JPS5934281B2 - single mode optical fiber - Google Patents
single mode optical fiberInfo
- Publication number
- JPS5934281B2 JPS5934281B2 JP52012684A JP1268477A JPS5934281B2 JP S5934281 B2 JPS5934281 B2 JP S5934281B2 JP 52012684 A JP52012684 A JP 52012684A JP 1268477 A JP1268477 A JP 1268477A JP S5934281 B2 JPS5934281 B2 JP S5934281B2
- Authority
- JP
- Japan
- Prior art keywords
- refractive index
- core
- single mode
- optical fiber
- mode optical
- 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.)
- Expired
Links
Classifications
-
- 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
- G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
- G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
- G02B6/03622—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 2 layers only
- G02B6/03633—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 2 layers only arranged - -
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
- Waveguides (AREA)
Description
【発明の詳細な説明】
本発明は外側石英管に含まれる不純物の影響を受けず、
曲りに強い単一モード光ファイバの構造に関するもので
ある。DETAILED DESCRIPTION OF THE INVENTION The present invention is not affected by impurities contained in the outer quartz tube;
This paper relates to the structure of a single mode optical fiber that is resistant to bending.
従来の単一モード光ファイバの屈折率分布は、第１図に
示すようになつており、ｎｌはコアの屈折率、ｎｏはク
ラッドの屈折率である。The refractive index distribution of a conventional single mode optical fiber is as shown in FIG. 1, where nl is the refractive index of the core and no is the refractive index of the cladding.
その電磁界分布は、コア径およびコアとクラッド間の屈
折率差によりきまる規格化周波数を２０として計算すれ
ば、第２図に示すような形になつていることがわかる。
第２図において、ａはコアの半径、にはクラッドの半径
であり、実線は従来の単一モード光ファイバにおける最
低次モードの電磁界分布を示す。If the electromagnetic field distribution is calculated by setting the normalized frequency determined by the core diameter and the refractive index difference between the core and the cladding to 20, it can be seen that the electromagnetic field distribution has a shape as shown in FIG. 2.
In FIG. 2, a is the radius of the core, a is the radius of the cladding, and the solid line shows the electromagnetic field distribution of the lowest mode in a conventional single mode optical fiber.
なお破線は本発明の単一モード光ファイバにおける最低
次モードの電磁界分布を示す。第２図から明らかなよう
に、電磁界の多くの部分が、クラッド部にしみ出してい
るので、クラッド部に含まれる不純物により吸収が生じ
、その損失が大きくなる。Note that the broken line indicates the electromagnetic field distribution of the lowest mode in the single mode optical fiber of the present invention. As is clear from FIG. 2, since a large portion of the electromagnetic field seeps into the cladding, absorption occurs due to impurities contained in the cladding, increasing the loss.
これを防ぐために、不純物を含まないクラッド層を厚く
作ることが考えられるが、作製［時間がかかるという欠
点がある。また曲りによる損失も電磁界分布に関係し、
中央部での電磁界分布が大きいほど曲りに対して強くな
る。In order to prevent this, it is conceivable to make a thick cladding layer that does not contain impurities, but this has the disadvantage that it takes a long time to make. The loss due to bending is also related to the electromagnetic field distribution.
The larger the electromagnetic field distribution in the center, the stronger it will be against bending.
しかし電磁界分布はファイバ構造に特有のものであり、
従来の単一モード光ファイバの構造では本質的にコアの
周辺部への電磁界分布の拡がりがある。ただコアとクラ
ッド間の屈折率差を大きくし、中央部への電磁界の集中
度を増すことは考えられるが、単一モードの条供を満た
すためには、コア径を小さくせねばならず、コア径を小
さくすると、ファイバ間の接続を考えた場合、接続損失
を小さくすることが困難であるという欠点がある。本発
明はこれらの欠点を除去するため、コアの中央部の屈折
率をコアの他の部分の屈折率より大きくしたもので、以
下図面について詳細に説明する。However, the electromagnetic field distribution is specific to the fiber structure;
In the structure of a conventional single mode optical fiber, the electromagnetic field distribution essentially spreads to the periphery of the core. However, it is conceivable to increase the concentration of the electromagnetic field in the center by increasing the refractive index difference between the core and the cladding, but in order to satisfy the requirements of a single mode, the core diameter must be reduced. However, when the core diameter is made small, it is difficult to reduce the connection loss when considering connections between fibers. In order to eliminate these drawbacks, the present invention makes the refractive index of the central part of the core larger than the refractive index of other parts of the core, and will be described in detail below with reference to the drawings.
