JP2004354209A

JP2004354209A - Optical wavelength measuring method, optical wavelength measuring device, and optical spectrum analysis device

Info

Publication number: JP2004354209A
Application number: JP2003152467A
Authority: JP
Inventors: Takanori Saito; 崇記斉藤
Original assignee: Anritsu Corp
Current assignee: Anritsu Corp
Priority date: 2003-05-29
Filing date: 2003-05-29
Publication date: 2004-12-16

Abstract

<P>PROBLEM TO BE SOLVED: To precisely measure the wavelength of a light without using a reference light source. <P>SOLUTION: The light to be measured is branched to two by a branching means 21, and the intensity Ea of one light Pd is detected by a light receiver 22. The other light Pe is incident on a transmitting element 23 having the transmitting characteristic in that the transmittance to light is changed depending on the wavelength, and the intensity Eb of its outgoing light Pe' is detected by a light receiver 24. A transmittance calculation means 30 calculates the transmittance H of the light to be measured to the transmitting element 23 from the detected two intensities of the light. A wavelength detection means 33 determines the wavelength λx of the light Pc to be measured on the basis of the calculated transmittance H and the transmitting characteristic of the transmitting element 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、光の波長を正確に測定するための技術に関する。
【０００２】
【従来の技術】
光に含まれる各波長成分の強度を測定するための装置として、図１５に示すような光学系を有する光スペクトラム解析装置が従来から用いられていた。
【０００３】
図１５において、入射端子１０ａから入射された被測定光Ｐは、コリメートレンズ１１により平行光Ｐ′に変換されて、回折格子１２に入射される。
【０００４】
回折格子１２は入射した光Ｐ′をその波長に応じた回折角で出射し、その回折格子１２から出射された光Ｐａは、回折格子１２に対して角度を変えることが可能に構成されたミラー１３に入射し、その反射光Ｐｂが回折格子１２へ再入射する。
【０００５】
この反射光Ｐａに対する回折格子１２の出射光のうち、所定の出射角度で出射される光Ｐｃが受光器１４に入射されて、その強度が検出される。
【０００６】
受光器１４に入射される光Ｐｃの波長は、回折格子１２に対するミラー１３の角度によって決定され、ミラー１３を図示しない駆動装置によって所望の角度範囲で往復回転させることにより、受光器１４に入射される光Ｐｃの波長を所望の波長範囲内で掃引することができる。
【０００７】
したがって、回折格子１２に対するミラー１３の角度あるいはその角度に対応した駆動信号の大きさと、受光器１４に実際に入射される光Ｐｃの波長λとの関係を予め求めておき、駆動装置によってミラー１３の角度を変化させたときに、その角度に応じた波長情報と、受光器１４によって検出される光の強度とを対応付けて取得することで、被測定光Ｐのスペクトラム特性を解析することができる。
【０００８】
なお、上記光学系でミラー１３を用いずに、回折格子１２の角度を駆動装置により可変して受光器１４に入射する光の波長を掃引する基本的な光学系により、光の波長と強度の関係を示すスペクトラム特性を解析する技術が、次の特許文献１に開示されている。
【０００９】
【特許文献１】
特開２００２−１６８６９２公報
【００１０】
【発明が解決しようとする課題】
しかしながら、上記のようにミラー１３を動かして波長を変化させる光学系を用いた従来の光スペクトラム解析装置では、駆動信号の大きさとミラー１３の角度との対応関係が経時変化し、得られるスペクトラム特性の強度と波長との関係が合わなくなり、被測定光の正確なスペクトラム特性を解析できなくなるという問題があった。
【００１１】
これを解決するために、例えばガス吸収セルを通過した基準光を入射してその吸収線スペクルのデータを求め、その波長をガス固有の安定な吸収線波長で校正する方法も考えられるが、校正のための作業が煩雑で、装置構成も大掛かりとなり、しかも、被測定光を入射している状態では、その校正された波長精度が得られているとは限らない。
【００１２】
本発明は、この問題を解決し、基準の光源を用いることなく、光の波長を正確に測定できる波長測定方法および装置を提供するとともに、その波長測定方法および装置を用いて、被測定光を入射した状態でスペクトラム特性を正確に求めることができる光スペクトラム解析装置を提供することを目的としている。
【００１３】
【課題を解決するための手段】
前記目的を達成するために、本発明の請求項１の光波長測定方法は、
光に対する透過率が波長によって変化する透過特性を有する透過素子に被測定光を入射するとともに、その入射光の強度と前記透過素子を通過して出射された出射光の強度を検出する段階（Ｓ１）と、
前記検出された入射光と出射光の強度から被測定光の前記透過素子に対する透過率を算出する段階（Ｓ２）と、
算出された透過率と前記透過素子の透過特性とに基づいて、被測定光の波長を求める段階（Ｓ３）とを含んでいる。
【００１４】
また、本発明の請求項２の光波長測定方法は、
光に対する透過率が波長に対して周期的に変化する透過特性を有する第１の透過素子と、光に対する透過率が波長に対して周期的に変化する透過特性で且つ前記第１の透過素子の透過特性と異なる透過特性を有する第２の透過素子に被測定光を入射するとともに、各透過素子についてその入射光の強度と透過素子を通過して出射された出射光の強度をそれぞれ検出する段階（Ｓ１１）と、
前記検出された入射光と出射光の強度から被測定光の前記各透過素子に対する透過率を算出する段階（Ｓ１２）と、
算出された透過率と前記各透過素子の透過特性とに基づいて、被測定光の波長を求める段階（Ｓ１３）とを含んでいる。
【００１５】
また、本発明の請求項３の光波長測定装置は、
被測定光を分岐して異なる複数の光路へ出射する分岐手段（２１）と、
前記分岐手段から第１の光路に出射された光の強度を検出する第１の受光器（２２）と、
光に対する透過率が波長によって変化する透過特性を有し、前記分岐手段から第２の光路に出射された光を通過させる透過素子（２３）と、
前記透過素子を通過した光の強度を検出する第２の受光器（２４）と、
前記第１の受光器および前記第２の受光器によって検出された光の強度から前記透過素子に対する被測定光の透過率を算出する透過率算出手段（３０）と、
前記透過率算出手段によって算出された透過率と前記透過素子の透過特性とに基づいて、被測定光の波長を求める波長検出手段（３３）とを備えている。
【００１６】
また、本発明の請求項４の光波長測定装置は、
被測定光を分岐して異なる複数の光路へ出射する分岐手段（２１）と、
前記分岐手段から第１の光路に出射された光の強度を検出する第１の受光器（２２）と、
光に対する透過率が波長に対して周期的に変化する透過特性を有し、前記分岐手段から第２の光路に出射された光を通過させる第１の透過素子（２３）と、
前記第１の透過素子を通過した光の強度を検出する第２の受光器（２４）と、光に対する透過率が波長に対して周期的に変化する透過特性で且つ前記第１の透過素子の透過特性と異なる透過特性を有し、前記分岐手段から第３の光路に出射された光を通過させる第２の透過素子（２５）と、
前記第２の透過素子を通過した光の強度を検出する第３の受光器（２６）と、前記第１の受光器および前記第２の受光器によって検出された光の強度から前記第１の透過素子に対する被測定光の透過率を算出する第１の透過率算出手段（３０）と、
前記第１の受光器および前記第３の受光器によって検出された光の強度から前記第２の透過素子に対する被測定光の透過率を算出する第２の透過率算出手段（３１）と、
前記第１の透過率算出手段および第２の透過率算出手段によって算出された透過率と前記第１の透過素子および第２の透過素子の透過特性とに基づいて、被測定光の波長を求める波長検出手段（３３′）とを備えている。
【００１７】
また、本発明の請求項５の光スペクトラム解析装置は、
スペクトラム解析の対象となる被測定光を入射するための入射端子（４０ａ）と、
前記入射端子から入射された被測定光を受けて回折する回折格子（４２）と、前記被測定光に対して前記回折格子が回折した光を受けて前記回折格子へ反射させるミラー（４３）と、
前記回折格子に対する前記ミラーの角度を変化させて、該ミラーからの反射光に対して前記回折格子が所定の出射角で出射する光の波長を変化させるとともにその波長に対応した波長情報を出力する波長掃引手段（４７、５０）と、
前記回折格子が前記所定の出射角で出射する光を分岐して複数の光路へ出射する分岐手段（２１）と、
前記分岐手段から第１の光路へ出射された光の強度を検出する第１の受光器（２２）と、
光に対する透過率が波長によって変化する透過特性を有し、前記分岐手段から第２の光路へ出射された光を通過させる透過素子（２３）と、
前記透過素子を通過した光の強度を検出する第２の受光器（２４）と、
