JP3071235B2 - Method of manufacturing preform for single mode optical fiber - Google Patents
Method of manufacturing preform for single mode optical fiberInfo
- Publication number
- JP3071235B2 JP3071235B2 JP8309991A JP8309991A JP3071235B2 JP 3071235 B2 JP3071235 B2 JP 3071235B2 JP 8309991 A JP8309991 A JP 8309991A JP 8309991 A JP8309991 A JP 8309991A JP 3071235 B2 JP3071235 B2 JP 3071235B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- optical fiber
- preform
- base material
- glass
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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]
- C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
- C03B37/0146—Furnaces therefor, e.g. muffle tubes, furnace linings
Description
【０００１】[0001]
【産業上の利用分野】本発明はシングルモ−ド光ファイ
バ用母材の製造方法、特にはロット間において長手方向
に安定した比屈折率差（△n)を有するシングルモ−ド光
ファイバ製造用のガラス母材の製造方法に関するもので
ある。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a single mode optical fiber preform, and more particularly to a method for manufacturing a single mode optical fiber having a stable relative refractive index difference (.DELTA.n) in the longitudinal direction between lots. The present invention relates to a method for manufacturing a glass base material.
【０００２】[0002]
【従来の技術】シングルモ−ド光ファイバ用母材の製造
は四塩化けい素などの気体状ガラス原料と四塩化ゲルマ
ニウムなどのド−プ剤とを酸水素火炎バ−ナ−に導入
し、ついでこの火炎加水分解で発生したガラス微粒子を
担体上に堆積し、これを軸方向に成長させて多孔質ガラ
ス母材を作る、いわゆるVAD 法で製造し、ついでこれを
高温で脱水、焼結して透明ガラス化することによって製
造されている。2. Description of the Related Art A single-mode optical fiber preform is manufactured by introducing a gaseous glass material such as silicon tetrachloride and a doping agent such as germanium tetrachloride into an oxyhydrogen flame burner. The glass fine particles generated by this flame hydrolysis are deposited on a carrier, grown in the axial direction to produce a porous glass base material, which is manufactured by the so-called VAD method, and then dehydrated and sintered at a high temperature. It is manufactured by vitrification.
【０００３】[0003]
【発明が解決しようとする課題】しかして、このVAD 法
で製造されたシングルモ−ド光ファイバ用母材には引上
げ速度の変動のために比屈折率差（△n)がロット間で大
きくバラ付くという不利がある。これはガラス微粒子の
堆積、成長で一定直径の多孔質ガラス母材が得られるよ
うに成長しつつある多孔質ガラス母材は徐々に上方に引
上げられるのであるが、多くの場合、多孔質ガラス母材
の製造初期や後期では引上げ速度が外径が一定になった
ときの引上げる速度に比較して変化し易く、またその他
の要因で作業中に引上げ速度が変化することもある。However, the single-mode optical fiber preform manufactured by the VAD method has a large relative refractive index difference (Δn) between lots due to fluctuations in the pulling speed. There is a disadvantage of sticking. This is because the growing porous glass preform is gradually pulled upward so that a porous glass preform having a constant diameter can be obtained by deposition and growth of glass fine particles. In the early and late stages of material production, the pulling speed is more likely to change than the pulling speed when the outer diameter is constant, and the pulling speed may change during the work due to other factors.
【０００４】このように引上げ速度が変化するとこれを
脱水、焼結して得られるガラス母材の比屈折率差（△n)
が変化し、このために比屈折率差（△n)の安定したガラ
ス母材を得ることが難しく、一本のガラス母材から目的
とする屈折率分布をもつ部分の割合が60％以下にもなる
という欠点がある。[0004] When the pulling speed changes in this way, the relative refractive index difference (△ n) of the glass base material obtained by dehydrating and sintering it.
Changes, it is difficult to obtain a glass base material having a stable relative refractive index difference (△ n), and the ratio of a portion having a target refractive index distribution from one glass base material to 60% or less. Disadvantage.
