JP3693982B2 - WDM transmission apparatus and WDM transmission method - Google Patents

Description

となるように決めればよい。例えば、クライアント信号の伝送速度が40 Gbit/sであり、ＷＤＭ伝送装置間を接続している光ファイバの総偏波分散値がx=10 psの場合には、伝送速度が40 Gbit/sのままでは偏波分散による波形歪により大きなパワーペナルティが生じる。この場合には、ＯＥＯ型多重分離部において波長あたりの伝送速度を10 Gbit/sに変換し、4本の10 Gbit/s信号を波長多重して伝送することにより、偏波分散によるパワーペナルティを回避して、符号誤り率の低い信号伝送が可能となる。また、ファイバの総偏波分散値が5 psである場合に、４本のクライアント信号を伝送する例を考える。この場合には、この4本のクライアント信号を1本の40 Gbit/s信号に多重して伝送することが可能である。これにより、使用する波長数を減らすことにより、周波数利用効率を向上させることができる。また、一般に1個の40 Gbit/sインタフェースは4個の10 Gbit/sインタフェースよりも低コストに実現できるため、多重化による低コスト化も期待できる。
【００３１】
次に、光ファイバの損失に対する伝送速度の最適化について説明する。長距離光ファイバ伝送では、雑音の少ない信号伝送を実現するため、光ファイバの損失により減衰した光信号光を伝送路の途中、及び受信端で光ファイバ増幅器により増幅しており、この光ファイバ増幅器で発生する光雑音（ASE: Amplified Spontaneous Emission）により、伝送後の符号誤り率が決定される。伝送後の誤り率を決定するSN比は、各区間での光ファイバの損失をLとすると、
【数２】

で表される。ここで、Ｎ_avは受信器に入力される信号光の単位時間あたりの光子数、qは電子の電荷、N_SPは光増幅器の自然放出光係数、ｍは中継用、及び受信用光増幅器の総数、B_oは光フィルタの半値幅、 B_eは受信器のベースバンド帯域（B_eは通常、伝送速度の0.7倍程度）、Gは光増幅器の利得であり、 G＝1/Lである。(2)式より、波長あたりの出力光パワーが一定であれば、伝送後に得られるSN比は、B_eが小さいほど高くなる。波長あたりの伝送速度ＢをB_e＝0.7×Ｂとすれば、システムに要求される符号誤り率（Ｓ/Ｎ）_oを規定すると、波長あたりの伝送速度は一意に決定される。すなわち、光ファイバの損失Lに対する最適な伝送速度が求められる。
次に、波長分散及び非線形定数に対する伝送速度の最適化について説明する。光ファイバ中では、伝播中の光信号は、波長分散、及び非線形光学効果のひとつである光Kerr効果（光強度に比例して屈折率が変化する現象）により信号に歪が生じる。伝播後の光信号波形は、光ファイバ中での光信号の伝播を記述する非線形シュレディンガー方程式
【数３】

を計算機シミュレーションにより解析することにより、求めることが可能である。ここで、Aは光信号の電界、 αは損失係数、β₁＝1/ｖ_g（ｖ_gは光信号の群速度）、β₂ は波長分散に比例する係数であり、 γは非線形定数である。(3)式に基づいて、各伝送速度における光信号伝送シミュレーションを行うことにより、伝送後の光信号歪によるパワーペナルティを見積もることが可能であり、各々の伝送速度においてシミュレーションを行うことにより、パワーペナルティの少ない伝送速度を選ぶことができる。
【００３２】
最後に、一般的なケースとして、光ファイバの損失値、波長分散値、偏波モード分散値、及び非線形係数のすべてのパラメータを考慮した伝送速度の決定方法を以下に説明する。上記のパラメータを考慮した光ファイバ中での伝播方程式は、以下の結合非線形シュレディンガー方程式で表される：
【数４】

ここで、Ａ_x、Ａ_yは光信号の２つの偏波成分、β_1x−β_1yは偏波モード分散による伝播定数差である。受信端での光信号波形は、光ファイバ中でのランダムモード結合を考慮して(4)式を数値シミュレーションにより解析することにより計算することが出来る。この受信光波形より光信号のオンレベル、オフレベルを求め、さらに伝送路中で発生する光増幅器雑音を考慮して、以下の式によりQ値を計算する。
【数５】

ここで、Ｓ₁、Ｓ₀はオンレベル、オフレベルの信号電流、σ₁、σ₀はそれぞれ光増幅器雑音によるオンレベル、オフレベルの雑音電流の標準偏差であり、
【数６】

で与えられる。(5)式で与えられるQ値はSN比に相当する量であり、Q=16.9 dBが符号誤り率10-12に相当する。光ファイバの特性に応じて伝送速度を決定するためには、様々な伝送速度に対して上記の方法によりQ値を計算し、Q値が最も大きくなるように伝送速度を決定すればよい。
【００３３】
以上説明した方法により光ファイバの特性に応じて伝送速度を決定して伝送することが可能であり、これにより、符号誤り率の低い高品質の信号伝送や、周波数利用効率の向上、低コスト化などのメリットが期待できる。
【００３４】
本発明の第２の実施形態について図３〜図５を参照して説明する。一般に、長距離ＷＤＭ伝送で利用できる波長帯域は、主に光増幅器の利得帯域によって制限されており、この利得帯域内で、できるだけ大容量の情報伝送を実現することが必要である。従って、ＷＤＭ信号の波長間隔は、可能な限り小さくするのが望ましい。しかしながら、周波数間隔の下限は、隣接する波長間の変調スペクトルの重なりにより生じるクロストークによって制限されるため、波長あたりの伝送速度が高くなるほど周波数間隔は広げる必要がある。
【００３５】
一方、光信号の伝送可能距離は、第一実施形態で説明したように、主に伝送路中で発生する光信号の歪や光雑音によって制限され、また波長あたりの伝送速度に依存する。また、この伝送可能距離は、以下に説明するように、波長間隔にも依存する。
【００３６】
光ファイバ中では、非線形光学効果の一種である光Kerr効果により、波形歪や波長間のクロストークが発生し、これにより伝送距離が制限される。この場合、波形歪、クロストークは、ファイバの波長分散値が小さいほど影響が大きく、また波長間隔が狭いほど影響が大きいという特徴がある。すなわち、周波数利用効率が一定である場合には、伝送速度が小さく波長間隔が密なほど、非線形効果による影響が大きくなる。光Kerr効果による屈折率の変化の大きさは、ファイバ中での光信号の有効断面積、及び非線形屈折率より決まる非線形定数に比例する。以上説明したように、伝送可能距離は、波長当りの伝送速度に依存し、また波長間隔にも依存するという性質を持っている。
【００３７】
従って、本発明のＷＤＭ伝送システムにおいて、周波数利用効率の低下を回避しつつ、伝送後の符号誤り率を最小にするように波長あたりの伝送速度及び波長間隔を決定することによって、従来の速度変換を行わない場合に比べて、より高品質、高周波数利用効率の信号伝送が可能となる。
【００３８】
以下に、ＷＤＭ信号の伝送シュミレーションによりその効果を説明する。本実施形態では、（a）8本の40 Gbit/s信号を標準シングルモードファイバ（SMF、波長分散値: 17 ps/nm/km）を用いて伝送する場合、(b) 32本の10 Gbit/s信号を非零分散シフトファイバ（NZDSF、波長分散値: 2.5 ps/nm/km）を用いて伝送する場合の２つのケースを考える。図３に本シミュレーションで検討した伝送路構成を示す。伝送路は、伝送用ファイバとファイバの損失を補償する中継器（光ファイバアンプ）より構成されており、それぞれのケースについて、光ファイバの波長分散値は、各区間を伝送後に１００％補償する構成とした。計算で用いたファイバパラメータを表１に示す。
【表１】