前記第１の受光器および第２の受光器によって検出された光の強度を前記波長情報に対応付けて記憶するスペクトラムデータ取得手段（５０）と、
前記スペクトラムデータ取得手段によって取得された光の強度から前記透過素子を通過した光の透過率を算出する透過率算出手段（３０）と、
前記透過率算出手段によって算出された透過率と前記透過素子の透過特性とに基づいて、前記分岐手段に入射された光の波長を求める波長検出手段（３３）と、
前記波長検出手段によって検出された波長に基づいて、前記波長情報を校正する波長校正手段（５５）とを備えている。
【００１８】
また、本発明の請求項６の光スペクトラム解析装置は、
スペクトラム解析の対象となる被測定光を入射するための入射端子（４０ａ）と、
前記入射端子から入射された被測定光を受けて回折する回折格子（４２）と、前記被測定光に対して前記回折格子が回折した光を受けて前記回折格子へ反射させるミラー（４３）と、
前記回折格子に対する前記ミラーの角度を変化させて、該ミラーからの反射光に対して前記回折格子が所定の出射角で出射する光の波長を変化させるとともにその波長に対応した波長情報を出力する波長掃引手段（４７、５０）と、
前記回折格子が前記所定の出射角で出射する光を分岐して複数の光路へ出射する分岐手段（２１′）と、
前記分岐手段から第１の光路へ出射された光の強度を検出する第１の受光器（２２）と、
光に対する透過率が波長に対して周期的に変化する透過特性を有し、前記分岐手段から第２の光路へ出射された光を通過させる第１の透過素子（２３）と、
前記第１の透過素子を通過した光の強度を検出する第２の受光器（２４）と、光に対する透過率が波長に対して周期的に変化する透過特性で且つ前記第１の透過素子と異なる透過特性を有し、前記分岐手段から第３の光路へ出射された光を通過させる第２の透過素子（２５）と、
前記第２の透過素子を通過した光の強度を検出する第３の受光器（２６）と、前記第１の受光器、第２の受光器および第３の受光器によって検出された光の強度を前記波長情報に対応付けて記憶するスペクトラムデータ取得手段（５０′）と、
前記スペクトラムデータ取得手段によって取得された光の強度から前記第１の透過素子を通過した光の透過率を算出する第１の透過率算出手段（３０）と、
前記スペクトラムデータ取得手段によって取得された光の強度から前記第２の透過素子を通過した光の透過率を算出する第２の透過率算出手段（３１）と、
前記第１の透過率算出手段および第２の透過率算出手段によって算出された透過率と前記第１の透過素子および第２の透過素子の透過特性とに基づいて、前記分岐手段に入射された光の波長を求める波長検出手段（３３′）と、
前記波長検出手段によって検出された波長に基づいて、前記波長情報を校正する波長校正手段（５５）とを備えている。
【００１９】
【発明の実施の形態】
以下、図面に基づいて本発明の実施の形態を説明する。
図１は、本発明の波長測定方法の手順を示すフローチャートである。
【００２０】
以下、このフローチャートに基づいて本発明の波長測定方法について説明する。なお、この波長測定方法は、単一波長の被測定光の波長を測定する方法である。
【００２１】
始めに、光に対する透過率が例えば図２に示すように波長の単調変化に対して単調変化する透過特性Ｆを有し、その特性が安定な透過素子に、波長λｘの被測定光を入射するとともに、その入射光の強度Ｅａと透過素子を通過して出射された出射光の強度Ｅｂを検出する（Ｓ１）。
【００２２】
次に、検出された入射光と出射光の強度Ｅａ、Ｅｂから被測定光の透過素子に対する透過率Ｈを、
Ｈ＝Ｅｂ／Ｅａ
の演算によって算出する（Ｓ２）。
【００２３】
なお、透過率は、減衰率（損失）が決まれば一義的に決まる値であるから、以下の説明で「透過」を「減衰」に置き換えてもよい。そのように置き換えた場合も本発明に含まれるものとする。
【００２４】
そして、この算出された透過率Ｈと透過素子の透過特性Ｆとに基づいて、被測定光の波長λｘを求める（Ｓ３）。
【００２５】
ここで、図２に示した透過特性Ｆのように、透過素子の透過率が広い波長範囲内で波長の単調変化に対して単調変化している場合、透過率Ｈが決まれば、波長も一義的に決まる。
【００２６】
したがって、この透過特性Ｆを予め記憶していれば、算出された透過率Ｈから被測定光の波長λｘを特定できる。
【００２７】
この波長測定方法の測定精度は、透過素子の透過特性の安定度によって決まり、その透過特性が極めて安定なものとしては、エタロン（ＥＴＡＲＯＮ）と呼ばれる光学櫛形フィルタを用いることができる。
【００２８】
ただし、このエタロンは、図３に示すように、波長の単調変化に対して透過率がほぼ一定波長間隔で周期的に増減変化する透過特性Ｆａを有しているため、算出された透過率Ｈに対して、一つの波長を特定することができないが、一般的に単一波長の光を測定する場合、その波長の概略値は既知であるから、算出された透過率Ｈに対応する複数の波長のうち、その概略値に最も近いものを被測定光の波長λｘとして選択すればよい。
【００２９】
また、例えば図４に示すように、増減変化の周期が僅かに異なる透過特性Ｆａ、Ｆｂをそれぞれ有する透過素子を用いれば、波長の概略値が全く不明の光の波長を求めることができる。
【００３０】
このように異なる透過特性の透過素子を用いた場合には、図５に示すように、その２つの透過素子に被測定光を入射して、それぞれの入射光の強度Ｅａ、Ｅａ′と通過光の強度Ｅｂ、Ｅｂ′を検出し（Ｓ１１）、その検出された入射光と出射光の強度から被測定光の各透過素子に対する透過率Ｈ１、Ｈ２を、
Ｈ１＝Ｅｂ／Ｅａ
Ｈ２＝Ｅｂ′／Ｅａ′
の演算によって算出する（Ｓ１２）。
【００３１】
そして、一方の透過素子の透過特性Ｆａで透過率がＨ１となる複数の波長のうち、他方の透過素子の透過特性Ｆｂで透過率がＨ２となる波長を、被測定光の波長λｘとして検出する（Ｓ１３）。
【００３２】
次に、上記の波長測定方法を用いた波長測定装置の実施形態について説明する。
【００３３】
図６に示す波長測定装置２０は、波長の概略値がわかっている被測定光を対象とするものであり、被測定光Ｐｃをビームスプリッタ等からなり波長依存性がない分岐手段２１によって２つの光路に分岐する。
【００３４】
なお、分岐手段２１の入射端から第１の光路への透過率をα、第２の光路への透過率をβとし、ともに既知とする。
【００３５】
分岐手段２１から第１の光路へ出射される光Ｐｄは、第１の受光器２２に入射されて、その光の強度に対応した電圧の信号Ｅａに変換されて透過率算出手段３０へ出力される。
【００３６】
また、分岐手段２１から第２の光路へ出射される光Ｐｅは、例えば前記したエタロン等のように透過率が波長に対して周期的に変化する透過特性の透過素子２３に入射され、この透過素子２３を透過した光Ｐｅ′が第２の受光器２４に入射されて、その光の強度に対応した電圧の信号Ｅｂに変換されて透過率算出手段３０へ出力される。
【００３７】
透過率算出手段３０は、第１の受光器２２で検出された光の強度Ｅａと第２の受光器２４で検出された光の強度Ｅｂから、透過素子２３に対する被測定光の透過率Ｈを算出する。
【００３８】
即ち、分岐手段２１に入射される光Ｐｃの強度をＥ０とし、分岐手段２１の出射光路毎の透過率α、βとすれば、第１の受光器２２に入射される光Ｐｄについて、
Ｅａ＝αＥ０
Ｅ０＝Ｅａ／α
が成立する。
【００３９】
したがって、透過素子２３に入射される光Ｐｄの強度は、
βＥ０＝（β／α）Ｅ０
となる。
【００４０】
よって、透過素子２３を通した光の透過率Ｈは、
Ｈ＝Ｅｂ／βＥ０＝（α／β）（Ｅｂ／Ｅａ）
と表され、この式に第１の受光器２２と第２受光器２４の出力を代入することで、透過率Ｈを求めることができる。なお、分岐手段２１の出射光路毎の分岐率が等しい場合には、受光器の出力Ｅａ、Ｅｂの比のみから透過率Ｈを求めることができる。
【００４１】
このようにして算出された透過率Ｈは、波長検出手段３３に出力される。
波長検出手段３３は、予め透過素子２３の透過特性Ｆａを記憶しており、その透過特性、算出された透過率Ｈおよび波長概略値とに基づいて、被測定光の波長λｘを求める。
【００４２】
図７に示す波長測定装置２０′は、波長の概略値が不明な被測定光を対象とするものであり、被測定光Ｐｃを波長依存性のない分岐手段２１′によって３つの光路に分岐する。なお、３つの光路への分岐率はそれぞれα、β、γで既知とする。
【００４３】
分岐手段２１′から第１の光路へ出射される光Ｐｄは、第１の受光器２２に入射されて、その光の強度に対応した電圧の信号Ｅａに変換されて、第１の透過率算出手段３０および第２の透過率算出手段３１に出力される。
【００４４】
また、分岐手段２１′から第２の光路へ出射される光Ｐｅは、前記図４の透過特性Ｆａを有する第１の透過素子２３に入射され、この第１の透過素子２３を透過した光Ｐｅ′が第２の受光器２４に入射されて、その光の強度に対応した電圧の信号Ｅｂに変換されて第１の透過率算出手段３０へ出力される。
【００４５】
また、分岐手段２１′から第３の光路へ出射される光Ｐｆは、第１の透過素子２３と異なる透過特性（図４のＦｂ）を有する第２の透過素子２５に入射され、この第２の透過素子２５を透過した光Ｐｆ′が第３の受光器２６に入射されて、その光の強度に対応した電圧の信号Ｅｃに変換されて第２の透過率算出手段３１へ出力される。
【００４６】
第１の透過率算出手段３０は、前記同様に第１の受光器２２で検出された光の強度Ｅａと第２の受光器２４で検出された光の強度Ｅｂに基づいて、第１の透過素子２３に対する被測定光の透過率Ｈ１を、
Ｈ１＝（α／β）（Ｅｂ／Ｅａ）
の演算によって算出して、波長検出手段３３′に出力する。
【００４７】
また、第２の透過率算出手段３１は、第１の受光器２２で検出された光の強度Ｅａと第３の受光器２６で検出された光の強度Ｅｃに基づいて、第２の透過素子２５に対する被測定光の透過率Ｈ２を、
Ｈ２＝（α／γ）（Ｅｃ／Ｅａ）
の演算によって算出して、波長検出手段３３′に出力する。
【００４８】
この場合でも、分岐手段２１′の出射光路毎の分岐率が等しい場合には、各受光器の出力Ｅａ、Ｅｂ、Ｅｃのみから各透過率Ｈを求めることができる。
【００４９】
波長検出手段３３′は、予め第１の透過素子２３と第２の透過素子２５の透過特性を記憶しており、それらの透過特性および算出された２つの透過率Ｈ１、Ｈ２に基づいて、被測定光の波長λｘを求める。
【００５０】
この波長検出は、前記したように、一方の透過素子２３の透過特性Ｆａで透過率がＨ１となる複数の波長のうち、他方の透過素子２５の透過特性Ｆｂで透過率がＨ２となる波長を、被測定光の波長として検出すればよい。