【０００５】そのため、この引上げ速度の安定化につい
ては大気圧による原料ガス供給量の変動を補正する方法
が提案されており、本発明者らもクラッド用バ−ナ−に
供給する水素量を制御する方法を提案している（特願平
２−38039号明細書参照）が、多孔質ガラス母材の引上
げ速度を一定にしても石英ガラス製の炉芯管を用いて脱
水、焼結した場合には各ロット毎に比屈折率差（△n)が
異なる値となるために、比屈折率差（△n)がロット間で
均一である光ファイバ用母材を得ることが難しいという
問題がある。To stabilize the pulling speed, a method has been proposed to correct the fluctuation of the supply amount of the raw material gas due to the atmospheric pressure. The present inventors also control the amount of hydrogen supplied to the cladding burner. (See Japanese Patent Application No. 2-38039), but dewatering and sintering using a quartz glass furnace core tube even if the pulling speed of the porous glass base material is kept constant. The problem is that it is difficult to obtain an optical fiber preform in which the relative refractive index difference (Δn) is uniform among lots because the relative refractive index difference (Δn) is different for each lot. is there.
【０００６】[0006]
【課題を解決するための手段】本発明はこのような不利
を解決したシングルモ−ド光ファイバ用母材の製造方法
に関するもので、これはゲルマニウムド−プしたガラス
微粒子をタ−ゲット基材に堆積し、これを軸方向に引上
げて多孔質ガラス母材を作り、これを石英ガラス製炉芯
管を用いて高温で脱水、焼結してなる光ファイバ用母材
の製造方法において、多孔質ガラス母材の脱水処理工程
における該石英ガラス製炉芯管の加熱ヒ−タ−の温度を
該石英ガラス製炉芯管の使用回数に応じて制御して加熱
ゾ−ンの温度を一定に保つことを特徴とするものであ
る。また、炉内温度を一定に保つには、加熱ヒーターに
供給する電力を増加させればよい。 SUMMARY OF THE INVENTION The present invention relates to a method of manufacturing a preform for a single-mode optical fiber which has solved the above disadvantages. This method uses a germanium-doped glass fine particle as a target substrate. In a method for producing a preform for an optical fiber, a porous glass preform is formed by depositing and pulling it up in the axial direction to produce a porous glass preform, and dehydrating and sintering this at a high temperature using a quartz glass furnace core. The temperature of the heating heater of the quartz glass furnace core in the dehydration process of the glass base material is controlled in accordance with the number of times the quartz glass furnace core is used, thereby keeping the temperature of the heating zone constant. It is characterized by the following. To keep the furnace temperature constant, use a heater
The supplied power may be increased.
【０００７】すなわち、本発明者らはロット間での比屈
折率差（△n)が一定であるシングルモ−ド光ファイバ用
母材の製造方法について種々検討した結果、VAD 法で作
られたゲルマニウムド−プされた多孔質ガラス母材の屈
折率が脱水、焼結工程における脱水処理温度に依存し、
この脱水処理温度の下降と共に上昇するということ、ま
たこの脱水、焼結工程を行なう石英ガラス製炉芯管につ
いてはその加熱ゾ−ンの温度が使用回数の増加と共に低
下することを見出し、この加熱ゾ−ンの温度を一定にす
るためにはこの石英ガラス製炉芯管の加熱ヒ−タ−の温
度をこの炉芯管の使用回数に応じて制御すればよいとい
うことを確認して本発明を完成させた。以下にこれをさ
らに詳述する。Namely, the present inventors is the relative refractive index difference between lots (△ n) is constant Shingurumo - a result of various studies on a manufacturing method of the mode optical fiber preform, created by the VAD method <br / The refractive index of the obtained germanium-doped porous glass base material depends on the dehydration temperature in the dehydration and sintering steps,
It has been found that the temperature rises as the temperature of the dehydration treatment decreases, and that the temperature of the heating zone of the quartz glass core tube for performing the dehydration and sintering steps decreases as the number of uses increases. It has been confirmed that the temperature of the heating heater of the quartz glass furnace core tube should be controlled in accordance with the number of times the furnace core tube is used in order to keep the zone temperature constant. Was completed. This is described in more detail below.
【０００８】[0008]
【作用】本発明は比屈折率差（△n)がロット間で均一と
されたシングルモ−ド光ファイバ−用母材の製造方法に
関するものである。The present invention relates to a method for producing a single-mode optical fiber preform in which the relative refractive index difference (Δn) is made uniform among lots.
