JP2004107190A

JP2004107190A - Method of manufacturing optical fiber and manufacturing apparatus

Info

Publication number: JP2004107190A
Application number: JP2002276263A
Authority: JP
Inventors: Hisashi Koaizawa; 小相澤　久; Yoshihiro Inoue; 井上　善博; Tetsuya Kumada; 熊田　哲哉
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 2002-09-20
Filing date: 2002-09-20
Publication date: 2004-04-08
Anticipated expiration: 2022-09-20
Also published as: JP4398634B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of stably manufacturing an optical fiber with good properties. <P>SOLUTION: In manufacturing an optical fiber by melting an optical fiber preform 5 in a drawing furnace 20, spinning an optical fiber 6, coating the optical fiber 6 to form a coated optical fiber 7, pulling out the coated optical fiber 7 by a capstan 50, and winding by a winding machine 60, a double spooler is used as the winding machine 60 and the optical fiber is sampled at a drawing speed for manufacturing after drawing for a certain period of time or a certain fiber length after reaching the manufacturing drawing speed. Properties of the sampled optical fiber are measured and respective drawing conditions are controlled repeatedly until the obtained measured values reach within a required range. After confirming that the required properties are obtained, drawing of the product optical fiber is started. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
光ファイバの線引方法および装置で特に特性の調整が難しい光ファイバを線引して光ファイバを製造する方法および装置に関する。又特に長手方向の光ファイバ母材の変動（たとえばコア径や屈折率分布の変動、複数のコア部からなる場合には、各コア部の屈折率やその分布さらに各層の厚さの変動が考えられる）がある母材に対応できる光ファイバ製造方法及び装置に関する。
【０００２】
【従来の技術】
光ファイバの線引では、線引速度（本明細書中、線速ともいう。）がほぼ一定線速とならないとカットオフや分散あるいはゼロ分散波長やモードフィールド径（ＭＦＤと略す）等の伝送特性が変化するために製品とならない。そのために、製造線速に到達してファイバ径や被覆径が安定するまで巻き取らずにエアガンで被覆ファイバを廃棄するか、あるいは巻き取りボビンにピンチロール手段を設けて、製造線速でサンプリングをして、その被覆光ファイバを検査して、所定の品質を有している事を確認後、巻き取り機に巻きつける事が開示されている（例えば、特許文献１〜２参照。）。この様にする事で、光ファイバのサンプリングを製造線速で行える事、さらに所定の品質を有していた場合にすぐに製造に入れるために生産性を向上できる利点がある。
また、所定波長における波長分散が正及び負となる区間が交互に設けられる光ファイバの製造方法において、線引開始時に得られた光ファイバの波長分散を測定し測定された波長分散に基づいて正及び負分散区間の目標ファイバ径を決定し線引を行う事が開示されている（例えば、特許文献３参照。）。これは分散スロープを低減したファイバや実効コア断面積が大きな光ファイバでは、屈折率分布が複雑で、屈折率の変化が大きく、プリフォームアナライザの測定精度が十分でないために特性の予測精度が出ないためにこの様なサンプリングを行う製造方法が提案されている。
また、屈折率分布が長手方向で均一な光ファイバ母材を線引する方法において、線引の開始時の際に得られた一定長さの光ファイバの波長分散及び分散スロープを測定し、測定された、波長分散と分散スロープに基づいて目標とする波長分散を得るための目標線引テンションと目標コア径を求め、この目標の線引テンションとコア径で母材の残りの部分を線引きする事が開示されている。また、更に最初のサンプルで目標のテンションを決め、次のサンプル取りで目標コア径を予測し、前記予測した目標テンションとコア径で残り母材を線引きする事が開示されている。また線引テンションを調整する方法として、線引速度を調整する事と線引炉の温度を調整する事が開示されている。これは母材の加工精度が分散補償ファイバ（ＤＣＦ）を作る上で不十分な場合や、及びプリフォームアナライザの測定精度が悪くても目標とする分散特性が容易に得られるためにこの様なサンプリングを行う製造方法が提案されている。特に線引テンションやコア径の変化に敏感なＤＣＦの製造に好適である事が記載されている（例えば、特許文献４参照。）。
【０００３】
しかしながら、従来は線引きされた光ファイバが所望の品質を有しているかを判定するだけであり、積極的に特性を合わせる内容は開示されていない。また、品質としてはコア径、ファイバ径や被覆の偏肉を対象としている（例えば、特許文献５〜６参照。）。
また、線引開始の際に得られた一定長さの光ファイバの波長分散を測定する事が開示されている（例えば、特許文献７〜８参照。）が、どのような条件でサンプリングされたか不明である。
特に線引速度が異なるとファイバの特性も変わるので線引速度が重要である。本発明者らの実験結果より得られた知見では、線引の当初はたとえ線引速度が同じでも線引長によって特性が変化する事が分かった。例えばＤＣＦ母材について製造線引速まで上げてサンプル取りを行い、サンプル取り後に線速を下げて母材の消費を少なくし、サンプルを測定し線引条件を調整するために線速を上げて調整したが、再現性が無く全くうまくいかなかった。従って製造線速でサンプリングする事は不可欠である事がわかった。また、サンプリングした光ファイバより目標の外径となるまでの区間の線速は低い方が好ましいという開示がある（例えば、特許文献９参照。）ので、製造線速でサンプリングや調整を必ずするというものではない事がわかる。
またこの発明の問題点は、サンプリングしたファイバより目標となるコア径さらには正及び負の区間長を予測しているが、予測とおりの特性になったかは確認されていない。これでは本当に所望の範囲の特性が得られるかは明確でない。
また線引母材が長手で均一であると考えられているが、プリフォームアナライザで測定した精度が正確でない以上長手で均一であるとは必ずしもいえないと思われる。少なくとも線引の開始部や終了部では先の部分でのプリフォームに作用する熱量（ヒータからの加熱とプリフォームの長手に逃げる熱）の違いにより光ファイバ母材のメニスカス形状が異なるために特性が変わることが考えられる。更にプリフォームの長手変動も考えられる。この様な変動に対してはこの発明では全く対応できない。
【０００４】
【特許文献１】
特開昭６４−６９５３６号公報
【特許文献２】
特開昭６４−６９５３７号公報
【特許文献３】
特開２００１−１３０９２２号公報
【特許文献４】
特開２００１−２２０１６７号公報
【特許文献５】
特開昭６４−６９５３６号公報
【特許文献６】
特開昭６４−６９５３７号公報
【特許文献７】
特開２００１−１３０９２２号公報
【特許文献８】
特開２００１−２２０１６７号公報
【特許文献９】
特開２００１−１３０９２２号公報
【０００５】
【発明が解決しようとする課題】
本発明は、上記問題点が解消され、良好な特性を有する光ファイバを安定して得ることのできる光ファイバの製造方法および製造装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明は、
（１）光ファイバ母材を線引炉にて溶融・紡糸して光ファイバとし、前記光ファイバに被覆を施して被覆光ファイバとし、キャプスタンにて前記被覆光ファイバを引き出し、これを巻き取り機で巻き取ることにより光ファイバの線引を行い、光ファイバを製造する方法であって、前記巻き取り機としてダブルスプーラを用い、製造線引速度に到達してから所定時間又は所定長さ線引した後に製造線引速度にてサンプル取りを行い、サンプル取りした光ファイバの特性の測定を行い、得られる測定値が所望の特性の範囲に入るように各線引条件の調整を繰り返し、所望の特性になったことを確認後、製品用の光ファイバの線引を開始することを特徴とする光ファイバの製造方法、
（２）前記測定値が所望の特性の範囲に入るまで、線引テンション、ファイバ外径および線引速度からなる群から選択される少なくとも１つの線引条件の調整を行い、前記サンプル取りと前記特性の測定を繰り返すことを特徴とする（１）項記載の光ファイバの製造方法、
（３）前記特性の測定として、カットオフ、波長分散、波長分散スロープ、実効コア断面積、伝送ロス、ＯＨロス、曲げロス、ＭＦＤおよびＰＭＤからなる群から選択される少なくとも１つの特性の測定を行うことを特徴とする（２）項記載の光ファイバの製造方法、