【００５１】
このように、実施形態の波長測定装置では、透過率が波長に対して変化する透過特性を有する透過素子に被測定光を通過させ、その入射光強度と出射光強度を検出して、その光の透過率を算出し、算出した透過率と透過素子の透過特性とから被測定光の波長を検出している。
【００５２】
このため、基準光源を用いた波長校正を行なうことなく、単一波長の被測定光の波長を正確に求めることができる。
【００５３】
次に、上記波長測定装置を要部として有する光スペクトラム解析装置の実施形態を図８に基づいて説明する。
【００５４】
図８に示している光スペクトラム解析装置４０は、入射端子４０ａに入射されたスペクトラム解析対象の被測定光Ｐをコリメートレンズ４１によって平行光Ｐ′に変換して回折格子４２に入射し、その回折光Ｐａをミラー４３で受けてその反射光Ｐｂを回折格子４２に再入射する。なお、被測定光Ｐが平行光の場合には、コリメートレンズ４１を省略することができる。また、以下の説明では前記した波長測定装置２０、２０′の構成要素と同等のものには同一符号を付している。
【００５５】
ここで、ミラー４３は、例えば図９に示すように構成されている。
即ち、ミラー４３は、半導体基板をエッチングして形成したものであり、外形が矩形の枠状基板４４と、枠状基板４４の中央部に配置され、外形が矩形で一面側に光を高い反射率で反射する反射面が形成された反射板４５と、枠状基板４４の上板４４ａの中間部と反射板４５の上縁中間部の間および下板４４ｂの中間部と反射板４５の下縁中間部の間を連結し、長手方向に沿って捩じれ変形が可能な一対の連結部４６、４６とを有しており、この連結部４６の捩じれ変形により、反射板４５は連結部４６、４６を結ぶ線を中心にして所定角度範囲内で回転できるようになっている。
【００５６】
したがって、このミラー４３の反射板４６の端部に外力を加えることで、反射板４４の角度を可変することができる。
【００５７】
この反射板４５に対して外力を与えるための駆動装置４７としては、静電力を与えるものあるいは電磁力を与えるもののいずれでもよい。
【００５８】
静電力を用いる場合には、例えば反射板４５（ミラー４３全体でもよい）の表面に導電層を形成するとともに、図１０のように、反射板４５の両端部にそれぞれ対向する固定電極４８、４９を設け、反射板４５と固定電極４８、４９の間に電圧Ｖを印加することで、反射板４５の両端と固定電極４８、４９の間に静電引力を生じさせ、反射板４５の角度を変化させる。
【００５９】
例えば、図１０の（ａ）のように、反射板４５と一方の固定電極４８の間に電圧Ｖを印加すれば、反射板４５の左側と固定電極４８との間に静電引力が生じて反射板４５は反時計回り回転して、静電引力と連結部４６、４６の復帰力とが釣り合う角度位置で停止する。
【００６０】
また、図１０の（ｂ）のように、反射板４５と他方の固定電４９の間に電圧Ｖを印加すれば、反射板４５の右側と固定電極４９との間に静電引力が生じて反射板４４は時計回り回転して、静電引力と連結部４６、４６の復帰力とが釣り合う角度位置で停止する。
【００６１】
また、固定電極４８、４９に所定周期で且つ交互に電圧を印加すれば、反射板４５は所定角度範囲内で往復回転することになる。
【００６２】
また、固定電極４８、４９に異なる電圧を同時に印加すれば、反射板４５はその電圧差に応じた角度位置で停止することになる。
【００６３】
なお、ここでは、反射板４５の表面側の両端に対向する位置に固定電極４８、４９を設けていたが、この固定電極４８、４９を反射板４５の背面側にも設けて、反射板４５の動きをより細かく制御することも可能である。
【００６４】
また、図示しないが、電磁力を用いる場合には、例えば、反射板４５の両端部に磁力で引かれる金属層を設け、これと対向するコイルに電流を流して、両者の間に生じた電磁力により、反射板４５の角度を可変したり、所定角度範囲内で往復回転させる。
【００６５】
このように半導体基板をエッチングして構成したミラー４３は、小型に且つ軽量に構成することができ、反射板４５の角度を高速に可変することができる。
【００６６】
なお、ここで示したミラー４３と駆動装置４７の構成は一例であり、最も簡単には平面鏡をステッピングモータ等の回転駆動装置によって回転させる構成としてもよい。
【００６７】
掃引制御手段５０は、駆動装置４７とともに波長掃引手段を構成するものであり、図示しない操作部等によって指定された掃引波長範囲に対応した角度範囲でミラー４３が回転するための駆動信号Ｄを駆動装置４６に出力し、その駆動信号Ｄの大きさに対応する波長情報λを順次出力するとともに、掃引の開始タイミングを示す掃引開始信号Ｓｓと、掃引の終了タイミングを示す掃引終了信号Ｓｅを出力する。
【００６８】
なお、ここでは、波長情報が波長の値そのものを表し、その波長値を校正する場合について説明するが、この波長情報は、分岐手段２１に入射される光の波長に対応した値であればよく、ミラー４３の角度データ、駆動信号の電圧値、後述するメモリのアドレス値であってもよい。
【００６９】
また、ミラー４３からの反射光Ｐｂに対して、回折格子４２が所定角度で出射する光Ｐｃは、前記した分岐手段２１によって第１の光路と第２の光路へ分岐出射される。ここで、前記したように、分岐手段２１の第１の光路側への透過率はα、第２の光路側への透過率はβとする。
【００７０】
第１の光路に出射された光Ｐｄは、第１の受光器２２に入射されて、その入射強度に比例した電圧の信号Ｅａ（ｔ）が出力される。
【００７１】
また、第２の光路に出射された光Ｐｅは、波長によって透過率が変化する透過特性を有する透過素子２３に入射され、その透過素子２３を通過した光Ｐｅ′が、第１の受光器２２と等しい受光特性をもつ第２の受光器２４に入射されて、その入射強度に比例した電圧の信号Ｅｂ（ｔ）が出力される。
【００７２】
この透過素子２３の透過特性は任意で、前記した図２の透過特性Ｆや、図３に示したエタロン等の透過特性Ｆａのいずれでもよいが、ここでは、ＷＤＭ光ネットワーク通信で用いられる光の測定を主目的にして、図１１のように、波長間隔ＡがＩＴＵによって規定されている間隔（ＩＴＵグリッドの間隔）に設定され、且つ、そのＩＴＵグリッドの各波長Ｇ１、Ｇ２、…、Ｇｎが透過率の単調変化領域（図１１は単調増加領域の例を示しているが単調減少領域でもよい）に設定された透過特性Ｆａをもっているものとする。
【００７３】
第１の受光器２２の出力信号Ｅａ（ｔ）と第２の受光器２４の出力信号Ｅｂ（ｔ）は、スペクトラムデータ取得手段５１に入力される。
【００７４】
スペクトラムデータ取得手段５１は、入力される信号Ｅａ（ｔ）、Ｅｂ（ｔ）を、掃引制御手段５０から出力される波長情報λの更新周期と同一周期でサンプリングしてディジタル値に変換し、そのサンプル値Ｅａ（ｋ）、Ｅｂ（ｂ）を波長情報λに対応付けてそれぞれメモリ５２、５３に記憶する。
【００７５】
例えば、各ＩＴＵグリッドの近傍にほぼ等しい強さの波長成分を有する光が被測定光Ｐとして入射され、その波長範囲が掃引された場合、第１の受光器２２には、被測定光Ｐに含まれる各波長成分が分岐手段２１を介して入射されて、メモリ５２には、図１２の（ａ）に示すように、その光に含まれる各波長毎の強度Ｅａ（ｋ）のデータ列で表されるスペクトラムデータが記憶されることになる。
【００７６】
また、第２の受光器２４には、被測定光Ｐに含まれる各波長成分が分岐手段２１および透過素子２３を介して入射され、メモリ５３には、図１２の（ｂ）のように、透過素子２３の透過特性の影響を受けた光に含まれる各波長毎の強度Ｅｂ（ｋ）のデータ列で表されるスペクトラムデータが記憶されることになる。
【００７７】
透過率算出手段３０は、メモリ５２、５３に記憶されたスペクトラムデータ、即ち、第１の受光器２２および第２の受光器２４によって検出された光の強度とそれに対応付けされた波長情報とに基づいて、透過素子２３を通過した光の透過率を算出する。
【００７８】
例えば、図１２の（ｂ）に示しているように、メモリ５３に記憶された各サンプル値Ｅｂ（ｋ）のうち、透過素子２３の透過率が単調変化する各波長領域のなかで最も大きな値となるサンプル値Ｅｍ（ｉ１）〜Ｅｍ（ｉｎ）を波長検出対象値として選択し、その各波長検出対象値Ｅｍ（ｉ１）〜Ｅｍ（ｉｎ）と、それに対応した波長情報λ（ｉ）に対応付けされてメモリ５２に記憶されている各サンプル値Ｅａ（ｉ１）〜Ｅａ（ｉｎ）（図１２の（ａ））と、分岐手段２１の透過率α、βとを用いて、各波長毎の透過率を以下のように求める。
【００７９】
Ｈ（ｉ１）＝（α／β）Ｅｍ（ｉ１）／Ｅａ（ｉ１）
Ｈ（ｉ２）＝（α／β）Ｅｍ（ｉ２）／Ｅａ（ｉ２）
……
Ｈ（ｉｎ）＝（α／β）Ｅｍ（ｉｎ）／Ｅａ（ｉｎ）
【００８０】
波長検出手段３３は、透過率算出手段３０によって算出された各透過率Ｈ（ｉ１）〜Ｈ（ｉｎ）と予め記憶されている透過素子２３の透過特性Ｆａとに基づいて、各サンプル値Ｅａ（ｉ１）〜Ｅａ（ｉｎ）の波長λｘ（ｉ１）〜λｘ（ｉｎ）を求める。
【００８１】
ただし、前記したように、エタロンを透過素子２３として用いた場合、算出された透過率から波長を一義的に求めることはできないので、その算出された一つの透過率Ｈ（ｉｊ）（ｊ＝１〜ｎ）に対して透過特性Ｆａから得られる複数の波長のうち、波長検出対象値Ｅｍ（ｉｊ）に対応付けされてメモリ５３に記憶されている波長λ（ｋ）に最も近い波長をその波長検出対象値Ｅｍ（ｉｊ）に対応した正確な波長λｘ（ｉｊ）として選択する。
【００８２】
波長校正手段５５は、波長検出手段３３によって得られた各波長λｘ（ｉ１）〜λｘ（ｉｎ）に基づいて、このスペクトラム解析装置４０の波長情報を校正する。
【００８３】
この波長校正の対象はスペクトラム解析装置の構成に応じて行なえばよく、ここでは、メモリ５２に記憶されている各サンプ値Ｅａ（ｋ）の波長λ（ｋ）を校正する例を示している。
【００８４】
即ち、上記のように、ＷＤＭ光ネットワーク通信で用いられるＩＴＵグリッドの光が入射されて、複数の強度データについての正確な波長が得られた場合には、各波長検出対象値Ｅｍ（ｉｊ）毎に検出された各波長λｘ（ｉｊ）と各波長検出対象値Ｅｍ（ｉｊ）に対応付けられて記憶された波長情報との誤差Δλ（ｉｊ）をそれぞれ求め、掃引制御手段２１が出力する波長情報に対する誤差Δλ（ｉｊ）の変化特性Ｑを例えば図１３のように求める。
【００８５】
そして、この変化特性Ｑに基づいて、メモリ５２に記憶されているスペクトラムデータの各波長情報を減算補正する。
【００８６】
スペクトラム波形表示手段５６は、上記のようにして波長情報が校正されたメモリ５２のスペクトラムデータを読み出すとともに、表示器５７の画面上に、横軸を波長軸、縦軸をパワー軸の直交座標を表示し、その直交座標上にスペクトラムデータの波形を表示させる。
