に、伝送で使用
する光の波長よりも２次モードのカットオフ波長が短い
単一モード光ファイバ２３を接続して構成されている。4' S φa'ds 5 φb'ds and ξ Boat ■ - Boat ■ of each boat shown in Figure 1
Expression expressing coupling to %Formula %g・Length of Kabra coupling part, φa, φb: Strong electromagnetic field distribution φa (x, y), φb (x, y) of fiber a and fiber b. (The coordinates are set as shown in Figure 6) ds = dx-dy k = 2π/λ (λ is the wavelength) Ba, Bb: Propagation constant No. 7 when there is no coupling between core a and core b The figure shows another embodiment of the invention. The optical fiber coupler 21 according to this embodiment has a single mode light having a cutoff wavelength of the secondary mode shorter than the wavelength of the light used for transmission at the end 22 of the optical fiber coupler 11 of the previous embodiment. It is configured by connecting fibers 23.
上述した光ファイバカプラ１１は、コア１２の外側に、
クラッド１３よりも屈折率の高いリング状の高屈折率層
１４を設けた２本の光ファイバ１５に融着延伸部１６を
形成して構成した。しかし、この光ファイバ１５は、原
理的に２次モードの発生が伝送特性の劣化を引き起こす
ことが考えられる。The optical fiber coupler 11 described above has a
A fused and stretched portion 16 was formed on two optical fibers 15 provided with a ring-shaped high refractive index layer 14 having a higher refractive index than the cladding 13. However, in principle, it is conceivable that the generation of a secondary mode in this optical fiber 15 causes deterioration of the transmission characteristics.
本実施例の光ファイバカプラ２１は、上記光ファイバカ
プラ１１の端末２２・・に、伝送で使用する光の波長よ
りも２次モードのカットオフ波長か短い単一モード光フ
ァイバ２３・・・を接続し、２次モードの伝搬を防止す
るものなので、伝送特性の劣化を防止することができる
。The optical fiber coupler 21 of this embodiment connects the single mode optical fibers 23 to the terminals 22 of the optical fiber coupler 11 with a cutoff wavelength of the secondary mode shorter than the wavelength of the light used for transmission. Since the connection prevents propagation of the secondary mode, deterioration of transmission characteristics can be prevented.
（実験例１）
コア径９μｍ１高屈折率層の内側径５０μｍ、高屈折率
層の外側径６０μｍ１ コアの比屈折率差０３２％、高
屈折率層の比屈折率差ｏ、１２％、ファイバ外径１２５
μｍのパラメータの光ファイバ１５を２本用い、第８図
に示すようにこれらの光ファイバ】５の被覆１７を一部
除去し、それぞれの光ファイバ裸線１８を平行に並べて
密着状態とし、次に、この光ファイバ裸線１８を酸水素
バーナ１９で加熱して第９図に示すように融着させ、更
に、各光ファイバ１５を離間する方向（第１０図中矢印
で示す）に延伸して融着延伸部１６を形成して光ファイ
バカプラを作製した。(Experiment Example 1) Core diameter 9 μm1 Inner diameter of high refractive index layer 50 μm, Outer diameter of high refractive index layer 60 μm1 Relative refractive index difference of core 032%, relative refractive index difference o of high refractive index layer 12%, outside fiber Diameter 125
Using two optical fibers 15 with parameters of .mu.m, as shown in FIG. Next, the bare optical fibers 18 are heated with an oxyhydrogen burner 19 to fuse them as shown in FIG. 9, and are further stretched in the direction to separate the optical fibers 15 (indicated by the arrows in FIG. 10). An optical fiber coupler was produced by forming a fused and stretched portion 16.
得られた光ファイバカプラの結合は比較的大きく、結合
度の波長依存性は、第１１図に示すように概略周期性を
示した。このグラフかられかるように、この光ファイバ
カプラのボート■に１，３μｍと１．５５μＭの２つの
波長の光を同時に入射すると、ボート■に１．５５μｍ
の光が、ボート■に１．３μｍの光がそれぞれ出射され
る。このような光ファイバカプラは、波長多重型カブラ
と呼称されている。第１２図は、作製された光ファイバ
カプラの融着延伸部１６の最も細い部分の断面を示すも
ので、この部分におけるファイバ径し、は４８μｍであ
った。The coupling of the obtained optical fiber coupler was relatively large, and the wavelength dependence of the coupling degree showed approximately periodicity as shown in FIG. As can be seen from this graph, when light with two wavelengths of 1.3 μm and 1.55 μM is simultaneously incident on the boat ■ of this optical fiber coupler, the wavelength of light of 1.55 μM is incident on the boat ■.
A light of 1.3 μm is emitted to the boat (2). Such an optical fiber coupler is called a wavelength multiplexing coupler. FIG. 12 shows a cross section of the thinnest portion of the fused and stretched portion 16 of the optical fiber coupler produced, and the fiber diameter at this portion was 48 μm.
