JP3582775B2 - Optical frequency filter - Google Patents

Description

【００２４】
尚、表１（ａ）はアレイ導波路格子フィルタ１の入出力光周波数の関係を、表１（ｂ）はアレイ導波路格子フィルタ３の入出力光周波数の関係を示した。
表１に示されるように、同一の入射ポートから信号が入射した場合、信号光の光周波数に応じて異なった出力ポートから出力され、また、同一光周波数の信号でも入力ポートが異なれば異なる出力ポートに出力されることとなる。
【００２５】
即ち、第一のアレイ導波路格子フィルタ１は、表１（ａ）に記載するように、一つの入射ポートに入射した信号を光周波数ｆ１〜２０に応じて四つの出力ポートへ透過させ、また、アレイ導波路格子フィルタ３は、表１（ｂ）に記載するように、四つの入射ポートに入射した信号を光周波数ｆ１〜ｆ２０に応じて五つの出力ポートへ透過させる。
【００２６】
アレイ導波路格子フィルタ１，３の透過特性を図２（ａ）及び（ｂ）にそれぞれ示す。
光ゲート・スイッチアレイ２及び４の光ゲート・スイッチ素子番号をそれぞれＡ１〜Ａ４、Ｂ１〜Ｂ５とし、光ゲート・スイッチＡ１及びＢ１を透過動作させ、それ以外の光ゲート・スイッチは遮断動作にある場合の透過特性は、第一のアレイ導波路格子フィルタ１では図２（ａ）で実線で示すように、ｆ１，ｆ５，ｆ９，ｆ１３，ｆ１７となり、また、第二のアレイ導波路格子フィルタ３では図２（ｂ）で実線で示すように、ｆ１，ｆ６，ｆ１１，ｆ１６となる。
【００２７】
つまり、第一のアレイ導波路格子フィルタ１では、図２（ａ）に示されるようにチャネル間隔３つおきに周期的に透過周波数帯が生じ、図中Ａ１〜Ａ４で示す光周波数を有する信号光がそれぞれ出力ポート１〜４に分波される。
更に、光ゲート・スイッチＡ１のみを透過動作させることにより、図１中実線で示される周波数の信号光が、図１中一番上の導波路から第二のアレイ導波路格子フィルタ３に入射する。
光ゲート・スイッチＡ２〜Ａ４はＯＦＦされているため、第二のアレイ導波路格子フィルタ３の他の入射導波路からは信号光は入射しない。
【００２８】
光ゲート・スイッチＡ１を透過し、第二のアレイ導波路格子フィルタ３から出力される信号光は図２（ｂ）に示されるようにチャネル間隔４つおきに周期的に透過周波数帯が生じ、図中Ｂ１〜Ｂ５で示す光周波数を有する信号光がそれぞれ五つの出力ポートに分波される。
光ゲート・スイッチＢ１を透過動作させることにより、実線で示すようなチャネル間隔４つおきの周期的な透過周波数帯が生じる。
その結果、後段の光ゲート・スイッチアレイ４からの出力は、両者の透過特性を掛け合わせたものとなる。
【００２９】
つまり、図２（ｃ）に示されるような周波数ｆ１を有する信号光が図１中一番上の導波路から光合流回路５に入射すると、光ゲート・スイッチＢ２〜Ｂ５はＯＦＦされているため、光合流回路５の他の入力導波路からは信号光は入射しない。
光合流回路５からの出力信号がこのフィルタの透過特性となり、図２（ｃ）に示すように、２０チャネル（＝４×５）おきに透過周波数帯が生じるものとなる。
この光周波数フィルタは２０チャネルの中から任意の周波数を選択できるフィルタとして用いることができる。
【００３０】
前後の光ゲート・スイッチアレイ２及び４の動作光ゲートの組み合わせを替えれば、他の１９チャネルの中から任意のチャネルを選択することは、これらの図及び表１より容易に理解することができる。
よって、このフィルタを用いることにより、周波数間隔１００ＧＨｚで等間隔に配列した２０の光周波数成分を持つ光の中から、任意の１つの光を取り出すことが可能である。
取り出される光周波数と電流を流して光を透過させるゲートとの対応表を表１に示す。
【００３１】
本実施例では、２つの光周波数選択フィルタの動作ゲートの組み合わせにより、１９１．０ＴＨｚから１９２．９ＴＨｚまでの周波数範囲内の２０周波数チャネルから任意のチャネルの光を取り出すことができる。
尚、制御しなければならない電極数は、９となっている。
従来の光周波数フィルタの構成では、２０チャネルの中から任意の周波数を選択できるフィルタには２０の光ゲート・スイッチの制御を要するが、本構成のフィルタでは、９（＝５＋４）の光ゲート・スイッチの制御をすればよく、電極数を著しく減少させることができることがわかる。
【００３２】
必要な周波数チャネルの数がより大きくなればなるほど、本発明による構成により、電極数の削減効果が大きくなることは明らかである。
本実施例では光ゲート・スイッチとして光アンプを用いた場合について説明したが、光の透過率を変化させることのできる他のデバイス、例えば吸収型変調器、グレーティング反射器等を用いた場合についても全く同様の効果が期待できる。
また、光合流回路５として、５入力１出力の場合について説明したが、Ｎ入力Ｍ出力のものを用いることも可能である。
また、本実施例の入力側、出力側を逆にした構成でも同様な効果が得られることは言うまでもない。
【００３３】
〔実施例２〕
本発明の第２の実施例を図３に示す。
本実施例は、チャネル数４、ＦＳＲがチャネル間隔の４倍のアレイ導波路格子フィルタ７と、チャネル数５、ＦＳＲがチャネル間隔の５倍のアレイ導波路格子フィルタ１１を用いた場合の２０チャネルの光周波数フィルタに関する。
【００３４】
図中、７はチャネル数４、ＦＳＲがチャネル間隔の４倍のアレイ導波路格子フィルタ、８は４チャネルの光ゲート・スイッチアレイ、９は４入力５出力の光合流分配回路、１０は５チャネルの光ゲート・スイッチアレイ、１１はチャネル数５、ＦＳＲがチャネル間隔の５倍のアレイ導波路格子フィルタ、１２は光ゲート制御用電極である。
【００３５】
ＩｎＰ半導体基板上に多数の光導波路が形成され、アレイ導波路格子フィルタ部分７及び１１の導波路のコア層は、バンドギャップ波長１０５０ｎｍのＩｎＧａＡｓＰで形成されている。
光ゲート・スイッチとして用いる半導体アンプ部８及び１０の導波路層の組成は、バンドギャップ波長１５５０〜１５８０ｎｍのＩｎＧａＡｓＰであり、波長１５５０ｎｍ（光周波数：〜１９３ＴＨｚ）付近の光に対して、吸収或いは増幅作用を持つ。
【００３６】
半導体アンプの上部に形成される光ゲート制御用電極１２と基板の裏面に形成される電極との間に電圧を制御し、半導体アンプの導波路層に流れる電流をＯＮ／ＯＦＦ動作させることにより、光を透過／遮断の制御が行われる。
第一のアレイ導波路格子フィルタ７では、周波数チャネル間隔１００ＧＨｚ、ＦＳＲ４００ＧＨｚ、チャネル数４となるように、アレイ導波路、スラブ導波路、入出力導波路が配置されている。
【００３７】
第二のアレイ導波路格子フィルタ１１では、周波数チャネル間隔１００ＧＨｚ、ＦＳＲ５００ＧＨｚ、チャネル数５となるように、アレイ導波路、スラブ導波路、入出力導波路が配置されている。
ここで、本実施例に係る光周波数フィルタの動作について説明する。
本実施例における各アレイ導波路格子フィルタ７，１１の入出力光周波数の関係を表２（ａ）及び（ｂ）にそれぞれ示す。
【００３８】
【表２】

【００３９】
尚、表２（ａ）はアレイ導波路格子フィルタ７の入出力光周波数の関係を、表２（ｂ）はアレイ導波路格子フィルタ１１の入出力光周波数の関係を示した。
即ち、光周波数選択フィルタ７は、表２（ａ）に記載するように、一つの入射ポートに入射した信号を光周波数ｆ１〜２０に応じて四つの出力ポートへ透過させ、また、アレイ導波路格子フィルタ３は、表１（ｂ）に記載するように、五つの入射ポートに入射した信号を一つの出力ポートへ透過させる。
【００４０】
いま、光ゲート・スイッチアレイ８及び１０の光ゲート・スイッチ素子番号をそれぞれＡ１〜Ａ４、Ｂ１〜Ｂ５とし、信号光が第一のアレイ導波路格子フィルタ７に一番上の導波路から入射したとする。
光ゲート・スイッチＡ１のみを透過動作させることにより、図２中実線で示される周波数の信号光が、図中一番上の導波路から４入力５出力の光合流分配回路９に入射する。
【００４１】
光ゲート・スイッチＡ２〜Ａ４はＯＦＦされているため、光合流分配回路９の他の入射導波路からは信号光は入射しない。
光ゲート・スイッチＡ１を透過して光合流分配回路９に入射した信号光は光合流分配回路９により分岐され、５チャネルの光ゲート・スイッチアレイ１０に入射する。
【００４２】
いま、光ゲート・スイッチアレイ１０のうち光ゲート・スイッチＢ１のみを透過動作させることにより、信号は一つの入力ポートからのみ第二のアレイ導波路格子フィルタ１１に入射し、出力信号は実線で示すようなチャネル間隔４つおきの周期的な透過周波数帯が生じる。
【００４３】
即ち、光ゲートスイッチアレイ１０を透過し、第二のアレイ導波路格子フィルタ１１から出力される信号光は、表２（ｂ）に示すように周波数ｆ１，ｆ６，ｆ１１，ｆ１６であり、また、図２（ｂ）に示されるようにチャネル間隔４つおきに周期的に透過周波数帯が生じ、図中Ｂ１〜Ｂ５で示される光周波数を有する信号光がそれぞれ五つの入力ポートから入射した場合に出力ポートから出力が得られる。
その結果、第二のアレイ導波路格子フィルタ１１からの出力は、両者の透過特性を掛け合わせたものとなる。
つまり図２（ｃ）に示されるような周波数ｆ１を有する信号光が出力されることになる。
【００４４】
この出力信号が本実施例に示されるフィルタの透過特性となり、図２（ｃ）に示すように、２０チャネル（＝４×５）おきに透過周波数帯が生じるものとなる。
この光周波数フィルタは２０チャネルの中から任意の周波数を選択できるフィルタとして用いることができる。
前後の光ゲート・スイッチアレイ８及び１０の動作光ゲートの組み合わせを替えれば、他の１９チャネルの中から任意のチャネルを選択することは、これらの図及び表１より容易に理解することができる。
【００４５】
よって、このフィルタを用いることにより、周波数間隔１００ＧＨｚで等間隔に配列した２０の光周波数成分を持つ光の中から、任意の１つの光を取り出すことが可能である。
取り出される光周波数と電流を流して光を透過させるゲートとの対応表を表１に示す。
本実施例では、２つの光周波数選択フィルタの動作ゲートの組み合わせにより、１９１．０ＴＨｚから１９２．９ＴＨｚまでの周波数範囲内の２０周波数チャネルから任意のチャネルの光を取り出すことができる。
尚、制御しなければならない電極数は、９となっている。
【００４６】
更に、本実施例では光ゲート・スイッチとして光アンプを用いた場合について説明したが、光の透過率を変化させることのできる他のデバイス、例えば、吸収型変調器、グレーティング反射器等を用いた場合についても全く同様の効果が期待できる。
また光合流回路としてＮ入力Ｍ出力の場合について説明したが、入力ポート数、出力ポート数がそれぞれＮ、Ｍ以上であれば、同様の効果が期待できる。
また、本実施例の入力側、出力側を逆にした構成でも、同様な効果が得られることは言うまでもない。
【００４７】
上述した光合流回路５、光合流分配回路９として有力なものは、図５に示すようなＹ分岐型、スターカプラ型（ＡＷＧに使われている）および多モード干渉型である。
図５（ａ）は、Ｙ分岐型の光合流回路を多段接続して構成された４入力１出力の光合流回路であり、Ｙ字型に接続された導波路を伝搬する内に１本の出力導波路に導かれる。
【００４８】
図５（ｂ）は、スターカプラ型の光合流回路、図５（ｃ）はスターカプラ型の光合流分岐回路であり、入射信号光が左右方向の幅が十分に広い２次元伝搬領域をビーム状に広がりながら伝搬し、出力導波路に結合するもので、ビームの広がりの範囲内にある全ての出力導波路に出力される。
そのため、Ｎ入力Ｍ出力（Ｎ＝１，２，３，…、Ｍ＝１，２，３，…）の光合流分岐回路が容易に形成できる。
【００４９】
図５（ｄ）は多モード干渉型の光合流回路、図５（ｅ）は多モード干渉型の光合流分岐回路であり、入射信号光が多モードの伝搬を許容する多モード伝搬領域を伝搬する内にモード干渉により光強度の強い領域・弱い領域が生じ、光強度の強い領域に出力導波路を配置することによりＮ入力Ｍ出力（Ｎ＝１，２，３，…、Ｍ＝１，２，３．…）の光合流分岐回路が容易に形成できる。
【００５０】
本発明は光合流分配回路としてはこれらのほか、市販のファイバ型のカプラを用いることも勿論可能であり、また例えば方向性結合器を用いた３ｄＢカプラを多段に接続しても構わない。
極端な言い方をすれば、複数本の入力導波路（またはファイバ）が複教本の出力導波路（またはファイバ）とが信号光の伝搬方向に沿って同時に物理的或いは（レンズ等を介して）光学的に接続されていれば光合流分岐回路として動作する。
【００５１】
〔実施例３〕
本発明の第３の実施例を図６に示す。
本実施例は、入力光が１００ＧＨｚ間隔で２０個の周波数が多重された信号光の場合に適用した周波数フィルタに関する。
図中３１はチャネル数４、ＦＳＲがチャネル間隔の４倍のアレイ導波路格子フィルタ、また、３３はチャネル数５，ＦＳＲがチャネル間隔の５倍のアレイ導波路格子フィルタであり、第一のアレイ導波路格子フィルタ３１のチャネル間隔は第二のアレイ導波路素子フィルタ３３のＦＳＲと等しくなるように設定されている。
【００５２】
即ち、第一のアレイ導波路格子フィルタ３１では、周波数チャネル間隔５００ＧＨｚ、チャネル毎の透過帯域５００ＧＨｚ，ＦＳＲ２０００ＧＨｚ、チャネル数４となるように、アレイ導波路、スラブ導波路、入出力導波路が配置されており、第二のアレイ導波路格子フィルタ３３では、周波数チャネル間隔１００ＧＨｚ、チャネル毎の透過帯域１００ＧＨｚ，ＦＳＲ５００ＧＨｚ、チャネル数５となるように、アレイ導波路、スラブ導波路、入出力導波路が配置されている。
３２は４チャネルの光ゲート・スイッチアレイ、３４は５チャネルの光ゲート・スイッチアレイ、３５は５入力１出力の光合流回路、３６は電極である。
【００５３】
多数の光導波路がＩｎＰ半導体基板上に形成され、アレイ導波路格子フィルタ３１及び３３の導波路のコア層は、バンドギャップ波長１０５０ｎｍのＩｎＧａＡｓＰで形成されている。