【００８７】
このスペクトラム波形の波長軸は波長校正手段５５によって校正されているため、ＩＴＵグリッド近傍の各スペクトラムの波長と強度を正確に把握できる。
【００８８】
このように、実施形態のスペクトラム解析装置４０では、ミラー４３からの反射光に対して回折格子４２が所定角度で出射する光Ｐｃを２つの光路に分岐し、その一方の分岐光を第１の受光器２２に入射し、その受光器２２の出力から被測定光のスペクトラムデータを求めるとともに、他方の分岐光を波長に対して透過率が変化する安定な透過特性Ｆａを有する透過素子２３に入射し、その通過光を第２の受光器２４に入射して、そのスペクトラムデータを求め、両スペクトラムデータから透過素子２３を通過した光の透過率を算出し、算出された透過率と透過素子２３の透過特性Ｆａとに基づいて、透過素子２３を通過した光の波長を求め、その求めた波長に基づいて被測定光のスペクトラムデータの波長を校正している。
【００８９】
このため、従来のように波長校正用の別光源を用いることなく、簡単な構成で被測定光のスペクトラム測定と波長校正とを並行して行なうことができる。
【００９０】
また、透過素子２３として、所定波長間隔で透過率が周期的に変化する透過特性Ｆａを有するエタロンを用いた場合には、上記のようにＷＤＭ光ネットワーク通信で用いられるＩＴＵグリッドの光のスペクトラム特性を高い波長精度で求めることができる。
【００９１】
なお、上記実施形態の光スペクトラム解析装置４０では、回折格子４２から所定角度で出射された光Ｐｃを２光路に分岐してその一方を第１の受光器２２で受光し、他方を透過素子２３に入射してその通過光を第２の受光器２４で受光していたが、図１４に示すスペクトラム解析装置４０′のように、回折格子４２から所定角度で出射された光Ｐｃを分岐手段２１′によって３光路に分岐し、第１の光路に出射された光Ｐｄを第１の受光器２３で受光し、第２の光路に出射された光Ｐｅを第１の透過素子２３に入射してその通過光Ｐｅ′を第２の受光器２４で受光し、さらに第３の光路に出射された光Ｐｆを第２の透過素子２５に入射してその通過光Ｐｆ′を第３の受光器２６で受光するように構成してもよい。
【００９２】
この構成の場合、前記したように、第２の透過素子２５の透過特性Ｆｂは、第１の透過素子２３の透過特性Ｆａと異なるようにしておく。
【００９３】
そして、前記同様に、波長が掃引されたときの各受光器２２、２４、２６の出力信号Ｅａ（ｔ）、Ｅｂ（ｔ）、Ｅｃ（ｔ）を、スペクトラムデータ取得手段５１′によってサンプリングしてそのサンプル値Ｅａ（ｋ）、Ｅｂ（ｋ）、Ｅｃ（ｋ）を波長情報λに対応付けてそれぞれメモリ５２、５３、５４に記憶する。
【００９４】
そして、第１の透過率算出手段３０は、前記同様にメモリ５２、５３に記憶されたスペクトラムデータに基づいて、第１の透過素子２３を通過した光の透過率Ｈ１（ｉｊ）を求める。また、第２の透過率算出手段３１は、メモリ５２、５４に記憶されたスペクトラムデータに基づいて、第２の透過素子２５を通過した光の透過率Ｈ２（ｉｊ）を求める。
【００９５】
波長検出手段３０′は、波長毎にそれぞれ２組ずつ得られた透過率Ｈ１（ｉｊ）、Ｈ２（ｉｊ）と、２つの透過素子２３、２５の透過特性Ｆａ、Ｆｂとから、各透過率Ｈ１（ｉｊ）、Ｈ２（ｉｊ）によって決まる光の正確な波長λｘ（ｉｊ）を求める。
【００９６】
この場合には、ある波長について得られた２つの透過率Ｈ１（ｉｊ）、Ｈｂ（ｉｊ）から、一義的に一つの波長λｘ（ｉｊ）を求めることができ、前記したように、掃引制御手段５０の波長情報を参照する必要はない。
【００９７】
そして、得られた正確な波長λｘ（ｉｊ）に基づいて、前記同様に波長校正することで、被測定光についてのスペクトラムデータの波長情報を校正できる。
【００９８】
また、上記した実施形態のスペクトラム解析装置４０、４０′では、メモリ５２に記憶されたスペクトラムデータの波長情報を補正していたが、これは本発明を限定するものではなく、掃引制御手段５０が出力する波長情報を校正したり、スペクトラム波形表示手段５６において、表示する波形の波長情報を補正してもよい。
【００９９】
【発明の効果】
以上説明したように、本発明の波長測定方法および装置は、光に対する透過率が波長によって変化する透過特性を有する透過素子に被測定光を入射するとともに、その入射光の強度と透過素子を通過して出射された出射光の強度を検出し、その検出された入射光と出射光の強度から被測定光の透過素子に対する透過率を求め、求めた透過率と透過素子の透過特性とに基づいて、被測定光の波長を求めている。
【０１００】
このため、基準光源を用いることなく、単一波長の被測定光の波長を正確に求めることができる。
【０１０１】
また、光に対する透過率が波長に対して周期的に変化する透過特性を有する第１の透過素子および第２の透過素子に被測定光を入射するとともに、各透過素子についてその入射光の強度と透過素子を通過して出射された出射光の強度をそれぞれ検出し、その検出された入射光と出射光の強度から被測定光の各透過素子に対する透過率を求め、求めた透過率と各透過素子の透過特性とに基づいて、被測定光の波長を求めるようにしたものでは、波長の概略値が不明の単一波長の被測定光の波長も正確に求めることができる。
【０１０２】
また、本発明の光スペクトラム解析装置は、ミラーからの反射光に対して回折格子が所定角度で出射する光に対して、前記波長測定装置と同様の処理を行なって、その光の波長を正確に求め、その求めた波長に基づいて波長情報の校正を行なっている。
【０１０３】
このため、従来のように波長校正用の光を別途用意して入射する必要がなく、被測定光を入射した状態で波長校正を行なうことができる。
【０１０４】
また、透過素子としてエタロンのように透過率が波長に対して周期的に変化する透過特性を有するものを用いた場合、ＷＤＭ光ネットワーク通信で規定されているＩＴＵグリッドの光の波長を正確に解析することができる。
【図面の簡単な説明】
【図１】本発明の波長測定方法の手順を示すフローチャート
【図２】透過素子の特性例を示す図
【図３】透過素子の特性例を示す図
【図４】透過素子の特性例を示す図
【図５】本発明の別の波長測定方法の手順を示すフローチャート
【図６】本発明の光波長測定装置の構成例を示す図
【図７】本発明の別の光波長測定装置の構成例を示す図
【図８】本発明の光スペクトラム解析装置の構成例を示す図
【図９】光スペクトラム解析装置の要部の構成例を示す図
【図１０】実施形態の要部の動作を説明するための図
【図１１】実施形態の要部の特性例を示す図
【図１２】実施形態の要部の動作を説明するための図
【図１３】実施形態の要部の動作を説明するための図
【図１４】本発明の別の光スペクトラム解析装置の構成例を示す図
【図１５】従来装置の構成図
【符号の説明】
２０、２０′……光波長測定装置、２１、２１′……分岐手段、２２、２４、２６……受光器、２３、２５……透過素子、３０、３１……透過率算出手段、３３……波長検出手段、４０……光スペクトラム解析装置、４０ａ……入射端子、４１……コリメートレンズ、４２……回折格子、４３……ミラー、４７……駆動装置、５０……掃引制御手段、５１、５１′……スペクトラムデータ取得手段、５２〜５４……メモリ、５５……波長校正手段、５６……スペクトラム波形表示手段、５７……表示器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for accurately measuring the wavelength of light.
[0002]
[Prior art]
As a device for measuring the intensity of each wavelength component contained in light, an optical spectrum analyzer having an optical system as shown in FIG. 15 has been conventionally used.
[0003]
In FIG. 15, a light P to be measured incident from an incident terminal 10 a is converted into a parallel light P ′ by a collimator lens 11 and is incident on a diffraction grating 12.
[0004]
The diffraction grating 12 emits the incident light P ′ at a diffraction angle corresponding to its wavelength, and the light Pa emitted from the diffraction grating 12 can change the angle with respect to the diffraction grating 12. The reflected light Pb is incident on the diffraction grating 12 again.
[0005]
Of the light emitted from the diffraction grating 12 with respect to the reflected light Pa, the light Pc emitted at a predetermined emission angle is incident on the light receiver 14 and its intensity is detected.
[0006]
The wavelength of the light Pc incident on the photodetector 14 is determined by the angle of the mirror 13 with respect to the diffraction grating 12, and is incident on the photodetector 14 by reciprocating the mirror 13 in a desired angle range by a driving device (not shown). The wavelength of the light Pc can be swept within a desired wavelength range.
