JPH085856A - Quartz optical fiber and its production - Google Patents

Quartz optical fiber and its production

Info

Publication number
JPH085856A
JPH085856A JP6162835A JP16283594A JPH085856A JP H085856 A JPH085856 A JP H085856A JP 6162835 A JP6162835 A JP 6162835A JP 16283594 A JP16283594 A JP 16283594A JP H085856 A JPH085856 A JP H085856A
Authority
JP
Japan
Prior art keywords
softening temperature
optical fiber
silica
glass layer
soot
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
Application number
JP6162835A
Other languages
Japanese (ja)
Inventor
Yoichi Akasaka
洋一 赤坂
Kunio Ogura
邦男 小倉
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Furukawa Electric Co Ltd
Original Assignee
Furukawa Electric Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Furukawa Electric Co Ltd filed Critical Furukawa Electric Co Ltd
Priority to JP6162835A priority Critical patent/JPH085856A/en
Publication of JPH085856A publication Critical patent/JPH085856A/en
Pending legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C03B2203/22—Radial profile of refractive index, composition or softening point

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

PURPOSE:To provide a quartz optical fiber having improved mechanical strength without impairing transmission loss and a process for producing the fiber. CONSTITUTION:This quartz optical fiber has an internal clad 2 on the outer periphery of a core 1 and an outer clad 3 on the outer periphery of the internal clad 2. The softening temp. of the outer clad 3 is higher than the softening temp. of the core 1 or the inner clad 2. The outer periphery of the outer clad 3 is provided with a glass layer 4 having the softening temp. lower than the softening temp. of the outer clad 3. Since the glass layer 4 having the softening temp. lower than the softening temp. of the outer clad 3 exists on the outer periphery of the outer clad 3, only the surface has nearly a molten state even if the fiber is drawn at a low drawing temp. The surface flaws of the optical fiber generated in a preform stage are drastically decreased.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、通信に使用される石英
系光ファイバとその製造方法に関するもので、さらに詳
しくは伝送損失を損なうことなく機械的強度を向上させ
た石英系光ファイバとその製造方法に関するものであ
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silica-based optical fiber used for communication and a method of manufacturing the same, and more specifically to a silica-based optical fiber having improved mechanical strength without impairing transmission loss and the same. The present invention relates to a manufacturing method.

【０００２】[0002]

【従来の技術】石英コア、Ｆドープクラッドに代表され
る石英系光ファイバは、コアとクラッドの軟化温度が異
なり、通常、図３に示すようにコアの軟化温度が高くク
ラッドの軟化温度が低い構造となっている。このような
石英系光ファイバは、線引時に光ファイバにかかる引張
応力の殆どをコアで受けることになるため、コアに構造
欠陥が生じ易く、これに起因するロス増が発生し、初期
ロスを十分低減できないという問題があった。このよう
な問題を解決する方法として、図４および図５に示すよ
うに光の伝送に影響しない外周部に外部クラッド１３を
設け、該外部クラッド１３をコア１１と同等かそれより
軟化温度の高いガラスとして、コア１１に集中する線引
時の引張応力を外部ガラスに分担させる光ファイバ構造
が提案されている。2. Description of the Related Art In a silica-based optical fiber typified by a quartz core and an F-doped clad, the softening temperatures of the core and the clad are different, and the softening temperature of the core is usually high and the softening temperature of the clad is low as shown in FIG. It has a structure. In such a silica-based optical fiber, most of the tensile stress applied to the optical fiber at the time of drawing is received by the core, so that a structural defect is likely to occur in the core, an increase in loss due to this occurs, and an initial loss is generated. There was a problem that it could not be reduced sufficiently. As a method for solving such a problem, as shown in FIGS. 4 and 5, an outer clad 13 is provided on the outer peripheral portion that does not affect the transmission of light, and the outer clad 13 is equal to or higher in softening temperature than the core 11. As the glass, an optical fiber structure has been proposed in which the tensile stress at the time of drawing concentrated on the core 11 is shared by the external glass.