【００３９】
図４は、上述の２つのケースに対して、従来技術により速度変換を行わないで伝送した場合、及び、本ＷＤＭ伝送装置により、速度変換を行って伝送した場合の、伝送距離に対するQ値の依存性の計算結果を示した図である。ここで、光ファイバ増幅器は(a)では120 kmごと、(b)では100 kmごとに配置し、各光ファイバ増幅器において全区間のファイバの波長分散値を補償する構成とし、光ファイバ入力パワーは各場合について最適化された値を用いている。また、Q値はSN比に相当する量であり、Q=16.9 dBが符号誤り率10-12に相当する。図４より、(a)では、本発明のＷＤＭ伝送装置により、8本の40 Gbit/sのクライアント信号を32本の10 Gbit/s信号に分割して伝送することによって、より高いQ値（より低い符号誤り率）で伝送することが可能であることがわかる。ここで、10 Gbit/s/chの場合の方がQ値が高くなるのは、伝送速度を下げて受信器のフィルタ帯域幅を1/4としたことにより、ASEに起因するビート雑音が減っているためであり、周波数間隔が小さくなることによる非線形効果の影響は、伝送ファイバの分散値が17 ps/nm/kmと大きいため、SN比の改善に比べて非線形効果による劣化量は小さいためである。
【００４０】
次に、(b)の場合には、本発明のＷＤＭ伝送装置により、32本の10 Gbit/s信号を、8本の40 Gbit/s信号に多重化して伝送した場合のほうが高いQ値が得られることがわかる。これは、NZDSFでは、光ファイバの波長分散値が2.5 ps/nm/kmと小さく、10 Gbit/s/ch、25 GHz間隔では非線形効果による波形歪、波長間クロストークが大きいが、波長あたりの伝送速度を40 Gbit/sとして波長間隔を広げることにより、この非線形効果の影響を抑圧した効果が大きく、この改善量がSN比の劣化分を上回るためである。図５に、それぞれの伝送速度におけるNZDSF 700 km伝送後のアイダイヤグラム及び光スペクトルを示す。（a）、（c）は、40 Gbit/s/chで100 GHz間隔、（b）、（d）は、10 Gbit/s/chで25 GHz間隔である場合についてそれぞれ示している。10 Gbit/s/chの場合には、非線形効果の影響により４光波混合光が発生しており、これがクロストークとなってアイパターンが劣化していることがわかる。
【００４１】
以上説明したように、光ファイバの性質により、最適な波長あたりの伝送速度及び波長間隔は異なることがわかる。光ファイバの特性に応じて伝送速度及び波長間隔を決定するには、光ファイバの損失、波長分散値、偏波分散値が既知であれば、様々な伝送速度及び波長間隔に対して、上記の数値シミュレーションにより、Q値を計算し、Q値が最も大きくなるように伝送速度及び波長間隔を決定すればよい。
【００４２】
以上により、光ファイバの特性に応じて伝送速度及び波長間隔を決定することが可能となり、より符号誤り率の低い高品質の信号伝送や、周波数利用効率の向上、低コスト化などのメリットが期待できる。
【００４３】
本発明の第３の実施形態について図６〜図８を参照して説明する。図６は、ＷＤＭ伝送装置が複数の方路に対応するインタフェースを持ち、メッシュ上に接続されてクライアント信号を伝送するＷＤＭネットワークを示す。図７に本実施形態のＷＤＭ伝送装置の構成を示す。本実施形態のＷＤＭ伝送装置は、ＯＥＯ型多重分離部７１と、光接続部７６と、波長多重分離部７２と、帯域割当制御部７３より構成されており、ＯＥＯ型多重分離部７１は、クライアント装置７４、及び光接続部７６に接続されている。ＯＥＯ型多重分離部７１は、クライアント装置７４からのクライアント信号を複数の低速信号に分離する、または複数のクライアント信号を高速信号に多重する。光接続部７６は、ＯＥＯ型多重分離部７１及び各方路に対応する複数の波長多重分離部７２に接続されており、波長単位または複数の波長単位で入出力ポートの接続を行う。波長多重分離部７１は光接続部７６及び光ファイバ７５に接続されており、光接続部７６から出力された光信号を波長領域で多重して光ファイバに送出するとともに、光ファイバより受信した波長多重信号を波長ごとに分離して光接続部７６に出力する。また、帯域割当制御部７３は、伝送ファイバの損失、波長分散値、偏波分散値、非線形定数のデータより、最適な波長あたりの伝送速度を決定し、ＯＥＯ型多重分離部での電気多重分離を制御する。
【００４４】
光接続部７６は、受信した光信号がＯＥＯ型多重分離部７１に接続されているクライアント装置４宛の信号であれば、その信号をＯＥＯ型多重分離部７１に送る。一方、光接続部７６は、受信した光信号が他の装置に接続されているクライアント装置４宛の信号であれば、光信号のまま波長多重分離部２に送り、同じ方路に出力される光信号を波長多重してファイバに送出する。従って、本実施形態の場合には、帯域割当制御部３において伝送速度を決定する際に、出力側に接続されているファイバの特性だけでなく、対向するクライアント装置４が収容されているＷＤＭ伝送装置までのすべてのファイバの特性を考慮して伝送速度を決定する必要がある。
【００４５】
図８に、本実施形態のＷＤＭ伝送装置を用いたクライアント信号の伝送例を示す。図８(a)は、光ファイバの偏波分散により、高速信号（40 Gbit/s）の伝送可能距離が１リンクに限られている場合である。この場合、10 Gbit/sでは４倍の偏波分散値まで伝送することが可能である。シングルモード光ファイバの偏波分散値は、ファイバ長の平方根に比例する性質があるので、距離にしてほぼ16倍の距離のファイバの偏波分散値まで伝送可能となる。従って、40 Gbit/sを４本の10 Gbit/sに分離して伝送することにより、２リンク以上の区間にわたって伝送が可能である。また、図８(b)に示すように、４本の10 Gbit/s信号は異なるルートを通って伝送した場合でも、ルート間の伝播遅延差がバーチャルコンカチネーションで吸収できる遅延差の範囲内であれば、伝送可能である。
【００４６】
また、ＷＤＭ伝送装置において、伝送速度のみならず波長間隔もファイバの特性に応じて決定する場合にも、出力側に接続されている光ファイバのみならず、対向するクライアント装置が接続されているＷＤＭ伝送装置までのすべての光ファイバの特性（損失、波長分散値、偏波分散値、非線形定数）を考慮して決定すればよいことは説明するまでもない。
【００４７】
本発明の第４実施形態について図９、図１０を参照して説明する。図９は、光ファイバの波長分散値の波長依存性を示した図である。ここに示すように、長距離通信に用いられる1.5〜1.6μmの波長帯では、波長分散値は波長が長くなるほど大きくなるという性質がある。ファイバがDSFの場合には、長距離通信で主に用いられている1550 nm帯では、波長分散値は0 ps/nm/km程度と非常に小さく、また、Lバンドと呼ばれる波長1600 nm帯では、3〜4 ps/nm/nm程度となる。一方、第２実施形態で説明したように、ファイバ中での非線形効果による波形歪、クロストークは、波長分散値が小さく、波長間隔が小さくなるほど影響が大きくなる。
【００４８】
本発明のＷＤＭ伝送装置において、図１０に示したように、波長分散値の小さい波長領域では、波長間隔を大きくして伝送速度の大きい信号に割り当て、波長分散が大きくなるに従って、波長間隔が小さく、伝送速度の低い信号に割り当てることによって、非線形効果による影響を軽減することが可能である。具体的には、図１０に示すように、光接続部１０４に接続された波長多重分離部（多重側）を異なる波長間隔の合分波部１００a、１００bを光カプラ１０１で結合し、光接続部１０５に接続された波長多重分離部（分離側）を異なる波長間隔の波長帯Ａ用合分波器１０３a及び波長帯Ｂ用合分波器１０３ｂを光カプラ１０２で結合して構成することで実現可能である。
ここで、合分波部にはアレイ導波路格子フィルタが適用可能であり、光導波路の構造により波長間隔を変化させることが可能である。また、光カプラとしては、例えばファイバ溶融延伸型カプラを用いても良い。
【００４９】
本発明の第５実施形態について図１１を参照して説明する。図１１は、各ＷＤＭ伝送装置が異種のファイバで接続されている場合を示す。ファイバAは零分散波長が1550 nm程度のDSFであり、ファイバBは零分散波長が1590nm程度のNZDSFである例を考える。この場合に、ファイバAに対して実施形態３に従って高速信号を短波長側、低速信号を長波長側に割り当てた場合、ファイバBにおいては、高速信号の方は、波長分散値が-4〜-5 ps/nm/km程度となり、波長分散値の絶対値が大きくなる。一方、低速信号のほうは、波長分散値が0 ps/nm/km程度となる。このため、ファイバB中で、波長間隔の狭い低速信号のほうが、非線形効果の影響を強く受けてしまうという問題が起こる。
【００５０】
この場合には、図１２に示すように、高速信号は波長分散の絶対値が小さい長波長側の波長に変換し、低速信号は波長分散の絶対値の大きい短波長側に変換する波長変換部１０７を光接続部１０６と、波長帯Ａ用合分波器１０３a及び波長帯Ｂ用合分波器１０３ｂの間にさらに設けることにより、非線形効果の影響を軽減することが可能である。このように、異種のファイバで接続されたＷＤＭ伝送装置においては、波長変換機能を設けることにより、非線形効果の影響の増大を回避することが可能である。
【００５１】
【発明の効果】
以上説明したように、請求項１および請求項１０に記載の発明によれば、光ファイバの損失値、波長分散値、偏波モード分散値、または非線形定数に基づいて、光ファイバに送出する伝送信号の波長あたりの伝送速度を制御するので、波長あたりの伝送速度を設定可能となり、伝送路中での伝送速度に依存する伝送距離制限、符号誤り率の低下を抑圧し、ＷＤＭネットワークの高品質化、経済化が可能である。
【００５２】
請求項２および請求項１１に記載の発明によれば、光ファイバの損失値、波長分散値、偏波モード分散値、または非線形定数に基づいて、光ファイバに送出する伝送信号の波長あたりの伝送速度及び前記伝送信号の波長間隔を制御するので、さらに、波長間隔を設定可能とすることにより、異なる伝送速度の信号を含む光信号を多重化する際に、周波数利用効率の低下を回避しつつ、光ファイバ中での非線形光学効果による信号劣化を抑圧することが可能となる。
【図面の簡単な説明】
【図１】本発明第１実施形態のＷＤＭ伝送装置の構成図である。
【図２】ＯＥＯ型多重分離部の構成図である。
【図３】ＷＤＭ伝送シミュレーションにおける伝送路構成を示す図である。
【図４】伝送距離に対するＱ値の依存性の計算結果を示すグラフである。
【図５】ＮＺＤＳＦ 700 km 伝送後のアイダイヤグラム及び光スペクトルの計算結果を示す図である。
【図６】本発明第３実施形態のＷＤＭ伝送装置を適用したＷＤＭネットワークの構成図である。
【図７】本発明第３実施形態のＷＤＭ伝送装置の構成図である。
【図８】本発明第３実施形態のＷＤＭ伝送装置を適用した帯域割当方式を示す図である。
【図９】波長分数値の波長依存性を示す図である。
【図１０】本発明第４実施形態の波長多重分離部の構成図である。
【図１１】ＷＤＭ伝送装置間が異種のファイバによって接続されている場合のネットワーク構成、及び波長分散値の波長依存性を示す図である
【図１２】波長変換部を備えたＷＤＭ伝送装置の構成例及び波長変換を示す図である。
【符号の説明】
１a、1b…ＯＥＯ型多重分離部
２a、２b…波長多重分離部
３…帯域割当制御部
４…クライアント装置
５…光ファイバ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a WDM transmission technique that transmits client signals economically and with high quality in a large-capacity wavelength division multiplexing (WDM) network.
[0002]
[Prior art]
In a long-distance optical fiber network, a WDM transmission technique for multiplexing and transmitting a plurality of wavelengths in one optical fiber is applied, and economical and large-capacity information transmission is realized. In a WDM transmission apparatus, an optical signal received from a client apparatus is converted into a wavelength-controlled optical signal that can be wavelength-multiplexed, and an optical signal having a plurality of wavelengths is multiplexed on one optical fiber in a wavelength demultiplexing unit. And send it into the fiber. On the receiving side, the received WDM signal is separated in the wavelength region and sent to the client device.
In a conventional WDM transmission apparatus, generally, an optical signal received from a client apparatus is not subjected to speed conversion, is wavelength-converted at the received transmission speed, and is multiplexed and transmitted to a WDM signal. Some devices have developed WDM transmission by multiplexing multiple client signals into higher-speed signals, but the transmission device itself determines the transmission rate per wavelength in consideration of the characteristics of the fiber. Currently, it has no function. The wavelength interval in the wavelength demultiplexing unit is usually defined regardless of the transmission rate of the client signal, the chromatic dispersion value of the optical fiber, the loss, and the like.
[0003]
[Problems to be solved by the invention]
However, when client signals are transmitted using the current WDM transmission apparatus, there are the following problems.
In long-distance WDM networks, the transmission distance is limited by the loss, chromatic dispersion value, polarization dispersion value, etc. of the optical fiber connecting the WDM transmission devices, and this transmission distance depends on the transmission speed per wavelength. To do. Therefore, when the optical signal received from the client device is transmitted at the transmission rate as it is, there is a possibility that the optical signal is transmitted at a transmission rate that is not suitable for the characteristics of the transmission path. In this case, in the long-distance network, there is a problem that a 3R repeater is required in the middle of the transmission path, leading to an increase in the cost of the network.
[0004]
In addition, when client signals having different transmission rates are multiplexed on a WDM signal, the frequency utilization efficiency may be lowered when the wavelength interval is fixed as in the conventional apparatus. The frequency band that can be used in long-distance WDM communication is mainly limited by the gain band of the optical fiber amplifier, and there is a problem that a decrease in frequency utilization efficiency leads to a decrease in transmittable capacity. Furthermore, due to the chromatic dispersion characteristics of the optical fiber and the nonlinear optical effect in the fiber, waveform distortion and crosstalk between wavelengths occur, which causes a transmission distance limitation and an increase in code error rate. Since narrowing of the frequency interval increases signal deterioration due to this nonlinear effect, a wavelength arrangement technique that takes this nonlinear effect into consideration is required.
[0005]
The present invention has been made in consideration of such a background, and by making it possible to set the transmission rate per wavelength, it is possible to reduce the transmission distance limitation and the code error rate depending on the transmission rate in the transmission path. The objective is to realize a high-quality, economical WDM network that is suppressed. It is another object of the present invention to suppress signal degradation due to a nonlinear optical effect in an optical fiber while avoiding a decrease in frequency utilization efficiency when multiplexing optical signals including signals having different transmission rates.
[0006]
[Means for Solving the Problems]
  According to the invention, the object is achieved by means described in the claims. That is, the invention according to claim 1 is a WDM transmission apparatus that multiplexes a plurality of client signals and transmits an optical fiber based on a loss value, a chromatic dispersion value, a polarization mode dispersion value, or a nonlinear constant of the optical fiber. The transmission speed of the transmission signal sent to the optical fiber is controlled by separating one client signal into low-speed signals with a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signal.Then, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0007]
  According to a second aspect of the present invention, in a WDM transmission apparatus that multiplexes a plurality of client signals and transmits an optical fiber in a wavelength region, the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber is set. Based on the transmission rate of the transmission signal sent to the optical fiber by separating one client signal into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signal, and Controls the wavelength interval of transmission signalsThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0008]