[0007]
Therefore, the relationship between the angle of the mirror 13 with respect to the diffraction grating 12 or the magnitude of the drive signal corresponding to the angle and the wavelength λ of the light Pc actually incident on the light receiver 14 is determined in advance, and the mirror 13 When the angle is changed, the spectrum information of the measured light P can be analyzed by acquiring the wavelength information corresponding to the angle and the intensity of the light detected by the light receiver 14 in association with each other. it can.
[0008]
Note that, without using the mirror 13 in the above optical system, the basic optical system that changes the angle of the diffraction grating 12 by a driving device and sweeps the wavelength of the light incident on the photodetector 14 is used. A technique for analyzing a spectrum characteristic indicating a relationship is disclosed in Patent Document 1 below.
[0009]
[Patent Document 1]
JP-A-2002-168692
[0010]
[Problems to be solved by the invention]
However, in the conventional optical spectrum analyzer using the optical system that changes the wavelength by moving the mirror 13 as described above, the correspondence between the magnitude of the drive signal and the angle of the mirror 13 changes with time, and the obtained spectrum characteristic There is a problem that the relationship between the intensity and the wavelength does not match, and it becomes impossible to analyze an accurate spectrum characteristic of the measured light.
[0011]
In order to solve this, for example, a method may be considered in which the reference light that has passed through the gas absorption cell is incident, the data of the absorption line spectrum is obtained, and the wavelength is calibrated with a stable absorption line wavelength inherent to the gas. Is complicated, the configuration of the apparatus becomes large, and in the state where the light to be measured is incident, the calibrated wavelength accuracy is not always obtained.
[0012]
The present invention solves this problem, and provides a wavelength measurement method and apparatus that can accurately measure the wavelength of light without using a reference light source. It is an object of the present invention to provide an optical spectrum analyzer capable of accurately determining a spectrum characteristic in a state where light is incident.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a method for measuring an optical wavelength according to claim 1 of the present invention comprises:
(S1) A step of irradiating the light to be measured on a transmission element having a transmission characteristic whose light transmittance changes according to the wavelength, and detecting the intensity of the incident light and the intensity of the outgoing light emitted through the transmission element. )When,
Calculating a transmittance of the measured light with respect to the transmission element from the detected intensities of the incident light and the emitted light (S2);
Determining a wavelength of the light to be measured based on the calculated transmittance and the transmission characteristics of the transmission element (S3).
[0014]
Further, the optical wavelength measuring method according to claim 2 of the present invention,
A first transmission element having a transmission characteristic in which light transmittance changes periodically with wavelength, and a first transmission element having a transmission characteristic in which light transmittance changes periodically with wavelength; A step of injecting the light to be measured into a second transmission element having a transmission characteristic different from the transmission characteristic, and detecting the intensity of the incident light and the intensity of the output light emitted through the transmission element for each transmission element. (S11),
Calculating the transmittance of the measured light with respect to each of the transmission elements from the detected incident light and the intensity of the emitted light (S12);
Determining a wavelength of the measured light based on the calculated transmittance and the transmission characteristics of each of the transmission elements (S13).
[0015]
Further, the optical wavelength measuring device according to claim 3 of the present invention,
Branching means (21) for branching the light to be measured and emitting the light to a plurality of different optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A transmissive element (23) having a transmissive property in which a transmissivity to light changes depending on a wavelength, and transmitting light emitted from the branching unit to a second optical path;
A second light receiver (24) for detecting the intensity of light passing through the transmission element;
Transmittance calculating means (30) for calculating the transmittance of the light to be measured with respect to the transmission element from the intensities of the light detected by the first light receiver and the second light receiver;
A wavelength detector (33) for obtaining a wavelength of the light to be measured based on the transmittance calculated by the transmittance calculator and the transmission characteristics of the transmission element.
[0016]
Further, the optical wavelength measuring device according to claim 4 of the present invention is:
Branching means (21) for branching the light to be measured and emitting the light to a plurality of different optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A first transmissive element (23) having a transmissive property in which a transmissivity to light periodically changes with respect to a wavelength, and transmitting light emitted from the branching unit to a second optical path;
A second light receiver (24) for detecting the intensity of light passing through the first transmission element; and a transmission characteristic having a transmittance for light that periodically changes with wavelength, and A second transmissive element (25) having a transmissive characteristic different from the transmissive characteristic and transmitting light emitted from the branching means to a third optical path;
A third light receiver that detects the intensity of light that has passed through the second transmission element, and the first light receiver based on the light intensity detected by the first light receiver and the second light receiver. First transmittance calculating means (30) for calculating the transmittance of the measured light with respect to the transmitting element;
Second transmittance calculating means (31) for calculating the transmittance of the light to be measured with respect to the second transmission element from the intensities of the light detected by the first light receiver and the third light receiver;
The wavelength of the light to be measured is determined based on the transmittance calculated by the first transmittance calculating unit and the second transmittance calculating unit and the transmission characteristics of the first transmitting element and the second transmitting element. Wavelength detecting means (33 ').
[0017]
Further, the optical spectrum analyzer according to claim 5 of the present invention,
An input terminal (40a) for inputting light to be measured to be subjected to spectrum analysis,
A diffraction grating (42) that receives and diffracts the light to be measured incident from the incident terminal; and a mirror (43) that receives light that is diffracted by the diffraction grating with respect to the light to be measured and reflects the light to the diffraction grating. ,
The angle of the mirror with respect to the diffraction grating is changed to change the wavelength of light emitted by the diffraction grating at a predetermined emission angle with respect to the reflected light from the mirror, and outputs wavelength information corresponding to the wavelength. Wavelength sweep means (47, 50);
Branching means (21) for branching light emitted by the diffraction grating at the predetermined emission angle and emitting the light to a plurality of optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A transmissive element (23) having a transmissive property in which the transmissivity to light changes according to the wavelength, and transmitting the light emitted from the branching means to the second optical path;
A second light receiver (24) for detecting the intensity of light passing through the transmission element;
Spectrum data acquisition means (50) for storing the intensities of the light detected by the first light receiver and the second light receiver in association with the wavelength information;
Transmittance calculating means (30) for calculating the transmittance of light passing through the transmission element from the intensity of light acquired by the spectrum data acquiring means;
Wavelength detecting means (33) for obtaining the wavelength of light incident on the branching means based on the transmittance calculated by the transmittance calculating means and the transmission characteristics of the transmission element;
Wavelength calibration means (55) for calibrating the wavelength information based on the wavelength detected by the wavelength detection means.
[0018]
Further, the optical spectrum analyzer according to claim 6 of the present invention,
An input terminal (40a) for inputting light to be measured to be subjected to spectrum analysis,
A diffraction grating (42) that receives and diffracts the light to be measured incident from the incident terminal; and a mirror (43) that receives light that is diffracted by the diffraction grating with respect to the light to be measured and reflects the light to the diffraction grating. ,
The angle of the mirror with respect to the diffraction grating is changed to change the wavelength of light emitted by the diffraction grating at a predetermined emission angle with respect to the reflected light from the mirror, and outputs wavelength information corresponding to the wavelength. Wavelength sweep means (47, 50);
Branching means (21 ') for branching the light emitted by the diffraction grating at the predetermined emission angle and emitting the light to a plurality of optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A first transmissive element (23) having a transmissive property in which a transmissivity to light periodically changes with respect to a wavelength, and transmitting light emitted from the branching unit to a second optical path;
A second photodetector (24) for detecting the intensity of light passing through the first transmission element, and a transmission characteristic having a light transmittance that periodically changes with wavelength; A second transmission element (25) having different transmission characteristics and transmitting light emitted from the branching unit to a third optical path;
A third light receiver (26) for detecting the intensity of light passing through the second transmission element; and light intensities detected by the first light receiver, the second light receiver, and the third light receiver. Spectrum data acquisition means (50 ') for storing the spectrum data in association with the wavelength information;
First transmittance calculating means (30) for calculating the transmittance of light passing through the first transmitting element from the intensity of light acquired by the spectrum data acquiring means;
Second transmittance calculating means (31) for calculating the transmittance of light passing through the second transmitting element from the intensity of light acquired by the spectrum data acquiring means;
Based on the transmittance calculated by the first transmittance calculating unit and the second transmittance calculating unit and the transmission characteristics of the first transmitting element and the second transmitting element, the light is incident on the branching unit. Wavelength detection means (33 ') for determining the wavelength of light;
Wavelength calibration means (55) for calibrating the wavelength information based on the wavelength detected by the wavelength detection means.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing the procedure of the wavelength measuring method of the present invention.
[0020]
Hereinafter, the wavelength measuring method of the present invention will be described based on this flowchart. Note that this wavelength measuring method is a method of measuring the wavelength of the measured light having a single wavelength.
[0021]
First, as shown in FIG. 2, for example, as shown in FIG. 2, the light to be measured having the wavelength λx is incident on a transmission element having a transmission characteristic F in which the light has a monotonous change with respect to a monotonous change in the wavelength. At the same time, the intensity Ea of the incident light and the intensity Eb of the emitted light emitted through the transmission element are detected (S1).
[0022]
Next, based on the detected intensities Ea and Eb of the incident light and the emitted light, the transmittance H of the measured light with respect to the transmission element is calculated as:
H = Eb / Ea
(S2).
[0023]
Note that the transmittance is a value that is uniquely determined if the attenuation rate (loss) is determined. Therefore, “transmission” may be replaced with “attenuation” in the following description. Such replacement is also included in the present invention.
[0024]
Then, the wavelength λx of the measured light is obtained based on the calculated transmittance H and the transmission characteristics F of the transmission element (S3).
[0025]
Here, as in the transmission characteristic F shown in FIG. 2, when the transmittance of the transmission element changes monotonically with respect to the monotonous change of the wavelength within a wide wavelength range, if the transmittance H is determined, the wavelength is unambiguous. Is decided.
[0026]
Therefore, if this transmission characteristic F is stored in advance, the wavelength λx of the measured light can be specified from the calculated transmittance H.
[0027]
The measurement accuracy of this wavelength measuring method is determined by the stability of the transmission characteristics of the transmission element. As an extremely stable transmission characteristic, an optical comb filter called an etalon (ETARON) can be used.
