JP3771823B2

JP3771823B2 - Arbitrary wavelength conversion circuit and composite wavelength band distribution type arbitrary wavelength conversion circuit

Info

Publication number: JP3771823B2
Application number: JP2001258316A
Authority: JP
Inventors: 純山涌; 篤高田; 敏夫盛岡
Original assignee: Nippon Telegraph and Telephone Corp
Current assignee: Nippon Telegraph and Telephone Corp
Priority date: 2001-08-28
Filing date: 2001-08-28
Publication date: 2006-04-26
Anticipated expiration: 2021-08-28
Also published as: JP2003066498A

Description

【０００１】
【発明の属する技術分野】
本発明は、光ルータにおいて、非線形光学効果を用いて任意の波長への波長変換を行う任意波長変換回路に関する。特に、１または複数の波長チャネルを含む波長バンド単位に波長変換を行う任意波長変換回路に関する。
【０００２】
また、波長多重光信号から分波した複数の波長バンドをそれぞれ任意の波長バンドへ波長変換する複合波長バンド分配型任意波長変換回路に関する。
【０００３】
【従来の技術】
近年、インターネット等の普及により通信トラヒック需要が急増しており、これらを制御するルータには現状でＴbit/s のスループット、将来的には10〜100 Ｔbit/s のスループットが要求されている。現在のルータでは、光ファイバ伝送路からの光信号を入力段で光／電気変換し、電気信号による信号処理の後に出力段で電気／光変換し、各光ファイバ伝送路を介して次ノードに転送する構成になっている。このような信号処理では、電気回路の処理速度がボトルネックとなり、将来的には数十Ｔbit/s オーダの信号処理を実現することが困難になる。なお、１つの方策としてＬＳＩ回路の並列化による高速化が可能であるが、装置規模の増大を招くことになる。
【０００４】
また、将来的に多様化する通信需要や大規模化するネットワークを考えると、自律的に伝送リンクの空き波長領域を確保でき、リストレーションやプロビジョニング等を高速に実現できるＶＷＰ（Virtual Wavelength Path)ルーティング装置が必要になる。このキーデバイスとなる波長変換回路は、現在のところ上記のように光／電気変換により行われているので、その動作速度に限界がある。
【０００５】
以上の電気信号処理に代わり、光信号波長を利用した光信号処理によりルーティングする方法が検討されている。入力信号光は、信号処理単位（１または連続する複数の波長チャネル）で光フィルタにより分波され、スイッチング処理が行われる。この波長ルーティングでは、光信号の変調方式や伝送速度に依存せずに光信号のままでルーティングすることができるので、装置構成が簡単かつ小規模になり、将来の大容量化にも容易に対応することができる。
【０００６】
また、将来的にトラヒック需要が増大すると、同一送信対地への波長パス設定数は１本以上使用されることが予想され、複数の波長をまとめてルーティングする方法が有望視されている。この方法では、複数の波長チャネルを１つの波長パス群として扱い、光スイッチの１ポートを複数の波長チャネルで共有することにより、光スイッチ規模を縮小させることができる。
【０００７】
しかし、現状の光／電気変換による波長変換では、波長パス群内の各波長パスに対して波長変換装置を用意する必要がある。一方、光信号のまま行う波長変換では、波長パス群を一括に波長変換できるので、光／電気変換方式に比べて大幅に装置規模を削減でき、また変調方式や伝送速度に依存しない波長変換が可能となる。
【０００８】
図１６は、従来の光信号処理による波長変換回路の構成例を示す。図において、波長λs の信号光と波長λp の励起光をＷＤＭカプラ２で合波し、分散シフトファイバ（ＤＳＦ）３に入力して波長λc の四光波混合光を発生させ、光フィルタ（ＢＰＦ）９で波長λc の四光波混合光のみを分離して波長変換光として出力する構成である。
【０００９】
【発明が解決しようとする課題】
ところで、分散シフトファイバ３を用いた四光波混合による波長変換では、分散シフトファイバ３の零分散波長λ₀において位相整合が成立するので、図１７に示すようにλp ＝λ₀に設定することにより、励起光波長λp を中心として信号光波長λs と対称な位置に波長λc の波長変換光（四光波混合光）が得られる。このように波長変換回路では、分散シフトファイバ３の零分散波長λ₀が固定であるので、励起光波長λp も固定となり、励起光波長λp を中心として対称な位置への波長変換しかできないことになる。
【００１０】
また、高い光非線形性が期待さているＰＰＬＮ（Periodically Poled LiNbO₃)等の２次の光非線形媒質による光パラメトリック波長変換素子でも、その導波路上の分極反転グレーティングの周期により波長変換の中心波長が決定されるので、同様に任意波長への変換は困難である。
【００１１】
以上のように、分散シフトファイバやＰＰＬＮ等の光非線形媒質単体では、位相整合波長を中心として対称な位置への波長変換となるので、光ルータに必要とされる任意波長への波長変換は実現できない。なお、光ファイバ等を用いた波長変換回路において、仮に零分散フラット（任意の波長で零分散）ファイバが開発され、波長可変光源から任意の波長の励起光を入力可能な構成とすると、任意波長への波長変換が実現できそうである。しかし、複数の波長チャネルを含む波長バンド単位に波長変換を行おうとすると、入力波長チャネル間でも位相整合条件が満足され、チャネル間クロストークが問題となる。
【００１２】
本発明は、光ルータにおいて、１または複数の波長チャネルを含む波長バンド単位に、入力波長チャネル間のクロストークを発生させることなく、任意の波長バンドへの波長変換を行うことができる任意波長変換回路を提供することを目的とする。
【００１３】
また、本発明は、波長多重光信号から分波した複数の波長バンドをそれぞれ任意の波長バンドへ波長変換する複合波長バンド分配型任意波長変換回路を提供することを目的とする。
【００１４】
【課題を解決するための手段】
本発明の任意波長変換回路は、図１６に示す従来の波長変換回路の単一構成では波長変換後の波長バンドに制限があるので、従来の波長変換回路を波長変換単位として複数の波長変換単位を縦続に接続する構成とし、トータルで任意の波長バンドへの波長変換を可能とするものである。
【００１５】
図１は、本発明の任意波長変換回路の基本構成を示す。ここでは、Ｍ個（Ｍは４以上の整数）に分割された波長帯域を波長バンドＢ1 〜ＢM とし、その中の１つの波長バンドＢi （ｉは１〜Ｍの整数）を任意の波長バンドＢ1 〜ＢM へ波長変換する構成を示す。
【００１６】
図において、縦続に接続されるＮ個の波長変換単位１０−１〜１０−Ｎは、それぞれ図１６に示す従来の波長変換回路と同様の構成である。ただし、波長バンド数Ｍと波長変換単位の数Ｎの関係は
２^N≧Ｍ
である。また、各波長変換単位において光非線形媒質の位相整合波長と励起光源の励起光波長は同一に設定され、かつ各波長変換単位ごとにその波長が異なるように設定される。駆動回路２０は、各波長変換単位のオンオフ駆動制御を行い、駆動される波長変換単位の組み合わせ２^Nに応じて２^N種類の任意波長バンドへの波長変換が実現する。例えばＭ＝８とし、波長バンドＢ1 を任意の波長バンドＢ1 〜Ｂ8 へ波長変換する場合には、３段（Ｎ＝３）の波長変換単位１０−１〜１０−３を縦続に接続する構成とする。
【００１７】
本発明の複合波長バンド分配型任意波長変換回路は、入力する波長多重信号光をＭ個の波長バンドＢ1 〜ＢM に分離する波長バンド分離手段と、各波長バンドごとに、それぞれ任意の波長バンドＢ1 〜ＢM へ波長変換する上記のＮ段構成の波長変換単位を複数組と、各波長変換単位を個別に駆動制御する駆動回路とを備える。
【００１８】
【発明の実施の形態】
＜任意波長変換回路の実施形態の構成例＞
図２は、本発明の任意波長変換回路の実施形態の構成例を示す。ここではＭ＝８、Ｂ1 の入力波長バンドをＢ1 〜Ｂ8 の任意の波長バンドへ波長変換する構成例を示す。波長変換単位は３段で構成される。
【００１９】
図において、３段の波長変換単位１０−１〜１０−３は縦続に接続される。各波長変換単位１０−１〜１０−３は、励起光源１１と、信号光と励起光を合波する合波器１２と、合波光を入力する光非線形媒質１３と、光非線形媒質１３で発生した波長変換光を分離する波長分離手段１４により構成される。ここで、各波長変換単位１０−１〜１０−３において、光非線形媒質１３の位相整合波長λ₀₁〜λ₀₃と、励起光源１１の励起光波長λp1〜λp3はそれぞれ同一に設定され（λp1＝λ₀₁、λp2＝λ₀₂、λp3＝λ₀₃）、かつ各波長変換単位ごとに異なるように設定される。駆動回路２０は、隣接ノードから送信された制御信号（制御チャネル、光ラベル信号）を入力し、その情報に従って各波長変換単位１０−１〜１０−３の励起光源１１をオンオフ駆動制御するとともに、波長分離手段１４に透過波長を設定する。
【００２０】