第３図は本発明の単一モード光ファイバの屈折率分布の
一例を示す図であつて、Ｎ，はコアの中央部の屈折率を
示す。FIG. 3 is a diagram showing an example of the refractive index distribution of the single mode optical fiber of the present invention, where N indicates the refractive index at the center of the core.
第３図におけるコアとクラツド間の比屈折率差が隻（＝
？＝０．１９％であり、中央部のコアとクラツド間の比
屈折率差は凸〔コ？＝０．２８％である。The relative refractive index difference between the core and cladding in Figure 3 is
? = 0.19%, and the relative refractive index difference between the central core and the cladding is convex. =0.28%.
このようにコアの中央部の屈折率がコアの他の部分の屈
折率より大きくなつているので、光の電磁界分布は中央
部が強くなり、定性的には第２図に破線で示したように
、コアの外側のクラツド部への電磁界のしみだしが小さ
くなる。第４図は単一モード光フアイバの損失の波長特
性を示す図で、実線は本発明によるコアの中央部の屈折
率を大きくした単一モードフアイバの損失の波長特性を
示し、破線は従来の単一モード光フアイバの損失の波長
特性を示す。In this way, the refractive index at the center of the core is larger than the refractive index at other parts of the core, so the electromagnetic field distribution of light becomes stronger at the center, qualitatively as shown by the broken line in Figure 2. As a result, the leakage of the electromagnetic field to the cladding portion outside the core is reduced. FIG. 4 is a diagram showing the wavelength characteristic of loss in a single mode optical fiber, where the solid line shows the wavelength characteristic of loss in the single mode fiber with a large refractive index in the center of the core according to the present invention, and the broken line shows the wavelength characteristic of loss in the conventional fiber. The wavelength characteristics of the loss of a single mode optical fiber are shown.
第４図に示す本発明による構造をもつた単一モード光フ
アイバのコアはＧｅＯ，を添加したＳｉＯ，ガラスから
なり、そのコアとクラツド間の比屈折率差は０．１９％
で、不純物を含まないクラツド層の厚さは１７μｍであ
つた。またコア径は６．２μｍで、コアの中心部の比屈
折率差は０．２８％で、その幅は１．０ｔｔｍ程度であ
つた。第４図に破線で示した従来の構造をもつた単一モ
ードフアイバのコアとクラツド間の比屈折率差およびコ
ア径は本発明の実施例の場合と同一であり、不純物を含
まないクラツド層の厚さは２０μｍであつた。The core of the single mode optical fiber having the structure according to the present invention shown in FIG. 4 is made of SiO and glass doped with GeO, and the relative refractive index difference between the core and the cladding is 0.19%.
The thickness of the impurity-free cladding layer was 17 μm. The core diameter was 6.2 μm, the relative refractive index difference at the center of the core was 0.28%, and the width was about 1.0 ttm. The relative refractive index difference between the core and the cladding and the core diameter of the single mode fiber with the conventional structure shown by the broken line in FIG. The thickness was 20 μm.