光ゲート・スイッチとして用いる半導体アンプ部３２及び３４の導波路層の組成は、バンドギャップ波長１５５０〜１５８０ｎｍのＩｎＧａＡｓＰであり、波長１５５０ｎｍ（光周波数：〜１９３ＴＨｚ）付近の光に対して、吸収或いは増幅作用を持つ。
半導体アンプの上部に形成される電極３６と基板の裏面に形成される電極との間に電圧を制御し、半導体アンプの導波路層に流れる電流をＯＮ／ＯＦＦ動作させることにより、光を透過／遮断の制御が行われる。
【００５４】
ここで本実施例の素子の動作について説明する。
第一のアレイ導波路格子フィルタ３１のある入射ポートと第二のアレイ導波路格子フィルタ３３の各入射ポートから２０の周波数多重信号光が入射した場合の各アレイ導波路格子フィルタの入出力光周波数の関係を表３（ａ）及び（ｂ）にそれぞれ示す。
【００５５】
【表３】

【００５６】
表３（ａ）はアレイ導波路格子フィルタ３１について、表３（ｂ）はアレイ導波路格子フィルタ３３について、表３（ｃ）は第３の実施例の光周波数フィルタ全体について、入出力光周波数の関係を示している。
図６の光ゲート・スイッチアレイ３２及び３４の光ゲート・スイッチ素子番号をそれぞれＡ１〜Ａ４，Ｂ１〜Ｂ５とし、例として光ゲート・スイッチＡ１とＢ１を透過動作させ、それ以外の光ゲート・スイッチは遮断動作にある場合の透過特性を図７に示す。
図６の第一のアレイ導波路格子フィルタ３１では、図７（ａ）に示されるように、２０の周波数多重信号光が連続する５つの信号光が一組となって、それぞれ出力ポート１〜４に分波される。
【００５７】
光ゲート・スイッチＡ１を透過動作させることにより、図中実線で示される５つのｆ１〜ｆ５の周波数信号光が、図６中３２で一番上の導波路から第二のアレイ導波路格子フィルタ３３に入射する。
光ゲート・スイッチＡ２〜Ａ４はＯＦＦされているため、第二のアレイ導波路格子フィルタ３３の他の入射導波路からは信号光は入射しない。
次に、光ゲート・スイッチＡ１から入射し、第二のアレイ導波路格子フィルタ３３から出力される信号光は図７（ｂ）に示されるような透過特性を示し、実線で示すようなチャネル間隔５つおきの周期的な透過周波数帯が生じる。
ところで、前段の光ゲート・スイッチアレイ３２で選ばれたのはｆ１〜ｆ５だけなので後段の光ゲート・スイッチアレイ３４のＢ１に入射するのはｆ１のみである。
【００５８】
即ち、後段の光ゲート・スイッチアレイ３４からの出力は、両者の透過特性を掛け合わせた、つまり図７（ｃ）に示されるように、ｆ１の周波数を有する信号光が図中一番上の導波路から光合流回路３５に入射する。
光ゲート・スイッチＢ２〜Ｂ５はＯＦＦされているため、光合流回路５の他の入射導波路からは信号光は入射しない。
光合流回路５からの出力信号がこのフィルタの透過特性となり、図７（ｃ）に示すように、２０波（＝４×５）おきに透過周波数帯が生じるものとなる。
この光周波数フィルタは２０の周波数多重信号光の中から任意の周波数信号光を選択できるフィルタとして用いることができる。
前後の光ゲート・スイッチアレイ３２及び３４の動作光ゲートの組み合わせを替えれば、他の１９の周波数信号光の中から任意の信号光を選択することは、これらの図及び表３より容易に理解することができる。
【００５９】
よって、このフィルタを用いることにより、周波数間隔１００ＧＨｚで等間隔に配列した２０の光周波数成分を持つ光の中から、任意の１つの光を取り出すことが可能である。
取り出される光周波数と電流を流して光を透過させるゲートとの対応は、表３（ｃ）に示す通りである。
本実施例では、２つの光周波数フィルタの動作ゲートの組み合わせにより、１９１．０ＴＨｚから１９２．９ＴＨｚまでの周波数範囲内の２０の周波数多重信号光の中から任意の周波数信号の光を取り出すことができる。
なお、制御しなければならない電極数は、９となっている。
従来の光周波数フィルタの構成では、２０の周波数多重信号光の中から任意の周波数信号光を選択できるフィルタには２０の光ゲート・スイッチの制御を要するが、本構成のフィルタでは、９（＝５＋４）の光ゲート・スイッチの制御をすればよく、電極数を著しく減少させることができることがわかる。
【００６０】
必要な周波数チャネルの数がより大きくなればなるほど、本発明による構成により、電極数の削減効果が大きくなることは明らかである。
本実施例では光ゲート・スイッチとして光アンプを用いた場合について説明したが、光の透過率を変化させることのできる他のデバイス、例えば吸収型変調器、グレーティング反射器等を用いた場合についても全く同様の効果が期待できる。
また光合流回路としてＮ入力１出力の場合について説明したが、Ｎ入力Ｍ出力のものを用いることも可能である。
また、本実施例の第一及び第二アレイ導波路格子の透過特性を逆にした構成でも同様な効果が得られることは言うまでもない。
【００６１】
〔実施例４〕
本発明の第４の実施例を図８に示す。
本実施例は、入力光が１００ＧＨｚ間隔で２０個の周波数が多重された信号光の場合に適用した周波数フィルタに関する。
図中４１はチャネル数４，ＦＳＲがチャネル間隔の４倍のアレイ導波路格子フィルタ、また、５はチャネル数５，ＦＳＲがチャネル間隔の５倍のアレイ導波路格子フィルタであり、第一のアレイ導波路格子フィルタ４１のチャネル間隔は第二のアレイ導波路格子フィルタ４５のＦＳＲと等しくなるように設定されている。
【００６２】
即ち、第一のアレイ導波路格子フィルタ４１では、周波数チャネル間隔５００ＧＨｚ、チャネル間の透過帯域５００ＧＨｚ、ＦＳＲ２０００ＧＨｚ、チャネル数４となるように、アレイ導波路、スラブ導波路、入出力導波路が配置されており、第二のアレイ導波路格子フィルタ４５では、周波数チャネル間隔１００ＧＨｚ、チャネル毎の透過帯域１００ＧＨｚ，ＦＳＲ５００ＧＨｚ、チャネル数５となるように、アレイ導波路、スラフ導波路、入出力導波路が配置されている。
４２は４チャネルの光ゲート・スイッチアレイ、４３は４入力５出力の光合流分配回路、４４は５チャネルの光ゲート・スイッチアレイ、４６は電極である。多数の光導波路がＩｎＰ半導体基板上に形成され、アレイ導波路格子フィルタ４１及び４５の導波路のコア層は、バンドギャップ波長１０５０ｎｍのＩｎＧａＡｓＰで形成されている。
【００６３】
光ゲート・スイッチとして用いる半導体アンプ部４２及び４４の導波路層の組成は、バンドギャップ波長１５５０〜１５８０ｎｍのＩｎＧａＡｓＰであり、波長１５５０ｎｍ（光周波数：〜１９３ＴＨｚ）付近の光に対して、吸収或いは増幅作用を持つ。
半導体アンプの上部に形成される電極４６と基板の裏面に形成される電極との間に電圧を制御し、半導体アンプの導波路層に流れる電流をＯＮ／ＯＦＦ動作させることにより、光を透過／遮断の制御が行われる。
ここで本発明の素子の動作について説明する。
第一のアレイ導波路格子フィルタ４１のある入射ポートと第二のアレイ導波路格子フィルタ４５の各入射ポートから２０の周波数多重信号光が入射した場合の各アレイ導波路格子フィルタの入出力光周波数の関係を表４（ａ）及び（ｂ）にそれぞれ示す。
【００６４】
【表４】

【００６５】
表４（ａ）はアレイ導波路格子フィルタ４１について、表４（ｂ）はアレイ導波路格子フィルタ４５について、表４（ｃ）は第４の実施例の光周波数フィルタ全体について、入出力光周波数の関係を示している。
いま信号光が第一のアレイ導波路格子フィルタ４１のある入射ポートから入射したとする。
図８の光ゲート・スイッチアレイ４２及び４４の光ゲート・スイッチ素子番号を再度それぞれＡ１〜Ａ４，Ｂ１〜Ｂ５とし、例として光ゲート・スイッチＡ１とＢ１を透過動作させ、それ以外の光ゲート・スイッチは遮断動作にある場合の透過特性は先程同様図７のようになる。
【００６６】
光ゲート・スイッチＡ１を透過動作させることにより、図７（ａ）中実線で示される５つの周波数ｆ１〜ｆ５の信号光が、図８中一番上の導波路から４入力５出力の光合流分配回路４３に入射する。
光ゲート・スイッチＡ２〜Ａ４はＯＦＦされているため、光合流分配回路４３の他の入射導波路から他の信号光は入射しない。
光ゲート・スイッチＡ１から光合流分配回路４３に入射した信号光は光合流分配回路４３により分岐され、５チャネルの光ゲート・スイッチアレイ４４に入射する。
さて、第二のアレイ導波路格子フィルタ４５では出力ポートを一本のみ用いる。
出力される信号光は表４（ｂ）より、図７（ｂ）中Ｂ１〜Ｂ５で示される光周波数を有する信号光がそれぞれ入力ポート１〜５から入射した場合に出力ポートから出力が得られる。
【００６７】
本実施例では、光ゲート・スイッチアレイ４４のうち光ゲート・スイッチＢ１のみを透過動作させ、光ゲート・スイッチＢ２〜Ｂ５はＯＦＦされているため、信号は入力ポート１からのみ第二のアレイ導波路格子フィルタ４５に入射し、他の入射導波路からは信号光は入射しない。
この場合の透過特性は、図７（ｂ）の実線で示すようなチャネル間隔５つおきの周期的な透過周波数帯が生じる。
ところで、前段の光ゲート・スイッチアレイ４２で選ばれたのはｆ１〜ｆ５だけなので後段の光ゲート・スイッチアレイ４４のＢ１から入射して、第二のアレイ導波路格子４５の出力ポートから出力されるのはｆ１のみである。
その結果、第二のアレイ導波路格子４５の出力ポートからは、両者の透過特性を掛け合わせた、つまり図７（ｃ）に示されるように、ｆ１の周波数を有する信号光が第二のアレイ導波路格子４５の出力ポートから出力される。
【００６８】
この出力信号が本実施例に示されるフィルタの透過特性となり、図７（ｃ）に示すように、２０波（＝４×５）おきに透過周波数帯が生じるものとなる。
この光周波数フィルタは２０の周波数多重信号光の中から任意の周波数信号光を選択できるフィルタとして用いることができる。
前後の光ゲート・スイッチアレイ４２及び４４の動作光ゲートの組み合わせを替えれば、他の１９の周波数信号光の中から任意の信号光を選択することは、これらの図及び表４より容易に理解することができる。
よって、このフィルタを用いることにより、周波数間隔１００ＧＨｚで等間隔に配列した２０の光周波数成分を持つ光の中から、任意の１つの光を取り出すことが可能である。
取り出される光周波数と電流を流して光を透過させるゲートとの対応は、表４（ｃ）に示す通りである。
【００６９】
本実施例では、２つの光周波数フィルタの動作ゲートの組み合わせにより、１９１．０ＴＨｚから１９２．９ＴＨｚまでの周波数範囲内の２０の周波数多重信号光から任意の周波数の信号光を取り出すことができる。
なお、制御しなければならない電極数は、９となっている。
本実施例では光ゲート・スイッチとして光アンプを用いた場合について説明したが、光の透過率を変化させることのできる他のデバイス、例えば吸収型変調器、グレーティング反射器等を用いた場合についても全く同様の効果が期待できる。
また光合流回路としてＮ入力Ｍ出力の場合について説明したが、入力ポート数、出力ポート数がそれぞれＮ，Ｍ以上であれば同様の効果が期待できる。
また、本実施例の第一及び第二アレイ導波路格子の透過特性を逆にした構成でも同様な効果が得られることは言うまでもない。
【００７０】
〔実施例５〕
本発明の第５の実施例を図９に示す。
本実施例は、入力光が１００ＧＨｚ間隔で２０個の周波数が多重された信号光の場合に適用した周波数フィルタに関する。
図中５１は、チャネル数５、チャネル間隔１００ＧＨｚ、チャネル毎の透過帯域１００ＧＨｚ，ＦＳＲがチャネル間隔の５倍、即ち、５００ＧＨｚのアレイ導波路格子フィルタである。
５３はチャネル数４、チャネル間隔は５００ＧＨｚ、チャネル毎の透過帯域は第一のアレイ導波路格子フィルタ５１のチャネル間隔の３倍、即ち、３００ＧＨｚ、ＦＳＲがチャネル間隔の４倍、即ち、２０００ＧＨｚのアレイ導波路格子フィルタである。
【００７１】
ただし、第二のアレイ導波路格子５３のスラブ導波路との接合点における入力導波路の間隔を図１０のように第二のアレイ導波路格子フィルタ５３のチャネル間隔５００ＧＨｚと信号光の周波数間隔１００ＧＨｚを加えた分だけ（６００ＧＨｚ）ずらして配置する。
このとき、第二のアレイ導波路格子フィルタ５３の各入力ポートから多重信号光が入射すると、各光周波数信号はその周波数毎に図１１に示す焦点位置に対して分配される。
図１１では、このときの各入力ポートからの入射に対してｆ１からｆ２０の各光周波数信号と焦点位置の関係を示している（一点鎖線）。
【００７２】
この図を見ればわかるように２０の各信号は第二のアレイ導波路格子フィルタ５３の入力ポートを適当に選ぶことにより常に透過帯域の中心を通るようになる（図１１点線枠、図１２）。
表５（ａ）はアレイ導波路格子フィルタ５１について、表５（ｂ）はアレイ導波路格子フィルタ５８について、表５（ｃ）は第５の実施例の光周波数フィルタ全体について、入出力光周波数の関係を示している。
よって、透過特性としては表５（ｂ）のようになる。
【００７３】
【表５】

【００７４】
５２は５チャネルの光ゲート・スイッチアレイ、５４は４チャネルの光ゲート・スイッチアレイ、５５は４入力１出力の光合流回路、５６は電極である。
多数の光導波路がＩｎＰ半導体基板上に形成され、アレイ導波路格子フィルタ５１及び５３の導波路のコア層は、バンドギャップ波長１０５０ｎｍのＩｎＧａＡｓＰで形成されている。
光ゲート・スイッチとして用いる半導体アンプ部５２及び５４の導波路層の組成は、バンドギャップ波長１５５０〜１５８０ｎｍのＩｎＧａＡｓＰであり、波長１５５０ｎｍ（光周波数＝：〜１９３ＴＨｚ）付近の光に対して、吸収或いは増幅作用を持つ。
【００７５】
半導体アンプの上部に形成される電極５６と基板の裏面に形成される電極との間に電圧を制御し、半導体アンプの導波路層に流れる電流をＯＮ／ＯＦＦ動作させることにより、光を透過／遮断の制御が行われる。
ここで本発明の素子の動作について説明する。
図９の光ゲート・スイッチアレイ５２及び５４の光ゲート・スイッチ素子番号をそれぞれＡ１〜Ａ５，Ｂ１〜Ｂ４とし、例として光ゲート・スイッチＡ２とＢ１を透過動作させ、それ以外の光ゲート・スイッチは遮断動作にある場合を考える。
第一のアレイ導波路格子５２の入射ポートから入った多重光は、その周波数成分毎に光ゲート・スイッチＡ１〜Ａ５に表５（ａ）のように分配されて入る。