２以上の波長チャネルで構成される波長バンドを四光波混合等の光パラメトリック波長変換で波長変換操作を行うと、波長バンド内の波長チャネル間クロストークが問題となる。しかし、本発明の構成では、各波長変換単位内の光非線形媒質１３として、位相整合波長（零分散波長）がそれぞれ異なるものを複数段構成で用いるので、波長変換時の波長バンド内の波長チャネル間クロストークを回避することができる。
【００２１】
＜波長変換単位１０の第１の構成例＞
図３は、波長変換単位１０の第１の構成例を示す。ここでは、光非線形媒質１３として３次の光非線形媒質である分散シフトファイバ（ＤＳＦ）３を用いる例を示す。コアを小さくすることにより高い光非線形性を有する分散シフトファイバ３を用いた場合には、ファイバ長２ｋｍ、励起光パワー50ｍＷで理論的に変換効率η（＝変換光パワー／信号光パワー）は100 ％となり、実用的なものとなる。励起光源１１が出力する励起光の波長λp と、分散シフトファイバ３の零分散波長λ₀は等しくなるように設定される（λp ＝λ₀）。合波器１２としてはＷＤＭカプラ２を用い、波長分離手段１４としては波長変換光または信号光の透過帯域が設定される波長可変フィルタ４を用いる。駆動回路２０は、励起光源１１をオンオフ駆動制御する制御信号を出力するとともに、波長可変フィルタ４の透過波長を設定する制御信号を出力する。
【００２２】
＜波長変換単位１０の第２の構成例＞
図４は、波長変換単位１０の第２の構成例を示す。ここでは、光非線形媒質１３として２次の光非線形媒質であるＰＰＬＮ（Periodically Poled LiNbO₃)５を用いる例を示す。その他の構成は、図３の第１の構成例と同様である。ただし、励起光源１１は、ＰＰＬＮ５の位相整合波長と等しい波長の励起光を出力する。
【００２３】
＜波長変換単位１０の第３の構成例＞
図５は、波長変換単位１０の第３の構成例を示す。ここでは、３段の波長変換単位１０−１〜１０−３のうち、１段目の波長変換単位１０−１と２段目の波長変換単位１０−２の波長分離手段１４として、信号光や波長変換光より強度が強く固定波長の励起光のみを取り除く励起光除去フィルタ（帯域除去フィルタ）６を用いる。そして、３段目の波長変換単位１０−３の波長分離手段１４として、所定の波長変換光のみを分離する波長可変フィルタ４を用いる。
【００２４】
この構成では、波長変換単位１０−１，１０−２の出力には、波長変換光とともに入力信号光が存在する。したがって、それぞれ次段の波長変換単位１０−２，１０−３では、前段の波長変換光とともに信号光に対する波長変換光も発生するが、最終的に波長変換単位１０−３の波長可変フィルタ４で必要な波長変換光（波長バンド）のみを切り出すことにより、励起光、信号光、他の波長変換光を取り除くことができる。
【００２５】
励起光除去フィルタ６は、各波長変換単位ごとに励起光波長が固定であるので除去帯域が固定のものを用いることができる。したがって、駆動回路２０は、波長変換単位１０−１〜１０−３の各励起光源１１をオンオフ駆動制御する制御信号を出力するとともに、波長変換単位１０−３に対してのみ波長可変フィルタ４の透過波長を設定する制御信号を出力する。
【００２６】
＜波長変換単位１０の第４の構成例＞
図６は、波長変換単位１０の第４の構成例を示す。ここでは、光非線形媒質１３として、特願２０００−３０４９３６に示される非線形マッハツェンダ干渉計構成の光パラメトリック回路７を用い、２つのポートから出力される信号光と波長変換光のいずれかを選択する出力光制御手段として２×１光スイッチ（ＳＷ）８を用いる。なお、光パラメトリック回路７は信号光と波長変換光が異なるポートに分離して出力される機能を有しており、その機能と２×１光スイッチ８によって、図２に示す波長分離手段１４に代わる機能を果たしている。
【００２７】
駆動回路２０は、励起光源１１をオンオフ駆動制御する制御信号を出力するとともに、２×１光スイッチ８を制御する制御信号を出力するが、１つの制御信号で対応することができる。例えば、駆動回路２０は、励起光オフの場合には信号光を出力させ、励起光オンの場合には波長変換光を出力させるように、励起光源１１および２×１光スイッチ８を同期制御する。
【００２８】
図７は、光パラメトリック回路７の基本構成を示す。図において、本光パラメトリック回路７は、内部の２つの光経路にそれぞれ光分散媒質と光非線形媒質を有する非線形マッハツェンダ干渉計６０により構成される。ただし、２つの光経路では、光分散媒質と２次の光非線形媒質の順番が逆になる。
【００２９】
信号光と励起光はＷＤＭカプラ２で合波され、その合波光が光合分波器６２の一方の入力ポートから入力され、２つの光経路に分岐される。一方の光経路に分岐された合波光は、最初に光分散媒質６３に入力され、次に２次の光非線形媒質６４に入力される。他方の光経路に分岐された合波光は、最初に２次の光非線形媒質６５に入力され、次に光分散媒質６６に入力される。２次の光非線形媒質６４，６５で発生する波長変換光と、２つの光経路を通過する信号光および励起光は光合分波器６７で合波され、一方の出力ポートに信号光および励起光が出力され、他方の出力ポートに波長変換光が出力される。すなわち、信号光と波長変換光の波長差が近接あるいは０でも、両者を分離して出力できる構成である。
【００３０】
図８は、光パラメトリック回路７の具体例を示す。ここでは非線形マッハツェンダ干渉計６０全体がＬiＮbＯ₃基板７０上の光導波路で構成される。すなわち、光合分波器６２，６７、光分散媒質として用いる非疑似位相整合ＬiＮbＯ₃導波路７１，７２、２次の光非線形媒質として用いる疑似位相整合ＬiＮbＯ₃導波路７３，７４がモノリシックに構成される。さらに、光カスケーディングのための光非線形媒質として用いる疑似位相整合ＬiＮbＯ₃導波路７５，７６が設けられる。
【００３１】
また、本構成例では、非線形マッハツェンダ干渉計６０の光学長を調整するために、一方の疑似位相整合ＬiＮbＯ₃導波路７４に電圧を印加する電源７７を備える。この電源７７の制御により、非線形マッハツェンダ干渉計６０の出力ポートに信号光または波長変換光のいずれかを出力させることができる。すなわち、この光学長調整手段を出力光制御手段（図６に示す２×１光スイッチ８）として機能させることができる。例えば、駆動回路２０は、励起光オフの場合には信号光を出力させ、励起光オンの場合には波長変換光を出力させるように、励起光源１１および電源７７を同期制御する。
【００３２】
＜任意波長変換回路の実施形態の動作例＞
図９は、本発明の任意波長変換回路の実施形態（図２）の動作例を示す。なお、各波長変換単位１０−１〜１０−３は、図３に示す第１の構成例のものとして説明するが他の構成例のものでも同様である。また、各波長変換単位１０−１〜１０−３の励起光源１１の励起光波長λp1〜λp3と分散シフトファイバ３の零分散波長λ₀₁〜λ₀₃は、それぞれ等しくなるように設定されるが、その波長位置は図１０に示す波長バンドＢ1 〜Ｂ8 の境界の波長▲１▼〜▲７▼のいずれかに設定される。例えば波長バンドＢ1 と波長バンドＢ2 の境界の波長を▲１▼とする。
【００３３】
各波長変換単位１０−１〜１０−３に設定される励起光波長（零分散波長）は、入力波長バンド（被変換光）に応じて決まる。図１１は、入力波長バンドに対する各波長変換単位の励起光波長を示す。入力波長バンドがＢ1,Ｂ2 の場合には、波長変換単位１０−１〜１０−３の励起光波長λp1〜λp3（零分散波長λ₀₁〜λ₀₃）として、それぞれ波長▲１▼，▲２▼，▲４▼が設定される。入力波長バンドがＢ3,Ｂ4 の場合には、同様に励起光波長λp1〜λp3としてそれぞれ波長▲３▼，▲２▼，▲４▼が設定される。入力波長バンドがＢ5,Ｂ6 の場合には、同様に励起光波長λp1〜λp3としてそれぞれ波長▲５▼，▲６▼，▲４▼が設定される。入力波長バンドがＢ7,Ｂ8 の場合には、同様に励起光波長λp1〜λp3としてそれぞれ波長▲７▼，▲６▼，▲４▼が設定される。
【００３４】
ここでは、波長バンドＢ1 から波長バンドＢ5 に波長変換する場合について説明する。図９に示すように、波長変換単位１０−１〜１０−３には、それぞれ波長▲１▼，▲２▼，▲４▼が励起光波長λp1〜λp3（零分散波長λ₀₁〜λ₀₃）として設定され、駆動回路２０によりそれぞれオフオフ駆動制御される。駆動回路２０は、波長変換単位１０−２，１０−３の各励起光源１１をオンとし、波長変換単位１０−１〜１０−３の各波長可変フィルタ４の透過帯域をＢ1 ，Ｂ4 ，Ｂ5 に設定する。
【００３５】
波長変換単位１０−１では励起光源１１がオフであるので、波長バンドＢ1 の入力信号光は波長変換されずに通過する。波長変換単位１０−２では、波長バンドＢ1 は波長▲２▼に対して対称な波長バンドＢ4 へ波長変換され、透過帯域Ｂ4 の波長可変フィルタ４を介して波長変換された波長バンドＢ4 のみが出力される。波長変換単位１０−３では、波長バンドＢ4 は波長▲４▼に対して対称な波長バンドＢ5 へ波長変換され、透過帯域Ｂ5 の波長可変フィルタ４を介して波長変換された波長バンドＢ5 のみが出力される。以上により、波長バンドＢ1 から波長バンドＢ5 への波長変換が行われる。
【００３６】
波長バンドＢ1 〜Ｂ4 のいずれかからＢ1 〜Ｂ8 の任意の波長バンドへ波長変換する場合の各波長変換単位１０−１〜１０−３の制御例を表１に示す。また、波長バンドＢ5 〜Ｂ8 のいずれかからＢ1 〜Ｂ8 の任意の波長バンドへ波長変換する場合の各波長変換単位１０−１〜１０−３の制御例を表２に示す。なお、励起光源オンは励起光を出力する波長変換単位ごとにその波長▲１▼〜▲７▼で表示し、透過帯域は各波長変換単位の波長可変フィルタ４に設定される波長バンドを示す。
【００３７】
【表１】

