JP4225035B2

JP4225035B2 - Optical amplification repeater transmission system and monitoring control method thereof

Info

Publication number: JP4225035B2
Application number: JP2002333869A
Authority: JP
Inventors: 順子岩崎; 隆横山
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2002-11-18
Filing date: 2002-11-18
Publication date: 2009-02-18
Anticipated expiration: 2022-11-18
Also published as: JP2004172750A

Description

【０００１】
【発明の属する技術分野】
本発明は、光ファイバ伝送路自体を光増幅媒体とする分布型ラマン増幅を用いた光増幅中継伝送システムに関する。
【０００２】
【従来の技術】
従来、波長多重伝送では、希土類添加光ファイバ増幅器の１種であるＥＤＦＡ（エルビウム添加光ファイバ増幅器）を搭載した光増幅中継器を複数多段につなげて長距離伝送を行っている。
図７は、従来の伝送中継システムの構成を示すブロック図である。図に示すように、光直接増幅器を搭載した中継器を多段に接続して端局間をつなぐ伝送路を構成している。そして、伝送路から受信端局への長距離にわたる伝送路損失をカバーして信号出力レベルを保つため、各増幅器からの出力が一定となるよう出力一定制御ＡＬＣ（Automatic Level Control）を行っている（図６）。
長距離伝送中継システムでは、光増幅器の励起光源や光増幅器及び伝送路自体の経時劣化を含む伝送路監視が重要な技術である。とくに、海洋光中継システムのように障害復旧には多大なコストが掛かるため、障害地点の同定や障害部品の特定が極めて重要である。
光増幅器の励起光源に関しては、ＡＬＣでは、増幅器からの信号光の出力レベルのモニタを行い、モニタ値が、あらかじめ定めた出力レベルからの変動を検出した場合、励起レーザのパワーを制御して、信号光のレベルが常に一定になるように制御する。そして、ＥＤＦＡ中継器では、波長は通常一種類の光源で励起しており、予備光源として光増幅器を励起するための励起レーザを複数有しているが、ＡＬＣ機能を実装している場合、ＥＤＦＡは通常飽和出力で動作させているため、信号光のモニタでは、励起レーザの故障が検出できないという問題がある。
【０００３】
伝送路の監視については、ＯＴＤＲ（Optical Time Domain Reflectmetry）などを用いて行う方法も良く行われる。ＯＴＤＲのプローブ光を用いてライン監視を行う方法とは、監視用波長を端局から入射し、監視用の伝送路区間のＯＴＤＲパス上を伝送させ、伝送路光ファイバの破断点等で反射され受信される戻り光をＯＴＤＲ測定器で観測して、光伝送路の状況監視を行うものである。
しかし、この監視方法を、数千キロ以上の長距離伝送に適用する場合、監視光が伝送路伝播中に光ファイバの非線形光学効果やノイズの影響をうけ、測定値劣化や時間変動が発生しやすくなる。また、これに対処し、測定精度をあげるためには、モニタ値の長時間平均をとる必要があるが、測定時間が数時間に及び、迅速かつ正確な障害検出という点で課題があった。
【０００４】
一方、中継区間の延伸や伝送光信号のＳ／Ｎ比改善を目的にして、光ファイバ伝送路そのものを利得媒体とする分布ラマン増幅効果を適用した中継伝送システムも検討されている。図８はラマン増幅効果におけるラマン励起光と信号増幅帯域の関係を示している。伝送路が石英光ファイバの場合、励起光の約１００ｎｍ（１３．２ＴＨｚ）長波側に利得ピークを有するよう信号光を増幅する。このため、波長の異なる励起光源を複数用いることで増幅波長帯域を比較的自由に設定でき、添加する元素およびホスト材料により増幅波長帯域が決定する希土類添加光ファイバ増幅器とは大きく異なる。更に、多波長励起方式を用いると柔軟に増幅波長帯域を拡大できる。また、既に敷設済みの光ファイバを利用することもできる。
この方式においても、長距離伝送であるため、励起光源の劣化や伝送路損失の経時変化を含む伝送路監視や中継器を構成する予備部品への切換等を遠隔や中継器自体で自律的に行えることが重要となる。とくに、ラマン増幅器が、複数波長の励起光源で帯域を確保できることは、逆に１波長の光源でも劣化を来すと、光増幅帯域特性にディップを生じ、伝送品質の低下を来すことになる。このため、ＥＤＦＡ中継伝送システム以上に励起光源の障害監視が重要であり、障害の原因が伝送路にあるか、励起光源にあるかを峻別できる監視方法を確立しておくことが重要である。
伝送路監視に関しては、ＯＴＤＲ監視方法を分布ラマン光増幅中継方式のライン監視に適用した場合、ＥＤＦＡ光中継伝送方式と同様の問題が生じる。分布型ラマン増幅の場合は、さらに、監視光がラマン増幅利得変動の影響による変動も受け、精度の良い測定が困難となる。
分布ラマン増幅器であり利得媒体でもある伝送路の損失分布をモニタするために、偏光状態を時間的に変化させた検査パルス光を伝送路に注入し、その後方散乱光を検出する方法が開示されている（例えば特許文献１参照）。検査パルス光の後方散乱を検出する方法は、上述のＯＴＤＲ法と同様の課題を有する。
また、励起光源の監視方法としては、ファイバ型光増幅器の励起光を分岐させて監視局に伝送し、後段の光増幅器からの励起光は自増幅器を迂回させて監視局に転送する方法が開示されている（例えば特許文献２参照）。しかしながら、後段からの励起光を自増幅器を迂回させて監視局に転送するこの励起光源の監視方法は、中継器における光回路構成が複雑になるという難点を有する。
【０００５】
【特許文献１】
特開２００１−２３５７７２号公報
【特許文献２】
特開平５−０４００７３号公報
【０００６】
【発明が解決しようとする課題】
本発明は、このような課題に鑑みて成されたものであって、ラマン増幅を適用する長距離多段中継伝送システムにおいて、光伝送路を構成する光ファイバや光中継器の状況監視を簡易な構成で、迅速かつ正確に行う方法や構成を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の光増幅中継伝送システムの監視制御方法は、信号光送信端局と受信端局の間を、波長の異なる複数の光源からなる励起光源が接続された複数の中継器を介して、光ファイバ伝送路によって縦続に接続し伝送路を伝送される信号光を分布型ラマン光増幅効果によって光増幅中継する伝送システムであって、複数の中継器の各中継器は、隣接する第１の隣接中継器との間の光ファイバ伝送路区間に、分布型ラマン光増幅効果を励起する励起光を、前記信号光と逆方向に伝播させる後方励起で送出し、別なる隣接する第２の隣接中継器から送出され、第２の隣接中継器との間の光ファイバ伝送路区間から出力される残留励起光を、励起光モニタ部において波長を特定してモニタし、励起光モニタ部の出力から、第２の隣接中継器との間の光ファイバ伝送路区間の伝送路障害と、第２の隣接中継器が備える励起光源の出力異常と、残留励起光に重畳された、第２の隣接中継器からの障害情報とを検出し、信号光を分岐モニタして、信号光の分岐モニタ出力が所定の値に一定となるように、各中継器の備える励起光源の出力を制御し、さらに、第２の隣接中継器からの障害情報と、各中継器と第２の隣接中継器との間の区間の伝送路障害の情報と、第２の隣接中継器が備える励起光源の出力異常の情報と、各中継器が備える励起光源の出力異常の情報とを、各中継器の障害情報として、励起光に重畳して第１の隣接中継器に送信する、ことを特徴とする。
【０００８】
また、本発明の光増幅中継伝送システムの監視制御方法は、上り送信装置と下り受信装置を備える第１の送受信端局と、上り受信装置と下り送信装置を備える第２の送受信端局との間を、上り下り２対の光ファイバ伝送路と、波長の異なる複数の光源からなる励起光源が接続された複数の中継器を介して縦続に接続し、伝送路の上り下りそれぞれを伝送する信号光を分布型ラマン光増幅効果によって光増幅中継する双方向伝送システムにおいて、複数の中継器の各中継器は、隣接する隣接中継器との間の上り下りそれぞれの光ファイバ伝送路区間に分布型ラマン光増幅効果を励起する励起光を、前記信号光と逆方向に伝播させる後方励起で送出し、隣接中継器から送出され、光ファイバ伝送路区間から出力される残留励起光を、励起光モニタ部において波長を特定してモニタし、励起光モニタ部の出力から、光ファイバ伝送路区間の伝送路障害と、隣接中継器が備える励起光源の出力異常と、残留励起光に重畳された隣接中継器からの障害情報とを検出し、隣接中継器からの障害情報と、伝送路障害の情報と、隣接中継器が備える励起光源の出力異常の情報と、各中継器が備える励起光源の出力異常の情報とを、各中継器が備える励起光源の励起光に重畳して、各中継器の障害情報として、隣接中継器に送信する、ことを特徴とする。
【０００９】
本発明の光増幅中継伝送システムは、信号光送信端局と受信端局の間を、波長の異なる複数の光源からなる励起光源が接続された複数の中継器を介して、光ファイバ伝送路によって縦続に接続し伝送路を伝送される信号光を分布型ラマン光増幅効果によって光増幅中継する伝送システムであって、複数の中継器の各中継器は、隣接する第１の隣接中継器との間の光ファイバ伝送路区間に、分布型ラマン光増幅効果を励起する励起光を、信号光と逆方向に伝播させる後方励起で送出する手段と、別なる隣接する第２の隣接中継器から送出され、第２の隣接中継器との間の光ファイバ伝送路区間から出力される残留励起光を、励起光モニタ部において波長を特定してモニタする手段と、励起光モニタ部の出力から、第２の隣接中継器との間の光ファイバ伝送路区間の伝送路障害と、第２の隣接中継器が備える励起光源の出力異常と、残留励起光に重畳された、第２の隣接中継器からの障害情報とを検出する手段と、信号光を分岐モニタして、信号光の分岐モニタ出力が所定の値に一定となるように、各中継器の備える励起光源の出力を制御する手段と、第２の隣接中継器からの障害情報と、各中継器と第２の隣接中継器との間の区間の伝送路障害の情報と、第２の隣接中継器が備える励起光源の出力異常の情報と、各中継器が備える励起光源の出力異常の情報とを、各中継器の障害情報として、励起光に重畳して第１の隣接中継器に送信する手段、を備えることを特徴とする。
【００１０】
本発明の光増幅中継伝送システムは、上り送信装置と下り受信装置を備える第１の送受信端局と、上り受信装置と下り送信装置を備える第２の送受信端局との間を、上り下り２対の光ファイバ伝送路と、波長の異なる複数の光源からなる励起光源が接続された複数の中継器を介して縦続に接続し、伝送路の上り下りそれぞれを伝送する信号光を分布型ラマン光増幅効果によって光増幅中継する双方向伝送システムであって、複数の中継器の各中継器は、隣接する隣接中継器との間の上り下りそれぞれの光ファイバ伝送路区間に分布型ラマン光増幅効果を励起する励起光を、前記信号光と逆方向に伝播させる後方励起で送出する手段と、隣接中継器から送出され、光ファイバ伝送路区間から出力される残留励起光を、励起光モニタ部において波長を特定してモニタする手段と、励起光モニタ部の出力から、光ファイバ伝送路区間の伝送路障害と、隣接中継器が備える励起光源の出力異常と、残留励起光に重畳された隣接中継器からの障害情報とを検出する手段と、隣接中継器からの障害情報と、伝送路障害の情報と、隣接中継器が備える励起光源の出力異常の情報と、各中継器が備える励起光源の出力異常の情報とを、各中継器が備える励起光源の励起光に重畳して、各中継器の障害情報として、隣接中継器に送信する手段、を備えることを特徴とする。
【００１１】
【発明の実施の形態】
本発明の発明の実施形態について図面を参照して説明する。
図１は本発明の第１の実施例の分布ラマン増幅中継伝送システムの構成を示すブロック図であり、分布ラマン増幅器を備えた中継器を多段に接続して端局間をつないで伝送路を構成している。ラマン増幅中継器１００とラマン増幅中継器２００は、後方励起を行うように励起光を光ファイバ伝送路１１若しくは１２に入射して、分布型ラマン増幅を行っている。励起方式としては、ＥＤＦＡの場合と同様、励起光を信号光と同一方向に光ファイバ内を伝播させる前方励起と、逆方向に伝播させる後方励起、及び、両方向励起の方式があるが、本実施例では後方励起方式の実施例について説明する。
ラマン増幅中継器１００は、ラマン増幅用励起光を出力する励起光源ユニット１１０、監視部１０１、光サーキュレータ１１１を備えている。ラマン増幅中継器２００も同一の構成である。
光サーキュレータ１１１（２１１）は、光ファイバ伝送路１１（１２）からの信号光を、後段の光ファイバ伝送路１２（１３）へ転送出力する。また、励起光源ユニット１１０（２１０）からの励起光を、光ファイバ伝送路１１（１２）へ後方励起光として出力する。
【００１２】
監視部１０１（２０１）は、光ファイバ伝送路１１からの信号光を一部分岐してモニタし、また、光ファイバ伝送路１２を通じて後段の中継器２００からの励起光のパワーのモニタを行う。モニタ情報は、励起光源ユニット１１０に出力する。監視部１０１（２０１）の構成を図２に示す。監視部は、信号光及び後段の中継器２００からの励起光を結合抽出するためのカプラ５１と、信号光を受光し光電変換する信号光モニタ部５２と、後段の中継器２００からの励起光のパワーのモニタを行う励起光モニタ部５３とから構成され、それぞれのモニタ部からのモニタ情報は、励起光源ユニット１１０の備える励起レーザ制御部３００に送信される。
各モニタ部５２、５３は、受信光を分波する光フィルタ（光ＦＩＬ）と、分波された複数の波長光を光電変換する複数の受光素子（ＰＤ）と、複数の受光素子出力信号をデジタル化等の処理を行い励起光源ユニット１１０の励起レーザ制御部３００に出力する受光信号処理部５４，５５を備える。
【００１３】
励起光源ユニット１１０の構成を図３に示す。
励起光源ユニット１１０は、光ファイバ伝送路１１（１２）を後方ラマン励起する複数の励起レーザ（ＬＤ３０１〜３０４）と、励起光のパワー制御と監視部１０１（２０１）から受信したモニタ情報に基づき、励起光への制御信号の付加を行う励起レーザ制御部３００を有している。
励起レーザは、同一波長のラマン励起光源２個を１組として偏波合成（ＰＢＣ３０５、３０６）後、他波長の励起光源の組と波長合成する（ＷＤＭカプラ３０７）ように構成されている。ここでは、２波長４ＬＤ構成の例を示す。
励起レーザ制御部３００は、励起レーザを駆動するＬＤドライバ３１０と、監視部１０１（２０１）の信号光モニタ部５２及び励起光モニタ部５３からのモニタ情報を受信するモニタ情報受信部３２０と、モニタ情報受信部の出力から励起レーザ光出力に付加する制御信号を生成する制御信号生成部３３０から構成されている。
【００１４】
次に、本発明の実施例の動作について説明する。
ラマン増幅中継器１００において、光ファイバ伝送路１１を透過した信号光は光カプラ５１によって分岐され、監視部１０１の信号光モニタ部５２によって検出される。信号光モニタ部５２で検出した波長多重光すべての受光レベルの低下があれば、自中継器１０１の励起ＬＤ３０１〜３０４の出力低下や光ファイバ伝送路１１の区間障害であることが分かり、増幅帯域にディップや突起を生じていれば、自ラマン増幅中継器１００内の特定の波長の励起レーザ障害であると判定される。
信号光を中継する後段のラマン増幅中継器２００が備える励起光源ユニット２１０から出力し、光ファイバ伝送路１２をラマン励起した励起光は、監視部１０１のもつ励起光モニタ部５３によって検出される。励起光モニタ部５３で検出した複数波長の励起光すべての受光レベルの低下があれば、後段中継器２０１の励起ＬＤ３０１〜３０４の出力低下や光ファイバ伝送路１２の損失増大やラマン利得低下等の区間障害であることが分かり、複数の波長のラマン励起光強度にばらつきが大きければ、後段のラマン増幅中継器２００内の特定の波長の励起レーザの出力異常等の障害であると判定される。この判定はモニタ情報受信部３２０が行う。
このように、監視部１０１が、信号光と励起光の各波長の出力レベルをモニタすることができるため、区間を特定したラマン増幅出力の低下と伝送路障害と特定波長のラマン励起光源の出力異常とを峻別して検出することができる。
【００１５】
次に、特定の区間の増幅度低下や光ファイバ伝送路１１（１２）の障害や、自増幅中継器１００や前段のラマン増幅中継器２００の励起光源の故障といった状態異常を検出したラマン増幅中継器１００の動作について説明する。
受光信号処理部５４及び５５が状態異常を検出した情報は、励起光源ユニット１１０のモニタ情報受信部３２０に送られる。モニタ情報受信部３２０は、２つの受光信号処理部からの状態異常の情報を検出する。信号光モニタ部５２からの信号光レベルが所定のレベルから低下または増大しているという障害を検出したとき、モニタ情報受信部３２０は、制御信号生成部３３０に自中継器のラマン後方励起用ＬＤの出力の増加または減少の指示を出力する。すなわち、区間１１のラマン増幅動作をＡＬＣ制御する。また、自ラマン増幅中継器の励起レーザに出力異常があった場合、励起レーザ３０１〜３０４の特定のＬＤの出力を制御する指示を制御信号生成部３３０に行う。
また、後段のラマン増幅中継器２００からの励起光のレベルをモニタする励起光モニタ部５３からの受信信号から、モニタ情報受信部３３２０は、区間１２の回線断やラマン増幅中継器２００における励起レーザ全体の出力低下や特定のレーザの障害等の状態異常を検出する。また、中継器２００からの励起光には、中継器２００以降の後段中継器の励起レーザの状態異常の情報が重畳されている。これらを検出して、制御信号生成部３３０に指示する。