ここでＡ２をＯＮ，Ａ１，Ａ３〜Ａ５をＯＦＦとすると、第二のアレイ導波路格子５３の入力ポート２にはｆ２，ｆ７，ｆ１２，ｆ１７が入り、それ以外の入力ポートには信号が入らない。
【００７６】
第二のアレイ導波路格子５３の入力ポート２から入った上の４つの信号は、表５（ｂ）の透過特性に従い、光ゲート・スイッチＢ１〜Ｂ４にそれぞれｆ７，ｆ１２，ｆ１７，ｆ２が入る。
更にここで、光ゲート・スイッチＢ１をＯＮにし、それ以外の光ゲート・スイッチＢ２〜Ｂ５をＯＦＦにすると、ｆ７のみが５入力１出力の光合流回路５５に入り、最終的にこの光周波数フィルタから出力される光信号はｆ７となる。
なお、前後の光ゲート・スイッチアレイ４２及び４４の動作光ゲートの組み合わせを替えれば、他の１９の周波数信号光の中から任意の信号光を選択することは、これらの図及び表５より容易に理解することができる。
よって、このフィルタを用いることにより、周波数間隔１００ＧＨｚで等間隔に配列した２０の光周波数成分を持つ光の中から、任意の１つの光を取り出すことが可能である。
取り出される光周波数と電流を流して光を透過させるゲートとの対応は、表５（ｃ）に示す通りである。
【００７７】
本実施例では、２つの光周波数フィルタの動作ゲートの組み合わせにより、１９１．０ＴＨｚから１９２．９ＴＨｚまでの周波数範囲内の２０の周波数多重信号光から任意の周波数の信号光を取り出すことができる。
なお、制御しなければならない電極数は、９となっている。
また、従来、透過特性がガウス分布になるようなアレイ導波路格子を複数段構成すると、通る帯域は設計上の誤差等で、徐々に狭まる傾向にあったが、このように後段に広い透過帯域を持ったアレイ導波路格子を置き、選ばれる信号は後段のアレイ導波路格子の入力導波路のスラブ導波路接続点での配置の工夫により、常に透過帯域の中心を通るようにできる。
これによって、この狭帯域化を抑制する効果が期待できる。
【００７８】
本実施例では光ゲート・スイッチとして光アンプを用いた場合について説明したが、光の透過率を変化させることのできる他のデバイス、例えば吸収型変調器、グレーティング反射器等を用いた場合についても全く同様の効果が期待できる。
また光合流回路としてＮ入力Ｍ出力の場合について説明したが、入力ポート数、出力ポート数がそれぞれＮ，Ｍ以上であれば同様の効果が期待できる。
【００７９】
【発明の効果】
以上、実施例に基づいて詳細に説明したように本発明によれば、少ない電極数の制御で選択できる光周波数（波長）の数を著しく増加した光周波数フィルタを実現することが可能になる。
【図面の簡単な説明】
【図１】本発明の第１の実施例を表す構成図である。
【図２】図２（ａ）はアレイ導波路格子フィルタ１，７の透過スペクトルを、図２（ｂ）はアレイ導波路格子フィルタ３，１１の透過スペクトルを、図２（ｃ）は光周波数フィルタ全体の透過スペクトルを表したグラフである。
【図３】本発明の第２の実施例を表す構成図である。
【図４】従来例の構成図である。
【図５】光合流回路、光合流分配回路の具体例を示す構成図である。
【図６】本発明の第３の実施例を表す構成図である。
【図７】図７（ａ）はアレイ導波路格子フィルタ３１，４１について、図７（ｂ）はアレイ導波路格子フィルタ３３，４５について、図７（ｃ）は光周波数フィルタ全体について、透過スペクトルを表したグラフである。
【図８】本発明の第４の実施例を表す構成図である。
【図９】本発明の第５の実施例を表す構成図である。
【図１０】本発明の第５の実施例におけるアレイ導波路格子フィルタ５３の入力導波路の設計を示す説明図である。
【図１１】本発明の第５の実施例におけるアレイ導波路格子フィルタ５３の入出力光周波数の関係を示す説明図である。
【図１２】本発明の第５の実施例におけるアレイ導波路格子フィルタ５３の透過特性を示すグラフである。
【符号の説明】
１，３ アレイ導波路格子フィルタ
７，１１ アレイ導波路格子フィルタ
２，４，８，１０，１１ 半導体アンプ・ゲート・アレイ
５ 光合流回路
６，１２ 光ゲート制御用電極
９ 光合流分配回路
１３，１８ 入力光導波路
１６，２１ 出力光導波路
１４，１５，１９，２０ スラブ導波路
１７，２２ アレイ導波路
２３ 光ゲート制御用電極
２４ ＩｎＰ基板
３１，３３ アレイ導波路格子フィルタ
３２，３４ 半導体アンプ・ゲート・アレイ
３５，５５ 光合流回路
３６，４６，５６ 光ゲート制御用電極
４１，４５ アレイ導波路格子フィルタ
４２，４４ 半導体アンプ・ゲート・アレイ
４３ 光合流分配回路
５１，５３ アレイ導波路格子フィルタ
５２，５４ 半導体アンプ・ゲート・アレイ
１１０ アレイ導波路格子分波器
１１１ アレイ導波路格子合波器
１１２ 半導体アンプ・ゲート・アレイ
１２０ ＩｎＰ基板
１２１，１２６ 入力光導波路
１２５，１３０ 出力光導波路
１２２，１２４，１２７，１２９ スラブ導波路
１２３，１２８ アレイ導波路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical frequency filter. That is, the present invention relates to an integrated optical frequency filter used for optical communication, optical switching, optical information processing, optical measurement, and the like.
[0002]
[Prior art]
In order to realize large-capacity communication, development of wavelength-division multiplexing optical communication for multiplexing and transmitting optical signals having a plurality of different optical frequencies (wavelengths) on one optical fiber is being actively conducted.
An optical frequency filter capable of selectively extracting only an optical signal of a specific optical frequency (wavelength) from a multiplexed optical signal composed of a plurality of optical frequencies is an optical add / drop device, an optical cross connect device. It is indispensable for realizing an optical switch.
[0003]
An optical frequency filter in which a pair of arrayed waveguide grating filters and an optical gate switch are integrated can digitally and quickly select an optical frequency by turning on / off an electrical signal. Promising as a suitable filter for
As a reported example of an optical frequency filter in which a pair of arrayed waveguide grating filters and a semiconductor amplifier, gate, and switch are integrated on an InP semiconductor substrate, M.P. And Zirngible et al. (IEEE Photonics Technology Letters, vol. 6, pp. 513-515, 1994).
[0004]
Also, there is known an optical filter device in which two filters having different resolutions are connected in series on a semiconductor wafer (JP-A-6-250132).
In this optical filter device, electrical energy is supplied from a control circuit to a waveguide having a controllable transmittance that connects the components of the filter defined on the wafer, whereby the entire filter includes a plurality of optical filters. Tune to a predetermined one of the frequencies.
The application of such electrical energy creates a frequency selection path that can transmit one of the hundreds of selected optical frequencies across the region of the semiconductor medium.
[0005]
Here, the operating characteristics of the conventional optical frequency filter will be described with reference to the drawings.
FIG. 4 schematically illustrates a configuration when an optical frequency filter of eight channels is viewed from above.
This filter is composed of three regions: an arrayed waveguide grating splitter 110, an arrayed waveguide grating multiplexer 111, and a semiconductor amplifier array 112.
An optical waveguide is formed on an InP substrate 120, and has a structure in which an InGaAsP core layer having a band gap wavelength of 1050 nm is sandwiched between InP clad layers.
[0006]
Therefore, the light is transparent to light near the wavelength of 1550 nm (light frequency: up to 193 THz), is confined in the InGaAsP layer having a higher refractive index than InP, and propagates along the waveguide pattern. Go.
When the incident light 113 enters the input waveguide 121 of the first array grating splitter, the light is guided to the first slab waveguide 122.
In the slab waveguide 122, the light spreads at a certain angle because there is no confinement effect due to the refractive index in the direction parallel to the substrate.
This spread light is gradually coupled to the large number of array waveguides 123 and guided to the second slab waveguide 124.
[0007]
Light converges in the second slab waveguide 124 and couples into one of the plurality of output waveguides 125.
Here, a certain difference in length is provided between adjacent waveguides of the arrayed waveguide 123.
For this reason, in the plane between the second slab waveguide 124 and the output waveguide 125, the position where the light is converged changes depending on the frequency of the input light.