【００３８】
【表２】

【００３９】
一般に、Ｍ個の波長バンドに対してＮ段の波長変換単位がもつ励起光波長λp1〜λpN（零分散波長λ₀₁〜λ_0N）は、次の関係式に基づいて決定することができる。
Ｍ＝２^N（Ｎは１以上の整数、Ｍは２以上の整数）
Ｂx ：入力波長バンド（ｘは１〜Ｍの整数）
ｙ：励起光の波長位置（ｙは１〜Ｍ−１の整数、図１０では▲１▼〜▲７▼で表示）
ｚ：波長変換単位の番号（ｚは１〜Ｎの整数）
各波長変換単位ｚにおいて、
ｘ＝２^zｎ−ｍ（ｎは１〜Ｍ／２^zの整数、ｍは０〜２^zの整数）
ｙ＝２^zｋ−２^(z-1)（ｋは１〜Ｍ／２^zの整数）
【００４０】
以上の関係式により、Ｍ＝16の場合における入力波長バンドＢx(Ｂ1 〜Ｂ16) に対して、４段の波長変換単位１０−１〜１０−４（ｚは１〜４）の励起光波長λp1〜λp4の波長位置ｙを図１２に示す。例えば、入力波長バンドＢ8 の場合には、波長変換単位１０−１〜１０−４の励起光波長λp1〜λp4の波長位置は、それぞれ▲７▼、▲６▼、▲４▼、▲８▼に設定すればよい。
【００４１】
＜複合波長バンド分配型任意波長変換回路の第１の実施形態＞
図１３は、複合波長バンド分配型任意波長変換回路の第１の実施形態を示す。ここでは、Ｍ＝８、Ｂ1 〜Ｂ8 の入力波長バンドをそれぞれＢ1 〜Ｂ8 の任意の波長バンドへ波長変換する構成例を示す。波長変換単位は３段で構成される。
【００４２】
図において、波長バンドＢ1 〜Ｂ8 を含む波長多重光は、波長バンド分離手段３０により各波長バンドＢ1 〜Ｂ8 に分離される。各波長バンドＢ1 〜Ｂ8 に対応して、それぞれ３段の波長変換単位１０−１１〜１０−１３、１０−２１〜１０−２３、…、１０−８１〜１０−８３が縦続に接続され、それぞれが駆動回路２０によりオンオフ駆動制御される。
【００４３】
各波長変換単位は、図３または図４に示すいずれかの構成をとる。すなわち、駆動回路２０は、各波長変換単位に対して、励起光源１１をオンオフ駆動制御する制御信号を出力するとともに、波長可変フィルタ４の透過波長を設定する制御信号を出力する。各波長変換単位に設定される励起光波長（零分散波長）は、図１１に示すように入力波長バンド（被変換光）に応じて決まる。図１３には、各波長変換単位に設定する励起光波長λp1〜λp3と、オンオフ状態および透過波長の設定例を示す。
【００４４】
＜複合波長バンド分配型任意波長変換回路の第２の実施形態＞
図１４は、複合波長バンド分配型任意波長変換回路の第２の実施形態を示す。
全体的な構成な図１３と同様であるが、ここに示す各波長変換単位は、図５に示す構成をとる。すなわち、駆動回路２０は、波長変換単位１０−１１〜１０−１３、１０−２１〜１０−２３、…、１０−８１〜１０−８３の各励起光源１１をオンオフ駆動制御する制御信号を出力するとともに、波長変換単位１０−１３、１０−２３、…、１０−８３に対してのみ波長可変フィルタ４の透過波長を設定する制御信号を出力する。
【００４５】
＜複合波長バンド分配型任意波長変換回路の第３の実施形態＞
図１５は、複合波長バンド分配型任意波長変換回路の第３の実施形態を示す。
全体的な構成な図１３と同様であるが、ここに示す各波長変換単位は、図６に示す構成をとる。すなわち、駆動回路２０は、波長変換単位１０−１１〜１０−１３、１０−２１〜１０−２３、…、１０−８１〜１０−８３に出力する制御信号により、各励起光源１１をオンオフ駆動制御するとともに、２×１光スイッチ８を制御する。すなわち、励起光オフの場合には信号光を出力させ、励起光オンの場合には波長変換光を出力させるように励起光源１１および２×１光スイッチ８を同期制御する。
【００４６】
【発明の効果】
以上説明したように、本発明の任意波長変換回路は、１または複数の波長チャネルを含む波長バンド単位に、入力波長チャネル間のクロストークを発生させることなく、任意の波長バンドへの波長変換を行うことができる。
【００４７】
また、本発明の複合波長バンド分配型任意波長変換回路は、波長多重光信号から分波した複数の波長バンドをそれぞれ任意の波長バンドへ波長変換することができる。
【図面の簡単な説明】
【図１】本発明の任意波長変換回路の基本構成を示すブロック図。
【図２】本発明の任意波長変換回路の実施形態を示すブロック図。
【図３】波長変換単位１０の第１の構成例を示す図。
【図４】波長変換単位１０の第２の構成例を示す図。
【図５】波長変換単位１０の第３の構成例を示す図。
【図６】波長変換単位１０の第４の構成例を示す図。
【図７】光パラメトリック回路７の基本構成を示す図。
【図８】光パラメトリック回路７の具体例を示す図。
【図９】任意波長変換回路の実施形態の動作例を説明する図。
【図１０】波長バンドと励起光の波長位置ｙの関係を示す図。
【図１１】入力波長バンドに対する各波長変換単位の励起光波長を示す図。
【図１２】４段の波長変換単位の励起光波長を示す図。
【図１３】複合波長バンド分配型任意波長変換回路の第１の実施形態を示す図。
【図１４】複合波長バンド分配型任意波長変換回路の第２の実施形態を示す図。
【図１５】複合波長バンド分配型任意波長変換回路の第３の実施形態を示す図。
【図１６】従来の光信号処理による波長変換回路の構成例を示す図。
【図１７】四光波混合による波長変換例を示す図。
【符号の説明】
２ＷＤＭカプラ
３分散シフトファイバ（ＤＳＦ）
４波長可変フィルタ
５ＰＰＬＮ
６励起光除去フィルタ
７光パラメトリック回路
８２×１光スイッチ
１０波長変換単位
１１励起光源
２０駆動回路
３０波長バンド分離手段
６０非線形マッハツェンダ干渉計
６２，６７光合分波器
６３，６６光分散媒質
６４，６５２次の光非線形媒質
７０ＬiＮbＯ₃基板７０
７１，７２非疑似位相整合ＬiＮbＯ₃導波路
７３，７４疑似位相整合ＬiＮbＯ₃導波路
７５，７６疑似位相整合ＬiＮbＯ₃導波路（光カスケーディング用）
７７電源[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an arbitrary wavelength conversion circuit that performs wavelength conversion to an arbitrary wavelength using a nonlinear optical effect in an optical router. In particular, the present invention relates to an arbitrary wavelength conversion circuit that performs wavelength conversion in units of wavelength bands including one or a plurality of wavelength channels.
[0002]
The present invention also relates to a composite wavelength band distribution type arbitrary wavelength conversion circuit that converts a plurality of wavelength bands demultiplexed from a wavelength multiplexed optical signal into arbitrary wavelength bands.
[0003]
[Prior art]
In recent years, the demand for communication traffic has increased rapidly due to the spread of the Internet and the like, and routers that control them are currently required to have a throughput of Tbit / s, and in the future, a throughput of 10 to 100 Tbit / s. In current routers, optical signals from optical fiber transmission lines are optically / electrically converted at the input stage, and after signal processing using electrical signals, electrical / optical conversion is performed at the output stage, and then sent to the next node via each optical fiber transmission line. It is configured to transfer. In such signal processing, the processing speed of the electric circuit becomes a bottleneck, and it will be difficult to realize signal processing on the order of several tens of Tbit / s in the future. One measure is to increase the speed by parallelizing LSI circuits, but this leads to an increase in the scale of the apparatus.
[0004]
In addition, considering future diversified communication demands and large networks, VWP (Virtual Wavelength Path) routing that can autonomously secure a vacant wavelength region of a transmission link and realize restoration and provisioning at high speed Equipment is required. Since the wavelength conversion circuit serving as the key device is currently performed by optical / electrical conversion as described above, its operation speed is limited.
[0005]
Instead of the above electric signal processing, a method of routing by optical signal processing using an optical signal wavelength has been studied. The input signal light is demultiplexed by an optical filter in signal processing units (one or a plurality of continuous wavelength channels), and switching processing is performed. In this wavelength routing, the optical signal can be routed as it is without depending on the modulation method and transmission speed of the optical signal, so the device configuration is simple and small-scale, and it can easily cope with future large capacity. can do.
[0006]
Further, when traffic demand increases in the future, it is expected that one or more wavelength paths set to the same transmission ground will be used, and a method of routing a plurality of wavelengths together is promising. In this method, a plurality of wavelength channels are handled as one wavelength path group, and one port of the optical switch is shared by the plurality of wavelength channels, so that the scale of the optical switch can be reduced.
[0007]
However, in the current wavelength conversion by optical / electrical conversion, it is necessary to prepare a wavelength conversion device for each wavelength path in the wavelength path group. On the other hand, in wavelength conversion performed as an optical signal, the wavelength path group can be wavelength-converted all at once, so the device scale can be greatly reduced compared to the optical / electrical conversion method, and wavelength conversion that does not depend on the modulation method or transmission speed. It becomes possible.
[0008]
FIG. 16 shows a configuration example of a wavelength conversion circuit using conventional optical signal processing. In the figure, signal light of wavelength λs and pumping light of wavelength λp are combined by a WDM coupler 2 and input to a dispersion shifted fiber (DSF) 3 to generate four-wave mixed light of wavelength λc, and an optical filter (BPF) 9 separates only the four-wave mixed light of wavelength λc and outputs it as wavelength-converted light.