【０００９】本発明による光ファイバ−用母材の製造は
基本的には公知のVAD 法で行なわれる。したがって、こ
れは一本のコア用酸水素火炎バ−ナ−と複数個のクラッ
ド用酸水素火炎バ−ナ−を用いて、このコア用酸水素火
炎バ−ナ−に四塩化けい素とド−プ剤としての四塩化ゲ
ルマニウムからなる原料ガスと酸素ガス、水素ガスを導
入し、四塩化けい素と四塩化ゲルマニウムの火炎加水分
解で発生した酸化ゲルマニウムでド−プされたシリカガ
ラス微粒子をタ−ゲット基材上に堆積させて軸方向にコ
ア部を成長させ、クラッド用酸水素火炎バ−ナ−に四塩
化けい素、酸素ガス、水素ガスを供給して四塩化けい素
の火炎加水分解で発生したシリカガラス微粒子をこのコ
ア部上に堆積成長させクラッド部を形成させて多孔質ガ
ラス母材を作り、ついてこれを石英ガラス製炉芯管を用
いて脱水、焼結させればよい。The production of the optical fiber preform according to the present invention is basically performed by a known VAD method. Therefore, this uses a single core oxyhydrogen flame burner and a plurality of cladding oxyhydrogen flame burners, and this core oxyhydrogen flame burner uses silicon tetrachloride and silicon dioxide. -A raw material gas consisting of germanium tetrachloride as a dopant, an oxygen gas, and a hydrogen gas are introduced, and silica glass fine particles doped with germanium oxide generated by flame hydrolysis of silicon tetrachloride and germanium tetrachloride are removed. -The core is grown on the get base material to grow the core in the axial direction, and silicon tetrachloride, oxygen gas and hydrogen gas are supplied to the oxyhydrogen flame burner for cladding for flame hydrolysis of silicon tetrachloride. The silica glass fine particles generated in the above are deposited and grown on the core portion to form a clad portion, thereby producing a porous glass base material, which is then dehydrated and sintered using a quartz glass furnace core tube.
【００１０】しかし、この場合多孔質ガラス母材の脱
水、焼結によって得られる光ファイバ用母材の比屈折率
差（△n)とロット間との相関についてしらべたところ、
この多孔質ガラス母材の脱水、処理工程は従来一般に C
l2、 F2などのハロゲンガスの存在下で行なわれるのであ
るが、これを例えば Cl2ガスの存在下で行なうとド−プ
剤としての酸化ゲルマニウム(GeO2)が Cl2と反応して揮
発性の GeCl4となって揮発するので比屈折率差（△n)が
低下するようになるのであるが、この反応がこの反応温
度に依存するものであるためにこの加熱ゾ−ンの温度が
低下すると GeCl4の発生が抑えられて母材中の結晶性Ge
O2が徐々に増加し、比屈折率差（△n)が上昇するので、
この比屈折率差（△n)を均一にするためには脱水処理工
程において加熱ゾ−ンの温度を一定にすればよいという
ことが見出された。However, in this case, the correlation between the relative refractive index difference (Δn) of the optical fiber preform obtained by dehydration and sintering of the porous glass preform and the lot-to-lot correlation was determined.
The dehydration and treatment process of this porous glass base material is generally C
This is performed in the presence of a halogen gas such as l 2 or F 2 .If this is performed in the presence of, for example, Cl 2 gas, germanium oxide (GeO 2 ) as a doping agent reacts with Cl 2. The vaporization of volatile GeCl 4 results in a decrease in the relative refractive index difference (Δn). However, since this reaction depends on the reaction temperature, the temperature of the heating zone is reduced. When the concentration decreases, the generation of GeCl 4 is suppressed and the crystalline Ge
Since O 2 gradually increases and the relative refractive index difference (△ n) increases,
It has been found that in order to make the relative refractive index difference (Δn) uniform, the temperature of the heating zone should be kept constant in the dehydration treatment step.
