JP3772132B2

JP3772132B2 - Optical signal quality degradation factor monitoring method and apparatus

Info

Publication number: JP3772132B2
Application number: JP2002172035A
Authority: JP
Inventors: 一平社家; 秀彦高良; 健太郎内山
Original assignee: Nippon Telegraph and Telephone Corp
Current assignee: Nippon Telegraph and Telephone Corp
Priority date: 2001-07-13
Filing date: 2002-06-12
Publication date: 2006-05-10
Anticipated expiration: 2022-06-12
Also published as: JP2003090766A

Description

【０００１】
【発明の属する技術分野】
本発明は、光通信における光信号品質劣化の要因を監視する方法および装置に関する。
【０００２】
【従来の技術】
光通信におけるこれまでの地点間通信では、同期網が提供するフレームに光時分割多重（ＯＴＤＭ：Optical Time Division Multiplexing）を用いて信号を束ねている。
【０００３】
このような光時分割多重では、同期光通信網（Synchronous Optical Network(ＳＯＮＥＴ）)／同期デジタルハイアライキー（Synchronous Digital Hierarchy(ＳＤＨ）)伝送方式等が用いられているが、このＳＯＮＥＴ／ＳＤＨ伝送方式では効率的な信号伝送を行うためにオーバーヘッドが定められており（参考文献［１］：ＩＴＵ−Ｔ Recommendation G707）、そのオーバーヘッドを用いてビット・インタリーブド・パリティ（Bit Interleaved Parity）とよばれるパリティ検査を、中継器間や多重化端局相互間でそれぞれ実施することで、故障区間の同定と切替起動信号を得ている。
【０００４】
ところが、ＳＯＮＥＴ／ＳＤＨ伝送方式などの信号品質監視系では、対象とする信号のビットレートや信号形式や変調形式（ＮＲＺ（Non Return to Zero：非ゼロ復帰）またはＲＺ（Return to Zero：ゼロ復帰）に応じた受信系（クロック抽出回路、受信回路、フレーム検出回路、パリティ検査回路または照合回路からなる誤り検出回路）が必要となる。そのため、単一の受信系では任意のビットレートや信号形式や変調形式の信号には対応できないという点がある。また、この従来の光信号監視系では、光信号を電気信号に置換した後に電気信号処理を行う必要があったため、経済性を考慮すると、光増幅中継系に適用することが難しく、例えばネットワーク障害が検知されたときに、光増幅中継系間のどの区間で障害が発生したかまでを同定することができない。
【０００５】
以上のことから、サービスあたりの通信容量が大きく、多様な信号形式、信号ビットレートに対応した、経済的なサービス転送網を構築することが不可欠である。ここで光ネットワークは、光時分割多重や波長分割多重（ＷＤＭ：Wavelength Division Multiplexing）を用いることにより通信容量を拡大でき、信号ビットレート、信号形式および変調形式に対して透明性がある点において極めて有望である。
【０００６】
そこで、このような光ネットワークに適した光信号品質監視法として、振幅ヒストグラムから光信号品質パラメータを評価する方法が提案されている（参考文献［２］：ＥＰＣ公開番号ＥＰ０９２０２５０Ａ２、米国出願（未公開）ＵＳＰ Application 09/204,001）。図１７にこの従来例の構成を示す。この従来例の光信号品質監視部１７０１は、光信号振幅ヒストグラム測定部１７０３と平均Ｑ値パラメータ評価部１７０５と光信号品質評価部１７０７とから構成され、光信号振幅ヒストグラム測定部１７０３において、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号から光信号振幅ヒストグラムを得て、平均Ｑ値パラメータ評価部１７０５において、その光信号振幅ヒストグラムから光信号品質パラメータである平均Ｑ値パラメータを評価し、光信号品質評価部１７０７において、その平均Ｑ値パラメータを解析することにより光信号品質監視を実現している。
【０００７】
【発明が解決しようとする課題】
ところで、近年のマルチメディアサービスの需要が急速に高まり、個々のサービスの通信容量を拡大する必要が生じてきた上に、映像、音声、データ等、多様な信号ビットレート・信号形式に効率的に対応するネットワークが切望されてくると、それに伴って監視すべき光信号の劣化要因も多様化し、特に伝送光ファイバの損失や伝送端局内の損失、光源劣化などによる光信号対雑音比劣化や、伝送光ファイバ中の波長分散による波形劣化などに個々に対応した監視が必要になる。
【０００８】
しかしながら、上述した従来例における平均Ｑ値パラメータは光信号対雑音比劣化や波長分散による波形劣化に対して感度があるが、それぞれの原因を判別することはできない。
【０００９】
本発明は、上述の点に鑑みてなされたもので、その目的は、サービスあたりの通信容量が大きく、多様な信号形式、信号ビットレートを有するマルチメディアサービスを収容できるような経済的で信頼性の高い光ネットワークを実現するのに寄与する光信号品質劣化要因監視方法および光信号品質劣化要因監視装置を提供することにある。
【００１０】
【課題を解決するための手段】
上記目的を達成するため、本発明の請求項１の光信号品質劣化要因監視方法は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとして、被測定光信号から光振幅ヒストグラムを得る光信号振幅ヒストグラム測定工程と、前記光信号振幅ヒストグラム測定工程によって得られる前記光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値を利用して光信号品質劣化要因を評価する光信号品質評価工程であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該波形劣化パラメータが増加していないときには伝送特性劣化の主要因が波形劣化以外と判別する光信号品質評価工程とを有することを特徴とする。
【００１１】
上記目的を達成するため、本発明の請求項２の光信号品質劣化要因監視方法は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとして、被測定光信号から光振幅ヒストグラムを得る光信号振幅ヒストグラム測定工程と、前記光信号振幅ヒストグラム測定工程によって得られる前記光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程を利用して得られる、光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータの初期値または初期特性を記憶媒体に記憶する初期状態記憶工程と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値と、前記初期状態記憶工程において前記記憶媒体に記憶されている前記初期値または前記初期特性とを利用して光信号品質劣化要因を評価する光信号品質評価工程であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該波形劣化パラメータが増加していないときには伝送特性劣化の主要因が波形劣化以外と判別する光信号品質評価工程とを有することを特徴とする。
【００１６】
上記目的を達成するため、本発明の請求項３の光信号品質劣化要因監視方法は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとし、光信号強度と光雑音強度の比を光信号対雑音比パラメータとして、被測定光信号を分岐する光分岐工程と、前記光分岐工程により分岐された一方の被測定光信号から光信号振幅ヒストグラムを得る光信号振幅ヒストグラム測定工程と、前記光分岐工程により分岐された他方の被測定光信号から光信号・光雑音の測定を行う光信号・光雑音強度測定工程と、前記光信号振幅ヒストグラム測定工程によって得られる光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程と、前記光信号・光雑音強度測定工程によって得られる前記光信号・光雑音強度から光信号品質パラメータである前記光信号対雑音比パラメータを得る光信号対雑音比パラメータ評価工程と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値と前記光信号対雑音比パラメータ評価工程で得られた光信号対雑音比パラメータの測定値を利用して光信号品質劣化要因を評価する光信号品質評価工程であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該光信号対雑音比パラメータが増加しているときには主要因が光信号対雑音比劣化と判別し、該波形劣化パラメータと該光信号対雑音比パラメータが増加していないときには主要因を波形劣化と光信号対雑音比劣化以外と判別する光信号品質評価工程とを有することを特徴とする。
【００１７】
上記目的を達成するため、本発明の請求項４の光信号品質劣化要因監視方法は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとし、光信号強度と光雑音強度の比を光信号対雑音比パラメータとして、被測定光信号を分岐する光分岐工程と、前記光分岐工程により分岐された一方の被測定光信号から光信号振幅ヒストグラムを得る光信号振幅ヒストグラム測定工程と、前記光分岐工程により分岐された他方の被測定光信号から光信号・光雑音の測定を行う光信号・光雑音強度測定工程と、前記光信号振幅ヒストグラム測定工程によって得られる光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程と、前記光信号・光雑音強度測定工程によって得られる前記光信号・光雑音強度から光信号品質パラメータである前記光信号対雑音比パラメータを得る光信号対雑音比パラメータ評価工程と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程と前記光信号対雑音比パラメータ評価工程とを利用して得られる、光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの初期値または初期特性を記憶媒体に記憶する初期状態記憶工程と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価工程で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値と前記光信号対雑音比パラメータ評価工程で得られた前記光信号対雑音比パラメータの測定値と、前記初期状態記憶工程で前記記憶媒体に記憶されている光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの初期値または初期特性とを利用して光信号品質劣化要因を評価する光信号品質評価工程であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該光信号対雑音比パラメータが増加しているときには主要因が光信号対雑音比劣化と判別し、該波形劣化パラメータと該光信号対雑音比パラメータが増加していないときには主要因を波形劣化と光信号対雑音比劣化以外と判別する光信号品質評価工程とを有することを特徴とする。
【００１８】
ここで、好ましくは、前記光信号振幅ヒストグラム測定工程が、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号を電気強度変調信号に変換する光電変換工程と、前記光電変換工程によって得られる前記電気強度変調信号を、繰り返し周波数がｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）のサンプリングクロックでサンプリングする電気サンプリング工程と、前記電気サンプリング工程によって得られるサンプリング信号から光信号強度分布を求め、ある平均時間内の光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価工程とを含む。
【００１９】
また、好ましくは、前記光信号振幅ヒストグラム測定工程が、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号を、繰り返し周波数がｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）でパルス幅がビットレートｆ_０（ｂｉｔ／ｓ）のタイムスロットよりも十分狭いサンプリング光パルス列と合波する光合波工程と、前記光合波工程により合波された合波光を、前記被測定光信号と前記サンプリング光パルス列の非線形相互作用を誘起するための非線形光学媒質に入射させることによって相互相関光信号を得る相互相関光信号発生工程と、前記相互相関光信号発生工程により得られる前記相互相関光信号を前記被測定光信号および前記サンプリング光パルス列から分波する光分波工程と、前記光分波工程により分波された前記相互相関光信号を電気強度変調信号に変換する光電変換工程と、前記光電変換工程によって得られる前記電気強度変調信号から光信号強度分布を求め、ある平均時間内の光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価工程とを含む。
【００２２】
上記目的を達成するため、本発明の請求項８の光信号品質劣化要因監視装置は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとして、被測定光信号から光振幅ヒストグラムを得る光信号振幅ヒストグラム測定手段と、前記光信号振幅ヒストグラム測定手段によって得られる前記光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値を利用して光信号品質劣化要因を評価する光信号品質評価手段であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該波形劣化パラメータが増加していないときには伝送特性劣化の主要因が波形劣化以外と判別する光信号品質評価手段とを有することを特徴とする。
【００２３】
上記目的を達成するため、本発明の請求項９の光信号品質劣化要因監視装置は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとして、被測定光信号から光振幅ヒストグラムを得る光信号振幅ヒストグラム測定手段と、前記光信号振幅ヒストグラム測定手段によって得られる前記光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段を利用して得られる、光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータの初期値または初期特性を記憶媒体に記憶する初期状態記憶手段と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値と、前記初期状態記憶手段において前記記憶媒体に記憶されている前記初期値または前記初期特性とを利用して光信号品質劣化要因を評価する光信号品質評価手段であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該波形劣化パラメータが増加していないときには伝送特性劣化の主要因が波形劣化以外と判別する光信号品質評価手段とを有することを特徴とする。
【００２８】
上記目的を達成するため、本発明の請求項１０の光信号品質劣化要因監視装置は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとし、光信号強度と光雑音強度の比を光信号対雑音比パラメータとして、被測定光信号を分岐する光分岐手段と、前記光分岐手段により分岐された一方の被測定光信号から光信号振幅ヒストグラムを得る光信号振幅ヒストグラム測定手段と、前記光分岐手段により分岐された他方の被測定光信号から光信号・光雑音の測定を行う光信号・光雑音強度測定手段と、前記光信号振幅ヒストグラム測定手段によって得られる光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段と、前記光信号・光雑音強度測定手段によって得られる前記光信号・光雑音強度から光信号品質パラメータである前記光信号対雑音比パラメータを得る光信号対雑音比パラメータ評価手段と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値と前記光信号対雑音比パラメータ評価手段で得られた光信号対雑音比パラメータの測定値を利用して光信号品質劣化要因を評価する光信号品質評価手段であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該光信号対雑音比パラメータが増加しているときには主要因が光信号対雑音比劣化と判別し、該波形劣化パラメータと該光信号対雑音比パラメータが増加していないときには主要因を波形劣化と光信号対雑音比劣化以外と判別する光信号品質評価手段とを有することを特徴とする。
【００２９】
上記目的を達成するため、本発明の請求項１１の光信号品質劣化要因監視装置は、ある平均時間内の光信号強度分布から得られる振幅ヒストグラムのうち、あらかじめ定めた強度しきい値よりも高い振幅ヒストグラム部分から想定した「レベル１」に相当する振幅ヒストグラム分布関数をｇ１とし、別途定めた強度しきい値よりも低い部分から「レベル０」に相当する振幅ヒストグラム分布関数をｇ０として得られた、該分布関数ｇ１とｇ０それぞれの平均値強度の差｜ｍ１−ｍ０｜と該分布関数ｇ１とｇ０の標準偏差値の和（ｓ１＋ｓ０）の比｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）を平均Ｑ値パラメータとし、前記「レベル１」の標準ヒストグラム分布関数ｇ１の標準偏差ｓ１を波形劣化パラメータとし、光信号強度と光雑音強度の比を光信号対雑音比パラメータとして、被測定光信号を分岐する光分岐手段と、前記光分岐手段により分岐された一方の被測定光信号から光信号振幅ヒストグラムを得る光信号振幅ヒストグラム測定手段と、前記光分岐手段により分岐された他方の被測定光信号から光信号・光雑音の測定を行う光信号・光雑音強度測定手段と、前記光信号振幅ヒストグラム測定手段によって得られる光信号振幅ヒストグラムから光信号品質パラメータである前記平均Ｑ値パラメータと前記波形劣化パラメータを得る平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段と、前記光信号・光雑音強度測定手段によって得られる前記光信号・光雑音強度から光信号品質パラメータである前記光信号対雑音比パラメータを得る光信号対雑音比パラメータ評価手段と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段と前記光信号対雑音比パラメータ評価手段とを利用して得られる、光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの初期値または初期特性を記憶媒体に記憶する初期状態記憶手段と、前記平均Ｑ値パラメータ評価および波形劣化パラメータ評価手段で得られた前記平均Ｑ値パラメータの測定値と前記波形劣化パラメータの測定値と前記光信号対雑音比パラメータ評価手段で得られた前記光信号対雑音比パラメータの測定値と、前記初期状態記憶手段で前記記憶媒体に記憶されている光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの初期値または初期特性とを利用して光信号品質劣化要因を評価する光信号品質評価手段であって、該平均Ｑ値パラメータが劣化した場合に、該波形劣化パラメータが増加しているときには伝送特性劣化の主要因が波形劣化と判別し、該光信号対雑音比パラメータが増加しているときには主要因が光信号対雑音比劣化と判別し、該波形劣化パラメータと該光信号対雑音比パラメータが増加していないときには主要因を波形劣化と光信号対雑音比劣化以外と判別する光信号品質評価手段とを有することを特徴とする。
【００３０】
ここで、好ましくは、前記光信号振幅ヒストグラム測定手段が、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号を電気強度変調信号に変換する光電変換手段と、前記光電変換手段によって得られる前記電気強度変調信号を、繰り返し周波数がｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）のサンプリングクロックでサンプリングする電気サンプリング手段と、前記電気サンプリング手段によって得られるサンプリング信号から光信号強度分布を求め、ある平均時間内の光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価手段とを含む。
【００３１】
また、好ましくは、前記光信号振幅ヒストグラム測定手段が、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号を、繰り返し周波数がｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）でパルス幅がビットレートｆ_０（ｂｉｔ／ｓ）のタイムスロットよりも十分狭いサンプリング光パルス列と合波する光合波手段と、前記光合波手段により合波された合波光を、前記被測定光信号と前記サンプリング光パルス列の非線形相互作用を誘起するための非線形光学媒質に入射させることによって相互相関光信号を得る相互相関光信号発生手段と、前記相互相関光信号発生手段により得られる前記相互相関光信号を前記被測定光信号および前記サンプリング光パルス列から分波する光分波手段と、前記光分波手段により分波された前記相互相関光信号を電気強度変調信号に変換する光電変換手段と、前記光電変換手段によって得られる前記電気強度変調信号から光信号強度分布を求め、ある平均時間内の光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価手段とを含む。
【００３２】
また、好ましくは、前記光信号振幅ヒストグラム測定手段が、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号を、サンプリングクロック発生手段から発生する繰り返し周波数が、ｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）のサンプリングクロックでサンプリングする光ゲート手段と、前記光ゲート手段から出力されるサンプリング光信号を受光してサンプリング電気信号に変換する光電変換手段と、前記光電変換手段によって得られる前記サンプリング電気信号から光信号強度分布を求め、ある平均時間内の光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価手段とを含む。
【００３４】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態を詳細に説明する。
(第１の実施形態)
図１の（Ａ）、（Ｂ）に本発明の第１の実施形態における光信号品質劣化要因監視装置の構成を示す。本実施形態の光信号品質劣化要因監視装置１０１は、光信号振幅ヒストグラム測定部１０３と、平均Ｑ値パラメータ評価部１０５と、波形劣化パラメータ評価部１０７と、初期状態記憶部１０９と、光信号品質評価部１１１とを有する。
【００３５】
光信号振幅ヒストグラム測定部１０３は被測定光信号から光振幅ヒストグラムを得る。平均Ｑ値パラメータ評価部１０５はその光信号振幅ヒストグラムから光信号品質パラメータである平均Ｑ値パラメータを得る。波形劣化パラメータ評価部１０７はその光信号振幅ヒストグラムから光信号品質パラメータである波形劣化パラメータを得る。初期状態記憶部１０９は光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータの初期値または初期特性を記憶媒体に記憶する。
【００３６】
光信号品質評価部１１１は平均Ｑ値パラメータの測定値と波形劣化パラメータの測定値と、初期状態記憶部１０９の記憶媒体に記憶されている初期値または初期特性とを利用して、光信号品質劣化要因を評価するが、その際に、平均Ｑ値パラメータと波形劣化パラメータの両方を規定し評価することによって、光信号品質劣化の主要因が被測定光信号の波形劣化なのか、それ以外なのかを判別する。
【００３７】
次に、図２のフローチャートを参照して、本実施形態における光信号品質劣化要因監視の手順を詳述する。
ステップ２０１：信号劣化がない状態のシステム導入時に、平均Ｑ値パラメータと波形劣化パラメータの（ａ）…初期値のみ、または（ｂ）…光信号対雑音比劣化依存性を評価する。
ステップ２０３：ステップ２０１の測定結果を初期状態記憶部１０９に記憶する。（以上、図１の（Ａ））。
ステップ２０５：システム運用開始後は一定の時間間隔で平均Ｑ値パラメータと波形劣化パラメータを評価する。
ステップ２０７：平均Ｑ値パラメータと波形劣化パラメータを測定するごとに光信号品質評価部１１１においてそれら測定値と、初期状態記憶部１０９の初期値または光信号対雑音比劣化依存グラフと比較する。
ステップ２０９：初期値からの平均Ｑ値パラメータの劣化を観測した場合、または平均Ｑ値パラメータが初期状態記憶部の光信号対雑音比劣化依存性グラフのあらかじめ決められたしきい値を下回った場合に、
（ａ）…波形劣化パラメータの変化がないか、もしくは小さいときは、劣化要因は波形劣化以外であると判別する。
（ｂ）…波形劣化パラメータの変化が大きいときは、劣化要因は主に波形劣化であると判別する。（以上、図１の（Ｂ））。
【００３８】
光信号振幅ヒストグラム測定部１０３は、例えば図３に示すように、光電変換部３０３と、電気サンプリングオシロスコープ３０５と、ヒストグラム評価部３０７とで構成される。この構成では、光電変換部３０３において、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号を電気強度変調信号に変換し、電気サンプリングオシロスコープ３０５において、その電気強度変調信号を繰り返し周波数がｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）のサンプリングクロックでサンプリングし、ヒストグラム評価部３０７において、そのサンプリングオシロスコープ３０５によって得られるサンプリング信号から、図５に示すように、光信号強度分布を求め、ある平均時間内のその光信号強度分布から光信号振幅ヒストグラムを得る。
【００３９】
また、光信号振幅ヒストグラム測定部１０３の別の例を図４に示す。本例の光信号振幅ヒストグラム測定部１０３は、光サンプリングオシロスコープ４０５とヒストグラム評価部３０７とで構成される。
【００４０】
この光サンプリングオシロスコープ４０５は、公知技術の光サンプリング法（参考文献［３］：H. Takara, S, Kawanishi, A. Yokoo, S.Tomaru, T. Kitoh, and M. Saruwatari, “100 Gbit/s optical signal eye-diagram measurement with optical sampling using organic nonlinear optical crystal”, Electron, Lett., 24, pp. 2256-2258, 1996. ）を利用できる。すなわち、光サンプリングオシロスコープ４０５は、ビットレートｆ_０（ｂｉｔ／ｓ）の被測定光信号と繰り返し周波数がｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）でパルス幅がビットレートｆ_０（ｂｉｔ／ｓ）のタイムスロットよりも十分狭いサンプリング光パルス列とを合波する光合波部と、その被測定光信号とそのサンプリング光パルス列の非線形相互作用を誘起するための非線形光学媒質に入射させることによって相互相関光信号を得る相互相関光信号発生部と、その相互相関光信号をその被測定光信号およびそのサンプリング光パルス列から分波する光分波部と、この光分波部により分波された相互相関光信号を電気強度変調信号に変換する光電変換と、その電気強度変調信号から図５のように光信号強度分布を求め、ある平均時間内の該光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価部とから構成できる。
【００４１】
また、光サンプリングオシロスコープ４０５は、別の例として、サンプリングクロック発生部と、ビットレートｆ_０（ｂｉｔ／ｓ）の光信号をこのサンプリングクロック発生部から発生する繰り返し周波数が、
ｆ_１（Ｈｚ）（ｆ_１＝（ｎ／ｍ）ｆ_０＋ａ：ｎ，ｍは自然数、ａはオフセット周波数）
のサンプリングクロックでサンプリングする光ゲート部と、この光ゲート部から出力されるサンプリング光信号を受光してサンプリング電気信号に変換する光電変換部と、そのサンプリング電気信号から光信号強度分布を求め、ある平均時間内の光信号強度分布から光信号振幅ヒストグラムを得るヒストグラム評価部とから構成できる。ここで、サンプリングクロック発生部には、シンセサイズド信号発生器＋コムジェネレータによる電気短パルス発生などを用いることができる。また、必要に応じて、そのコムジェネレータの前段または後段に電気増幅器を用いることもできる。また、必要に応じて、そのコムジェネレータの後段にベースバンドクリッパを用いることもできる。上記光ゲート部には、電界吸収型光変調器によるゲート動作などを用いることができる。
【００４２】
図１の平均Ｑ値パラメータ評価部１０５と波形劣化パラメータ評価部１０７では、例えば、図６から図９に示すような評価方法が利用できる。
【００４３】
図６における平均Ｑ値パラメータおよび波形劣化パラメータ評価アルゴリズムは以下の通りである。
（１）：光信号振幅ヒストグラム測定部１０３から得られる光信号振幅ヒストグラム（図６の（Ａ））に対して、
（２）：振幅ヒストグラムのうち強度レベルの小さい方から調べたときの極大値をｍ０′と定める（図６の（Ｂ））。
（３）：次に、強度レベル最大のサンプリング点（ｍ０′）から強度レベルが小さい方に向かってサンプリング点数を積分して、
Ｎ（middle）＝Ｎ（total)×Ｄ×Ｍ
（但し、Ｎ（total)は全サンプリング点数、Ｄは光信号のデューティー比（パルス幅とタイムスロットの比）、Ｍはマーク率（ディジタル伝送におけるレベル１の発生確率））
で求まるサンプリング点数Ｎ（middle）と、積分値が等しくなったときの積分したサンプリング点の最小レベルをｍ（middle）とする（図６の（Ｃ））。
（４）：ｍ１′＝２×｛ｍ（middle）−ｍ０′｝
で求まるｍ１′を定める（図６の（Ｄ））。
（５）：ｍ１′−alpha （ｍ１′−ｍ０′）
で求まる強度レベルをしきい値（ａ）
ｍ０′＋alpha （ｍ１′−ｍ０′）
で求まる強度レベルをしきい値（ｂ）
（但し、alpha は０＜alpha ＜０．５の実数）
と定め、強度レベルがしきい値（ａ）以上の分布をレベル１の分布ｇ１、しきい値（ｂ）以下の分布をレベル０の分布ｇ０とし、それぞれの分布ｇ１、ｇ０において、平均値ｍ１，ｍ０と標準偏差ｓ１，ｓ０を求める（図６の（Ｅ））。
（６）：（５）で求めた平均値と標準偏差から
Ｑａｖｇ＝｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）
で求まるＱ値を平均Ｑ値パラメータとし、ｓ１を波形劣化パラメータ（ＷＤ）とする。
【００４４】
図７における平均Ｑ値パラメータおよび波形劣化パラメータ評価アルゴリズムは以下の通りである。
（１）：光信号振幅ヒストグラム測定部１０３から得られる光信号振幅ヒストグラムに対して（図７の（Ａ））、
（２）：振幅ヒストグラムのうち強度レベルの小さい方から調べたときの最初の極大値をしきい値（ｂ）と定める（図７の（Ｂ））。
（３）：強度レベル最大のサンプリング点から強度レベルが小さい方に向かってサンプリング点数を積分して、