【０００３】前述した外部クラッドを有する光ファイバ
は、線引時の引張応力によって生ずるコア１１の構造欠
陥を抑制できるため、初期ロスの大幅な低減が可能とな
る。但し、外部クラッド１３まで十分軟らかくなるよう
な高い温度で線引きした場合は、逆にコア１１やコア周
辺の内部クラッド１２が極端に軟らかくなり、今度は熱
的な構造欠陥を生ずることになり、別の異なる現象によ
って初期ロス増が起きる。従って、前記外部クラッドを
有する光ファイバは、線引きの際に可能な限りの低温で
線引きし、引張応力と熱的な構造欠陥を同時に抑制する
ことで、初期ロスの低い光ファイバが得られる。Since the optical fiber having the above-mentioned outer cladding can suppress the structural defect of the core 11 caused by the tensile stress at the time of drawing, the initial loss can be greatly reduced. However, if the outer cladding 13 is drawn at such a high temperature that it is soft enough, the core 11 and the inner cladding 12 around the core become extremely soft, which in turn causes thermal structural defects. The initial loss increase occurs due to the different phenomena of. Therefore, the optical fiber having the outer cladding is drawn at the lowest possible temperature at the time of drawing to suppress tensile stress and thermal structural defects at the same time, whereby an optical fiber with low initial loss can be obtained.

【０００４】[0004]

【発明が解決しようとする課題】しかしながら、前記外
部クラッドを有する光ファイバは、低温線引を実施して
いるため、機械強度の観点からは大きな問題を抱える。
つまり、最外層に軟化温度の高いガラスを配置している
ため、プリフォーム表面が線引時の熱で十分軟化しきら
ず、元々のプリフォームに存在している表面の微小な傷
を低減することができない。また、線引の高い張力応力
が光ファイバ表面にかかるため、表面傷を拡大してしま
う現象も生じる。これらの要因により線引きされた光フ
ァイバは、非常に低強度部が多いものとなっていた。However, since the optical fiber having the outer cladding is subjected to low temperature drawing, it has a serious problem from the viewpoint of mechanical strength.
In other words, because the glass with a high softening temperature is placed in the outermost layer, the preform surface is not sufficiently softened by the heat during drawing, and it is possible to reduce the microscopic scratches on the surface existing in the original preform. I can't. In addition, since a tensile stress with a high degree of drawing is applied to the surface of the optical fiber, a phenomenon that surface scratches are enlarged occurs. The optical fiber drawn by these factors has many very low strength parts.

【０００５】[0005]

【課題を解決するための手段】本発明は上記の問題を解
決し、伝送損失を損なうことなく機械的強度を向上させ
た石英系光ファイバとその製造方法を提供することを目
的とする。上記の目的を達成するために、本発明は以下
のような手段を有している。SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a silica optical fiber having improved mechanical strength without impairing transmission loss and a method for manufacturing the same. In order to achieve the above object, the present invention has the following means.

【０００６】本発明のうち請求項１の石英系光ファイバ
は、コアの外周に内部クラッド、前記内部クラッドの外
周に外部クラッドを備えている石英系光ファイバであっ
て、前記外部クラッドの軟化温度は前記コアもしくは前
記内部クラッドの軟化温度より高く、かつ前記外部クラ
ッドの外周には軟化温度が前記外部クラッドより低いガ
ラス層を有することを特徴とする。The silica-based optical fiber according to claim 1 of the present invention is a silica-based optical fiber having an inner cladding on the outer periphery of the core and an outer cladding on the outer periphery of the inner cladding, wherein the softening temperature of the outer cladding is Has a glass layer whose softening temperature is higher than the softening temperature of the core or the inner cladding and lower than the softening temperature of the outer cladding on the outer periphery of the outer cladding.

【０００７】本発明のうち請求項２の石英系光ファイバ
は、軟化温度の低いガラス層の厚さは０．１μｍ以上１
０μｍ以下の範囲であることを特徴とする。In the silica optical fiber according to claim 2 of the present invention, the glass layer having a low softening temperature has a thickness of 0.1 μm or more.
It is characterized in that it is in the range of 0 μm or less.

【０００８】本発明のうち請求項３の石英系光ファイバ
は、軟化温度の低いガラス層は、Ｆ、Ｐ、Ｂ、Ｃｌのう
ちのいずれか、もしくは２つ以上の元素がドーパントと
して添加された石英ガラスであることを特徴とする。In the silica optical fiber according to claim 3 of the present invention, the glass layer having a low softening temperature is doped with any one of F, P, B and Cl, or two or more elements as a dopant. It is characterized by being quartz glass.