【００１６】
制御信号生成部３３０は、全ての状態異常に関する警報情報を中継器１００のさらに前段の中継器を介して送信端局に向けて送信するため、励起レーザ３０１〜３０４を制御する制御信号を組み立て、ＬＤドライバ３１０に送信する。
警報情報は、縦続に接続した複数の中継器をリレーして送信端局に送達される。すなわち、ラマン増幅中継システムを構成するｍ段のラマン増幅中継器のうち、最終段−１段目すなわち（ｍ−１）段目の中継器は、後段のｍ段目の中継器との間の区間障害情報とｍ段目の中継器の励起レーザ障害情報（ｍ−１の障害情報と呼ぶ）を（ｍ−２）段目の中継器に送信する。（ｍ−２）段目の中継器は、後段の（ｍ−１）段目の中継器との間の区間障害情報と（ｍ−１）段目の中継器の励起レーザ障害情報（ｍ−２の障害情報と呼ぶ）に加えて、ｍ−１の障害情報を合わせて（ｍ−３）段目の中継器に送信する。このように、障害情報が各中継器で追加され、次々とリレーされて、最終送信端局に送達される。
警報情報の通知方法としては、励起光を強度変調して送出する方法や、特定の波長の励起ＣＷ光を変調して送信する方法によって行う。
【００１７】
次に本発明の第２の実施形態について図４を参照して説明する。
図４は、本発明の第２の実施形態の分布ラマン増幅中継伝送システムの構成を示すブロック図である。上り信号伝播方向、下り信号伝播方向の双方向について、分布ラマン増幅器を備えた中継器を多段に接続して端局間をつないで伝送路を構成している。各中継器は、上り下りのおのおの信号光のモニタと後段の分布ラマン増幅の励起光をモニタするように構成している。このため、ラマン増幅中継器５００（４００）は、図１の第１の実施形態の構成に加えて、下り信号回線用光ファイバ伝送路２２に結合する監視部２０２（１０２）を備える。また、励起光源ユニット５１０（４１０）は、図３の励起光源ユニット１１０を下り信号回線用に追加して備えている。
【００１８】
この実施形態では、ラマン増幅中継器４００が、図１の実施形態の説明で述べた送信端局への警報情報の送達が上り下り両方の伝送路において行えると共に、上り信号回線を介してモニタした後段のラマン増幅中継器５００の励起光強度や光ファイバ伝送路１２のモニタ情報を、下り信号回線（光ファイバ伝送路２２）を励起するラマン増幅励起光に載せて、ラマン増幅中継器５００に送り、ラマン増幅中継器５００では、中継器４００から受信したモニタ情報に基づき励起光源ユニット５１０の備える励起レーザ出力を制御することができ、送信端局からの遠隔制御のみならず、中継器間の協働によって、ローカルに自律的な保守管理が行える。
ここで、モニタ情報の送信は、励起レーザユニット内の特定光源に信号を重畳または、特定波長を変調するサブキャリアを用いる等の方法で行う。
【００１９】
さらに、図１の実施形態の説明で述べた、自中継装置内の励起光源ユニットを制御してＡＬＣ動作を行うことは勿論できるが、仮に信号光伝搬方向に関して前段の光中継器のＡＬＣ動作に不具合等が生じ、上り光ファイバ伝送路１１を伝搬し、ラマン増幅中継器４００に入力する信号光のレベル低下が激しく、自中継器４００のＡＬＣ動作では、励起光の能力に限界があって、次段の光ファイバ伝送路１２に転送する信号光レベルが所要のレベルに維持できないような場合を想定してみると、本実施形態では、下り光ファイバ伝送路２２を励起する励起光を用いて、後段の中継器５００や、さらに複数の後段の中継器に指示を送って、複数の中継器の協働を得て、信号光レベルを所要のレベルに回復させることができる。
【００２０】
また、本第２の実施形態の構成を取ることによって、特に各中継スパンのスパンロスやラマン利得の経時的な変動を試験測定することができる。このために、前段の中継器４００から中継器５００の励起レーザユニット５１０に対し、制御信号を送信し、これにより励起レーザユニット５１０が、備えている各励起レーザのＯＮ／ＯＦＦを行い、光ファイバ伝送路１２の区間のスパンロスやラマン利得を測定することができる。このように実施することで、敷設済みの伝送路ファイバの損失特性や、励起レーザの試験や出力調整が行える。
【００２１】
次に第３の実施形態について図５を参照して説明する。
第１の実施形態及び第２の実施形態の各ラマン増幅中継器は、図５に示す励起光源ユニット６００を備える。励起光源ユニット６００は、各励起ＬＤ３０１〜３０４の出力を検出するＰＤ６０１〜６０４を具備し、各ＰＤの検出出力情報は、ＰＤモニタ６４０によって集線され、励起ＬＤの障害情報が、モニタ情報受信部６２０に出力される。モニタ情報受信部６２０は、励起光モニタ部５３と信号光モニタ部５２からの情報に加えて、自中継器が備える励起光源の障害等に関する情報もモニタし、ＬＤドライバ６１０によって前段増幅区間１２（１３）、２２（２３）を励起する励起光に重畳して送信することができ、縦続してつながっている各中継器の励起光源に関する情報を前段への励起光に多重しリレーして送信端局に送信することができる。送信端局では、励起光を介して伝送路障害情報と各中継器の励起光源の障害等の情報を各中継器のリレーによって集中的に収集することができる。これによって、伝送路の障害か、励起ＬＤの障害かの、さらに詳細な状態の特定が可能となる。また隣接中継器間でモニタ値の比較を行うことにより、より正確なファイバ特性などが検出できる。
【００２２】
以上の実施形態の説明では、後方励起の場合を説明したが、前方励起であっても同様に構成でき、同様な効果を得ることができる。
【００２３】
【発明の効果】
以上述べたように、本発明ではラマン増幅中継伝送システムにおいて隣接中継器から注入されるラマン増幅用励起光をモニタすることにより、中継スパンの伝送路の障害、品質劣化を検出する構成をとっているため、従来検出できなかった中継器内の特定の励起レーザの出力異常を検出することが可能であり、かつモニタ自体は１中継区間で行うため、励起光が起こす非線形効果による劣化の割合が少なくてすむ。
本発明では中継スパン伝播後の励起光情報をモニタすることにより、ファイバの障害を検出することができる他、励起レーザの状態を確認することが可能である。特に励起光源ユニット１１０で信号光モニタ部からの情報に基づき波長多重信号光の出力一定制御ＡＬＣを実施しているような場合、各中継器からの出力レベルは見掛け上一定出力で動作しているが、各励起レーザの出力が、出力限界までパワーをあげているような場合があり、この場合、複数の励起レーザが正常に動作しているかどうか判定できない。しかし、励起光を出力している中継器自体において励起光出力をモニタすることによりＡＬＣを実施している中継器においても励起レーザの過出力あるいは出力していない等の情報を検出できる。
さらに、本発明では、隣接中継器から、送信元中継器のラマン増幅用励起光の出力をオン／オフ制御を実施することにより、中継スパンのスパンロスやラマン利得を測定することが可能である。
【００２４】
【図面の簡単な説明】
【図１】本発明のラマン増幅中継伝送システムの第１の実施形態の構成を示すブロック図である。
【図２】本発明のラマン増幅中継器が備える監視部の構成を示すブロック図である。
【図３】本発明のラマン増幅中継器が備える励起レーザ制御部の構成を示すブロック図である。
【図４】本発明のラマン増幅中継伝送システムの第２の実施形態の構成を示すブロック図である。
【図５】本発明のラマン増幅中継器が備える励起レーザ制御部の別なる構成を示すブロック図である。
【図６】光増幅中継伝送路における信号光のレベルダイアグラムを示す説明図である。
【図７】従来の希土類添加光ファイバ増幅中継システムの構成を示すブロック図である。
【図８】ラマン増幅の概要を説明する説明図である。
【符号の説明】
１１光ファイバ伝送路
５２信号光モニタ部
５３励起光モニタ部
３０１〜３０４ＬＤ
１０１監視部
１００ラマン増幅中継器
１１０励起光源ユニット
１１１光サーキュレータ
２００ラマン増幅中継器
３００励起レーザ制御部
３１０ＬＤドライバ
３２０モニタ情報受信部
３３０制御信号生成部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical amplification repeater transmission system using distributed Raman amplification using an optical fiber transmission line itself as an optical amplification medium.
[0002]
[Prior art]
Conventionally, in wavelength division multiplexing transmission, long-distance transmission is performed by connecting a plurality of optical amplification repeaters equipped with an EDFA (erbium-doped optical fiber amplifier), which is a kind of rare earth-doped optical fiber amplifier, in multiple stages.
FIG. 7 is a block diagram showing a configuration of a conventional transmission relay system. As shown in the figure, a transmission line is formed by connecting repeaters equipped with optical direct amplifiers in multiple stages to connect between terminal stations. And in order to cover the transmission line loss over a long distance from the transmission line to the receiving terminal station and maintain the signal output level, output constant control ALC (Automatic Level Control) is performed so that the output from each amplifier becomes constant. (FIG. 6).
In a long-distance transmission relay system, transmission line monitoring including deterioration over time of an optical amplifier pumping light source and optical amplifier and the transmission line itself is an important technology. In particular, since it takes a great deal of cost to recover from a failure like an ocean optical relay system, it is extremely important to identify a fault point and a faulty part.
Regarding the excitation light source of the optical amplifier, the ALC monitors the output level of the signal light from the amplifier, and when the monitor value detects a fluctuation from a predetermined output level, the power of the excitation laser is controlled, Control is performed so that the level of the signal light is always constant. In the EDFA repeater, the wavelength is normally pumped by one type of light source and has a plurality of pumping lasers for pumping the optical amplifier as backup light sources. Is normally operated at a saturated output, and therefore there is a problem that a failure of the pump laser cannot be detected by the signal light monitor.
[0003]
For monitoring the transmission path, a method that uses OTDR (Optical Time Domain Reflectmetry) or the like is often performed. The line monitoring method using the OTDR probe light is that the monitoring wavelength is incident from the terminal station, is transmitted on the OTDR path of the monitoring transmission line section, and is reflected at the break point of the transmission line optical fiber, etc. The received return light is observed with an OTDR measuring device to monitor the state of the optical transmission line.
However, when this monitoring method is applied to long-distance transmissions of several thousand kilometers or more, the monitoring light is affected by the nonlinear optical effects and noise of the optical fiber during propagation in the transmission line, resulting in measurement value deterioration and time fluctuations. It becomes easy. In order to cope with this and increase the measurement accuracy, it is necessary to take an average of the monitor values for a long time. However, the measurement time is several hours, and there is a problem in terms of rapid and accurate failure detection.
[0004]
On the other hand, for the purpose of extending the relay section and improving the S / N ratio of the transmission optical signal, a relay transmission system using a distributed Raman amplification effect using the optical fiber transmission line itself as a gain medium has been studied. FIG. 8 shows the relationship between the Raman pumping light and the signal amplification band in the Raman amplification effect. When the transmission line is a quartz optical fiber, the signal light is amplified so as to have a gain peak on the long wave side of about 100 nm (13.2 THz) of the excitation light. Therefore, the amplification wavelength band can be set relatively freely by using a plurality of pumping light sources having different wavelengths, which is greatly different from the rare earth-doped optical fiber amplifier in which the amplification wavelength band is determined by the element to be added and the host material. Furthermore, if a multi-wavelength excitation method is used, the amplification wavelength band can be expanded flexibly. Moreover, it is also possible to use an already laid optical fiber.