（比較例）
一方、比較のために、コア径９μｍ１フアイバ径１２５
μｍの通常の単一モードファイバを用い、先の光ファイ
バカプラと同程度の結合特性を有する光ファイバカプラ
を作製し、その融着延伸部の最細径部分を観察したとこ
ろ、第１３図に示すように、先の実験例１のものに比べ
て融着延伸部の細りは急激になっており、この部分のフ
ァイバ径り、は２５μｍであった。したがって、この部
分にわずかな力が加わっても、曲がりや引っ張りに伴う
変形を受は易いことがわかる。(Comparative example) On the other hand, for comparison, core diameter 9 μm 1 fiber diameter 125
When we fabricated an optical fiber coupler with the same coupling characteristics as the previous optical fiber coupler using a normal single mode fiber of μm, we observed the smallest diameter part of the fused and stretched part, and the result is shown in Figure 13. As shown, the thinning of the fused and stretched portion was sharper than that of Experimental Example 1, and the fiber diameter in this portion was 25 μm. Therefore, it can be seen that even if a slight force is applied to this part, it is easily deformed due to bending or pulling.
（実験例２）
実験例１で用いた光ファイバを２本用意し、方の光ファ
イバの外径を、フッ素含有酸水素炎を用いた気相エツチ
ングにより１２５μｍから１１０μｍに細めた。この光
ファイバと、エツチングを施さない光ファイバとを平行
に並べ、実験例１と同様に融着、延伸を行って光ファイ
バカプラを作製した。得られた光ファイバカプラの結合
は比較的弱いものてあっ１こが、その結合度の波長依存
性の変化は非常に小さく、第５図に示すように、波長１
２μｍ＝１．６μｍの広い波長域にわたり、はぼ一定の
結合度を示し１こ。(Experimental Example 2) Two optical fibers used in Experimental Example 1 were prepared, and the outer diameter of the other optical fiber was reduced from 125 μm to 110 μm by gas phase etching using a fluorine-containing oxyhydrogen flame. This optical fiber and an unetched optical fiber were arranged in parallel and fused and stretched in the same manner as in Experimental Example 1 to produce an optical fiber coupler. Although the coupling of the obtained optical fiber coupler is relatively weak, the change in the wavelength dependence of the degree of coupling is very small, and as shown in Fig. 5, at wavelength 1
Over a wide wavelength range of 2 μm = 1.6 μm, the degree of coupling is approximately constant.
（実験例３）
実験例２で作製した光ファイバの端部に、コア径９μｍ
１ ファイバ径１２５μｍ、 ２次モードのカットオ
フ波長が１．４５μｍの単一モード光ファイバを接続し
、第７図に示す光ファイバカプラを作製した。(Experimental Example 3) A core diameter of 9 μm was attached to the end of the optical fiber produced in Experimental Example 2.
1 Single-mode optical fibers having a fiber diameter of 125 μm and a secondary mode cutoff wavelength of 1.45 μm were connected to fabricate an optical fiber coupler shown in FIG. 7.
得られ１こ光ファイバカプラの損失を測定しに結果、余
剰損失は０ 、１ ｄＢと低損失であったわ「発明の効
果」
以上説明したように、この発明では次のような効果を奏
する。We measured the loss of the obtained optical fiber coupler and found that the surplus loss was as low as 0.1 dB. ``Effects of the Invention'' As explained above, this invention has the following effects. .
中心部のコアの外側に、クラッドよりも屈折率の高いリ
ング状高屈折率層か１層以上形成されてなる複数本の光
ファイバを融着延伸して光ファイバカプラを構成したの
で、先ファイバのモードのパワーが高屈折率層に引きず
られ、その広がりが大きくなり、従来のものよりも少な
い延伸量てモード間の結合を起こさせることができ、融
着延伸部の変形が少なくなり、光ファイバカプラの特性
を向上させることができる。An optical fiber coupler is constructed by fusion-stretching multiple optical fibers each having one or more ring-shaped high refractive index layers with a higher refractive index than the cladding formed on the outside of the central core. The power of the mode is dragged by the high refractive index layer, and its spread becomes larger, allowing coupling between modes to occur with a smaller amount of stretching than conventional ones, reducing deformation of the fusion-stretched part, and increasing the amount of light. The characteristics of the fiber coupler can be improved.
また、上記構成の光ファイバカプラの端末に、２次モー
ドのカットオフ波長が、使用する光の波長よりし実質的
に短い単一モード晃ファイバを接続することによって、
２次モードの伝搬が防止されるので、伝送特性の劣化が
防止できる。Furthermore, by connecting a single mode optical fiber whose secondary mode cutoff wavelength is substantially shorter than the wavelength of the light used, to the terminal of the optical fiber coupler having the above configuration,
Since propagation of the secondary mode is prevented, deterioration of transmission characteristics can be prevented.