【０００９】本発明のうち請求項４の石英系光ファイバ
の製造方法は、コアの外周に内部クラッド、前記内部ク
ラッドの外周に外部クラッドを備え、前記外部クラッド
の軟化温度は前記コアもしくは前記内部クラッドの軟化
温度より高く、かつ前記外部クラッドの外周には軟化温
度が前記外部クラッドより低いガラス層を有する石英系
光ファイバであって、前記軟化温度の低いガラス層は、
外付け法によりスートを形成し、前記スートに軟化温度
を下げるドーパントを添加して形成されることを特徴と
する。According to a fourth aspect of the present invention, in the method for producing a silica-based optical fiber, an inner cladding is provided on the outer periphery of the core, and an outer cladding is provided on the outer periphery of the inner cladding, and the softening temperature of the outer cladding is the core or the inner cladding. A silica-based optical fiber having a glass layer having a softening temperature higher than that of the clad and having a softening temperature lower than the outer clad on the outer periphery of the outer clad, wherein the glass layer having a low softening temperature is:
It is characterized in that the soot is formed by an external method, and a dopant for lowering the softening temperature is added to the soot.

【００１０】本発明のうち請求項５の石英系光ファイバ
の製造方法は、前記軟化温度の低いガラス層は、外付け
法によるスート合成時に軟化温度を下げるドーパントを
添加して形成されることを特徴とする。According to a fifth aspect of the present invention, in the method for manufacturing a silica-based optical fiber, the glass layer having a low softening temperature is formed by adding a dopant that lowers the softening temperature during soot synthesis by an external method. Characterize.

【００１１】本発明のうち請求項６の石英系光ファイバ
の製造方法は、前記軟化温度の低いガラス層は、外付け
法によって合成されたスートをガラス化する際の雰囲気
に軟化温度を下げるドーパントを添加して形成されるこ
とを特徴とする。According to a sixth aspect of the present invention, in the method for manufacturing a silica-based optical fiber, the glass layer having a low softening temperature is a dopant that lowers the softening temperature to an atmosphere when vitrifying the soot synthesized by the external method. It is characterized by being added.

【００１２】本発明のうち請求項７の石英系光ファイバ
の製造方法は、外部クラッドと軟化温度の低いガラス層
に相当するスートを外付け法により同時に合成し、前記
スートをガラス化する際に前記スートの外側部分に軟化
温度を下げるドーパントを添加して、前記スートの内側
部分を外部クラッド、外側部分を軟化温度の低いガラス
層とすることを特徴とする。According to a seventh aspect of the present invention, in the method for producing a silica-based optical fiber, the outer cladding and the soot corresponding to the glass layer having a low softening temperature are simultaneously synthesized by an external attachment method, and the soot is vitrified. A dopant for lowering the softening temperature is added to an outer portion of the soot to form an inner clad of the soot as an outer cladding and an outer portion of the soot as a glass layer having a low softening temperature.

【００１３】[0013]

【作用】本発明のうち請求項１〜３の石英系光ファイバ
によれば、コアの外周に内部クラッド、前記内部クラッ
ドの外周に外部クラッドを備えている石英系光ファイバ
であって、前記外部クラッドの軟化温度は前記コアもし
くは前記内部クラッドの軟化温度より高く、かつ前記外
部クラッドの外周には軟化温度が前記外部クラッドより
低いガラス層を有しているので、低い線引温度で線引き
しても表面だけは溶融状態に近くなり、プリフォーム段
階で生じている光ファイバの表面傷が大幅に減少する。According to the silica type optical fiber of the present invention, the silica type optical fiber is provided with an inner cladding on the outer periphery of the core and an outer cladding on the outer periphery of the inner cladding. The softening temperature of the cladding is higher than the softening temperature of the core or the inner cladding, and the outer cladding has a glass layer having a lower softening temperature than the outer cladding. However, only the surface becomes close to the molten state, and the surface flaws of the optical fiber generated at the preform stage are greatly reduced.

【００１４】本発明のうち請求項２の石英系光ファイバ
によれば、軟化温度の低いガラス層は厚さが０．１μｍ
以上１０μｍ以下の範囲であるので、光ファイバの低強
度部に生ずる微小傷の深さ（最大０．１μｍ程度）より
深く、光ファイバに生ずる表面傷を埋めるのには充分で
ある。一方、前記厚みは厚過ぎると光ファイバ表面の変
形などの新たな問題も生ずるが、本発明では１０μｍ以
下であるので、問題は生じない。According to the silica type optical fiber of the second aspect of the present invention, the glass layer having a low softening temperature has a thickness of 0.1 μm.
Since it is in the range of 10 μm or less, it is sufficient to fill the surface scratch generated in the optical fiber deeper than the depth of the minute scratch generated in the low strength portion of the optical fiber (about 0.1 μm at maximum). On the other hand, if the thickness is too thick, a new problem such as deformation of the surface of the optical fiber may occur, but since it is 10 μm or less in the present invention, no problem occurs.