  The invention according to claim 3 is an OEO type demultiplexing unit connected to a plurality of client devices and a wavelength demultiplexing unit, wherein the client signal from the client device is separated into a plurality of low-speed optical signals, or A plurality of client signals from the client device are multiplexed on a high-speed optical signal and output to the wavelength demultiplexing unit, an optical fiber connecting the plurality of WDM transmission devices, and the OEO demultiplexing unit. A connected wavelength demultiplexing unit that multiplexes the optical signal output from the OEO-type demultiplexing unit in a wavelength region, sends the multiplexed wavelength multiplexed signal to the optical fiber, and transmits the wavelength multiplexed signal from the optical fiber; A WDM including a wavelength demultiplexing unit that receives the multiplexed signal and demultiplexes the wavelength multiplexed signal in a wavelength region and outputs the demultiplexed signal to the OEO demultiplexing unit In the transmission device, based on the loss value, the chromatic dispersion value, the polarization mode dispersion value, or the nonlinear constant of the optical fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength demultiplexing unit, is determined. , Equipped with a bandwidth allocation control unit that controls by separating one client signal into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signalThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0009]
  The invention according to claim 4 is an OEO type demultiplexing unit connected to a plurality of client devices and a wavelength demultiplexing unit, wherein the client signal from the client device is separated into a plurality of low-speed optical signals, or A plurality of client signals from the client device are multiplexed on a high-speed optical signal and output to the wavelength demultiplexing unit, an optical fiber connecting the plurality of WDM transmission devices, and the OEO demultiplexing unit. A connected wavelength demultiplexing unit that multiplexes the optical signal output from the OEO-type demultiplexing unit in a wavelength region, sends the multiplexed wavelength multiplexed signal to the optical fiber, and transmits the wavelength multiplexed signal from the optical fiber; A WDM including a wavelength demultiplexing unit that receives the multiplexed signal and demultiplexes the wavelength multiplexed signal in a wavelength region and outputs the demultiplexed signal to the OEO demultiplexing unit In the transmission device, based on the loss value, the chromatic dispersion value, the polarization mode dispersion value, or the nonlinear constant of the optical fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength demultiplexing unit, is determined. , A band in which one client signal is separated into a plurality of low-speed signals of a plurality of wavelengths, or a plurality of client signals are multiplexed into one high-speed signal to control in the wavelength region, and the wavelength interval of the transmission signal is controlled in the wavelength region Has an allocation control unitThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0010]
  The invention according to claim 5 is an OEO type demultiplexing unit connected to a plurality of client devices, wavelength demultiplexing units, and an optical connecting unit, and demultiplexes a client signal from the client devices into a plurality of low-speed optical signals. Alternatively, an OEO-type demultiplexing unit that multiplexes a plurality of client signals from the client device into a high-speed optical signal and outputs the multiplexed signal to the wavelength multiplexing / demultiplexing unit, and an optical fiber connecting the plurality of WDM transmission devices and the OEO type A demultiplexing unit and a wavelength demultiplexing unit connected to the optical connecting unit, wherein the optical signal output from the OEO demultiplexing unit is multiplexed in a wavelength region, and the multiplexed wavelength multiplexed signal is transmitted to the optical fiber; At the same time, when the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in the wavelength region and output to the OEO demultiplexing unit. An optical connection that is connected to a long demultiplexing unit, a plurality of wavelength demultiplexing units corresponding to each path of the OEO type demultiplexing unit and the optical fiber, and connects input / output ports in units of wavelengths or in units of wavelengths In the WDM transmission apparatus comprising the optical fiber, an optical signal transmitted from the wavelength demultiplexing unit to the optical fiber based on a loss value, a chromatic dispersion value, a polarization mode dispersion value, or a nonlinear constant of the optical fiber. A band allocation control unit that controls the transmission speed of a transmission signal in the wavelength region by separating one client signal into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signalThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0011]
  The invention according to claim 6 is an OEO type demultiplexing unit connected to a plurality of client devices, wavelength demultiplexing units, and an optical connecting unit, and demultiplexes a client signal from the client devices into a plurality of low-speed optical signals. Alternatively, an OEO-type demultiplexing unit that multiplexes a plurality of client signals from the client device into a high-speed optical signal and outputs the multiplexed signal to the wavelength multiplexing / demultiplexing unit, and an optical fiber connecting the plurality of WDM transmission devices and the OEO type A demultiplexing unit and a wavelength demultiplexing unit connected to the optical connecting unit, wherein the optical signal output from the OEO demultiplexing unit is multiplexed in a wavelength region, and the multiplexed wavelength multiplexed signal is transmitted to the optical fiber; At the same time, when the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in the wavelength region and output to the OEO demultiplexing unit. An optical connection that is connected to a long demultiplexing unit, a plurality of wavelength demultiplexing units corresponding to each path of the OEO type demultiplexing unit and the optical fiber, and connects input / output ports in units of wavelengths or in units of wavelengths In the WDM transmission apparatus comprising the optical fiber, an optical signal transmitted from the wavelength demultiplexing unit to the optical fiber based on a loss value, a chromatic dispersion value, a polarization mode dispersion value, or a nonlinear constant of the optical fiber. The transmission speed of the transmission signal is controlled in the wavelength region by separating one client signal into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signal, and the wavelength interval of the transmission signals is Equipped with a bandwidth allocation controller that controls in the wavelength regionThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0012]
  The invention according to claim 7 is a WDM transmission in which a plurality of client signals are multiplexed and transmitted through an optical fiber.MethodThe transmission rate of the transmission signal sent to the optical fiber based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, and one client signal as a low-speed signal having a plurality of wavelengths. Or control by multiplexing multiple client signals into one high-speed signalThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0013]
  The invention according to claim 8 is a WDM transmission in which a plurality of client signals are multiplexed and an optical fiber is transmitted in the wavelength region.MethodThe transmission rate of the transmission signal sent to the optical fiber based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, and one client signal as a low-speed signal having a plurality of wavelengths. Or by multiplexing multiple client signals into one high-speed signal and controlling the wavelength interval of the transmission signalThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0014]
  The invention according to claim 9 is a WDM transmission in which a plurality of client signals are multiplexed in the wavelength domain and transmitted through one optical fiber.MethodThe bandwidth allocation control unit for controlling the transmission speed per wavelength of the transmission signal is configured such that the wavelength multiplexing / demultiplexing unit is based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber. The transmission speed of the transmission signal, which is an optical signal sent to the fiber, is determined by separating one client signal into low-speed signals of multiple wavelengths, or multiplexing multiple client signals into one high-speed signal, and multiple clients An OEO demultiplexing unit connected to the device and the wavelength demultiplexing unit demultiplexes the client signal from the client device into a plurality of low-speed optical signals based on the transmission rate determined by the band allocation control unit; or Multiplex a plurality of client signals from the client device into a high-speed optical signal, output to the wavelength demultiplexing unit, and a plurality of WDM transmissions The wavelength demultiplexing unit connected to the optical fiber connecting the devices multiplexes the optical signal output from the OEO type demultiplexing unit in the wavelength region, sends the multiplexed wavelength multiplexed signal to the optical fiber, and When the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in the wavelength region and output to the OEO demultiplexing unit.Then, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0015]
  The invention according to claim 10 is a WDM transmission in which a plurality of client signals are multiplexed in the wavelength domain and transmitted through one optical fiber.MethodThe bandwidth allocation control unit for controlling the transmission speed per wavelength of the transmission signal and the wavelength interval of the transmission signal in the wavelength region is set to a loss value, a chromatic dispersion value, a polarization mode dispersion value, or a nonlinear constant of the optical fiber. Based on this, the transmission rate of the transmission signal, which is an optical signal sent from the wavelength multiplexing / demultiplexing unit to the optical fiber, is separated into low-speed signals of a plurality of wavelengths, or a plurality of client signals are converted into a single high-speed signal. The OEO type demultiplexing unit connected to the plurality of client devices and the wavelength demultiplexing unit determines the transmission rate determined by the band allocation control unit and the wavelength interval of the transmission signal. Based on the wavelength interval of the transmission signal, the client signal from the client device is separated into a plurality of low-speed optical signals, or the client A plurality of client signals from a device are multiplexed on a high-speed optical signal, output to the wavelength demultiplexing unit, and a wavelength demultiplexing unit connected to an optical fiber connecting the plurality of WDM transmission units is the OEO demultiplexing unit The optical signal output from is multiplexed in the wavelength domain, the multiplexed wavelength multiplexed signal is sent to the optical fiber, and when the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in the wavelength domain, Output to the OEO demultiplexerThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0016]