[0009]
[Problems to be solved by the invention]
By the way, in the wavelength conversion by four-wave mixing using the dispersion shifted fiber 3, phase matching is established at the zero dispersion wavelength λ ₀ of the dispersion shifted fiber 3, so that by setting λp = λ ₀ as shown in FIG. Thus, wavelength-converted light (four-wave mixed light) having a wavelength λc is obtained at a position symmetrical to the signal light wavelength λs with the excitation light wavelength λp as the center. Thus, in the wavelength conversion circuit, since the zero dispersion wavelength λ ₀ of the dispersion shift fiber 3 is fixed, the pumping light wavelength λp is also fixed, and only wavelength conversion to a symmetric position with respect to the pumping light wavelength λp is possible. Become.
[0010]
In addition, even in an optical parametric wavelength conversion element using a second-order optical nonlinear medium such as PPLN (Periodically Poled LiNbO ₃ ), which is expected to have high optical nonlinearity, the center wavelength of wavelength conversion depends on the period of the polarization inversion grating on the waveguide. Similarly, conversion to an arbitrary wavelength is difficult.
[0011]
As described above, a single optical nonlinear medium such as a dispersion-shifted fiber or PPLN performs wavelength conversion to a symmetrical position with the phase matching wavelength as the center, thus realizing wavelength conversion to an arbitrary wavelength required for an optical router. Can not. In a wavelength conversion circuit using an optical fiber or the like, if a zero-dispersion flat (zero-dispersion at an arbitrary wavelength) fiber has been developed and an arbitrary wavelength pumping light can be input from a wavelength variable light source, an arbitrary wavelength It seems that wavelength conversion to can be realized. However, if wavelength conversion is performed in units of wavelength bands including a plurality of wavelength channels, the phase matching condition is satisfied even between the input wavelength channels, and interchannel crosstalk becomes a problem.
[0012]
The present invention provides an arbitrary wavelength conversion capable of performing wavelength conversion to an arbitrary wavelength band without generating crosstalk between input wavelength channels in units of wavelength bands including one or a plurality of wavelength channels in an optical router. An object is to provide a circuit.
[0013]
It is another object of the present invention to provide a composite wavelength band distribution type arbitrary wavelength conversion circuit that converts a plurality of wavelength bands demultiplexed from a wavelength multiplexed optical signal to arbitrary wavelength bands.
[0014]
[Means for Solving the Problems]
Since the arbitrary wavelength conversion circuit of the present invention has a limitation in the wavelength band after wavelength conversion in the single configuration of the conventional wavelength conversion circuit shown in FIG. 16, a plurality of wavelength conversion units using the conventional wavelength conversion circuit as a wavelength conversion unit. Are connected in cascade, and the total wavelength conversion to an arbitrary wavelength band is possible.
[0015]
FIG. 1 shows a basic configuration of an arbitrary wavelength conversion circuit of the present invention. Here, the wavelength band divided into M (M is an integer of 4 or more ) is defined as wavelength bands B1 to BM, and one of the wavelength bands Bi (i is an integer of 1 to M) is an arbitrary wavelength band B1. A configuration for wavelength conversion to .about.BM is shown.
[0016]
In the figure, N wavelength conversion units 10-1 to 10-N connected in cascade have the same configuration as the conventional wavelength conversion circuit shown in FIG. However, the relationship between the number M of wavelength bands and the number N of wavelength conversion units is 2 ^N ≧ M
It is. In each wavelength conversion unit, the phase matching wavelength of the optical nonlinear medium and the excitation light wavelength of the excitation light source are set to be the same, and the wavelength is set to be different for each wavelength conversion unit. The drive circuit 20 performs on / off drive control for each wavelength conversion unit, and realizes wavelength conversion into 2 ^N types of arbitrary wavelength bands according to the combination 2 ^N of wavelength conversion units to be driven. For example, when M = 8 and wavelength conversion of the wavelength band B1 to an arbitrary wavelength band B1 to B8, three stages (N = 3) of wavelength conversion units 10-1 to 10-3 are connected in cascade. To do.
[0017]
The composite wavelength band distribution type arbitrary wavelength conversion circuit of the present invention comprises wavelength band separation means for separating input wavelength multiplexed signal light into M wavelength bands B1 to BM, and an arbitrary wavelength band B1 for each wavelength band. A plurality of sets of wavelength conversion units having the above-described N-stage configuration for wavelength conversion to BM and a drive circuit that individually drives and controls each wavelength conversion unit.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
<Configuration Example of Embodiment of Arbitrary Wavelength Conversion Circuit>
FIG. 2 shows a configuration example of an embodiment of the arbitrary wavelength conversion circuit of the present invention. Here, a configuration example is shown in which the wavelength conversion of the input wavelength band of M = 8 and B1 to an arbitrary wavelength band of B1 to B8 is performed. The wavelength conversion unit is composed of three stages.
[0019]
In the figure, the three wavelength conversion units 10-1 to 10-3 are connected in cascade. Each of the wavelength conversion units 10-1 to 10-3 is generated in the pumping light source 11, the multiplexer 12 that combines the signal light and the pumping light, the optical nonlinear medium 13 that inputs the multiplexed light, and the optical nonlinear medium 13. The wavelength separation means 14 for separating the converted wavelength converted light. Here, in each of the wavelength conversion units 10-1 to 10-3, the phase matching wavelengths λ _{01 to} λ ₀₃ of the optical nonlinear medium 13 and the pumping light wavelengths λp1 to λp3 of the pumping light source 11 are set to be the same (λp1 = λ ₀₁ , λp 2 = λ ₀₂ , λp 3 = λ ₀₃ ) and are set differently for each wavelength conversion unit. The drive circuit 20 receives a control signal (control channel, optical label signal) transmitted from an adjacent node, and performs on / off drive control of the excitation light sources 11 of the wavelength conversion units 10-1 to 10-3 according to the information. A transmission wavelength is set in the wavelength separation means 14.