【００１５】本発明のうち請求項４〜７の石英系光ファ
イバの製造方法によれば、コアの外周に内部クラッド、
前記内部クラッドの外周に外部クラッドを備え、前記外
部クラッドの軟化温度は前記コアもしくは前記内部クラ
ッドの軟化温度より高く、かつ前記外部クラッドの外周
には軟化温度が前記外部クラッドより低いガラス層を有
する石英系光ファイバであって、前記軟化温度の低いガ
ラス層は、外付け法によりスートを形成し、前記スート
に軟化温度を下げるドーパントを添加して形成されるの
で、低い線引温度で線引きしても表面だけは溶融状態に
近くなり、プリフォーム段階で生じている光ファイバの
表面傷が大幅に減少する。According to the method for manufacturing a silica-based optical fiber of the present invention, the inner cladding is provided on the outer periphery of the core.
An outer clad is provided on the outer circumference of the inner clad, and a softening temperature of the outer clad is higher than that of the core or the inner clad, and a glass layer having a lower softening temperature than the outer clad is provided on the outer circumference of the outer clad. In the quartz optical fiber, the glass layer having a low softening temperature is formed by forming a soot by an external method and adding a dopant that lowers the softening temperature to the soot. However, only the surface becomes close to the molten state, and the surface scratches of the optical fiber generated at the preform stage are greatly reduced.

【００１６】本発明のうち請求項７の石英系光ファイバ
の製造方法によれば、外部クラッドと軟化温度の低いガ
ラス層に相当するスートを外付け法により同時に合成
し、前記スートをガラス化する際に前記スートの外側部
分に軟化温度を下げるドーパントを添加して、前記スー
トの内側部分を外部クラッド、外側部分を軟化温度の低
いガラス層とするので、外部クラッドと軟化温度の低い
ガラス層を外付け法により別々にスートを形成するより
も、製造工程が省略でき生産効率が良い。According to the method for producing a silica-based optical fiber of claim 7 of the present invention, the outer cladding and the soot corresponding to the glass layer having a low softening temperature are simultaneously synthesized by the external attachment method to vitrify the soot. At this time, a dopant that lowers the softening temperature is added to the outer portion of the soot, the inner portion of the soot is the outer cladding, and the outer portion is a glass layer having a lower softening temperature. The manufacturing process can be omitted and the production efficiency is better than the case where the soot is formed separately by the external method.

【００１７】[0017]

【実施例】以下に本発明を実施例により詳細に説明す
る。図１は本発明の石英系光ファイバの一実施例であ
る。コア１は僅かにＦをドープしたＳｉＯ2 、内部クラ
ッド２はで比屈折率差でΔ＝−０．３５％となるように
ＳｉＯ2 にＦを均一に添加したもの、外部クラッド３は
純ＳｉＯ2 である。尚、最外層の符号４は、軟化温度の
低いガラス層であり、ＳｉＯ2 に軟化温度を下げるドー
パントを添加したものである。また、表１と表２は、本
発明の石英系光ファイバと従来の石英系光ファイバの実
験結果を示したものである。The present invention will be described below in detail with reference to examples. FIG. 1 shows an embodiment of the silica type optical fiber of the present invention. The core 1 is SiO 2 slightly doped with F, the inner cladding 2 is SiO 2 uniformly added with F so that the relative refractive index difference is Δ = −0.35%, and the outer cladding 3 is pure SiO 2. Is 2 . Reference numeral 4 of the outermost layer is a glass layer having a low softening temperature, which is SiO 2 to which a dopant for lowering the softening temperature is added. Tables 1 and 2 show experimental results of the silica optical fiber of the present invention and the conventional silica optical fiber.