  The invention according to claim 11 is a WDM transmission in which a plurality of client signals are multiplexed in the wavelength domain and transmitted through one optical fiber.MethodThe bandwidth allocation control unit for controlling the transmission speed per wavelength of the transmission signal is the optical fiber connected to the output side and the optical fiber connected to the WDM transmission device to which the opposite client device is connected. Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength multiplexing / demultiplexing unit, and a plurality of one client signal The OEO demultiplexing unit connected to the plurality of client devices and the wavelength demultiplexing unit is configured to perform the band allocation control. The client signal from the client device is separated into a plurality of low-speed optical signals based on the transmission speed determined by the unit, or A plurality of client signals from the client device are multiplexed into a high-speed optical signal, output to the wavelength demultiplexing unit, and the wavelength demultiplexing unit connected to the optical fiber connecting the plurality of WDM transmission units is the OEO type demultiplexing The optical signal output from the unit is multiplexed in the wavelength domain, and the multiplexed wavelength multiplexed signal is transmitted to the optical fiber. When the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in the wavelength domain. , Output to the OEO demultiplexerThen, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0017]
  The invention according to claim 12 is a WDM transmission in which a plurality of client signals are multiplexed in a wavelength region and transmitted through one optical fiber.MethodThe bandwidth allocation control unit for controlling the transmission speed per wavelength of the transmission signal and the wavelength interval of the transmission signal is an WDM transmission in which an optical fiber connected to the output side and a client device facing the optical connection unit are connected. Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber connected to the device, the transmission speed of the transmission signal, which is the optical signal sent to the optical fiber by the wavelength demultiplexing unit, is determined. Determining a single client signal into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into a single high-speed signal, and determining a wavelength interval of the transmission signals, and a plurality of client devices and wavelengths The OEO type demultiplexing unit connected to the demultiplexing unit is the client device based on the transmission rate determined by the band allocation control unit. Are separated into a plurality of low-speed optical signals, or a plurality of client signals from the client device are multiplexed into a high-speed optical signal and output to the wavelength demultiplexing unit to connect the plurality of WDM transmission devices The wavelength demultiplexing unit connected to the optical fiber multiplexes the optical signal output from the OEO type demultiplexing unit in the wavelength region, and sends the multiplexed wavelength multiplexed signal to the optical fiber. When a wavelength multiplexed signal is received, the wavelength multiplexed signal is separated in the wavelength region and output to the OEO demultiplexing unit.Then, when controlling the transmission rate of the transmission signal sent to the optical fiber based on the polarization mode dispersion value of the optical fiber, when the polarization mode dispersion value of the optical fiber is x, the per-wavelength The transmission speed B is determined such that 0.3 × 1 / B ≧ x.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of a WDM transmission apparatus according to a first embodiment of the present invention. This WDM transmission apparatus includes an OEO type demultiplexing unit 1, a wavelength demultiplexing unit 2, and a band allocation control unit 3. The configuration of the WDM transmission apparatus will be described below by taking the case where the client signal and the signal in the WDM network are in the SDH / SONET format as an example. The OEO type demultiplexing unit 1 is connected to a plurality of client devices 4 and a wavelength demultiplexing unit 2. When the OEO type demultiplexing unit (transmission side) 1a receives the client signal from the client device 4, the OEO type demultiplexing unit 1a performs convergence / separation in units of VC-4 (about 150 MBit / s) by an electrical switch, converts it into an optical signal, and converts the wavelength Output to the demultiplexing unit (transmission side) 2a. When the OEO type demultiplexing unit (reception side) 1b receives the optical signal from the wavelength demultiplexing unit (reception side) 2b, the OEO type demultiplexing unit (reception side) 2b performs focusing and demultiplexing by an electrical switch, converts it into an optical signal, and sends it to the client device 4 To do. The wavelength demultiplexing unit 2 a multiplexes the optical signal output from the OEO type demultiplexing unit (transmission side) 1 a in the wavelength region and transmits the multiplexed optical signal to the optical fiber 5. The wavelength demultiplexing unit 2b receives the wavelength multiplexed signal output from the optical fiber 5, separates the wavelength multiplexed signal for each wavelength, and outputs the separated signal to the OEO type demultiplexing unit (receiving side) 1b. The band allocation control unit 3 determines the optimum transmission rate per wavelength from the transmission fiber loss, chromatic dispersion value, polarization dispersion value, and nonlinear constant data, and performs the electrical demultiplexing in the OEO demultiplexing unit 1. Control.
[0025]
Here, a feature of the present invention is that a band allocation control unit 3 is newly provided, and the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber connecting the WDM transmission apparatuses. Is to determine the transmission rate per wavelength.
[0026]
Next, the configuration of the OEO demultiplexing unit 1 of the WDM transmission apparatus according to the first embodiment of the present invention will be described with reference to FIG. The OEO demultiplexing unit 1 includes an OE conversion unit 20, an EO conversion unit 25, SOH processing units 21 and 24, a virtual concatenation generation unit 22, and an electrical SW unit 23 on the transmission side. On the receiving side, an OE conversion unit 30, an EO conversion unit 35, SOH processing units 31 and 34, an electric SW unit 32, and a virtual concatenation restoration unit 33 are configured.
[0027]
Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. In the WDM transmission apparatus of this embodiment, as shown in FIG. 2, the virtual concatenation technology defined by ITU-T G.707 is applied. This is because VC-4-64c and other large-capacity information is divided into fine transmission units such as VC-3 / 4 and transmitted in the SDH / SONET path network, and VC- This is a transmission scheme in which VC-4-64c is reconfigured after reception based on information indicating the position in 4-64c. As a result, the client signal can be divided into a plurality of lower-speed optical signals and transmitted, or the plurality of client signals can be multiplexed and transmitted into one higher-speed signal.
[0028]
For example, a case where the client signal is VC-4-64c and is divided into four VC-4-16c for transmission will be described below. The STM-64 signal received from the client device 4 is OE converted by the OE conversion unit 20, and VC-4-64c is extracted through the end of section overhead information and pointer processing by the SOH processing unit 21. The VC-4-64c is divided into 64 VC-4 (VC-4-64v) by the virtual concatenation conversion unit 22. The electrical switch unit 23 switches the output port in units of VC-4. In the SOH processing unit 24, the 16 VC-4 signals are subjected to SOH processing to form STM-16, and the EO conversion unit 25 is converted to a wavelength that can be wavelength multiplexed. Is EO-converted and sent to the wavelength demultiplexing unit 2a. On the receiving side, the four received STM-16 signals are decomposed into VC-4 units after SOH termination processing by the SOH processing unit 31, and the virtual concatenation restoration unit 33 is connected via the electrical switch unit 32. The VC-4-64c is reconstructed based on the position information in the VC-4-64c input to the H4 byte and written in the H4 byte. In this way, it is possible to disassemble and transmit a plurality of lower speed signals. Conversely, it is possible to multiplex four VC-4-16c client signals and transmit them as VC-4-64c with the same configuration.
The optical signal generated by the OEO type demultiplexing unit is multiplexed with the WDM signal by the wavelength demultiplexing unit, sent to the optical fiber, and transmitted to the WDM transmission apparatus on the ground side.
[0029]
As described above, according to the configuration of this embodiment, a high-speed client signal is divided into a plurality of low-speed optical signals for transmission, or a plurality of client signals are multiplexed into a single high-speed optical signal. It becomes possible to transmit.
[0030]
Next, a method for determining the transmission rate per wavelength according to the characteristics of the optical fiber connected to the WDM transmission apparatus will be described. First, focusing on the polarization mode dispersion value of the optical fiber, a case where the transmission speed is optimized will be described. Polarization dispersion is a phenomenon in which the propagation speed in the fiber varies depending on the polarization state, and varies for each fiber core. Due to this polarization dispersion, the optical signal waveform after transmission is distorted, leading to a decrease in the code error rate and a limitation on the transmittable distance. The allowable total polarization dispersion value is known to be about 0.3 times the time slot in binary digital modulation. If the transmission rate is 10 Gbit / s, it is about 30 ps and 40 Gbit / s. If it exists, it becomes about 7.5 ps, and the allowable polarization dispersion value decreases as the transmission rate per wavelength increases. Therefore, if the polarization dispersion value of the optical fiber is x, the transmission speed B per wavelength is
[Expression 1]