Even in this method, since it is long-distance transmission, transmission line monitoring including deterioration of the excitation light source and transmission line loss over time and switching to spare parts constituting the repeater are autonomously performed remotely or by the repeater itself. It is important to be able to do it. In particular, the Raman amplifier can secure a band with a plurality of wavelength excitation light sources. Conversely, if a light source with a single wavelength deteriorates, the optical amplification band characteristics will dip and the transmission quality will deteriorate. . For this reason, it is more important to monitor failure of the excitation light source than to the EDFA relay transmission system, and it is important to establish a monitoring method capable of distinguishing whether the cause of the failure is in the transmission path or in the excitation light source.
Regarding the transmission line monitoring, when the OTDR monitoring method is applied to the line monitoring of the distributed Raman optical amplifying and relaying system, the same problem as in the EDFA optical relaying and transmission system occurs. In the case of distributed Raman amplification, the monitoring light is also subject to fluctuations due to the influence of fluctuations in Raman amplification gain, making accurate measurement difficult.
In order to monitor the loss distribution of a transmission line that is a distributed Raman amplifier and a gain medium, a method of injecting inspection pulse light whose polarization state is temporally changed into the transmission line and detecting the backscattered light is disclosed. (For example, refer to Patent Document 1). The method for detecting the backscattering of the inspection pulse light has the same problem as the above-described OTDR method.
Also, as a pumping light source monitoring method, a method is disclosed in which pumping light from a fiber-type optical amplifier is branched and transmitted to a monitoring station, and pumping light from a subsequent optical amplifier is transferred to the monitoring station by bypassing its own amplifier. (See, for example, Patent Document 2). However, this pumping light source monitoring method for transferring the pumping light from the subsequent stage to the monitoring station bypassing its own amplifier has a drawback that the optical circuit configuration in the repeater becomes complicated.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-235772
[Patent Document 2]
JP-A-5-040073
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of such problems, and in a long-distance multistage relay transmission system to which Raman amplification is applied, the status of optical fibers and optical repeaters constituting an optical transmission line can be easily monitored. It is an object to provide a method and a configuration that can be quickly and accurately performed.
[0007]
[Means for Solving the Problems]
The method for monitoring and controlling an optical amplifying repeater transmission system according to the present invention provides an optical transmission between a signal light transmitting terminal station and a receiving terminal station via a plurality of repeaters to which pumping light sources composed of a plurality of light sources having different wavelengths are connected. A transmission system for optically amplifying and repeating signal light transmitted through a transmission line connected in cascade by a fiber transmission line by a distributed Raman light amplification effect, Multiple repeaters Each repeater Is Excitation light for exciting the distributed Raman light amplification effect in the optical fiber transmission line section between the adjacent first adjacent repeaters, Backward excitation propagating in the opposite direction to the signal light Sent out from another adjacent second repeater and output from the optical fiber transmission line section between the second adjacent repeater Be done The residual excitation light, In the excitation light monitor Identify and monitor the wavelength, From the output of the excitation light monitor unit, Transmission line failure in the optical fiber transmission line section between the second adjacent repeater and , Abnormal output of the excitation light source provided in the second adjacent repeater And fault information from the second adjacent repeater superimposed on the residual pump light Detect Then, the signal light is branched and monitored, and the output of the excitation light source included in each repeater is controlled so that the branch monitor output of the signal light becomes constant at a predetermined value, and further, from the second adjacent repeater Fault information, information on transmission path faults in the section between each repeater and the second adjacent repeater, information on output abnormality of the excitation light source provided in the second adjacent repeater, and excitation provided in each repeater Information on the output abnormality of the light source is transmitted to the first adjacent repeater as the failure information of each repeater, superimposed on the excitation light. It is characterized by that.
[0008]
In addition, the monitoring control method of the optical amplification repeater transmission system according to the present invention includes a first transmission / reception terminal station including an uplink transmission device and a downlink reception device, and a second transmission / reception terminal station including an uplink reception device and a downlink transmission device. Signals that are connected in cascade via a plurality of repeaters to which two pairs of upstream and downstream optical fiber transmission lines and pumping light sources composed of a plurality of light sources having different wavelengths are connected. In a bidirectional transmission system that amplifies and repeats light by distributed Raman light amplification effect, Multiple repeaters Each repeater Is , Adjacent adjacent repeater The pumping light that excites the distributed Raman light amplification effect in the upstream and downstream optical fiber transmission line sections In the backward pumping that propagates in the opposite direction to the signal light Send out, Adjacent repeater Output from the optical fiber transmission line section Be done The residual excitation light, In the excitation light monitor Identify and monitor the wavelength, From the output of the pump light monitor unit, the optical fiber transmission line section Transmission line failure and abnormal output of the excitation light source provided in the adjacent repeater Fault information from the adjacent repeater superimposed on the residual pump light Detect And the failure information from the adjacent repeater, the information on the transmission line failure, the information on the output abnormality of the excitation light source provided in the adjacent repeater, and the information on the output abnormality of the excitation light source provided in each repeater. Is superimposed on the pumping light of the pumping light source and is sent to the adjacent relay as fault information of each relay It is characterized by that.
[0009]
