JP2010163329A - Method for manufacturing preform for optical fiber added with rare earth element - Google Patents

Method for manufacturing preform for optical fiber added with rare earth element Download PDF

Info

Publication number
JP2010163329A
JP2010163329A JP2009007742A JP2009007742A JP2010163329A JP 2010163329 A JP2010163329 A JP 2010163329A JP 2009007742 A JP2009007742 A JP 2009007742A JP 2009007742 A JP2009007742 A JP 2009007742A JP 2010163329 A JP2010163329 A JP 2010163329A
Authority
JP
Japan
Prior art keywords
rare earth
quartz tube
earth element
optical fiber
manufacturing
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.)
Granted
Application number
JP2009007742A
Other languages
Japanese (ja)
Other versions
JP5384123B2 (en
Inventor
Seichin Kin
成珍 金
Tetsuya Yamamoto
哲也 山本
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.)
Mitsubishi Cable Industries Ltd
Original Assignee
Mitsubishi Cable Industries 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 Mitsubishi Cable Industries Ltd filed Critical Mitsubishi Cable Industries Ltd
Priority to JP2009007742A priority Critical patent/JP5384123B2/en
Publication of JP2010163329A publication Critical patent/JP2010163329A/en
Application granted granted Critical
Publication of JP5384123B2 publication Critical patent/JP5384123B2/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

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
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
    • C03B37/01838—Reactant delivery systems, e.g. reactant deposition burners for delivering and depositing additional reactants as liquids or solutions, e.g. for solution doping of the deposited glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
    • C03B2201/34—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with rare earth metals, i.e. with Sc, Y or lanthanides, e.g. for laser-amplifiers

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General 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)
  • Glass Melting And Manufacturing (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing in high productivity an optical fiber having a uniform core NA that enables a solution of a compound containing rare earth elements to be efficiently used. <P>SOLUTION: The method for manufacturing a preform for the optical fiber includes a liquid impregnation step where glass microparticles deposited on the inner peripheral surface of a quartz tube by the MCVD method are impregnated with the solution of a compound containing rare earth elements to add the rare earth elements to the glass microparticles. After a step of clarifying the glass microparticles added with the rare earth elements, the method for manufacturing a preform for the optical fiber includes another step of depositing the glass microparticles and another step of clarifying the glass microparticles. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

本発明は光ファイバ母材の製造方法に関し、特に、希土類元素添加の光ファイバ母材の製造方法に関する。   The present invention relates to a method for manufacturing an optical fiber preform, and more particularly to a method for manufacturing a rare earth element-added optical fiber preform.

ＭＣＶＤ（modified chemical vapor deposition）法を用いてコア母材を作製する製法として、ガラス微粒子の形成と、希土類元素含有化合物等を添加する工程を別個の工程として行う、液浸ＭＣＶＤと呼ばれる製造方法がある。該製造方法は、石英管の内周面にガラス微粒子を堆積した後、石英管の一方の端部から希土類元素含有化合物等を含む溶液を流し込んで微粒子中に浸透後、希土類元素含有化合物等を熱で拡散させた後にガラス微粒子を透明化させるという方法である。例えば、石英管内周面にガラス微粒子を堆積させてガラス微粒子層を形成する堆積工程、該ガラス微粒子層に希土類元素含有化合物の溶液を含浸させる液浸工程、乾燥工程を経て、ガラス微粒子層の透明化工程、及び石英管をコラプスする工程により光ファイバ母材を製造する方法が特許文献１に記載されている。上記の製造方法では、ガラス微粒子層の透明化に引き続いて石英管を中実化させるコラプス工程を行うことによって光ファイバ母材を作り出している。   As a manufacturing method for producing a core base material using a modified chemical vapor deposition (MCVD) method, there is a manufacturing method called immersion MCVD in which the formation of glass fine particles and the step of adding a rare earth element-containing compound are performed as separate steps. is there. In the manufacturing method, after depositing glass fine particles on the inner peripheral surface of a quartz tube, a solution containing a rare earth element-containing compound is poured from one end of the quartz tube to penetrate into the fine particles, and then the rare earth element-containing compound, etc. In this method, the glass fine particles are made transparent after being diffused by heat. For example, a glass particulate layer is formed by depositing glass particulates on the inner peripheral surface of a quartz tube, a liquid immersion step in which the glass particulate layer is impregnated with a solution of a rare earth element-containing compound, and a drying step. Patent Document 1 describes a method of manufacturing an optical fiber preform by a forming step and a step of collapsing a quartz tube. In the manufacturing method described above, the optical fiber preform is produced by performing a collapse process for solidifying the quartz tube subsequent to the transparency of the glass fine particle layer.

特開２００４−８３３９９号公報JP 2004-83399 A

しかしながら、微粒子ガラスの形成やコラプスする際、原料に含まれているＯＨ基がコア内部に混入されるためにＣｌ２、ＢＣｌ３などのガスを流し、脱水を行わなければいけない。それはコア内にＯＨ基が含まれることにより、ポンプ光かつ信号光の伝送損失が増え、ファイバ特性が悪くなるからである。しかし、脱水のためにＣｌ２、ＢＣｌ３などのガスを流すことによって、高温でこれらのガスとガラスとの反応が促進されるためにコアが選択的にエッチング（蒸発）されてしまうことがある。また、ガラスよりＹｂ、Ａｌ、Ｅｒ、Ｇｅなどの添加元素のエッチング速度が速くなるためにコア中心部の屈折率が低くなり、屈折率プロファイルの中心に凹みが生じる。一方、主な光は基本モード(ＬＰ０１)としてコア中心部を導波するため、屈折率プロファイル中心の凹みによって光散乱を受け、伝送損失の増大、及びモードフィールドが歪むという現象が生じる。また、Ｃｌ２、ＢＣｌ３などのガスによって添加元素のエッチング速度が異なり、局所的にガラス組成の揺らぎや結晶欠陥が生じてしまう。特に、Ｙｂ添加ファイバレーザの場合は自励パルス、レイリー散乱（ＲＳ)、誘導ブリルアン散乱（ＳＢＳ）、誘導ラマン散乱（ＳＲＳ)などの非線形特性が顕著となり、ファイバ端面が破壊されるという重大な問題が生じる。この問題を解決するためには、新たなコラプス工程が必要である。ＯＨ基の濃度を減らすために脱水は欠かせない重要な工程であるため、脱水処理を実施しつつ、上記問題を解決できるように光ファイバ母材の製造方法を改善することが求められていた。 However, when forming or collapsing the fine particle glass, dehydration must be performed by flowing a gas such as Cl 2 or BCl 3 because OH groups contained in the raw material are mixed inside the core. This is because the transmission loss of pump light and signal light increases due to the inclusion of OH groups in the core, and the fiber characteristics deteriorate. However, when a gas such as Cl 2 or BCl 3 is flowed for dehydration, the reaction between these gases and glass is promoted at a high temperature, so that the core may be selectively etched (evaporated). . Further, since the etching rate of additive elements such as Yb, Al, Er, and Ge is faster than that of glass, the refractive index at the core central portion is lowered, and a dent is generated at the center of the refractive index profile. On the other hand, since the main light is guided through the core center as the fundamental mode (LP01), light scatters due to the depression at the center of the refractive index profile, resulting in an increase in transmission loss and distortion of the mode field. Further, the etching rate of the additive element differs depending on the gas such as Cl 2 or BCl 3 , and the glass composition fluctuates and crystal defects are locally generated. In particular, in the case of a Yb-doped fiber laser, the nonlinear problem such as self-excited pulse, Rayleigh scattering (RS), stimulated Brillouin scattering (SBS), and stimulated Raman scattering (SRS) becomes prominent, and the serious problem that the end face of the fiber is destroyed. Occurs. In order to solve this problem, a new collapsing process is required. Since dehydration is an indispensable process in order to reduce the concentration of OH groups, it has been required to improve the optical fiber preform manufacturing method so that the above problems can be solved while performing dehydration. .