Ｎ（middle）＝Ｎ（total)×Ｄ×Ｍ
（但し、Ｎ（total)は全サンプリング点数、Ｄは光信号のデューティー比（パルス幅とタイムスロットの比）、Ｍはマーク率（ディジタル伝送におけるレベル１の発生確率））
で求まるサンプリング点数Ｎ（middle）と積分値が等しくなったときの、積分したサンプリング点の最小レベルをｍ（middle）とする（図７の（Ｃ））。
（４）：しきい値（ａ）＝２×｛ｍ（middle）−しきい値（ｂ）｝
でしきい値（ａ）を定める（図７の（Ｄ））。
（５）：振幅ヒストグラムのうち、強度レベルがしきい値（ａ）以上の部分を正規分布ｇ１の一部と仮定し、しきい値（ｂ）以下の部分を正規分布ｇ０の一部と仮定し、最小二乗法などによりフィッテングしてレベル１、レベル０の平均値ｍ１、ｍ０と標準偏差ｓ１、ｓ０を求める（図７の（Ｅ））。
（６）：（５）で求めた平均値と標準偏差から
Ｑａｖｇ＝｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）
で求まるＱ値を平均Ｑ値パラメータとし、ｓ１を波形劣化パラメータとする。分布関数ｇ０，ｇ１としてはカイ二乗分布を仮定することもできる（参考文献［４］：D. Marcuse, “Derivation of Analytical Expressions for the Bit-Error Probability in Lightwave Systems with Optical Amplifiers,”IEEE J. Lightwave Technol., Vol.8, No. 12, pp1816-1823, 1990)。
【００４５】
図８における平均Ｑ値パラメータおよび波形劣化パラメータ評価アルゴリズムは以下の通りである。
（１）：光信号振幅ヒストグラム測定部１０３から得られる光信号振幅ヒストグラムに対して（図８の（Ａ））、
（２）：振幅ヒストグラムのうち強度レベルの小さい方から調べたときの最初の極大値をしきい値（ｂ）と定める（図８の（Ｂ））。
（３）：振幅ヒストグラムのうち、強度レベルがしきい値（ｂ）以下の部分を正規分布ｇ０の一部と仮定し、最小二乗法などによりフィッテングしてレベル０の平均値ｍ０と標準偏差ｓ０をそれぞれ求める（図８の（Ｃ））。
（４）：振幅ヒストグラム全体から（３）で求めた関数ｇ０を差し引いた分布ｇ１ｘを求め、分布ｇ１ｘのうち強度レベルの大きい方から調べたときの最初の極大値をしきい値（ａ）と定める。ｇ１ｘは、レベル１の分布関数ｇ１とクロスポイントの分布関数ｇｘの重ね合わせと考えられる（図８の（Ｄ））。
（５）：分布ｇ１ｘのうち強度レベルがしきい値（ａ）以上の部分を正規分布ｇ１の一部と仮定し、最小二乗法などによりフィツテングしてレベル１の平均値ｍ１と標準偏差ｓ１をそれぞれ求める（図８の（Ｅ））。
（６）：しきい値（ａ），（ｂ）をそれぞれｍ１，ｍ０とする（図８の（Ｆ））。
（７）：（５）で求めた平均値と標準偏差から
Ｑａｖｇ＝｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）
で求まるＱ値を平均Ｑ値パラメータとし、ｓ１を波形劣化パラメータとする。分布関数ｇ０，ｇ１としてはカイ二乗分布を仮定することもできる（参照文献［４］）。
【００４６】
図９における平均Ｑ値パラメータおよび波形劣化パラメータ評価アルゴリズムは以下の通りである。
（１）：光信号振幅ヒストグラム測定部１０３から得られる光信号振幅ヒストグラムに対して（図９の（Ａ））、
（２）：振幅ヒストグラムのうち強度レベルの大きい方から調べたときの最初の極大値をしきい値（ａ）、振幅ヒストグラムのうち強度レベルの小さい方から調べたときの最初の極大値をしきい値（ｂ）と定める（図９の（Ｂ））。
（３）：振幅ヒストグラムのうち、強度レベルがしきい値（ａ）以上の部分を正規分布ｇ１と仮定し、
しきい値（ｂ）以下の部分を正規分布ｇ０と仮定し、最小二乗法などによりフィッテングして、
最小二乗法などによりフィッテングしてレベル１の平均値ｍ１と標準偏差ｓ１、レベル０の平均値ｍ０と標準偏差ｓ０を求める（図９の（Ｃ））。
（４）：（３）で求めた平均値と標準偏差から
Ｑａｖｇ＝｜ｍ１−ｍ０｜／（ｓ１＋ｓ０）
で求まるＱ値を平均Ｑ値パラメータとし、ｓ１を波形劣化パラメータとする。分布関数ｇ０，ｇ１としてはカイ二乗分布を仮定することもできる（参考文献［４］）。
【００４７】
本実施形態における、実際の測定結果を図１０、および図１１に示す。
【００４８】
図１０の（Ａ）〜（Ｃ）は、１０Ｇｂｉｔ／ｓＮＲＺ光信号から得られる光信号振幅ヒストグラムを示す。図１０の（Ａ）は波長分散値が３４０ｐｓ／ｎｍ、最小受光パワー−３１ｄＢｍの場合であり、図１０の（Ｂ）は波長分散値が１３６０ｐｓ／ｎｍ、最小受光パワー−３１ｄＢｍの場合であり、図１０の（Ｃ）は波長分散値が３４０ｐｓ／ｎｍ、最小受光パワー−３９ｄＢｍの場合である。
【００４９】
すなわち、図１０の（Ａ）と（Ｂ）の比較では、光信号対雑音比劣化がなく波長分散による波形劣化がある場合の振幅ヒストグラムの変化を確認できるが、レベル１（振幅の大きい側のピーク）の分布の標準偏差の増加が見られ、それによる平均Ｑ値の減少が予想できる。
【００５０】
図１０の（Ａ）と（Ｃ）の変化では、波長分散による波形劣化がなく光信号対雑音比劣化がある場合の振幅ヒストグラムの変化を確認できるが、レベル１と０の平均値の差の減少が顕著に見られ、それによる平均Ｑ値の減少が予想される。つまり、波形劣化だけの場合と光信号対雑音比劣化だけの場合とで、平均Ｑ値減少の原因が異なる傾向が確認できる。
【００５１】
図１１の（Ａ）、（Ｂ）のグラフは上記の考察を実験的に確認したものである。左右どちらのグラフも波長分散値が３４０ｐｓ／ｎｍ、最小受光パワー−３１ｄＢｍの場合の値を１として各パラメータの変化をプロットしている。
【００５２】
左側の図１１の（Ａ）に示すグラフは、波長分散値の変化に対する平均Ｑ値パラメータの変化、波形劣化パラメータｓ１の変化、レベル０と１の平均値の差の変化を示しており、波長分散値の増加（波形劣化の増大）に伴って、平均Ｑ値パラメータの減少と波形劣化パラメータｓ１の増加が見られる。
【００５３】
右の図１１の（Ｂ）に示すグラフは、最小受光パワーの変化に対する平均Ｑ値パラメータの変化、波形劣化パラメータｓ１の変化、レベル０と１の平均値の差の変化を示しており、最小受光パワーの減少（光信号対雑音比の減少）に伴って、平均Ｑ値パラメータの減少がみられ、波形劣化パラメータｓ１の変化が小さい。これは左側のグラフの波形劣化の場合と区別できる。
【００５４】
（第２の実施形態）
図１２に本発明の第２の実施形態における光信号品質劣化要因監視装置の構成を示す。本実施形態の光信号品質劣化要因監視装置１２０１は、光分岐器１２０３と、光信号振幅ヒストグラム測定部１２０５と、光信号・光雑音強度測定部１２０７と、平均Ｑ値パラメータ評価部１２０９と、光信号対雑音比パラメータ評価部１２１１と、初期状態記憶部１２１３と、光信号品質評価部１２１４とを有する。
【００５５】
光分岐器１２０３は被測定光信号を分岐する。光信号振幅ヒストグラム測定部１２０５は分岐された一方の被測定光信号から光信号振幅ヒストグラムを得る。光信号・光雑音強度測定部１２０７は分岐された他方の被測定光信号から光信号・光雑音強度の測定を行う。平均Ｑ値パラメータ評価部１２０９は光信号振幅ヒストグラム測定部１２０５によって得られる光信号振幅ヒストグラムから光信号品質パラメータである平均Ｑ値パラメータを得る。光信号対雑音比パラメータ評価部１２１１は光信号振幅ヒストグラム測定部１２０５によって得られる光信号・光雑音強度から光信号品質パラメータである光信号対雑音比パラメータを得る。初期状態記憶部１２１３は光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの初期値または初期特性を記憶媒体に記憶する。
【００５６】
光信号品質評価部１２１４は、平均Ｑ値パラメータの測定値と光信号対雑音比パラメータの測定値と、記憶媒体に記憶されている光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと光信号対雑音比パラメータの初期値または初期特性とを利用して光信号品質劣化要因を評価するが、その際に平均Ｑ値パラメータと光信号対雑音比パラメータの両方を規定し評価することによって、光信号品質劣化の主要因が光信号対雑音比劣化なのか、それ以外なのかを判別する。
【００５７】
次に、図１３のフローチャートを参照して、本実施形態における光信号品質劣化要因監視の手順を詳述する。
ステップ１３０１：信号劣化がない状態のシステム導入時に、平均Ｑ値パラメータと光信号対雑音比パラメータの（ａ）…初期値のみ、または（ｂ）…光信号対雑音比劣化依存性を評価する。
ステップ１３０３：その測定結果を初期状態記憶部１２１３に記憶する。（以上、図１２の（Ａ））。
ステップ１３０５：システム運用開始後は一定の時間間隔で平均Ｑ値パラメータと光信号対雑音比パラメータを評価する。
ステップ１３０７：平均Ｑ値パラメータと光信号対雑音比パラメータを測定するごとに、光信号品質評価部１２１４において初期状態記憶部１２１３の初期値または光信号対雑音比劣化依存性グラフと比較する。
ステップ１３０９：初期値からの平均Ｑ値パラメータの劣化を観測した場合、または平均Ｑ値パラメータが初期状態記憶部１２１３の光信号対雑音比劣化依存性グラフのあらかじめ決められたしきい値を下回った場合に、
（ａ）…光信号対雑音比パラメータの変化がないか、もしくは小さいときは、劣化要因は光信号対雑音比劣化以外であると判別する。
（ｂ）…光信号対雑音比パラメータの変化が大きいときは、劣化要因は主に光信号対雑音比劣化であると判別する。（以上、図１２の（Ｂ））。
【００５８】
光信号振幅ヒストグラム測定部１２０５は、図３〜図５に具体例で示すように、電気サンプリングや光サンプリングを用いた方法を利用でき、その詳細は第１の実施形態に述べたとおりである。
【００５９】
平均Ｑ値パラメータ評価部１２０９は、図６〜図９に示すような評価方法が利用できる。その詳細は第１の実施形態に述べたとおりである。
【００６０】
光信号・光雑音強度測定部１２０７には、例えば光スペクトルアナライザを用いることができる。
【００６１】
また、光信号対雑音比パラメータ評価部１２１１では、例えば図１４に示すように、
光信号対雑音比（ＯＳＮＲ）＝１０Ｌｏｇ（光信号強度／光雑音強度）で光信号対雑音比パラメータを評価できる。
【００６２】
（第３の実施形態）
図１５に本発明の第３の実施形態における光信号品質劣化要因監視装置の構成を示す。なお、図１５において、図１２と同様な構成要素には同一符号を付してある。本実施形態の光信号品質劣化要因監視装置１５０１は、光分岐器１２０３と、光信号振幅ヒストグラム測定部１２０５と、光信号・光雑音強度測定部１２０７と、平均Ｑ値パラメータ評価部１５０３と、波形劣化パラメータ評価部１５０５と、光信号対雑音比パラメータ評価部１２１１と、初期状態記憶部１２１３と、光信号品質評価部１２１４とを有する。
【００６３】
光分岐器１２０３は被測定光信号を分岐する。光信号振幅ヒストグラム測定部１２０５は分岐された一方の被測定光信号から光信号振幅ヒストグラムを得る。光信号・光雑音強度測定部１２０７は分岐された他方の被測定光信号から光信号・光雑音の測定を行う。平均Ｑ値パラメータ評価部１５０３は光信号振幅ヒストグラムから光信号品質パラメータである平均Ｑ値パラメータを得る。波形劣化パラメータ評価部１５０５は光信号振幅ヒストグラムから光信号品質パラメータである波形劣化パラメータを得る。光信号対雑音比パラメータ評価部１２１１は光信号・光雑音強度から光信号品質パラメータである光信号対雑音比パラメータを得る。初期状態記憶部１２１３は光信号品質劣化がないシステム導入時の平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの初期値または初期特性を記憶媒体に記憶する。
【００６４】
光信号品質評価部１２１４は、平均Ｑ値パラメータの測定値と波形劣化パラメータの測定値と光信号対雑音比パラメータの測定値と、記憶媒体に記憶されている光信号品質劣化がないシステム導入時の初期値または初期特性とを利用して光信号品質劣化要因を評価するが、その際に平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの全部を規定し評価することによって、光信号品質劣化の主要因が光信号対雑音比劣化なのか、波形劣化なのか、それ以外なのかを判別する。
【００６５】
次に、図１６のフローチャートを参照して、本実施形態における光信号品質劣化要因監視の手順を詳述する。
ステップ１６０１：信号劣化がない状態のシステム導入時に、平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータの
（ａ）…初期値のみ、または（ｂ）…光信号対雑音比劣化依存性を評価する。ステップ１６０３：その測定結果を初期状態記憶部１２１３に記憶する。（以上、図１５の（Ａ））。
ステップ１６０５：システム運用開始後は一定の時間間隔で平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータを評価する。
ステップ１６０７：平均Ｑ値パラメータと波形劣化パラメータと光信号対雑音比パラメータを測定するごとに、光信号品質評価部１２１４において初期状態記憶部１２１３の初期値または光信号対雑音比劣化依存性グラフと比較する。ステップ１６０９：初期値からの平均Ｑ値パラメータの劣化を観測した場合、または平均Ｑ値パラメータが初期状態記憶部１２１３の光信号対雑音比劣化依存性グラフのあらかじめ決められたしきい値を下回った場合に、
（ａ）…波形劣化パラメータの変化がないか、もしくは小さく、かつ、光信号対雑音比パラメータの変化がないか、もしくは小さいときは、劣化要因は波形劣化と光信号対雑音比劣化以外であると判別する。
（ｂ）…光信号対雑音比パラメータの変化が大きいときは、劣化要因は主に光信号対雑音比劣化であると判別する。
（ｃ）…波形劣化パラメータの変化が大きいときは、劣化要因は主に波形劣化であると判別する。（以上、図１５の（Ｂ））。
【００６６】
光信号振幅ヒストグラム測定部１２０５は、図３〜図５に具体例で示すように、電気サンプリングや光サンプリングを用いた方法を利用でき、その詳細は第１の実施形態に述べたとおりである。
【００６７】
平均Ｑ値パラメータ評価部１５０３は、図６〜図９に示すような評価方法が利用できる。その詳細は第１の実施形態に述べたとおりである。
【００６８】
光信号・光雑音強度測定部１２０７と光信号対雑音比パラメータ評価部１２１１は、図１４に示すような評価方法が利用できる。その詳細は第２の実施形態に述べたとおりである。
【００６９】
【発明の効果】
以上説明したように、本発明によれば、光信号品質の劣化要因を監視できるので、サービスあたりの通信容量が大きく、多様な信号形式、信号ビットレートを有するマルチメディアサービスを収容できるような、経済的で信頼性の高い光ネットワークを実現することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態の光信号品質劣化要因監視装置の構成を示すブロック図である。
【図２】本発明の第１の実施形態の光信号品質劣化要因監視装置で利用した光信号劣化要因の推測アルゴリズムを示すフローチャートである。
【図３】図１の光信号振幅ヒストグラム測定部の構成例を示すブロック図である。
【図４】図１の光信号振幅ヒストグラム測定部の他の構成例を示すブロック図である。
【図５】図１の光信号品質劣化要因監視装置におけるヒストグラム評価の方法を示す特性図である。
【図６】図１の光信号品質劣化要因監視装置における平均Ｑ値パラメータおよび波形劣化パラメータ評価のアルゴリズムの第１の例を示す特性図である。
【図７】図１の光信号品質劣化要因監視装置における平均Ｑ値パラメータおよび波形劣化パラメータ評価のアルゴリズムの第２の例を示す特性図である。
【図８】図１の光信号品質劣化要因監視装置における平均Ｑ値パラメータおよび波形劣化パラメータ評価のアルゴリズムの第３の例を示す特性図である。
【図９】図１の光信号品質劣化要因監視装置における平均Ｑ値パラメータおよび波形劣化パラメータ評価のアルゴリズムの第４の例を示す特性図である。
【図１０】図１の光信号品質劣化要因監視装置において１０Ｇｂｉｔ／ｓＮＲＺ光信号から得られる光信号振幅ヒストグラムを示すグラフである。
【図１１】波形劣化だけの場合と光信号対雑音比劣化だけの場合とで、平均Ｑ値減少の原因が異なる傾向を実験的に確認したグラフである。
【図１２】本発明の第２の実施形態の光信号品質劣化要因監視装置の構成を示すブロック図である。
【図１３】本発明の第２の実施形態の光信号品質劣化要因監視装置で利用した光信号劣化要因の推測アルゴリズムを示すフローチャートである。
【図１４】図１２の信号対雑音比パラメータ評価部の特性を示す概念図である。
【図１５】本発明の第３の実施形態の光信号品質劣化要因監視装置の構成を示すブロック図である。
【図１６】本発明の第３の実施形態の光信号品質劣化要因監視装置で利用した光信号劣化要因の推測アルゴリズムを示すフローチャートである。
【図１７】従来の光信号品質監視部の構成例を示すブロック図である。
【符号の説明】
１０１光信号品質劣化要因監視装置
１０３光信号振幅ヒストグラム測定部
１０５平均Ｑ値パラメータ評価部
１０７波形状態記憶部
１１１光信号品質評価部
３０３光電変換部
３０５電気サンプリングオシロスコープ
３０７ヒストグラム評価部
４０５光サンプリングオシロスコープ
１２０１光信号品質劣化要因監視装置
１２０３光分岐器
１２０５光信号振幅ヒストグラム測定部
１２０７光信号・光雑音強度測定部
１２０９平均Ｑ値パラメータ評価部
１２１１信号対雑音比パラメータ評価部
１２１３初期状態記憶部
１２１４光信号品質評価部
１５０１光信号品質劣化要因監視装置
１５０３平均Ｑ値パラメータ評価部
１５０５波形劣化パラメータ評価部
１７０１光信号品質監視部
１７０３光信号振幅ヒストグラム測定部
１７０５平均Ｑ値パラメータ評価部
１７０７光信号品質評価部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for monitoring factors of optical signal quality degradation in optical communication.
[0002]
[Prior art]
In conventional point-to-point communication in optical communication, signals are bundled using optical time division multiplexing (OTDM) in frames provided by a synchronous network.
[0003]
In such optical time division multiplexing, a Synchronous Optical Network (SONET) / Synchronous Digital Hierarchy (SDH) transmission system or the like is used. This SONET / SDH transmission is used. In the system, an overhead is defined in order to perform efficient signal transmission (reference document [1]: ITU-T Recommendation G707), and the overhead is referred to as bit interleaved parity (Bit Interleaved Parity). The parity check is performed between the repeaters and between the multiplexed terminals, thereby obtaining the fault section identification and the switching activation signal.
[0004]
However, in signal quality monitoring systems such as SONET / SDH transmission systems, the bit rate, signal format and modulation format (NRZ (Non Return to Zero) or RZ (Return to Zero)) of the target signal Therefore, a reception system (an error detection circuit comprising a clock extraction circuit, a reception circuit, a frame detection circuit, a parity check circuit, or a collation circuit) is required. In addition, this conventional optical signal monitoring system needs to perform electrical signal processing after replacing the optical signal with an electrical signal, so that considering the economics, It is difficult to apply to an amplification relay system. For example, when a network failure is detected, it is possible to identify in which section the failure has occurred between optical amplification relay systems. Can not.
[0005]
From the above, it is indispensable to construct an economical service transfer network that has a large communication capacity per service and supports various signal formats and signal bit rates. Here, the optical network can expand communication capacity by using optical time division multiplexing or wavelength division multiplexing (WDM), and is extremely transparent in terms of signal bit rate, signal format, and modulation format. Promising.
[0006]
Therefore, as an optical signal quality monitoring method suitable for such an optical network, a method of evaluating an optical signal quality parameter from an amplitude histogram has been proposed (reference [2]: EPC publication number EP0920250A2, US application (unpublished). ) USP Application 09 / 204,001). FIG. 17 shows the configuration of this conventional example. The conventional optical signal quality monitoring unit 1701 includes an optical signal amplitude histogram measurement unit 1703, an average Q value parameter evaluation unit 1705, and an optical signal quality evaluation unit 1707. In the optical signal amplitude histogram measurement unit 1703, the bit rate f ₀ An optical signal amplitude histogram is obtained from the measured optical signal of (bit / s), and an average Q value parameter evaluation unit 1705 evaluates an average Q value parameter, which is an optical signal quality parameter, from the optical signal amplitude histogram. The quality evaluation unit 1707 realizes optical signal quality monitoring by analyzing the average Q value parameter.
[0007]
[Problems to be solved by the invention]
By the way, in recent years, the demand for multimedia services has increased rapidly, and it has become necessary to expand the communication capacity of each service. In addition, video, audio, data, etc. can be efficiently converted into various signal bit rates and signal formats. When the corresponding network is eagerly desired, the degradation factors of the optical signal to be monitored are diversified accordingly, especially the optical signal to noise ratio degradation due to the loss of the transmission optical fiber, the loss in the transmission terminal station, the light source degradation, It is necessary to individually monitor the waveform degradation due to wavelength dispersion in the transmission optical fiber.
[0008]
However, the average Q value parameter in the above-described conventional example is sensitive to optical signal-to-noise ratio deterioration and waveform deterioration due to wavelength dispersion, but the cause of each cannot be determined.
[0009]
The present invention has been made in view of the above points, and its object is to provide an economical and reliable system that can accommodate multimedia services having a large communication capacity per service and having various signal formats and signal bit rates. An optical signal quality degradation factor monitoring method and an optical signal quality degradation factor monitoring device that contribute to realizing a high optical network.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the optical signal quality deterioration factor monitoring method according to claim 1 of the present invention is higher than a predetermined intensity threshold value among amplitude histograms obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value As a parameter, the standard deviation s1 of the standard histogram distribution function g1 of “level 1” is used as a waveform degradation parameter, and an optical amplitude histogram is obtained from the measured optical signal. Optical signal amplitude histogram measurement step to obtain, average Q value parameter evaluation and waveform to obtain the average Q value parameter and the waveform degradation parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement step An optical signal quality deterioration factor is evaluated using the measured value of the average Q value parameter and the measured value of the waveform deterioration parameter obtained in the deterioration parameter evaluation step, the average Q value parameter evaluation and the waveform deterioration parameter evaluation step. An optical signal quality evaluation process, When the average Q value parameter is deteriorated, when the waveform deterioration parameter is increased, it is determined that the main factor of the transmission characteristic deterioration is the waveform deterioration, and when the waveform deterioration parameter is not increased, the main factor of the transmission characteristic deterioration. Discriminate other than waveform deterioration And an optical signal quality evaluation step.