The optical amplification repeater transmission system of the present invention uses an optical fiber transmission line between a signal light transmitting terminal station and a receiving terminal station via a plurality of repeaters to which pumping light sources composed of a plurality of light sources having different wavelengths are connected. A transmission system for optically amplifying and repeating signal light transmitted in a cascade and connected through a transmission line by a distributed Raman optical amplification effect, Multiple repeaters Each repeater Is In the optical fiber transmission line section between the adjacent first adjacent repeaters, pumping light that excites the distributed Raman light amplification effect, Backward excitation propagating in the opposite direction to the signal light Output from the second adjacent repeater adjacent to the means for sending out and output from the optical fiber transmission line section between the second adjacent repeater Be done The residual excitation light, In the excitation light monitor Means for identifying and monitoring wavelengths; From the output of the excitation light monitor unit, Transmission line failure in the optical fiber transmission line section between the second adjacent repeater and , An output abnormality of the excitation light source provided in the second adjacent repeater; Fault information from the second adjacent repeater superimposed on the residual pump light Means to detect A means for branching and monitoring the signal light, and controlling the output of the excitation light source included in each repeater so that the branch monitor output of the signal light becomes a predetermined value, and a failure from the second adjacent repeater Information, information on the transmission path failure in the section between each repeater and the second adjacent repeater, information on the output abnormality of the excitation light source provided in the second adjacent repeater, and the excitation light source provided in each repeater Is output to the first adjacent repeater as superimposed on the excitation light as failure information of each repeater. Means.
[0010]
The optical amplification repeater transmission system according to the present invention provides an uplink / downlink channel between a first transmission / reception terminal station having an uplink transmission device and a downlink reception device and a second transmission / reception terminal station having an uplink reception device and a downlink transmission device. Connected in cascade via a pair of optical fiber transmission lines and a plurality of repeaters to which pumping light sources consisting of a plurality of light sources having different wavelengths are connected. A bidirectional transmission system for optical amplification relaying by an amplification effect, Multiple repeaters Each repeater Is , Adjacent adjacent repeater The pumping light that excites the distributed Raman light amplification effect in the upstream and downstream optical fiber transmission line sections In the backward pumping that propagates in the opposite direction to the signal light Means for sending out; Adjacent repeater Output from the optical fiber transmission line section Be done The residual excitation light, In the excitation light monitor Means to identify and monitor the wavelength; From the output of the excitation light monitor unit, the optical fiber transmission line section Transmission line failure and abnormal output of the excitation light source provided in the adjacent repeater Fault information from the adjacent repeater superimposed on the residual pump light Means to detect , Failure information from adjacent repeaters, transmission path failure information, information on output abnormality of the excitation light source provided in the adjacent repeaters, and information on output abnormality of the excitation light source provided in each repeater, Means for transmitting to adjacent repeaters as fault information of each repeater, superimposed on the excitation light of the excitation light source provided, It is characterized by providing.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a distributed Raman amplification repeater transmission system according to a first embodiment of the present invention, in which repeaters having distributed Raman amplifiers are connected in multiple stages to connect end stations with transmission lines. It is composed. The Raman amplification repeater 100 and the Raman amplification repeater 200 carry out distributed Raman amplification by making excitation light incident on the optical fiber transmission line 11 or 12 so as to perform backward pumping. As in the case of the EDFA, there are a forward pumping method in which pumping light propagates in the optical fiber in the same direction as the signal light, a backward pumping method in which the pumping light propagates in the reverse direction, and a bidirectional pumping method. In the example, an embodiment of the backward excitation method will be described.
The Raman amplification repeater 100 includes an excitation light source unit 110 that outputs Raman amplification excitation light, a monitoring unit 101, and an optical circulator 111. The Raman amplification repeater 200 has the same configuration.
The optical circulator 111 (211) transfers and outputs the signal light from the optical fiber transmission line 11 (12) to the subsequent optical fiber transmission line 12 (13). Further, the pumping light from the pumping light source unit 110 (210) is output as backward pumping light to the optical fiber transmission line 11 (12).
[0012]
The monitoring unit 101 (201) branches and monitors part of the signal light from the optical fiber transmission line 11, and also monitors the power of pumping light from the subsequent repeater 200 through the optical fiber transmission line 12. The monitor information is output to the excitation light source unit 110. The configuration of the monitoring unit 101 (201) is shown in FIG. The monitoring unit includes a coupler 51 for combining and extracting the signal light and the excitation light from the subsequent-stage repeater 200, a signal light monitor unit 52 that receives and photoelectrically converts the signal light, and the excitation light from the subsequent-stage repeater 200. The monitor information from each monitor unit is transmitted to the excitation laser control unit 300 included in the excitation light source unit 110.
Each of the monitor units 52 and 53 receives an optical filter (optical FIL) that demultiplexes received light, a plurality of light receiving elements (PD) that photoelectrically convert a plurality of demultiplexed wavelength lights, and a plurality of light receiving element output signals. Light receiving signal processing units 54 and 55 that perform processing such as digitization and output to the excitation laser control unit 300 of the excitation light source unit 110 are provided.
[0013]
The configuration of the excitation light source unit 110 is shown in FIG.
The pumping light source unit 110 is based on a plurality of pumping lasers (LD301 to 304) for backward Raman pumping the optical fiber transmission line 11 (12), and monitor information received from the power control of the pumping light and the monitoring unit 101 (201). An excitation laser controller 300 that adds a control signal to the excitation light is provided.
The pump laser is configured to combine two Raman pumping light sources having the same wavelength as a pair and to combine the wavelengths with a pair of pumping light sources of other wavelengths (WDM coupler 307) after polarization combining (PBCs 305 and 306). Here, an example of a two-wavelength 4LD configuration is shown.