【００１１】他方、この多孔質ガラス母材の脱水処理工
程は石英ガラス製炉芯管を用いて行なわれるのである
が、この石英ガラス製炉芯管についてはこれを使用して
いると石英ガラスの失透が徐々に進み、この失透が進む
にしたがってこれに比例して輻射熱の放射量が徐々に落
ち、加熱ゾ−ンの温度が徐々に低下するために、炉芯管
に供給する電力を一定にして多孔質ガラス母材を複数個
脱水処理し焼結すると、このようにして得られた光ファ
イバ用母材の比屈折率差（△n)は加熱ゾ−ンの温度が徐
々に低下するために各ロット間では図２に示したように
ロット毎に徐々に上昇し、一定にならないということが
見出された。On the other hand, the step of dehydrating the porous glass base material is performed by using a quartz glass furnace core tube. As the devitrification progresses gradually, and as the devitrification progresses, the amount of radiant heat radiated gradually decreases, and the temperature of the heating zone gradually decreases. When a plurality of porous glass preforms are dehydrated and sintered at a constant temperature, the relative refractive index difference (△ n) of the thus obtained optical fiber preform gradually decreases as the temperature of the heating zone decreases. As shown in FIG. 2, it was found that the temperature gradually increased for each lot and did not become constant.
【００１２】したがって、各ロット間における光ファイ
バ用母材の比屈折率差（△n)を均一にするためには加熱
ゾ−ンの温度を一定にする必要があるが、これには石英
ガラス製炉芯管での石英ガラスの失透による輻射熱の放
射量の減少があるので、これについてはこの失透化度に
比例して徐々に加熱ヒ−タ−に供給する電力を例えば炉
内温度を1,100 ℃と一定にするときには図３に示したよ
うにロット数の増加と共に徐々に上昇させれば、これを
所定の一定温度に保つことができ、得られる光ファイバ
用母材の比屈折率差（△n)をロット間で均一にすること
ができることが確認されたので、この加熱ゾ−ンの温度
を一定にするためにはここに使用する石英ガラス製炉芯
管の使用回数に応じて加熱ヒ−タ−の温度を制御するこ
と、換言すれば加熱ヒ−タ−に供給する電力を石英ガラ
ス製炉芯管の使用回数に応じて徐々に増加させればよ
い。Therefore, in order to make the relative refractive index difference (Δn) of the optical fiber preform between lots uniform, it is necessary to keep the temperature of the heating zone constant. Since there is a decrease in the amount of radiation of radiant heat due to the devitrification of quartz glass in the furnace core tube, the electric power supplied to the heating heater is gradually increased in proportion to the degree of devitrification, for example, by changing the furnace temperature. When the temperature is kept constant at 1,100 ° C., as shown in FIG. 3, if the temperature is gradually increased with an increase in the number of lots, the temperature can be maintained at a predetermined constant temperature, and the relative refractive index of the obtained optical fiber base material can be maintained. Since it was confirmed that the difference (△ n) can be made uniform among lots, the temperature of the heating zone should be kept constant according to the number of times the quartz glass core tube used here was used. To control the temperature of the heating heater, in other words, the heating heater. - data - the test sheet to quartz glass power
What is necessary is just to increase it gradually according to the frequency of use of the furnace core tube.
【００１３】なお、本発明により光ファイバ用母材を得
るために多孔質ガラス母材を脱水処理するための加熱ゾ
−ンの温度を80０〜1,400 ℃の範囲で一定温度に保持す
ればロット間での比屈折率差（△n)の変動を少なくする
ことができる。If the temperature of the heating zone for dehydrating the porous glass preform in order to obtain the preform for an optical fiber according to the present invention is maintained at a constant temperature in the range of 800 to 1,400 ° C., the lot-to-lot quantity is reduced. The variation of the relative refractive index difference (Δn) can be reduced.