第４図において、注目すべき点は本発明の実施例と従来
の構造をもつたものとでは、波長が０．９５μｍ付近に
おける損失が顕著に異なつていることである。この損失
の原因は前記不純物を含まないクラツドの外側のクラツ
ド部の石英に含まれる０Ｈ基（不純物）によるものであ
るが、本発明の単一モード光フアイバの不純物を含まな
いクラツド層の厚さ（１７μｍ）が従来の単一モード光
フアイバのそれ（２０μｍ）より薄いにもかかわらず、
０Ｈ基の影響を受けずに、本発明の実施例の方がその損
失が小さくなつている。また基本モードの次の次数のモ
ードの光の電磁界分布は第５図に示すように、コア内の
外側部において強いので、これ等のモードのカツトオフ
波長は主としてコア内の外側部の屈折率できまるから、
コアの中央部の屈折率を大きくさせても、単一モードの
条件を満たすためコア径を小さくする必要がない。実際
に測定した結果、カツトオフ波長は、従来の単一モード
光フアイバと本発明の単一モード光フアイバのいずれも
０．７μｍであつた。また曲り損失に関して測定した結
果は、本発明の単一モード光フアイバでは直径２０鰭の
曲りに対して波長１．０μｍで５ｄＢ／ターンであつた
が、従来の単一モード光フアイバでは７ｄＢ／ターンあ
つた。このことから曲りに対しても強いことが実証され
た。コアの中央部の屈折率をコアとクラツド間の屈折率
差の２倍以上だけコアの屈折率より大きくすると、単一
モード光フアイバの条件を満たすために、コア径とコア
とクラツド間の屈折率差によりきまるコア径より小さく
しなければならなかつた。What should be noted in FIG. 4 is that the loss at a wavelength around 0.95 μm is significantly different between the embodiment of the present invention and the conventional structure. The cause of this loss is due to the 0H group (impurity) contained in the quartz in the cladding part outside the impurity-free cladding, but the thickness of the impurity-free cladding layer of the single mode optical fiber of the present invention (17 μm) is thinner than that of conventional single mode optical fiber (20 μm).
The loss is smaller in the examples of the present invention without being affected by the 0H group. Furthermore, as shown in Figure 5, the electromagnetic field distribution of light in modes of the next order after the fundamental mode is strong in the outer part of the core, so the cutoff wavelength of these modes is mainly determined by the refractive index of the outer part of the core. Because it can be done,
Even if the refractive index of the central portion of the core is increased, there is no need to reduce the core diameter because the single mode condition is satisfied. As a result of actual measurements, the cutoff wavelength was 0.7 μm for both the conventional single mode optical fiber and the single mode optical fiber of the present invention. The bending loss of the single mode optical fiber of the present invention was 5 dB/turn at a wavelength of 1.0 μm for bending with a diameter of 20 fins, whereas that of the conventional single mode optical fiber was 7 dB/turn. It was hot. This proves that it is strong against bending. If the refractive index of the central part of the core is made larger than the refractive index of the core by more than twice the refractive index difference between the core and the cladding, the core diameter and the refraction between the core and the cladding can be adjusted to meet the requirements for a single mode optical fiber. It had to be smaller than the core diameter determined by the rate difference.
またコアの中央部の屈折率を前記屈折率差の１／１０以
下だけコアの屈折率より大きくした場合には、従来の単
一モード光フアイバと同様な結果となり、特に顕著な効
果はなかつた。また屈折率を大きくする部分の半径をコ
ア径の％以上とすると、単一モードになる波長が長波長
側にずれた。Furthermore, when the refractive index at the center of the core was made larger than the refractive index of the core by 1/10 or less of the refractive index difference, the results were similar to those of conventional single mode optical fibers, and there was no particularly significant effect. . Furthermore, when the radius of the portion where the refractive index is increased is greater than % of the core diameter, the wavelength at which the single mode becomes a single mode shifts to the longer wavelength side.
以上のことから、本発明の単一モード光フアイバのよう
な構造を有し、効果が期待できるのは、屈折率差に関し
ては１／１０〜２倍、その半径に関してはコア径の％以
下にする必要のあることがわかる。From the above, it can be seen that the effects of having a structure like the single mode optical fiber of the present invention can be expected when the refractive index difference is 1/10 to 2 times, and when the radius is less than % of the core diameter. I know what I need to do.