The excitation laser control unit 300 includes an LD driver 310 that drives the excitation laser, a monitor information receiving unit 320 that receives monitor information from the signal light monitoring unit 52 and the excitation light monitoring unit 53 of the monitoring unit 101 (201), and a monitor. The control signal generator 330 generates a control signal to be added to the excitation laser beam output from the output of the information receiver.
[0014]
Next, the operation of the embodiment of the present invention will be described.
In the Raman amplification repeater 100, the signal light transmitted through the optical fiber transmission line 11 is branched by the optical coupler 51 and detected by the signal light monitor unit 52 of the monitoring unit 101. If there is a decrease in the light reception level of all the wavelength multiplexed lights detected by the signal light monitor unit 52, it can be understood that the output of the pumping LDs 301 to 304 of the own repeater 101 is decreased or the section failure of the optical fiber transmission line 11 occurs. If a dip or a protrusion is generated in the laser beam, it is determined that the pump laser has a specific wavelength in the Raman amplification repeater 100.
The pumping light output from the pumping light source unit 210 provided in the subsequent stage Raman amplification repeater 200 that relays the signal light and Raman-pumped in the optical fiber transmission line 12 is detected by the pumping light monitoring unit 53 of the monitoring unit 101. If there is a decrease in the light reception level of all of the excitation lights of a plurality of wavelengths detected by the excitation light monitor unit 53, the output of the excitation LDs 301 to 304 of the rear-stage repeater 201 will decrease, the loss of the optical fiber transmission line 12 will increase, the Raman gain will decrease, etc. If it is found that it is a section fault and there is a large variation in the intensity of Raman pumping light of a plurality of wavelengths, it is determined that the fault is a fault such as an output abnormality of a pumping laser of a specific wavelength in the later stage Raman amplification repeater 200. This determination is performed by the monitor information receiving unit 320.
As described above, since the monitoring unit 101 can monitor the output level of each wavelength of the signal light and the excitation light, a decrease in the Raman amplification output specifying the section, a transmission path failure, and the output of the Raman excitation light source of the specific wavelength It is possible to detect abnormally distinctly.
[0015]
Next, a Raman amplification relay that detects a state abnormality such as a decrease in amplification in a specific section, a failure of the optical fiber transmission line 11 (12), or a failure of the excitation light source of the self-amplification repeater 100 or the Raman amplification repeater 200 in the previous stage. The operation of the container 100 will be described.
Information that the received light signal processing units 54 and 55 detect the abnormal state is sent to the monitor information receiving unit 320 of the excitation light source unit 110. The monitor information receiving unit 320 detects abnormal state information from the two received light signal processing units. When detecting the failure that the signal light level from the signal light monitor unit 52 is lowered or increased from a predetermined level, the monitor information receiving unit 320 sends the Raman backward pumping LD of its own repeater to the control signal generating unit 330. Outputs an instruction to increase or decrease the output of. That is, the Raman amplification operation in the section 11 is ALC controlled. Further, when there is an output abnormality in the pump laser of the own Raman amplification repeater, the control signal generator 330 is instructed to control the output of a specific LD of the pump lasers 301 to 304.
Further, from the received signal from the pumping light monitoring unit 53 that monitors the level of the pumping light from the subsequent Raman amplification repeater 200, the monitor information receiving unit 3320 causes the line disconnection in the section 12 and the pumping laser in the Raman amplification repeater 200. Detects abnormalities such as a decrease in overall output and failure of a specific laser. In addition, the pumping light from the repeater 200 is superposed with information on the abnormal state of the pumping laser of the subsequent repeater after the repeater 200. These are detected and instructed to the control signal generator 330.
[0016]
The control signal generation unit 330 assembles control signals for controlling the excitation lasers 301 to 304 in order to transmit alarm information related to all state abnormalities to the transmitting terminal station via the repeater further upstream of the repeater 100, Transmit to the LD driver 310.
The alarm information is delivered to the transmitting terminal station by relaying a plurality of repeaters connected in cascade. That is, among the m-stage Raman amplification repeaters constituting the Raman amplification repeater system, the last stage-1 stage, that is, the (m-1) -th repeater is connected to the subsequent m-stage repeater. Section fault information and pump laser fault information (referred to as m-1 fault information) of the m-th repeater are transmitted to the (m-2) -th repeater. The (m-2) -th stage repeater includes the section fault information between the (m-1) -th stage repeater and the excitation laser fault information (m-) of the (m-1) -th stage repeater. 2), the m-1 failure information is combined and transmitted to the (m-3) -th stage repeater. Thus, failure information is added at each repeater, relayed one after another, and delivered to the final transmitting terminal station.
As a method for notifying the alarm information, a method for transmitting the excitation light after modulating the intensity or a method for modulating and transmitting the excitation CW light having a specific wavelength are used.
[0017]
Next, a second embodiment of the present invention FIG. Will be described with reference to FIG.
FIG. 4 is a block diagram showing the configuration of the distributed Raman amplification repeater transmission system according to the second embodiment of the present invention. In both directions of the upstream signal propagation direction and the downstream signal propagation direction, repeaters having distributed Raman amplifiers are connected in multiple stages to connect the terminal stations to form a transmission line. Each repeater is configured to monitor the upstream and downstream signal light and the pump light of the subsequent distributed Raman amplification. For this reason, the Raman amplification repeater 500 (400) includes a monitoring unit 202 (102) coupled to the downlink signal line optical fiber transmission line 22 in addition to the configuration of the first embodiment of FIG. Further, the excitation light source unit 510 (410) is additionally provided with the excitation light source unit 110 of FIG. 3 for the downlink signal line.
[0018]