[0020]
When a wavelength conversion operation is performed on a wavelength band composed of two or more wavelength channels by optical parametric wavelength conversion such as four-wave mixing, crosstalk between wavelength channels within the wavelength band becomes a problem. However, in the configuration of the present invention, as the optical nonlinear medium 13 in each wavelength conversion unit, those having different phase matching wavelengths (zero dispersion wavelengths) are used in a multistage configuration, so that the wavelength channel in the wavelength band at the time of wavelength conversion Inter-crosstalk can be avoided.
[0021]
<First Configuration Example of Wavelength Conversion Unit 10>
FIG. 3 shows a first configuration example of the wavelength conversion unit 10. Here, an example is shown in which a dispersion-shifted fiber (DSF) 3 that is a third-order optical nonlinear medium is used as the optical nonlinear medium 13. When the dispersion shifted fiber 3 having high optical nonlinearity by reducing the core is used, the conversion efficiency η (= converted light power / signal light power) is theoretically 100 with a fiber length of 2 km and a pumping light power of 50 mW. %, Which is practical. The wavelength λp of the excitation light output from the excitation light source 11 and the zero dispersion wavelength λ ₀ of the dispersion shifted fiber 3 are set to be equal (λp = λ ₀ ). The WDM coupler 2 is used as the multiplexer 12, and the wavelength tunable filter 4 in which the transmission band of wavelength-converted light or signal light is set is used as the wavelength separator 14. The drive circuit 20 outputs a control signal for controlling the on / off drive of the excitation light source 11 and a control signal for setting the transmission wavelength of the wavelength tunable filter 4.
[0022]
<Second Configuration Example of Wavelength Conversion Unit 10>
FIG. 4 shows a second configuration example of the wavelength conversion unit 10. Here, an example in which a PPLN (Periodically Poled LiNbO ₃ ) 5 that is a second-order optical nonlinear medium is used as the optical nonlinear medium 13 is shown. Other configurations are the same as those of the first configuration example of FIG. However, the excitation light source 11 outputs excitation light having a wavelength equal to the phase matching wavelength of the PPLN 5.
[0023]
<Third Configuration Example of Wavelength Conversion Unit 10>
FIG. 5 shows a third configuration example of the wavelength conversion unit 10. Here, among the three-stage wavelength conversion units 10-1 to 10-3, as the wavelength separation means 14 of the first-stage wavelength conversion unit 10-1 and the second-stage wavelength conversion unit 10-2, signal light or An excitation light removal filter (band removal filter) 6 that removes only excitation light having a stronger intensity than wavelength-converted light and a fixed wavelength is used. The wavelength tunable filter 4 that separates only predetermined wavelength-converted light is used as the wavelength separation means 14 of the third-stage wavelength conversion unit 10-3.
[0024]
In this configuration, the input signal light is present together with the wavelength converted light at the outputs of the wavelength conversion units 10-1 and 10-2. Therefore, in the wavelength conversion units 10-2 and 10-3 in the next stage, the wavelength conversion light for the signal light is generated together with the wavelength conversion light in the previous stage. By cutting out only the necessary wavelength converted light (wavelength band), the excitation light, signal light, and other wavelength converted light can be removed.
[0025]
As the excitation light removal filter 6, a filter having a fixed removal band can be used because the excitation light wavelength is fixed for each wavelength conversion unit. Therefore, the drive circuit 20 outputs a control signal for controlling the on / off drive of the respective excitation light sources 11 of the wavelength conversion units 10-1 to 10-3 and transmits the wavelength variable filter 4 only to the wavelength conversion unit 10-3. Outputs a control signal for setting the wavelength.
[0026]
<Fourth Configuration Example of Wavelength Conversion Unit 10>
FIG. 6 shows a fourth configuration example of the wavelength conversion unit 10. Here, an optical parametric circuit 7 having a nonlinear Mach-Zehnder interferometer configuration shown in Japanese Patent Application No. 2000-304936 is used as the optical nonlinear medium 13, and an output for selecting either signal light or wavelength converted light output from two ports is used. A 2 × 1 optical switch (SW) 8 is used as the light control means. The optical parametric circuit 7 has a function of separating and outputting the signal light and the wavelength-converted light to different ports, and the function and the 2 × 1 optical switch 8 are used for the wavelength separation means 14 shown in FIG. It plays an alternative function.
[0027]
The drive circuit 20 outputs a control signal for controlling the pumping light source 11 to be turned on and off, and outputs a control signal for controlling the 2 × 1 optical switch 8, but this can be dealt with by a single control signal. For example, the drive circuit 20 synchronously controls the excitation light source 11 and the 2 × 1 optical switch 8 so that signal light is output when the excitation light is off and wavelength-converted light is output when the excitation light is on. .
[0028]
FIG. 7 shows a basic configuration of the optical parametric circuit 7. In the figure, the present optical parametric circuit 7 includes a nonlinear Mach-Zehnder interferometer 60 having an optical dispersion medium and an optical nonlinear medium in two internal optical paths. However, in the two optical paths, the order of the light dispersion medium and the second-order optical nonlinear medium is reversed.
[0029]
The signal light and the pump light are combined by the WDM coupler 2, and the combined light is input from one input port of the optical multiplexer / demultiplexer 62 and branched into two optical paths. The combined light branched into one of the optical paths is first input to the light dispersion medium 63 and then input to the second-order optical nonlinear medium 64. The combined light branched into the other optical path is first input to the second-order optical nonlinear medium 65 and then input to the light dispersion medium 66. The wavelength-converted light generated in the second-order optical

nonlinear media

64 and 65 and the signal light and the pump light passing through the two optical paths are multiplexed by the optical multiplexer / demultiplexer 67, and the signal light and the pump light are output to one output port. Is output, and the wavelength-converted light is output to the other output port. That is, even if the wavelength difference between the signal light and the wavelength converted light is close or zero, both can be separated and output.
[0030]
FIG. 8 shows a specific example of the optical parametric circuit 7. Here, the entire nonlinear Mach-Zehnder interferometer 60 is constituted by an optical waveguide on the LiNbO ₃ substrate 70. That is, the optical multiplexer /

demultiplexers

62 and 67, the non-pseudo phase matching LiNbO ₃ waveguides 71 and 72 used as the optical dispersion medium, and the pseudo phase matching LiNbO ₃ waveguides 73 and 74 used as the second-order optical nonlinear medium are monolithically configured. The Furthermore, quasi phase matching LiNbO ₃ waveguides 75 and 76 used as an optical nonlinear medium for optical cascading are provided.
[0031]
Further, in this configuration example, in order to adjust the optical length of the nonlinear Mach-Zehnder interferometer 60, a power supply 77 for applying a voltage to one pseudo phase matching LiNbO ₃ waveguide 74 is provided. By controlling the power supply 77, either the signal light or the wavelength converted light can be output to the output port of the nonlinear Mach-Zehnder interferometer 60. That is, this optical length adjusting means can function as output light control means (2 × 1 optical switch 8 shown in FIG. 6). For example, the drive circuit 20 synchronously controls the excitation light source 11 and the power source 77 so that the signal light is output when the excitation light is off and the wavelength converted light is output when the excitation light is on.
[0032]
<Operation Example of Embodiment of Arbitrary Wavelength Conversion Circuit>
FIG. 9 shows an operation example of the embodiment (FIG. 2) of the arbitrary wavelength conversion circuit of the present invention. In addition, although each wavelength conversion unit 10-1 to 10-3 is demonstrated as a thing of the 1st structural example shown in FIG. 3, the thing of another structural example is also the same. Also, the zero-dispersion wavelength lambda ₀₁ to [lambda] ₀₃ wavelength of the excitation light λp1~λp3 the dispersion-shifted fiber 3 of the pumping light source 11 of the wavelength conversion units 10-1 to 10-3, but is set such that each becomes equal, The wavelength position is set to one of the wavelengths {circle around (1)} to {circle around (7)} at the boundaries of the wavelength bands B1 to B8 shown in FIG. For example, assume that the wavelength at the boundary between the wavelength band B1 and the wavelength band B2 is (1).
[0033]
The excitation light wavelength (zero dispersion wavelength) set in each of the wavelength conversion units 10-1 to 10-3 is determined according to the input wavelength band (converted light). FIG. 11 shows the excitation light wavelength of each wavelength conversion unit with respect to the input wavelength band. When the input wavelength bands of B1, B2, as the pumping light wavelength of the wavelength conversion unit 10-1~10-3 λp1~λp3 (zero-dispersion wavelength λ ₀₁ ~λ _03), each wavelength ▲ 1 ▼, ▲ 2 ▼ , (4) are set. When the input wavelength bands are B3 and B4, the wavelengths {circle around (3)}, {circle around (2)} and {circle around (4)} are set as the pumping light wavelengths λp1 to λp3, respectively. When the input wavelength bands are B5 and B6, the wavelengths {circle around (5)}, {circle around (6)} and {circle around (4)} are similarly set as the excitation light wavelengths λp1 to λp3, respectively. When the input wavelength bands are B7 and B8, the wavelengths {circle around (7)}, {circle around (6)} and {circle around (4)} are similarly set as the excitation light wavelengths λp1 to λp3.
[0034]
Here, the case where wavelength conversion from the wavelength band B1 to the wavelength band B5 will be described. As shown in FIG. 9, the wavelength conversion units 10-1 to 10-3, respectively wavelengths ▲ 1 ▼, ▲ 2 ▼, ▲ 4 ▼ pumping light wavelength Ramudapi1～ramudapi3 (zero-dispersion wavelength λ ₀₁ ~λ ₀₃₎ And the driving circuit 20 performs off-off driving control. The drive circuit 20 turns on the respective excitation light sources 11 of the wavelength conversion units 10-2 and 10-3, and sets the transmission bands of the wavelength variable filters 4 of the wavelength conversion units 10-1 to 10-3 to B1, B4, and B5. Set.
[0035]
Since the excitation light source 11 is off in the wavelength conversion unit 10-1, the input signal light in the wavelength band B1 passes through without being wavelength converted. In the wavelength conversion unit 10-2, the wavelength band B1 is converted into a wavelength band B4 that is symmetric with respect to the wavelength {circle around (2)}, and only the wavelength band B4 that is wavelength-converted through the wavelength variable filter 4 in the transmission band B4 is output. Is done. In the wavelength conversion unit 10-3, the wavelength band B4 is wavelength-converted into a wavelength band B5 that is symmetric with respect to the wavelength (4), and only the wavelength band B5 that is wavelength-converted through the wavelength variable filter 4 in the transmission band B5 is output. Is done. As described above, the wavelength conversion from the wavelength band B1 to the wavelength band B5 is performed.
[0036]
Table 1 shows a control example of each wavelength conversion unit 10-1 to 10-3 when wavelength conversion is performed from any one of the wavelength bands B1 to B4 to any wavelength band of B1 to B8. Table 2 shows a control example of the wavelength conversion units 10-1 to 10-3 when wavelength conversion is performed from any one of the wavelength bands B5 to B8 to any wavelength band of B1 to B8. The excitation light source ON is indicated by the wavelengths {circle around (1)} to {circle around (7)} for each wavelength conversion unit that outputs the excitation light, and the transmission band indicates the wavelength band set in the wavelength variable filter 4 of each wavelength conversion unit.
[0037]
[Table 1]

[0038]
[Table 2]

[0039]
Generally, the pumping light wavelength λp1~λpN having the wavelength conversion unit N stages for the M wavelength band (zero-dispersion wavelength λ ₀₁ ~λ _0N) can be determined in accordance with the following relationship.
M = 2 ^N (N is an integer of 1 or more, M is an integer of 2 or more)
Bx: Input wavelength band (x is an integer from 1 to M)
y: wavelength position of the excitation light (y is an integer from 1 to M-1, indicated by (1) to (7) in FIG. 10)
z: Number of wavelength conversion unit (z is an integer from 1 to N)
In each wavelength conversion unit z,
^{x = 2 z n-m (} n is an integer of 1~M / 2 ^z, m is an integer from 0 to 2 ^z)
y = 2 ^z k-2 ^(z-1) (k is an integer of ^{1 to} M / 2 ^z )
[0040]
From the above relational expression, for the input wavelength band Bx (B1 to B16) in the case of M = 16, four stages of wavelength conversion units 10-1 to 10-4 (z is 1 to 4) excitation light wavelengths λp1 The wavelength position y of ˜λp4 is shown in FIG. For example, in the case of the input wavelength band B8, the wavelength positions of the excitation light wavelengths λp1 to λp4 of the wavelength conversion units 10-1 to 10-4 are respectively (7), (6), (4), and (8). You only have to set it.
[0041]
<First Embodiment of Compound Wavelength Distribution Type Arbitrary Wavelength Conversion Circuit>
FIG. 13 shows a first embodiment of a composite wavelength band distribution type arbitrary wavelength conversion circuit. Here, a configuration example is shown in which M = 8 and the input wavelength bands of B1 to B8 are converted into arbitrary wavelength bands of B1 to B8, respectively. The wavelength conversion unit is composed of three stages.
[0042]
In the figure, wavelength multiplexed light including wavelength bands B1 to B8 is separated into wavelength bands B1 to B8 by the wavelength band separation means 30. Corresponding to each wavelength band B1 to B8, three stages of wavelength conversion units 10-11 to 10-13, 10-21 to 10-23, ..., 10-81 to 10-83 are connected in cascade, respectively. Is controlled to be turned on / off by the drive circuit 20.
[0043]
Each wavelength conversion unit has one of the configurations shown in FIG. 3 or FIG. That is, the drive circuit 20 outputs a control signal for controlling the excitation light source 11 to be turned on / off and outputs a control signal for setting the transmission wavelength of the wavelength tunable filter 4 for each wavelength conversion unit. The excitation light wavelength (zero dispersion wavelength) set for each wavelength conversion unit is determined according to the input wavelength band (converted light) as shown in FIG. FIG. 13 shows an example of setting the excitation light wavelengths λp1 to λp3, the on / off state, and the transmission wavelength set for each wavelength conversion unit.
[0044]
<Second Embodiment of Compound Wavelength Band Distribution Type Arbitrary Wavelength Conversion Circuit>
FIG. 14 shows a second embodiment of the composite wavelength band distribution type arbitrary wavelength conversion circuit.
Although the overall configuration is the same as in FIG. 13, each wavelength conversion unit shown here has the configuration shown in FIG. That is, the drive circuit 20 outputs a control signal for performing on / off drive control of each of the excitation light sources 11 of the wavelength conversion units 10-11 to 10-13, 10-21 to 10-23, ..., 10-81 to 10-83. At the same time, a control signal for setting the transmission wavelength of the wavelength tunable filter 4 is output only to the wavelength conversion units 10-13, 10-23,..., 10-83.
[0045]
<Third Embodiment of Compound Wavelength Distribution Type Arbitrary Wavelength Conversion Circuit>
FIG. 15 shows a third embodiment of the composite wavelength band distribution type arbitrary wavelength conversion circuit.
Although the overall configuration is the same as in FIG. 13, each wavelength conversion unit shown here has the configuration shown in FIG. That is, the drive circuit 20 performs on / off drive control of each excitation light source 11 according to a control signal output to the wavelength conversion units 10-11 to 10-13, 10-21 to 10-23, ..., 10-81 to 10-83. In addition, the 2 × 1 optical switch 8 is controlled. That is, the excitation light source 11 and the 2 × 1 optical switch 8 are synchronously controlled so that the signal light is output when the excitation light is off and the wavelength-converted light is output when the excitation light is on.
[0046]
【The invention's effect】
As described above, the arbitrary wavelength conversion circuit of the present invention performs wavelength conversion to an arbitrary wavelength band without generating crosstalk between input wavelength channels for each wavelength band including one or more wavelength channels. It can be carried out.
[0047]
In addition, the composite wavelength band distribution type arbitrary wavelength conversion circuit of the present invention can wavelength-convert a plurality of wavelength bands demultiplexed from the wavelength multiplexed optical signal to arbitrary wavelength bands.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of an arbitrary wavelength conversion circuit of the present invention.
FIG. 2 is a block diagram showing an embodiment of an arbitrary wavelength conversion circuit of the present invention.
FIG. 3 is a diagram showing a first configuration example of a wavelength conversion unit 10;
4 is a diagram showing a second configuration example of the wavelength conversion unit 10. FIG.
FIG. 5 is a diagram showing a third configuration example of the wavelength conversion unit 10;
6 is a diagram showing a fourth configuration example of the wavelength conversion unit 10. FIG.
7 is a diagram showing a basic configuration of an optical parametric circuit 7. FIG.
FIG. 8 is a diagram showing a specific example of the optical parametric circuit 7;
FIG. 9 is a diagram illustrating an operation example of an embodiment of an arbitrary wavelength conversion circuit.
FIG. 10 is a diagram showing a relationship between a wavelength band and a wavelength position y of excitation light.
FIG. 11 is a diagram showing excitation light wavelengths of respective wavelength conversion units with respect to an input wavelength band.
FIG. 12 is a diagram showing excitation light wavelengths in four stages of wavelength conversion units.
FIG. 13 is a diagram showing a first embodiment of a composite wavelength band distribution type arbitrary wavelength conversion circuit;
FIG. 14 is a diagram showing a second embodiment of a composite wavelength band distribution type arbitrary wavelength conversion circuit.
FIG. 15 is a diagram showing a third embodiment of a composite wavelength band distribution type arbitrary wavelength conversion circuit;
FIG. 16 is a diagram illustrating a configuration example of a wavelength conversion circuit using conventional optical signal processing.
FIG. 17 is a diagram showing an example of wavelength conversion by four-wave mixing.
[Explanation of symbols]
2 WDM coupler 3 Dispersion shifted fiber (DSF)
4 Tunable filter 5 PPLN
6 Excitation light removal filter 7 Optical parametric circuit 8 2 × 1 optical switch 10 Wavelength conversion unit 11 Excitation light source 20 Drive circuit 30 Wavelength band separation means 60 Nonlinear Mach-