For example, if light of a certain frequency f1 is coupled to the first output waveguide, light having a different frequency by Δf will be coupled to the adjacent second output waveguide.
[0008]
That is, the first arrayed waveguide grating splitter functions to distribute light having different optical frequencies to a plurality of output waveguides according to the frequency.
On the other hand, the second arrayed waveguide grating combiner 111 includes an input waveguide 126, a first slab waveguide 127, an arrayed waveguide 128, a second slab waveguide 129, and an output waveguide 130. Has a symmetric structure in which the arrangement of the input waveguide 121 and the output waveguide 125 of the arrayed waveguide grating duplexer 110 is interchanged.
Therefore, the operation of the second arrayed waveguide grating multiplexer 111 can be understood by considering how light travels in the opposite direction in the description of the operation of the first arrayed waveguide grating splitter.
The second arrayed waveguide grating multiplexer 111 functions to combine the split light into one waveguide.
[0009]
Semiconductor amplifiers 112 are formed between the output waveguide 125 of the arrayed waveguide grating demultiplexer 110 and the input waveguide 126 of the arrayed waveguide grating multiplexer / demultiplexer 111, respectively.
The waveguide of the semiconductor amplifier 112 is made of InGaAsP having a band gap wavelength of 1550 to 1580 nm. When no current is injected, light near 1550 nm is absorbed, and when the current is injected, the light is amplified.
That is, the semiconductor amplifier 112 functions as a gate switch for blocking or transmitting light depending on the current ON / OFF.
Therefore, by passing a current through a specific semiconductor amplifier 112 to pass light, only a specific wavelength from the light split by the first arrayed waveguide grating splitter 110 is output to the output waveguide 130. It is possible to guide.
[0010]
The optical frequency filter having such a configuration has a feature that the optical frequency to be selected electrically can be switched at a high speed.
The design of the arrayed waveguide grating filter will be described below.
The frequency of light transmitted from a particular output waveguide of the arrayed waveguide grating filter is periodic.
The period of this frequency is called a free spectral range (FSR) and is determined by the following equation.
FSR = c / (n · ΔL)
Here, c is the speed of light, n is the effective refractive index of the arrayed waveguide, and ΔL is the difference in length between adjacent arrayed waveguides.
[0011]
That is, the FSR is determined by setting the length difference ΔL between the arrayed waveguides.
Further, the difference in transmission frequency between adjacent output waveguides, that is, the channel frequency interval Δf can be determined by the interval between the output waveguides, the length of the slab waveguide, and the FSR.
In the example shown in FIG. 4, the channel frequency interval Δf is 200 GHz, the number of channels (the number of output waveguides) is 8, the FSR is 1.6 THz, and the FSR is exactly the number of channels times the channel frequency interval. Is set to
This filter operates as an optical frequency filter that selects only light of an arbitrary frequency from eight multiplexed optical signals arranged at intervals of 200 GHz.
[0012]
[Problems to be solved by the invention]
In the above prior art, when the number of selectable optical frequencies is increased, an arrayed waveguide grating filter having a large number of output waveguides is required in proportion to the number, and the number of optical gates is also increased. As a result, the size of the element increases and the number of electrodes increases.
Increasing the element size causes a decrease in the number of elements that can be made from a unit wafer and a decrease in yield, and an increase in the number of electrodes leads to an increase in a wiring process for performing electric wiring and an increase in the scale of a control circuit. There was a problem.
SUMMARY OF THE INVENTION An object of the present invention is to solve the problem in the conventional example and provide an optical frequency filter that requires a small increase in the number of control electrodes even when the number of selectable optical frequencies increases.
[0013]
[Means for Solving the Problems]
The optical frequency filter according to claim 1 of the present invention that achieves the above object has an operation of splitting light incident on one input waveguide into at least two or more output waveguides for different optical frequencies. The split light is transmitted or blocked between the first arrayed waveguide grating filter and the second arrayed waveguide grating filter having the function of combining the split light into one waveguide. In an optical frequency filter connected with an optical gate switch, in the first and second arrayed waveguide grating filters, a difference in optical frequency to be split or multiplexed between adjacent output waveguides or input waveguides, The waveguides are arranged so that the so-called frequency channel spacing is equal in all the arrayed waveguide gratings, and the interval between the transmitted light frequency periodically generated in the first arrayed waveguide grating filter and the second array is determined. The difference in length between adjacent arrayed waveguides of the first arrayed waveguide grating filter and the second, so that the interval between transmitted light frequencies periodically generated in the waveguide grating filter differs by the frequency channel interval. The difference in length between adjacent arrayed waveguides of the arrayed waveguide grating filter is set to be a different value, and is further divided into at least two or more output waveguides of the second arrayed waveguide grating filter. An optical gate switch for transmitting or blocking the waved light is connected, and an optical merging circuit is connected to an output waveguide of the optical gate switch.