（４）前記光ファイバ母材が、標準シングルモードファイバに対して分散スロープが小さいかもしくは実効コア断面積が大きなファイバ、分散補償ファイバ（ＤＣＦ）、分散スロープ補償ファイバ（ＤＳＣＦ）またはコアの一部もしくはクラッドにフッ素をドープされたファイバであることを特徴とする（１）、（２）または（３）項記載の光ファイバの製造方法、
（５）前記製品用の光ファイバの線引を開始した後の線引途中にも、所定長さごとに、前記のサンプル取り、特性の測定および線引条件の調整を所望の特性の範囲に入るまで繰り返し行うことを特徴とする（２）〜（４）のいずれか１項記載の光ファイバの製造方法、
（６）前記の線引途中の特性の測定として、カットオフ、波長分散、波長分散スロープ、実効コア断面積、伝送ロス、曲げロス、ＭＦＤおよびＰＭＤからなる群から選択される少なくとも１つの特性の測定を行うことを特徴とする（５）項記載の光ファイバの製造方法、
（７）前記特性の測定ごとに前記サンプル取りを行うことを特徴とする（５）または（６）項記載の光ファイバの製造方法、
（８）前記特性の測定に適した巻き取りのテンションで前記サンプル取りを行うことを特徴とする（５）、（６）または（７）項記載の光ファイバの製造方法、
（９）前記測定値が所望の特性の範囲に入らなくなった場合の光ファイバ母材について、先に線引きした前記測定値が所望の特性の範囲に入る光ファイバの特性の測定値に基づいて、前記母材の外径を削るか、または再度クラッドを足すかして調整を行い、新たな光ファイバ母材とし線引を行うことを特徴とする（１）〜（８）のいずれか１項記載の光ファイバの製造方法、および
（１０）光ファイバ母材を溶融・紡糸して光ファイバとする線引炉と、前記光ファイバに被覆を施す被覆装置と、前記被覆光ファイバを引き出すキャプスタンと、引き出された光ファイバを巻き取る巻き取り機とを有する光ファイバの製造装置であって、前記巻き取り機としてダブルスプーラを用い、製造線引速度に到達してから所定時間又は所定長さ線引した後に製造線引速度にてサンプル取りを行い、サンプル取りした光ファイバの特性の測定を行い、得られる測定値が所望の特性の範囲に入るように線引条件の調整を繰り返し行い、所望の特性に入ったことを確認後、製品用の光ファイバの線引を開始することを特徴とする光ファイバの製造装置
を提供するものである。
【０００７】
【発明の実施の形態】
本発明における線引方法は、光ファイバ母材を線引炉にて溶融・紡糸して光ファイバとし、前記光ファイバを必要に応じて冷却し被覆を施して被覆ファイバとしキャプスタンにて、前記被覆ファイバを引き出し巻き取り機で巻き取る光ファイバの線引方法であって、巻き取り機としてダブルスプーラを用い、製造線速に到達してから所定時間又は所定長さ線引した後にサンプル取りを行い、サンプル取りしたファイバの特性の測定を行い、光ファイバ母材の良否を判定し線引を続けるかどうかを決めるものである。好ましくは、線引開始時にサンプリングを行い線引条件を調整して所定の特性を得られるようにして線引を行う。例えば、以下のように線引を行うことが好ましい。
▲１▼製造線速で製造ファイバ径及び線引テンションで所定時間あるいは所定線引長線引を行い、
▲２▼ダブルスプーラ（デュアル　テイクアップ　ワインダー（ｄｕａｌ　ｔａｋｅ　ｕｐ　ｗｉｎｄｅｒ）とも呼ばれる）を用いて製造線速とほぼ同一の線引速度でサンプリングを行い、
▲３▼サンプリングしたファイバの特性を測定し
▲４▼過去のデータ、あるいは母材のプロファイルと線引速度、テンション等より、所望の特性を得ることのできる線引条件を予測し
▲５▼製造線速で線引条件の調整を行い
▲６▼再度サンプリングを行う
▲７▼▲３▼から▲６▼を繰り返す
▲８▼所定のファイバ特性が得られたら製造を開始する
ここで、▲１▼で所定時間あるいは所定線引長線引を行うのは、線引始めに通常２１０ｍ／分の線速から２００ｍ／分以上の線速まで上げるので、母材の溶融部の形状が安定状態になっていないためである。したがって、一般に、大きな母材ほど、定常状態になるまでに長い時間を必要とする。また、本発明に用いられるダブルスプーラとしては公知のものを用いることができ、例えば特願平５−１８７５８４号に記載の装置を適用することができる。
【０００８】
本発明を図面を参照してより詳細に説明する。図１は本発明の光ファイバ製造方法を適用した製造装置の好ましい一実施形態を示す説明図である。
図１において、光ファイバ母材５は、線引炉２０にて溶融・紡糸されて光ファイバ６となり、前記光ファイバ６は必要に応じて冷却塔２１で冷却され、コーティングダイス３１とダイスホルダー３２を有してなる被覆装置３０および紫外線照射装置４０で被覆を施され被覆光ファイバ７となり、キャプスタン５０にて前記被覆光ファイバ７が引き出され、ガイドプーリ５１を経て、巻き取り機（ダブルスプーラ）６０で巻き取られることにより、線引が行われ光ファイバが製造される。巻取り装置として用いられるダブルスプーラ６０は、ダンサー６３により、線速変動やスプールの巻き太りによるライン速度とスプールの回転速度の変動の調整を行う。可動プーリ６４ａ及び６４ｂ（ただし、可動プーリ６４ａはスプール６１に巻き取るときの位置を、可動プーリ６４ｂはスプール６２に巻き取るときの位置を表す。）を上下に移動させスプール６１又は６２に光ファイバをガイドする。こうして、パスライン８を経て第１のスプール６１に、パスライン９を経て第２のスプール６２に、光ファイバを分けて巻き取ることができる。
この様なダブルスプーラ６０を有することにより、製造線引速度に到達してから所定時間又は所定長さ線引した後に、ダブルスプーラ６０中の第１のスプール６１から第２のスプール６２に製造線引速度でシフトを行い、第１のスプールをダブルスプーラから取り外して所定長さのサンプル取りを行うことができる。サンプル取りした光ファイバの特性の測定を行い、光ファイバの良否を判定し線引を続けるかどうかを決める。ここで、所定時間または所定長さとは、母材のサイズや種類や線引速度等により変わるものであり特に制限されないが、例えば所定時間として１０分〜１２０分、所定長さとして５ｋｍ〜５０ｋｍが好ましい。
サンプル取りした光ファイバが良好な所望の特性を有していれば、そのままの線引条件で第２のスプール６２にて巻き取りを続ける。このようにして所望の特性を有する光ファイバが製品として得られる。不良であればそのままサンプルとして光ファイバを第２のスプール６２に巻き取りながら線引条件が調整される。
【０００９】
線引条件の調整は、測定結果により調整する条件が異なるが、本発明では線引テンション、ファイバ外径、線引速度を変えることが可能である。
線引テンションの調整は、テンション計測装置３で測定したデータに基づき、制御装置１及び２により線引炉２０の炉温を上下させることにより、テンションを下げたり上げたりできる。ファイバ外径の調整は、ファイバ外径の目標設定値を変えることで、ファイバ外径計測装置４で測定したデータに基づき、制御装置１及び２により、母材送りモータ１１を有する母材送り装置１０の母材の送り速度と、キャプスタンモータ５２を有するキャプスタン５０の速度とを制御をすることで行うことができる。また、炉温とファイバ外径を一定のまま線引速度を変えると線引テンションが変化するとともにメニスカス部（母材の溶融部）の形状が変化する（伝送ロスやファイバ径変動、曲がりに影響する）。さらに、炉温と炉内のガス条件（ガス流量など）を変えることで線引テンションを変えることもできる。また、テンション一定で炉温を変えることができる。これは伝送ロスやファイバ強度に影響する。
【００１０】
本発明における線引条件の調整は、線引テンション、ファイバ外径および線引速度からなる群から選択される少なくとも１つを調整することが好ましい。この後、ダブルスプーラでシフトして再度前記サンプル取りおよび特性の測定を行い、所望の特性の範囲に入る様に線引条件の調整を繰り返す。
前記特性には、カットオフ、波長分散、波長分散スロープ、実効コア断面積、伝送ロス、ＯＨロス、曲げロス、ＭＦＤまたは偏波モード分散（ＰＭＤ）などがある。これら特性の所望の範囲はそれぞれ、製造される光ファイバーの用途により異なり特に制限されるものではないが、例えば、カットオフ（２ｍ法）は９００〜１６００ｎｍ、波長分散は１５５０ｎｍで０〜２０ｐｓ／ｎｍ／ｋｍ、波長分散スロープは１５５０ｎｍで、ＳＭＦやＮＺ−ＤＳＦでは０．０１〜２ｐｓ／ｎｍ^２／ｋｍ、ＤＣＦ、ＤＳＣＦやＲＤＦといった分散補償逆分散ファイバでは−２０〜−３００ｐｓ／ｎｍ^２／ｋｍ、実効コア断面積は２０〜１５０μｍ^２、伝送ロスは１５５０ｎｍで、ＳＭＦやＮＺ−ＤＳＦでは０．１５〜５ｄＢ／ｋｍ、ＤＣＦやＤＳＣＦといった逆分散ファイバでは−０．０５〜−２ｄＢ／ｋｍ、ＯＨロスは０．２６〜３ｄＢ／ｋｍ（同上）、曲げロスは０．０６〜２０ｄＢ／ｍ（φ２０ｍｍマンドレルに巻きつけて）（同上）、ＭＦＤは３〜１２μｍ、偏波モード分散（ＰＭＤ）はファイバの種類により異なり、好ましくは１ｐｓ／ｍ^１／２以下とするが、これに制限されない。
【００１１】
本発明における光ファイバ母材は、特に制限するものではないが、標準シングルモードファイバに対して分散スロープが小さいファイバもしくは実効コア断面積が大きなファイバ、分散補償ファイバ（ＤＣＦ）、分散スロープ補償ファイバ（ＤＳＣＦ）またはコアの一部もしくはクラッドにフッ素をドープされたファイバが好ましく用いられる。
本発明に用いられる光ファイバの被覆は特に制限されるものではないが、例えば紫外線硬化樹脂、電子線硬化樹脂、熱硬化樹脂等による被覆が挙げられる。
【００１２】
本発明において、特開２００１−１３０９２２の様に所定波長における波長分散が正及び負の区間がある光ファイバを製造する場合については、正負区間の両方について前記線速条件の調整を行うことが好ましい。
また本発明において、例えば母材のコア径の長手変動や母材外径の変動に対応するなどのために、前記線引条件の調整が完了し製品用光ファイバの線引を開始した後にも、所定長さごとに前記サンプル取りおよび前記特性の測定を行い、線引途中にも前記線引条件の調整を行うことが好ましい。これは、前述の光ファイバは特に特性の許容範囲が狭いか、ファイバの作り込みが難しいためである。