第１図ないし第３図は、この発明の一実施例を示すもの
で、第１図は光ファイバカプラの概略側面図、第２図は
、第１図のＡ−Ａ線断面の説明図、第３図は第１図のＢ
−Ｂ線断面の説明図、第４図は、この発明の光ファイバ
カプラにおいて好適な光ファイバの屈折率分布を例示す
るための概略図、第５図は、この発明に係わる光ファイ
バカプラの結合度の波長依存性の一例を示すグラフ、第
６１図は、カブラの結合を決定する式を説明するための
概略図、第７図は、この発明の他の実施例を示す概略側
面図、第８図ないし第１Ｏ図は、光ファイバカプラの製
造方法を工程順に説明するための図、第】１図は、この
発明に係わる実験例で作製した光ファイバカプラリ結合
度の波長依存性を示すグラフ、第１２図は、同じ光ファ
イバカプラの融着延伸部の説明図、第１３図は、比較例
の融着延伸部の説明図、第１４図ないし第１７図は、従
来例を説明するための図であって、第１４図および第１
５図は、従来の光ファイバカプラに使用される光ファイ
バの屈折率分布を例示するための図、第１６図は光ファ
イバカプラの概略側面図、第１７図は第１６図のＣ部拡
大図である。
１１．２１・・・・光ファイバカプラ、１２・・・・コ
ア、１３・・・・・クラッド、１４・・・・・・高屈折
率層、１５・・・・・・光ファイバ、１６・・・・・・
融着延伸部、２２・・・端部、２３・・・・単一モード
光ファイバ。1 to 3 show an embodiment of the present invention, in which FIG. 1 is a schematic side view of an optical fiber coupler, FIG. 2 is an explanatory diagram of a cross section taken along line A-A in FIG. Figure 3 is B of Figure 1.
4 is a schematic diagram illustrating the refractive index distribution of an optical fiber suitable for the optical fiber coupler of the present invention, and FIG. 5 is an explanatory diagram of the cross section of the optical fiber coupler of the present invention. FIG. 61 is a graph showing an example of the wavelength dependence of wavelength; FIG. Figures 8 to 1O are diagrams for explaining the manufacturing method of an optical fiber coupler in the order of steps, and Figure 1 shows the wavelength dependence of the coupling degree of the optical fiber coupler manufactured in an experimental example related to the present invention. Graph, FIG. 12 is an explanatory diagram of the fusion-stretching part of the same optical fiber coupler, FIG. 13 is an explanatory diagram of the fusion-stretching part of the comparative example, and FIGS. 14 to 17 are explanatory diagrams of the conventional example. 14 and 1.
Figure 5 is a diagram illustrating the refractive index distribution of an optical fiber used in a conventional optical fiber coupler, Figure 16 is a schematic side view of the optical fiber coupler, and Figure 17 is an enlarged view of section C in Figure 16. It is. 11.21... Optical fiber coupler, 12... Core, 13... Clad, 14... High refractive index layer, 15... Optical fiber, 16...・・・・・・
Fusion/stretching portion, 22... End portion, 23... Single mode optical fiber.
Claims (2)
高いリング状高屈折率層が１層以上形成されてなる複数
本の光ファイバの一部に、融着延伸部が形成されてなる
光ファイバカプラ。(1) A fused and stretched part is formed in a part of a plurality of optical fibers in which one or more ring-shaped high refractive index layers having a higher refractive index than the cladding are formed on the outside of the central core. An optical fiber coupler.
高いリング状高屈折率層が１層以上形成されてなる複数
本の光ファイバの一部に、融着延伸部が形成されてなる
光ファイバカプラの端末に、２次モードのカットオフ波
長が、使用する光の波長よりも実質的に短い単一モード
光ファイバを接続してなる光ファイバカプラ。(2) A fused and stretched part is formed in a part of a plurality of optical fibers in which one or more ring-shaped high refractive index layers having a higher refractive index than the cladding are formed on the outside of the central core. An optical fiber coupler in which a single mode optical fiber whose secondary mode cutoff wavelength is substantially shorter than the wavelength of the light used is connected to the terminal of the optical fiber coupler.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16773690A JPH0456907A (en) | 1990-06-26 | 1990-06-26 | Optical fiber coupler |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16773690A JPH0456907A (en) | 1990-06-26 | 1990-06-26 | Optical fiber coupler |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0456907A true JPH0456907A (en) | 1992-02-24 |
Family
ID=15855182
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16773690A Pending JPH0456907A (en) | 1990-06-26 | 1990-06-26 | Optical fiber coupler |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0456907A (en) |
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