[0011]
In order to achieve the above object, the optical signal quality degradation factor monitoring method according to claim 2 of the present invention is higher than a predetermined intensity threshold value in an amplitude histogram obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value As a parameter, the standard deviation s1 of the standard histogram distribution function g1 of “level 1” is used as a waveform degradation parameter, and an optical amplitude histogram is obtained from the measured optical signal. Optical signal amplitude histogram measurement step to obtain, average Q value parameter evaluation and waveform to obtain the average Q value parameter and the waveform degradation parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement step Initial values or initial characteristics of the average Q value parameter and the waveform deterioration parameter at the time of introduction of the system without deterioration of the optical signal quality obtained by using the deterioration parameter evaluation step, the average Q value parameter evaluation and the waveform deterioration parameter evaluation step. An initial state storage step for storing in a storage medium, a measurement value of the average Q value parameter and a measurement value of the waveform deterioration parameter obtained in the average Q value parameter evaluation and waveform deterioration parameter evaluation step, and the initial state storage step In the first stored in the storage medium The optical signal quality evaluation step of evaluating an optical signal quality degradation factor using the value or the initial characteristics, When the average Q value parameter is deteriorated, when the waveform deterioration parameter is increased, it is determined that the main factor of the transmission characteristic deterioration is the waveform deterioration, and when the waveform deterioration parameter is not increased, the main factor of the transmission characteristic deterioration. Discriminate other than waveform deterioration And an optical signal quality evaluation step.
[0016]
To achieve the above object, the optical signal quality deterioration factor monitoring method according to claim 3 of the present invention is higher than a predetermined intensity threshold value among amplitude histograms obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value The standard deviation s1 of the standard histogram distribution function g1 of “level 1” as a waveform degradation parameter, and the ratio of the optical signal intensity to the optical noise intensity as an optical signal pair. An optical branching step for branching the optical signal to be measured as a sound ratio parameter, an optical signal amplitude histogram measuring step for obtaining an optical signal amplitude histogram from one of the optical signals to be measured branched by the optical branching step, and the optical branching step An optical signal / optical noise intensity measurement step for measuring an optical signal / optical noise from the other optical signal to be measured branched by the optical signal amplitude histogram obtained from the optical signal amplitude histogram measurement step by the optical signal quality parameter An average Q value parameter evaluation and waveform deterioration parameter evaluation step for obtaining the certain average Q value parameter and the waveform deterioration parameter, and an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement step An optical signal-to-noise ratio parameter evaluation step to obtain the optical signal-to-noise ratio parameter, The measured value of the average Q value parameter obtained in the average Q value parameter evaluation step and the waveform deterioration parameter evaluation step, the measured value of the waveform deterioration parameter, and the optical signal to noise ratio obtained in the optical signal to noise ratio parameter evaluation step. An optical signal quality evaluation process for evaluating optical signal quality degradation factors using measured values of parameters, When the average Q value parameter is deteriorated, it is determined that the main factor of transmission characteristic deterioration is waveform deterioration when the waveform deterioration parameter is increased, and when the optical signal-to-noise ratio parameter is increased, the main factor is It is determined that the optical signal-to-noise ratio is deteriorated, and when the waveform deterioration parameter and the optical signal-to-noise ratio parameter are not increased, the main factors are determined to be other than waveform deterioration and optical signal-to-noise ratio deterioration. And an optical signal quality evaluation step.
[0017]
In order to achieve the above object, the optical signal quality degradation factor monitoring method according to claim 4 of the present invention is higher than a predetermined intensity threshold value among amplitude histograms obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value The standard deviation s1 of the standard histogram distribution function g1 of “level 1” as a waveform degradation parameter, and the ratio of the optical signal intensity to the optical noise intensity as an optical signal pair. An optical branching step for branching the optical signal to be measured as a sound ratio parameter, an optical signal amplitude histogram measuring step for obtaining an optical signal amplitude histogram from one of the optical signals to be measured branched by the optical branching step, and the optical branching step An optical signal / optical noise intensity measurement step for measuring an optical signal / optical noise from the other optical signal to be measured branched by the optical signal amplitude histogram obtained from the optical signal amplitude histogram measurement step by the optical signal quality parameter An average Q value parameter evaluation and waveform deterioration parameter evaluation step for obtaining the certain average Q value parameter and the waveform deterioration parameter, and an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement step An optical signal-to-noise ratio parameter evaluation step to obtain the optical signal-to-noise ratio parameter, Average Q value parameter, waveform deterioration parameter, and optical signal obtained by using the average Q value parameter evaluation and waveform deterioration parameter evaluation step and the optical signal-to-noise ratio parameter evaluation step when introducing a system free of optical signal quality deterioration An initial state storage step of storing an initial value or initial characteristic of the noise-to-noise ratio parameter in a storage medium; a measured value of the average Q value parameter obtained in the average Q value parameter evaluation and waveform deterioration parameter evaluation step; and the waveform deterioration There is no degradation in optical signal quality stored in the storage medium in the initial state storage step and the measured value of the parameter, the optical signal-to-noise ratio parameter measurement value obtained in the optical signal-to-noise ratio parameter evaluation step The initial value or initial characteristics of the average Q factor parameter, waveform degradation parameter, and optical signal-to-noise ratio parameter at the time of system introduction Is an optical signal quality evaluation process for evaluating optical signal quality degradation factors using When the average Q value parameter is deteriorated, it is determined that the main factor of transmission characteristic deterioration is waveform deterioration when the waveform deterioration parameter is increased, and when the optical signal-to-noise ratio parameter is increased, the main factor is It is determined that the optical signal-to-noise ratio is deteriorated, and when the waveform deterioration parameter and the optical signal-to-noise ratio parameter are not increased, the main factors are determined to be other than waveform deterioration and optical signal-to-noise ratio deterioration. And an optical signal quality evaluation step.
[0018]
Here, preferably, the optical signal amplitude histogram measurement step includes the bit rate f. ₀ A photoelectric conversion step of converting a measured optical signal of (bit / s) into an electric intensity modulation signal, and a repetition frequency of the electric intensity modulation signal obtained by the photoelectric conversion step is f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n and m are natural numbers, and a is an offset frequency) An electrical sampling process for sampling with a sampling clock, and an optical signal intensity distribution obtained from a sampling signal obtained by the electrical sampling process, and an optical signal intensity distribution within a certain average time A histogram evaluation step of obtaining an optical signal amplitude histogram from the histogram.
[0019]
Preferably, the optical signal amplitude histogram measurement step includes a bit rate f. ₀ (Bit / s) optical signal under measurement, repetition frequency is f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n and m are natural numbers, a is an offset frequency) and the pulse width is the bit rate f ₀ An optical multiplexing step for combining with a sampling optical pulse train that is sufficiently narrower than a (bit / s) time slot; and the combined light combined by the optical multiplexing step, and a nonlinear mutual relationship between the optical signal to be measured and the sampling optical pulse train. A cross-correlation optical signal generation step for obtaining a cross-correlation optical signal by being incident on a nonlinear optical medium for inducing an action, and the cross-correlation optical signal obtained by the cross-correlation optical signal generation step An optical demultiplexing step of demultiplexing from the sampling optical pulse train, a photoelectric conversion step of converting the cross-correlation optical signal demultiplexed by the optical demultiplexing step into an electric intensity modulation signal, and the photoelectric conversion step A histogram that obtains an optical signal intensity distribution from an electrical intensity modulation signal and obtains an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. And an evaluation process.
[0022]
To achieve the above object, the optical signal quality deterioration factor monitoring apparatus according to claim 8 of the present invention is higher than a predetermined intensity threshold value among amplitude histograms obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value As a parameter, the standard deviation s1 of the standard histogram distribution function g1 of “level 1” is used as a waveform degradation parameter, and an optical amplitude histogram is obtained from the measured optical signal. Optical signal amplitude histogram measurement means to obtain, average Q value parameter evaluation and waveform to obtain the average Q value parameter and the waveform degradation parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement means An optical signal quality deterioration factor is evaluated by using the measured value of the average Q value parameter and the measured value of the waveform deterioration parameter obtained by the deterioration parameter evaluation means, the average Q value parameter evaluation and the waveform deterioration parameter evaluation means. Optical signal quality evaluation means, When the average Q value parameter is deteriorated, when the waveform deterioration parameter is increased, it is determined that the main factor of the transmission characteristic deterioration is the waveform deterioration, and when the waveform deterioration parameter is not increased, the main factor of the transmission characteristic deterioration. Discriminate other than waveform deterioration And an optical signal quality evaluation means.
[0023]
To achieve the above object, the optical signal quality deterioration factor monitoring apparatus according to claim 9 of the present invention is higher than a predetermined intensity threshold value among amplitude histograms obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value As a parameter, the standard deviation s1 of the standard histogram distribution function g1 of “level 1” is used as a waveform degradation parameter, and an optical amplitude histogram is obtained from the measured optical signal. Optical signal amplitude histogram measurement means to obtain, average Q value parameter evaluation and waveform to obtain the average Q value parameter and the waveform degradation parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement means The initial values or initial characteristics of the deterioration parameter evaluation means and the average Q value parameter and the waveform deterioration parameter obtained when the system without optical signal quality deterioration is obtained by using the average Q value parameter evaluation and waveform deterioration parameter evaluation means. Initial state storage means for storing in a storage medium; measured value of the average Q value parameter and measured value of the waveform deterioration parameter obtained by the average Q value parameter evaluation and waveform deterioration parameter evaluation means; and the initial state storage means In the first stored in the storage medium The optical signal quality evaluation means for evaluating an optical signal quality degradation factor using the value or the initial characteristics, When the average Q value parameter is deteriorated, when the waveform deterioration parameter is increased, it is determined that the main factor of the transmission characteristic deterioration is the waveform deterioration, and when the waveform deterioration parameter is not increased, the main factor of the transmission characteristic deterioration. Discriminate other than waveform deterioration And an optical signal quality evaluation means.
[0028]
To achieve the above object, the optical signal quality deterioration factor monitoring apparatus according to claim 10 of the present invention is higher than a predetermined intensity threshold value among amplitude histograms obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value The standard deviation s1 of the “level 1” standard histogram distribution function g1 is a waveform degradation parameter, and the ratio of the optical signal intensity to the optical noise intensity is the optical signal. Optical branching means for branching the measured optical signal as a noise ratio parameter, optical signal amplitude histogram measuring means for obtaining an optical signal amplitude histogram from one measured optical signal branched by the optical branching means, and the optical branching means An optical signal / optical noise intensity measuring means for measuring an optical signal / optical noise from the other optical signal to be measured branched by the optical signal amplitude histogram obtained from the optical signal amplitude histogram measuring means by an optical signal quality parameter An average Q value parameter evaluation and waveform deterioration parameter evaluation means for obtaining the average Q value parameter and the waveform deterioration parameter, and an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement means. Optical signal-to-noise ratio parameter evaluation means for obtaining said optical signal-to-noise ratio parameter, The measured value of the average Q value parameter obtained by the average Q value parameter evaluation and waveform deterioration parameter evaluation means, the measured value of the waveform deterioration parameter, and the optical signal to noise ratio obtained by the optical signal to noise ratio parameter evaluation means. An optical signal quality evaluation means for evaluating an optical signal quality degradation factor using a measured value of a parameter, When the average Q value parameter is deteriorated, it is determined that the main factor of transmission characteristic deterioration is waveform deterioration when the waveform deterioration parameter is increased, and when the optical signal-to-noise ratio parameter is increased, the main factor is It is determined that the optical signal-to-noise ratio is deteriorated, and when the waveform deterioration parameter and the optical signal-to-noise ratio parameter are not increased, the main factors are determined to be other than waveform deterioration and optical signal-to-noise ratio deterioration. And an optical signal quality evaluation means.
[0029]
In order to achieve the above object, an optical signal quality degradation factor monitoring apparatus according to claim 11 of the present invention is higher than a predetermined intensity threshold in an amplitude histogram obtained from an optical signal intensity distribution within a certain average time. An amplitude histogram distribution function corresponding to “level 1” assumed from the amplitude histogram portion is set as g1, and an amplitude histogram distribution function corresponding to “level 0” is obtained from a portion lower than a separately determined intensity threshold as g0. The difference between the average value intensities of the distribution functions g1 and g0 | m1-m0 | and the ratio of the standard deviation values of the distribution functions g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value The standard deviation s1 of the “level 1” standard histogram distribution function g1 is a waveform degradation parameter, and the ratio of the optical signal intensity to the optical noise intensity is the optical signal. Optical branching means for branching the measured optical signal as a noise ratio parameter, optical signal amplitude histogram measuring means for obtaining an optical signal amplitude histogram from one measured optical signal branched by the optical branching means, and the optical branching means An optical signal / optical noise intensity measuring means for measuring an optical signal / optical noise from the other optical signal to be measured branched by the optical signal amplitude histogram obtained from the optical signal amplitude histogram measuring means by an optical signal quality parameter An average Q value parameter evaluation and waveform deterioration parameter evaluation means for obtaining the average Q value parameter and the waveform deterioration parameter, and an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement means. Optical signal-to-noise ratio parameter evaluation means for obtaining said optical signal-to-noise ratio parameter, Average Q value parameter, waveform deterioration parameter evaluation means and optical signal-to-noise ratio parameter evaluation means obtained using the average Q value parameter, waveform deterioration parameter, and optical signal at the time of system introduction without optical signal quality deterioration An initial state storage means for storing an initial value or an initial characteristic of the noise-to-noise ratio parameter in a storage medium; a measured value of the average Q value parameter obtained by the average Q value parameter evaluation and waveform deterioration parameter evaluation means; and the waveform deterioration There is no degradation of the optical signal quality stored in the storage medium by the measured value of the parameter, the measured value of the optical signal-to-noise ratio parameter obtained by the optical signal-to-noise ratio parameter evaluation unit, and the initial state storage unit Initial value or initial characteristics of average Q factor parameter, waveform degradation parameter, and optical signal-to-noise ratio parameter at the time of system introduction Is an optical signal quality evaluation means for evaluating degradation factors of optical signal quality using When the average Q value parameter is deteriorated, it is determined that the main factor of transmission characteristic deterioration is waveform deterioration when the waveform deterioration parameter is increased, and when the optical signal-to-noise ratio parameter is increased, the main factor is It is determined that the optical signal-to-noise ratio is deteriorated, and when the waveform deterioration parameter and the optical signal-to-noise ratio parameter are not increased, the main factors are determined to be other than waveform deterioration and optical signal-to-noise ratio deterioration. And an optical signal quality evaluation means.
[0030]
Here, it is preferable that the optical signal amplitude histogram measuring means has a bit rate f. ₀ A photoelectric conversion means for converting a measured optical signal of (bit / s) into an electric intensity modulation signal, and the electric intensity modulation signal obtained by the photoelectric conversion means with a repetition frequency of f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n, m are natural numbers, a is an offset frequency) An electrical sampling means for sampling with a sampling clock, and an optical signal intensity distribution obtained from a sampling signal obtained by the electrical sampling means, and an optical signal intensity distribution within a certain average time Histogram evaluation means for obtaining an optical signal amplitude histogram from the histogram.
[0031]
Preferably, the optical signal amplitude histogram measuring means has a bit rate f. ₀ (Bit / s) optical signal under measurement, repetition frequency is f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n and m are natural numbers, a is an offset frequency) and the pulse width is the bit rate f ₀ An optical multiplexing unit that multiplexes with a sampling optical pulse train that is sufficiently narrower than a (bit / s) time slot, and a non-linear mutual between the optical signal to be measured and the sampling optical pulse train that is multiplexed by the optical multiplexing unit. A cross-correlation light signal generating means for obtaining a cross-correlation light signal by being incident on a nonlinear optical medium for inducing an action; and the cross-correlation light signal obtained by the cross-correlation light signal generation means and Optical demultiplexing means for demultiplexing from the sampling optical pulse train, photoelectric conversion means for converting the cross-correlation optical signal demultiplexed by the optical demultiplexing means into an electric intensity modulation signal, and the photoelectric conversion means A histogram that obtains an optical signal intensity distribution from an electrical intensity modulation signal and obtains an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. And an evaluation means.
[0032]
Preferably, the optical signal amplitude histogram measuring means has a bit rate f. ₀ The repetition frequency for generating the optical signal under measurement (bit / s) from the sampling clock generation means is f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n, m are natural numbers, a is an offset frequency) optical gate means for sampling, and photoelectric conversion means for receiving a sampling optical signal output from the optical gate means and converting it into a sampling electrical signal; Histogram evaluation means for obtaining an optical signal intensity distribution from the sampling electrical signal obtained by the photoelectric conversion means and obtaining an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
1A and 1B show the configuration of an optical signal quality deterioration factor monitoring apparatus according to the first embodiment of the present invention. The optical signal quality degradation factor monitoring apparatus 101 of this embodiment includes an optical signal amplitude histogram measurement unit 103, an average Q value parameter evaluation unit 105, a waveform degradation parameter evaluation unit 107, an initial state storage unit 109, and an optical signal quality. And an evaluation unit 111.
[0035]
The optical signal amplitude histogram measuring unit 103 obtains an optical amplitude histogram from the measured optical signal. The average Q value parameter evaluation unit 105 obtains an average Q value parameter that is an optical signal quality parameter from the optical signal amplitude histogram. The waveform degradation parameter evaluation unit 107 obtains a waveform degradation parameter that is an optical signal quality parameter from the optical signal amplitude histogram. The initial state storage unit 109 stores, in the storage medium, the average Q-factor parameter and the initial value or initial characteristic of the waveform deterioration parameter when the system is introduced with no optical signal quality deterioration.
[0036]
The optical signal quality evaluation unit 111 uses the measured value of the average Q-factor parameter, the measured value of the waveform deterioration parameter, and the initial value or the initial characteristic stored in the storage medium of the initial state storage unit 109 to obtain the optical signal quality. Degradation factors are evaluated. At that time, by defining and evaluating both the average Q value parameter and the waveform degradation parameter, whether the main cause of optical signal quality degradation is the waveform degradation of the optical signal under measurement, or other factors Is determined.
[0037]
Next, the procedure for monitoring the optical signal quality deterioration factor in this embodiment will be described in detail with reference to the flowchart of FIG.
Step 201: When the system is introduced without any signal degradation, the average Q value parameter and the waveform degradation parameter (a)... Only the initial value or (b)... Optical signal-to-noise ratio degradation dependency are evaluated.
Step 203: The measurement result of step 201 is stored in the initial state storage unit 109. (Thus, (A) of FIG. 1).
Step 205: After starting the system operation, the average Q value parameter and the waveform deterioration parameter are evaluated at regular time intervals.
Step 207: Each time the average Q value parameter and the waveform degradation parameter are measured, the optical signal quality evaluation unit 111 compares these measured values with the initial value of the initial state storage unit 109 or the optical signal-to-noise ratio degradation dependency graph.
Step 209: When the deterioration of the average Q value parameter from the initial value is observed, or when the average Q value parameter falls below a predetermined threshold value of the optical signal-to-noise ratio deterioration dependency graph of the initial state storage unit In addition,
(A)... When there is no change or small change in the waveform deterioration parameter, it is determined that the deterioration factor is other than the waveform deterioration.
(B) When the change in the waveform deterioration parameter is large, it is determined that the deterioration factor is mainly the waveform deterioration. (Thus, (B) of FIG. 1).
[0038]
The optical signal amplitude histogram measurement unit 103 includes a photoelectric conversion unit 303, an electrical sampling oscilloscope 305, and a histogram evaluation unit 307, for example, as shown in FIG. In this configuration, in the photoelectric conversion unit 303, the bit rate f ₀ The optical signal to be measured (bit / s) is converted into an electric intensity modulation signal, and the electric sampling oscilloscope 305 repeats the electric intensity modulation signal with a frequency f. ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n, m are natural numbers, and a is an offset frequency), and the histogram evaluation unit 307 obtains an optical signal intensity distribution from the sampling signal obtained by the sampling oscilloscope 305 as shown in FIG. An optical signal amplitude histogram is obtained from the optical signal intensity distribution within a certain average time.
[0039]
Another example of the optical signal amplitude histogram measurement unit 103 is shown in FIG. The optical signal amplitude histogram measurement unit 103 in this example is configured by an optical sampling oscilloscope 405 and a histogram evaluation unit 307.
[0040]
This optical sampling oscilloscope 405 is a known optical sampling method (reference [3]: H. Takara, S, Kawanishi, A. Yokoo, S. Tomaru, T. Kitoh, and M. Saruwatari, “100 Gbit / s. optical signal eye-diagram measurement with optical sampling using organic nonlinear optical crystal ", Electron, Lett., 24, pp. 2256-2258, 1996.). That is, the optical sampling oscilloscope 405 has a bit rate f. ₀ (Bit / s) optical signal under measurement and repetition frequency f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n and m are natural numbers, a is an offset frequency) and the pulse width is the bit rate f ₀ An optical multiplexing unit that combines a sampling optical pulse train that is sufficiently narrower than a (bit / s) time slot, and a non-linear optical medium that induces a nonlinear interaction between the optical signal to be measured and the sampling optical pulse train. A cross-correlation optical signal generation unit for obtaining a cross-correlation optical signal, an optical demultiplexing unit for demultiplexing the cross-correlation optical signal from the measured optical signal and the sampling optical pulse train, and demultiplexing by the optical demultiplexing unit Photoelectric conversion for converting the cross-correlated optical signal into an electric intensity modulation signal, an optical signal intensity distribution is obtained from the electric intensity modulation signal as shown in FIG. 5, and the optical signal amplitude is calculated from the optical signal intensity distribution within a certain average time. And a histogram evaluation unit for obtaining a histogram.
[0041]
Further, as another example, the optical sampling oscilloscope 405 includes a sampling clock generation unit, a bit rate f ₀ The repetition frequency for generating an optical signal of (bit / s) from the sampling clock generator is as follows:
f ₁ (Hz) (f ₁ = (N / m) f ₀ + A: n and m are natural numbers, a is an offset frequency)
An optical gate section that samples with the sampling clock of the optical signal, a photoelectric conversion section that receives the sampling optical signal output from the optical gate section and converts it into a sampling electric signal, and obtains an optical signal intensity distribution from the sampling electric signal. A histogram evaluation unit that obtains an optical signal amplitude histogram from the optical signal intensity distribution within the average time can be used. Here, for the sampling clock generator, electrical short pulse generation by a synthesized signal generator + comb generator can be used. Further, if necessary, an electric amplifier can be used in the front stage or the rear stage of the comb generator. Further, if necessary, a baseband clipper can be used after the comb generator. For the optical gate portion, gate operation by an electroabsorption optical modulator can be used.
[0042]
In the average Q value parameter evaluation unit 105 and the waveform deterioration parameter evaluation unit 107 in FIG. 1, for example, evaluation methods as shown in FIGS. 6 to 9 can be used.
[0043]
The average Q value parameter and waveform degradation parameter evaluation algorithm in FIG. 6 is as follows.
(1): For the optical signal amplitude histogram ((A) of FIG. 6) obtained from the optical signal amplitude histogram measurement unit 103,
(2): The maximum value when the amplitude histogram is examined from the smaller intensity level is defined as m0 ′ ((B) of FIG. 6).
(3): Next, the number of sampling points is integrated from the sampling point (m0 ′) having the maximum intensity level toward the smaller intensity level,
N (middle) = N (total) x D x M
(Where N (total) is the total number of sampling points, D is the duty ratio of the optical signal (ratio of pulse width and time slot), M is the mark ratio (probability of occurrence of level 1 in digital transmission))
And the minimum level of the integrated sampling point when the integrated value becomes equal is m (middle) ((C) in FIG. 6).
(4): m1 ′ = 2 × {m (middle) −m0 ′}
M1 ′ obtained by (1) in FIG. 6 is determined.
(5): m1'-alpha (m1'-m0 ')
The threshold level (a)
m0 '+ alpha (m1'-m0')
The intensity level obtained with the threshold (b)
(However, alpha is a real number 0 <alpha <0.5)
A distribution whose intensity level is equal to or higher than the threshold value (a) is a level 1 distribution g1, and a distribution whose intensity level is equal to or lower than the threshold value (b) is a level 0 distribution g0. In each of the distributions g1 and g0, the average value m1 , M0 and standard deviations s1, s0 are obtained ((E) of FIG. 6).
(6): From the average and standard deviation obtained in (5)
Qavg = | m1-m0 | / (s1 + s0)
The Q value obtained by the above is set as an average Q value parameter, and s1 is set as a waveform deterioration parameter (WD).
[0044]
The average Q value parameter and waveform deterioration parameter evaluation algorithm in FIG. 7 is as follows.
(1): With respect to the optical signal amplitude histogram obtained from the optical signal amplitude histogram measurement unit 103 ((A) in FIG. 7),
(2): The first maximum value when the amplitude histogram is examined from the smaller intensity level is defined as the threshold value (b) ((B) of FIG. 7).
(3): Integrate the number of sampling points from the sampling point with the maximum intensity level toward the smaller intensity level,
N (middle) = N (total) x D x M
(Where N (total) is the total number of sampling points, D is the duty ratio of the optical signal (ratio of pulse width and time slot), M is the mark ratio (probability of occurrence of level 1 in digital transmission))
The minimum level of the integrated sampling point when the integrated value is equal to the sampling point number N (middle) obtained in step (m) is defined as m (middle) (FIG. 7C).
(4): Threshold value (a) = 2 × {m (middle) −Threshold value (b)}
To determine the threshold value (a) ((D) of FIG. 7).
(5): In the amplitude histogram, a portion having an intensity level equal to or higher than the threshold value (a) is assumed to be a part of the normal distribution g1, and a portion not higher than the threshold value (b) is assumed to be a part of the normal distribution g0. Then, the average values m1 and m0 of level 1 and level 0 and standard deviations s1 and s0 are obtained by fitting using a least square method or the like ((E) of FIG. 7).
(6): From the average and standard deviation obtained in (5)
Qavg = | m1-m0 | / (s1 + s0)
The Q value obtained by the above is the average Q value parameter, and s1 is the waveform deterioration parameter. Chi-square distribution can also be assumed as the distribution functions g0 and g1 (reference [4]: D. Marcuse, “Derivation of Analytical Expressions for the Bit-Error Probability in Lightwave Systems with Optical Amplifiers,” IEEE J. Lightwave. Technol., Vol. 8, No. 12, pp1816-1823, 1990).
[0045]
The average Q value parameter and waveform deterioration parameter evaluation algorithm in FIG. 8 is as follows.
(1): With respect to the optical signal amplitude histogram obtained from the optical signal amplitude histogram measurement unit 103 ((A) in FIG. 8),
(2): The first maximum value when the amplitude histogram is examined from the smaller intensity level is defined as the threshold value (b) ((B) of FIG. 8).
(3): Assuming that the portion of the amplitude histogram whose intensity level is equal to or less than the threshold value (b) is part of the normal distribution g0, fitting is performed by the least square method or the like, and the average value m0 and standard deviation s0 of level 0 Are respectively obtained ((C) of FIG. 8).
(4): A distribution g1x obtained by subtracting the function g0 obtained in (3) from the entire amplitude histogram is obtained, and the first maximum value when the distribution g1x is examined from the higher intensity level is defined as a threshold value (a). Determine. g1x is considered to be a superposition of the distribution function g1 at level 1 and the distribution function gx at the cross point ((D) in FIG. 8).
(5): Assuming that the portion of the distribution g1x whose intensity level is equal to or greater than the threshold value (a) is a part of the normal distribution g1, fitting is performed by the least square method or the like to obtain the average value m1 and the standard deviation s1 of the level 1 Each is obtained ((E) in FIG. 8).
(6): Threshold values (a) and (b) are set to m1 and m0, respectively ((F) in FIG. 8).
(7): From the average and standard deviation obtained in (5)
Qavg = | m1-m0 | / (s1 + s0)
The Q value obtained by the above is the average Q value parameter, and s1 is the waveform deterioration parameter. A chi-square distribution can also be assumed as the distribution functions g0 and g1 (reference document [4]).
[0046]
The average Q value parameter and waveform degradation parameter evaluation algorithm in FIG. 9 is as follows.
(1): With respect to the optical signal amplitude histogram obtained from the optical signal amplitude histogram measuring unit 103 ((A) in FIG. 9),
(2): Threshold value (a) is the first maximum value when the amplitude histogram is examined from the higher intensity level, and is the first maximum value when the amplitude histogram is examined from the smaller intensity level. It is defined as a threshold value (b) ((B) of FIG. 9).
(3): Assuming that the portion of the amplitude histogram whose intensity level is equal to or greater than the threshold value (a) is the normal distribution g1,
Assuming that the portion below the threshold (b) is a normal distribution g0, fitting by the least squares method,
The level 1 average value m1 and standard deviation s1, and the level 0 average value m0 and standard deviation s0 are obtained by fitting using the least square method or the like (FIG. 9C).
(4): From the average and standard deviation obtained in (3)
Qavg = | m1-m0 | / (s1 + s0)
The Q value obtained by the above is the average Q value parameter, and s1 is the waveform deterioration parameter. A chi-square distribution can also be assumed as the distribution functions g0 and g1 (reference document [4]).
[0047]
The actual measurement results in this embodiment are shown in FIG. 10 and FIG.
[0048]
10A to 10C show optical signal amplitude histograms obtained from a 10 Gbit / s NRZ optical signal. 10A shows the case where the chromatic dispersion value is 340 ps / nm and the minimum light receiving power −31 dBm, and FIG. 10B shows the case where the chromatic dispersion value is 1360 ps / nm and the minimum light receiving power −31 dBm. FIG. 10C shows the case where the chromatic dispersion value is 340 ps / nm and the minimum light receiving power is −39 dBm.
[0049]
That is, in the comparison between (A) and (B) in FIG. 10, it is possible to confirm the change in the amplitude histogram when there is no optical signal-to-noise ratio degradation and there is waveform degradation due to wavelength dispersion. An increase in the standard deviation of the distribution of the peak) is observed, and a decrease in the average Q value can be expected.
[0050]
In the changes in FIGS. 10A and 10C, it is possible to confirm the change in the amplitude histogram when there is no waveform deterioration due to wavelength dispersion and there is optical signal-to-noise ratio deterioration, but the difference between the average values of level 1 and 0 The decrease is noticeable, and the average Q value is expected to decrease. That is, it can be confirmed that the cause of the decrease in the average Q value is different between the case of only the waveform deterioration and the case of only the optical signal-to-noise ratio deterioration.
[0051]
The graphs (A) and (B) of FIG. 11 confirm the above consideration experimentally. In both the left and right graphs, changes in each parameter are plotted with a value of 1 when the chromatic dispersion value is 340 ps / nm and the minimum received light power is −31 dBm.
[0052]
The graph shown in FIG. 11A on the left shows changes in the average Q-value parameter, changes in the waveform degradation parameter s1, changes in the difference between the average values of levels 0 and 1, with respect to changes in the chromatic dispersion value. As the variance value increases (increase in waveform deterioration), a decrease in the average Q value parameter and an increase in the waveform deterioration parameter s1 are observed.
[0053]
The graph shown in FIG. 11B on the right shows the change in the average Q value parameter, the change in the waveform deterioration parameter s1, and the change in the difference between the average values of levels 0 and 1 with respect to the change in the minimum received light power. As the received light power decreases (optical signal-to-noise ratio decreases), the average Q value parameter decreases, and the change in the waveform deterioration parameter s1 is small. This can be distinguished from the case of waveform deterioration in the left graph.
[0054]
(Second Embodiment)
FIG. 12 shows the configuration of an optical signal quality deterioration factor monitoring apparatus according to the second embodiment of the present invention. The optical signal quality degradation factor monitoring device 1201 of the present embodiment includes an optical splitter 1203, an optical signal amplitude histogram measurement unit 1205, an optical signal / optical noise intensity measurement unit 1207, an average Q value parameter evaluation unit 1209, A signal-to-noise ratio parameter evaluation unit 1211, an initial state storage unit 1213, and an optical signal quality evaluation unit 1214 are included.
[0055]
The optical splitter 1203 branches the measured optical signal. The optical signal amplitude histogram measuring unit 1205 obtains an optical signal amplitude histogram from one of the branched optical signals to be measured. The optical signal / optical noise intensity measuring unit 1207 measures the optical signal / optical noise intensity from the other branched optical signal to be measured. The average Q value parameter evaluation unit 1209 obtains an average Q value parameter that is an optical signal quality parameter from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement unit 1205. The optical signal-to-noise ratio parameter evaluation unit 1211 obtains an optical signal-to-noise ratio parameter, which is an optical signal quality parameter, from the optical signal / optical noise intensity obtained by the optical signal amplitude histogram measurement unit 1205. The initial state storage unit 1213 stores, in a storage medium, an initial Q value parameter, a waveform deterioration parameter, and an initial value or initial characteristic of an optical signal-to-noise ratio parameter at the time of introduction of the system without optical signal quality deterioration.
[0056]
The optical signal quality evaluation unit 1214 measures the measured value of the average Q-factor parameter, the measured value of the optical signal-to-noise ratio parameter, the average Q-factor parameter and the optical value stored in the storage medium when there is no optical signal quality degradation. The optical signal quality degradation factor is evaluated using the initial value or the initial characteristic of the signal-to-noise ratio parameter. In this case, by defining and evaluating both the average Q-factor parameter and the optical signal-to-noise ratio parameter, It is determined whether the main cause of optical signal quality degradation is optical signal-to-noise ratio degradation or other factors.
[0057]
Next, the procedure for monitoring the optical signal quality deterioration factor in this embodiment will be described in detail with reference to the flowchart of FIG.
Step 1301: At the time of introducing the system in a state where there is no signal deterioration, (a)... Only the initial value of the average Q value parameter and the optical signal to noise ratio parameter, or (b).
Step 1303: The measurement result is stored in the initial state storage unit 1213. (The above is (A) of FIG. 12).
Step 1305: After starting the system operation, the average Q value parameter and the optical signal-to-noise ratio parameter are evaluated at regular time intervals.
Step 1307: Each time the average Q value parameter and the optical signal-to-noise ratio parameter are measured, the optical signal quality evaluation unit 1214 compares the initial value of the initial state storage unit 1213 or the optical signal-to-noise ratio deterioration dependency graph.
Step 1309: When deterioration of the average Q value parameter from the initial value is observed, or the average Q value parameter falls below a predetermined threshold of the optical signal-to-noise ratio deterioration dependency graph of the initial state storage unit 1213 In case,
(A) When the optical signal to noise ratio parameter is not changed or small, Degradation factors other than optical signal-to-noise ratio degradation It is determined that
(B) When the change in the optical signal to noise ratio parameter is large, it is determined that the deterioration factor is mainly the optical signal to noise ratio deterioration. (The above is (B) of FIG. 12).
[0058]
The optical signal amplitude histogram measurement unit 1205 can use a method using electrical sampling or optical sampling, as shown in specific examples in FIGS. 3 to 5, and details thereof are as described in the first embodiment.
[0059]
The average Q-value parameter evaluation unit 1209 can use an evaluation method as shown in FIGS. The details are as described in the first embodiment.
[0060]
For the optical signal / optical noise intensity measurement unit 1207, for example, an optical spectrum analyzer can be used.
[0061]
Further, in the optical signal-to-noise ratio parameter evaluation unit 1211, for example, as shown in FIG.
Optical signal to noise ratio (OSNR) = 10 Log (optical signal intensity / optical noise intensity) The optical signal to noise ratio parameter can be evaluated.
[0062]
(Third embodiment)
FIG. 15 shows the configuration of an optical signal quality deterioration factor monitoring apparatus according to the third embodiment of the present invention. In FIG. 15, the same components as those in FIG. 12 are denoted by the same reference numerals. The optical signal quality degradation factor monitoring device 1501 of this embodiment includes an optical splitter 1203, an optical signal amplitude histogram measuring unit 1205, an optical signal / optical noise intensity measuring unit 1207, an average Q value parameter evaluating unit 1503, and a waveform. A degradation parameter evaluation unit 1505, an optical signal-to-noise ratio parameter evaluation unit 1211, an initial state storage unit 1213, and an optical signal quality evaluation unit 1214 are included.
[0063]
The optical splitter 1203 branches the measured optical signal. The optical signal amplitude histogram measuring unit 1205 obtains an optical signal amplitude histogram from one of the branched optical signals to be measured. The optical signal / optical noise intensity measuring unit 1207 measures the optical signal / optical noise from the other optical signal to be measured branched. The average Q value parameter evaluation unit 1503 obtains an average Q value parameter that is an optical signal quality parameter from the optical signal amplitude histogram. The waveform degradation parameter evaluation unit 1505 obtains a waveform degradation parameter that is an optical signal quality parameter from the optical signal amplitude histogram. The optical signal-to-noise ratio parameter evaluation unit 1211 obtains an optical signal-to-noise ratio parameter that is an optical signal quality parameter from the optical signal / optical noise intensity. The initial state storage unit 1213 stores, in a storage medium, an initial Q value parameter, a waveform deterioration parameter, and an initial value or initial characteristic of an optical signal-to-noise ratio parameter at the time of introduction of the system without optical signal quality deterioration.
[0064]
The optical signal quality evaluation unit 1214 is configured to introduce a measurement value of an average Q value parameter, a measurement value of a waveform deterioration parameter, a measurement value of an optical signal-to-noise ratio parameter, and an optical signal quality deterioration stored in a storage medium. The optical signal quality deterioration factor is evaluated using the initial value or the initial characteristic of the optical signal. At that time, by defining and evaluating all of the average Q value parameter, the waveform deterioration parameter, and the optical signal to noise ratio parameter, the optical signal quality deterioration factor is evaluated. It is determined whether the main cause of signal quality degradation is optical signal-to-noise ratio degradation, waveform degradation, or otherwise.
[0065]
Next, the procedure for monitoring the optical signal quality deterioration factor in this embodiment will be described in detail with reference to the flowchart of FIG.
Step 1601: When the system is introduced without any signal degradation, the average Q-factor parameter, waveform degradation parameter, and optical signal-to-noise ratio parameter are
(A) ... initial value only, or (b) ... optical signal-to-noise ratio degradation dependency is evaluated. Step 1603: The measurement result is stored in the initial state storage unit 1213. (Thus, (A) of FIG. 15).
Step 1605: After starting the system operation, the average Q value parameter, the waveform deterioration parameter, and the optical signal-to-noise ratio parameter are evaluated at regular time intervals.
Step 1607: Each time the average Q value parameter, the waveform deterioration parameter, and the optical signal-to-noise ratio parameter are measured, the optical signal quality evaluation unit 1214 sets the initial value of the initial state storage unit 1213 or the optical signal-to-noise ratio deterioration dependency graph Compare. Step 1609: When deterioration of the average Q value parameter from the initial value is observed, or the average Q value parameter falls below a predetermined threshold value of the optical signal-to-noise ratio deterioration dependency graph of the initial state storage unit 1213 In case,
(A) When there is no change or small change in the waveform deterioration parameter and no change or small change in the optical signal to noise ratio parameter, the deterioration factors are other than the waveform deterioration and the optical signal to noise ratio deterioration. Is determined.
(B) When the change in the optical signal to noise ratio parameter is large, it is determined that the deterioration factor is mainly the optical signal to noise ratio deterioration.
(C) When the change in the waveform deterioration parameter is large, it is determined that the deterioration factor is mainly the waveform deterioration. (The above is (B) of FIG. 15).
[0066]
The optical signal amplitude histogram measurement unit 1205 can use a method using electrical sampling or optical sampling, as shown in specific examples in FIGS. 3 to 5, and details thereof are as described in the first embodiment.
[0067]
The average Q value parameter evaluation unit 1503 can use an evaluation method as shown in FIGS. The details are as described in the first embodiment.
[0068]
The optical signal / optical noise intensity measurement unit 1207 and the optical signal-to-noise ratio parameter evaluation unit 1211 can use an evaluation method as shown in FIG. The details are as described in the second embodiment.
[0069]
【The invention's effect】
As described above, according to the present invention, the degradation factor of the optical signal quality can be monitored, so that the communication capacity per service is large, and multimedia services having various signal formats and signal bit rates can be accommodated. An economical and highly reliable optical network can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical signal quality deterioration factor monitoring apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing an optical signal degradation factor estimation algorithm used in the optical signal quality degradation factor monitoring apparatus according to the first embodiment of the present invention;
3 is a block diagram illustrating a configuration example of an optical signal amplitude histogram measurement unit in FIG. 1; FIG.
4 is a block diagram showing another configuration example of the optical signal amplitude histogram measurement unit in FIG. 1. FIG.
5 is a characteristic diagram showing a histogram evaluation method in the optical signal quality deterioration factor monitoring apparatus of FIG. 1; FIG.
6 is a characteristic diagram showing a first example of an algorithm for evaluating an average Q value parameter and a waveform deterioration parameter in the optical signal quality deterioration factor monitoring apparatus of FIG. 1; FIG.
7 is a characteristic diagram showing a second example of an algorithm for evaluating an average Q value parameter and a waveform deterioration parameter in the optical signal quality deterioration factor monitoring apparatus of FIG. 1; FIG.
8 is a characteristic diagram showing a third example of an algorithm for evaluating an average Q value parameter and a waveform deterioration parameter in the optical signal quality deterioration factor monitoring device of FIG. 1; FIG.
FIG. 9 is a characteristic diagram showing a fourth example of an algorithm for evaluating an average Q value parameter and a waveform deterioration parameter in the optical signal quality deterioration factor monitoring apparatus of FIG. 1;
10 is a graph showing an optical signal amplitude histogram obtained from a 10 Gbit / s NRZ optical signal in the optical signal quality deterioration factor monitoring apparatus of FIG. 1;
FIG. 11 is a graph experimentally confirming a tendency in which the cause of the average Q value decrease is different between only the waveform deterioration and only the optical signal-to-noise ratio deterioration.
FIG. 12 is a block diagram illustrating a configuration of an optical signal quality deterioration factor monitoring apparatus according to a second embodiment of this invention.
FIG. 13 is a flowchart showing an optical signal deterioration factor estimation algorithm used in the optical signal quality deterioration factor monitoring apparatus according to the second embodiment of the present invention;
14 is a conceptual diagram illustrating characteristics of a signal-to-noise ratio parameter evaluation unit in FIG. 12;
FIG. 15 is a block diagram showing a configuration of an optical signal quality deterioration factor monitoring apparatus according to a third embodiment of the present invention.
FIG. 16 is a flowchart showing an optical signal degradation factor estimation algorithm used in the optical signal quality degradation factor monitoring apparatus according to the third embodiment of the present invention;
FIG. 17 is a block diagram illustrating a configuration example of a conventional optical signal quality monitoring unit.
[Explanation of symbols]
101 Optical signal quality degradation factor monitoring device
103 Optical signal amplitude histogram measurement unit
105 Average Q-value parameter evaluation unit
107 Waveform state storage unit
111 Optical signal quality evaluation unit
303 Photoelectric converter
305 Electric sampling oscilloscope
307 Histogram evaluation unit
405 Optical sampling oscilloscope
1201 Optical signal quality deterioration factor monitoring device
1203 Optical splitter
1205 Optical signal amplitude histogram measurement unit
1207 Optical signal / noise intensity measurement unit
1209 Average Q factor parameter evaluation unit
1211 Signal to Noise Ratio Parameter Evaluation Unit
1213 Initial state storage unit
1214 Optical signal quality evaluation unit
1501 Optical Signal Quality Deterioration Factor Monitoring Device
1503 Average Q-value parameter evaluation unit
1505 Waveform degradation parameter evaluation unit
1701 Optical signal quality monitoring unit
1703 Optical signal amplitude histogram measurement unit
1705 Average Q factor parameter evaluation unit
1707 Optical signal quality evaluation section

Claims

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. ,
An optical signal amplitude histogram measurement step for obtaining an optical amplitude histogram from the optical signal under measurement;
An average Q value parameter evaluation and a waveform deterioration parameter evaluation step for obtaining the average Q value parameter and the waveform deterioration parameter that are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement step;
In the optical signal quality evaluation step of evaluating the optical signal quality deterioration factor using the average Q value parameter measurement value and the waveform deterioration parameter measurement value obtained in the average Q value parameter evaluation and waveform deterioration parameter evaluation step. When the average Q value parameter is deteriorated, when the waveform deterioration parameter is increased, it is determined that the main factor of the transmission characteristic deterioration is waveform deterioration, and when the waveform deterioration parameter is not increased, the transmission characteristic deterioration is performed. An optical signal quality degradation factor monitoring method comprising: an optical signal quality evaluation step for discriminating that the main factor is other than waveform degradation .

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. ,
An optical signal amplitude histogram measurement step for obtaining an optical amplitude histogram from the optical signal under measurement;
An average Q value parameter evaluation and a waveform deterioration parameter evaluation step for obtaining the average Q value parameter and the waveform deterioration parameter that are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement step;
An initial value obtained by using the average Q value parameter evaluation and waveform deterioration parameter evaluation steps and storing the initial value or initial characteristic of the average Q value parameter and the waveform deterioration parameter at the time of system introduction without optical signal quality deterioration in a storage medium A state storage process;
The measured value of the average Q value parameter and the measured value of the waveform deterioration parameter obtained in the average Q value parameter evaluation and waveform deterioration parameter evaluation step, and the initial value stored in the storage medium in the initial state storage step Optical signal quality evaluation step of evaluating an optical signal quality degradation factor using the value or the initial characteristic, and when the average Q value parameter is degraded and the waveform degradation parameter is increased, the transmission characteristic An optical signal quality characterized in that the main factor of deterioration is determined as waveform deterioration, and when the waveform deterioration parameter is not increased, an optical signal quality evaluation step is performed to determine that the main factor of transmission characteristic deterioration is other than waveform deterioration. Deterioration factor monitoring method.

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. The ratio of optical signal intensity to optical noise intensity is used as an optical signal to noise ratio parameter.
An optical branching process for branching the optical signal under measurement;
An optical signal amplitude histogram measuring step for obtaining an optical signal amplitude histogram from one of the optical signals to be measured branched by the optical branching step;
An optical signal / optical noise intensity measuring step for measuring an optical signal / optical noise from the other optical signal under measurement branched by the optical branching step;
An average Q value parameter evaluation and a waveform deterioration parameter evaluation step for obtaining the average Q value parameter and the waveform deterioration parameter, which are optical signal quality parameters, from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement step;
An optical signal-to-noise ratio parameter evaluation step for obtaining the optical signal-to-noise ratio parameter that is an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement step;
The measurement value of the average Q value parameter obtained in the average Q value parameter evaluation step and the waveform deterioration parameter evaluation step, the measurement value of the waveform deterioration parameter, and the optical signal to noise obtained in the optical signal to noise ratio parameter evaluation step. An optical signal quality evaluation step for evaluating an optical signal quality deterioration factor by using a measured value of a ratio parameter, wherein when the average Q value parameter is deteriorated and the waveform deterioration parameter is increased, transmission characteristic deterioration When the optical signal-to-noise ratio parameter is increased, the main factor is determined as the optical signal-to-noise ratio deterioration, and the waveform deterioration parameter and the optical signal-to-noise ratio parameter are increased. Optical signal quality degradation factor monitoring, characterized in that it has an optical signal quality evaluation process for discriminating main factors other than waveform degradation and optical signal-to-noise ratio degradation. Visual method.

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. The ratio of optical signal intensity to optical noise intensity is used as an optical signal to noise ratio parameter.
An optical branching process for branching the optical signal under measurement;
An optical signal amplitude histogram measuring step for obtaining an optical signal amplitude histogram from one of the optical signals to be measured branched by the optical branching step;
An optical signal / optical noise intensity measuring step for measuring an optical signal / optical noise from the other optical signal under measurement branched by the optical branching step;
An average Q value parameter evaluation and a waveform deterioration parameter evaluation step for obtaining the average Q value parameter and the waveform deterioration parameter, which are optical signal quality parameters, from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement step;
An optical signal-to-noise ratio parameter evaluation step for obtaining the optical signal-to-noise ratio parameter that is an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement step;
An average Q value parameter, a waveform deterioration parameter, and a light obtained by using the average Q value parameter evaluation and waveform deterioration parameter evaluation step and the optical signal-to-noise ratio parameter evaluation step when introducing a system without optical signal quality deterioration. An initial state storage step of storing an initial value or initial characteristic of the signal-to-noise ratio parameter in a storage medium;
The measured value of the average Q value parameter obtained in the average Q value parameter evaluation step and the waveform deterioration parameter evaluation step, the measured value of the waveform deterioration parameter, and the optical signal pair obtained in the optical signal to noise ratio parameter evaluation step. The measured value of the noise ratio parameter, the average Q value parameter, the waveform deterioration parameter, and the initial value of the optical signal-to-noise ratio parameter at the time of introducing the system without optical signal quality deterioration stored in the storage medium in the initial state storing step Alternatively, an optical signal quality evaluation step of evaluating an optical signal quality deterioration factor using initial characteristics, and when the average Q value parameter is deteriorated and the waveform deterioration parameter is increased, the transmission characteristic deterioration is When the main factor is determined to be waveform deterioration and the optical signal-to-noise ratio parameter is increased, the main factor is determined to be optical signal-to-noise ratio deterioration, and the wave Optical signal quality degradation factor and having an optical signal quality evaluation step of determining that addition waveform degradation and optical signal-to-noise ratio degradation of the main factors when deterioration parameter and optical signal-to-noise ratio parameter does not increase Monitoring method.

The optical signal amplitude histogram measurement step includes
A photoelectric conversion step of converting an optical signal under measurement having a bit rate f ₀ (bit / s) into an electric intensity modulation signal;
The electrical intensity modulation signal obtained by the photoelectric conversion step is a sampling clock having a repetition frequency of f ₁ (Hz) (f ₁ = (n / m) f ₀ + a: n, m is a natural number, and a is an offset frequency). An electrical sampling process for sampling;
5. A histogram evaluation step of obtaining an optical signal intensity distribution from a sampling signal obtained by the electrical sampling step and obtaining an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. The optical signal quality deterioration factor monitoring method according to any one of the above.

The optical signal amplitude histogram measurement step includes
Pulse the optical signal under measurement at bit rate f ₀ (bit / s) at a repetition frequency of f ₁ (Hz) (f ₁ = (n / m) f ₀ + a: n, m are natural numbers, a is an offset frequency) An optical combining step of combining with a sampling optical pulse train whose width is sufficiently narrower than a time slot having a bit rate f ₀ (bit / s);
A cross-correlation optical signal that obtains a cross-correlation optical signal by causing the combined light combined by the optical multiplexing step to enter a nonlinear optical medium for inducing a nonlinear interaction between the optical signal to be measured and the sampling optical pulse train Generation process,
An optical demultiplexing step of demultiplexing the cross-correlation optical signal obtained by the cross-correlation optical signal generation step from the measured optical signal and the sampling optical pulse train;
A photoelectric conversion step of converting the cross-correlation optical signal demultiplexed by the optical demultiplexing step into an electric intensity modulation signal;
2. A histogram evaluation step of obtaining an optical signal intensity distribution from the electrical intensity modulation signal obtained by the photoelectric conversion step and obtaining an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. 5. The optical signal quality deterioration factor monitoring method according to any one of items 1 to 4.

The optical signal amplitude histogram measurement step includes
The repetition frequency generated from the sampling clock generation step for the optical signal under measurement having the bit rate f ₀ (bit / s) is f ₁ (Hz) (f ₁ = (n / m) f ₀ + a: n, m are natural numbers. , A is an optical gate process for sampling with a sampling clock of an offset frequency),
A photoelectric conversion step of converting a sampling optical signal obtained by the optical gate step into a sampling electric signal;
2. A histogram evaluation step of obtaining an optical signal intensity distribution from the sampling electric signal obtained by the photoelectric conversion step and obtaining an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. 5. The optical signal quality deterioration factor monitoring method according to any one of 4 above.

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. ,
An optical signal amplitude histogram measuring means for obtaining an optical amplitude histogram from the optical signal under measurement;
Average Q value parameter evaluation and waveform deterioration parameter evaluation means for obtaining the average Q value parameter and the waveform deterioration parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement means;
Optical signal quality evaluation means for evaluating an optical signal quality deterioration factor using the measured value of the average Q value parameter and the measured value of the waveform deterioration parameter obtained by the average Q value parameter evaluation and waveform deterioration parameter evaluation means. When the average Q value parameter is deteriorated, when the waveform deterioration parameter is increased, it is determined that the main factor of the transmission characteristic deterioration is waveform deterioration, and when the waveform deterioration parameter is not increased, the transmission characteristic deterioration is performed. An optical signal quality degradation factor monitoring device characterized by comprising: an optical signal quality evaluation means for discriminating that the main factor is other than waveform degradation .

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. ,
An optical signal amplitude histogram measuring means for obtaining an optical amplitude histogram from the optical signal under measurement;
Average Q value parameter evaluation and waveform deterioration parameter evaluation means for obtaining the average Q value parameter and the waveform deterioration parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement means;
An initial value or initial characteristic of the average Q value parameter and the waveform deterioration parameter at the time of introduction of the system without optical signal quality deterioration obtained by using the average Q value parameter evaluation and waveform deterioration parameter evaluation means is stored in a storage medium. State storage means;
The average Q value parameter measurement value and the waveform deterioration parameter measurement value obtained by the average Q value parameter evaluation and waveform deterioration parameter evaluation means, and the initial value stored in the storage medium in the initial state storage means Optical signal quality evaluation means for evaluating an optical signal quality degradation factor using the value or the initial characteristic, and when the average Q value parameter is deteriorated, the transmission characteristic is increased when the waveform deterioration parameter is increased. Optical signal quality characterized by comprising: optical signal quality evaluation means for determining that the main cause of deterioration is waveform deterioration and that the main cause of transmission characteristic deterioration is other than waveform deterioration when the waveform deterioration parameter is not increased Deterioration factor monitoring device.

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. The ratio of optical signal intensity to optical noise intensity is used as an optical signal to noise ratio parameter.
Optical branching means for branching the optical signal under measurement;
An optical signal amplitude histogram measuring means for obtaining an optical signal amplitude histogram from one of the measured optical signals branched by the optical branching means;
An optical signal / optical noise intensity measuring means for measuring an optical signal / optical noise from the other optical signal to be measured branched by the optical branching means;
Average Q value parameter evaluation and waveform deterioration parameter evaluation means for obtaining the average Q value parameter and the waveform deterioration parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement means;
An optical signal-to-noise ratio parameter evaluation unit that obtains the optical signal-to-noise ratio parameter that is an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement unit;
The measured value of the average Q value parameter obtained by the average Q value parameter evaluation and waveform degradation parameter evaluation means, the measured value of the waveform degradation parameter, and the optical signal to noise obtained by the optical signal to noise ratio parameter evaluation means. An optical signal quality evaluation unit that evaluates an optical signal quality deterioration factor using a measured value of a ratio parameter, and when the average Q value parameter is deteriorated, transmission characteristic deterioration occurs when the waveform deterioration parameter is increased. Optical signal quality degradation means comprising: an optical signal quality evaluation means for discriminating that the main cause of waveform degradation is waveform degradation, and that the major factor of transmission characteristic degradation is other than waveform degradation when the waveform degradation parameter is not increased Factor monitoring device.

Among the amplitude histograms obtained from the optical signal intensity distribution within a certain average time, an amplitude histogram distribution function corresponding to “level 1” assumed from an amplitude histogram portion higher than a predetermined intensity threshold is defined as g1, and separately determined. The difference between the distribution function g1 and the average value intensity of g0 | m1−m0 | and the distribution function obtained by setting the amplitude histogram distribution function corresponding to “level 0” as g0 from the portion lower than the intensity threshold The ratio of the sum of standard deviation values of g1 and g0 (s1 + s0) | m1-m0 | / (s1 + s0) is an average Q value parameter, and the standard deviation s1 of the standard histogram distribution function g1 of the “level 1” is a waveform deterioration parameter. The ratio of optical signal intensity to optical noise intensity is used as an optical signal to noise ratio parameter.
Optical branching means for branching the optical signal under measurement;
An optical signal amplitude histogram measuring means for obtaining an optical signal amplitude histogram from one of the measured optical signals branched by the optical branching means;
An optical signal / optical noise intensity measuring means for measuring an optical signal / optical noise from the other optical signal to be measured branched by the optical branching means;
Average Q value parameter evaluation and waveform deterioration parameter evaluation means for obtaining the average Q value parameter and the waveform deterioration parameter which are optical signal quality parameters from the optical signal amplitude histogram obtained by the optical signal amplitude histogram measurement means;
An optical signal-to-noise ratio parameter evaluation unit that obtains the optical signal-to-noise ratio parameter that is an optical signal quality parameter from the optical signal / optical noise intensity obtained by the optical signal / optical noise intensity measurement unit;
The average Q value parameter, waveform deterioration parameter, and light obtained by using the average Q value parameter evaluation and waveform deterioration parameter evaluation means and the optical signal-to-noise ratio parameter evaluation means when introducing a system free from optical signal quality deterioration. Initial state storage means for storing an initial value or initial characteristic of the signal-to-noise ratio parameter in a storage medium;
The measured value of the average Q value parameter obtained by the average Q value parameter evaluation and waveform deterioration parameter evaluation means, the measured value of the waveform deterioration parameter, and the optical signal pair obtained by the optical signal to noise ratio parameter evaluation means. The measured value of the noise ratio parameter, the initial Q value parameter, the waveform deterioration parameter, and the initial value of the optical signal-to-noise ratio parameter at the time of system introduction without optical signal quality deterioration stored in the storage medium by the initial state storage means Alternatively, an optical signal quality evaluation unit that evaluates an optical signal quality degradation factor using initial characteristics, and when the average Q value parameter is degraded and the waveform degradation parameter is increased, transmission characteristic degradation is performed. the main factors to determine the waveform deterioration, the main cause of the transmission characteristic deterioration is determined to other waveform distortion when the waveform deterioration parameter is not increased Optical signal quality degradation factor monitoring device and having a signal quality evaluation means.

The optical signal amplitude histogram measuring means is
Photoelectric conversion means for converting an optical signal to be measured having a bit rate of f ₀ (bit / s) into an electric intensity modulation signal;
The electrical intensity modulation signal obtained by the photoelectric conversion means is a sampling clock whose repetition frequency is f ₁ (Hz) (f ₁ = (n / m) f ₀ + a: n, m is a natural number, and a is an offset frequency). Electrical sampling means for sampling;
12. A histogram evaluation unit that obtains an optical signal intensity distribution from a sampling signal obtained by the electrical sampling unit and obtains an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. The optical signal quality deterioration factor monitoring device according to any one of the above.

The optical signal amplitude histogram measuring means is
Pulse the optical signal under measurement at bit rate f ₀ (bit / s) at a repetition frequency of f ₁ (Hz) (f ₁ = (n / m) f ₀ + a: n, m are natural numbers, a is an offset frequency) Optical multiplexing means for combining with a sampling optical pulse train whose width is sufficiently narrower than a time slot having a bit rate f ₀ (bit / s);
A cross-correlation optical signal for obtaining a cross-correlation optical signal by causing the combined light combined by the optical combining means to enter a nonlinear optical medium for inducing a nonlinear interaction between the optical signal to be measured and the sampling optical pulse train Generating means;
Optical demultiplexing means for demultiplexing the cross-correlated optical signal obtained by the cross-correlated optical signal generating means from the measured optical signal and the sampling optical pulse train;
Photoelectric conversion means for converting the cross-correlation optical signal demultiplexed by the optical demultiplexing means into an electric intensity modulation signal;
9. A histogram evaluation unit that obtains an optical signal intensity distribution from the electrical intensity modulation signal obtained by the photoelectric conversion unit and obtains an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. To 11. The optical signal quality deterioration factor monitoring device according to any one of 11 to 11.

The optical signal amplitude histogram measuring means is
The repetition frequency generated from the sampling clock generating means for the optical signal under measurement having the bit rate f ₀ (bit / s) is f ₁ (Hz) (f ₁ = (n / m) f ₀ + a: n, m are natural numbers. , A is an optical frequency gate means for sampling with a sampling clock),
Photoelectric conversion means for receiving a sampling optical signal output from the optical gate means and converting it into a sampling electric signal;
9. A histogram evaluation unit that obtains an optical signal intensity distribution from the sampling electric signal obtained by the photoelectric conversion unit and obtains an optical signal amplitude histogram from the optical signal intensity distribution within a certain average time. The optical signal quality deterioration factor monitoring device according to any one of claims 11 to 11.