この所定長さは、母材のサイズ（φ３０ｍｍから１００ｍｍ）により異なるが、例えばＤＣＦの場合１０ｋｍから１００ｋｍごとが挙げられ、このような所定長さごとにダブルスプーラ６０でシフトを行いサンプリングをし前記▲３▼から▲８▼を行うことが好ましい。
このような線引途中での特性の測定は、線引開始初期に行う特性の測定と同様でもよいが、好ましくは、カットオフ、波長分散、波長分散スロープ、実効コア断面積、伝送ロス、曲げロス、ＭＦＤおよびＰＭＤからなる群から選択される少なくとも２つのトレードオフとなる関係にある特性の測定を行うことが好ましい。
【００１３】
本発明におけるサンプリングは、前記特性の測定に必要とする長さごとに前記サンプル取りを行うことが好ましく、また、前記特性の測定に適した巻き取りのテンションでサンプリングを行うことが好ましい。
本発明において、線引初期または線引途中で前記特性の測定結果が大幅に不良である場合の光ファイバ母材は、先に線引きした光ファイバの特性を測定し、その結果をもとに、前記母材の外径を削るか、または再度クラッドを足すかなどして調整を行い、新たな光ファイバ母材とし線引を行うことが好ましい。
【００１４】
【実施例】
次に本発明を実施例に基づきさらに詳細に説明するが、本発明はこれに制限されるものではない。
実施例１
本発明によりＷ型のＤＣＦ母材を図１の製造装置を用いて線引して光ファイバを製造した。ダブルスプーラとしては、先に述べた特願平５−１８７５８４号に記載の装置を適用した。なお、光ファイバは紫外線硬化樹脂（以後、ＵＶ樹脂と略す）で被覆した。
ここで線引条件の調整は以下のように行った。
▲１▼製造線速３００ｍ／ｍｉｎ、製造ファイバ径１２５μｍ及び線引テンション３３０ｇの線引条件で所定時間（１０分〜６０分）あるいは所定線引長（５ｋｍ〜２０ｋｍ）線引を行い線引状態を安定化させた。
▲２▼製造線速とほぼ同一の線引速度３００ｍ／ｍｉｎでダブルスプーラで所定長のサンプリングを行った。伝送ロスや波長分散や波長分散スロープ、ＰＭＤ等を測定する場合は、２〜６ｋｍサンプリングした。カットオフや曲げロス、ＭＦＤや実効コア断面積を測定する場合は数百ｍ以下とした。
▲３▼サンプリングしたファイバの波長分散と曲げロスを測定した。
▲４▼過去のデータ、あるいは母材のプロファイルと線引速度、テンション等より所望の特性が得られる線引条件を予測した。
【００１５】
この場合、ＤＣＦは、波長分散Ｄが負となった。また分散Ｄと曲げロスはトレードオフの関係になった。曲げロスはコア径を大きくした方が良くなり、波長分散Ｄの絶対値は小さくなる。そこでまず曲げロスが所望の特性の範囲である１０ｄＢ／ｍ以下に入るようにコア径を決めた。即ちファイバ外径を大きくした。但し、この場合の設計時の目標ファイバ外径を１２５μｍとしていたので、１２０μｍから１３０μｍの範囲で調整できない場合は、線引を中断して母材の再加工を行なうようにした。
曲げを強くするためには、コア径を大きくすると良い事が、過去のデータよりわかっているので、０．０５μｍ大きくした。ファイバ外径としては１２５μｍから１２６μｍとなるようにファイバ外径制御の設定値を変えた。この場合分散は小さくなる傾向にある。１０分して外径が安定した所で、更に１０分待ってサンプリングをした。曲げロスは波長１５５０ｎｍで２ｄＢ／ｍ（φ２０ｍｍのマンドレルに巻いたロス増の結果）となった。
【００１６】
今度は分散の絶対値が小さくなったので、線引テンションを４０ｇ小さくして、分散の絶対値を大きくした。この結果、曲げロス５ｄＢ／ｍ（１５５０ｎｍにて）、分散が目標の−１２０ｐｓ／ｎｍ／ｋｍとする事が出来た。この条件で製品用光ファイバの線引を開始した。
２５ｋｍ線引した所でダブルスプーラをシフトさせサンプルとして巻き取ったファイバの特性を測定した結果、波長分散の絶対値が大きくなっていた。そこで、炉温を下げて、線引テンションを２０ｇ上げた。テンションが安定してから１０分待ってサンプル取りを行なった。
その結果、曲げロスが、４．６ｄＢ／ｍで分散が−１２３ｐｓ／ｎｍ／ｋｍとなり規格の中心地（−１２０）に近づいたので、製品用光ファイバの線引を続けた。このようにあと２回ダブルスプーラでシフトしサンプル取りを行ない調整を行なった。
以上のようにして、良品として８０ｋｍの光ファイバが得られた。
【００１７】
比較のために同様の母材および線引スタート時の線引条件で、ファイバ外径１２５μｍ、線引テンション３３０ｇ、線速３００ｍ／分となるように線引条件を決めた以外は、上記実施例１と同様にして立ち上げを行ったところ、頭だしで合格していても、この場合は、実施例１と同等の良品の光ファイバは５０ｋｍ程度しか取れなかった。
【００１８】
実施例２
Ｗ−ｓｅｇ型の分散スロープまで保証したＤＣＦファイバ母材を実施例１と同様に線引して光ファイバを製造した。なお、光ファイバはＵＶ樹脂で被覆した。
ここで線引条件の調整は以下のように行った。
▲１▼製造線速５００ｍ／ｍｉｎ、製造ファイバ径１２５μｍ及び線引テンション２９０ｇの線引条件で所定時間（６０分）あるいは所定線引長（２０ｋｍ）線引を行い線引状態を安定化させた。
▲２▼製造線速とほぼ同一の線引速度５００ｍ／ｍｉｎでダブルスプーラでシフトを行い所定長のサンプリングを行った。伝送ロスや波長分散や波長分散スロープ、ＰＭＤ等を測定する場合は、２〜６ｋｍサンプルリングした。カットオフや曲げロス、ＭＦＤや実効コア断面積を測定する場合は数百ｍ以下とした。
▲３▼サンプリングしたファイバの波長分散と波長分散スロープ及び曲げロスを測定した。
▲４▼過去のデータ、あるいは母材のプロファイルと線引速度、テンション等より所望の特性が得られる線引条件を予測した。
【００１９】
この場合、ＤＣＦは、波長分散Ｄ、波長分散スロープＳが負となった。また分散Ｄと曲げロスはトレードオフの関係になった。曲げロスはコア径を大きくした方が良くなり、また波長分散Ｄの絶対値は小さくなり、波長分散スロープＳの絶対値は大きくなる。そこで実施例１と同様にまず曲げロスが所望の特性の範囲である１０ｄＢ／ｍ以下に入るようにコア径を決めた。即ちファイバ外径を大きくした。但し、この場合の設計時の目標ファイバ外径を１２５μｍとしていたので、１２０μｍから１３０μｍの範囲で調整できない場合は、線引を中断して母材の再加工を行なうようにした。
曲げを強くするためには、コア径を大きくすると良い事が、過去のデータよりわかっているので、０．１μｍ大きくした。ファイバ外径としては１２５μｍから１２７μｍとなるようにファイバ外径制御の設定値を変えた。この場合波長分散Ｄの絶対値は小さくなる傾向にある。波長分散のスロープＳの絶対値も小さくなる。しかし、この場合分散Ｄと分散スロープＳの比をＤＰＳ＝Ｄ／Ｓとすると、ＤＰＳが所定の範囲（ＤＰＳ＝３３０から３６０が目標の範囲）となる様にする必要がある。この場合、ＤＰＳ（ｎｍ）は小さくなる。１０分して外径が安定した所で、更に１０分待ってサンプリングをした。曲げロスは３ｄＢ／ｍ（φ２０ｍｍのマンドレルに巻いたロス増の結果）となった。
【００２０】
今度はＤＰＳが３８０ｎｍと大きくなるので、線引テンションを３０ｇ小さくして、ＤＰＳを小さくした。この結果、曲げロス５ｄＢ／ｍ（１５５０ｎｍにて）、ＤＰＳ３５０（ｎｍ）と目標の範囲内にする事が出来た。この条件で製品用光ファイバの線引を開始した。
５０ｋｍ線引した所でダブルスプーラをシフトさせサンプルとして巻き取ったファイバの特性を測定した結果、曲げロスが１０ｄＢ／ｍ（１５５０ｎｍ）大きくなっていた。そこで、炉温を下げて、線引テンションを２０ｇ上げた。テンションが安定してから１０分待ってサンプル取りを行なった。
その結果、曲げロスが、６ｄＢ／ｍでＤＰＳ３４５ｎｍとなり曲げ規格の６ｄＢ／ｍとぎりぎりであったので、コア径を０．０３μｍ小さくする調整を行なった。ファイバ外径としては１２６．４μｍとなるようにファイバ外径設定値を変えた。
ファイバ外径が線速が安定してから、２０分待ってサンプル取りを行なった。その結果、曲げロスが４．３ｄＢ／ｋｍでＤＰＳ３５５ｎｍと規格内となったので、製品用光ファイバの線引を続けた。このような調整を行ないながら後１０回ダブルスプーラでシフトしサンプル取りを行ない調整を行なった。
以上のようにして、良品として５００ｋｍの光ファイバが得られた。
【００２１】
比較のために、線速５００ｍ／分、ファイバ外径１２５μｍ、線引テンション２９０ｇとなるように線引条件を決めた以外は、上記実施例２と同様にして立ち上げを行ったところ、頭だしで合格していても、この場合、実施例２と同等の良品の光ファイバは１００ｋｍ程度しか取れなかった。
【００２２】
実施例３
１５５０ｎｍの分散が４〜１０ｐｓ／ｎｍ／ｋｍで分散スロープが０．０５ｐｓ／ｎｍ^２／ｋｍ以下、ＭＦＤが８〜８．５μｍを満たす、ＮＺ−ＤＳＦ（ノンゼロ分散シフト光ファイバ）母材を実施例１と同様に線引して光ファイバを製造した。なお、光ファイバはＵＶ樹脂で被覆した。
ここで線引条件の調整は以下のように行った。
▲１▼製造線速１０００ｍ／ｍｉｎ、製造ファイバ径１２５μｍ及び線引テンション１７０ｇの線引条件で所定時間（６０分）あるいは所定線引長（２０ｋｍ）線引を行い線引状態を安定化させた。
▲２▼製造線速とほぼ同一の線引速度１０００ｍ／ｍｉｎでダブルスプーラでシフトし所定長のサンプリングを行った。伝送ロスや波長分散や波長分散スロープ、ＰＭＤ等を測定する場合は、２〜６ｋｍサンプリングした。カットオフや曲げロス、ＭＦＤや実効コア断面積を測定する場合は数百ｍ以下とした。
▲３▼サンプリングしたファイバの波長分散と波長分散スロープ及びＭＦＤを測定した。
▲４▼過去のデータ、あるいは母材のプロファイルと線引速度、テンション等より所望の特性が得られる線引条件を予測した。
【００２３】
この場合、低分散スロープのＮＺ−ＤＳＦは、波長分散Ｄ、波長分散スロープが正となった。また分散ＤとＭＦＤはトレードオフの関係になった。ＭＦＤのコア径依存性はプロファイルによりコア径に対して大きくなる場合と小さくなる場合がある、この母材の場合は、今までのデータよりコア径を大きくするとＭＦＤが小さくなる事が分かっているので、ＭＦＤを大きくするためにファイバ外径を１２５μｍから１２４．５μｍに小さくした。この場合波長分散、波長分散スロープとも小さくなる。
ファイバ外径制御の目標値を線引後の外径が１２４．５μｍとなるように設定し、線速、ファイバ外径が一定となるまで待ち、更に、２０ｋｍ線引した後に再度ダブルスプーラでシフトを行ないサンプル取りした。
【００２４】
ＭＦＤが７．８μｍ〜８．１μｍと大きくなり、１５５０ｎｍでの波長分散とスロープは４．６ｐｓ／ｎｍ／ｋｍ、０．０４８ｐｓ／ｎｍ^２／ｋｍと規格を満足した。この条件で製品用光ファイバの線引を開始した。
１００ｋｍ線引してダブルスプーラでシフトし巻き取ったボビンのファイバの端末よりサンプルファイバを取り、波長分散、スロープそしてＭＦＤを測定した。分散が４．２ｐｓ／ｎｍ／ｋｍと小さくなっていた。分散スロープは０．０４６　ｐｓ／ｎｍ^２／ｋｍで規格に対して多少余裕があったので、炉温を下げて線引テンションを３０ｇ上げた。線速、ファイバ外径が安定してから、２０ｋｍ線引して再度サンプリングを行なった。
その結果、分散が４．６　ｐｓ／ｎｍ／ｋｍと改善し、ＭＦＤが８．１μｍ及び分散スロープが０．０４８　ｐｓ／ｎｍ^２／ｋｍと規格内であったので、製品用光ファイバの線引を続けた。このような調整を行ないながら後５回ダブルスプーラでシフトしサンプル取りを行ない調整を行なった。
以上のようにして、良品として４００ｋｍ以上の光ファイバが得られた。
【００２５】
比較のために実施例３と同様の母材および線引スタート時の線引条件で、線速１０００ｍ／分、ファイバ外径１２５μｍ、線引テンション１２０ｇとなるように線引条件を決め、立ち上げを行ったところ、頭だしで合格していても、この場合、実施例３と同等の良品としては２００ｋｍ程度の光ファイバしか取れなかった。
【００２６】
実施例４
コアにフッ素が比屈折率差で約Δ＝０．０１％、クラッドにフッ素が約Δ＝０，３５％ドープされたカットオフが１５００ｎｍにシフトしたシングルモードファイバ（ｆｕｌｌｙ　ｆｌｕｏｒｉｎｅ　ｄｏｐｅ　ｆｉｂｅｒ（以後、ＦＦファイバと呼ぶ））母材を実施例１と同様に線引して光ファイバを製造した。なお、光ファイバはＵＶ樹脂で被覆した。
ここで線引条件の調整は以下のように行った。
この場合は、カットオフと１５５０ｎｍの伝送ロスの特性を測定した。伝送ロスは線引炉温度と線引テンションに大きく依存するので５ｋｍのサンプルを取り測定した。カットオフはテンションとコア径に依存するので、先ずはカットオフをあわせるためのファイバ外径を今までの実施例と同じように変更し、サンプリングを行い次にテンションを測定して伝送ロスを下げる事にした。
【００２７】
線速は３００ｍ／ｍｉｎとしテンション３０ｇ、ファイバ外径１２５μｍの線引条件で線引をスタートした。カットオフが１５２０ｎｍと高かったので、コア径を小さくするために、ファイバ外径を１２４．３μｍと小さくなるようにファイバ外径制御の設定値を変更した。このときの伝送ロスは０．１８０ｄＢ／ｋｍと高かった。線速、ファイバ外径が安定してから、１０ｋｍ線引して再度サンプリングを行なった。その結果、カットオフは１４８０ｎｍまで低下した。このときの伝送ロスは０．１９２ｄＢ／ｋｍであった。そこで線引テンションを２０ｇまで炉温を上げるか、炉内に供給するガスを少なくして下げた。線速、ファイバ外径が安定してから、１０ｋｍ線引して再度サンプリングを行なった。その結果、カットオフ波長、伝送ロスがそれぞれ、１４９２ｎｍ、０．１７５ｄＢ／ｋｍまで改善し、目標の規格の範囲となったので製品用光ファイバの線引を開始した。
【００２８】
３０ｋｍ線引後ダブルスプーラでシフトし、巻き取ったボビンの端末よりファイバを５ｋｍ取り出し、伝送ロスとカットオフの測定を行った。伝送ロスが０．１８３ｄＢ／ｋｍとカットオフが１４９７ｎｍであったので、線引テンションを２５ｇに変更した。線速、ファイバ外径が安定してから、１０ｋｍ線引して再度サンプリングを行なった。その結果、カットオフが１４９５ｎｍ、伝送ロス０．１７６ｄＢ／ｋｍであったので、そのままの条件で製品用光ファイバの線引を続けた。このような調整を繰り返してダブルスプーラで７回シフトを行い線引ボビンを得た。
以上のようにして、良品として１００ｋｍから１８０ｋｍの光ファイバが得られた。
【００２９】
比較のために、上記実施例４と同様の母材および線引スタート時の線引条件で、線速３００ｍ／分、ファイバ外径１２５μｍ、線引テンション３０ｇとなるように線引条件を決めた以外は、上記実施例４と同様にして立ち上げを行ったところ、長手変動があるこの母材では５０ｋｍから１００ｋｍしか実施例４と同等の良品が取れなかった。
【００３０】
実施例５
実施例４に対し、ＦＦファイバの調整を以下の通りとした以外は同様にして光ファイバを製造した。ここでＦＦファイバの調整としては、伝送ロスが線引炉温度と線引テンションに依存する事を用いて、最初のサンプリングでカットオフと１５５０ｎｍの伝送ロスを測定し、所望のカットオフになるように線引テンションを調整した。
例えばカットオフが高い場合には線引テンションを下げる（線引炉温を上げる）。またカットオフが低い場合にはテンションを上げる（線引炉温を下げる）。この様に線引条件を調整した後、線速とファイバ外径が安定した後に５ｋｍ線引後、再度サンプリングを行いカットオフと伝送ロスを測定した。カットオフが規格内に入ったら、伝送ロスの調整を行った。伝送ロスが高い場合、原因が二つ有り、炉温が高すぎる場合と、光ファイバの高温部の冷却速度が速すぎる場合がある。過去の経験から伝送ロスの波長特性より判断した。この場合炉温が高すぎたので、テンションを同じにしつつ、線引炉温を下げ、更に炉内に供給するガス量を下げる調整をした。これも事前の実験で条件を求めておくと調整回数が少なくできる。この調整をカットオフと伝送ロスが共に規格内に入るまで繰り返した。規格に入った後に製品用光ファイバの線引を開始した。実施例４の様に所定の長さ線引した後に、ダブルスプーラで切り替えて巻き取った光ファイバの特性を測定して、必要に応じて線引条件の調整をおこなった。結果は実施例４と同様の効果が得られた。
【００３１】
どの実施例の母材も傾向としては、母材の立ち上げ部と終端部で特性の変動が大きくなった。従って、上記調整は、線引立ち上げ初期と、線引終了時に行う事が多かった。また２つの特性の合わせこみを別々にサンプリングして行う例について示したが、母材ごとに調整する特性がほぼ決まるので、同時に両方の調整行う事も可能である。
【００３２】
【発明の効果】
本発明の製造方法及び製造装置は以下の効果を奏する。
１）線引速度をほぼ製造線速としているために線引条件を変更した後の光ファイバ特性の予測値と実際値の差が小さくできる。（線速変動による外乱が無くなったため）
２）所定の特性に入った事を確認してから製造に入る事ができる。
３）特性予測を、過去のデータあるいは、更に母材のプロファイルと線引速度、テンション等より線引条件を予測する事により正確な特性予測ができる。
４）ダブルスプーラを用いているために、サンプリングの回数が多くてもまた線速が１０００ｍ／ｍｉｎ以上でもサンプリングができる。さらに線引の最初だけでなく、途中にもサンプリングが行える。
５）線引途中でもサンプリングして同様の調整が行えるために長手変動があっても調整ができ、歩留まりを大幅に改善できる。
６）従って、長手変動がある母材についても適用できる。（歩留まりを改善できる。）
７）線引最初や途中よりつかえない母材の場合も、線引を中断する事で無駄な線引をしなくてすむ。
８）線引初期あるいは線引途中で特性が入らなくなった光ファイバ母材を、先に線引きした光ファイバの特性を測定して前記母材の外径を削るか、再度クラッドを足すかして調整を行い新たな線引母材とし線引を行う事により、前記母材を有効利用できる。
したがって、本発明の製造方法および製造装置は良好な特性を有する光ファイバを安定して得るのに好適である。
【図面の簡単な説明】
【図１】本発明の光ファイバ製造方法を適用した製造装置の好ましい一実施形態を示す説明図である。
【符号の説明】
１　第１の制御装置
２　第２の制御装置
３　テンション計測装置
４　ファイバ外径計測装置
５　光ファイバ母材
６　光ファイバ
７　被覆光ファイバ
８　スプール６１に巻取るときのパスライン
９　スプール６２に巻取るときのパスライン
１０　母材送り装置
１１　母材送りモ−タ
２０　線引炉
２１　冷却筒
３０　被覆装置
３１　コーティングダイス
３２　ダイスホルダー
４０　紫外線照射装置
５０　キャプスタン
５１　ガイドプーリ
５２　キャプスタンモ−タ
６０　巻取り装置（ダブルスプ−ラ）
６１　第１のスプ−ル
６２　第２のスプ−ル
６３　ダンサー
６４ａ、６４ｂ　可動プーリ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for manufacturing an optical fiber by drawing an optical fiber whose characteristics are particularly difficult to adjust with an optical fiber drawing method and apparatus. In particular, variations in the optical fiber preform in the longitudinal direction (for example, variations in core diameter and refractive index distribution, and in the case of a plurality of core portions, variations in the refractive index and distribution of each core portion and the thickness of each layer are considered). The present invention relates to a method and an apparatus for manufacturing an optical fiber which can cope with a certain base material.
[0002]
[Prior art]
In drawing an optical fiber, transmission of cutoff, dispersion or zero dispersion wavelength, mode field diameter (abbreviated as MFD), or the like is performed unless the drawing speed (also referred to as a linear speed in this specification) becomes substantially constant. It does not become a product because of its characteristic changes. For this purpose, discard the coated fiber with an air gun without winding it up until the fiber diameter and coating diameter reach the production linear speed and stabilize the fiber diameter, or provide pinch roll means on the take-up bobbin, and perform sampling at the production linear speed. Then, after inspecting the coated optical fiber to confirm that the coated optical fiber has a predetermined quality, it is disclosed that the coated optical fiber is wound around a winding machine (for example, see Patent Documents 1 and 2). By doing so, there is an advantage that the sampling of the optical fiber can be performed at the production linear speed, and furthermore, when the optical fiber has a predetermined quality, it can be put into production immediately, thereby improving the productivity.
Further, in a method for manufacturing an optical fiber in which sections in which chromatic dispersion at a predetermined wavelength is positive and negative are alternately provided, the chromatic dispersion of the optical fiber obtained at the start of drawing is measured, and a positive value is determined based on the measured chromatic dispersion. It is disclosed that a target fiber diameter in a negative dispersion section is determined and drawing is performed (for example, see Patent Document 3). This is because in a fiber with a reduced dispersion slope or an optical fiber with a large effective core area, the refractive index distribution is complicated, the refractive index changes greatly, and the measurement accuracy of the preform analyzer is not sufficient. For this reason, a manufacturing method for performing such sampling has been proposed.
In the method of drawing an optical fiber preform having a uniform refractive index distribution in the longitudinal direction, the chromatic dispersion and the dispersion slope of the optical fiber of a fixed length obtained at the start of drawing are measured. The target drawing tension and the target core diameter for obtaining the target chromatic dispersion based on the chromatic dispersion and the dispersion slope are determined, and the remaining portion of the base material is drawn with the target drawing tension and the core diameter. Thing is disclosed. Further, it discloses that a target tension is determined in the first sample, a target core diameter is predicted in the next sample, and the remaining base material is drawn using the predicted target tension and the core diameter. As a method of adjusting the drawing tension, it is disclosed that the drawing speed is adjusted and the temperature of the drawing furnace is adjusted. This is because the processing accuracy of the base material is insufficient to make a dispersion compensating fiber (DCF), and the target dispersion characteristics can be easily obtained even if the measurement accuracy of the preform analyzer is poor. Manufacturing methods that perform sampling have been proposed. It is described that it is particularly suitable for the production of DCF that is sensitive to changes in drawing tension and core diameter (for example, see Patent Document 4).
[0003]
However, conventionally, it is only necessary to determine whether or not the drawn optical fiber has a desired quality, and there is no disclosure of the content of actively matching the characteristics. Further, the quality is intended for the core diameter, the fiber diameter, and the uneven thickness of the coating (for example, see Patent Documents 5 and 6).
Further, it is disclosed that the chromatic dispersion of an optical fiber having a fixed length obtained at the start of drawing is measured (for example, see Patent Documents 7 and 8). Unknown.
In particular, if the drawing speed differs, the characteristics of the fiber also change, so the drawing speed is important. According to the knowledge obtained from the experimental results of the present inventors, it has been found that the characteristics change with the drawing length even at the same drawing speed at the beginning of drawing. For example, the DCF base material is sampled by increasing the drawing speed to the production drawing speed, and after taking the sample, reducing the drawing speed to reduce the consumption of the base material, increasing the drawing speed to measure the sample and adjust the drawing conditions. I adjusted it, but it didn't work because there was no reproducibility. Therefore, it was found that sampling at the production line speed was indispensable. Also, there is a disclosure that the linear velocity in a section until the target outer diameter becomes smaller than that of the sampled optical fiber is preferably lower (for example, see Patent Document 9). It turns out that it is not a thing.
Further, the problem of the present invention is to predict the target core diameter and the positive and negative section lengths from the sampled fiber, but it is not confirmed whether the characteristics are as expected. It is not clear that the desired range of characteristics can be obtained.
Although the drawing base material is considered to be uniform in the longitudinal direction, it is considered that the drawing base material is not necessarily uniform in the longitudinal direction unless the precision measured by the preform analyzer is accurate. At least at the beginning and end of drawing, the meniscus shape of the optical fiber preform is different due to the difference in the amount of heat acting on the preform at the previous part (heating from the heater and heat escaping to the length of the preform). May change. Furthermore, longitudinal variations of the preform are also conceivable. The present invention cannot cope with such a variation at all.
[0004]
[Patent Document 1]
JP-A-64-69536
[Patent Document 2]
JP-A-64-69538
[Patent Document 3]
JP 2001-130922 A
[Patent Document 4]
JP 2001-220167 A
[Patent Document 5]
JP-A-64-69536
[Patent Document 6]
JP-A-64-69538
[Patent Document 7]
JP 2001-130922 A
[Patent Document 8]
JP 2001-220167 A
[Patent Document 9]
JP 2001-130922 A
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical fiber manufacturing method and apparatus capable of solving the above problems and stably obtaining an optical fiber having good characteristics.
[0006]
[Means for Solving the Problems]
The present invention
(1) An optical fiber preform is melted and spun in a drawing furnace to form an optical fiber, the optical fiber is coated to form a coated optical fiber, and the coated optical fiber is drawn out by a capstan and wound up. A method for manufacturing an optical fiber by drawing an optical fiber by winding it with a machine, using a double spooler as the winding machine, for a predetermined time or a predetermined length after reaching a manufacturing drawing speed. After drawing, a sample is taken at the production drawing speed, the characteristics of the sampled optical fiber are measured, and the adjustment of each drawing condition is repeated so that the obtained measured value falls within the range of the desired characteristics. After confirming that the characteristics have been obtained, a method of manufacturing an optical fiber, which starts drawing an optical fiber for a product,
(2) Adjusting at least one drawing condition selected from the group consisting of drawing tension, fiber outer diameter, and drawing speed until the measured value falls within a range of a desired characteristic; The method for producing an optical fiber according to (1), wherein the measurement of the characteristics is repeated.
(3) As the measurement of the characteristic, measurement of at least one characteristic selected from the group consisting of cutoff, chromatic dispersion, chromatic dispersion slope, effective core area, transmission loss, OH loss, bending loss, MFD, and PMD is performed. (2) The method for producing an optical fiber according to (2),
(4) The optical fiber preform is a fiber having a smaller dispersion slope or a larger effective core area than a standard single mode fiber, a dispersion compensating fiber (DCF), a dispersion slope compensating fiber (DSCF), or a part of a core. Alternatively, the method according to (1), (2) or (3), wherein the cladding is a fiber doped with fluorine.
(5) During the drawing after the drawing of the optical fiber for the product is started, the sample is taken, the characteristics are measured, and the drawing conditions are adjusted within a desired characteristic range at predetermined intervals. (2) The method for producing an optical fiber according to any one of (2) to (4),
(6) As the measurement of the characteristic during the drawing, at least one characteristic selected from the group consisting of cutoff, chromatic dispersion, chromatic dispersion slope, effective core area, transmission loss, bending loss, MFD and PMD is measured. The method for producing an optical fiber according to (5), wherein the measurement is performed.
(7) The method of manufacturing an optical fiber according to (5) or (6), wherein the sample is taken every time the characteristic is measured.
(8) The method for producing an optical fiber according to (5), (6) or (7), wherein the sample is taken at a winding tension suitable for measuring the characteristic.
(9) For the optical fiber preform when the measured value does not fall within the desired characteristic range, based on the measured value of the characteristic of the optical fiber in which the previously drawn measured value falls within the desired characteristic range, The method according to any one of (1) to (8), wherein adjustment is performed by cutting the outer diameter of the base material or adding a clad again to draw a new optical fiber base material. The method of manufacturing an optical fiber according to the above, and
(10) A drawing furnace for melting and spinning an optical fiber preform into an optical fiber, a coating device for coating the optical fiber, a capstan for extracting the coated optical fiber, and winding the extracted optical fiber. An apparatus for manufacturing an optical fiber having a take-up winding machine, wherein a double spooler is used as the winding machine, and after reaching a production drawing speed for a predetermined time or a predetermined length, the production drawing speed is reduced. Samples are taken, the characteristics of the sampled optical fiber are measured, and the drawing conditions are repeatedly adjusted so that the measured values fall within the desired characteristics range, confirming that the desired characteristics have been achieved. An optical fiber manufacturing apparatus characterized by starting drawing of an optical fiber for a product afterwards.
Is provided.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The drawing method in the present invention, the optical fiber preform is melted and spun in a drawing furnace to form an optical fiber, and the optical fiber is cooled and coated as necessary to form a coated fiber and a capstan, This is a method for drawing an optical fiber in which the coated fiber is drawn by a draw-up take-up machine, and a double spooler is used as a take-up machine. Then, the characteristics of the sampled fiber are measured, and the quality of the optical fiber preform is determined to determine whether or not to continue drawing. Preferably, sampling is performed at the start of drawing, and drawing is performed so as to obtain predetermined characteristics by adjusting drawing conditions. For example, it is preferable to draw as follows.
(1) Perform a predetermined time or a predetermined length drawing at a manufacturing fiber speed and a manufacturing fiber diameter at a manufacturing linear speed,
{Circle around (2)} Using a double spooler (also called a dual take up winder), perform sampling at a drawing speed almost equal to the production linear speed,
(3) Measure the characteristics of the sampled fiber
(4) From the past data or the profile of the base material and the drawing speed, tension, etc., predict the drawing conditions that can obtain the desired characteristics.
(5) Adjust the drawing conditions at the production line speed.
(6) Perform sampling again
Repeat steps 7 to 3 to 6
(8) Start manufacturing when the specified fiber characteristics are obtained.
Here, performing the predetermined time or the predetermined length drawing in (1) is because the linear speed is usually increased from 210 m / min to 200 m / min or more at the beginning of drawing, so that the shape of the molten portion of the base material is increased. Is not in a stable state. Therefore, in general, a larger base material requires a longer time to reach a steady state. As the double spooler used in the present invention, a publicly known double spooler can be used, and for example, an apparatus described in Japanese Patent Application No. 5-187584 can be applied.
[0008]
The present invention will be described in more detail with reference to the drawings. FIG. 1 is an explanatory view showing a preferred embodiment of a manufacturing apparatus to which the optical fiber manufacturing method of the present invention is applied.
In FIG. 1, an optical fiber preform 5 is melted and spun in a drawing furnace 20 to become an optical fiber 6, and the optical fiber 6 is cooled by a cooling tower 21 if necessary, and a coating die 31 and a die holder 32 are formed. The coated optical fiber 7 is coated by a coating device 30 having a coating device and an ultraviolet irradiation device 40 to form a coated optical fiber 7. The coated optical fiber 7 is drawn out by a capstan 50, and is passed through a guide pulley 51. ) By being wound at 60, drawing is performed and an optical fiber is manufactured. The double spooler 60 used as a winding device uses a dancer 63 to adjust linear speed fluctuations and fluctuations in line speed and spool rotation speed due to thickening of the spool. The movable pulleys 64a and 64b (where the movable pulley 64a indicates the position when winding on the spool 61 and the movable pulley 64b indicates the position when winding on the spool 62) are moved up and down, and the optical fiber is moved to the spool 61 or 62. Guide. In this manner, the optical fiber can be separately wound around the first spool 61 via the pass line 8 and the second spool 62 via the pass line 9.
By having such a double spooler 60, after a predetermined time or a predetermined length has been drawn after reaching the production line drawing speed, the production spool is transferred from the first spool 61 in the double spooler 60 to the second spool 62. The shift can be performed at the pulling speed, and the first spool can be removed from the double spooler to take a sample of a predetermined length. The characteristics of the sampled optical fiber are measured, and the quality of the optical fiber is determined to determine whether to continue drawing. Here, the predetermined time or the predetermined length varies depending on the size, type, drawing speed, and the like of the base material, and is not particularly limited. For example, the predetermined time is 10 minutes to 120 minutes, and the predetermined length is 5 km to 50 km. preferable.
If the sampled optical fiber has good desired characteristics, the winding is continued on the second spool 62 under the same drawing conditions. In this way, an optical fiber having desired characteristics is obtained as a product. If defective, the drawing condition is adjusted while winding the optical fiber as a sample on the second spool 62 as it is.
[0009]
The conditions for adjusting the drawing conditions are different depending on the measurement result, but in the present invention, the drawing tension, the outer diameter of the fiber, and the drawing speed can be changed.
The tension of the drawing can be adjusted by raising or lowering the furnace temperature of the drawing furnace 20 by the controllers 1 and 2 based on the data measured by the tension measuring device 3. The outer diameter of the fiber is adjusted by changing a target set value of the outer diameter of the fiber. This can be performed by controlling the feed speed of the base material of No. 10 and the speed of the capstan 50 having the capstan motor 52. Also, if the drawing speed is changed while the furnace temperature and the fiber outer diameter are kept constant, the drawing tension changes and the shape of the meniscus portion (the molten portion of the base material) changes (this affects transmission loss, fiber diameter fluctuation, and bending). Do). Further, the drawing tension can be changed by changing the furnace temperature and the gas conditions (such as gas flow rate) in the furnace. Further, the furnace temperature can be changed with a constant tension. This affects transmission loss and fiber strength.
[0010]
In the adjustment of the drawing conditions in the present invention, it is preferable to adjust at least one selected from the group consisting of drawing tension, fiber outer diameter, and drawing speed. After that, the sample is taken again and the characteristics are measured by shifting with a double spooler, and the adjustment of the drawing conditions is repeated so as to fall within the range of the desired characteristics.
The characteristics include cutoff, chromatic dispersion, chromatic dispersion slope, effective core area, transmission loss, OH loss, bending loss, MFD, or polarization mode dispersion (PMD). The desired ranges of these characteristics differ depending on the use of the optical fiber to be manufactured, and are not particularly limited. For example, the cutoff (2 m method) is 900 to 1600 nm, and the chromatic dispersion is 1550 nm and 0 to 20 ps / nm /. km, the chromatic dispersion slope is 1550 nm, and 0.01 to 2 ps / nm for SMF and NZ-DSF. ² / Km, -20 to -300 ps / nm in dispersion-compensated inverse dispersion fibers such as DCF, DSCF and RDF ² / Km, effective core area is 20 to 150 μm ² The transmission loss is 1550 nm, 0.15 to 5 dB / km for SMF and NZ-DSF, -0.05 to -2 dB / km for reverse dispersion fibers such as DCF and DSCF, and the OH loss is 0.26 to 3 dB / km ( The bending loss is 0.06 to 20 dB / m (wrapped around a φ20 mm mandrel) (same as above), the MFD is 3 to 12 μm, and the polarization mode dispersion (PMD) varies depending on the type of fiber, and is preferably 1 ps / m. ^1/2 But not limited to:
[0011]
Although the optical fiber preform in the present invention is not particularly limited, a fiber having a small dispersion slope or a large effective core area, a dispersion compensation fiber (DCF), a dispersion slope compensation fiber ( DSCF) or a fiber in which a part of a core or a clad is doped with fluorine is preferably used.
The coating of the optical fiber used in the present invention is not particularly limited, and examples thereof include coating with an ultraviolet curable resin, an electron beam curable resin, a thermosetting resin, or the like.
[0012]
In the present invention, in the case of manufacturing an optical fiber in which chromatic dispersion at a predetermined wavelength has positive and negative sections as in JP-A-2001-130922, it is preferable to adjust the linear velocity condition in both the positive and negative sections. .
Further, in the present invention, for example, in order to cope with a variation in the longitudinal diameter of the core diameter of the base material or a change in the outer diameter of the base material, even after the adjustment of the drawing conditions is completed and the drawing of the product optical fiber is started. Preferably, the sample is taken and the characteristics are measured for each predetermined length, and the drawing conditions are adjusted during the drawing. This is because the above-mentioned optical fiber has a particularly narrow allowable range of characteristics or is difficult to produce.
The predetermined length varies depending on the size of the base material (φ30 mm to 100 mm), and for example, in the case of DCF, every 10 km to 100 km. The shift is performed by the double spooler 60 for each such predetermined length, and sampling is performed. It is preferable to perform (3) to (8).
The measurement of the characteristics during the drawing may be the same as the measurement of the characteristics performed at the beginning of the drawing, but preferably, the cutoff, the chromatic dispersion, the chromatic dispersion slope, the effective core area, the transmission loss, and the bending. It is preferable to measure at least two trade-off characteristics selected from the group consisting of loss, MFD, and PMD.
[0013]
In the sampling according to the present invention, it is preferable that the sampling is performed for each length required for the measurement of the characteristic, and it is preferable that the sampling is performed with a winding tension suitable for the measurement of the characteristic.
In the present invention, the optical fiber preform when the measurement result of the characteristics is significantly poor during the initial drawing or during the drawing, the characteristics of the previously drawn optical fiber are measured, based on the result, It is preferable to perform adjustment by cutting the outer diameter of the base material or adding a clad again, and drawing a new optical fiber base material.
[0014]
【Example】
Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
Example 1
According to the present invention, an optical fiber was manufactured by drawing a W-shaped DCF base material using the manufacturing apparatus shown in FIG. As the double spooler, the apparatus described in Japanese Patent Application No. 5-187584 described above was applied. The optical fiber was covered with an ultraviolet curing resin (hereinafter abbreviated as UV resin).
Here, the adjustment of the drawing conditions was performed as follows.
{Circle around (1)} A predetermined time (10 minutes to 60 minutes) or a predetermined length (5 km to 20 km) is drawn under the drawing conditions of a manufacturing line speed of 300 m / min, a manufacturing fiber diameter of 125 μm, and a drawing tension of 330 g, and a drawing state. Was stabilized.
{Circle around (2)} Sampling of a predetermined length was performed with a double spooler at a drawing speed of 300 m / min which is almost the same as the production line speed. When measuring transmission loss, chromatic dispersion, chromatic dispersion slope, PMD, etc., sampling was performed for 2 to 6 km. When measuring the cut-off, bending loss, MFD and effective core area, it was set to several hundred m or less.
(3) The wavelength dispersion and bending loss of the sampled fiber were measured.
{Circle around (4)} The drawing conditions for obtaining desired characteristics are predicted from the past data or the profile of the base material and the drawing speed, tension and the like.
[0015]
In this case, the chromatic dispersion D of the DCF was negative. The dispersion D and the bending loss had a trade-off relationship. The bending loss increases as the core diameter increases, and the absolute value of the wavelength dispersion D decreases. Therefore, the core diameter was determined so that the bending loss was within 10 dB / m, which is the range of desired characteristics. That is, the outer diameter of the fiber was increased. However, since the target fiber outer diameter at the time of design in this case was 125 μm, if the adjustment could not be made in the range of 120 μm to 130 μm, the drawing was interrupted and the preform was reworked.
It is known from past data that the core diameter should be increased in order to increase the bending, so the thickness was increased by 0.05 μm. The set value of the fiber outer diameter control was changed so that the fiber outer diameter was changed from 125 μm to 126 μm. In this case, the variance tends to be small. After 10 minutes, when the outer diameter was stabilized, sampling was performed after waiting for another 10 minutes. The bending loss was 2 dB / m at a wavelength of 1550 nm (result of an increase in loss wound around a mandrel of φ20 mm).
[0016]
Since the absolute value of the variance was reduced this time, the drawing tension was reduced by 40 g and the absolute value of the variance was increased. As a result, the bending loss was 5 dB / m (at 1550 nm) and the dispersion was the target of -120 ps / nm / km. Under these conditions, drawing of a product optical fiber was started.
As a result of measuring the characteristics of the fiber wound as a sample by shifting the double spooler at a position where the 25 km was drawn, the absolute value of the chromatic dispersion was increased. Therefore, the furnace temperature was lowered and the drawing tension was increased by 20 g. After the tension was stabilized, a sample was taken after waiting 10 minutes.
As a result, the bending loss was 4.6 dB / m and the dispersion was -123 ps / nm / km, which was close to the center of the standard (-120). Therefore, the drawing of the optical fiber for the product was continued. In this way, adjustment was performed by shifting the sample with the double spooler two more times and taking a sample.
As described above, an optical fiber of 80 km was obtained as a good product.
[0017]
For the purpose of comparison, the same as the above-described embodiment except that the drawing conditions were determined so that the fiber outer diameter was 125 μm, the drawing tension was 330 g, and the drawing speed was 300 m / min. When the apparatus was started up in the same manner as in Example 1, even if the head was passed, in this case, a good optical fiber equivalent to that of Example 1 could be obtained only for about 50 km.
[0018]
Example 2
An optical fiber was manufactured by drawing a DCF fiber preform guaranteed to the W-seg type dispersion slope in the same manner as in Example 1. The optical fiber was covered with a UV resin.
Here, the adjustment of the drawing conditions was performed as follows.
{Circle around (1)} A predetermined drawing time (60 minutes) or a predetermined drawing length (20 km) was drawn under the drawing conditions of a production drawing speed of 500 m / min, a production fiber diameter of 125 μm, and a drawing tension of 290 g to stabilize the drawing state. .
{Circle around (2)} A double spooler was used for shifting at a drawing speed of 500 m / min, which was almost the same as the production linear speed, and sampling of a predetermined length was performed. When measuring transmission loss, chromatic dispersion, chromatic dispersion slope, PMD, etc., sampling was performed for 2 to 6 km. When measuring the cut-off, bending loss, MFD and effective core area, it was set to several hundred m or less.
(3) The chromatic dispersion, chromatic dispersion slope and bending loss of the sampled fiber were measured.
{Circle around (4)} Drawing conditions for obtaining desired characteristics were predicted from past data or the profile of the base material, drawing speed, tension and the like.
[0019]
In this case, the chromatic dispersion D and the chromatic dispersion slope S of the DCF were negative. The dispersion D and the bending loss had a trade-off relationship. The bending loss increases as the core diameter increases, the absolute value of the chromatic dispersion D decreases, and the absolute value of the chromatic dispersion slope S increases. Therefore, similarly to the first embodiment, the core diameter was determined so that the bending loss was within 10 dB / m, which is the range of the desired characteristics. That is, the outer diameter of the fiber was increased. However, since the target fiber outer diameter at the time of design in this case was 125 μm, if the adjustment could not be made in the range of 120 μm to 130 μm, the drawing was interrupted and the preform was reworked.
It is known from past data that the core diameter should be increased in order to increase the bending, so the diameter was increased by 0.1 μm. The set value of the fiber outer diameter control was changed so that the fiber outer diameter was changed from 125 μm to 127 μm. In this case, the absolute value of the wavelength dispersion D tends to decrease. The absolute value of the chromatic dispersion slope S also decreases. However, in this case, assuming that the ratio between the dispersion D and the dispersion slope S is DPS = D / S, it is necessary to make the DPS fall within a predetermined range (DPS = 330 to 360 is a target range). In this case, DPS (nm) becomes small. When the outer diameter became stable after 10 minutes, sampling was performed after waiting for another 10 minutes. The bending loss was 3 dB / m (as a result of an increase in the loss wound around a mandrel of φ20 mm).
[0020]
This time, the DPS was increased to 380 nm, so the drawing tension was reduced by 30 g to reduce the DPS. As a result, a bending loss of 5 dB / m (at 1550 nm) and a DPS of 350 (nm) could be achieved within the target ranges. Under these conditions, drawing of a product optical fiber was started.
As a result of measuring the characteristics of the fiber wound as a sample by shifting the double spooler at a position where 50 km was drawn, the bending loss was increased by 10 dB / m (1550 nm). Therefore, the furnace temperature was lowered and the drawing tension was increased by 20 g. After the tension was stabilized, a sample was taken after waiting 10 minutes.
As a result, the bending loss was 345 nm in DPS at 6 dB / m, which was almost the same as the bending standard of 6 dB / m. Therefore, adjustment was made to reduce the core diameter by 0.03 μm. The fiber outer diameter set value was changed so that the fiber outer diameter was 126.4 μm.
After the fiber outer diameter was stabilized at the linear velocity, a sample was taken after waiting for 20 minutes. As a result, since the bending loss was 4.3 dB / km and the DPS was within the standard of 355 nm, the drawing of the optical fiber for product was continued. While performing such adjustment, the shift was performed ten times with a double spooler, and a sample was taken for adjustment.
As described above, an optical fiber of 500 km was obtained as a good product.
[0021]
For comparison, the start-up was performed in the same manner as in Example 2 except that the drawing conditions were determined so that the drawing speed was 500 m / min, the fiber outer diameter was 125 μm, and the drawing tension was 290 g. In this case, a good optical fiber equivalent to that of Example 2 could only take about 100 km.
[0022]
Example 3
1550 nm dispersion is 4-10 ps / nm / km and dispersion slope is 0.05 ps / nm ² An optical fiber was manufactured by drawing a NZ-DSF (non-zero dispersion shifted optical fiber) base material having a MFD of 8 to 8.5 μm or less in the same manner as in Example 1. The optical fiber was covered with a UV resin.
Here, the adjustment of the drawing conditions was performed as follows.
{Circle around (1)} A predetermined drawing time (60 minutes) or a predetermined drawing length (20 km) was drawn under the drawing conditions of a production drawing speed of 1000 m / min, a production fiber diameter of 125 μm, and a drawing tension of 170 g to stabilize the drawing state. .
{Circle around (2)} Sampling of a predetermined length was performed by shifting with a double spooler at a drawing speed of 1000 m / min, which was almost the same as the production line speed. When measuring transmission loss, chromatic dispersion, chromatic dispersion slope, PMD, etc., sampling was performed for 2 to 6 km. When measuring the cut-off, bending loss, MFD and effective core area, it was set to several hundred m or less.
(3) The chromatic dispersion, chromatic dispersion slope, and MFD of the sampled fiber were measured.
{Circle around (4)} Drawing conditions for obtaining desired characteristics were predicted from past data or the profile of the base material, drawing speed, tension and the like.
[0023]
In this case, the chromatic dispersion D and the chromatic dispersion slope of the low dispersion slope NZ-DSF were positive. Also, the dispersion D and the MFD had a trade-off relationship. Depending on the profile, the core diameter dependency of the MFD may increase or decrease with respect to the core diameter. In the case of this base material, it is known from the data up to now that the MFD decreases as the core diameter increases. Therefore, in order to increase the MFD, the outer diameter of the fiber was reduced from 125 μm to 124.5 μm. In this case, both the chromatic dispersion and the chromatic dispersion slope become small.
Set the target value of the fiber outer diameter control so that the outer diameter after drawing becomes 124.5 μm, wait until the drawing speed and the outer diameter of the fiber become constant, and after drawing 20 km, shift again with the double spooler. And took a sample.
[0024]
The MFD increases from 7.8 μm to 8.1 μm, and the chromatic dispersion and slope at 1550 nm are 4.6 ps / nm / km and 0.048 ps / nm. ² / Km and the standard was satisfied. Under these conditions, drawing of a product optical fiber was started.
A sample fiber was taken from the end of the bobbin fiber which was shifted by a double spooler and wound up after drawing 100 km, and chromatic dispersion, slope and MFD were measured. The dispersion was as small as 4.2 ps / nm / km. Dispersion slope is 0.046 ps / nm ² / Km, there was some room for the standard, so the furnace temperature was lowered and the drawing tension was raised by 30 g. After the linear velocity and the fiber outer diameter were stabilized, 20 km was drawn and sampling was performed again.
As a result, the dispersion is improved to 4.6 ps / nm / km, the MFD is 8.1 μm, and the dispersion slope is 0.048 ps / nm. ² / Km, which is within the standard, so the drawing of the optical fiber for the product was continued. While performing such adjustments, the sample was shifted five times by a double spooler and sampled for adjustment.
As described above, an optical fiber of 400 km or more was obtained as a good product.
[0025]
For comparison, under the same base material and drawing conditions at the time of starting drawing as in Example 3, the drawing conditions were determined such that the drawing speed was 1000 m / min, the fiber outer diameter was 125 μm, and the drawing tension was 120 g, and the drawing was started. In this case, even if the head was passed, in this case, an optical fiber of about 200 km was obtained as a good product equivalent to that of Example 3.
[0026]
Example 4
A single mode fiber (hereinafter, referred to as FF) in which the cutoff is shifted to 1500 nm, in which the core is doped with fluorine at a relative refractive index difference of about Δ = 0.01% and the clad is doped with about Δ = 0.35%. An optical fiber was manufactured by drawing the preform in the same manner as in Example 1. The optical fiber was covered with a UV resin.
Here, the adjustment of the drawing conditions was performed as follows.
In this case, the characteristics of the cutoff and the transmission loss at 1550 nm were measured. Since the transmission loss greatly depends on the drawing furnace temperature and the drawing tension, a sample of 5 km was measured. Since the cutoff depends on the tension and the core diameter, first change the fiber outer diameter to match the cutoff in the same way as in the previous embodiments, perform sampling, and then measure the tension to reduce transmission loss. I did it.
[0027]
The drawing speed was 300 m / min, the drawing was started under the drawing conditions of a tension of 30 g and a fiber outer diameter of 125 μm. Since the cutoff was as high as 1520 nm, in order to reduce the core diameter, the set value of the fiber outer diameter control was changed so that the fiber outer diameter was reduced to 124.3 μm. The transmission loss at this time was as high as 0.180 dB / km. After the linear velocity and the fiber outer diameter were stabilized, 10 km was drawn and sampling was performed again. As a result, the cutoff decreased to 1480 nm. The transmission loss at this time was 0.192 dB / km. Therefore, the furnace temperature was raised to a drawing tension of 20 g or the gas supplied into the furnace was reduced to lower the temperature. After the linear velocity and the fiber outer diameter were stabilized, 10 km was drawn and sampling was performed again. As a result, the cutoff wavelength and the transmission loss were improved to 1492 nm and 0.175 dB / km, respectively, and were within the target specifications. Therefore, drawing of an optical fiber for a product was started.
[0028]
After drawing 30 km, the fiber was shifted by a double spooler, and 5 km of the fiber was taken out from the end of the wound bobbin, and the transmission loss and cutoff were measured. Since the transmission loss was 0.183 dB / km and the cutoff was 1497 nm, the drawing tension was changed to 25 g. After the linear velocity and the fiber outer diameter were stabilized, 10 km was drawn and sampling was performed again. As a result, the cutoff was 1495 nm and the transmission loss was 0.176 dB / km. Therefore, the drawing of the optical fiber for a product was continued under the same conditions. By repeating such adjustment, shifting was performed seven times with a double spooler to obtain a drawing bobbin.
As described above, an optical fiber of 100 km to 180 km was obtained as a good product.
[0029]
For comparison, the drawing conditions were determined such that the drawing speed at the start of drawing was 300 m / min, the fiber outer diameter was 125 μm, and the drawing tension was 30 g under the same base material and drawing conditions as in Example 4 above. Except for the above, the starting was performed in the same manner as in Example 4 above. As a result, with this base material having a longitudinal variation, only a good product equivalent to Example 4 was obtained from 50 km to 100 km.
[0030]
Example 5
An optical fiber was manufactured in the same manner as in Example 4, except that the FF fiber was adjusted as follows. Here, as the adjustment of the FF fiber, the transmission loss depends on the drawing furnace temperature and the drawing tension, and the cutoff and the transmission loss of 1550 nm are measured at the first sampling so that the desired cutoff is obtained. The drawing tension was adjusted.
For example, when the cutoff is high, the drawing tension is reduced (the drawing furnace temperature is increased). If the cutoff is low, increase the tension (lower the drawing furnace temperature). After adjusting the drawing conditions in this way, after the drawing speed and the fiber outer diameter were stabilized, 5 km was drawn, and sampling was performed again to measure cutoff and transmission loss. When the cutoff was within the standard, the transmission loss was adjusted. If the transmission loss is high, there are two causes: the furnace temperature is too high, and the cooling rate of the high temperature part of the optical fiber is too high. Judgment was made from the wavelength characteristics of transmission loss based on past experience. In this case, since the furnace temperature was too high, adjustment was made to lower the drawing furnace temperature and further reduce the amount of gas supplied into the furnace while maintaining the same tension. In this case, the number of adjustments can be reduced if the conditions are obtained in advance by experiments. This adjustment was repeated until both the cutoff and the transmission loss were within the standard. After entering the standard, we started drawing optical fibers for products. After drawing a predetermined length as in Example 4, the characteristics of the optical fiber wound by switching with a double spooler were measured, and the drawing conditions were adjusted as necessary. As a result, the same effect as in Example 4 was obtained.
[0031]
The tendency of the base material of any of the examples was that the characteristic variation was large between the rising portion and the end portion of the base material. Therefore, the above adjustment is often performed at the beginning of drawing and at the end of drawing. Also, an example has been described in which the adjustment of the two characteristics is performed by separately sampling, but since the characteristics to be adjusted are substantially determined for each base material, both adjustments can be performed simultaneously.
[0032]
【The invention's effect】
The manufacturing method and the manufacturing apparatus of the present invention have the following effects.
1) Since the drawing speed is substantially the production line speed, the difference between the predicted value and the actual value of the optical fiber characteristics after changing the drawing conditions can be reduced. (Because disturbance due to linear velocity fluctuation has disappeared)
2) It is possible to start manufacturing after confirming that the specified characteristics are obtained.
3) Accurate characteristic prediction can be performed by predicting the drawing conditions from past data or furthermore, the profile of the base material and the drawing speed, tension, and the like.
4) Since a double spooler is used, sampling can be performed even if the number of times of sampling is large and the linear velocity is 1000 m / min or more. Furthermore, sampling can be performed not only at the beginning of the drawing but also in the middle.
5) Since the same adjustment can be performed by sampling even during drawing, the adjustment can be performed even if there is a variation in the longitudinal direction, and the yield can be greatly improved.
6) Therefore, the present invention can be applied to a base material having a longitudinal variation. (The yield can be improved.)
7) Even in the case of a base material that cannot be used from the beginning or in the middle of drawing, by interrupting the drawing, unnecessary drawing can be avoided.
8) For the optical fiber preform whose characteristics do not enter during the initial drawing or during the drawing, measure the characteristics of the previously drawn optical fiber and cut the outer diameter of the preform, or add a clad again. By performing adjustment and drawing as a new drawing base material, the base material can be used effectively.
Therefore, the manufacturing method and the manufacturing apparatus of the present invention are suitable for stably obtaining an optical fiber having good characteristics.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a preferred embodiment of a manufacturing apparatus to which an optical fiber manufacturing method of the present invention is applied.
[Explanation of symbols]
1 First control device
2 Second control device
3 tension measuring device
4 Fiber diameter measuring device
5 Optical fiber preform
6 Optical fiber
7 Coated optical fiber
8 Pass line for winding on spool 61
9 Pass line when winding on spool 62
10 Base material feeder
11 Base material feed motor
20 wire drawing furnace
21 Cooling cylinder
30 Coating equipment
31 Coating dies
32 dice holder
40 UV irradiation device
50 capstan
51 Guide pulley
52 Capstan Motor
60 Winding device (double spooler)
61 First spool
62 Second spool
63 dancer
64a, 64b Movable pulley

Claims

The optical fiber preform is melted and spun in a drawing furnace to form an optical fiber, the optical fiber is coated to form a coated optical fiber, and the coated optical fiber is pulled out with a capstan, and wound by a winding machine. It is a method of manufacturing an optical fiber by drawing an optical fiber, using a double spooler as the winder, after drawing a predetermined time or a predetermined length after reaching a manufacturing drawing speed. A sample is taken at the production drawing speed, the characteristics of the sampled optical fiber are measured, and the adjustment of each drawing condition is repeated so that the obtained measured value falls within the range of the desired characteristics. A method of manufacturing an optical fiber, comprising: starting to draw an optical fiber for a product after confirming the fact.

Until the measured value falls within the range of desired characteristics, adjust at least one drawing condition selected from the group consisting of drawing tension, fiber outer diameter and drawing speed, and take the sample and measure the characteristics. 2. The method for manufacturing an optical fiber according to claim 1, wherein

As the measurement of the characteristic, measurement of at least one characteristic selected from the group consisting of cutoff, chromatic dispersion, chromatic dispersion slope, effective core area, transmission loss, OH loss, bending loss, MFD, and PMD is performed. 3. The method for manufacturing an optical fiber according to claim 2, wherein:

The optical fiber preform may be a fiber having a small dispersion slope or a large effective core area, a dispersion compensating fiber (DCF), a dispersion slope compensating fiber (DSCF), or a part or cladding of a standard single mode fiber. 4. The method for producing an optical fiber according to claim 1, wherein the optical fiber is a fiber doped with fluorine.

In the course of drawing after starting the drawing of the optical fiber for the product, the sample taking, measurement of the characteristics and adjustment of the drawing conditions are repeated for each predetermined length until the desired characteristics are obtained. The method of manufacturing an optical fiber according to claim 2, wherein the method is performed.

As the measurement of the characteristic during the drawing, at least one characteristic selected from the group consisting of cutoff, chromatic dispersion, chromatic dispersion slope, effective core area, transmission loss, bending loss, MFD, and PMD is measured. The method for producing an optical fiber according to claim 5, wherein

7. The method according to claim 5, wherein the sample is taken every time the characteristic is measured.

8. The method of manufacturing an optical fiber according to claim 5, wherein the sample is taken with a winding tension suitable for measuring the characteristic.

For the optical fiber preform when the measured value does not fall within the desired characteristic range, the preform is drawn based on the measured value of the characteristic of the optical fiber in which the measured value falls within the desired characteristic range. The optical fiber according to any one of claims 1 to 8, wherein the outer diameter of the optical fiber is adjusted or adjusted by adding a clad again, and a new optical fiber preform is drawn. Production method.

A drawing furnace for melting and spinning an optical fiber preform into an optical fiber, a coating apparatus for coating the optical fiber, a capstan for drawing the coated optical fiber, and a winding for winding the drawn optical fiber An apparatus for manufacturing an optical fiber, comprising: using a double spooler as the winding machine, drawing a predetermined time or a predetermined length after reaching the production drawing speed, and then taking a sample at the production drawing speed. The characteristics of the sampled optical fiber are measured, and the drawing conditions are repeatedly adjusted so that the obtained measured value falls within the range of the desired characteristics. An optical fiber manufacturing apparatus, which starts drawing an optical fiber for use.