In this embodiment, the Raman amplification repeater 400 can deliver alarm information to the transmitting terminal station described in the description of the embodiment of FIG. 1 on both the upstream and downstream transmission lines, and monitor it via the upstream signal line. The pumping light intensity of the subsequent Raman amplification repeater 500 and the monitor information of the optical fiber transmission line 12 are placed on the Raman amplification pumping light that excites the downstream signal line (optical fiber transmission line 22) and sent to the Raman amplification repeater 500. The Raman amplification repeater 500 can control the pump laser output of the pump light source unit 510 based on the monitor information received from the repeater 400, and can be used not only for remote control from the transmitting terminal station but also for cooperation between repeaters. By the operation, local autonomous maintenance management can be performed.
Here, the monitor information is transmitted by a method such as superimposing a signal on a specific light source in the excitation laser unit or using a subcarrier that modulates a specific wavelength.
[0019]
Further, although it is possible to perform the ALC operation by controlling the pumping light source unit in the own repeater described in the description of the embodiment of FIG. 1, it is assumed that the ALC operation of the preceding optical repeater is temporarily performed with respect to the signal light propagation direction. When the malfunction occurs, the level of the signal light that propagates through the upstream optical fiber transmission line 11 and is input to the Raman amplification repeater 400 is drastically reduced. In the ALC operation of the repeater 400, there is a limit to the ability of the pumping light, Assuming a case where the level of the signal light transferred to the optical fiber transmission line 12 at the next stage cannot be maintained at a required level, in the present embodiment, pump light that excites the downstream optical fiber transmission line 22 is used. By sending an instruction to the subsequent repeater 500 or a plurality of subsequent repeaters, the signal light level can be recovered to a required level with the cooperation of the plural repeaters.
[0020]
Further, by adopting the configuration of the second embodiment, it is possible to test and measure the span loss and the Raman gain of each relay span over time. For this purpose, a control signal is transmitted from the repeater 400 in the previous stage to the pump laser unit 510 of the repeater 500, whereby the pump laser unit 510 turns on / off each pump laser provided therein, and the optical fiber. The span loss and Raman gain of the section of the transmission line 12 can be measured. By carrying out in this way, the loss characteristics of the installed transmission line fiber, the pump laser test and the output adjustment can be performed.
[0021]
Next, a third embodiment will be described with reference to FIG.
Each Raman amplification repeater of the first embodiment and the second embodiment includes an excitation light source unit 600 shown in FIG. The excitation light source unit 600 includes PDs 601 to 604 that detect the outputs of the respective excitation LDs 301 to 304. The detection output information of each PD is collected by the PD monitor 640, and the failure information of the excitation LD is displayed as the monitor information receiving unit 620. Is output. The monitor information receiving unit 620 monitors not only the information from the pumping light monitoring unit 53 and the signal light monitoring unit 52 but also information on the failure of the pumping light source provided in the own repeater, and the LD driver 610 performs the upstream amplification section 12 ( 13), 22 (23) can be superimposed on the pumping light to be transmitted, and information on the pumping light source of each relay connected in cascade is multiplexed with the pumping light to the previous stage and relayed to transmit Can be sent to the station. The transmission terminal station can collect information on the transmission path failure information and the failure of the pumping light source of each repeater by the relay of each repeater through the pumping light. As a result, it is possible to specify a more detailed state of the failure of the transmission path or the failure of the excitation LD. Also, more accurate fiber characteristics can be detected by comparing monitor values between adjacent repeaters.
[0022]
In the above description of the embodiment, the case of backward excitation has been described. However, even forward excitation can be configured in the same manner, and the same effect can be obtained.
[0023]
【The invention's effect】
As described above, in the present invention, the Raman amplification repeater transmission system monitors the Raman amplification pumping light injected from the adjacent repeater, thereby detecting the failure of the transmission path in the repeater span and the quality deterioration. Therefore, it is possible to detect an output abnormality of a specific excitation laser in a repeater that could not be detected in the past, and since the monitor itself is performed in one relay section, the rate of deterioration due to nonlinear effects caused by excitation light is reduced. Less.
In the present invention, by monitoring the pump light information after propagation through the relay span, it is possible to detect the failure of the fiber and to check the state of the pump laser. In particular, when the pumping light source unit 110 performs the output constant control ALC of the wavelength multiplexed signal light based on the information from the signal light monitor unit, the output level from each repeater apparently operates at a constant output. However, there are cases where the output of each pumping laser has increased its power to the output limit. In this case, it cannot be determined whether or not a plurality of pumping lasers are operating normally. However, by monitoring the pumping light output in the repeater that outputs the pumping light, it is possible to detect information such as the excessive output of the pumping laser or not being output even in the repeater that performs the ALC.
Furthermore, in the present invention, it is possible to measure the span loss and the Raman gain of the relay span by performing on / off control on the output of the pump light for Raman amplification of the source repeater from the adjacent repeater.
[0024]
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of a Raman amplification repeater transmission system of the present invention.
FIG. 2 is a block diagram showing a configuration of a monitoring unit provided in the Raman amplification repeater of the present invention.
FIG. 3 is a block diagram showing a configuration of a pump laser controller provided in the Raman amplification repeater of the present invention.
FIG. 4 is a block diagram showing a configuration of a second embodiment of the Raman amplification repeater transmission system of the present invention.
FIG. 5 is a block diagram showing another configuration of an excitation laser controller provided in the Raman amplification repeater of the present invention.
FIG. 6 is an explanatory diagram showing a level diagram of signal light in an optical amplification repeater transmission line.
FIG. 7 is a block diagram showing a configuration of a conventional rare earth-doped optical fiber amplification repeater system.
FIG. 8 is an explanatory diagram for explaining an outline of Raman amplification;
[Explanation of symbols]
11 Optical fiber transmission line
52 Signal light monitor
53 Excitation light monitor
301-304 LD
101 Monitoring unit
100 Raman amplification repeater
110 Excitation light source unit
111 Optical circulator
200 Raman amplification repeater
300 Excitation laser controller
310 LD driver
320 Monitor information receiver
330 Control signal generator