以上説明したように、本発明の単一モード光フアイバは
コアの中央部の屈折率をコアの他の部分の屈折率より大
きくすることにより、光の電磁界分布を中央に集中させ
るので、不純物を含まないクラツド層が薄くても、その
外側のクラツド部の石英ガラスの不純物の影響を受けず
、また曲りにも強い。As explained above, the single mode optical fiber of the present invention concentrates the electromagnetic field distribution of light at the center by making the refractive index of the central part of the core larger than the refractive index of other parts of the core. Even if the cladding layer that does not contain glass is thin, it is not affected by impurities in the quartz glass in the outer cladding part, and is resistant to bending.
またクラツド層を薄くすることができるので、単一モー
ド光フアイバの作製時間の短縮が可能であり、光通信へ
応用するためにも極めて有効である。Furthermore, since the cladding layer can be made thinner, the manufacturing time of a single mode optical fiber can be shortened, which is extremely effective for application to optical communications.
第１図は従来の単一モード光フアイバの屈折率分布の一
例を示す図、第２図は最低次のモードの電磁界分布を示
す図、第３図は本発明の単一モード光フアイバの屈折率
分布の一例を示す図、第４図は単一モード光フアイバの
損失の波長特性を示す図、第５図は基本モードの次の次
数のモードの光の電磁界分布を示す図である。
ｎ１・・・・・・コアの屈折率、ＮＯ・・・・・・クラ
ツドの屈折率、Ｎ２・・・・・・コアの中央部の屈折率
、ａ・・・・・・コアの半径、ｒ・・・・・・クラツド
の半径。FIG. 1 is a diagram showing an example of the refractive index distribution of a conventional single mode optical fiber, FIG. 2 is a diagram showing the electromagnetic field distribution of the lowest mode, and FIG. 3 is a diagram showing an example of the refractive index distribution of a conventional single mode optical fiber. Figure 4 is a diagram showing an example of refractive index distribution, Figure 4 is a diagram showing the wavelength characteristics of loss in a single mode optical fiber, and Figure 5 is a diagram showing the electromagnetic field distribution of light in the mode of the next order of the fundamental mode. . n1: refractive index of the core, NO: refractive index of the cladding, N2: refractive index of the center of the core, a: radius of the core, r...Radius of the cladding.
Claims (1)
ラス被覆体で、前記中心部のガラスを被覆してなる単一
モード光ファイバにおいて、前記中心部のガラスの中央
部で、前記中心部のガラスの半径の１／２より小さい半
径内の部分の屈折率を、前記中心部のガラスと前記ガラ
ス被覆体間の屈折率差の１／１０〜２倍だけ、前記中心
部のガラスの屈折率より大きくしたことを特徴とする単
一モード光ファイバ。1. In a single mode optical fiber formed by covering the glass in the center with a glass coating having a refractive index smaller than the refractive index of the glass in the center, The refractive index of a portion within a radius smaller than 1/2 of the radius of the glass is 1/10 to 2 times the refractive index difference between the glass at the center and the glass coating, and the refractive index of the glass at the center. A single mode optical fiber characterized by its larger size.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP52012684A JPS5934281B2 (en) | 1977-02-08 | 1977-02-08 | single mode optical fiber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP52012684A JPS5934281B2 (en) | 1977-02-08 | 1977-02-08 | single mode optical fiber |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5397849A JPS5397849A (en) | 1978-08-26 |
| JPS5934281B2 true JPS5934281B2 (en) | 1984-08-21 |
Family
ID=11812192
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP52012684A Expired JPS5934281B2 (en) | 1977-02-08 | 1977-02-08 | single mode optical fiber |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5934281B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60263103A (en) * | 1984-06-12 | 1985-12-26 | Shin Etsu Chem Co Ltd | Base material for optical fiber and its production |
| JPS6252508A (en) * | 1985-09-02 | 1987-03-07 | Nippon Telegr & Teleph Corp <Ntt> | Optical fiber |
| US4763976A (en) * | 1987-05-21 | 1988-08-16 | Corning Glass Works | Connector employing mode field modification |
| US5278931A (en) * | 1992-12-31 | 1994-01-11 | Corning Incorporated | Low bend loss singlemode optical waveguide fiber |
-
1977
- 1977-02-08 JP JP52012684A patent/JPS5934281B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5397849A (en) | 1978-08-26 |
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