本発明は、かかる事情に鑑みてなされたものであり、その解決しようとする課題は、屈折率プロファイルの中心に凹みが生じない、光ファイバ母材の製造方法を提供することにある。   The present invention has been made in view of such circumstances, and a problem to be solved is to provide a method for manufacturing an optical fiber preform in which no dent is generated in the center of a refractive index profile.

すなわち、本発明は以下の通りである。
［１］ＭＣＶＤ法により石英管の内周面に形成されたガラス微粒子に、希土類元素含有化合物の溶液を含浸させることにより、希土類元素を添加する液浸工程を有する光ファイバ母材の製造方法であって、希土類元素が添加された前記ガラス微粒子の第１透明化工程後に、さらに、ガラス微粒子を堆積する工程と、ガラス微粒子の第２透明化工程を有することを特徴とする希土類元素添加光ファイバ母材の製造方法。
［２］前記第１透明化工程に続く第１コラプス工程と、前記第２透明化工程に続く第２コラプス工程とをさらに有する、上記［１］に記載の製造方法。
［３］前記液浸工程が、前記石英管に注入された前記溶液を、前記石英管の両端に装着され、弾性材料を用いて形成された栓で封入し、前記栓が装着された石英管を中心軸の周りに回転させる工程である、ことを特徴とする上記［１］または［２］記載の製造方法。
［４］前記希土類元素含有化合物が、希土類元素含有化合物と共添加化合物を含み、前記光ファイバ母材の開口数が０．０５〜０．２である上記［１］〜［３］のいずれかに記載の製造方法。
［５］前記希土類元素がイッテルビウム（Ｙｂ）であり、共添加元素がアルミニウム(Ａｌ)であることを特徴とする上記［４］に記載の製造方法。 That is, the present invention is as follows.
[1] A method of manufacturing an optical fiber preform having a liquid immersion step of adding a rare earth element by impregnating glass fine particles formed on the inner peripheral surface of a quartz tube by an MCVD method with a solution of a rare earth element-containing compound. A rare earth element-doped optical fiber, further comprising a step of depositing glass fine particles and a second transparency step of glass fine particles after the first transparency step of the glass fine particles to which the rare earth element is added. A manufacturing method of a base material.
[2] The manufacturing method according to [1], further including a first collapse step following the first transparency step and a second collapse step following the second transparency step.
[3] In the immersion step, the solution injected into the quartz tube is sealed at both ends of the quartz tube with a plug formed using an elastic material, and the quartz tube with the plug mounted The method according to [1] or [2] above, wherein the method is a step of rotating around a central axis.
[4] Any one of the above [1] to [3], wherein the rare earth element-containing compound includes a rare earth element-containing compound and a co-added compound, and the numerical aperture of the optical fiber preform is 0.05 to 0.2. The manufacturing method as described in.
[5] The method according to [4], wherein the rare earth element is ytterbium (Yb) and the co-added element is aluminum (Al).

本発明により、従来の製造装置を活用しつつ、製造プロセスの大幅な変更をすることなく、簡便な方法で、屈折率プロファイルの中心に凹みや結晶欠陥が少ない光ファイバ母材を製造することができる。   According to the present invention, it is possible to manufacture an optical fiber preform with few dents and crystal defects at the center of the refractive index profile by a simple method without making a significant change in the manufacturing process while utilizing a conventional manufacturing apparatus. it can.

図１は本発明に係る一実施形態の光ファイバ母材の製造方法を示すフローチャートである。FIG. 1 is a flowchart showing a method for manufacturing an optical fiber preform according to an embodiment of the present invention. 図２は本発明の実施例の液浸工程を説明する断面図である。FIG. 2 is a cross-sectional view for explaining the liquid immersion process of the embodiment of the present invention. 図３は本発明の実施例の液浸工程を説明する断面図である。FIG. 3 is a cross-sectional view for explaining the liquid immersion process of the embodiment of the present invention. 図４は本発明の実施例の方法で作製した光ファイバ母材の評価結果を示すチャートである。FIG. 4 is a chart showing the evaluation results of the optical fiber preform manufactured by the method of the example of the present invention. 図５は比較例の光ファイバ母材の製造方法を示すフローチャートである。FIG. 5 is a flowchart showing a method for manufacturing an optical fiber preform of a comparative example. 図６は比較例の方法で作製した光ファイバ母材の評価結果を示すチャートである。FIG. 6 is a chart showing the evaluation results of the optical fiber preform manufactured by the method of the comparative example.

以下、本発明をより詳細に説明する。
本発明は、希土類元素等がドープされたコアを有する光ファイバ母材の製造方法に関するものである。図１に本発明の製造方法をフローチャートで示す。図１に示すように、本発明の製造方法は、第１堆積工程Ｓ１、液浸工程Ｓ２、乾燥拡散工程Ｓ３、第１透明化工程Ｓ４、第１コラプス工程Ｓ５、第２堆積工程Ｓ６、第２透明化工程Ｓ７、および第２コラプス工程Ｓ８からなる。なお、堆積工程の前に、石英管の脱水工程Ｓ０を行っても良い。 Hereinafter, the present invention will be described in more detail.
The present invention relates to a method for manufacturing an optical fiber preform having a core doped with a rare earth element or the like. FIG. 1 is a flowchart showing the manufacturing method of the present invention. As shown in FIG. 1, the manufacturing method of the present invention includes a first deposition step S1, a liquid immersion step S2, a drying diffusion step S3, a first transparency step S4, a first collapse step S5, a second deposition step S6, 2 transparency process S7 and 2nd collapse process S8. Note that a quartz tube dehydration step S0 may be performed before the deposition step.

［脱水工程（Ｓ０）］
ＭＣＶＤ法では有機金属原料中に含まれるＯＨ基やコア作製中に混入されるＯＨ基によって伝送損失が増え、レーザ特性を悪化させるためにＯＨ基の混入を抑制することが望ましい。そのため、脱水工程（Ｓ０）では、無水石英管を高温に加熱しつつ、その一端から脱水ガスを導入することで、石英管の内周面を脱水する。使用する脱水ガスとしては、Ｃｌ２、ＳｉＣｌ４、ＧｅＣｌ４、ＰＯＣｌ３、ＢＣｌ３などを用いることができる。その際、脱水ガスを単独で供給しても構わないが、Ｏ２、Ａｒ、Ｈｅなどのガスと同時に流しても良い。また、脱水温度は石英管内周面の損傷を考慮し、１２００℃から１５００℃が望ましい。なお、無水石英管とは、ＯＨを含む量が１ｐｐｍ以下（赤外線分光器による測定の限界）の石英管を意味する。 [Dehydration step (S0)]
In the MCVD method, it is desirable to suppress the mixing of OH groups in order to increase the transmission loss due to the OH groups contained in the organometallic raw material and the OH groups mixed during core fabrication, and to deteriorate the laser characteristics. Therefore, in the dehydration step (S0), the inner peripheral surface of the quartz tube is dehydrated by introducing a dehydrating gas from one end of the anhydrous quartz tube while heating the anhydrous quartz tube to a high temperature. As the dehydrating gas to be used, Cl 2 , SiCl 4 , GeCl 4 , POCl 3 , BCl 3 or the like can be used. At that time, the dehydrating gas may be supplied alone, but it may flow simultaneously with a gas such as O 2 , Ar, or He. The dehydration temperature is preferably 1200 ° C. to 1500 ° C. in consideration of damage on the inner peripheral surface of the quartz tube. The anhydrous quartz tube means a quartz tube having an OH content of 1 ppm or less (limit of measurement by an infrared spectrometer).