[0014]
An optical frequency filter according to a second aspect of the present invention that achieves the above object has an operation of splitting light incident on one input waveguide into at least two or more output waveguides for different optical frequencies. The split light is transmitted or blocked between the first arrayed waveguide grating filter and the second arrayed waveguide grating filter having the function of combining the split light into one waveguide. In an optical frequency filter connected with an optical gate switch, in the first and second arrayed waveguide grating filters, a difference in optical frequency to be split or multiplexed between adjacent output waveguides or input waveguides, The waveguides are arranged so that the so-called frequency channel spacing is equal in all the arrayed waveguide gratings, and the interval between the transmitted light frequency periodically generated in the first arrayed waveguide grating filter and the second array is determined. The difference in length between adjacent arrayed waveguides of the first arrayed waveguide grating filter and the second, so that the interval between transmitted light frequencies periodically generated in the waveguide grating filter differs by the frequency channel interval. The length difference between adjacent array waveguides of the arrayed waveguide grating filter is set to a different value, and further, an optical convergence / distribution circuit is connected to the output waveguide of the optical gate switch, An optical gate switch for transmitting or blocking the split light is connected to at least two or more output waveguides of the merging distribution circuit, and the output waveguide of the optical gate switch is a second arrayed waveguide grating filter. Are connected to different input waveguides.
[0015]
According to a third aspect of the present invention, there is provided an optical gate switch for transmitting or blocking light split by the first arrayed waveguide grating filter between two arrayed waveguide grating filters. In the optical frequency filter connected to the first arrayed waveguide grating filter, the difference between the optical frequencies split into adjacent output waveguides, the so-called frequency channel interval and the second arrayed waveguide grating filter periodically The waveguides are arranged so that the intervals of the generated transmitted light frequencies are equal, or, in the second arrayed waveguide grating filter, the difference between the optical frequencies split into adjacent output waveguides, so-called frequency channel spacing and The waveguides are arranged so that the intervals between the transmitted light frequencies periodically generated in the first arrayed waveguide grating filter are equal to each other. An optical gate switch for transmitting or blocking the demultiplexed light is connected to at least two or more output waveguides of the filter, and an optical combining circuit is connected to the output waveguide of the optical gate switch. Features.
[0016]
According to a fourth aspect of the present invention, there is provided an optical gate switch for transmitting or blocking light split by a first arrayed waveguide grating filter between two arrayed waveguide grating filters. In the optical frequency filter connected to the first arrayed waveguide grating filter, the difference between the optical frequencies split into adjacent output waveguides, the so-called frequency channel interval and the second arrayed waveguide grating filter periodically The waveguides are arranged so that the intervals of the generated transmitted light frequencies are equal, or, in the second arrayed waveguide grating filter, the difference between the optical frequencies split into adjacent output waveguides, so-called frequency channel spacing and The waveguides are arranged so that the intervals between the transmitted light frequencies periodically generated in the first arrayed waveguide grating filter are equal to each other. An optical converging / distributing circuit is connected to the force waveguide, and an optical gate switch for transmitting or blocking the distributed light is connected to at least two or more output waveguides of the optical converging / distributing circuit, Are connected to different input waveguides of the second arrayed waveguide grating filter.
[0017]
According to a fifth aspect of the present invention to achieve the above object, an optical gate switch for transmitting or blocking light split by the first arrayed waveguide grating filter between two arrayed waveguide grating filters. In the optical frequency filter, the optical frequency band transmitted through the output waveguide of the second arrayed waveguide grating filter is equal to or greater than the optical frequency band transmitted through the first arrayed waveguide grating filter and the first array. The difference between the optical frequencies that are set to be equal to or less than the interval of the transmitted light frequency that periodically occurs in the waveguide grating filter, and are divided into adjacent output waveguides in the second arrayed waveguide grating filter, so-called, The frequency channel interval and the interval of the transmitted light frequency periodically generated in the first arrayed waveguide grating filter are equal to each other in the output waveguide adjacent to the first arrayed waveguide grating filter. The input waveguides of the second arrayed waveguide grating filter are arranged so as to be shifted by the difference in the optical frequency, that is, the so-called frequency channel interval, and at least two or more outputs of the second arrayed waveguide grating filter are provided. An optical gate switch for transmitting or blocking the demultiplexed light is connected to the waveguide, and an optical convergence circuit is connected to an output waveguide of the optical gate switch.
[0018]
[Action]
In the present invention, the first array waveguide grating, the preceding stage optical gate switch array, the optical converging / distributing circuit, the latter stage optical gate switch array, and the second array waveguide grating are constituted, By appropriately designing the channel frequency interval between the waveguide grating filter and the subsequent arrayed waveguide grating filter and the FSR between them, or by setting the channel frequency of the preceding arrayed waveguide grating filter and the latter arrayed waveguide grating filter The feature is that the intervals are equal, and the FSR between them is different from each other by the channel interval.
A feature is that a large number of optical frequencies can be efficiently selected with fewer optical gate switches than the conventional method.
In the optical frequency filter according to the present invention, the number of optical frequencies that can be selected with a small number of electrodes can be significantly increased by selecting a combination of the optical gate switch in the preceding stage and the optical gate switch in the subsequent stage.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
[Example 1]
FIG. 1 shows a first embodiment of the present invention.
In the present embodiment, 20 channels of light are combined with an arrayed waveguide grating filter 1 having four channels and an FSR of four times the channel interval, and an arrayed waveguide grating filter 3 having five channels and an FSR of five times the channel interval. It relates to a frequency filter.
[0020]
In the figure, 1 is an arrayed waveguide grating filter having 4 channels and FSR is 4 times the channel interval, 2 is an optical gate switch array of 4 channels, 3 is 5 channels and the FSR is 5 times the channel interval. Waveguide grating filter, 4 is a 5-channel optical gate switch array, 5 is a 5-input, 1-output optical convergence circuit, and 6 is an optical gate control electrode.
A large number of optical waveguides are formed on the InP semiconductor substrate, and the core layers of the waveguides of the arrayed waveguide grating filter portions 1 and 3 are formed of InGaAsP having a band gap wavelength of 1050 nm.
[0021]
The composition of the waveguide layers of the semiconductor amplifier sections 2 and 4 used as the optical gate switch is InGaAsP having a band gap wavelength of 1550 to 1580 nm, and absorbs or amplifies light near the wavelength of 1550 nm (optical frequency: up to 193 THz). Has an action.
The voltage is controlled between the optical gate control electrode 6 formed on the semiconductor amplifiers 2 and 4 and the electrode formed on the back surface of the substrate, and the current flowing in the waveguide layer of the semiconductor amplifier is turned on / off. As a result, light transmission / blocking is controlled.
In the first arrayed waveguide grating filter 1, an arrayed waveguide, a slab waveguide, and an input / output waveguide are arranged so that the frequency channel interval is 100 GHz, the FSR is 400 GHz, and the number of channels is 4.
[0022]
In the second arrayed waveguide grating filter 3, an arrayed waveguide, a slab waveguide, and an input / output waveguide are arranged so that the frequency channel interval is 100 GHz, the FSR is 500 GHz, and the number of channels is 5.
Here, the operation of the optical frequency filter according to the present embodiment will be described.
The first arrayed waveguide grating filter 1 has four channels, the FSR has four times the channel spacing, the second arrayed waveguide grating filter 3 has five channels, and the FSR has five times the channel spacing. Tables 1 (a) and 1 (b) show the relationship between the input and output optical frequencies of each of the arrayed waveguide grating filters 1 and 3 when there is a channel spacing between them.
[0023]
[Table 1]

[0024]
Table 1 (a) shows the relationship between the input and output optical frequencies of the arrayed waveguide grating filter 1, and Table 1 (b) shows the relationship between the input and output optical frequencies of the arrayed waveguide grating filter 3.
As shown in Table 1, when a signal enters from the same input port, the signal is output from a different output port according to the optical frequency of the signal light. It will be output to the port.
[0025]
That is, as described in Table 1 (a), the first arrayed waveguide grating filter 1 transmits a signal incident on one incident port to four output ports according to the optical frequencies f1 to f20, and The array waveguide grating filter 3 transmits signals incident on the four incident ports to five output ports according to the optical frequencies f1 to f20, as described in Table 1 (b).
[0026]
FIGS. 2A and 2B show the transmission characteristics of the arrayed waveguide grating filters 1 and 3, respectively.
The optical gate switch element numbers of the optical gate switch arrays 2 and 4 are A1 to A4 and B1 to B5, respectively, and the optical gate switches A1 and B1 are operated to be transmitted, and the other optical gate switches are in the cutoff operation. In this case, the transmission characteristics of the first arrayed waveguide grating filter 1 are f1, f5, f9, f13, and f17, as shown by the solid line in FIG. In FIG. 2B, f1, f6, f11, and f16 are obtained as indicated by the solid lines in FIG.
[0027]
That is, in the first arrayed waveguide grating filter 1, as shown in FIG. 2 (a), a transmission frequency band is periodically generated at every three channel intervals, and a signal having an optical frequency indicated by A1 to A4 in the figure. Light is split into output ports 1-4, respectively.
Further, the signal light having the frequency indicated by the solid line in FIG. 1 is incident on the second arrayed waveguide grating filter 3 from the uppermost waveguide in FIG. .
Since the optical gate switches A2 to A4 are turned off, no signal light enters from the other incident waveguides of the second arrayed waveguide grating filter 3.
[0028]
As shown in FIG. 2B, the signal light transmitted through the optical gate switch A1 and output from the second arrayed waveguide grating filter 3 periodically has a transmission frequency band at every four channel intervals as shown in FIG. Signal lights having optical frequencies indicated by B1 to B5 in the drawing are respectively split into five output ports.
By causing the optical gate switch B1 to perform the transmission operation, a periodic transmission frequency band is generated at every fourth channel interval as shown by the solid line.
As a result, the output from the optical gate switch array 4 at the subsequent stage is obtained by multiplying the transmission characteristics of the two.
[0029]
That is, when the signal light having the frequency f1 as shown in FIG. 2C enters the optical converging circuit 5 from the uppermost waveguide in FIG. 1, the optical gate switches B2 to B5 are turned off. Signal light does not enter from the other input waveguides of the optical converging circuit 5.
The output signal from the optical convergence circuit 5 becomes the transmission characteristic of this filter, and as shown in FIG. 2C, a transmission frequency band occurs every 20 channels (= 4 × 5).
This optical frequency filter can be used as a filter that can select an arbitrary frequency from 20 channels.
[0030]
If the combination of the operating optical gates of the front and rear optical gate / switch arrays 2 and 4 is changed, selecting an arbitrary channel from the other 19 channels can be easily understood from these figures and Table 1. .
Therefore, by using this filter, it is possible to extract any one light from the light having 20 optical frequency components arranged at regular intervals at a frequency interval of 100 GHz.
Table 1 shows a correspondence table between the extracted light frequency and a gate that transmits light by passing a current.
[0031]
In this embodiment, by combining the operation gates of the two optical frequency selection filters, light of any channel can be extracted from 20 frequency channels within a frequency range from 191.0 THz to 192.9 THz.
The number of electrodes to be controlled is nine.