You should decide so that it becomes. For example, if the transmission rate of the client signal is 40 Gbit / s and the total polarization dispersion value of the optical fiber connecting the WDM transmission devices is x = 10 ps, the transmission rate is 40 Gbit / s. If left as it is, a large power penalty is caused by waveform distortion due to polarization dispersion. In this case, the transmission rate per wavelength is converted to 10 Gbit / s in the OEO demultiplexing unit, and four 10 Gbit / s signals are wavelength-multiplexed and transmitted, thereby reducing the power penalty due to polarization dispersion. Thus, signal transmission with a low code error rate is possible. Also, consider an example in which four client signals are transmitted when the total polarization dispersion value of the fiber is 5 ps. In this case, it is possible to multiplex and transmit these four client signals into one 40 Gbit / s signal. Thereby, frequency use efficiency can be improved by reducing the number of wavelengths to be used. In general, one 40 Gbit / s interface can be realized at a lower cost than four 10 Gbit / s interfaces, and therefore, the cost can be reduced by multiplexing.
[0031]
Next, optimization of the transmission rate with respect to the loss of the optical fiber will be described. In long-distance optical fiber transmission, in order to realize signal transmission with less noise, optical signal light attenuated due to loss of the optical fiber is amplified by an optical fiber amplifier in the middle of the transmission path and at the receiving end. The code error rate after transmission is determined by optical noise (ASE: Amplified Spontaneous Emission). The S / N ratio that determines the error rate after transmission is defined as L for the loss of the optical fiber in each section.
[Expression 2]

It is represented by Where N_avIs the number of photons per unit time of the signal light input to the receiver, q is the charge of the electrons, N_SPIs the spontaneous emission coefficient of the optical amplifier, m is the total number of optical amplifiers for relay and reception, B_oIs the half width of the optical filter, B_eIs the baseband bandwidth of the receiver (B_eIs usually about 0.7 times the transmission speed), G is the gain of the optical amplifier, and G = 1 / L. From equation (2), if the output optical power per wavelength is constant, the SN ratio obtained after transmission is B_eThe smaller is the higher. Transmission speed B per wavelength is B_e= 0.7 x B, the required code error rate (S / N) for the system_o, The transmission rate per wavelength is uniquely determined. That is, an optimum transmission rate for the optical fiber loss L is required.
Next, transmission speed optimization for chromatic dispersion and nonlinear constant will be described. In an optical fiber, an optical signal being propagated is distorted by chromatic dispersion and the optical Kerr effect (a phenomenon in which the refractive index changes in proportion to the light intensity), which is one of nonlinear optical effects. The optical signal waveform after propagation is a nonlinear Schrodinger equation describing the propagation of the optical signal in the optical fiber.
[Equation 3]

Can be obtained by analyzing by computer simulation. Where A is the electric field of the optical signal, α is the loss factor, β₁= 1 / v_g(V_gIs the group velocity of the optical signal), β₂ Is a coefficient proportional to chromatic dispersion, and γ is a nonlinear constant. Based on equation (3), it is possible to estimate the power penalty due to optical signal distortion after transmission by performing an optical signal transmission simulation at each transmission speed. A transmission rate with a small penalty can be selected.
[0032]
Finally, as a general case, a method for determining a transmission rate in consideration of all parameters of an optical fiber loss value, chromatic dispersion value, polarization mode dispersion value, and nonlinear coefficient will be described below. The propagation equation in the optical fiber considering the above parameters is expressed by the following coupled nonlinear Schrodinger equation:
[Expression 4]

Where A_x, A_yIs the two polarization components of the optical signal, β_1x-Β_1yIs the propagation constant difference due to polarization mode dispersion. The optical signal waveform at the receiving end can be calculated by analyzing equation (4) by numerical simulation in consideration of random mode coupling in the optical fiber. The on-level and off-level of the optical signal are obtained from this received optical waveform, and the Q value is calculated by the following formula in consideration of optical amplifier noise generated in the transmission path.
[Equation 5]

Where S₁, S₀Is on-level, off-level signal current, σ₁, Σ₀Is the standard deviation of the on-level and off-level noise current due to optical amplifier noise,
[Formula 6]

Given in. The Q value given by Equation (5) is an amount corresponding to the SN ratio, and Q = 16.9 dB corresponds to the code error rate 10-12. In order to determine the transmission rate according to the characteristics of the optical fiber, the Q value is calculated by the above method for various transmission rates, and the transmission rate may be determined so that the Q value is maximized.
[0033]
With the method described above, it is possible to determine the transmission speed according to the characteristics of the optical fiber and transmit it. This enables high-quality signal transmission with a low code error rate, improved frequency utilization efficiency, and lower cost. We can expect merit such as.
[0034]
A second embodiment of the present invention will be described with reference to FIGS. In general, the wavelength band that can be used in long-distance WDM transmission is mainly limited by the gain band of the optical amplifier, and it is necessary to realize as large a capacity information transmission as possible within this gain band. Therefore, it is desirable to make the wavelength interval of the WDM signal as small as possible. However, since the lower limit of the frequency interval is limited by crosstalk caused by overlapping modulation spectra between adjacent wavelengths, the frequency interval needs to be increased as the transmission rate per wavelength increases.
[0035]
On the other hand, as described in the first embodiment, the transmittable distance of the optical signal is limited mainly by distortion of the optical signal and optical noise generated in the transmission path, and depends on the transmission speed per wavelength. The transmittable distance also depends on the wavelength interval, as will be described below.
[0036]
In an optical fiber, waveform distortion and crosstalk between wavelengths occur due to the optical Kerr effect, which is a kind of nonlinear optical effect, thereby limiting the transmission distance. In this case, the waveform distortion and the crosstalk are characterized in that the influence is larger as the chromatic dispersion value of the fiber is smaller, and the influence is larger as the wavelength interval is narrower. That is, when the frequency utilization efficiency is constant, the influence of the nonlinear effect becomes larger as the transmission speed is smaller and the wavelength interval is closer. The magnitude of the refractive index change due to the optical Kerr effect is proportional to the effective cross-sectional area of the optical signal in the fiber and a nonlinear constant determined by the nonlinear refractive index. As described above, the transmittable distance has the property that it depends on the transmission speed per wavelength and also on the wavelength interval.
[0037]
Therefore, in the WDM transmission system of the present invention, the conventional speed conversion is achieved by determining the transmission speed and wavelength interval per wavelength so as to minimize the code error rate after transmission while avoiding the decrease in frequency utilization efficiency. Compared to the case where the signal is not transmitted, signal transmission with higher quality and higher frequency utilization efficiency becomes possible.
[0038]
Below, the effect is demonstrated by the transmission simulation of a WDM signal. In this embodiment, (a) when transmitting 8 40 Gbit / s signals using standard single mode fiber (SMF, chromatic dispersion value: 17 ps / nm / km), (b) 32 10 Gbit / s signals Consider two cases of transmitting a / s signal using a non-zero dispersion shifted fiber (NZDSF, chromatic dispersion value: 2.5 ps / nm / km). FIG. 3 shows the transmission path configuration studied in this simulation. The transmission path is composed of a transmission fiber and a repeater (optical fiber amplifier) that compensates for the loss of the fiber. In each case, the chromatic dispersion value of the optical fiber is compensated 100% after transmission in each section. It was. Table 1 shows the fiber parameters used in the calculation.
[Table 1]

[0039]
FIG. 4 shows the Q value with respect to the transmission distance when the transmission is performed without speed conversion according to the conventional technique and when the transmission is performed with the speed conversion performed by the WDM transmission apparatus with respect to the above two cases. It is the figure which showed the calculation result of the dependency. Here, the optical fiber amplifiers are arranged every 120 km in (a) and every 100 km in (b), and each optical fiber amplifier is configured to compensate the chromatic dispersion value of the fiber in the entire section, and the optical fiber input power is Values optimized for each case are used. The Q value is an amount corresponding to the SN ratio, and Q = 16.9 dB corresponds to the code error rate 10-12. 4 (a), in the case of (a), by dividing the eight 40 Gbit / s client signals into 32 10 Gbit / s signals by the WDM transmission apparatus of the present invention, a higher Q value ( It can be seen that transmission with a lower code error rate is possible. Here, the Q value is higher in the case of 10 Gbit / s / ch because the beat noise caused by ASE is reduced by lowering the transmission rate and reducing the filter bandwidth of the receiver to 1/4. The effect of the nonlinear effect due to the smaller frequency interval is because the dispersion value of the transmission fiber is as large as 17 ps / nm / km, so the amount of degradation due to the nonlinear effect is small compared to the improvement of the SN ratio. It is.
[0040]
Next, in the case of (b), a higher Q value is obtained when 32 10 Gbit / s signals are multiplexed into 8 40 Gbit / s signals and transmitted by the WDM transmission apparatus of the present invention. It turns out that it is obtained. In NZDSF, the chromatic dispersion value of the optical fiber is as small as 2.5 ps / nm / km, and waveform distortion and inter-wavelength crosstalk due to nonlinear effects are large at 10 Gbit / s / ch and 25 GHz intervals. This is because widening the wavelength interval by setting the transmission speed to 40 Gbit / s has a large effect of suppressing the influence of this nonlinear effect, and the amount of improvement exceeds the degradation of the SN ratio. FIG. 5 shows an eye diagram and an optical spectrum after NZDSF 700 km transmission at each transmission speed. (A), (c) shows the case of 40 Gbit / s / ch at 100 GHz spacing, and (b), (d) shows the case of 10 Gbit / s / ch at 25 GHz spacing. In the case of 10 Gbit / s / ch, it can be seen that four-wave mixed light is generated due to the influence of the non-linear effect, and this causes crosstalk and the eye pattern is degraded.
[0041]
As described above, it can be seen that the optimum transmission speed and wavelength interval per wavelength differ depending on the properties of the optical fiber. In order to determine the transmission speed and wavelength interval according to the characteristics of the optical fiber, if the loss, chromatic dispersion value, and polarization dispersion value of the optical fiber are known, the transmission speed and wavelength interval described above can be obtained for various transmission speeds and wavelength intervals. It is only necessary to calculate the Q value by numerical simulation and determine the transmission rate and the wavelength interval so that the Q value is maximized.
[0042]
As a result, it is possible to determine the transmission speed and wavelength interval according to the characteristics of the optical fiber, and high-quality signal transmission with a lower code error rate, improved frequency utilization efficiency, and lower costs are expected. it can.
[0043]
A third embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows a WDM network in which a WDM transmission apparatus has interfaces corresponding to a plurality of routes and is connected on a mesh to transmit a client signal. FIG. 7 shows the configuration of the WDM transmission apparatus of this embodiment. The WDM transmission apparatus according to this embodiment includes an OEO demultiplexing unit 71, an optical connection unit 76, a wavelength demultiplexing unit 72, and a band allocation control unit 73. The OEO demultiplexing unit 71 is a client. The device 74 and the optical connection unit 76 are connected. The OEO type demultiplexing unit 71 separates the client signal from the client device 74 into a plurality of low-speed signals, or multiplexes the plurality of client signals into a high-speed signal. The optical connection unit 76 is connected to the OEO type demultiplexing unit 71 and a plurality of wavelength demultiplexing units 72 corresponding to the respective paths, and connects input / output ports in units of wavelengths or in units of wavelengths. The wavelength demultiplexing unit 71 is connected to the optical connection unit 76 and the optical fiber 75. The optical signal output from the optical connection unit 76 is multiplexed in the wavelength region and transmitted to the optical fiber, and the wavelength received from the optical fiber. The multiplexed signal is separated for each wavelength and output to the optical connection unit 76. Further, the band allocation control unit 73 determines the optimum transmission rate per wavelength from the transmission fiber loss, chromatic dispersion value, polarization dispersion value, and nonlinear constant data, and performs electrical demultiplexing in the OEO demultiplexing unit. To control.
[0044]
If the received optical signal is a signal addressed to the client device 4 connected to the OEO demultiplexing unit 71, the optical connecting unit 76 sends the signal to the OEO demultiplexing unit 71. On the other hand, if the received optical signal is a signal addressed to the client device 4 connected to another device, the optical connection unit 76 sends the optical signal as it is to the wavelength demultiplexing unit 2 and outputs it to the same path. The optical signal is wavelength-multiplexed and sent to the fiber. Therefore, in the case of the present embodiment, when determining the transmission rate in the band allocation control unit 3, not only the characteristics of the fiber connected to the output side but also the WDM transmission in which the opposing client device 4 is accommodated. It is necessary to determine the transmission rate in consideration of the characteristics of all the fibers up to the equipment.
[0045]
FIG. 8 shows an example of client signal transmission using the WDM transmission apparatus of this embodiment. FIG. 8A shows a case where the transmission distance of the high-speed signal (40 Gbit / s) is limited to one link due to the polarization dispersion of the optical fiber. In this case, it is possible to transmit up to four times the polarization dispersion value at 10 Gbit / s. Since the polarization dispersion value of a single-mode optical fiber has a property proportional to the square root of the fiber length, it is possible to transmit up to the polarization dispersion value of a fiber that is approximately 16 times the distance. Therefore, by separating 40 Gbit / s into four 10 Gbit / s and transmitting, it is possible to transmit over a section of two or more links. As shown in Fig. 8 (b), even when four 10 Gbit / s signals are transmitted through different routes, the propagation delay difference between routes is within the range of delay difference that can be absorbed by virtual concatenation. If there is, transmission is possible.
[0046]
Also, in the WDM transmission apparatus, not only the transmission speed but also the wavelength interval is determined according to the characteristics of the fiber, not only the optical fiber connected to the output side but also the WDM to which the opposite client apparatus is connected. Needless to say, it may be determined in consideration of the characteristics (loss, chromatic dispersion value, polarization dispersion value, nonlinear constant) of all optical fibers up to the transmission apparatus.
[0047]
A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a diagram showing the wavelength dependence of the chromatic dispersion value of the optical fiber. As shown here, in the wavelength band of 1.5 to 1.6 μm used for long-distance communication, the wavelength dispersion value has a property of increasing as the wavelength increases. When the fiber is DSF, the chromatic dispersion value is very small at around 0 ps / nm / km in the 1550 nm band, which is mainly used for long-distance communications, and in the 1600 nm band called the L band. 3-4 ps / nm / nm. On the other hand, as described in the second embodiment, the waveform distortion and crosstalk due to the nonlinear effect in the fiber have a larger influence as the wavelength dispersion value is smaller and the wavelength interval is smaller.
[0048]
In the WDM transmission apparatus of the present invention, as shown in FIG. 10, in the wavelength region where the chromatic dispersion value is small, the wavelength interval is increased and assigned to a signal having a high transmission rate, and the wavelength interval decreases as the chromatic dispersion increases. By allocating to a signal having a low transmission rate, it is possible to reduce the influence due to the nonlinear effect. Specifically, as shown in FIG. 10, the wavelength demultiplexing unit (multiplexing side) connected to the optical connecting unit 104 is coupled to the multiplexing / demultiplexing units 100a and 100b having different wavelength intervals by the optical coupler 101, and the optical connection is performed. The wavelength demultiplexing unit (separation side) connected to the unit 105 is configured by coupling the wavelength band A multiplexer / demultiplexer 103a and the wavelength band B multiplexer / demultiplexer 103b having different wavelength intervals by the optical coupler 102. It is feasible.
Here, an arrayed waveguide grating filter can be applied to the multiplexing / demultiplexing unit, and the wavelength interval can be changed depending on the structure of the optical waveguide. Further, as the optical coupler, for example, a fiber melt drawing type coupler may be used.
[0049]
A fifth embodiment of the present invention will be described with reference to FIG. FIG. 11 shows a case where each WDM transmission apparatus is connected by different types of fibers. Consider an example in which fiber A is a DSF with a zero dispersion wavelength of about 1550 nm, and fiber B is an NZDSF with a zero dispersion wavelength of about 1590 nm. In this case, when the high-speed signal is assigned to the short wavelength side and the low-speed signal is assigned to the long wavelength side for the fiber A according to the third embodiment, in the fiber B, the chromatic dispersion value is −4 to − The absolute value of the chromatic dispersion value is increased to about 5 ps / nm / km. On the other hand, the low-speed signal has a chromatic dispersion value of about 0 ps / nm / km. For this reason, in the fiber B, a low-speed signal with a narrow wavelength interval is strongly affected by the nonlinear effect.
[0050]
In this case, as shown in FIG. 12, the high-speed signal is converted to a wavelength on the long wavelength side where the absolute value of chromatic dispersion is small, and the low-speed signal is converted to the short wavelength side where the absolute value of chromatic dispersion is large. By further providing 107 between the optical connecting unit 106 and the wavelength band A multiplexer / demultiplexer 103a and the wavelength band B multiplexer / demultiplexer 103b, it is possible to reduce the influence of the nonlinear effect. As described above, in a WDM transmission apparatus connected by different types of fibers, it is possible to avoid an increase in the influence of the nonlinear effect by providing a wavelength conversion function.
[0051]
【The invention's effect】
As described above, according to the inventions according to claims 1 and 10, transmission to be transmitted to the optical fiber based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber. Controls the transmission speed per wavelength of the signal, so the transmission speed per wavelength can be set, and the transmission distance limitation depending on the transmission speed in the transmission path and the reduction in the code error rate are suppressed, and the high quality of the WDM network And economicization is possible.
[0052]
According to the second and eleventh aspects of the invention, transmission per wavelength of a transmission signal transmitted to the optical fiber based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber. Since the speed and the wavelength interval of the transmission signal are controlled, it is possible to set the wavelength interval, thereby avoiding a decrease in frequency utilization efficiency when multiplexing optical signals including signals of different transmission rates. It is possible to suppress signal deterioration due to the nonlinear optical effect in the optical fiber.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a WDM transmission apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of an OEO type demultiplexing unit.
FIG. 3 is a diagram illustrating a transmission path configuration in a WDM transmission simulation;
FIG. 4 is a graph showing the calculation result of the dependence of the Q value on the transmission distance.
FIG. 5 is a diagram showing a calculation result of an eye diagram and an optical spectrum after NZDSF 700 km transmission.
FIG. 6 is a configuration diagram of a WDM network to which a WDM transmission apparatus according to a third embodiment of the present invention is applied.
FIG. 7 is a configuration diagram of a WDM transmission apparatus according to a third embodiment of the present invention.
FIG. 8 is a diagram illustrating a bandwidth allocation method to which a WDM transmission apparatus according to a third embodiment of the present invention is applied.
FIG. 9 is a diagram showing the wavelength dependence of wavelength fractional values.
FIG. 10 is a configuration diagram of a wavelength demultiplexing unit according to a fourth embodiment of the present invention.
FIG. 11 is a diagram showing a network configuration when WDM transmission apparatuses are connected by different types of fibers, and wavelength dependence of chromatic dispersion values;
FIG. 12 is a diagram illustrating a configuration example of a WDM transmission apparatus including a wavelength conversion unit and wavelength conversion.
[Explanation of symbols]
1a, 1b ... OEO demultiplexer
2a, 2b ... wavelength demultiplexing unit
3 Bandwidth allocation control unit
4 ... Client device
5. Optical fiber

Claims (12)

In a WDM transmission apparatus that multiplexes a plurality of client signals and transmits an optical fiber,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal sent to the optical fiber is separated into low-speed signals of multiple wavelengths. Or by multiplexing multiple client signals into one high-speed signal ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
A WDM transmission apparatus that is determined to be In a WDM transmission apparatus that multiplexes a plurality of client signals and transmits an optical fiber in the wavelength region,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal sent to the optical fiber is separated into low-speed signals of multiple wavelengths. Or control by multiplexing a plurality of client signals into one high-speed signal, and control the wavelength interval of the transmission signal ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
A WDM transmission apparatus that is determined to be An OEO type demultiplexing unit connected to a plurality of client devices and a wavelength demultiplexing unit, which separates a client signal from the client device into a plurality of low-speed optical signals, or a plurality of client signals from the client device An OEO type demultiplexing unit that multiplexes a high-speed optical signal and outputs to the wavelength demultiplexing unit;
An optical fiber connecting a plurality of WDM transmission apparatuses and a wavelength demultiplexing unit connected to the OEO demultiplexing unit, wherein the optical signals output from the OEO demultiplexing unit are multiplexed and multiplexed in the wavelength domain A wavelength division multiplexing unit that transmits a wavelength division multiplexed signal to the optical fiber and receives the wavelength division multiplexed signal from the optical fiber, and separates the wavelength division multiplexed signal in a wavelength region and outputs the wavelength division multiplexed signal to the OEO type demultiplexing unit; In the WDM transmission apparatus provided,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength demultiplexing unit, is set as one client. A band allocation control unit for controlling signals by separating signals into a plurality of low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signal ;
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
A WDM transmission apparatus that is determined to be An OEO type demultiplexing unit connected to a plurality of client devices and a wavelength demultiplexing unit, which separates a client signal from the client device into a plurality of low-speed optical signals, or a plurality of client signals from the client device An OEO type demultiplexing unit that multiplexes a high-speed optical signal and outputs to the wavelength demultiplexing unit;
An optical fiber connecting a plurality of WDM transmission apparatuses and a wavelength demultiplexing unit connected to the OEO demultiplexing unit, wherein the optical signals output from the OEO demultiplexing unit are multiplexed and multiplexed in the wavelength domain A wavelength division multiplexing unit that transmits a wavelength division multiplexed signal to the optical fiber and receives the wavelength division multiplexed signal from the optical fiber, and separates the wavelength division multiplexed signal in a wavelength region and outputs the wavelength division multiplexed signal to the OEO type demultiplexing unit; In the WDM transmission apparatus provided,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength demultiplexing unit, is set as one client. A bandwidth allocation control unit that controls signals in the wavelength region by separating signals into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into a single high-speed signal, and controls the wavelength interval of the transmission signal in the wavelength region. Equipped ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
A WDM transmission apparatus that is determined to be An OEO type demultiplexing unit connected to a plurality of client devices and wavelength demultiplexing units and an optical connection unit, which separates a client signal from the client device into a plurality of low-speed optical signals, or from the client device An OEO demultiplexing unit that multiplexes a plurality of client signals into a high-speed optical signal and outputs the multiplexed signal to the wavelength demultiplexing unit;
An optical fiber connecting a plurality of WDM transmission apparatuses, and a wavelength demultiplexing unit connected to the OEO demultiplexing unit and the optical connecting unit, and an optical signal output from the OEO demultiplexing unit in a wavelength region A wavelength which is multiplexed and transmitted to the optical fiber, and when the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in a wavelength region and output to the OEO demultiplexing unit A demultiplexing unit;
WDM comprising an optical connection unit connected to the OEO type demultiplexing unit and a plurality of wavelength demultiplexing units corresponding to each path of the optical fiber, and connecting input / output ports in units of wavelengths or in units of wavelengths. In transmission equipment,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength demultiplexing unit, is set as one client. A band allocation control unit that controls signals in a wavelength region by separating signals into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into one high-speed signal ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
A WDM transmission apparatus that is determined to be An OEO type demultiplexing unit connected to a plurality of client devices and wavelength demultiplexing units and an optical connection unit, which separates a client signal from the client device into a plurality of low-speed optical signals, or from the client device An OEO demultiplexing unit that multiplexes a plurality of client signals into a high-speed optical signal and outputs the multiplexed signal to the wavelength demultiplexing unit;
An optical fiber connecting a plurality of WDM transmission apparatuses, and a wavelength demultiplexing unit connected to the OEO demultiplexing unit and the optical connecting unit, and an optical signal output from the OEO demultiplexing unit in a wavelength region A wavelength which is multiplexed and transmitted to the optical fiber, and when the wavelength multiplexed signal is received from the optical fiber, the wavelength multiplexed signal is separated in a wavelength region and output to the OEO demultiplexing unit A demultiplexing unit;
WDM comprising an optical connection unit connected to the OEO type demultiplexing unit and a plurality of wavelength demultiplexing units corresponding to each path of the optical fiber, and connecting input / output ports in units of wavelengths or in units of wavelengths. In transmission equipment,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal, which is an optical signal sent to the optical fiber by the wavelength demultiplexing unit, is set as one client. A bandwidth allocation control unit that controls signals in the wavelength region by separating signals into low-speed signals of a plurality of wavelengths or multiplexing a plurality of client signals into a single high-speed signal, and controls the wavelength interval of the transmission signal in the wavelength region. Equipped ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
A WDM transmission apparatus that is determined to be In a WDM transmission method for multiplexing a plurality of client signals and transmitting an optical fiber,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal sent to the optical fiber is separated into low-speed signals of multiple wavelengths. Or by multiplexing multiple client signals into one high-speed signal ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
WDM transmission method characterized by determining to be In a WDM transmission method in which a plurality of client signals are multiplexed and an optical fiber is transmitted in the wavelength region,
Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber, the transmission speed of the transmission signal sent to the optical fiber is separated into low-speed signals of multiple wavelengths. Or control by multiplexing a plurality of client signals into one high-speed signal, and control the wavelength interval of the transmission signal ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
WDM transmission method characterized by determining to be In a WDM transmission method in which a plurality of client signals are multiplexed in a wavelength region and transmitted through one optical fiber,
The bandwidth allocation control unit that controls the transmission speed per wavelength of the transmission signal is configured such that the wavelength demultiplexing unit is connected to the optical fiber based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber. The transmission speed of the transmission signal, which is an optical signal to be transmitted, is determined by separating one client signal into low-speed signals of a plurality of wavelengths, or multiplexing a plurality of client signals into one high-speed signal,
The OEO type demultiplexing unit connected to the plurality of client devices and the wavelength demultiplexing unit demultiplexes the client signal from the client device into a plurality of low-speed optical signals based on the transmission rate determined by the band allocation control unit. Or, a plurality of client signals from the client device are multiplexed into a high-speed optical signal and output to the wavelength demultiplexing unit,
The wavelength demultiplexing unit connected to the optical fiber connecting the plurality of WDM transmission apparatuses multiplexes the optical signal output from the OEO type demultiplexing unit in the wavelength region, and sends the multiplexed wavelength multiplexed signal to the optical fiber. In addition, when receiving the wavelength multiplexed signal from the optical fiber, the wavelength multiplexed signal is separated in a wavelength region, and output to the OEO demultiplexing unit ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
WDM transmission method characterized by determining to be In a WDM transmission method in which a plurality of client signals are multiplexed in a wavelength region and transmitted through one optical fiber,
The bandwidth allocation controller that controls the transmission speed per wavelength of the transmission signal and the wavelength interval of the transmission signal in the wavelength region is based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber. The wavelength multiplexing / demultiplexing unit separates the transmission speed of the transmission signal, which is an optical signal transmitted to the optical fiber, into one low-speed signal with a plurality of wavelengths, or multiplexes a plurality of client signals into one high-speed signal. And determining the wavelength interval of the transmission signal,
The OEO type demultiplexing unit connected to the plurality of client devices and the wavelength demultiplexing unit receives the client signal from the client device based on the transmission rate determined by the band allocation control unit and the wavelength interval of the transmission signal. , Separating into a plurality of low-speed optical signals, or multiplexing a plurality of client signals from the client device into a high-speed optical signal, and outputting to the wavelength demultiplexing unit,
The wavelength demultiplexing unit connected to the optical fiber connecting the plurality of WDM transmission apparatuses multiplexes the optical signal output from the OEO type demultiplexing unit in the wavelength region, and sends the multiplexed wavelength multiplexed signal to the optical fiber. In addition, when receiving the wavelength multiplexed signal from the optical fiber, the wavelength multiplexed signal is separated in a wavelength region, and output to the OEO demultiplexing unit ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
WDM transmission method characterized by determining to be In a WDM transmission method in which a plurality of client signals are multiplexed in a wavelength region and transmitted through one optical fiber,
The bandwidth allocation control unit that controls the transmission speed per wavelength of the transmission signal includes the optical fiber connected to the output side and the optical fiber connected from the optical connection unit to the WDM transmission device to which the opposite client device is connected. Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant, the transmission rate of the transmission signal, which is an optical signal sent from the wavelength demultiplexing unit to the optical fiber, and one client signal for a plurality of wavelengths. It is determined by separating into multiple low-speed signals or multiplexing multiple client signals into one high-speed signal,
The OEO type demultiplexing unit connected to the plurality of client devices and the wavelength demultiplexing unit demultiplexes the client signal from the client device into a plurality of low-speed optical signals based on the transmission rate determined by the band allocation control unit. Or, a plurality of client signals from the client device are multiplexed into a high-speed optical signal and output to the wavelength demultiplexing unit,
The wavelength demultiplexing unit connected to the optical fiber connecting the plurality of WDM transmission apparatuses multiplexes the optical signal output from the OEO type demultiplexing unit in the wavelength region, and sends the multiplexed wavelength multiplexed signal to the optical fiber. In addition, when receiving the wavelength multiplexed signal from the optical fiber, the wavelength multiplexed signal is separated in a wavelength region, and output to the OEO demultiplexing unit ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
WDM transmission method characterized by determining to be In a WDM transmission method in which a plurality of client signals are multiplexed in a wavelength region and transmitted through one optical fiber,
The bandwidth allocation control unit that controls the transmission speed per wavelength of the transmission signal and the wavelength interval of the transmission signal includes the optical fiber connected to the output side and the optical connection unit to the WDM transmission device to which the opposite client device is connected. Based on the loss value, chromatic dispersion value, polarization mode dispersion value, or nonlinear constant of the optical fiber connected to the optical fiber, the transmission rate of the transmission signal, which is an optical signal sent from the wavelength multiplexing / demultiplexing unit to the optical fiber, is Determining by separating one client signal into low-speed signals of a plurality of wavelengths, or multiplexing a plurality of client signals into one high-speed signal, and determining the wavelength interval of the transmission signal;
The OEO type demultiplexing unit connected to the plurality of client devices and the wavelength demultiplexing unit demultiplexes the client signal from the client device into a plurality of low-speed optical signals based on the transmission rate determined by the band allocation control unit. Or, a plurality of client signals from the client device are multiplexed into a high-speed optical signal and output to the wavelength demultiplexing unit,
The wavelength demultiplexing unit connected to the optical fiber connecting the plurality of WDM transmission apparatuses multiplexes the optical signal output from the OEO type demultiplexing unit in the wavelength region, and sends the multiplexed wavelength multiplexed signal to the optical fiber. In addition, when receiving the wavelength multiplexed signal from the optical fiber, the wavelength multiplexed signal is separated in a wavelength region, and output to the OEO demultiplexing unit ,
Based on the polarization mode dispersion value of the optical fiber, when controlling the transmission speed of the transmission signal sent to the optical fiber, the transmission speed per wavelength when the polarization mode dispersion value of the optical fiber is x B
0.3 × 1 / B ≧ x
WDM transmission method characterized by determining to be

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