Claims

The signal light transmission terminal station and the reception terminal station are connected in cascade by an optical fiber transmission line via a plurality of repeaters to which pumping light sources composed of a plurality of light sources having different wavelengths are connected, and the transmission line is transmitted. In a transmission system that repeats optical signal amplification using distributed Raman light amplification effect,
Each repeater of the plurality of repeaters is
Excitation light for exciting the distributed Raman light amplification effect is sent to the optical fiber transmission line section between the adjacent first adjacent repeaters by backward pumping that propagates in the opposite direction to the signal light ,
Sent from the second adjacent repeater to another becomes adjacent monitor the residual pump light output from the optical fiber transmission line section, to identify the wavelength in the excitation light monitor unit between said second adjacent repeaters And
Wherein the output of the excitation light monitor unit, and a transmission line fault in the optical fiber transmission line section between the second adjacent repeaters, an output abnormality of the second said excitation light source adjacent repeater comprises of the residual Detecting fault information from the second adjacent repeater superimposed on the excitation light ,
Branch monitoring the signal light, and controlling the output of the excitation light source included in each repeater so that the branch monitor output of the signal light is constant at a predetermined value;
Fault information from the second adjacent repeater, information on transmission path faults in the section between each repeater and the second adjacent repeater, and an excitation light source included in the second adjacent repeater Information on output abnormality and information on output abnormality of the excitation light source included in each repeater is transmitted to the first adjacent repeater as superimposed on the excitation light as failure information of each repeater.
A supervisory control method for an optical amplification repeater transmission system.