[0028]
However, as shown in FIG. 3, the etalon has a transmission characteristic Fa in which the transmittance periodically increases and decreases at a substantially constant wavelength interval with respect to a monotonous change in wavelength. In contrast, one wavelength cannot be specified, but generally when measuring light of a single wavelength, since the approximate value of the wavelength is known, a plurality of wavelengths corresponding to the calculated transmittance H are known. The wavelength closest to the approximate value may be selected as the wavelength λx of the measured light.
[0029]
In addition, as shown in FIG. 4, for example, if a transmission element having transmission characteristics Fa and Fb, each of which has a slightly different increase / decrease change cycle, is used, it is possible to obtain a wavelength of light whose wavelength is not completely known.
[0030]
When the transmission elements having different transmission characteristics are used, as shown in FIG. 5, the light to be measured is incident on the two transmission elements, and the intensities Ea and Ea 'of the respective incident lights and the passing light are shown. (S11), and the transmittances H1 and H2 of the light to be measured with respect to each transmission element are determined from the detected intensities of the incident light and the emitted light.
H1 = Eb / Ea
H2 = Eb '/ Ea'
(S12).
[0031]
Then, among a plurality of wavelengths whose transmittance is H1 in the transmission characteristic Fa of one transmission element, a wavelength whose transmittance is H2 in the transmission characteristic Fb of the other transmission element is detected as the wavelength λx of the light to be measured. (S13).
[0032]
Next, an embodiment of a wavelength measuring device using the above-described wavelength measuring method will be described.
[0033]
The wavelength measuring apparatus 20 shown in FIG. 6 is intended for measuring light whose approximate value of the wavelength is known. The measuring light Pc is split into two beams by a splitting means 21 which is composed of a beam splitter or the like and has no wavelength dependency. Branch into the optical path.
[0034]
The transmittance from the incident end of the branching means 21 to the first optical path is α, and the transmittance to the second optical path is β, both of which are known.
[0035]
The light Pd emitted from the branching unit 21 to the first optical path enters the first light receiver 22, is converted into a voltage signal Ea corresponding to the intensity of the light, and is output to the transmittance calculating unit 30. You.
[0036]
The light Pe emitted from the branching means 21 to the second optical path is incident on a transmission element 23 having a transmission characteristic whose transmittance changes periodically with respect to wavelength, such as the etalon described above. The light Pe ′ transmitted through the element 23 enters the second light receiver 24, is converted into a voltage signal Eb corresponding to the intensity of the light, and is output to the transmittance calculator 30.
[0037]
The transmittance calculating means 30 calculates the transmittance H of the measured light to the transmission element 23 from the light intensity Ea detected by the first light receiver 22 and the light intensity Eb detected by the second light receiver 24. calculate.
[0038]
That is, assuming that the intensity of the light Pc incident on the branching unit 21 is E0 and the transmittances α and β for the respective output optical paths of the branching unit 21, for the light Pd incident on the first light receiver 22,
Ea = αE0
E0 = Ea / α
Holds.
[0039]
Therefore, the intensity of the light Pd incident on the transmission element 23 is
βE0 = (β / α) E0
It becomes.
[0040]
Therefore, the transmittance H of the light passing through the transmission element 23 is
H = Eb / βE0 = (α / β) (Eb / Ea)
The transmittance H can be obtained by substituting the outputs of the first light receiver 22 and the second light receiver 24 into this equation. In addition, when the branching ratios of the output optical paths of the branching unit 21 are equal, the transmittance H can be obtained only from the ratio of the outputs Ea and Eb of the light receiver.
[0041]
The transmittance H calculated in this way is output to the wavelength detecting means 33.
The wavelength detecting means 33 stores the transmission characteristic Fa of the transmission element 23 in advance, and obtains the wavelength λx of the measured light based on the transmission characteristic, the calculated transmittance H, and the approximate wavelength.
[0042]
The wavelength measuring device 20 'shown in FIG. 7 is intended for a light to be measured whose approximate wavelength is unknown, and the light to be measured Pc is branched into three optical paths by a branching means 21' having no wavelength dependency. . Note that the branching rates into the three optical paths are known as α, β, and γ, respectively.
[0043]
The light Pd emitted from the branching means 21 ′ to the first optical path enters the first light receiver 22, is converted into a voltage signal Ea corresponding to the intensity of the light, and calculates a first transmittance. It is output to the means 30 and the second transmittance calculating means 31.
[0044]
The light Pe emitted from the branching means 21 'to the second optical path enters the first transmission element 23 having the transmission characteristic Fa shown in FIG. 4, and the light Pe transmitted through the first transmission element 23. Is incident on the second light receiver 24, converted into a voltage signal Eb corresponding to the intensity of the light, and output to the first transmittance calculating means 30.
[0045]
The light Pf emitted from the branching unit 21 ′ to the third optical path is incident on the second transmission element 25 having a transmission characteristic (Fb in FIG. 4) different from that of the first transmission element 23, Is transmitted to the third light receiver 26, is converted into a voltage signal Ec corresponding to the intensity of the light, and is output to the second transmittance calculating means 31.
[0046]
The first transmittance calculating means 30 performs the first transmission based on the light intensity Ea detected by the first light receiver 22 and the light intensity Eb detected by the second light receiver 24 in the same manner as described above. The transmittance H1 of the measured light to the element 23 is
H1 = (α / β) (Eb / Ea)
And outputs it to the wavelength detecting means 33 '.
[0047]
Further, the second transmittance calculating means 31 calculates the second transmission element based on the light intensity Ea detected by the first light receiver 22 and the light intensity Ec detected by the third light receiver 26. 25, the transmittance H2 of the light to be measured is
H2 = (α / γ) (Ec / Ea)
And outputs it to the wavelength detecting means 33 '.
[0048]
Even in this case, when the branching ratio of each of the output optical paths of the branching unit 21 'is equal, each transmittance H can be obtained only from the outputs Ea, Eb, and Ec of each light receiver.
[0049]
The wavelength detecting means 33 'stores transmission characteristics of the first transmission element 23 and the second transmission element 25 in advance, and based on the transmission characteristics and the calculated two transmittances H1 and H2, the wavelength detection means 33'. The wavelength λx of the measurement light is obtained.
[0050]
As described above, the wavelength detection detects the wavelength at which the transmittance becomes H2 at the transmission characteristic Fb of the other transmission element 25 among the plurality of wavelengths at which the transmittance becomes H1 at the transmission characteristic Fa of one transmission element 23, as described above. , May be detected as the wavelength of the light to be measured.
[0051]
As described above, in the wavelength measuring device of the embodiment, the light to be measured is passed through the transmission element having the transmission characteristic in which the transmittance changes with respect to the wavelength, and the intensity of the incident light and the intensity of the emitted light are detected. Is calculated, and the wavelength of the light to be measured is detected from the calculated transmittance and the transmission characteristics of the transmission element.
[0052]
Therefore, the wavelength of the light to be measured having a single wavelength can be accurately obtained without performing the wavelength calibration using the reference light source.
[0053]
Next, an embodiment of an optical spectrum analyzer having the wavelength measuring device as a main part will be described with reference to FIG.
[0054]
The optical spectrum analyzer 40 shown in FIG. 8 converts the light to be measured P, which is incident on the incident terminal 40a, into the parallel light P ′ by the collimating lens 41, enters the diffraction grating 42, The light Pa is received by the mirror 43 and the reflected light Pb is re-incident on the diffraction grating 42. When the measured light P is parallel light, the collimator lens 41 can be omitted. In the following description, the same components as those of the above-described wavelength measuring devices 20 and 20 'are denoted by the same reference numerals.
[0055]
Here, the mirror 43 is configured, for example, as shown in FIG.
That is, the mirror 43 is formed by etching a semiconductor substrate, and is disposed at a central portion of the frame-shaped substrate 44 having a rectangular outer shape, and has a rectangular outer shape and highly reflects light on one side. Between the middle part of the upper plate 44a of the frame-shaped substrate 44 and the middle part of the upper edge of the reflector 45, and the middle part of the lower plate 44b and the lower part of the reflector 45. It has a pair of connecting portions 46, 46 that connect between the edge intermediate portions and can be twisted and deformed along the longitudinal direction. The reflecting plate 45 is connected to the connecting portions 46, Rotation is possible within a predetermined angle range around a line connecting 46.
[0056]
Therefore, by applying an external force to the end of the reflection plate 46 of the mirror 43, the angle of the reflection plate 44 can be changed.
[0057]
The driving device 47 for applying an external force to the reflection plate 45 may be either a device for applying an electrostatic force or a device for applying an electromagnetic force.
[0058]
When an electrostatic force is used, for example, a conductive layer is formed on the surface of the reflection plate 45 (or the entire mirror 43), and the fixed electrodes 48 and 49 respectively oppose both ends of the reflection plate 45 as shown in FIG. Is provided, and a voltage V is applied between the reflector 45 and the fixed electrodes 48 and 49, thereby generating an electrostatic attraction between both ends of the reflector 45 and the fixed electrodes 48 and 49, and changing the angle of the reflector 45. Change.
[0059]
For example, as shown in FIG. 10A, when a voltage V is applied between the reflector 45 and one fixed electrode 48, an electrostatic attraction is generated between the left side of the reflector 45 and the fixed electrode 48. The reflection plate 45 rotates counterclockwise and stops at an angular position where the electrostatic attraction and the return force of the connecting portions 46, 46 are balanced.
[0060]
When a voltage V is applied between the reflector 45 and the other fixed electrode 49 as shown in FIG. 10B, an electrostatic attraction is generated between the right side of the reflector 45 and the fixed electrode 49. The reflection plate 44 rotates clockwise and stops at an angular position where the electrostatic attraction and the return force of the connecting portions 46 and 46 are balanced.
[0061]
Further, when a voltage is applied to the fixed electrodes 48 and 49 alternately in a predetermined cycle, the reflection plate 45 reciprocates within a predetermined angle range.
[0062]
If different voltages are simultaneously applied to the fixed electrodes 48 and 49, the reflecting plate 45 stops at an angular position corresponding to the voltage difference.
[0063]
Here, the fixed electrodes 48 and 49 are provided at positions opposed to both ends on the front surface side of the reflection plate 45. However, the fixed electrodes 48 and 49 are also provided on the back side of the reflection plate 45, Can be controlled more finely.
[0064]
Although not shown, in the case of using electromagnetic force, for example, a metal layer drawn by magnetic force is provided at both ends of the reflection plate 45, and a current is applied to a coil opposed to the metal layer to generate an electromagnetic force generated therebetween. The angle of the reflection plate 45 is changed by the force, or the reflection plate 45 is reciprocated within a predetermined angle range.
[0065]
The mirror 43 formed by etching the semiconductor substrate in this manner can be made small and lightweight, and the angle of the reflection plate 45 can be changed at high speed.
[0066]
Note that the configuration of the mirror 43 and the driving device 47 shown here is merely an example, and it is most simple to use a configuration in which the plane mirror is rotated by a rotary driving device such as a stepping motor.
[0067]
The sweep control means 50 constitutes a wavelength sweep means together with the driving device 47, and drives a drive signal D for rotating the mirror 43 in an angle range corresponding to a sweep wavelength range designated by an operation unit (not shown). It outputs to the device 46, sequentially outputs the wavelength information λ corresponding to the magnitude of the drive signal D, and outputs the sweep start signal Ss indicating the start timing of the sweep and the sweep end signal Se indicating the end timing of the sweep. .
[0068]
Here, the case where the wavelength information represents the value of the wavelength itself and the wavelength value is calibrated will be described. However, the wavelength information may be a value corresponding to the wavelength of the light incident on the branching unit 21. , The angle data of the mirror 43, the voltage value of the drive signal, or the address value of a memory described later.
[0069]
The light Pc emitted from the diffraction grating 42 at a predetermined angle with respect to the reflected light Pb from the mirror 43 is branched and emitted to the first optical path and the second optical path by the above-described branching unit 21. Here, as described above, the transmittance of the branching unit 21 toward the first optical path is α, and the transmittance toward the second optical path is β.
[0070]
The light Pd emitted to the first optical path enters the first light receiver 22 and outputs a signal Ea (t) of a voltage proportional to the incident intensity.
[0071]
The light Pe emitted to the second optical path is incident on a transmission element 23 having a transmission characteristic whose transmittance changes according to the wavelength, and the light Pe ′ passing through the transmission element 23 is converted into a first light receiver 22. And a signal Eb (t) of a voltage proportional to the incident intensity is output.
[0072]
The transmission characteristics of the transmission element 23 may be any of the transmission characteristics F shown in FIG. 2 and the transmission characteristics Fa such as an etalon shown in FIG. For the main purpose of measurement, as shown in FIG. 11, the wavelength interval A is set to the interval defined by the ITU (interval of the ITU grid), and each wavelength G1, G2,. It is assumed that the transmission characteristic Fa is set in a monotonically changing region of the transmittance (FIG. 11 shows an example of a monotonically increasing region, but may be a monotonically decreasing region).
[0073]
The output signal Ea (t) of the first light receiver 22 and the output signal Eb (t) of the second light receiver 24 are input to the spectrum data acquisition means 51.
[0074]
The spectrum data obtaining means 51 samples the input signals Ea (t) and Eb (t) at the same cycle as the update cycle of the wavelength information λ output from the sweep control means 50 and converts the signals into digital values. The sample values Ea (k) and Eb (b) are stored in the memories 52 and 53 in association with the wavelength information λ.
[0075]
For example, when light having a wavelength component of substantially equal intensity is incident as the light to be measured P near each ITU grid and its wavelength range is swept, the first light receiver 22 includes the light to be measured P Each of the wavelength components included is incident via the branching unit 21 and is stored in the memory 52 as a data string of the intensity Ea (k) for each wavelength included in the light, as shown in FIG. The represented spectrum data will be stored.
[0076]
In addition, each wavelength component included in the measured light P is incident on the second light receiver 24 via the branching unit 21 and the transmission element 23, and is input to the memory 53 as shown in FIG. The spectrum data represented by the data string of the intensity Eb (k) for each wavelength included in the light affected by the transmission characteristics of the transmission element 23 is stored.
[0077]
The transmittance calculator 30 converts the spectrum data stored in the memories 52 and 53, that is, the intensity of the light detected by the first light receiver 22 and the second light receiver 24 into the wavelength information associated therewith. Based on this, the transmittance of the light passing through the transmission element 23 is calculated.
[0078]
For example, as shown in FIG. 12B, among the sample values Eb (k) stored in the memory 53, the largest value in each wavelength region where the transmittance of the transmission element 23 monotonically changes. Sample values Em (i1) to Em (in) are selected as the wavelength detection target values, and correspond to the respective wavelength detection target values Em (i1) to Em (in) and the corresponding wavelength information λ (i). Each of the sample values Ea (i1) to Ea (in) (FIG. 12A) and the transmittances α and β of the branching unit 21 are used for each wavelength. The transmittance is determined as follows.
[0079]
H (i1) = (α / β) Em (i1) / Ea (i1)
H (i2) = (α / β) Em (i2) / Ea (i2)
......
H (in) = (α / β) Em (in) / Ea (in)
[0080]
The wavelength detection unit 33 calculates each sample value Ea (based on the transmittances H (i1) to H (in) calculated by the transmittance calculation unit 30 and the transmission characteristics Fa of the transmission element 23 stored in advance. The wavelengths λx (i1) to λx (in) of i1) to Ea (in) are obtained.
[0081]
However, as described above, when the etalon is used as the transmission element 23, the wavelength cannot be uniquely determined from the calculated transmittance, and thus one calculated transmittance H (ij) (j = 1) Out of a plurality of wavelengths obtained from the transmission characteristics Fa with respect to .about.n), the wavelength closest to the wavelength .lamda. (K) stored in the memory 53 in association with the wavelength detection target value Em (ij) is the wavelength. An accurate wavelength λx (ij) corresponding to the detection target value Em (ij) is selected.
[0082]
The wavelength calibrator 55 calibrates the wavelength information of the spectrum analyzer 40 based on the wavelengths λx (i1) to λx (in) obtained by the wavelength detector 33.
[0083]
The wavelength calibration may be performed in accordance with the configuration of the spectrum analyzer. Here, an example is shown in which the wavelength λ (k) of each sum value Ea (k) stored in the memory 52 is calibrated.
[0084]
That is, as described above, when light of the ITU grid used in WDM optical network communication is incident and an accurate wavelength for a plurality of intensity data is obtained, each wavelength detection target value Em (ij) And the error Δλ (ij) between the detected wavelength λx (ij) and the wavelength information stored in association with each wavelength detection target value Em (ij), respectively, and obtains the wavelength information output by the sweep control unit 21. The change characteristic Q of the error Δλ (ij) with respect to is obtained, for example, as shown in FIG.
[0085]
Then, based on the change characteristic Q, each wavelength information of the spectrum data stored in the memory 52 is subtracted and corrected.
[0086]
The spectrum waveform display means 56 reads out the spectrum data of the memory 52 whose wavelength information has been calibrated as described above, and displays the horizontal axis on the wavelength axis and the vertical axis on the orthogonal coordinate of the power axis on the screen of the display 57. And displays the waveform of the spectrum data on the rectangular coordinates.
[0087]
Since the wavelength axis of this spectrum waveform is calibrated by the wavelength calibrating means 55, the wavelength and intensity of each spectrum near the ITU grid can be accurately grasped.
[0088]
As described above, in the spectrum analyzer 40 of the embodiment, the light Pc emitted from the diffraction grating 42 at a predetermined angle with respect to the reflected light from the mirror 43 is branched into two optical paths, and one of the branched lights is divided into the first light. The light is incident on the light receiver 22, and the spectrum data of the light to be measured is obtained from the output of the light receiver 22, and the other branch light is incident on the transmission element 23 having a stable transmission characteristic Fa in which the transmittance changes with respect to the wavelength. The transmitted light is incident on the second light receiver 24, spectrum data thereof is obtained, the transmittance of light passing through the transmission element 23 is calculated from both the spectrum data, and the calculated transmittance and the transmission element 23 are calculated. The wavelength of the light that has passed through the transmission element 23 is determined based on the transmission characteristics Fa, and the wavelength of the spectrum data of the measured light is calibrated based on the determined wavelength.
[0089]
For this reason, the spectrum measurement of the measured light and the wavelength calibration can be performed in parallel with a simple configuration without using a separate light source for wavelength calibration as in the related art.
[0090]
When an etalon having a transmission characteristic Fa whose transmittance changes periodically at a predetermined wavelength interval is used as the transmission element 23, as described above, the spectrum characteristic of the light of the ITU grid used in the WDM optical network communication is used. Can be obtained with high wavelength accuracy.
[0091]
In the optical spectrum analyzer 40 of the above embodiment, the light Pc emitted from the diffraction grating 42 at a predetermined angle is split into two optical paths, one of which is received by the first light receiver 22, and the other is transmitted by the transmission element 23. The light Pc emitted from the diffraction grating 42 at a predetermined angle is split by the splitting means 21 as in a spectrum analyzer 40 'shown in FIG. ', The light Pd emitted to the first optical path is received by the first light receiver 23, and the light Pe emitted to the second optical path is incident on the first transmission element 23. The passing light Pe 'is received by the second light receiving device 24, and the light Pf emitted to the third optical path is incident on the second transmitting element 25, and the passing light Pf' is received by the third light receiving device 26. May be configured to receive light.
[0092]
In this configuration, as described above, the transmission characteristic Fb of the second transmission element 25 is different from the transmission characteristic Fa of the first transmission element 23.
[0093]
Then, similarly to the above, the output signals Ea (t), Eb (t), and Ec (t) of the respective light receivers 22, 24, and 26 when the wavelength is swept are sampled by the spectrum data obtaining means 51 '. The sample values Ea (k), Eb (k), and Ec (k) are stored in the memories 52, 53, and 54 in association with the wavelength information λ.
[0094]
Then, the first transmittance calculating means 30 calculates the transmittance H1 (ij) of the light passing through the first transmission element 23 based on the spectrum data stored in the memories 52 and 53 in the same manner as described above. Further, the second transmittance calculating means 31 calculates the transmittance H2 (ij) of the light passing through the second transmission element 25 based on the spectrum data stored in the memories 52 and 54.
[0095]
The wavelength detecting means 30 ′ obtains each transmittance H 1 from the transmittances H 1 (ij) and H 2 (ij) obtained by two sets for each wavelength and the transmission characteristics Fa and Fb of the two transmission elements 23 and 25. (Ij), an accurate wavelength λx (ij) of light determined by H2 (ij) is obtained.