［第１堆積工程（Ｓ１）］
次に、第１堆積工程Ｓ１では、中空の石英管の内周面にガラス微粒子(以下、スートということがある)層を形成する。第１堆積工程では、石英管を加熱しつつ、その一端から、ガラス原料ガス、キャリヤガス、反応ガスなどを導入する。これにより、石英管内周面にガラス微粒子を堆積させることで、スート層を形成する。石英管を加熱する温度は１０００℃から１６００℃が好ましい。堆積時の加熱温度が１６００℃を超えると、微粒子ガラスの大きさや密度が変動し、希土類元素含有化合物をガラス微粒子中に浸透させる液浸工程Ｓ２（後述）にて、微粒子ガラス中に染み込む添加元素や希土類元素のドーピング濃度に好ましく無い影響を与える。一方、１０００℃未満の低温で微粒子ガラスを堆積すると石英管からスート層が剥がれ落ちる場合がある。また、微粒子を堆積する際には石英管の内圧が、大気圧より約４Ｐａ低くなるようにガラス内圧を制御することが好ましい。
ＭＣＶＤで用いるガラス原料ガスとしては、ＳｉＣｌ４、ＳｉＦ４、ＰＯＣｌ３、ＢＦ３、ＢＣｌ３などが挙げられる。また、キャリヤガスとしては、Ｈｅ、Ａｒが挙げられ、反応ガスとしてはＯ２が挙げられる。
なお、一般に、形成するスート層の層厚は、約０．０５ｍｍ〜約０．５ｍｍである。適当な層厚は使用する石英管の管径により異なるが、スート層を厚く堆積してコラプスする方が、ファイバ母材からのファイバの生産量が増えるので上記範囲内で層厚は厚いほうが好ましい。 [First deposition step (S1)]
Next, in the first deposition step S1, a glass fine particle (hereinafter sometimes referred to as soot) layer is formed on the inner peripheral surface of the hollow quartz tube. In the first deposition step, while heating the quartz tube, glass source gas, carrier gas, reaction gas, and the like are introduced from one end thereof. Thereby, a soot layer is formed by depositing glass fine particles on the inner peripheral surface of the quartz tube. The temperature for heating the quartz tube is preferably 1000 ° C. to 1600 ° C. When the heating temperature at the time of deposition exceeds 1600 ° C., the size and density of the fine particle glass fluctuate, and the additive element that soaks into the fine particle glass in the liquid immersion step S2 (described later) in which the rare earth element-containing compound is infiltrated into the fine glass particles. And undesirable effects on the doping concentration of rare earth elements. On the other hand, when fine particle glass is deposited at a low temperature of less than 1000 ° C., the soot layer may be peeled off from the quartz tube. Further, when depositing fine particles, it is preferable to control the glass internal pressure so that the internal pressure of the quartz tube is about 4 Pa lower than the atmospheric pressure.
Examples of the glass source gas used in MCVD include SiCl 4 , SiF 4 , POCl 3 , BF 3 , and BCl 3 . Further, examples of the carrier gas include He and Ar, and examples of the reaction gas include O 2 .
In general, the thickness of the soot layer to be formed is about 0.05 mm to about 0.5 mm. The appropriate layer thickness varies depending on the diameter of the quartz tube to be used. However, it is preferable to thicken the soot layer and collapse, so that the fiber production from the fiber preform increases, so the layer thickness is preferably within the above range. .

［液浸工程（Ｓ２）］
次の工程は、スート層が形成された石英管内周面に希土類元素含有化合物溶液（以下、処理液ともいう）を注入して、スート層に含浸させる液浸工程Ｓ２である。ここで、希土類元素含有化合物溶液は、希土類元素及び希土類元素との共添加物のそれぞれの塩化物または酸化物を溶解した溶液である。希土類元素含有化合物として、塩化エルビウム（ＥｒＣｌ３、ＥｒＣｌ３・６Ｈ２Ｏ）、塩化ネオジム（ＮｄＣｌ３）、塩化イッテルビウム（ＹｂＣｌ３、ＹｂＣｌ３・６Ｈ２Ｏ）、塩化ツリウム（ＴｍＣｌ３）、塩化ランタン（ＬａＣｌ３）など、共添加化合物として、ＡｌＣｌ３、ＡｌＣｌ３・６Ｈ２Ｏ、Ｐ２Ｏ５、Ｈ３ＰＯ４などが挙げられる。溶媒としてはアルコール類、水、塩酸などの極性溶媒が挙げられるが、乾燥除去の容易性からエタノールが最も好ましい。 [Immersion process (S2)]
The next step is a liquid immersion step S2 in which a rare earth element-containing compound solution (hereinafter also referred to as a processing solution) is injected into the inner peripheral surface of the quartz tube on which the soot layer is formed, and the soot layer is impregnated. Here, the rare earth element-containing compound solution is a solution in which the respective chlorides or oxides of the rare earth element and the co-additive with the rare earth element are dissolved. As the rare earth element-containing compound, erbium chloride (ErCl 3, ErCl 3 · 6H 2 O), neodymium chloride (NdCl 3), ytterbium chloride (YbCl 3, YbCl 3 · 6H 2 O), thulium chloride (TMCL 3), lanthanum chloride Examples of the co-addition compound such as (LaCl 3 ) include AlCl 3 , AlCl 3 .6H 2 O, P 2 O 5 , H 3 PO 4, and the like. Examples of the solvent include polar solvents such as alcohols, water, and hydrochloric acid, and ethanol is most preferable from the viewpoint of easy drying and removal.

希土類元素添加のファイバの特性は、希土類元素や共添加物の濃度に大きく影響される。ＹｂとＡｌを共添加する場合、各々の溶液濃度（ｗｔ％）は、０．０５≦Ｙｂ≦１．５、０．０５≦Ａｌ≦２程度の範囲であることが望ましい。また、Ｙｂのクラスタリングはガラスのフォトダークニングに影響し、ファイバレーザ特性に悪影響を及ぼすため、ＡｌとＹｂのモル比もＹｂ添加光ファイバ特性に重要なパラメータである。つまり、Ｙｂのクラスタリングを抑制するためにはＡｌとＹｂのモル比Ｒ（＝Ａl／Ｙｂ）を３≦Ｒ≦１５にすることが望ましい。この範囲の比率にすることで、ＮＡが０．０５〜０．２の光ファイバ母材を提供することができる。   The properties of rare-earth-doped fibers are greatly affected by the concentration of rare-earth elements and co-additives. When Yb and Al are co-added, the solution concentration (wt%) is preferably in the range of 0.05 ≦ Yb ≦ 1.5 and 0.05 ≦ Al ≦ 2. Further, since the clustering of Yb affects the photodarkening of glass and adversely affects the fiber laser characteristics, the molar ratio of Al to Yb is also an important parameter for the Yb-doped optical fiber characteristics. That is, in order to suppress the clustering of Yb, it is desirable that the molar ratio R (= Al / Yb) of Al and Yb is 3 ≦ R ≦ 15. By setting the ratio within this range, an optical fiber preform having an NA of 0.05 to 0.2 can be provided.

この液浸工程については、石英管内に形成されたスート層に、共添加物の溶液を含浸することができるのであれば従来の種々の方法が適用できる。その中でも、本発明者等は、処理液使用量の削減を実現しつつ、作製された光ファイバのコアＮＡやドーピング濃度の分布を均一にできる液浸方法として、図２、３に示す方法を見出したので、以下、本発明の液浸方法について説明する。
図２に示す実施形態は、スート層２１が形成された石英管１１の両端の開口にゴム栓４１および４２を挿入し、共添加成分を含む希土類元素含有化合物溶液（以下、処理液という場合がある）３１が石英管１１外に流出するのを防止しつつ、石英管１１を回転させる態様を説明している。つまり、本実施形態では、ゴム栓４１、４２を液体流出抑制手段として用いる。石英管１１をその中心軸の周りに回転させるため、下部に溜められた少量の処理液３１が、スート層２１の全面に行き渡り、微粒子ガラスに効果的に含浸される。スート層２１には凹凸形状等が形成されていないため、凹凸起因の濃度ムラが発生することはなく、均一な処理が行われる。石英管１１内への処理液３１の投入量は、石英管１１の管径やスート層２１の厚さによっても異なるが、底面に位置するスート層２１の表面から２〜５ｍｍの水位であることが好ましい。この水位は石英管１１の内容積の約２０〜４０％に相当する。 For this immersion process, various conventional methods can be applied as long as the soot layer formed in the quartz tube can be impregnated with the solution of the co-additive. Among them, the present inventors have used the method shown in FIGS. 2 and 3 as a liquid immersion method capable of making the core NA and the doping concentration distribution of the manufactured optical fiber uniform while realizing a reduction in the amount of processing liquid used. Now, the liquid immersion method of the present invention will be described.
In the embodiment shown in FIG. 2, rubber plugs 41 and 42 are inserted into openings at both ends of the quartz tube 11 in which the soot layer 21 is formed, and a rare earth element-containing compound solution containing a co-added component (hereinafter, referred to as a processing solution may be called. A mode in which the quartz tube 11 is rotated while preventing 31 from flowing out of the quartz tube 11 is described. That is, in this embodiment, the rubber plugs 41 and 42 are used as liquid outflow suppression means. Since the quartz tube 11 is rotated around its central axis, a small amount of the processing liquid 31 stored in the lower part spreads over the entire surface of the soot layer 21 and is effectively impregnated with the fine particle glass. Since the soot layer 21 is not formed with uneven shapes or the like, density unevenness due to unevenness does not occur, and uniform processing is performed. The amount of treatment liquid 31 introduced into the quartz tube 11 varies depending on the diameter of the quartz tube 11 and the thickness of the soot layer 21, but is 2 to 5 mm from the surface of the soot layer 21 located on the bottom surface. Is preferred. This water level corresponds to about 20 to 40% of the internal volume of the quartz tube 11.

石英管１１の内部への希土類元素含有化合物溶液３１の注入は種々の方法を採用できるが、その一つの形態を図３に示す。図３に示すように、一方のゴム栓４３の中央に貫通孔４４が形成されており、貫通孔４４には注入管５０が挿入される。希土類元素含有化合物溶液３１は、注入管５０から石英管１１の内部に注入される。石英管１１はガラス旋盤により回転されるので、石英管１１内での注入管５０の高さ位置に達する量の希土類元素含有化合物溶液３１は必要ではない。言い換えると、希土類元素含有化合物溶液３１は貫通孔４４から流出するほど多量に注入する必要が無い。したがって、処理液を含浸させるための石英管１１の回転の際には、注入管５０を抜き取るだけでよく、貫通孔が形成されていないゴム栓に取り替える必要は無い。なお、このとき、注入管５０を抜き取った後の貫通孔４４に栓を取り付けても良い。また、注入管５０の石英管外の形状によっては、とりつけたままで石英管１１を回転することもできる。なお、貫通孔４４のないゴム栓に取り替えてもよい。また、貫通孔４４の直径を注入管５０の挿入部の外形より大きくし、貫通孔４４内で注入管５０が自由に回転できる態様にしておけば、注入管５０を抜き取ることなく石英管１１を回転させることができる。液浸の終了後には、石英管１１の両端で止めたゴム栓４１および４２または４３を外すことで、石英管１１中の残留共添加溶液を除去することができる。   Various methods can be employed for injecting the rare earth element-containing compound solution 31 into the quartz tube 11, and one form thereof is shown in FIG. As shown in FIG. 3, a through hole 44 is formed at the center of one rubber plug 43, and an injection tube 50 is inserted into the through hole 44. The rare earth element-containing compound solution 31 is injected into the quartz tube 11 from the injection tube 50. Since the quartz tube 11 is rotated by a glass lathe, an amount of the rare earth element-containing compound solution 31 reaching the height position of the injection tube 50 in the quartz tube 11 is not necessary. In other words, the rare earth element-containing compound solution 31 does not need to be injected so much that it flows out of the through hole 44. Therefore, when the quartz tube 11 for impregnating the treatment liquid is rotated, the injection tube 50 need only be pulled out, and there is no need to replace it with a rubber stopper in which no through hole is formed. At this time, a stopper may be attached to the through hole 44 after the injection tube 50 has been extracted. Further, depending on the shape of the injection tube 50 outside the quartz tube, the quartz tube 11 can be rotated while being attached. Note that a rubber plug without the through hole 44 may be replaced. Further, if the diameter of the through hole 44 is made larger than the outer shape of the insertion portion of the injection tube 50 so that the injection tube 50 can freely rotate in the through hole 44, the quartz tube 11 can be removed without removing the injection tube 50. Can be rotated. After completion of the immersion, the residual co-added solution in the quartz tube 11 can be removed by removing the rubber stoppers 41 and 42 or 43 stopped at both ends of the quartz tube 11.

ここで、弾性材料を用いて成形された栓としては、代表的な例としてゴム栓が挙げられるが、栓の材料は、希土類元素含有化合物溶液による溶解や膨潤などが生じない材料であれば特に種類は限定されない。例えば、架橋イソプレンゴムまたは架橋ブチルゴム、架橋イソブチレン・イソプレンゴム、熱可塑性エラストマー、熱硬化性エラストマーが挙げられる。熱可塑性エラストマーとしては、ウレタン系、エチレンプロピレン系、ＥＶＡ系、ＥＥＡ系、スチレン系などの各種エラストマー、ナイロン６、ナイロン６６、ポリエステル、エチレンビニルアルコール共重合体、ポリ塩化ビニリデンなどが挙げられる。また、熱硬化性エラストマーとしては、天然あるいは合成イソプレン系、エチレンプロピレンジエンモノマー系、イソプレンイソブチレン系、ニトリルブタジエン系、クロロプレン系、またはシリコーン系エラストマーなどを主成分とするものが挙げられる。これらの中でも、シリコーン系ゴム栓が好適に用いられる。   Here, a typical example of the plug formed using an elastic material is a rubber plug, and the plug material is particularly a material that does not dissolve or swell due to the rare earth element-containing compound solution. The type is not limited. Examples thereof include crosslinked isoprene rubber or crosslinked butyl rubber, crosslinked isobutylene / isoprene rubber, thermoplastic elastomer, and thermosetting elastomer. Examples of the thermoplastic elastomer include various elastomers such as urethane, ethylene propylene, EVA, EEA, and styrene, nylon 6, nylon 66, polyester, ethylene vinyl alcohol copolymer, and polyvinylidene chloride. Examples of the thermosetting elastomer include those mainly composed of natural or synthetic isoprene-based, ethylene propylene diene monomer-based, isoprene isobutylene-based, nitrile butadiene-based, chloroprene-based, or silicone-based elastomer. Among these, silicone rubber stoppers are preferably used.

石英管の適切な回転速度は、石英管の管径によって異なる。たとえば、外径が２８ｍｍで内径が２５ｍｍの石英管の場合には、５〜２０回転／分が好ましい。この回転速度範囲であれば、石英管内面のスート層に、希土類元素含有化合物溶液を全面均一に浸透させることができる。   The appropriate rotation speed of the quartz tube varies depending on the diameter of the quartz tube. For example, in the case of a quartz tube having an outer diameter of 28 mm and an inner diameter of 25 mm, 5-20 revolutions / minute is preferable. Within this rotation speed range, the rare earth element-containing compound solution can be uniformly permeated into the soot layer on the inner surface of the quartz tube.

［乾燥拡散工程（Ｓ３）］
液浸の終了後、乾燥拡散工程Ｓ３に移る。石英管内は、残留処理液を除去後、Ｏ２ガスを流しながら自然乾燥させる。自然乾燥の時間は約１時間でよい。
乾燥後、石英管の温度を上げるために外部熱源の温度を段階的に上げ、石英管の温度を１５０℃から１５００℃に加熱する。加熱は、脱水、希土類元素含有化合物および共添加物の分解、および、それら元素の拡散を目的としているので、１５０℃から１５００℃まで段階的に石英管温度を上げることが望ましい。希土類元素含有化合物および共添加物の分解は１５０℃以上であれば起こるため、分解後に希土類元素のＥｒ、Ｙｂなどのイオンや、共添加物であるＡｌ、Ｐなどのイオンはこの乾燥拡散工程で、微粒子ガラス中に均一に拡散されて行くものと推定される。 [Drying diffusion step (S3)]
After the immersion is completed, the process proceeds to the drying diffusion step S3. The quartz tube is naturally dried while flowing an O 2 gas after removing the residual treatment liquid. The time for natural drying may be about 1 hour.
After drying, in order to raise the temperature of the quartz tube, the temperature of the external heat source is raised stepwise, and the temperature of the quartz tube is heated from 150 ° C. to 1500 ° C. The heating is aimed at dehydration, decomposition of the rare earth element-containing compound and co-additive, and diffusion of these elements, so it is desirable to raise the quartz tube temperature stepwise from 150 ° C. to 1500 ° C. Since decomposition of rare earth element-containing compounds and co-additives occurs at 150 ° C. or higher, rare earth elements such as Er and Yb ions and co-additive ions such as Al and P are decomposed in this dry diffusion step. It is presumed that it is diffused uniformly in the fine particle glass.

［第１透明化工程（Ｓ４）］
乾燥拡散工程Ｓ３に引き続き、第１透明化工程Ｓ４を実行する。透明化工程は、石英管内にＣｌ２等の脱水ガス及びＨｅなどのキャリヤガス、およびＯ２ガスを流しながら石英管温度を１５００℃から１８００℃まで上げることにより、残留する微量の水分や異物が除去され、希土類金属元素等が添加されたスート層を透明化することができる。 [First transparency step (S4)]
Subsequent to the drying diffusion step S3, the first transparency step S4 is performed. In the clearing process, the quartz tube temperature is raised from 1500 ° C. to 1800 ° C. while flowing a dehydration gas such as Cl 2 and a carrier gas such as He and O 2 gas into the quartz tube, so that a minute amount of residual moisture and foreign matter are removed. The soot layer to which the rare earth metal element or the like is added can be made transparent.

［第１コラプス工程（Ｓ５）］
第１透明化工程に引き続き、第１コラプス工程を実行してもよい。この第１コラプス工程を設けることにより、第２コラプス工程の時間を短縮し、ガラスエッチング（蒸発）をより効果的に防ぐことができる。第１コラプス工程を実行することによりガラス管の内径をある程度まで小さくすることができる。ただし、あまり小さくすると第２堆積工程でガラス原料ガスの流れが悪くなるので、内径１５〜２０ｍｍ程度にまでコラプスすることが好ましい。なお、コアが扁平になることを回避するため、石英管の内圧を、大気圧に対して０Ｐａ〜１０Ｐａ低くすることが望ましい。また、この第１コラプス工程は省略することもできる。 [First Collapse Step (S5)]
Subsequent to the first transparency process, the first collapse process may be performed. By providing this first collapse step, the time of the second collapse step can be shortened and glass etching (evaporation) can be more effectively prevented. By executing the first collapse step, the inner diameter of the glass tube can be reduced to some extent. However, if it is too small, the flow of the glass raw material gas becomes worse in the second deposition step, so it is preferable to collapse to about 15 to 20 mm in inner diameter. In order to avoid the core from becoming flat, it is desirable that the internal pressure of the quartz tube be lowered by 0 Pa to 10 Pa with respect to the atmospheric pressure. In addition, the first collapse step can be omitted.

［第２堆積工程（Ｓ６）］
その後、石英パイプの温度を、上述の第１堆積工程Ｓ１と同等の温度になるように外部の熱源を下げ、第１堆積工程で用いたものと同等のガラス原料ガス、キャリヤガス、反応ガスなどを流しながら微粒子ガラスの薄膜層（スート層）を形成した。なお、スート層の厚さが厚い場合、コアの中心屈折率プロファイルが下がる（すなわち、コア中心部の屈折率が低下する）ので、第２堆積工程で堆積するスート層の層厚は０．００１ｍｍから０．１ｍｍが好ましい。 [Second deposition step (S6)]
Thereafter, the external heat source is lowered so that the temperature of the quartz pipe becomes the same as that in the first deposition step S1, and the same glass raw material gas, carrier gas, reaction gas, etc. as those used in the first deposition step A thin film layer (soot layer) of fine particle glass was formed while flowing. In addition, when the thickness of the soot layer is thick, the core refractive index profile is lowered (that is, the refractive index at the core central portion is lowered), so the thickness of the soot layer deposited in the second deposition step is 0.001 mm. To 0.1 mm is preferable.

［第２透明化工程（Ｓ７）］
その後、第１透明化工程Ｓ４と同等の条件で、石英パイプ温度を１５００℃から１８００℃まで段階的に上げ、焼付けおよび微粒子ガラスの透明化を行う。 [Second transparency step (S7)]
Thereafter, the quartz pipe temperature is raised stepwise from 1500 ° C. to 1800 ° C. under the same conditions as in the first clarification step S4, and baking and fine particle glass are clarified.

［第２コラプス工程（Ｓ８）］
第２透明化工程Ｓ７に引き続き、同等の温度で、石英管の外部から加熱し、石英管をコラプスさせた。この第２コラプス工程Ｓ８により、希土類元素および共添加物元素がドープされた中実コアを有する光ファイバ母材が完成する。なお、コアが扁平になることを回避するため、石英管の内圧を、大気圧に対して０Ｐａ〜１０Ｐａ低くすることが望ましい。 [Second Collapse Step (S8)]
Subsequent to the second transparency step S7, the quartz tube was collapsed by heating from the outside of the quartz tube at the same temperature. By this second collapse step S8, an optical fiber preform having a solid core doped with rare earth elements and co-additive elements is completed. In order to avoid the core from becoming flat, it is desirable that the internal pressure of the quartz tube be lowered by 0 Pa to 10 Pa with respect to the atmospheric pressure.

［屈折率測定方法］
光ファイバ母材の光学特性の測定は、光ファイバ母材内部屈折率分布測定装置を用いて行った。使用した装置は、Photon Kinetics社製のプリフォームアナライザ(preform analyzer)モデルＰ１０４である。 [Refractive index measurement method]
The optical characteristics of the optical fiber preform were measured using an optical fiber preform internal refractive index distribution measuring device. The apparatus used is a preform analyzer model P104 manufactured by Photon Kinetics.

以下、本発明について、実施例を挙げてさらに具体的に説明する。本発明はこれらにより何ら限定されるものではない。   Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited by these.

［実施例］
外径２８ｍｍφ−管厚１．５ｍｍ−長さ４００ｍｍの無水石英管の内壁面に１．４ＳＬＭのＯ２を流しながら段階的に温度を上げ、１２００〜１５００℃で石英管の内壁面の空焼きを行った後、５０ＳＣＣＭのＣｌ２を流しながら１１３０℃で脱水を行った(脱水工程)。なお、ガラス旋盤による保持のため、石英管の両端に上記石英管よりも管径が大きな補助石英管を継ぎ足しても良い。補助石英管の長さは特に規定されないが、本実施例では長さ約５００ｍｍの補助石英管を用いた。この補助石英管には、スート層は形成されない。ここで、ＳＬＭおよびＳＣＣＭは、０℃基準で表記するガス流量の単位であり、それぞれ、Ｌ／ｍｉｎ、ｍＬ／ｍｉｎに相当する。
その後、０．５６ＳＬＭのＳｉＣｌ４、０．４ＳＬＭのＨｅ、０．５ＳＬＭのＯ２のガスを流しながら、１１８０℃で４回連続して、石英管内壁面へ微粒子ガラスの堆積を行った（第１堆積工程）。微粒子を堆積する際には石英管の内圧が大気圧より約４Ｐａ低くなるように石英管の内圧を制御した。 [Example]
The temperature was raised stepwise while flowing 1.4 SLM of O 2 on the inner wall surface of an anhydrous quartz tube having an outer diameter of 28 mmφ, a tube thickness of 1.5 mm, and a length of 400 mm, and the inner wall surface of the quartz tube was baked at 1200 to 1500 ° C. After dehydration, dehydration was performed at 1130 ° C. while flowing 50 SCCM of Cl 2 (dehydration step). For holding by a glass lathe, an auxiliary quartz tube having a larger diameter than the quartz tube may be added to both ends of the quartz tube. Although the length of the auxiliary quartz tube is not particularly defined, an auxiliary quartz tube having a length of about 500 mm is used in this embodiment. No soot layer is formed on the auxiliary quartz tube. Here, SLM and SCCM are units of gas flow rate expressed based on 0 ° C., and correspond to L / min and mL / min, respectively.
Thereafter, fine glass was deposited on the inner wall surface of the quartz tube four times at 1180 ° C. while flowing 0.56 SLM SiCl 4 , 0.4 SLM He, 0.5 SLM O 2 gas (first). Deposition process). When depositing the fine particles, the internal pressure of the quartz tube was controlled so that the internal pressure of the quartz tube was about 4 Pa lower than the atmospheric pressure.

次に、端部の微粒子ガラスを石英管内面から除去し、ゴム栓を用いて補助石英管の両端を封止した。別途、０．６ｇのＹｂＣｌ３・６Ｈ２Ｏ（希土類元素含有化合物）、２ｇのＡｌＣｌ３・６Ｈ２Ｏ（共添加化合物）を３００ｍＬのエタノールに溶かした希土類元素含有化合物溶液（処理液ともいう）を調製した。１５０ｍＬの希土類元素含有化合物溶液を石英管中に注入した後、ガラス旋盤のチャックに保持した状態で石英管をその中心軸の周りに１時間回転させ、石英管の内面全体に均一に希土類元素含有化合物溶液を浸透させた。このとき、注入された処理液の水位は、最も低いスート層の表面から約５ｍｍの高さであった。石英管を保持し、回転させることができるガラス旋盤のチャックの回転速度は１０回転/分で行った。ＹｂＣｌ３・６Ｈ２ＯとＡｌＣｌ３・６Ｈ２Ｏは、いずれも水溶性であり、水、アルコール類に溶けるが、乾燥工程を考慮してアルコールを溶媒として用いた。ＹｂＣｌ３・６Ｈ２Ｏ、ＡｌＣｌ３・６Ｈ２Ｏの共添加量は、目的とする光ファイバの性質によって異なるが、本実施例では、開口数（ＮＡ）が０．０６〜０．０８で、波長９１５ｎｍでのコア吸収係数が１００〜１２０ｄＢ／ｍになるように約０．５ｗｔ％のＹｂ濃度、および約０．６ｗｔ％のＡｌ濃度で共添加を行った（液浸工程）。 Next, the fine particle glass at the end was removed from the inner surface of the quartz tube, and both ends of the auxiliary quartz tube were sealed using a rubber stopper. Separately, a rare earth element-containing compound solution obtained by dissolving 0.6 g of YbCl 3 .6H 2 O (rare earth element-containing compound) and 2 g of AlCl 3 .6H 2 O (co-added compound) in 300 mL of ethanol (also referred to as a treatment liquid). Was prepared. After injecting 150 mL of a rare earth element-containing compound solution into the quartz tube, the quartz tube is rotated around its central axis for 1 hour while being held on the chuck of the glass lathe, and the entire inner surface of the quartz tube is uniformly contained. The compound solution was infiltrated. At this time, the water level of the injected processing liquid was about 5 mm from the surface of the lowest soot layer. The rotation speed of the chuck of the glass lathe capable of holding and rotating the quartz tube was 10 rpm. YbCl 3 · 6H 2 O and AlCl 3 · 6H 2 O are both water-soluble and soluble in water and alcohols, but alcohol was used as a solvent in consideration of the drying process. The co-addition amount of YbCl 3 · 6H 2 O and AlCl 3 · 6H 2 O varies depending on the properties of the target optical fiber, but in this example, the numerical aperture (NA) is 0.06 to 0.08, Co-addition was performed at a Yb concentration of about 0.5 wt% and an Al concentration of about 0.6 wt% so that the core absorption coefficient at a wavelength of 915 nm would be 100 to 120 dB / m (immersion step).

液浸処理後、石英管両端で止めたゴム栓を外し、石英管中の残留共添加溶液を流し捨てた後、Ｏ２ガスを流しながら１時間ほど自然乾燥を行った。そして、石英管温度を上げるために外部熱源の温度を段階的に上げ、１５０℃から１５００℃の石英管の温度で加熱乾燥を行った（乾燥拡散工程）。加熱乾燥は脱水、ＹｂＣｌ３・６Ｈ２Ｏ、ＡｌＣｌ３・６Ｈ２Ｏの分解および、ＡｌとＹｂを拡散させるため、１５０℃から１５００℃まで石英管の加熱温度を段階的に昇温した。ＹｂＣｌ３・６Ｈ２Ｏ、ＡｌＣｌ３・６Ｈ２Ｏの分解は１５０℃以上で起こり、生成したＹｂイオン、Ａｌイオンは加熱によって、微粒子ガラス中に均一に拡散される。
その後、石英管内の内圧を大気圧より４Ｐａ低くなるように維持し、Ｏ２流量を０．３ＳＬＭ、Ｈｅ流量を０．７ＳＬＭ、Ｃｌ２流量を２０ＳＣＣＭとして、混合ガスを流しながら石英管温度を１５００℃から１８００℃まで上げ、微粒子ガラスを透明化（第１透明化工程）し、ガラス管の内径を１５ｍｍφまで小さくした（第１コラプス工程）。
その後、石英パイプの温度を１１８０℃に低下させて維持できるように外部の熱源を制御し、０．５６ＳＬＭのＳｉＣｌ４、０．４ＳＬＭのＨｅ、０．５ＳＬＭのＯ２のガスを流しながらスート層を形成した。スート層の厚さが厚い場合、コア中心の屈折率プロファイルが下がるために本実施例では、０．００１ｍｍから０．１ｍｍが好ましい（第２堆積工程）。
その後、０．３ＳＬＭのＯ２、０．７ＳＬＭのＨｅ、２０ＳＣＣＭのＣｌ２のガスを流しながら石英パイプ温度を１５００℃から１８００℃まで段階的に上げ、再び焼付け、微粒子ガラスを透明化した（第２透明化工程）。
最後に石英管の第２コラプス工程を行った。コラプスに際しては、加熱不足により、コア中心部に気泡や空洞が発生したり、屈折率プロファイルに凹が生じたりすることがなく、逆に、加熱しすぎて、石英管が垂れたり、Ｙｂクラスタが起こらないように、適宜ヒータを移動させることで、長手方向のバラツキがない中実コアを作製した。光ファイバ母材内部屈折率分布測定装置（Photon Kinetics社製、モデルＰ１０４）による測定の結果、作製された光ファイバ母材のコア径は約２ｍｍφであった。 After the immersion treatment, the rubber stoppers stopped at both ends of the quartz tube were removed, and the residual co-added solution in the quartz tube was poured and discarded, followed by natural drying for about 1 hour while flowing O 2 gas. Then, in order to raise the temperature of the quartz tube, the temperature of the external heat source was raised stepwise, and heat drying was performed at a temperature of the quartz tube of 150 ° C. to 1500 ° C. (drying diffusion step). In the heat drying, dehydration, decomposition of YbCl 3 · 6H 2 O, AlCl 3 · 6H 2 O, and Al and Yb were diffused, and the heating temperature of the quartz tube was raised stepwise from 150 ° C. to 1500 ° C. Decomposition of YbCl 3 · 6H 2 O and AlCl 3 · 6H 2 O occurs at 150 ° C. or higher, and the generated Yb ions and Al ions are uniformly diffused in the fine particle glass by heating.
Thereafter, the internal pressure in the quartz tube is maintained to be 4 Pa lower than the atmospheric pressure, the O 2 flow rate is 0.3 SLM, the He flow rate is 0.7 SLM, the Cl 2 flow rate is 20 SCCM, and the quartz tube temperature is 1500 while flowing the mixed gas. The temperature was raised from 1 ° C. to 1800 ° C. to make the fine particle glass transparent (first transparent step), and the inner diameter of the glass tube was reduced to 15 mmφ (first collapse step).
Thereafter, an external heat source is controlled so that the temperature of the quartz pipe can be maintained at 1180 ° C., and a soot layer is supplied while flowing 0.56 SLM SiCl 4 , 0.4 SLM He, 0.5 SLM O 2 gas. Formed. When the thickness of the soot layer is thick, the refractive index profile at the center of the core is lowered. Therefore, in the present embodiment, 0.001 mm to 0.1 mm is preferable (second deposition step).
Thereafter, the quartz pipe temperature was gradually increased from 1500 ° C. to 1800 ° C. while flowing 0.3 SLM O 2 , 0.7 SLM He, and 20 SCCM Cl 2 gas, and baked again to make the fine particle glass transparent (first glass). 2 transparency process).
Finally, a second collapsing process for the quartz tube was performed. When collapsing, bubbles and cavities are not generated in the center of the core due to insufficient heating, and concaves are not formed in the refractive index profile. On the other hand, excessive heating causes the quartz tube to sag or Yb clusters to form. A solid core having no longitudinal variation was produced by appropriately moving the heater so as not to occur. As a result of measurement using an optical fiber preform internal refractive index distribution measuring apparatus (Photon Kinetics, model P104), the core diameter of the produced optical fiber preform was about 2 mmφ.

図４に、実施例で作製した光ファイバ母材のプリフォームアナライザ・モデルＰ１０４（Photon Kinetics社製）による評価結果を示す。図４において、横軸は光ファイバ母材の中心軸からの半径位置（ｍｍ）を示し、縦軸は、測定時に用いたマッチングオイルに対する母材の屈折率差を示す。コア中心部にて屈折率の凹みがない屈折率プロファイルが得られた。これは、コラプス中に添加物元素がエッチングされることが抑えられた効果である。尚、コア中心部の結晶性も向上するために光散乱による光の伝送損失が少なくなり、非線形特性の抑制、ファイバ特性の再現性や製造の安定性の向上も期待できる。   In FIG. 4, the evaluation result by the preform analyzer model P104 (made by Photon Kinetics) of the optical fiber preform produced in the Example is shown. In FIG. 4, the horizontal axis indicates the radial position (mm) from the central axis of the optical fiber preform, and the vertical axis indicates the refractive index difference of the preform with respect to the matching oil used at the time of measurement. A refractive index profile having no refractive index dent at the core central portion was obtained. This is an effect of suppressing the additive element from being etched during the collapse. In addition, since the crystallinity of the core central portion is also improved, light transmission loss due to light scattering is reduced, and nonlinear characteristics can be suppressed, fiber characteristics can be reproducible, and manufacturing stability can be expected.

また、本実施例で製造した光ファイバ母材のコアの長手方向におけるＮＡのバラツキは５％程度と小さかった。その結果、母材として用いることができる有効長さとして２４０ｍｍを確保できた。なお、コアのＮＡの長手方向のバラツキは、２４０ｍｍ長の母材の端から２０、６０、１００、１４０、１８０、２２０ｍｍの位置でＮＡ値を測定し、それらの位置でのＮＡ値の標準偏差を２倍し、それを平均のＮＡで割った値をバラツキとして算出した。得られた有効長（２４０ｍｍ）は従来の液浸方法で製造した場合に比べて２倍以上であった。このように特性のバラツキが改善されたことにより、特性の再現性や製造の安定性の確保が可能となる。   Further, the variation in NA in the longitudinal direction of the core of the optical fiber preform manufactured in this example was as small as about 5%. As a result, it was possible to secure 240 mm as an effective length that can be used as a base material. The variation in the NA of the core in the longitudinal direction is measured by measuring the NA value at positions 20, 60, 100, 140, 180, and 220 mm from the end of the 240 mm long base material, and the standard deviation of the NA value at those positions. Was doubled, and the value obtained by dividing it by the average NA was calculated as the variation. The obtained effective length (240 mm) was more than twice as compared with the case of manufacturing by the conventional liquid immersion method. Thus, by improving the variation in characteristics, it becomes possible to ensure the reproducibility of characteristics and the stability of manufacturing.

［比較例］
比較例では、実施例と同じ外径２８ｍｍφ−管厚１．５ｍｍ−長さ４００ｍｍの無水石英管を用い、実施例の第２堆積工程、第２透明化工程および第２コラプス工程を省略し、第１透明化工程に引き続いてコラプス工程を行う以外は実施例と同じ製造条件で、コア径約２ｍｍφの光ファイバ母材を製造した。図５は、比較例の製造工程を示すフローチャートである。 [Comparative example]
In the comparative example, an anhydrous quartz tube having an outer diameter of 28 mmφ, a tube thickness of 1.5 mm, and a length of 400 mm is used, and the second deposition step, the second transparency step, and the second collapse step are omitted. An optical fiber preform with a core diameter of about 2 mmφ was manufactured under the same manufacturing conditions as in the Examples except that the collapse process was performed following the first transparency process. FIG. 5 is a flowchart showing the manufacturing process of the comparative example.

図６に、比較例の製法で作製された光ファイバ母材のプリフォームアナライザ・モデルＰ１０４（Photon Kinetics社製）による評価結果を示す。図６において、横軸は光ファイバ母材の中心軸からの半径位置（ｍｍ）を示し、縦軸はマッチングオイルに対する母材の屈折率差を示す。コア中心部に屈折率の明瞭な凹みが確認できた。   FIG. 6 shows an evaluation result of an optical fiber preform manufactured by the manufacturing method of the comparative example using a preform analyzer model P104 (manufactured by Photon Kinetics). In FIG. 6, the horizontal axis indicates the radial position (mm) from the central axis of the optical fiber preform, and the vertical axis indicates the refractive index difference of the preform with respect to the matching oil. A clear recess with a refractive index could be confirmed in the core central part.

以上、説明したように、本発明の液浸ＭＣＶＤ法により、コア中心部に屈折率の凹みがない光ファイバ母材を提供することができる。加えて、液浸工程で、弾性材料からなる栓を用いて石英管内に希土類元素含有化合物溶液を封入し、石英管を回転させることで、スート層に希土類元素および共添加物元素ドーピングすることにより、少ない処理液量で、ＮＡなどのバラツキが小さく、均質な光ファイバ母材を高収率で製造することができる。   As described above, by the immersion MCVD method of the present invention, it is possible to provide an optical fiber preform that does not have a refractive index dent at the core central portion. In addition, in the immersion process, the rare earth element-containing compound solution is sealed in the quartz tube using a stopper made of an elastic material, and the quartz tube is rotated, thereby doping the soot layer with rare earth elements and co-additive elements. Thus, a uniform optical fiber preform can be produced in a high yield with a small amount of processing liquid and small variations in NA and the like.

本発明の製造方法により、コア中心部に屈折率の凹みがなく、コア中心部の結晶性の向上により光の伝送損失が少なく、非線形特性が抑制された光ファイバの提供が可能となる。しかも、ファイバ特性の再現性や製造の安定性の向上が期待できるうえに、ＮＡなどのバラツキが小さく、均質な光ファイバを高収率で製造することができる。   According to the manufacturing method of the present invention, it is possible to provide an optical fiber that has no refractive index dent at the core central portion, has a small optical transmission loss due to improved crystallinity at the core central portion, and has nonlinear characteristics suppressed. In addition, it is possible to improve the reproducibility of fiber characteristics and the stability of manufacturing, and it is possible to manufacture a homogeneous optical fiber with a small variation in NA and the like with a high yield.

１１ 石英管
２１ スート層
３１ 希土類元素含有化合物溶液（処理液）
４１，４２，４３ ゴム栓
４４ 貫通孔
５０ 注入管 11 Quartz tube 21 Soot layer 31 Rare earth element-containing compound solution (treatment liquid)
41, 42, 43 Rubber stopper 44 Through hole 50 Injection pipe

Claims (5)

ＭＣＶＤ法により石英管の内周面に形成されたガラス微粒子に、希土類元素含有化合物の溶液を含浸させることにより、希土類元素を添加する液浸工程を有する光ファイバ母材の製造方法であって、
希土類元素が添加された前記ガラス微粒子の第１透明化工程後に、さらに、ガラス微粒子を堆積する工程と、ガラス微粒子の第２透明化工程を有することを特徴とする希土類元素添加光ファイバ母材の製造方法。 A method of manufacturing an optical fiber preform having a liquid immersion step of adding a rare earth element by impregnating a glass fine particle formed on the inner peripheral surface of a quartz tube by an MCVD method with a solution of a rare earth element-containing compound,
A rare earth element-added optical fiber preform characterized by further comprising a step of depositing glass fine particles and a second transparency step of glass fine particles after the first transparency step of the glass fine particles to which the rare earth element is added. Production method. 前記第１透明化工程に続く第１コラプス工程と、前記第２透明化工程に続く第２コラプス工程とをさらに有する、請求項１に記載の製造方法。   The manufacturing method according to claim 1, further comprising: a first collapse process following the first transparency process; and a second collapse process following the second transparency process. 前記液浸工程が、前記石英管に注入された前記溶液を、前記石英管の両端に装着され、弾性材料を用いて形成された栓で封入し、前記栓が装着された石英管を中心軸の周りに回転させる工程である、ことを特徴とする請求項１または２記載の製造方法。   In the immersion step, the solution injected into the quartz tube is sealed with plugs formed at both ends of the quartz tube and formed of an elastic material, and the quartz tube with the plug is attached to a central axis. The manufacturing method according to claim 1, wherein the manufacturing method is a step of rotating around the substrate. 前記希土類元素含有化合物が、希土類元素含有化合物と共添加化合物を含み、前記光ファイバ母材の開口数が０．０５〜０．２である請求項１〜３のいずれか１項に記載の製造方法。   4. The production according to claim 1, wherein the rare earth element-containing compound includes a rare earth element-containing compound and a co-addition compound, and the numerical aperture of the optical fiber preform is 0.05 to 0.2. 5. Method. 前記希土類元素がイッテルビウム（Ｙｂ）であり、共添加元素がアルミニウム(Ａｌ)であることを特徴とする請求項４に記載の製造方法。


The method according to claim 4, wherein the rare earth element is ytterbium (Yb) and the co-added element is aluminum (Al).


JP2009007742A 2009-01-16 2009-01-16 Rare earth element-doped optical fiber preform manufacturing method Expired - Fee Related JP5384123B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2009007742A JP5384123B2 (en) 2009-01-16 2009-01-16 Rare earth element-doped optical fiber preform manufacturing method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2009007742A JP5384123B2 (en) 2009-01-16 2009-01-16 Rare earth element-doped optical fiber preform manufacturing method

Publications (2)

Publication Number Publication Date
JP2010163329A true JP2010163329A (en) 2010-07-29
JP5384123B2 JP5384123B2 (en) 2014-01-08

Family

ID=42579812

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2009007742A Expired - Fee Related JP5384123B2 (en) 2009-01-16 2009-01-16 Rare earth element-doped optical fiber preform manufacturing method

Country Status (1)

Country Link
JP (1) JP5384123B2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014143287A (en) * 2013-01-23 2014-08-07 Mitsubishi Cable Ind Ltd Rare earth doped optical fiber and method for manufacturing the same
CN117285244A (en) * 2023-11-23 2023-12-26 中国工程物理研究院激光聚变研究中心 Calibration model acquisition and calibration method for rare earth doped content and aluminum doped content

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03211504A (en) * 1990-01-17 1991-09-17 Fujitsu Ltd Production of rare earth doped fiber and preform thereof
JPH10190113A (en) * 1996-12-27 1998-07-21 Fujitsu Ltd Fiber for light amplification and its manufacture
JP2001342032A (en) * 2000-05-29 2001-12-11 Fujikura Ltd Method of manufacturing optical fiber preform by dipping process and injection plug
JP2004083399A (en) * 2002-07-02 2004-03-18 Sumitomo Electric Ind Ltd Optical fiber and method of manufacturing preform for optical fiber
JP2007091579A (en) * 2005-08-29 2007-04-12 Fujikura Ltd Method of manufacturing optical fiber preform

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03211504A (en) * 1990-01-17 1991-09-17 Fujitsu Ltd Production of rare earth doped fiber and preform thereof
JPH10190113A (en) * 1996-12-27 1998-07-21 Fujitsu Ltd Fiber for light amplification and its manufacture
JP2001342032A (en) * 2000-05-29 2001-12-11 Fujikura Ltd Method of manufacturing optical fiber preform by dipping process and injection plug
JP2004083399A (en) * 2002-07-02 2004-03-18 Sumitomo Electric Ind Ltd Optical fiber and method of manufacturing preform for optical fiber
JP2007091579A (en) * 2005-08-29 2007-04-12 Fujikura Ltd Method of manufacturing optical fiber preform

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014143287A (en) * 2013-01-23 2014-08-07 Mitsubishi Cable Ind Ltd Rare earth doped optical fiber and method for manufacturing the same
CN117285244A (en) * 2023-11-23 2023-12-26 中国工程物理研究院激光聚变研究中心 Calibration model acquisition and calibration method for rare earth doped content and aluminum doped content
CN117285244B (en) * 2023-11-23 2024-04-05 中国工程物理研究院激光聚变研究中心 Calibration model acquisition and calibration method for rare earth doped content and aluminum doped content

Also Published As

Publication number Publication date
JP5384123B2 (en) 2014-01-08

Similar Documents

Publication Publication Date Title
US9139466B2 (en) Optical fiber preform, optical fiber, and method of manufacturing optical fiber preform
US9411095B2 (en) Optical-fiber preform and method for manufacturing optical-fiber preform
CN103913800B (en) Optical fiber and optical fiber quartz glass base material
KR900002263B1 (en) Method for preparing optical-fiber preform
US6821449B2 (en) Two step etching process for an optical fiber preform
JP5903896B2 (en) Optical fiber preform manufacturing method
US20140370287A1 (en) Method for producing optical fiber preform, optical fiber preform, and optical fiber
US9340444B2 (en) Optical fiber preform manufacturing method, optical fiber preform, and optical fiber
WO2017164025A1 (en) Optical fiber
JP5657274B2 (en) Rare earth element-doped optical fiber and manufacturing method thereof
WO2020155707A1 (en) Optical fiber preform rod of large size and low loss and preparation method therefor
KR101436723B1 (en) Optical fiber
JP5384123B2 (en) Rare earth element-doped optical fiber preform manufacturing method
GB2565645A (en) Optical fiber preform
JP5329991B2 (en) Rare earth element-doped optical fiber preform manufacturing method
US20090218706A1 (en) Method of manufacturing photonic bandgap fibre
JP2014143287A (en) Rare earth doped optical fiber and method for manufacturing the same
CN113603352A (en) Active optical fiber preform with axially-doped concentration gradually changed and preparation method thereof
JP5836208B2 (en) Optical fiber preform manufacturing method
JP5384133B2 (en) Rare earth element-doped fiber doped with BF3 and manufacturing method thereof
JPH0425213B2 (en)
JP2009078928A (en) Optical fiber preform, method for producing the same and rare earth-added optical fiber
CN110734220A (en) Preparation method of phosphorus-doped active optical fibers
JP2007091579A (en) Method of manufacturing optical fiber preform
KR100321996B1 (en) Manufacturing method of doped silica glass by extrusion process

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20111026

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20130418

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20130507

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20130705

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20130730

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20130826

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20130917

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20131002

R150 Certificate of patent or registration of utility model

Ref document number: 5384123

Country of ref document: JP

Free format text: JAPANESE INTERMEDIATE CODE: R150

Free format text: JAPANESE INTERMEDIATE CODE: R150

R250 Receipt of annual fees

Free format text: JAPANESE INTERMEDIATE CODE: R250

LAPS Cancellation because of no payment of annual fees