In the configuration of the conventional optical frequency filter, a filter capable of selecting an arbitrary frequency from among 20 channels requires control of 20 optical gate switches, but in the filter of this configuration, 9 (= 5 + 4) optical gate switches are required. It is found that the number of electrodes can be significantly reduced by controlling the switches.
[0032]
Obviously, the greater the number of required frequency channels, the greater the effect of reducing the number of electrodes with the arrangement according to the invention.
In the present embodiment, the case where an optical amplifier is used as the optical gate switch has been described. Exactly the same effect can be expected.
In addition, although the description has been given of the case where the optical convergence circuit 5 has five inputs and one output, an N-input and M-output circuit may be used.
It is needless to say that a similar effect can be obtained even when the input side and the output side of the present embodiment are reversed.
[0033]
[Example 2]
FIG. 3 shows a second embodiment of the present invention.
In this embodiment, 20 channels are used when an arrayed waveguide grating filter 7 having 4 channels and an FSR of 4 times the channel interval, and an arrayed waveguide grating filter 11 having 5 channels and an FSR of 5 times the channel interval Optical frequency filter.
[0034]
In the figure, 7 is an arrayed waveguide grating filter having 4 channels, FSR is 4 times the channel interval, 8 is a 4-channel optical gate switch array, 9 is a 4-input, 5-output optical convergence / distribution circuit, and 10 is 5 channels An optical gate switch array, 11 is an arrayed waveguide grating filter having 5 channels and an FSR of 5 times the channel interval, and 12 is an optical gate control electrode.
[0035]
A large number of optical waveguides are formed on an InP semiconductor substrate, and the core layers of the waveguides of the arrayed waveguide grating filter portions 7 and 11 are formed of InGaAsP having a band gap wavelength of 1050 nm.
The composition of the waveguide layers of the semiconductor amplifier sections 8 and 10 used as optical gate switches is InGaAsP having a band gap wavelength of 1550 to 1580 nm, and absorbs or amplifies light having a wavelength of about 1550 nm (optical frequency: up to 193 THz). Has an action.
[0036]
By controlling the voltage between the optical gate control electrode 12 formed on the upper part of the semiconductor amplifier and the electrode formed on the back surface of the substrate, and turning on / off the current flowing through the waveguide layer of the semiconductor amplifier, Light transmission / blocking is controlled.
In the first arrayed waveguide grating filter 7, an arrayed waveguide, a slab waveguide, and an input / output waveguide are arranged so that the frequency channel interval is 100 GHz, the FSR is 400 GHz, and the number of channels is 4.
[0037]
In the second arrayed waveguide grating filter 11, the arrayed waveguide, the slab waveguide, and the input / output waveguide are arranged such that the frequency channel interval is 100 GHz, the FSR is 500 GHz, and the number of channels is 5.
Here, the operation of the optical frequency filter according to the present embodiment will be described.
Tables 2 (a) and 2 (b) show the relationship between the input and output optical frequencies of each of the arrayed waveguide grating filters 7 and 11 in this embodiment.
[0038]
[Table 2]

[0039]
Table 2 (a) shows the relationship between the input and output optical frequencies of the arrayed waveguide grating filter 7, and Table 2 (b) shows the relationship between the input and output optical frequencies of the arrayed waveguide grating filter 11.
That is, as shown in Table 2 (a), the optical frequency selection filter 7 transmits a signal incident on one input port to four output ports according to the optical frequencies f1 to f20, As described in Table 1 (b), the grating filter 3 transmits signals incident on five incident ports to one output port.
[0040]
Now, the optical gate switch element numbers of the optical gate switch arrays 8 and 10 are A1 to A4 and B1 to B5, respectively, and the signal light enters the first arrayed waveguide grating filter 7 from the uppermost waveguide. And
By transmitting only the optical gate switch A1, signal light having the frequency indicated by the solid line in FIG. 2 is incident on the four-input / five-output optical merger / distributor 9 from the uppermost waveguide in the figure.
[0041]
Since the optical gate switches A2 to A4 are turned off, no signal light enters from the other incident waveguides of the optical convergence / distribution circuit 9.
The signal light that has passed through the optical gate switch A1 and entered the optical multiplexing / distributing circuit 9 is branched by the optical convergence / distributing circuit 9, and is incident on the 5-channel optical gate / switch array 10.
[0042]
Now, by allowing only the optical gate switch B1 of the optical gate switch array 10 to perform a transmission operation, a signal enters the second arrayed waveguide grating filter 11 from only one input port, and an output signal is indicated by a solid line. Such a periodic transmission frequency band occurs at every fourth channel interval.
[0043]
That is, the signal light transmitted through the optical gate switch array 10 and output from the second arrayed waveguide grating filter 11 has the frequencies f1, f6, f11, and f16 as shown in Table 2 (b). As shown in FIG. 2B, when a transmission frequency band is periodically generated at every fourth channel interval, signal light having optical frequencies indicated by B1 to B5 in the figure is input from each of five input ports. Output is obtained from the output port.
As a result, the output from the second arrayed waveguide grating filter 11 is obtained by multiplying the two transmission characteristics.
That is, a signal light having a frequency f1 as shown in FIG. 2C is output.
[0044]
This output signal becomes the transmission characteristic of the filter shown in this embodiment, and as shown in FIG. 2C, a transmission frequency band is generated every 20 channels (= 4 × 5).
This optical frequency filter can be used as a filter that can select an arbitrary frequency from 20 channels.
If the combination of the operating optical gates of the front and rear optical gate / switch arrays 8 and 10 is changed, selecting an arbitrary channel from the other 19 channels can be easily understood from these figures and Table 1. .
[0045]
Therefore, by using this filter, it is possible to extract any one light from the light having 20 optical frequency components arranged at regular intervals at a frequency interval of 100 GHz.
Table 1 shows a correspondence table between the extracted light frequency and a gate that transmits light by passing a current.
In this embodiment, by combining the operation gates of the two optical frequency selection filters, light of any channel can be extracted from 20 frequency channels within a frequency range from 191.0 THz to 192.9 THz.
The number of electrodes to be controlled is nine.
[0046]
Further, in this embodiment, the case where the optical amplifier is used as the optical gate switch has been described. However, other devices capable of changing the light transmittance, for example, an absorption type modulator, a grating reflector and the like are used. Exactly the same effect can be expected in this case.
Also, the case where the optical converging circuit has N inputs and M outputs has been described, but the same effect can be expected if the number of input ports and the number of output ports are N and M, respectively.
It is needless to say that a similar effect can be obtained even when the input side and the output side of this embodiment are reversed.
[0047]
The most promising optical converging circuits 5 and 9 are the Y-branch type, the star coupler type (used in AWG) and the multi-mode interference type as shown in FIG.
FIG. 5A shows a four-input one-output optical converging circuit configured by connecting Y-branch type optical converging circuits in multiple stages, and one of the light converging circuits propagates through a waveguide connected in a Y-shape. Guided to the output waveguide.
[0048]
FIG. 5 (b) shows a star coupler type optical merging circuit, and FIG. 5 (c) shows a star coupler type optical merging / branching circuit. The beam propagates while spreading in a shape, and is coupled to the output waveguide, and is output to all output waveguides within the range of beam spread.
Therefore, it is possible to easily form an optical converging / branching circuit having N inputs and M outputs (N = 1, 2, 3,..., M = 1, 2, 3,...).
[0049]
FIG. 5D shows a multi-mode interference type optical converging circuit, and FIG. 5E shows a multi-mode interference type optical converging / branching circuit, in which an incident signal light propagates in a multi-mode propagation region allowing multi-mode propagation. In the meantime, a mode where the light intensity is high and a region where the light intensity is high are generated due to the mode interference, and N output M outputs (N = 1, 2, 3,..., M = 1, 2, 3,...) Can be easily formed.
[0050]
In the present invention, besides these, a commercially available fiber-type coupler can be used as the optical multiplexing / distributing circuit. For example, a 3 dB coupler using a directional coupler may be connected in multiple stages.
To put it in extreme terms, a plurality of input waveguides (or fibers) and an output waveguide (or fiber) of a compound text are simultaneously physically or optically (via a lens or the like) along the propagation direction of signal light. If they are connected to each other, they operate as an optical merging / branching circuit.
[0051]
[Example 3]
FIG. 6 shows a third embodiment of the present invention.
The present embodiment relates to a frequency filter applied when input light is signal light in which 20 frequencies are multiplexed at 100 GHz intervals.
In the figure, 31 is an arrayed waveguide grating filter having four channels and FSR is four times the channel interval, and 33 is an arrayed waveguide grating filter having five channels and the FSR is five times the channel interval. The channel spacing of the waveguide grating filter 31 is set to be equal to the FSR of the second arrayed waveguide element filter 33.
[0052]
That is, in the first array waveguide grating filter 31, the array waveguide, the slab waveguide, and the input / output waveguide are arranged such that the frequency channel interval is 500 GHz, the transmission band for each channel is 500 GHz, the FSR is 2000 GHz, and the number of channels is 4. In the second array waveguide grating filter 33, the array waveguide, the slab waveguide, and the input / output waveguide are arranged so that the frequency channel interval is 100 GHz, the transmission band for each channel is 100 GHz, the FSR is 500 GHz, and the number of channels is 5. Have been.
32 is an optical gate switch array of 4 channels, 34 is an optical gate switch array of 5 channels, 35 is an optical convergence circuit of 5 inputs and 1 output, and 36 is an electrode.
[0053]
A number of optical waveguides are formed on an InP semiconductor substrate, and the core layers of the waveguides of the arrayed waveguide grating filters 31 and 33 are formed of InGaAsP having a band gap wavelength of 1050 nm.
The composition of the waveguide layers of the semiconductor amplifier sections 32 and 34 used as the optical gate switch is InGaAsP having a band gap wavelength of 1550 to 1580 nm, and absorbs or amplifies light near the wavelength of 1550 nm (optical frequency: １９193 THz). Has an action.
The voltage is controlled between the electrode 36 formed on the upper part of the semiconductor amplifier and the electrode formed on the back surface of the substrate, and the current flowing through the waveguide layer of the semiconductor amplifier is turned on / off to transmit / transmit light. Shutdown control is performed.
[0054]
Here, the operation of the element of this embodiment will be described.
Input / output optical frequency of each arrayed waveguide grating filter when 20 frequency multiplexed signal lights are incident from an input port of the first arrayed waveguide grating filter 31 and each input port of the second arrayed waveguide grating filter 33 Are shown in Tables 3 (a) and 3 (b), respectively.
[0055]
[Table 3]

[0056]
Table 3 (a) shows the arrayed waveguide grating filter 31, Table 3 (b) shows the arrayed waveguide grating filter 33, and Table 3 (c) shows the entire optical frequency filter of the third embodiment. Shows the relationship.
The optical gate switch element numbers of the optical gate switch arrays 32 and 34 in FIG. 6 are A1 to A4 and B1 to B5, respectively. For example, the optical gate switches A1 and B1 are operated in a transparent manner, and other optical gate switches are operated. FIG. 7 shows the transmission characteristics in the case of the shut-off operation.