The transmission terminal station transmits the failure information of the transmission path section constituting the optical amplification repeater transmission system and the output abnormality information of the excitation light source included in each repeater adjacent to the transmission terminal station. Monitoring the entire optical amplification repeater transmission system.
The monitoring control method for an optical amplification repeater transmission system according to claim 1 .

Between the first transmission / reception terminal station including the uplink transmission device and the downlink reception device and the second transmission / reception terminal station including the uplink reception device and the downlink transmission device, two pairs of upstream and downstream optical fiber transmission lines, Bidirectionally connected via a plurality of repeaters to which pumping light sources consisting of a plurality of different light sources are connected, and optically amplifies and repeats signal light transmitted on each of the upstream and downstream of the transmission path by a distributed Raman light amplification effect In transmission systems,
Each repeater of the plurality of repeaters is
The pumping light that excites the distributed Raman light amplification effect in the upstream and downstream optical fiber transmission line sections between adjacent adjacent repeaters, and is sent by backward pumping that propagates in the opposite direction to the signal light ,
The sent from the adjacent repeaters, the residual pumping light outputted from the optical fiber transmission line section, and monitored to identify the wavelength in the excitation light monitor unit,
From the output of the pumping light monitoring unit, the transmission path fault in the optical fiber transmission path section, the output abnormality of the pumping light source provided in the adjacent repeater, and the fault information from the adjacent repeater superimposed on the residual pumping light to detect the door,
Fault information from the adjacent repeater, information on the transmission path fault, information on output abnormality of the excitation light source provided in the adjacent repeater, and information on output abnormality of the excitation light source provided in each repeater, Superimposing on the excitation light of the excitation light source provided in each repeater, and transmitting to the adjacent repeater as fault information of each repeater,
A supervisory control method for an optical amplification repeater transmission system.

Control the excitation light source of the adjacent repeater using the failure information of each repeater,
The monitoring control method for an optical amplification repeater transmission system according to claim 3.

The first or second transceiver terminal stations constituting each of the upstream or downstream optical amplifier repeater transmission system, and the transmission path information related to the failure information the excitation light output abnormality of sections, wherein each first Or received from the adjacent repeater connected to the upstream or downstream transmission path of the second transmitting / receiving terminal station, and monitoring the entire optical amplification repeater transmission system,
The monitoring control method for an optical amplification repeater transmission system according to claim 3 or 4 ,

Each repeater transmits a control signal for controlling on / off of the excitation light source included in the adjacent repeater, superimposed on the excitation light propagating in the same direction as the signal light, so that the adjacent repeater is transmitted. measuring one or both of the transmission loss and the amplification gain of the transmission line section between the vessels,
The monitoring control method for an optical amplification repeater transmission system according to any one of claims 3 to 5 .

The signal light transmission terminal station and the reception terminal station are connected in cascade by an optical fiber transmission line via a plurality of repeaters to which pumping light sources composed of a plurality of light sources having different wavelengths are connected, and the transmission line is transmitted. In a transmission system that repeats optical signal amplification using distributed Raman light amplification effect,
Each repeater of the plurality of repeaters is
Means for transmitting pumping light for exciting the distributed Raman light amplification effect to the optical fiber transmission line section between the adjacent first adjacent repeaters by backward pumping that propagates in the opposite direction to the signal light ;
Sent from the second adjacent repeater to another becomes adjacent monitor the residual pump light output from the optical fiber transmission line section, to identify the wavelength in the excitation light monitor unit between said second adjacent repeaters Means to
Wherein the output of the excitation light monitor unit, and a transmission line fault in the optical fiber transmission line section between the second adjacent repeaters, an output abnormality of the second said excitation light source adjacent repeater comprises of the residual Means for detecting failure information from the second adjacent repeater superimposed on the excitation light ;
Means for branch-monitoring the signal light, and controlling the output of the excitation light source included in each of the repeaters so that the branch monitor output of the signal light is constant at a predetermined value;
Fault information from the second adjacent repeater, information on transmission path faults in the section between each repeater and the second adjacent repeater, and an excitation light source included in the second adjacent repeater Means for transmitting the output abnormality information and the output abnormality information of the pumping light source included in each repeater to the first adjacent repeater superimposed on the pumping light as failure information of each repeater ,
An optical amplification repeater transmission system comprising:

The transmission terminal station transmits the failure information of the transmission path section constituting the optical amplification repeater transmission system and the output abnormality information of the excitation light source included in each repeater adjacent to the transmission terminal station. Means for monitoring the entire optical amplification repeater transmission system,
The optical amplification repeater transmission system according to claim 7 , further comprising:

Between the first transmission / reception terminal station including the uplink transmission device and the downlink reception device and the second transmission / reception terminal station including the uplink reception device and the downlink transmission device, two pairs of upstream and downstream optical fiber transmission lines, Bidirectionally connected via a plurality of repeaters to which pumping light sources consisting of a plurality of different light sources are connected, and optically amplifies and repeats signal light transmitted on each of the upstream and downstream of the transmission path by a distributed Raman light amplification effect In transmission systems,
Each repeater of the plurality of repeaters is
Means for transmitting pumping light for exciting the distributed Raman light amplification effect in the upstream and downstream optical fiber transmission line sections between adjacent repeaters by backward pumping that propagates in the opposite direction to the signal light ; ,
The sent from the adjacent repeaters, the residual pumping light outputted from the optical fiber transmission line section, and means for monitoring to identify the wavelength in the excitation light monitor unit,
From the output of the pumping light monitoring unit, the transmission path fault in the optical fiber transmission path section, the output abnormality of the pumping light source provided in the adjacent repeater, and the fault information from the adjacent repeater superimposed on the residual pumping light and means for detecting the door,
Fault information from the adjacent repeater, information on the transmission path fault, information on output abnormality of the excitation light source provided in the adjacent repeater, and information on output abnormality of the excitation light source provided in each repeater, Means for transmitting to the adjacent repeater as fault information of each repeater by superimposing on the excitation light of the excitation light source included in each repeater;
An optical amplification repeater transmission system comprising:

10. The optical amplification repeater transmission system according to claim 9 , further comprising means for controlling a pumping light source of the adjacent repeater using failure information of each repeater.

The first or second transceiver terminal stations constituting each of the upstream or downstream optical amplifier repeater transmission system, and the transmission path information related to the failure information the excitation light output abnormality of sections, wherein each first Or means for receiving from the adjacent repeater connected to the upstream or downstream transmission path of the second transmitting / receiving terminal station and monitoring the entire optical amplification repeater transmission system;
The optical amplification repeater transmission system according to claim 9 or 10 , further comprising:

Each repeater transmits a control signal for controlling on / off of the excitation light source included in the adjacent repeater, superimposed on the excitation light propagating in the same direction as the signal light, so that the adjacent repeater is transmitted. It means for measuring one or both of the transmission loss and the amplification gain of the transmission line section between the vessels,
The optical amplification repeater transmission system according to claim 9, further comprising: