JPS61174138A - Production of base material for optical fiber - Google Patents

Production of base material for optical fiber

Info

Publication number
JPS61174138A
JPS61174138A JP1265285A JP1265285A JPS61174138A JP S61174138 A JPS61174138 A JP S61174138A JP 1265285 A JP1265285 A JP 1265285A JP 1265285 A JP1265285 A JP 1265285A JP S61174138 A JPS61174138 A JP S61174138A
Authority
JP
Japan
Prior art keywords
base material
porous base
fluorine
optical fiber
bulk density
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
JP1265285A
Other languages
Japanese (ja)
Other versions
JPH0583498B2 (en
Inventor
Masao Hoshikawa
星川　政雄
Tsunehisa Kyodo
倫久 京藤
Koji Yano
矢野　宏司
Gotaro Tanaka
豪太郎 田中
Hiroshi Yokota
弘 横田
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.)
Sumitomo Electric Industries Ltd
Original Assignee
Sumitomo Electric 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 Sumitomo Electric Industries Ltd filed Critical Sumitomo Electric Industries Ltd
Priority to JP1265285A priority Critical patent/JPS61174138A/en
Publication of JPS61174138A publication Critical patent/JPS61174138A/en
Publication of JPH0583498B2 publication Critical patent/JPH0583498B2/ja
Granted 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
    • C03B37/012—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]
    • C03B37/01413—Reactant delivery systems
    • C03B37/0142—Reactant deposition burners
    • 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]
    • C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
    • 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]
    • C03B37/01486—Means for supporting, rotating or translating the preforms being formed, e.g. lathes
    • C03B37/01493—Deposition substrates, e.g. targets, mandrels, start rods or tubes
    • 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
    • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
    • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2207/00—Glass deposition burners
    • C03B2207/50—Multiple burner arrangements

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Glass Melting And Manufacturing (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

PURPOSE:To provide a titled base material having a refractive index distribution in a radial direction by heating a porous base material having a central hole and having a bulk density distribution in a radial direction in a fluorine-contg. atmosphere. CONSTITUTION:An upper seed bar 3-1 and a lower seed bar 3-2 are adjacently disposed in a muffle 3-10. Glass raw material is supplied from torches 3-4-5 and 3-8, 9 and while the bars 3-1, 2 are rotated, the bar 3-1 is pulled up. The porous base material 4-2 having the central hole 3-11, consisting of an inside layer 3-6 and an outside layer 3-7 and having the bulk density distribution in the radial direction is obtd. Such base material 4-2 is charged into a muffle 4-3 and is heated in a heating furnace 4-1; at the same time a non-fluorine dehydrating gas and diluting gas are admitted into the furnace through an inlet 4-6 and a fluorine-contg. gas is supplied therein through an inlet 4-4 at the same instant by which the base material is heat-treated and the transparent glass base material having the refractive index distribution is obtd.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は光ファイバ特にシングルモードファイバの製造
方法に係わる。DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing optical fibers, particularly single mode fibers.

（従来の技術） 光ファイバは、中心部に屈折率の高い活性領域と、その
周辺を取シま〈該活性領域よりも屈折率の低い非活性領
域から形成される。このような光ファイバの製造方法と
しては、従来よシ種々の方法が開発され実用に供されて
おり、例えば、Ｍ−Ｃ’ｌＤ法（Ｍｏ１ｆｌｅｄ　Ｃｈ
ｅｍｌｃａｌ　ｖａｐｏｒＤｅｐｏｓｌｔｌｏｎ　　内
付けｃｖｎ法）、ＷＡＤ法（Ｖ’ａｐｏｒＰｈａｓ＠Ａ
ｘｌａｌ　Ｄｅｐｏｓｌｔｌｏｎ　Ｍ＠ｔｈｏｄ気相軸
付は法）、ｏｖ’ｎ法（０ｕｔｓｌａｅ　Ｖａｐｏｒ　
Ｄｒｐｏｓｌｔｌｏｎ　Ｍｅｔｈｏｄ外付は法）等がそ
の代表例である。これらの製造方法において、活性領域
を構成する材料としては、主として８１ｏｇ　／　Ｇ・
０３系ガラスが用いられ、非活性領域構成材料としては
主として８１０．が用いられている。(Prior Art) An optical fiber is formed of an active region with a high refractive index in the center and an inactive region with a lower refractive index around the active region. As methods for manufacturing such optical fibers, various methods have been developed and put into practical use. For example, the M-C'ID method (Mo1fled Ch
emlcal vaporDeposltlon internal cvn method), WAD method (V'aporPhas@A
xlal Deposltlon M@thod method), ov'n method (0utslae Vapor
A typical example is Drposltlon Method. In these manufacturing methods, the material constituting the active region is mainly 81og/G・
03 series glass is used, and 810. is used.

ところで、光は活性領域において集中伝送され、この部
分の材料としては、最も光損失の小さな材料、即ちＳｔ
Ｏ，を用いるのがむしろ理想的である。一方、非活性領
域の屈折率は活性領域のそれよ）も小さくする必要があ
るため、ＳｔＯ。By the way, light is concentratedly transmitted in the active region, and this part is made of a material with the smallest optical loss, that is, St
It is rather ideal to use O. On the other hand, since the refractive index of the non-active region needs to be smaller than that of the active region, StO.

に添加剤としてＢ、Ｏ，、ＩＦ等屈折率低下用ドーパン
トを加える。光７アイパの用途によってはＢ、０３を使
用することもできるが、長波長帯すなわち１　ｐｍ以上
の光を伝送する場合には、Ｂ−０ボンド存在による遠赤
外領域での光吸収のために１使用が好ましくない場合が
ある。その点において、光ファイバの使用波長帯では特
別な吸収ピークのないアは、添加剤として理想的である
。A dopant for lowering the refractive index, such as B, O, or IF, is added as an additive. B, 03 can be used depending on the application of Hikari 7 Eyepa, but when transmitting light in the long wavelength band, that is, 1 pm or more, it is necessary to There are cases where it is not desirable to use 1. In this respect, A, which has no particular absorption peak in the wavelength band used by optical fibers, is ideal as an additive.

従って、活性領域は主としてＳｔＯ，を、非活性領域は
主として８１０２　／　Ｆ系ガラスを用いて、屈折率を
調整することが好ましい。このようなファイバ構造とし
ては、例えば特公昭５５−１５６８２号公報に詳細に記
載されている。Therefore, it is preferable to adjust the refractive index by using mainly StO in the active region and mainly using 8102/F glass in the non-active region. Such a fiber structure is described in detail in, for example, Japanese Patent Publication No. 55-15682.

また上記構造のファイバを製造する方法としては、例え
ば石英棒の周囲に熱プラズマによって、ｒを添加した石
英ガラスを、半径方向くガラス状態にて堆積する方法、
石英棒のまわシに、ｒを添加した石英微粉末を半径方向
に堆積させ、これを焼結しガラス母材とする方法、およ
びＭ−ｃｖｎ法により、石英管内面にまず１を添加した
石英ガラス層を堆積せしめて非活性領域に相当する部分
を作った後、無添加の石英ガラス層を堆積し、ついで中
空部をつぶして中実な棒としてガラス母材とする方法等
がある。Further, as a method for manufacturing a fiber having the above structure, for example, a method in which quartz glass doped with r is deposited in a glass state in the radial direction around a quartz rod using thermal plasma;
First, quartz powder doped with R is deposited on the inner surface of a quartz tube by a method of depositing fine quartz powder doped with R in the radial direction on a quartz rod and sintering it to form a glass base material, and by the M-cvn method. After depositing a glass layer to form a portion corresponding to a non-active region, there is a method of depositing an additive-free quartz glass layer, and then crushing the hollow portion to form a solid rod as a glass base material.

（発明が解決しようとする問題点） しかしながら、上記の熱プラズマによる方法では、石英
棒と、積層する１添加の石英との間の汚染および、１添
加石英自体のＯＨ基による汚染によって、充分に低損失
の光ファイバを得ることは困難である。を九石英棒のま
わシに火炎加水分解法によシ１添加ガラス微粉末をつけ
てゆく方法では、石英棒表面に最初から吸着されている
水分および、火炎加水分解法によシ１添加ガラス微粉末
を堆積させるときに石英棒表面からのＯＨ基の侵入（微
粉末の水分はとれやすいか、ガラス表面から入る水分を
取ることは極めて困難である。）により、やはシ充分に
低損失の光ファイバは得難い。Ｍ−ＯＶＤ法によれば比
較的特性の良いファイバを得ることができるが、生産性
に乏しいという欠点があった。、本発明は、以上に述べ
た従来の製法が有する０１１　基による光ファイバの特
性の劣化および生産性の低さという問題を克服した、活
性領域が主として石英、非活性領域が弗素を添加した石
英ガラスからなる光ファイバを得ることのできる全く新
規な光ファイバ用母材の製造方法を提供することを目的
とする。(Problems to be Solved by the Invention) However, in the above method using thermal plasma, the problem is insufficient due to contamination between the quartz rod and the laminated 1-doped quartz and contamination by OH groups of the 1-doped quartz itself. Obtaining low-loss optical fibers is difficult. In the method of applying 1-added glass fine powder to a quartz rod by flame hydrolysis, the moisture adsorbed on the surface of the quartz rod from the beginning and the 1-added glass powder by flame hydrolysis are removed. When depositing fine powder, OH groups enter from the surface of the quartz rod (it is easy to remove moisture from fine powder, or it is extremely difficult to remove moisture from the glass surface), resulting in a sufficiently low loss. Optical fiber is difficult to obtain. Although it is possible to obtain a fiber with relatively good characteristics using the M-OVD method, it has the drawback of poor productivity. The present invention overcomes the problems of deterioration of optical fiber characteristics and low productivity caused by 011 groups in the conventional manufacturing method described above. It is an object of the present invention to provide a completely new method for manufacturing an optical fiber base material that can produce an optical fiber made of glass.

（問題点を解決するための手段） すなわち本発明は、中心孔を有し、半径方向にがさ密度
分布を有する多孔質母材を、弗素又は弗素を含む雰囲気
中にさらして加熱することによシ、半径方向に屈折率分
布を有する透明ガラス母材を得ることを特徴とする光フ
ァイバ用母材の製造方法、である。(Means for Solving the Problems) That is, the present invention involves heating a porous base material having a central hole and having a radial density distribution by exposing it to fluorine or an atmosphere containing fluorine. This is a method for producing an optical fiber preform, which is characterized by obtaining a transparent glass preform having a refractive index distribution in the radial direction.

本発明の特に好ましい実施態様としては、上記の方法に
おいて長手方向一対向して、互の一端が隣り合うように
配置された２本の種棒の隣接する付近より多孔質母材を
形成し、該多孔質母材の種棒長手方向成長とともに少く
とも一方の種棒を該長手方向に移動せしめることにより
形成される、中心孔を有し、半径方向にかさ密度分布を
有する多孔質母材を、弗素又は弗素を含む雰囲気中にさ
らして加熱することによシ、半径方向に屈折率分布を有
する透明ガラス母材を得ることがあげられる。In a particularly preferred embodiment of the present invention, in the above method, a porous base material is formed from the adjacent vicinity of two seed rods that are arranged to face each other in the longitudinal direction so that one end of each other is adjacent to each other, A porous base material having a central hole and having a bulk density distribution in the radial direction, which is formed by moving at least one seed rod in the longitudinal direction as the seed rods of the porous base material grow in the longitudinal direction. A transparent glass base material having a refractive index distribution in the radial direction can be obtained by exposing it to fluorine or an atmosphere containing fluorine and heating it.

以下本発明の方法について詳細に説明する。The method of the present invention will be explained in detail below.

本発明者らは石英への弗素添加のメカニズムについて鋭
意研究の結果、以下の如き知見を得た。すなわち、弗素
を添加された石英の屈折率ｎは石英のそれより小さくな
るが、この時の石英の屈折率に対する減少率を百分率に
て表したものを１戊１とすると、１−１は下記（１）式
にて与えられる。The present inventors have made the following findings as a result of intensive research into the mechanism of fluorine addition to quartz. In other words, the refractive index n of fluorine-doped quartz is smaller than that of quartz, but if the rate of decrease with respect to the refractive index of quartz is expressed in percentage as 1 1, then 1-1 is as follows. It is given by equation (1).

ここで１Ｆ日ＩＰＩＩは雰囲気ガスとしてｓ−ｙ＠を用
ｔｎた場合の８Ｆ、ガスの分圧、Ｒはボルツマン定数（
１，９８７ｃｌＬ”ｄｅｇ＊ｍｏｌ　）、およびＴは雰
囲気の絶対温度を表す。Here, 1F day IPII is 8F when s-y@ is used as the atmospheric gas, gas partial pressure, R is Boltzmann constant (
1,987 clL"deg*mol), and T represents the absolute temperature of the atmosphere.

（１）式によればし鵠１は雰囲気温度に対して極めて敏
感であることがわかる。According to equation (1), it can be seen that Mouse 1 is extremely sensitive to ambient temperature.

第１図は、火炎加水分解反応により生成せしめた石英微
粉末を、温度条件を変えながら、分圧α０２の８Ｆｇ雰
囲気中に３時間曝し、次いで雰囲気中からｓｙ−を除去
し、温度１６５０℃、Ｈｅ１ＧＧ容量チ雰囲気にて該石
英微粉末を透明化して得た、弗素添加ガラスの、石英に
対する屈折率の低下率（チ）を示す。この場合のカサ密
度は約０３であった。なお図中の○印は、８１Ｆｇを含
む雰囲気中で各温度条件で処理し、１６５０℃で透明ガ
ラス化した場合に得られたガラスの屈折率低下率の実験
値である。なおグラフ中’Ｉ’　（Ｃ）は温度を、１ｏ
ａ／　Ｔ　（’Ｋ）は絶対温度の逆数を示す。Figure 1 shows that fine quartz powder produced by flame hydrolysis reaction is exposed to an 8Fg atmosphere with a partial pressure α02 for 3 hours while changing the temperature conditions, then sy- is removed from the atmosphere, and the temperature is 1650°C. The reduction rate (chi) of the refractive index relative to quartz of the fluorine-doped glass obtained by making the quartz fine powder transparent in a He1GG capacitance atmosphere is shown. The bulk density in this case was approximately 0.03. Note that the ○ marks in the figure are experimental values of the refractive index reduction rate of the glass obtained when the glass was treated under various temperature conditions in an atmosphere containing 81Fg and turned into transparent vitrification at 1650°C. In addition, 'I' (C) in the graph represents the temperature, 1o
a/T ('K) indicates the reciprocal of absolute temperature.

ことで石英に対する弗素の添加率は、下記の化学式（２
）に従う可逆反応である。Therefore, the addition rate of fluorine to quartz can be calculated using the following chemical formula (2
) is a reversible reaction.

４８１０！　＋　８Ｐ＠　＃４８１０１．５　ｙ＋ｓｏ
、ｙ、　　　＋＊＋（２）（−）　　（ｇ）　　　（−
）　　　（ｇ）Ｓ：固体 ｇ：気体 上記（２）弐において、反応の右辺への進行の程度は、
（１）式によってきまる（ｙ添加量はすなわち４８１０
．．５１Ｆの生成量であって、これは（１）式により決
まる）が、このことはほぼ雰囲気温度により決定される
ことを意味する。すなわち、弗素の石英への添加の度合
は（１）式でもわかるように濃度依存性と共に著しい温
度依存性を持っている。4810! + 8P @ #48101.5 y+so
,y, +*+(2)(-) (g) (-
) (g) S: solid g: gas In (2) 2 above, the degree of progress of the reaction to the right side is:
It is determined by the formula (1) (the amount of y added is 4810
．． ．． 51F (which is determined by equation (1)) is approximately determined by the ambient temperature. That is, as can be seen from equation (1), the degree of addition of fluorine to quartz has both concentration dependence and significant temperature dependence.

次に、弗素の石英への添加量は、石英微粉末のかさ密度
に依存する。第２図に、石英微粉末のかさ密度と比屈折
率差１．Ｍ（Ｆ）Ｉ　　との関係を示す。これは、温度
１２００℃、Ｂ１＃の分圧α０２（残はＨｅ　）　　の
炉中に、かさ密度の異なる石英の多孔質母材（石英微粉
末の集ったもの）を３時間入れた後、１６５０℃で透明
ガラス化した後に、石英の屈折率に対する屈折率変化を
測定したものを示す。Next, the amount of fluorine added to quartz depends on the bulk density of fine quartz powder. Figure 2 shows the bulk density and relative refractive index difference of quartz fine powder. The relationship with M(F)I is shown. This is done by placing porous quartz base materials (a collection of fine quartz powder) with different bulk densities in a furnace at a temperature of 1200°C and a partial pressure of B1# α02 (the remainder being He) for 3 hours. The graph shows the measurement of the refractive index change with respect to the refractive index of quartz after it was made into transparent glass at 1650°C.

第２図から明らかなように、同じ温度、時間、８１Ｆ＠
分圧雰囲気中に曝しても、多孔質母材のかさ密度によっ
て、添加される弗素量には大きな差が生じる。すなわち
弗素添加量は、著しいかさ密度依存性を持つことがわか
る。As is clear from Figure 2, the same temperature and time, 81F@
Even when exposed to a partial pressure atmosphere, the amount of fluorine added varies greatly depending on the bulk density of the porous base material. In other words, it can be seen that the amount of fluorine added has a significant dependence on bulk density.

ところで、多孔質母材の脱水性、すなわち、一定の脱水
剤を含むある温度雰囲気に多孔質母材をさらし、該多孔
質母材をさらに高温で透明ガラス化した場合の残留ＯＨ
量は、多孔質母材のかさ密度に大きく依存し、かさ密度
が高いほど残留ＯＨ量の多いことはよく知られている。By the way, the dehydration property of a porous base material, that is, the residual OH when the porous base material is exposed to a certain temperature atmosphere containing a certain dehydrating agent and the porous base material is turned into transparent glass at a higher temperature.
It is well known that the amount largely depends on the bulk density of the porous matrix, and that the higher the bulk density, the greater the amount of residual OH.

したがって、石英多孔質母材への適切な弗素添加を行う
ためには、特に、温度、がさ密度の選択と共に１脱水の
方法についても考慮する必要がある。Therefore, in order to appropriately add fluorine to the quartz porous base material, it is necessary to take into account the selection of temperature and bulk density, as well as the dehydration method.

本発明者らは以上の諸点を考慮し、残留。■量が極めて
少なく実質的に石英を活性領域とし、弗素が添加された
石英を非活性領域とする、伝送損失の極めて小さな光フ
ァイバの製法に到達した。The inventors of the present invention have considered the above points and have made the following decisions. (2) We have achieved a method for manufacturing an optical fiber with extremely low transmission loss, in which the active region is substantially made of quartz and the inactive region is made of fluorine-doped quartz.

以下、具体的に説明するが、以下に述べる方法及び実施
例は、あくまで本発明の例示にすぎず、また各図におけ
る各部の位置、相対的配置関係、大きさ、形状等はこれ
に限定されるものではないことは、言うまでもない。Although detailed explanations will be given below, the methods and examples described below are merely illustrative of the present invention, and the positions, relative arrangement relationships, sizes, shapes, etc. of each part in each figure are limited to these. Needless to say, this is not something that can be done.

第３図は本発明に係わる多孔質母材形成の方法を説明す
る図である。図中３−１は引き上げ用種棒、５−２は下
部種棒、３−４は内層用トーチであり、高かさ密度多孔
質母材（以下内層多孔質母材という）３−６を形成する
。３−５は外層用トーチであり、低かさ密度多孔質母材
（以下外層多孔質母材という）５−７を形成する。内層
、外層各トーチ３−４．３−５には、少くとも■雪を含
む可燃性ガス、０．および５ＩＯ１４等の、化学反応に
より８１０．を生じる原料等が供給される。なお、内層
用トーチでは、かさ密度を高くするため火炎の温度が外
層用トーチよシ高く々つている。内１外層各トーチ５−
４および３−５の出口の火炎中で加水分解反応が起こり
、ＥｉｌＯ，微粒子が形成され、該微粒子は夫々内層お
よび外層多孔質母材３−６および５−７となって長手方
向に成長してゆく。５−８．５−９は多孔質母材に付着
しなかった８１０鵞粒子等を排気する排気管であり、５
−１０は系全体を覆うマツフルである。FIG. 3 is a diagram illustrating a method of forming a porous base material according to the present invention. In the figure, 3-1 is a pulling seed rod, 5-2 is a lower seed rod, and 3-4 is a torch for inner layer, forming a high bulk density porous base material (hereinafter referred to as inner layer porous base material) 3-6. do. Reference numeral 3-5 denotes an outer layer torch, which forms a low bulk density porous base material (hereinafter referred to as outer layer porous base material) 5-7. Each of the inner and outer layer torches 3-4 and 3-5 contains at least ■ combustible gas containing snow; and 5IO14, etc., by chemical reaction, 810. Raw materials, etc. that produce Note that in the case of the inner layer torch, the flame temperature is higher than that of the outer layer torch in order to increase the bulk density. Inner 1 outer layer each torch 5-
A hydrolysis reaction occurs in the flame at the exits of 4 and 3-5, forming EilO fine particles, which grow in the longitudinal direction to become inner and outer porous matrices 3-6 and 5-7, respectively. I'm going to go. 5-8.5-9 is an exhaust pipe for exhausting 810 particles that did not adhere to the porous base material, and 5-8.
-10 is a pine full covering the entire system.

さて、多孔質母材形成の出発時には、引き上げ上種棒３
−１は、下部種棒３−２と隣接状態にあり、この状態で
まず内層用トーチ３−４によって、内層多孔質母材３−
６を形成する。多孔質母材はその成長とともに回転しな
がら上部に引き上げられてゆく。なお、下部種棒は、下
部に位置は固定されているが、引上げ用種棒とほぼ同じ
回転速度で自由に回転し得るようになっており、多孔質
母材成長とともに下部種棒が抜けてゆく状態となる。し
たがって、そのあとに多孔質母材中心部に中心孔３−１
１ができる。Now, at the start of forming the porous base material, the upper seed rod 3 is pulled up.
-1 is in a state adjacent to the lower seed rod 3-2, and in this state, first, the inner layer porous base material 3-
form 6. As the porous base material grows, it is pulled upward while rotating. The position of the lower seed rod is fixed at the bottom, but it can rotate freely at approximately the same rotational speed as the pulling seed rod, and as the porous base material grows, the lower seed rod comes out. It becomes a state of going. Therefore, after that, the center hole 3-1 is placed in the center of the porous base material.
1 can be done.

なお下部種棒は回転可能ではあるが、必ずしも引上用種
棒とともに回転させなくてもよい。Although the lower seed rod is rotatable, it does not necessarily have to be rotated together with the pulling seed rod.

以上の方法によシ、内外層を有する多孔質母材を長手方
向に形成することができる。なお、多孔質母材の把持を
よくするため、引き上げ用種棒の先端を３−３のように
加工したものを用いてもよい。By the above method, a porous base material having inner and outer layers can be formed in the longitudinal direction. In addition, in order to better grip the porous base material, a pulling seed rod whose tip is processed as shown in 3-3 may be used.

本発明方法に用いる引上げ用種棒として、例えば石英管
、また下部種棒としては例えばアルミナ、ジルコニア棒
等が用いられるが、これ等に限定されるものではない。The pulling seed rod used in the method of the present invention may be, for example, a quartz tube, and the lower seed rod may be, for example, an alumina or zirconia rod, but is not limited to these.

通常行われている方法では、細長い一本の出発棒の上に
、半径方向に多孔質母材を形成し、その後多孔質母材か
ら該出発棒を引きぬく方法がとられるが、この従来法で
は多孔質母材が長尺になると出発棒が引き抜き難くなシ
、引き抜きの際に多孔質母材が破壊されたり、中心孔表
面に傷がついたりして長尺の母材を得るのが難かしいと
いう欠点がある。In the conventional method, a porous base material is formed in the radial direction on a single elongated starting rod, and then the starting rod is pulled out from the porous base material. However, if the porous base material becomes long, it becomes difficult to pull out the starting rod, and the porous base material may be destroyed or the center hole surface may be scratched during pulling out, making it difficult to obtain a long base material. The drawback is that it is difficult.

しかし、本発明の方法は、長手方向に対向して互の一端
が隣接するように配置された２本の種棒の該隣接部分付
近より、ガラス微粒子の集合体よりなる多孔質母材を形
成し、該多孔質母材の長手方向成長とともに、少なくと
も一方の種棒をその長手方向に移動せしめることにより
、中心孔を有し、半径方向にがさ密度分布を有する多孔
質母材を製造するので、上記の従来法の欠点は解消され
、長尺の内外層を有する多孔質母材を得ることができる
。However, in the method of the present invention, a porous base material made of an aggregate of glass fine particles is formed from the vicinity of the adjacent portions of two seed rods that are arranged to face each other in the longitudinal direction and have one end adjacent to each other. Then, as the porous base material grows in the longitudinal direction, at least one of the seed rods is moved in the longitudinal direction of the porous base material, thereby producing a porous base material having a central hole and having a bulge density distribution in the radial direction. Therefore, the drawbacks of the conventional method described above are overcome, and a porous base material having elongated inner and outer layers can be obtained.

なお、内層多孔質母材３−６のかさ密度を調整するため
、トーチ３−４だけでなく、図示されていないが加熱の
ためのトーチを用いてもよいし、その他の補助加熱手段
を用いてもよい。In addition, in order to adjust the bulk density of the inner porous base material 3-6, not only the torch 3-4 but also a heating torch (not shown) may be used, or other auxiliary heating means may be used. It's okay.

次に以上のようＫして得られた多孔質母材に、弗素添加
、脱水、焼結を行う本発明方法の１例につき述べる。Next, an example of the method of the present invention will be described in which the porous base material obtained by K as described above is subjected to fluorine addition, dehydration, and sintering.

第４図は、脱水及び弗素添加の一実施態様を説明する図
である。４−１は加熱炉であシ、多孔質母材４−２を加
熱する。４−３はマツフル、４−５は雰囲気ガスの排気
孔である。引上げ用種棒をそのインレット４−６を通し
て、非弗素の脱水ガス及び希釈ガス、例えばＣ４及びＨ
ｅ等を流入せしめる。また、マツフル４−３の下部よジ
インレット４−４を通じて、Ｐ富ガス又は高温で分解し
て弗素となる気体化合物及び希釈−ガス並びに場合によ
れば０４など脱水ガスを流入せしめる。FIG. 4 is a diagram illustrating one embodiment of dehydration and fluoridation. 4-1 is a heating furnace that heats the porous base material 4-2. 4-3 is a matsufuru, and 4-5 is an atmospheric gas exhaust hole. The pulling seed rod is passed through its inlet 4-6 to supply non-fluorine dehydration gas and diluent gas, such as C4 and H
e, etc. are allowed to flow in. In addition, a P-rich gas or a gaseous compound that decomposes into fluorine at high temperatures, a diluent gas, and, if necessary, a dehydrated gas such as 04 are allowed to flow into the lower part of the Matsufuru 4-3 through the inlet 4-4.

このとき、多孔質母材４−２の下部をあらかじめ閉じて
おくと、多孔質母材の内層の脱水に関してよシ有効であ
るが、開口しておいてもかまわない。At this time, it is more effective to dehydrate the inner layer of the porous base material if the lower part of the porous base material 4-2 is closed in advance, but it may be left open.

この状態で、引き上げ用種棒を、回転しながら引き下し
、加熱炉４−１の高温部を、該多孔質母材４−２が通過
するようＫしてやる。表お、適当な速度で多孔質母材を
引き下すととＫよシ高温部を通過する多孔質母材の断面
内温変分布を適当に調整することが可能である。このよ
うＫ、内層多孔質母材はＣＩ４等の脱水ガスに常時直接
さらされておシ、かつ多孔質母材の下部を閉じることＫ
よシ、加圧して脱水ガスを内層多孔質母材に送ることも
可能となり、脱水が極めて効果的に行われる。In this state, the pulling seed rod is pulled down while rotating, and heated so that the porous base material 4-2 passes through the high temperature section of the heating furnace 4-1. In addition, if the porous base material is pulled down at an appropriate speed, it is possible to appropriately adjust the temperature variation distribution within the cross section of the porous base material that passes through the high temperature section. In this way, the inner layer porous base material is always directly exposed to dehydration gas such as CI4, and the lower part of the porous base material is closed.
Additionally, it becomes possible to pressurize and send dehydration gas to the inner porous base material, and dehydration is performed extremely effectively.

即ち、中心孔を有しない多孔質母材の場合、中心部分に
高かさ密度の部分、その周辺に低かさ密度の部分がある
が、この場合、脱水の困難な部分が多孔質母材の中心に
存在することになり、多孔質母材の周辺より侵入するＣ
Ｉ４等の脱水ガスによってしか脱水されない。本発明の
方法では多孔質母材に中心孔があり、この中心孔附近が
高かさ密度であるため、上述したようＫ　　・直接脱水
ガスに常時さらされ、かつまた多孔質母材の下部を閉じ
ることにより、中心孔の一方の開口部より脱水ガスを圧
力により強制侵入せしめることによって、脱水効果がさ
らに高まるととＫなる。In other words, in the case of a porous base material that does not have a central pore, there is a part with high bulk density in the center and a part with low bulk density around it. C that enters from the periphery of the porous base material.
It can only be dehydrated by dehydrating gas such as I4. In the method of the present invention, the porous base material has a central hole, and since the area around the central hole has a high bulk density, it is constantly exposed to the K and direct dehydration gas as described above, and the lower part of the porous base material is closed. By forcing the dehydration gas to enter through one opening of the center hole under pressure, the dehydration effect is further enhanced.

以上により、かさ密度の高さによる脱水効果の低減とい
う問題が克服できる。With the above, the problem of reduced dehydration effect due to high bulk density can be overcome.

一方、多孔質母材外部より弗素が浸入し、外層多孔質母
材への弗素添加が有効に行われる。On the other hand, fluorine infiltrates from the outside of the porous base material, and fluorine is effectively added to the outer porous base material.

すなわち、内層多孔質母材は、殆んど弗素雰囲気にさら
されず、さらに、かさ密度が高いために弗素添加が殆ん
ど起らず、かつ、前述の如く脱水が効果的に行われるた
め、低損失でかつ、所定の屈折率分布が得られる。That is, the inner porous base material is hardly exposed to a fluorine atmosphere, and furthermore, because of its high bulk density, fluorine addition hardly occurs, and dehydration is effectively performed as described above. A predetermined refractive index distribution can be obtained with low loss.

効果的な脱水と、弗素添加量の温度依存性を更に効果的
に行う他の実施態様を以下に述べる。Other embodiments that achieve effective dehydration and even more effective temperature dependence of the amount of fluorine added will be described below.

第４図の構成において、多孔質母材４−２の中心孔の下
方を開放しておき、まず第１ステツプとしてインレット
４−４及び４−６よシ、脱水ガスと希釈ガスを流しなが
ら、多孔質母材４−２を加熱炉４−１の高温部を通過せ
しめる。In the configuration shown in FIG. 4, the lower part of the center hole of the porous base material 4-2 is left open, and as a first step, while flowing dehydration gas and dilution gas through the inlets 4-4 and 4-6, The porous base material 4-2 is passed through the high temperature section of the heating furnace 4-1.

このときインレット４−６を通すガスの流量は極めて小
さくシ、中心孔が冷却され々いように注意する。多孔質
母材４−２が加熱炉４−１を全部通過し終って後、母材
を炉の上部に−たん引上げる。At this time, the flow rate of the gas passing through the inlet 4-6 should be extremely small so that the center hole is not sufficiently cooled. After the porous base material 4-2 has completely passed through the heating furnace 4-1, the base material is pulled up to the upper part of the furnace.

次に第２ステツプとして、インレット４−６から以前よ
りも大きい流速で、脱水ガスと希釈ガスを流し、かつイ
ンレット４−４から弗素添加用ガスおよび希釈ガスおよ
び必要に応じて脱水ガスからなる混合ガスを流入せしめ
る。このとき、インレット４−４から流入されるガスが
中心孔に入らないようにインレット４−６に流入させる
ガスの流速をより大きくする必要がある。との状態で、
再び多孔質母材を引き下げ、加熱炉高温部を通過させる
。Next, as a second step, the dehydration gas and the diluent gas are flowed from the inlet 4-6 at a higher flow rate than before, and the mixture consisting of the fluoridation gas and the diluent gas and, if necessary, the dehydration gas is flowed from the inlet 4-4. Allow gas to flow in. At this time, it is necessary to increase the flow rate of the gas flowing into the inlet 4-6 so that the gas flowing from the inlet 4-4 does not enter the center hole. In the state of
The porous base material is pulled down again and passed through the high temperature section of the heating furnace.

かくすることＫよシ、第１ステツプで脱水が行われ、第
２ステツプで中心孔付近が冷却されることによる弗素添
加抑制効果が可能となり、効果的な弗素添加及び脱水が
共に行われることに表る。In this way, dehydration is performed in the first step, and the vicinity of the center hole is cooled in the second step, thereby making it possible to suppress the addition of fluorine, and thereby effectively performing both the addition of fluorine and the dehydration. appear.

第５図は、本発明方法によシ、脱水及び弗素添加された
多孔質母材４−２′を、焼結して透明ガラス化する方法
の１例を示すものである。多孔質母材４−２′をマツフ
ル４−３の上部に引上げ、加熱炉４−１の温度を上昇せ
しめる。所定の温度に到達後、インレット４−４より■
・　を主体とするガスを流しながら、引上げ用種棒３−
１を回転しながら下降せしめる。かくすることにより、
多孔質母材４−２′は全体に透明化し、半径方向に屈折
率分布のついた透明母材となる。FIG. 5 shows an example of a method for sintering a porous base material 4-2' which has been subjected to dehydration and fluorine addition according to the method of the present invention to form transparent glass. The porous base material 4-2' is pulled up to the top of the matsufuru 4-3, and the temperature of the heating furnace 4-1 is raised. After reaching the specified temperature, from inlet 4-4■
・ While flowing a gas mainly consisting of
1 and lower it while rotating it. By doing so,
The porous base material 4-2' becomes transparent as a whole and has a refractive index distribution in the radial direction.

なお、多孔質母材４−２′を透明化しながら、引き上げ
用種棒３−１から■・　ガスを流してもよい。また中心
孔が大きく孔が閉じＫ〈い場合には、引き上げ用種棒３
−１から真空引きを行ってもよい。かくすることＫよシ
、多孔質母材４−２′中に残留していたｃ４ガスが完全
に排気され、気泡のない透明母材が得やすくなる。Note that while the porous base material 4-2' is made transparent, the gas may be flowed from the pulling seed rod 3-1. In addition, if the center hole is large and the hole is not closed, the pulling seed rod 3
Vacuuming may be performed from -1. By doing so, the C4 gas remaining in the porous base material 4-2' is completely exhausted, making it easier to obtain a transparent base material free of bubbles.

以上詳述した、本発明の多孔質母材の脱水、弗素添加及
び焼結の方法は、これを要するに１中心孔を有し半径方
向にかさ密度分布を有する多孔質母材を、少なくとも弗
素を含む化合物ガス含有雰囲気中にさらし、しかる後こ
れを透明化して、半径方向に屈折率分布を有する透明母
材を得ることを特徴とするものである。The method of dehydrating, adding fluorine, and sintering a porous base material of the present invention, which has been described in detail above, basically consists of a porous base material having one central hole and a bulk density distribution in the radial direction. The method is characterized in that a transparent base material having a refractive index distribution in the radial direction is obtained by exposing the base material to an atmosphere containing a compound gas and then making it transparent.

なお弗素含有ガスとして、上記では８１Ｆ＠を例に述べ
たが、これに限らず、例えば８１１Ｐ４．００！４’ｌ
’＊、ｃ　ｃｔＩＦ、、ＳＯＷ、、８ｅｌＦｇ、ｃｙ４
、ｍ、ｙ、　Ｆ、ｌｉ、　　等を用いることもできる。In addition, although 81F@ was mentioned as an example of the fluorine-containing gas, it is not limited to this, for example, 811P4.00!4'l
'*,c ctIF,,SOW,,8elFg,cy4
, m, y, F, li, etc. can also be used.

（実施例） 以下、本発明の方法の実施例について述べる。(Example) Examples of the method of the present invention will be described below.

実施例１ 直径５ｆａの中心孔を有し、外径１１　Ｑ＋ｗの多孔質
母材をａｒｃｔ４を原料として第３図に示す方法にて作
製した。内層多孔質母材の厚さは約１露、かさ密度は１
．５　ｆ　／　ａｍ　”であった。また外層多孔質母材
すかさ密度は約０．５　？　／　５１　”であった。Example 1 A porous base material having a central hole with a diameter of 5 fa and an outer diameter of 11 Q+w was produced using arct4 as a raw material by the method shown in FIG. 3. The thickness of the inner porous matrix is approximately 1 dew, and the bulk density is 1
．． 5 f/am''. The bulk density of the outer porous matrix was approximately 0.5?/51''.

該多孔質母材の下端を閉じ、温度１２００℃の加熱炉の
中へ入れ、炉内雰囲気ガスとして、マツフル内にＳｉＦ
４、Ｈｅ５ｃ４の混合ガスを５ｔ／−１また引上げ用種
棒よ’）　Ｃｋ、”の混合ガスをｌ０ＣＣ／−で流しな
がら、２　ｔｍ　／　ｍ　（Ｄ速度で多孔質母材を加熱
炉内に挿入した。The lower end of the porous base material was closed and placed in a heating furnace at a temperature of 1200°C, and SiF was added to the Matsufuru as the furnace atmosphere gas.
4. Flow the mixed gas of 5t/-1 of He5c4 at 5t/-1 and the pulling seed rod')Ck," at 10cc/-, and put the porous base material into the heating furnace at a speed of Inserted.

次いで多孔質母材を引き上げて、炉温を１６３０℃にし
、マツフル内雰囲気としてＨｅ　　を５ｔ／−流し、か
つ引上げ用種棒よシ真空に引いて、多孔質母材を２露／
−の速度で加熱炉内に挿入し、全体を透明化した。得ら
れた母材の外径は約４０■であった。Next, the porous base material was pulled up, the furnace temperature was set to 1630°C, 5 tons of He was flowed as an atmosphere inside the Matsufuru, and the pulling seed rod was evacuated, and the porous base material was heated to 2 dew/min.
The sample was inserted into the heating furnace at a speed of -, and the entire sample was made transparent. The outer diameter of the obtained base material was about 40 mm.

該母材に石英管をかぶせて縮径線引し、活性領域外径約
１０ｐｍ、外径１２５μｍのファイバを得た。得られた
ファイバの屈折率差は１３チ、減衰量は１．３μｍの波
長において、１８ｄＢ／ｋｍであった。The base material was covered with a quartz tube and drawn to reduce its diameter to obtain a fiber with an active region outer diameter of about 10 pm and an outer diameter of 125 μm. The refractive index difference of the obtained fiber was 13 degrees, and the attenuation was 18 dB/km at a wavelength of 1.3 μm.

実施例２ 直径５ｍの中心孔を有し、外径的１１０■の多孔質母材
をｅｔｃ４を原料として第５図に示す方法で作製した。Example 2 A porous base material having a central hole with a diameter of 5 m and an outer diameter of 110 cm was prepared using etc4 as a raw material by the method shown in FIG. 5.

内層多孔質母材の厚さは約１雪、かさ密度は１．５ｔ／
ｅｘ”、また外層多孔質母材のかさ密度は約αＳｔ／ａ
ｍ”であった。The thickness of the inner porous base material is approximately 1 snow, and the bulk density is 1.5t/
ex”, and the bulk density of the outer porous base material is approximately αSt/a
It was "m".

該多孔質母材を温度１２５０℃の加熱炉の中へ入れ、炉
内雰囲気ガスとしてＨｅ１Ｃ１４の混合ガスを５ｔ／−
また先端開口した多孔質母材に引上げ用種棒よシＨｅ１
Ｃ１４の混合ガスを２０ＣＣ／−で流しながら３　ｗｍ
　／―の速度で多孔質母材を加熱炉内に挿入した。The porous base material was placed in a heating furnace at a temperature of 1250°C, and a mixed gas of He1C14 was added at 5t/- as the furnace atmosphere gas.
In addition, a pulling seed rod was inserted into the porous base material with an open end.
3wm while flowing C14 mixed gas at 20CC/-
The porous base material was inserted into the heating furnace at a speed of /-.

次に全体の雰囲気を流量５ｔ７−〇Ｈｅ　　のみとし、
多孔質母材をマツフル上部に引き上げ、炉内温度を１６
５０℃にし、多孔質母材の開口端を閉じるためしばらく
その状態に留めたのち、２−／―の速度にて炉内に挿入
し、全体を透明化した。得られた母材の外径は約４０■
であった。Next, the entire atmosphere is set to a flow rate of 5t7-〇He,
The porous base material was lifted to the top of Matsufuru, and the temperature inside the furnace was raised to 16
The temperature was raised to 50°C, and the porous base material was kept in that state for a while to close the open end, and then inserted into the furnace at a speed of 2-/- to make the whole transparent. The outer diameter of the obtained base material is approximately 40cm
Met.

該母材に石英管をかぶせて縮径線引し、活性領域外径的
１０ＰＷ＠、外径１２５μ惰のファイバを得た。得られ
たファイバの屈折率差はＩＩＬ３ｔｓ１また減衰量は１
．５μｍの波長においてＱ、　５　ａＢ／ｉであった。The base material was covered with a quartz tube and drawn to reduce its diameter to obtain a fiber with an active region outer diameter of 10PW and an outer diameter of 125μ. The refractive index difference of the obtained fiber is IIL3ts1 and the attenuation is 1
．． At a wavelength of 5 μm, the Q was 5 aB/i.

以上の実施例の結果から明らかなごとく、得られたファ
イバは石英に弗素が適切に添加され伝送損失が極めて小
さく、残留ＯＨ基量も少ないことがわかる。As is clear from the results of the above examples, it can be seen that in the obtained fiber, fluorine is appropriately added to the quartz, the transmission loss is extremely small, and the amount of residual OH groups is also small.

〔発明の効果〕〔Effect of the invention〕

本発明の光ファイバ用母材の製造方法は、中心孔を有し
、半径方向にがさ密度分布を有する多孔質母材を用いる
ことにより、下記の利点を有する。The method for manufacturing an optical fiber preform of the present invention has the following advantages by using a porous preform having a central hole and having a radial density distribution.

■　高かさ密度部分が直接脱水用ガスにさらされるため
、中心孔のない母材では脱水困難であった、該高かさ密
度部分の脱水が効果的に行われる。(2) Since the high bulk density portion is directly exposed to the dehydration gas, the high bulk density portion can be effectively dehydrated, which would be difficult to dehydrate in a base material without a central hole.

■　多孔質母材への弗素添加量の温度依存性及びかさ密
度依存性という性質を巧みに利用することにより、弗素
添加が効率良く行え、理想的な低損失光ファイバ用母材
が得られる。(2) By skillfully utilizing the temperature dependence and bulk density dependence of the amount of fluorine added to the porous base material, fluorine addition can be carried out efficiently and an ideal low-loss optical fiber base material can be obtained.

■　従来法による中心孔を有する多孔質母材の製法では
出発棒の引き抜きが困難で長尺母材を得難かったが、本
発明は多孔質母材成長と同時に糧棒が順次抜かれてゆく
ため、上記の困難はなく、長手方向に均一な寸法及びか
さ密度分布を有する長尺の母材を得ることができる。■ In the conventional manufacturing method of porous base material with a central hole, it was difficult to pull out the starting rod and it was difficult to obtain a long base material, but in the present invention, the food rods are sequentially pulled out at the same time as the porous base material grows. , it is possible to obtain a long base material having uniform dimensions and bulk density distribution in the longitudinal direction without the above-mentioned difficulties.

以上のように、本発明は低損失で長手方向に均一な長尺
の光ファイバ用母材を容易に得ることが可能である。As described above, according to the present invention, it is possible to easily obtain a long optical fiber preform with low loss and uniformity in the longitudinal direction.

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

第１図は石英への弗素の添加率と温度条件との関係を示
すグラフ、第２図は石英微粉末への゛　弗素添加率と該
石英微粉末のかさ密度との関係を示すグラフ、第３図な
いし第５図は本発明の実施態様例を説明４であって、第
３図は多孔質母材の形成方法、第４図は該多孔質母材の
脱水および弗素添加の方法、第５図は多孔質母材を焼結
、透明ガラス化する方法を示す。Figure 1 is a graph showing the relationship between the fluorine addition rate to quartz and temperature conditions; Figure 2 is a graph showing the relationship between the fluorine addition rate to quartz fine powder and the bulk density of the quartz fine powder; 3 to 5 illustrate embodiments of the present invention. FIG. 3 shows a method for forming a porous base material, FIG. 4 shows a method for dehydrating and adding fluorine to the porous base material, and FIG. Figure 5 shows a method of sintering a porous base material and turning it into transparent glass.

Claims (7)

【特許請求の範囲】[Claims] （１）中心孔を有し、半径方向にかさ密度分布を有する
多孔質母材を、弗素又は弗素を含む雰囲気中にさらして
加熱することにより、半径方向に屈折率分布を有する透
明ガラス母材を得ることを特徴とする光ファイバ用母材
の製造方法。(1) A transparent glass base material having a refractive index distribution in the radial direction by exposing a porous base material having a central hole and having a bulk density distribution in the radial direction to fluorine or an atmosphere containing fluorine and heating it. 1. A method for producing an optical fiber base material, the method comprising: obtaining a base material for an optical fiber; （２）長手方向に対向して、互の一端が隣り合うように
配置された２本の種棒の隣接する付近より多孔質母材を
形成し、該多孔質母材の種棒長手方向成長とともに少く
とも一方の種棒を該長手方向に移動せしめることにより
形成される、中心孔を有し、半径方向にかさ密度分布を
有する多孔質母材を、弗素又は弗素を含む雰囲気中にさ
らして加熱することにより、半径方向に屈折率分布を有
する透明ガラス母材を得ることを特徴とする光ファイバ
用母材の製造方法。(2) A porous base material is formed from the adjacent vicinity of two seed rods arranged so that one end of the other is adjacent to each other while facing each other in the longitudinal direction, and the seed rods of the porous base material grow in the longitudinal direction. A porous base material having a central hole and having a bulk density distribution in the radial direction, which is formed by moving at least one seed rod in the longitudinal direction, is exposed to fluorine or an atmosphere containing fluorine. 1. A method for producing an optical fiber preform, the method comprising obtaining a transparent glass preform having a refractive index distribution in the radial direction by heating. （３）多孔質母材が実質的に石英微粉末からなる特許請
求の範囲第（１）項または第（２）項に記載の光ファイ
バ用母材の製造方法。(3) A method for manufacturing an optical fiber preform according to claim (1) or (2), wherein the porous preform is substantially composed of fine quartz powder. （４）かさ密度分布は中心孔をとりまく部分のかさ密度
がその他の部分よりも大きくなつている特許請求の範囲
第（１）項、第（２）項または第（３）項記載の光ファ
イバ用母材の製造方法。(4) The optical fiber according to claim (1), (2), or (3), wherein the bulk density distribution is such that the bulk density of the portion surrounding the central hole is larger than that of the other portions. Manufacturing method of base material. （５）多孔質母材の中心孔には非弗素系脱水ガスを含む
ガスを流し、多孔質母材外周は弗素又は弗素を含む高温
雰囲気中にさらす特許請求の範囲第（１）項、第（２）
項、第（３）項または第（４）項記載の光ファイバ用母
材の製造方法。(5) A gas containing a non-fluorine dehydrating gas is passed through the center hole of the porous base material, and the outer periphery of the porous base material is exposed to fluorine or a high temperature atmosphere containing fluorine. (2)
3. The method for manufacturing an optical fiber preform according to item 1, item 3, or item 4. （６）非弗素系脱水ガスが塩素又は塩素を含む化合物ガ
スである特許請求の範囲第（５）項記載の光ファイバ用
母材の製法。(6) The method for producing an optical fiber preform according to claim (5), wherein the non-fluorine dehydrating gas is chlorine or a compound gas containing chlorine. （７）弗素を含む高温雰囲気がＳｉＦ＿４、ＣＣｌ＿２
Ｆ＿２、ＣＣｌＦ＿３、ＳｉＦ＿２、ＳＦ＿６、ＳｅＦ
＿６、ＣＦ＿４、Ｎ＿３Ｆ、Ｆ＿２Ｎ＿４のうちの少な
くとも一つを含有する特許請求の範囲第（５）項記載の
光ファイバ用母材の製造方法。(7) High temperature atmosphere containing fluorine is SiF_4, CCl_2
F_2, CClF_3, SiF_2, SF_6, SeF
_6, CF_4, N_3F, and F_2N_4. The method for manufacturing an optical fiber preform according to claim (5).
JP1265285A 1985-01-28 1985-01-28 Production of base material for optical fiber Granted JPS61174138A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP1265285A JPS61174138A (en) 1985-01-28 1985-01-28 Production of base material for optical fiber

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1265285A JPS61174138A (en) 1985-01-28 1985-01-28 Production of base material for optical fiber

Publications (2)

Publication Number Publication Date
JPS61174138A true JPS61174138A (en) 1986-08-05
JPH0583498B2 JPH0583498B2 (en) 1993-11-26

Family

ID=11811299

Family Applications (1)

Application Number Title Priority Date Filing Date
JP1265285A Granted JPS61174138A (en) 1985-01-28 1985-01-28 Production of base material for optical fiber

Country Status (1)

Country Link
JP (1) JPS61174138A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0311080A2 (en) * 1987-10-07 1989-04-12 Sumitomo Electric Industries Limited Method for producing glass preform for optical fiber
US5022904A (en) * 1985-12-27 1991-06-11 Sumitomo Electric Industries, Ltd. Method of making optical glass article
US5217516A (en) * 1985-12-27 1993-06-08 Sumitomo Electric Industries, Ltd. Method of making optical glass article
WO2015107931A1 (en) * 2014-01-16 2015-07-23 古河電気工業株式会社 Method for producing optical fiber preform and method for producing optical fiber

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5022904A (en) * 1985-12-27 1991-06-11 Sumitomo Electric Industries, Ltd. Method of making optical glass article
US5217516A (en) * 1985-12-27 1993-06-08 Sumitomo Electric Industries, Ltd. Method of making optical glass article
EP0311080A2 (en) * 1987-10-07 1989-04-12 Sumitomo Electric Industries Limited Method for producing glass preform for optical fiber
US5055121A (en) * 1987-10-07 1991-10-08 Sumitomo Electric Industries, Ltd. Method for producing glass preform for optical fiber
WO2015107931A1 (en) * 2014-01-16 2015-07-23 古河電気工業株式会社 Method for producing optical fiber preform and method for producing optical fiber

Also Published As

Publication number Publication date
JPH0583498B2 (en) 1993-11-26

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