In the first arrayed waveguide grating filter 31 of FIG. 6, as shown in FIG. 7A, five signal lights in which 20 frequency-multiplexed signal lights are continuous form a set, and output ports 1 to It is split into four.
[0057]
The transmission operation of the optical gate switch A1 causes the five frequency signal lights of f1 to f5 indicated by the solid lines in the figure to pass through the uppermost waveguide in FIG. Incident on.
Since the optical gate switches A2 to A4 are turned off, no signal light is incident from the other incident waveguides of the second arrayed waveguide grating filter 33.
Next, the signal light incident from the optical gate switch A1 and output from the second arrayed waveguide grating filter 33 has transmission characteristics as shown in FIG. 7 (b), and the channel spacing as shown by the solid line. Every fifth periodic transmission frequency band occurs.
By the way, since only f1 to f5 are selected in the optical gate switch array 32 in the former stage, only f1 is incident on B1 of the optical gate switch array 34 in the latter stage.
[0058]
That is, the output from the optical gate switch array 34 at the subsequent stage is obtained by multiplying the transmission characteristics of the two, that is, as shown in FIG. 7C, the signal light having the frequency f1 is at the top of the figure. The light enters the optical converging circuit 35 from the waveguide.
Since the optical gate switches B2 to B5 are turned off, no signal light enters from the other incident waveguides of the optical convergence circuit 5.
The output signal from the optical convergence circuit 5 becomes the transmission characteristic of this filter, and as shown in FIG. 7C, a transmission frequency band occurs every 20 waves (= 4 × 5).
This optical frequency filter can be used as a filter that can select an arbitrary frequency signal light from 20 frequency multiplexed signal lights.
It is easily understood from these figures and Table 3 that selecting any signal light from the other 19 frequency signal lights by changing the combination of the operating optical gates of the front and rear optical gate switch arrays 32 and 34. can do.
[0059]
Therefore, by using this filter, it is possible to extract any one light from the light having 20 optical frequency components arranged at regular intervals at a frequency interval of 100 GHz.
Table 3 (c) shows the correspondence between the extracted optical frequency and the gate that transmits light by passing a current.
In this embodiment, by combining the operation gates of the two optical frequency filters, light of an arbitrary frequency signal can be extracted from 20 frequency multiplexed signal lights within a frequency range from 191.0 THz to 192.9 THz. .
The number of electrodes to be controlled is nine.
In the configuration of the conventional optical frequency filter, a filter capable of selecting an arbitrary frequency signal light from among the 20 frequency multiplexed signal lights requires control of 20 optical gate switches. It can be seen that it is sufficient to control the (5 + 4) optical gate switch, and the number of electrodes can be significantly reduced.
[0060]
Obviously, the greater the number of required frequency channels, the greater the effect of reducing the number of electrodes with the arrangement according to the invention.
In the present embodiment, the case where an optical amplifier is used as the optical gate switch has been described. Exactly the same effect can be expected.
Also, the case of N-input and one-output has been described as the optical converging circuit, but an N-input and M-output circuit can be used.
It is needless to say that a similar effect can be obtained even when the transmission characteristics of the first and second arrayed waveguide gratings of the present embodiment are reversed.
[0061]
[Example 4]
FIG. 8 shows a fourth embodiment of the present invention.
The present embodiment relates to a frequency filter applied when input light is signal light in which 20 frequencies are multiplexed at intervals of 100 GHz.
In the figure, reference numeral 41 denotes an arrayed waveguide grating filter having 4 channels and an FSR of 4 times the channel interval, and 5 denotes an arrayed waveguide grating filter having 5 channels and an FSR of 5 times the channel interval. The channel spacing of the waveguide grating filter 41 is set to be equal to the FSR of the second arrayed waveguide grating filter 45.
[0062]
That is, in the first array waveguide grating filter 41, the array waveguide, the slab waveguide, and the input / output waveguide are arranged such that the frequency channel interval is 500 GHz, the transmission band between channels is 500 GHz, the FSR is 2000 GHz, and the number of channels is 4. In the second array waveguide grating filter 45, the array waveguide, the slab waveguide, and the input / output waveguide are arranged such that the frequency channel interval is 100 GHz, the transmission band for each channel is 100 GHz, the FSR is 500 GHz, and the number of channels is 5. Have been.
42 is a 4-channel optical gate / switch array, 43 is a 4-input / 5-output optical convergence / distribution circuit, 44 is a 5-channel optical gate / switch array, and 46 is an electrode. A large number of optical waveguides are formed on an InP semiconductor substrate, and the core layers of the waveguides of the arrayed waveguide grating filters 41 and 45 are formed of InGaAsP having a band gap wavelength of 1050 nm.
[0063]
The composition of the waveguide layers of the semiconductor amplifier sections 42 and 44 used as the optical gate switch is InGaAsP having a band gap wavelength of 1550 to 1580 nm, and absorbs or amplifies light near the wavelength of 1550 nm (optical frequency: up to 193 THz). Has an action.
The voltage is controlled between the electrode 46 formed on the upper part of the semiconductor amplifier and the electrode formed on the back surface of the substrate, and the current flowing through the waveguide layer of the semiconductor amplifier is turned on / off to transmit / transmit light. Shutdown control is performed.
Here, the operation of the device of the present invention will be described.
Input / output optical frequency of each arrayed waveguide grating filter when 20 frequency multiplexed signal lights are incident from an input port of the first arrayed waveguide grating filter 41 and each input port of the second arrayed waveguide grating filter 45 Are shown in Tables 4 (a) and 4 (b), respectively.
[0064]
[Table 4]

[0065]
Table 4 (a) shows the arrayed waveguide grating filter 41, Table 4 (b) shows the arrayed waveguide grating filter 45, and Table 4 (c) shows the input / output optical frequency for the entire optical frequency filter of the fourth embodiment. Shows the relationship.
Now, it is assumed that the signal light is incident from a certain input port of the first arrayed waveguide grating filter 41.
The optical gate switch element numbers of the optical gate switch arrays 42 and 44 in FIG. 8 are again denoted by A1 to A4 and B1 to B5, respectively. When the switch is in the cutoff operation, the transmission characteristics are as shown in FIG.
[0066]
By causing the optical gate switch A1 to perform the transmission operation, the signal lights of the five frequencies f1 to f5 indicated by the solid lines in FIG. The light enters the distribution circuit 43.
Since the optical gate switches A2 to A4 are turned off, no other signal light enters from another incident waveguide of the optical convergence distribution circuit 43.
The signal light that has entered the optical multiplexing / distributing circuit 43 from the optical gate switch A1 is branched by the optical convergence / distributing circuit 43 and is incident on the 5-channel optical gate / switch array.
Now, in the second array waveguide grating filter 45, only one output port is used.
According to Table 4 (b), the output signal light is obtained from the output port when the signal light having the optical frequency indicated by B1 to B5 in FIG. .
[0067]
In this embodiment, since only the optical gate switch B1 of the optical gate switch array 44 is operated to be transmitted and the optical gate switches B2 to B5 are turned off, signals are transmitted only from the input port 1 to the second array switch. The light enters the waveguide grating filter 45, and no signal light enters from the other incident waveguides.
In this case, in the transmission characteristics, a periodic transmission frequency band occurs every five channel intervals as shown by the solid line in FIG. 7B.
By the way, since only f1 to f5 are selected in the optical gate switch array 42 in the former stage, the light enters from B1 of the optical gate switch array 44 in the latter stage and is output from the output port of the second arrayed waveguide grating 45. Only f1 is used.
As a result, from the output port of the second arrayed waveguide grating 45, the signal light having the frequency f1 is multiplied by the transmission characteristics of the two, that is, as shown in FIG. Output from the output port of the waveguide grating 45.
[0068]
This output signal becomes the transmission characteristic of the filter shown in this embodiment, and as shown in FIG. 7C, a transmission frequency band occurs every 20 waves (= 4 × 5).
This optical frequency filter can be used as a filter that can select an arbitrary frequency signal light from 20 frequency multiplexed signal lights.
By changing the combination of the operating optical gates of the front and rear optical gate / switch arrays 42 and 44, selecting any signal light from the other 19 frequency signal lights can be easily understood from these figures and Table 4. can do.
Therefore, by using this filter, it is possible to extract any one light from the light having 20 optical frequency components arranged at regular intervals at a frequency interval of 100 GHz.
Table 4 (c) shows the correspondence between the extracted optical frequency and the gate that transmits light by passing a current.
[0069]
In this embodiment, by combining the operation gates of the two optical frequency filters, it is possible to extract a signal light having an arbitrary frequency from 20 frequency-multiplexed signal lights within a frequency range from 191.0 THz to 192.9 THz.
The number of electrodes to be controlled is nine.
In the present embodiment, the case where an optical amplifier is used as the optical gate switch has been described. Exactly the same effect can be expected.
Also, the case where the optical converging circuit has N inputs and M outputs has been described, but the same effect can be expected if the number of input ports and the number of output ports are N and M or more, respectively.
It is needless to say that a similar effect can be obtained even when the transmission characteristics of the first and second arrayed waveguide gratings of the present embodiment are reversed.
[0070]
[Example 5]
FIG. 9 shows a fifth embodiment of the present invention.
The present embodiment relates to a frequency filter applied when input light is signal light in which 20 frequencies are multiplexed at 100 GHz intervals.
In the figure, reference numeral 51 denotes an arrayed waveguide grating filter having 5 channels, a channel interval of 100 GHz, a transmission band of 100 GHz for each channel, and an FSR of 5 times the channel interval, that is, 500 GHz.
An array 53 has four channels, a channel interval of 500 GHz, and a transmission band for each channel is three times the channel interval of the first arrayed waveguide grating filter 51, ie, 300 GHz, and the FSR is four times the channel interval, ie, an array of 2000 GHz. It is a waveguide grating filter.
[0071]
However, the interval between the input waveguides at the junction of the second arrayed waveguide grating 53 with the slab waveguide is set to 500 GHz for the channel interval of the second arrayed waveguide grating filter 53 and 100 GHz for the signal light as shown in FIG. Are shifted (600 GHz) by an amount equal to the sum of the values.
At this time, when multiplex signal light enters from each input port of the second arrayed waveguide grating filter 53, each optical frequency signal is distributed to the focal position shown in FIG. 11 for each frequency.
FIG. 11 shows the relationship between the optical frequency signals f1 to f20 and the focus position with respect to the incidence from each input port at this time (dotted line).
[0072]
As can be seen from this figure, each of the 20 signals always passes through the center of the transmission band by appropriately selecting the input port of the second arrayed waveguide grating filter 53 (dotted frame in FIG. 11, FIG. 12). .
Table 5 (a) is for the arrayed waveguide grating filter 51, Table 5 (b) is for the arrayed waveguide grating filter 58, and Table 5 (c) is for the entire optical frequency filter of the fifth embodiment. Shows the relationship.
Therefore, the transmission characteristics are as shown in Table 5 (b).
[0073]
[Table 5]

[0074]
52 is an optical gate switch array of 5 channels, 54 is an optical gate switch array of 4 channels, 55 is an optical convergence circuit of 4 inputs and 1 output, and 56 is an electrode.
A large number of optical waveguides are formed on an InP semiconductor substrate, and the core layers of the waveguides of the arrayed waveguide grating filters 51 and 53 are formed of InGaAsP having a band gap wavelength of 1050 nm.
The composition of the waveguide layers of the semiconductor amplifier sections 52 and 54 used as optical gate switches is InGaAsP having a band gap wavelength of 1550 to 1580 nm, and absorbs or absorbs light near a wavelength of 1550 nm (optical frequency =: 193 THz). Has an amplifying effect.
[0075]
The voltage is controlled between the electrode 56 formed on the upper part of the semiconductor amplifier and the electrode formed on the back surface of the substrate, and the current flowing in the waveguide layer of the semiconductor amplifier is turned on / off, thereby transmitting / transmitting light. Shutdown control is performed.
Here, the operation of the device of the present invention will be described.
The optical gate switch element numbers of the optical gate switch arrays 52 and 54 in FIG. 9 are A1 to A5 and B1 to B4, respectively. For example, the optical gate switches A2 and B1 are operated in a transparent manner, and the other optical gate switches are operated. Consider the case of a shut-off operation.
The multiplexed light entering from the incident port of the first arrayed waveguide grating 52 is distributed to the optical gate switches A1 to A5 for each frequency component as shown in Table 5 (a).
When A2 is turned on and A1 and A3 to A5 are turned off, f2, f7, f12, and f17 enter the input port 2 of the second arrayed waveguide grating 53, and a signal enters other input ports. Absent.
[0076]
The upper four signals from the input port 2 of the second arrayed waveguide grating 53 enter f7, f12, f17, and f2 into the optical gate switches B1 to B4, respectively, according to the transmission characteristics shown in Table 5 (b). .
Further, when the optical gate switch B1 is turned on and the other optical gate switches B2 to B5 are turned off, only f7 enters the 5-input / 1-output optical merging circuit 55, and finally this optical frequency filter Is f7.
By changing the combination of the operating optical gates of the front and rear optical gate switch arrays 42 and 44, it is easy to select an arbitrary signal light from the other 19 frequency signal lights from these figures and Table 5. Can be understood.
Therefore, by using this filter, it is possible to extract any one light from the light having 20 optical frequency components arranged at regular intervals at a frequency interval of 100 GHz.
Table 5 (c) shows the correspondence between the extracted optical frequency and the gate that transmits current and allows light to pass therethrough.
[0077]
In this embodiment, by combining the operation gates of the two optical frequency filters, it is possible to extract a signal light having an arbitrary frequency from 20 frequency-multiplexed signal lights within a frequency range from 191.0 THz to 192.9 THz.
The number of electrodes to be controlled is nine.
Conventionally, when an arrayed waveguide grating having a transmission characteristic having a Gaussian distribution is formed in a plurality of stages, the passing band tends to gradually narrow due to a design error or the like. The selected signal can always pass through the center of the transmission band by devising the arrangement of the input waveguide of the subsequent arrayed waveguide grating at the connection point of the slab waveguide.
Thereby, an effect of suppressing the band narrowing can be expected.
[0078]
In the present embodiment, the case where an optical amplifier is used as the optical gate switch has been described. Exactly the same effect can be expected.
Also, the case where the optical converging circuit has N inputs and M outputs has been described, but the same effect can be expected if the number of input ports and the number of output ports are N and M or more, respectively.
[0079]
【The invention's effect】
As described above in detail based on the embodiments, according to the present invention, it is possible to realize an optical frequency filter in which the number of optical frequencies (wavelengths) that can be selected by controlling a small number of electrodes is significantly increased.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
2A is a transmission spectrum of the arrayed waveguide grating filters 1 and 7, FIG. 2B is a transmission spectrum of the arrayed waveguide grating filters 3 and 11, and FIG. It is a graph showing the transmission spectrum of the whole filter.
FIG. 3 is a configuration diagram illustrating a second embodiment of the present invention.
FIG. 4 is a configuration diagram of a conventional example.
FIG. 5 is a configuration diagram showing a specific example of an optical convergence circuit and an optical convergence distribution circuit.
FIG. 6 is a configuration diagram illustrating a third embodiment of the present invention.
7A is a transmission spectrum of the arrayed waveguide grating filters 31 and 41, FIG. 7B is a diagram of the arrayed waveguide grating filters 33 and 45, and FIG. It is a graph showing.
FIG. 8 is a configuration diagram illustrating a fourth embodiment of the present invention.
FIG. 9 is a configuration diagram illustrating a fifth embodiment of the present invention.
FIG. 10 is an explanatory diagram showing a design of an input waveguide of an arrayed waveguide grating filter 53 according to a fifth embodiment of the present invention.
FIG. 11 is an explanatory diagram showing a relationship between input and output optical frequencies of an arrayed waveguide grating filter 53 according to a fifth embodiment of the present invention.
FIG. 12 is a graph showing transmission characteristics of an arrayed waveguide grating filter 53 according to a fifth embodiment of the present invention.
[Explanation of symbols]
1,3 Arrayed waveguide grating filter
7,11 Arrayed waveguide grating filter
2,4,8,10,11 Semiconductor amplifier gate array
5 Optical merging circuit
6,12 Electrode for optical gate control
9 Optical merging and distribution circuit
13,18 Input optical waveguide
16,21 output optical waveguide
14, 15, 19, 20 Slab waveguide
17,22 Array waveguide
23 Optical gate control electrode
24 InP substrate
31,33 Arrayed waveguide grating filter
32,34 Semiconductor amplifier gate array
35,55 Optical merging circuit
36,46,56 Electrode for optical gate control
41,45 Arrayed waveguide grating filter
42,44 Semiconductor amplifier gate array
43 Optical Convergence Distribution Circuit
51,53 Arrayed waveguide grating filter
52,54 Semiconductor Amplifier Gate Array
110 Arrayed Waveguide Grating Demultiplexer
111 Array waveguide grating multiplexer
112 Semiconductor Amplifier Gate Array
120 InP substrate
121, 126 input optical waveguide
125,130 output optical waveguide
122, 124, 127, 129 Slab waveguide
123,128 Array waveguide

Claims (5)

A first arrayed waveguide grating filter having a function of splitting light incident on one input waveguide into at least two or more output waveguides for each different optical frequency, and combining the split light into one An optical frequency filter comprising an optical gate switch for transmitting or blocking the demultiplexed light connected between a second arrayed waveguide grating filter having an action of multiplexing with a waveguide. In the arrayed waveguide grating filter, the waveguides are arranged so that the difference between the optical frequencies to be split or multiplexed between the adjacent output waveguides or input waveguides is equal in all arrayed waveguide gratings, and The interval between transmitted light frequencies periodically generated in the first arrayed waveguide grating filter and the interval between transmitted light frequencies periodically generated in the second arrayed waveguide grating filter are different by the difference of the optical frequency. The difference in length between adjacent array waveguides in the first arrayed waveguide grating filter and the difference in length between adjacent arrayed waveguides in the second arrayed waveguide grating filter are different values. And an optical gate switch for transmitting or blocking the demultiplexed light is connected to at least two or more output waveguides of the second arrayed waveguide grating filter, and the output guide of the optical gate switch is connected. An optical frequency filter, wherein an optical combining circuit is connected to the wave path. A first arrayed waveguide grating filter having a function of splitting light incident on one input waveguide into at least two or more output waveguides for each different optical frequency, and combining the split light into one An optical frequency filter comprising an optical gate switch for transmitting or blocking the demultiplexed light connected between a second arrayed waveguide grating filter having an action of multiplexing with a waveguide. In the arrayed waveguide grating filter, the waveguides are arranged so that the difference between the optical frequencies to be split or multiplexed between the adjacent output waveguides or input waveguides is equal in all arrayed waveguide gratings, and The interval between transmitted light frequencies periodically generated in the first arrayed waveguide grating filter and the interval between transmitted light frequencies periodically generated in the second arrayed waveguide grating filter are different by the difference of the optical frequency. The difference in length between adjacent array waveguides in the first arrayed waveguide grating filter and the difference in length between adjacent arrayed waveguides in the second arrayed waveguide grating filter are different values. And an optical converging / distributing circuit connected to the output waveguide of the optical gate switch, and transmitting or blocking the demultiplexed light to at least two or more output waveguides of the optical converging / distributing circuit. An optical frequency filter to which a gate switch is connected, wherein an output waveguide of the optical gate switch is connected to different input waveguides of a second arrayed waveguide grating filter. An optical frequency filter in which an optical gate switch for transmitting or blocking light split by the first arrayed waveguide grating filter is connected between two arrayed waveguide grating filters. Wherein the waveguides are arranged such that the difference between the optical frequencies demultiplexed to adjacent output waveguides and the interval between the transmitted light frequencies periodically generated by the second arrayed waveguide grating filter are equal, or In the two arrayed waveguide grating filters, the waveguides are set so that the difference between the optical frequencies demultiplexed to adjacent output waveguides and the interval between the transmitted light frequencies periodically generated in the first arrayed waveguide grating filter are equal. Is connected, and an optical gate switch for transmitting or blocking the demultiplexed light is connected to at least two or more output waveguides of the second arrayed waveguide grating filter. Optical frequency filter, characterized in that the optical combining circuit is connected to the output waveguides of the optical gate switches. An optical frequency filter in which an optical gate switch for transmitting or blocking light split by the first arrayed waveguide grating filter is connected between two arrayed waveguide grating filters. Wherein the waveguides are arranged such that the difference between the optical frequencies demultiplexed to adjacent output waveguides and the interval between the transmitted light frequencies periodically generated by the second arrayed waveguide grating filter are equal, or In the two arrayed waveguide grating filters, the waveguides are set so that the difference between the optical frequencies demultiplexed to adjacent output waveguides and the interval between the transmitted light frequencies periodically generated in the first arrayed waveguide grating filter are equal. Is further arranged, and an optical converging / distributing circuit is connected to the output waveguide of the optical gate switch, and the distributed light is distributed to at least two or more output waveguides of the optical converging / distributing circuit. An optical frequency filter, wherein an optical gate switch for transmitting or blocking is connected, and an output waveguide of the optical gate switch is connected to different input waveguides of a second arrayed waveguide grating filter. . An optical frequency filter in which an optical gate switch for transmitting or blocking light split by the first arrayed waveguide grating filter is connected between the two arrayed waveguide grating filters. In the output waveguide, the transmitted optical frequency band is equal to or more than the optical frequency band transmitted by the first arrayed waveguide grating filter and equal to or less than the interval of the transmitted light frequency periodically generated in the first arrayed waveguide grating filter. Set in the range, and in the second arrayed waveguide grating filter, the difference between the optical frequency split into adjacent output waveguides and the transmitted light frequency periodically generated in the first arrayed waveguide grating filter. The input of the second arrayed waveguide grating filter is shifted so that the interval is shifted by the difference of the optical frequency demultiplexed to the adjacent output waveguides in the first arrayed waveguide grating filter. A waveguide is disposed, and an optical gate switch for transmitting or blocking the demultiplexed light is connected to at least two or more output waveguides of the second arrayed waveguide grating filter. An optical frequency filter, wherein an optical combining circuit is connected to the output waveguide.

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