【００１８】実施例１、２、３、４、５、６では、軟化
温度を下げるドーパントとしてΔ＝−０．３７％相当の
ＦをドープしたＳｉＯ2 である軟化温度の低いガラス層
４の厚さを変えて外付け法で合成した。尚、Ｆは外付け
法で合成したスートのガラス化時に添加したものであ
る。実施例１〜６では、軟化温度の低いガラス層４の厚
さを変化させているが、厚さ０．１〜１０μｍの場合に
高強度と低損失を同時に実現している。前記軟化温度の
低いガラス層４の厚さが１０μｍ越えて１５μｍ程度に
なると、光ファイバの外径が決まっているために引張応
力を分担する外部クラッド３を薄くせざるを得ない。そ
の結果、コア１にも引張応力のー部が負荷されることに
なり、張力に起因する伝送損失が多少生じてしまう。ま
た、軟化温度の低いガラス層４の厚さがさらに厚くなる
と、線引時のセッティングの僅かなずれによる歪で、僅
かではあるが光ファイバの非円度が低下する。従って、
本発明は軟化温度の低いガラス層４の厚さが０．１〜１
０μｍの範囲で特に有効である。In Examples 1, 2, 3, 4, 5, and 6, the thickness of the glass layer 4 having a low softening temperature, which is SiO 2 doped with F corresponding to Δ = −0.37% as a dopant for lowering the softening temperature. The composition was changed according to the external method. In addition, F is added at the time of vitrification of the soot synthesized by the external method. In Examples 1 to 6, the thickness of the glass layer 4 having a low softening temperature is changed, but when the thickness is 0.1 to 10 μm, high strength and low loss are realized at the same time. When the thickness of the glass layer 4 having a low softening temperature exceeds 10 μm to about 15 μm, the outer diameter of the optical fiber is fixed, so that the outer cladding 3 that bears the tensile stress must be thinned. As a result, the core 1 of the tensile stress is also applied to the core 1, and some transmission loss due to the tension occurs. Further, when the glass layer 4 having a low softening temperature is further thickened, the non-circularity of the optical fiber is slightly reduced due to the distortion caused by the slight deviation of the setting during drawing. Therefore,
In the present invention, the glass layer 4 having a low softening temperature has a thickness of 0.1 to 1
It is particularly effective in the range of 0 μm.

【００１９】次に、実施例７、８、９は、実施例１〜６
で用いた軟化温度を低下させるドープ剤Ｆの代わりに、
Ｃｌ、Ｐ、Ｂを用いたものである。このうち、Ｃｌはガ
ラス化工程で添加し、ＰとＢはガラス化工程での添加の
効率が悪いため、外付けスート合成時にドーパントを添
加した。いずれの場合でも、低伝送損失と高強度を同時
に実現している。更に、実施例１０、１１は、外部クラ
ッド３と軟化温度の低いガラス層４に相当するスートを
外付け法で同時に合成しておき、ガラス化時にＦまたは
Ｃｌを軟化温度の低いガラス層４に相当するスート部分
だけに添加した例である。外付け法によって合成したス
ートをドーパント原料を含むガラス化雰囲気で処理した
場合、密度の高いスートの場合は内部へ拡散して行くの
に時間がかかり、（スートの密度が高いほど添加され難
いことはよく知られている）また、外周部でドーパント
がトラップされる現象が生じることにより、短時間に焼
結させると外側部分にだけドーパントが添加された分布
とすることができる。Next, Examples 7, 8 and 9 are Examples 1 to 6.
In place of the doping agent F used for reducing the softening temperature,
It uses Cl, P, and B. Of these, Cl was added in the vitrification step, and P and B were added in the vitrification step inefficiently, so a dopant was added during the synthesis of the external soot. In both cases, low transmission loss and high strength are realized at the same time. Furthermore, in Examples 10 and 11, the outer cladding 3 and the soot corresponding to the glass layer 4 having a low softening temperature were simultaneously synthesized by the external attachment method, and F or Cl was added to the glass layer 4 having a low softening temperature during vitrification. In this example, only the corresponding soot portion is added. When the soot synthesized by the external method is treated in a vitrifying atmosphere containing a dopant material, it takes time for the soot with a high density to diffuse into the interior (the higher the density of the soot, the more difficult it is to add). It is well known) that the phenomenon in which the dopant is trapped occurs at the outer peripheral portion, so that it is possible to obtain a distribution in which the dopant is added only to the outer portion when the sintering is performed for a short time.

【００２０】実施例１０、１１では、石英の外部クラッ
ド３と軟化温度の低いガラス層４に相当するスートの密
度を０．５〜０．８ｇ／ｃｍ3 とし、ＳｉＦ4 およびＣ
ｌ2を添加したＨｅ雰囲気中（温度１６５０℃）に、３
００ｍ／ｍｉｎの高速で挿入した。その結果、外付け法
によって合成された層の内側にはＦやＣｌが殆ど拡散せ
ず、外付け法によって合成された層の外側には軟化温度
を下げるドーパントを固定できた。但し、境界部でのド
ーパント分布は、ステップ的な変化ではなく、なだらか
に傾斜して変化したものとなっている。この方法で製造
した母材からも、低伝送損失と高強度を両立させた石英
系光ファイバを得ることができる。In Examples 10 and 11, the density of soot corresponding to the quartz outer cladding 3 and the glass layer 4 having a low softening temperature was set to 0.5 to 0.8 g / cm 3, and SiF 4 and C were used.
In a He atmosphere containing 1 2 (temperature 1650 ° C.), 3
It was inserted at a high speed of 00 m / min. As a result, F and Cl were hardly diffused inside the layer synthesized by the external method, and the dopant for lowering the softening temperature could be fixed on the outside of the layer synthesized by the external method. However, the dopant distribution at the boundary is not a stepwise change, but changes with a gentle slope. A silica optical fiber having both low transmission loss and high strength can be obtained from the base material manufactured by this method.