【００１４】[0014]
【実施例】つぎに本発明の実施例、比較例を示す。 実施例、比較例 コア用バ−ナ−に四塩化けい素30cc／分、四塩化ゲルマ
ニウム 3.5cc／分、酸素ガス3.0 リットル／分、水素ガ
ス1.0 リットル／分を供給すると共に、クラッド用バ−
ナ−に四塩化けい素 400cc／分、酸素ガス10リットル／
分、水素ガス8リットル／分を供給し、この火炎加水分
解で発生した酸化ゲルマニウムでド−プされたコア用ガ
ラス微粒子および酸化ゲルマニウムを含まないクラッド
用ガラス微粒子を基材の先に設置した20rpm で回転して
いる合成石英ガラス棒に堆積し、その軸方向に成長させ
てコア部、クラッド部からなる多孔質ガラス母材を作
り、軸方向にこの多孔質ガラス母材を引上げ装置を用い
て0.65±0.005mm/分の一定速度で引上げて、外径 100m
m、長さ800mm の多孔質ガラス母材を作った。Next, examples of the present invention and comparative examples will be described. Examples and Comparative Examples 30 cc / min of silicon tetrachloride, 3.5 cc / min of germanium tetrachloride, 3.0 liter / min of oxygen gas and 1.0 liter / min of hydrogen gas were supplied to the core burner, and the cladding bar was supplied.
400cc / min of silicon tetrachloride in oxygen, 10 liters of oxygen gas /
And a hydrogen gas of 8 liters / minute, and a core glass fine particle doped with germanium oxide generated by the flame hydrolysis and a cladding glass fine particle containing no germanium oxide were set at a speed of 20 rpm. It is deposited on a synthetic quartz glass rod that is rotating in the direction, and grown in the axial direction to make a porous glass base material composed of a core part and a clad part, and this porous glass base material is drawn in the axial direction using a pulling device. Pull up at a constant speed of 0.65 ± 0.005mm / min, outer diameter 100m
An 800 mm long porous glass preform was made.
【００１５】ついで、これを Cl2ガスを10容量％含有す
るHeガス雰囲気中において長さ2,000 mmの石英ガラス製
炉管を用い、この加熱ヒ−タ−に供給する電力をロット
毎に図３に示したように徐々に上昇させて加熱ゾ−ンの
温度を1,100 ℃±1 ℃に保つようにして脱水処理し、1,
600 ℃で焼結して外径40mm、長さ400mm のシングルモ−
ド光ファイバ用母材を作り、このもののロット毎に比屈
折率差（△n)をしらべたところ、図１に示したように略
々均一であることが確認された。Next, in a He gas atmosphere containing 10% by volume of Cl 2 gas, a quartz glass furnace tube having a length of 2,000 mm was used, and the electric power supplied to the heating heater was changed for each lot as shown in FIG. As shown in (1), the temperature was gradually raised to keep the temperature of the heating zone at 1,100 ° C. ± 1 ° C.
Sintered at 600 ° C, single mode with 40mm outer diameter and 400mm length
A preform for optical fiber was prepared, and the relative refractive index difference (Δn) was examined for each lot. As a result, it was confirmed that the preform was substantially uniform as shown in FIG.
【００１６】しかし、比較のために上記における加熱ヒ
−タ−に供給される電力を各ロットごとに変えずに一定
にしたところ、この場合にはロット数の増加と共に光フ
ァイバ用母材の屈折率分布が増加し、両者の関係は図２
に示したとおりのものとなった。However, for comparison, when the power supplied to the heating heater in the above was kept constant without changing for each lot, in this case, as the number of lots increased, the refractive index of the optical fiber preform was changed. The rate distribution increases, and the relationship between the two is shown in FIG.
The result was as shown in the figure.
【００１７】[0017]
【発明の効果】本発明は上記構成としたことにより、石
英ガラス製炉芯管の使用回数の増加に伴う石英ガラスの
失透により、輻射熱の放射量が減少し炉内温度が低下す
るのを、加熱ヒーターへの電力を増加させて補償し、加
熱ゾーンの温度を一定に制御し、多孔質ガラス母材の脱
水、焼結の際のＧｅＣｌ 4 の揮発量を一定とすることに
より、製造ロット間で比屈折率差(Δｎ)の変動のない光
ファイバ用母材の製造が可能となり、特性の安定したシ
ングルモード光ファイバが得られる。ばロット間での比
屈折率差（△n)の変動を少なくすることができる。According to the present invention having the above-described structure, the stone
With the increase in the number of uses of English glass furnace core tubes, quartz glass
Due to devitrification, the amount of radiant heat radiation decreases and the furnace temperature decreases.
Is compensated by increasing the power to the heater,
The temperature of the heat zone is controlled to a constant value to remove the porous glass base material.
To keep the volatilization amount of GeCl 4 during water and sintering constant
Light with no variation in relative refractive index difference (Δn) between production lots
It is possible to manufacture fiber preforms,
A single mode optical fiber is obtained. For example, the variation in the relative refractive index difference (Δn) between lots can be reduced.
【図１】 本発明により得られたシングルモ−ド光ファ
イバ−用母材のロット数と屈折率（△n)との相関グラフ
である。FIG. 1 is a graph showing the correlation between the lot number and the refractive index (Δn) of a single-mode optical fiber preform obtained according to the present invention.
【図２】 比較例で作られたシングルモ−ド光ファイバ
−用母材のロット数と比屈折率差（△n)との相関グラフ
である。FIG. 2 is a graph showing the correlation between the number of lots of a single-mode optical fiber preform prepared in a comparative example and the relative refractive index difference (Δn).
【図３】 ロット数と石英ガラス製炉芯管に供給するヒ
−タ−電力(kw)との相関グラフである。FIG. 3 is a correlation graph between the number of lots and heater power (kw) supplied to a quartz glass furnace core tube.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 栗山 収 群馬県安中市磯部２丁目13番１号 信越 化学工業株式会社 磯部工場内 (58)調査した分野(Int.Cl.7，ＤＢ名) C03B 37/00 - 37/16 C03B 8/04 C03B 20/00 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Osamu Kuriyama 2-3-1-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Isobe Plant (58) Field surveyed (Int.Cl. 7 , DB name) C03B 37/00-37/16 C03B 8/04 C03B 20/00
Claims (2)
タ−ゲット基材上に堆積し、これを軸方向に引上げて多
孔質ガラス母材を作り、これを石英ガラス製炉芯管を用
いて高温で脱水、焼結してなる光ファイバ用母材の製造
方法において、多孔質ガラス母材の脱水処理工程におけ
る該石英ガラス製炉芯管の加熱ヒ−タ−の温度を該石英
ガラス製炉芯管の使用回数に応じて制御して加熱ゾ−ン
の温度を一定に保つことを特徴とするシングルモ−ド光
ファイバ用母材の製造方法。1. A method for depositing germanium-doped glass fine particles on a target base material, and pulling the same in an axial direction to form a porous glass base material, which is then heated to a high temperature using a quartz glass furnace core tube. In the method for producing a preform for an optical fiber obtained by dehydration and sintering, the temperature of the heating heater of the quartz glass furnace core tube in the step of dehydrating the porous glass preform is set to the quartz glass furnace core. A method for producing a preform for a single-mode optical fiber, characterized in that the temperature of a heating zone is kept constant by controlling the number of uses of a tube.
じて制御して加熱ゾ−ンの温度を一定に保つに際し、石To keep the temperature of the heating zone constant by controlling
英ガラス製炉芯管の使用回数の増加に伴って低下する炉Furnace declines with increasing use of British glass core tube
内温度を、加熱ヒーターに供給される電力を増加させてIncrease the internal temperature by increasing the power supplied to the heater
補償する請求項１に記載のシングルモ−ド光ファイバ用2. A single-mode optical fiber according to claim 1, which compensates.
母材の製造方法。Manufacturing method of base material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8309991A JP3071235B2 (en) | 1991-03-22 | 1991-03-22 | Method of manufacturing preform for single mode optical fiber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8309991A JP3071235B2 (en) | 1991-03-22 | 1991-03-22 | Method of manufacturing preform for single mode optical fiber |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04295026A JPH04295026A (en) | 1992-10-20 |
| JP3071235B2 true JP3071235B2 (en) | 2000-07-31 |
Family
ID=13792744
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8309991A Expired - Lifetime JP3071235B2 (en) | 1991-03-22 | 1991-03-22 | Method of manufacturing preform for single mode optical fiber |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3071235B2 (en) |
-
1991
- 1991-03-22 JP JP8309991A patent/JP3071235B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04295026A (en) | 1992-10-20 |
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