Zehnder interferometer

62, 67 Optical multiplexer /

demultiplexer

63, 66

Optical dispersion medium

64, 65 Secondary optical nonlinear medium 70 LiNbO ₃ substrate 70
71, 72 Non-pseudo phase matching LiNbO ₃ waveguide 73, 74 Pseudo phase matching LiNbO ₃ waveguide 75, 76 Pseudo phase matching LiNbO ₃ waveguide (for optical cascading)
77 Power supply

Claims

The wavelength band divided into M (M is an integer of 4 or more ) is defined as wavelength bands B1 to BM, and one of the wavelength bands Bi (i is an integer of 1 to M) is converted to an arbitrary wavelength band B1 to BM. In an arbitrary wavelength conversion circuit for wavelength conversion,
Wavelength conversion units connected in cascade in N stages (2 ^N ≧ M, N is an integer of 2 or more ), and a drive circuit that individually drives and controls each wavelength conversion unit,
The wavelength conversion unit includes an excitation light source that outputs excitation light having a predetermined wavelength λ p by on / off drive control of the drive circuit, a multiplexing unit that combines input signal light and excitation light, and at the time of driving the excitation light source. An optical nonlinear medium that receives combined light from the combining means , generates wavelength-converted light at a position symmetrical to the input signal light around the excitation light wavelength λ p , and allows the input signal light to pass when the excitation light source is not driven And wavelength separation means for selecting and outputting a predetermined wavelength band under the control of the drive circuit,
The wavelength conversion units of the N stages are set such that the phase matching wavelength of the optical nonlinear medium and the pumping light wavelength of the pumping light source are the same, and the wavelength is set to be different for each wavelength conversion unit. Wavelength conversion into 2 ^N types of arbitrary wavelength bands according to the number ^2N of driving light source driving / non-driving combinations, and any of the wavelength bands B1 to BM for the signal light of the wavelength band Bi from the wavelength conversion unit at the final stage An arbitrary wavelength conversion circuit characterized in that the wavelength conversion light is output.

Among the wavelength conversion units connected in cascade with N stages, the wavelength separation means of at least the final wavelength conversion unit is configured to select one of the wavelength bands B1 to BM serving as wavelength conversion light as a transmission band. The arbitrary wavelength conversion circuit according to claim 1 .

The arbitrary wavelength conversion circuit according to claim 2 , wherein the wavelength separation unit of the wavelength conversion unit other than the transmission band set is configured to remove excitation light.

Instead of the optical nonlinear medium and wavelength separation means in the wavelength conversion unit, two output ports of the first optical multiplexer / demultiplexer with two inputs and two outputs and two of the second optical multiplexer / demultiplexer with two inputs and two outputs A non-linear Mach-Zehnder interferometer in which an optical dispersion medium and a second-order optical nonlinear medium are inserted in two optical paths respectively connecting the input port and the first optical multiplexer / demultiplexer and the second optical multiplexer / demultiplexer is provided. The first optical nonlinear medium is inserted next to the first optical dispersion medium in one optical path between the optical device and the second optical dispersion next to the second optical nonlinear medium in the other optical path. Inserting a medium, inputting the combined light from one input port of the first optical multiplexer / demultiplexer, outputting input signal light and pumping light from one output port of the second optical multiplexer / demultiplexer, An optical parameter that outputs wavelength-converted light for the input signal light from the other output port. Any wavelength converter according to claim 1, characterized in that it comprises a circuit, and an output light controlling means outputting light of said optical parametric circuit to select whether the wavelength-converted light whether the input signal light.

The arbitrary wavelength conversion circuit according to claim 1 , wherein the optical nonlinear medium is a second-order optical nonlinear medium or a third-order optical nonlinear medium.

The drive circuit is configured to receive a control signal (control channel, optical label signal) transmitted from an adjacent node, and individually drive and control each wavelength conversion unit according to the information. An arbitrary wavelength conversion circuit described in 1.

Wavelength band separating means for separating the input wavelength multiplexed signal light into the M wavelength bands B1 to BM;
2. A plurality of sets of wavelength conversion units having an N-stage configuration according to claim 1, wherein wavelength conversion is performed to arbitrary wavelength bands B1 to BM for each wavelength band.
A combined wavelength band distribution type arbitrary wavelength conversion circuit comprising: a drive circuit that individually drives and controls each wavelength conversion unit.

Wherein the drive circuit, is transmitted from the adjacent node the control signal (control channel, optical label signal) is input, according to claim 7, characterized in that the individually driven and controlled constituting the respective wavelength conversion unit according to the information A composite wavelength band distribution type arbitrary wavelength conversion circuit described in 1.