【００２１】実施例１０、１１では、外部クラッド３と
軟化温度の低いガラス層４を別々に合成する製造方法に
対して、製造工程をひとつ省略したものとなる。In Examples 10 and 11, one manufacturing step was omitted from the manufacturing method in which the outer cladding 3 and the glass layer 4 having a low softening temperature were separately synthesized.

【００２２】比較例１、２は最外層のガラス層を設けな
い図４に示す従来構造の石英系光ファイバである。比較
例１は他に較べて高温で線引きしているため、光ファイ
バ強度は良好であるが熱による構造欠陥がコア１１周辺
に生じ、構造不完全性による伝送損失増が生じている。Comparative Examples 1 and 2 are silica type optical fibers having the conventional structure shown in FIG. 4 in which the outermost glass layer is not provided. Since Comparative Example 1 draws at a higher temperature than the others, the optical fiber strength is good, but structural defects due to heat occur around the core 11 and transmission loss increases due to structural imperfections.

【００２３】比較例２は、ガラス表面が軟化しないよう
な低温で線引きしたもので、外部クラッド１３で線引張
力を分担しており、熱と応力の両方が起因する構造欠陥
が抑制できるため、結果として伝送損失が非常に小さく
なっている。しかし、表面欠陥が線引後も多く残ってし
まうため、最低強度が１．５ＧＰａとなり、低強度部が
存在すると同時に、強度の５０％値も低くなっている。Comparative Example 2 is drawn at a low temperature such that the glass surface is not softened, and the outer cladding 13 shares the linear tension force, so that structural defects caused by both heat and stress can be suppressed. As a result, the transmission loss is very small. However, since many surface defects remain after drawing, the minimum strength is 1.5 GPa, and there is a low strength portion, and at the same time, the 50% value of the strength is low.

【００２４】[0024]

【表１】 [Table 1]

【００２５】[0025]

【表２】 [Table 2]

【００２６】[0026]

【発明の効果】以上述べたように、本発明の請求項１〜
３の石英系光ファイバによれば、コアの外周に内部クラ
ッド、前記内部クラッドの外周に外部クラッドを備えて
いる石英系光ファイバであって、前記外部クラッドの軟
化温度は前記コアもしくは前記内部クラッドの軟化温度
より高く、かつ前記外部クラッドの外周には軟化温度が
前記外部クラッドより低いガラス層を有しているので、
低い線引温度で線引きしても表面だけは溶融状態に近く
なり、プリフォーム段階で生じている光ファイバの表面
傷が大幅に減少する。従って、コア及びコア周辺クラッ
ドに線引時の引張応力をかけないようにすることで低ロ
スを実現するとともに、ファイバ強度も従来と同等のも
のが得られる。As described above, the claims 1 to 3 of the present invention are as follows.
3 is a silica-based optical fiber having an inner cladding on the outer periphery of the core and an outer cladding on the outer periphery of the inner cladding, wherein the softening temperature of the outer cladding is the core or the inner cladding. Higher than the softening temperature of, and since the outer cladding has a glass layer having a lower softening temperature than the outer cladding,
Even if the wire is drawn at a low drawing temperature, only the surface is close to a molten state, and the surface scratches of the optical fiber generated at the preform stage are greatly reduced. Therefore, by not applying tensile stress during drawing to the core and the clad around the core, low loss can be realized, and fiber strength equivalent to that of the conventional one can be obtained.

【００２７】本発明のうち請求項２の石英系光ファイバ
によれば、軟化温度の低いガラス層は厚さが０．１μｍ
以上１０μｍ以下の範囲であるので、光ファイバの低強
度部に生ずる微小傷の深さ（最大０．１μｍ程度）より
深く、光ファイバに生ずる表面傷を埋めるのには充分で
ある。一方、前記厚みは厚過ぎると光ファイバ表面の変
形などの新たな問題も生ずるが、本発明では１０μｍ以
下であるので、問題は生じない。According to the optical fiber of claim 2 of the present invention, the glass layer having a low softening temperature has a thickness of 0.1 μm.
Since it is in the range of 10 μm or less, it is sufficient to fill the surface scratch generated in the optical fiber deeper than the depth of the minute scratch generated in the low strength portion of the optical fiber (about 0.1 μm at maximum). On the other hand, if the thickness is too thick, a new problem such as deformation of the surface of the optical fiber may occur, but since it is 10 μm or less in the present invention, no problem occurs.

【００２８】本発明のうち請求項４〜７の石英系光ファ
イバの製造方法によれば、コアの外周に内部クラッド、
前記内部クラッドの外周に外部クラッドを備え、前記外
部クラッドの軟化温度は前記コアもしくは前記内部クラ
ッドの軟化温度より高く、かつ前記外部クラッドの外周
には軟化温度が前記外部クラッドより低いガラス層を有
する石英系光ファイバであって、前記軟化温度の低いガ
ラス層は、外付け法によりスートを形成し、前記スート
に軟化温度を下げるドーパントを添加して形成されるの
で、低い線引温度で線引きしても表面だけは溶融状態に
近くなり、プリフォーム段階で生じている光ファイバの
表面傷が大幅に減少する。According to the method for producing a silica-based optical fiber of the present invention, the inner cladding is provided on the outer periphery of the core.
An outer clad is provided on the outer circumference of the inner clad, and a softening temperature of the outer clad is higher than that of the core or the inner clad, and a glass layer having a lower softening temperature than the outer clad is provided on the outer circumference of the outer clad. In the quartz optical fiber, the glass layer having a low softening temperature is formed by forming a soot by an external method and adding a dopant that lowers the softening temperature to the soot. However, only the surface becomes close to the molten state, and the surface scratches of the optical fiber generated at the preform stage are greatly reduced.

【００２９】本発明のうち請求項７の石英系光ファイバ
の製造方法によれば、外部クラッドと軟化温度の低いガ
ラス層に相当するスートを外付け法により同時に合成
し、前記スートをガラス化する際に前記スートの外側部
分に軟化温度を下げるドーパントを添加して、前記スー
トの内側部分を外部クラッド、外側部分を軟化温度の低
いガラス層とするので、外部クラッドと軟化温度の低い
ガラス層を外付け法により別々にスートを形成するより
も、製造工程が省略でき生産効率が良い。According to the method for producing a silica-based optical fiber of claim 7 of the present invention, the outer cladding and the soot corresponding to the glass layer having a low softening temperature are simultaneously synthesized by the external attachment method to vitrify the soot. At this time, a dopant that lowers the softening temperature is added to the outer portion of the soot, the inner portion of the soot is the outer cladding, and the outer portion is a glass layer having a lower softening temperature. The manufacturing process can be omitted and the production efficiency is better than the case where the soot is formed separately by the external method.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の石英系光ファイバの一実施例を示す断
面図である。FIG. 1 is a sectional view showing an embodiment of a silica-based optical fiber of the present invention.

【図２】図１の石英系光ファイバの径方向とその軟化温
度の関係図である。2 is a diagram showing the relationship between the radial direction of the silica-based optical fiber of FIG. 1 and its softening temperature.

【図３】従来の石英系光ファイバの径方向とその軟化温
度の関係図である。FIG. 3 is a diagram showing the relationship between the radial direction of a conventional silica optical fiber and its softening temperature.

【図４】従来の石英系光ファイバの一例を示す断面図で
ある。FIG. 4 is a sectional view showing an example of a conventional silica optical fiber.

【図５】図４の石英系光ファイバの径方向とその軟化温
度の関係図である。5 is a diagram showing the relationship between the radial direction of the silica-based optical fiber of FIG. 4 and its softening temperature.

【符号の説明】[Explanation of symbols]

１ コア ２ 内部クラッド ３ 外部クラッド ４ 軟化温度の低いガラス層 1 core 2 inner clad 3 outer clad 4 glass layer with low softening temperature

Claims (7)

【特許請求の範囲】[Claims] 【請求項１】 コアの外周に内部クラッド、前記内部ク
ラッドの外周に外部クラッドを備えている石英系光ファ
イバであって、前記外部クラッドの軟化温度は前記コア
もしくは前記内部クラッドの軟化温度より高く、かつ前
記外部クラッドの外周には軟化温度が前記外部クラッド
より低いガラス層を有することを特徴とする石英系光フ
ァイバ。1. A silica optical fiber having an inner cladding on the outer periphery of a core and an outer cladding on the outer periphery of the inner cladding, wherein the softening temperature of the outer cladding is higher than the softening temperature of the core or the inner cladding. A silica-based optical fiber having a glass layer having a softening temperature lower than that of the outer cladding on the outer periphery of the outer cladding. 【請求項２】 軟化温度の低いガラス層の厚さは０．１
μｍ以上１０μｍ以下の範囲であることを特徴とする請
求項１記載の石英系光ファイバ。2. The glass layer having a low softening temperature has a thickness of 0.1.
The silica-based optical fiber according to claim 1, wherein the silica-based optical fiber is in a range of μm or more and 10 μm or less. 【請求項３】 軟化温度の低いガラス層は、Ｆ、Ｐ、
Ｂ、Ｃｌのうちのいずれかもしくは２つ以上の元素がド
ーパントとして添加された石英ガラスであることを特徴
とする請求項１または請求項２記載の石英系光ファイ
バ。3. The glass layer having a low softening temperature comprises F, P,
The silica-based optical fiber according to claim 1 or 2, which is silica glass to which any one or more elements of B and Cl are added as a dopant. 【請求項４】 コアの外周に内部クラッド、前記内部ク
ラッドの外周に外部クラッドを備え、前記外部クラッド
の軟化温度は前記コアもしくは前記内部クラッドの軟化
温度より高く、かつ前記外部クラッドの外周には軟化温
度が前記外部クラッドより低いガラス層を有する石英系
光ファイバであって、前記軟化温度の低いガラス層は、
外付け法によりスートを形成し、前記スートに軟化温度
を下げるドーパントを添加して形成されることを特徴と
する石英系光ファイバの製造方法。4. An inner cladding is provided on the outer periphery of the core, and an outer cladding is provided on the outer periphery of the inner cladding, wherein the softening temperature of the outer cladding is higher than the softening temperature of the core or the inner cladding, and the outer periphery of the outer cladding is A silica-based optical fiber having a glass layer having a softening temperature lower than that of the outer cladding, wherein the glass layer having a low softening temperature is:
A method for manufacturing a silica-based optical fiber, which is characterized in that a soot is formed by an external attachment method, and a soot is added with a dopant that lowers a softening temperature. 【請求項５】 前記軟化温度の低いガラス層は、外付け
法によるスート合成時に軟化温度を下げるドーパントを
添加して形成されることを特徴とする請求項４記載の石
英系光ファイバの製造方法。5. The method for producing a silica-based optical fiber according to claim 4, wherein the glass layer having a low softening temperature is formed by adding a dopant that lowers the softening temperature during soot synthesis by an external attachment method. . 【請求項６】 前記軟化温度の低いガラス層は、外付け
法によって合成されたスートをガラス化する際の雰囲気
に軟化温度を下げるドーパントを添加して形成されるこ
とを特徴とする請求項４記載の石英系光ファイバの製造
方法。6. The glass layer having a low softening temperature is formed by adding a dopant for lowering the softening temperature to an atmosphere for vitrifying soot synthesized by an external method. A method for manufacturing the silica-based optical fiber described above. 【請求項７】 外部クラッドと軟化温度の低いガラス層
に相当するスートを外付け法により同時に合成し、前記
スートをガラス化する際に前記スートの外側部分に軟化
温度を下げるドーパントを添加して、前記スートの内側
部分を外部クラッド、外側部分を軟化温度の低いガラス
層とすることを特徴とする請求項４記載の石英系光ファ
イバの製造方法。7. An outer cladding and a soot corresponding to a glass layer having a low softening temperature are simultaneously synthesized by an external attachment method, and when vitrifying the soot, a dopant for lowering the softening temperature is added to an outer portion of the soot. 5. The method for producing a silica-based optical fiber according to claim 4, wherein the inner part of the soot is an outer cladding and the outer part is a glass layer having a low softening temperature.
JP6162835A 1994-06-21 1994-06-21 Quartz optical fiber and its production Pending JPH085856A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP6162835A JPH085856A (en) 1994-06-21 1994-06-21 Quartz optical fiber and its production

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP6162835A JPH085856A (en) 1994-06-21 1994-06-21 Quartz optical fiber and its production

Publications (1)

Publication Number Publication Date
JPH085856A true JPH085856A (en) 1996-01-12

Family

ID=15762155

Family Applications (1)

Application Number Title Priority Date Filing Date
JP6162835A Pending JPH085856A (en) 1994-06-21 1994-06-21 Quartz optical fiber and its production

Country Status (1)

Country Link
JP (1) JPH085856A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002148465A (en) * 2000-08-28 2002-05-22 Sumitomo Electric Ind Ltd Optical fiber, method for manufacturing optical fiber preform and method for manufacturing optical fiber

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002148465A (en) * 2000-08-28 2002-05-22 Sumitomo Electric Ind Ltd Optical fiber, method for manufacturing optical fiber preform and method for manufacturing optical fiber

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