[0096]
In this case, one wavelength λx (ij) can be uniquely determined from the two transmittances H1 (ij) and Hb (ij) obtained for a certain wavelength, and as described above, the sweep control means There is no need to refer to the 50 wavelength information.
[0097]
Then, based on the obtained accurate wavelength λx (ij), the wavelength is calibrated in the same manner as described above, whereby the wavelength information of the spectrum data of the measured light can be calibrated.
[0098]
Further, in the spectrum analyzers 40 and 40 'of the above-described embodiment, the wavelength information of the spectrum data stored in the memory 52 is corrected, but this does not limit the present invention. The wavelength information to be output may be calibrated, or the spectrum waveform display means 56 may correct the wavelength information of the displayed waveform.
[0099]
【The invention's effect】
As described above, the wavelength measuring method and apparatus according to the present invention allows the light to be measured to be incident on the transmission element having the transmission characteristic in which the light transmittance changes with the wavelength, and the intensity of the incident light and the light passing through the transmission element. Then, the intensity of the emitted light emitted is detected, the transmittance of the measured light to the transmission element is determined from the detected intensity of the incident light and the intensity of the emitted light, and based on the determined transmittance and the transmission characteristics of the transmission element. Thus, the wavelength of the light to be measured is obtained.
[0100]
Therefore, the wavelength of the measured light having a single wavelength can be accurately obtained without using the reference light source.
[0101]
In addition, the light to be measured is incident on the first transmission element and the second transmission element having transmission characteristics in which the light transmittance changes periodically with respect to the wavelength, and the intensity of the incident light for each transmission element is determined. The intensities of the outgoing lights emitted through the transmissive element are detected, and the transmittance of the measured light to each transmissive element is calculated from the detected intensities of the incident light and the outgoing light. When the wavelength of the light to be measured is determined based on the transmission characteristics of the element, the wavelength of the light to be measured having a single wavelength whose approximate value of the wavelength is unknown can also be accurately determined.
[0102]
Further, the optical spectrum analyzer of the present invention performs the same processing as that of the wavelength measuring device on the light emitted from the diffraction grating at a predetermined angle with respect to the reflected light from the mirror, and corrects the wavelength of the light. And the wavelength information is calibrated based on the obtained wavelength.
[0103]
Therefore, it is not necessary to separately prepare and enter light for wavelength calibration as in the related art, and it is possible to perform wavelength calibration with the light to be measured incident.
[0104]
When a transmissive element such as an etalon having a transmissivity that changes periodically with wavelength is used, the wavelength of the light of the ITU grid specified in WDM optical network communication can be accurately analyzed. can do.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a procedure of a wavelength measuring method according to the present invention.
FIG. 2 is a diagram showing a characteristic example of a transmission element.
FIG. 3 is a diagram showing an example of characteristics of a transmission element.
FIG. 4 is a diagram showing a characteristic example of a transmission element.
FIG. 5 is a flowchart showing the procedure of another wavelength measuring method according to the present invention.
FIG. 6 is a diagram showing a configuration example of an optical wavelength measurement device according to the present invention.
FIG. 7 is a diagram showing a configuration example of another optical wavelength measurement device of the present invention.
FIG. 8 is a diagram showing a configuration example of an optical spectrum analyzer according to the present invention.
FIG. 9 is a diagram showing a configuration example of a main part of an optical spectrum analyzer.
FIG. 10 is a diagram for explaining the operation of the main part of the embodiment.
FIG. 11 is a diagram illustrating an example of characteristics of a main part of the embodiment.
FIG. 12 is a diagram for explaining the operation of the main part of the embodiment.
FIG. 13 is a diagram for explaining the operation of the main part of the embodiment.
FIG. 14 is a diagram showing a configuration example of another optical spectrum analysis device according to the present invention.
FIG. 15 is a configuration diagram of a conventional device.
[Explanation of symbols]
20, 20 '... optical wavelength measuring device, 21, 21' ... branching means, 22, 24, 26 ... light receiver, 23, 25 ... transmission element, 30, 31 ... transmittance calculation means, 33 ... .., Wavelength detecting means, 40, optical spectrum analyzer, 40a, incident terminal, 41, collimating lens, 42, diffraction grating, 43, mirror, 47, driving device, 50, sweep control means, 51 .., 51 ′... Spectrum data acquisition means, 52 to 54... Memory, 55... Wavelength calibration means, 56.

Claims

(S1) A step of irradiating the light to be measured on a transmission element having a transmission characteristic whose light transmittance changes according to the wavelength, and detecting the intensity of the incident light and the intensity of the outgoing light emitted through the transmission element. )When,
Calculating a transmittance of the measured light with respect to the transmission element from the detected intensities of the incident light and the emitted light (S2);
Obtaining a wavelength of the light to be measured based on the calculated transmittance and the transmission characteristics of the transmission element (S3).

A first transmission element having a transmission characteristic in which light transmittance changes periodically with wavelength, and a first transmission element having a transmission characteristic in which light transmittance changes periodically with wavelength; A step of injecting the light to be measured into a second transmission element having a transmission characteristic different from the transmission characteristic, and detecting the intensity of the incident light and the intensity of the output light emitted through the transmission element for each transmission element. (S11),
Calculating the transmittance of the measured light with respect to each of the transmission elements from the detected incident light and the intensity of the emitted light (S12);
Obtaining a wavelength of the light to be measured based on the calculated transmittance and the transmission characteristics of each of the transmission elements (S13).

Branching means (21) for branching the light to be measured and emitting the light to a plurality of different optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A transmissive element (23) having a transmissive property in which a transmissivity to light changes depending on a wavelength, and transmitting light emitted from the branching unit to a second optical path;
A second light receiver (24) for detecting the intensity of light passing through the transmission element;
Transmittance calculating means (30) for calculating the transmittance of the light to be measured with respect to the transmission element from the intensities of the light detected by the first light receiver and the second light receiver;
An optical wavelength measuring device comprising: a wavelength detecting unit (33) for obtaining a wavelength of light to be measured based on the transmittance calculated by the transmittance calculating unit and the transmission characteristics of the transmission element.

Branching means (21) for branching the light to be measured and emitting the light to a plurality of different optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A first transmissive element (23) having a transmissive property in which a transmissivity to light periodically changes with respect to a wavelength, and transmitting light emitted from the branching unit to a second optical path;
A second light receiver (24) for detecting the intensity of light passing through the first transmission element; and a transmission characteristic having a transmittance for light that periodically changes with wavelength, and A second transmissive element (25) having a transmissive characteristic different from the transmissive characteristic and transmitting light emitted from the branching means to a third optical path;
A third light receiver that detects the intensity of light that has passed through the second transmission element, and the first light receiver based on the light intensity detected by the first light receiver and the second light receiver. First transmittance calculating means (30) for calculating the transmittance of the measured light with respect to the transmitting element;
Second transmittance calculating means (31) for calculating the transmittance of the light to be measured with respect to the second transmission element from the intensities of the light detected by the first light receiver and the third light receiver;
The wavelength of the light to be measured is determined based on the transmittance calculated by the first transmittance calculating unit and the second transmittance calculating unit and the transmission characteristics of the first transmitting element and the second transmitting element. An optical wavelength measuring device comprising a wavelength detecting means (33 ').

An input terminal (40a) for inputting light to be measured to be subjected to spectrum analysis,
A diffraction grating (42) that receives and diffracts the light to be measured incident from the incident terminal; and a mirror (43) that receives light that is diffracted by the diffraction grating with respect to the light to be measured and reflects the light to the diffraction grating. ,
The angle of the mirror with respect to the diffraction grating is changed to change the wavelength of light emitted by the diffraction grating at a predetermined emission angle with respect to the reflected light from the mirror, and outputs wavelength information corresponding to the wavelength. Wavelength sweep means (47, 50);
Branching means (21) for branching light emitted by the diffraction grating at the predetermined emission angle and emitting the light to a plurality of optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A transmissive element (23) having a transmissive property in which the transmissivity to light changes according to the wavelength, and transmitting the light emitted from the branching means to the second optical path;
A second light receiver (24) for detecting the intensity of light passing through the transmission element;
Spectrum data acquisition means (50) for storing the intensities of the light detected by the first light receiver and the second light receiver in association with the wavelength information;
Transmittance calculating means (30) for calculating the transmittance of light passing through the transmission element from the intensity of light acquired by the spectrum data acquiring means;
Wavelength detecting means (33) for obtaining the wavelength of light incident on the branching means based on the transmittance calculated by the transmittance calculating means and the transmission characteristics of the transmission element;
An optical spectrum analyzer comprising: a wavelength calibrator (55) for calibrating the wavelength information based on the wavelength detected by the wavelength detector.

An input terminal (40a) for inputting light to be measured to be subjected to spectrum analysis,
A diffraction grating (42) that receives and diffracts the light to be measured incident from the incident terminal; and a mirror (43) that receives light that is diffracted by the diffraction grating with respect to the light to be measured and reflects the light to the diffraction grating. ,
The angle of the mirror with respect to the diffraction grating is changed to change the wavelength of light emitted by the diffraction grating at a predetermined emission angle with respect to the reflected light from the mirror, and outputs wavelength information corresponding to the wavelength. Wavelength sweep means (47, 50);
Branching means (21 ') for branching the light emitted by the diffraction grating at the predetermined emission angle and emitting the light to a plurality of optical paths;
A first light receiver (22) for detecting the intensity of light emitted from the branching unit to a first optical path;
A first transmissive element (23) having a transmissive property in which a transmissivity to light periodically changes with respect to a wavelength, and transmitting light emitted from the branching unit to a second optical path;
A second light receiver (24) for detecting the intensity of light passing through the first transmission element; and a transmission characteristic having a transmittance for light that periodically changes with wavelength, and A second transmissive element (25) having a transmissive characteristic different from the transmissive characteristic, and passing light emitted from the branching means to a third optical path;
A third light receiver (26) for detecting the intensity of light passing through the second transmission element; and light intensities detected by the first light receiver, the second light receiver, and the third light receiver. Spectrum data acquisition means (50 ') for storing the spectrum data in association with the wavelength information;
First transmittance calculating means (30) for calculating the transmittance of light passing through the first transmitting element from the intensity of light acquired by the spectrum data acquiring means;
Second transmittance calculating means (31) for calculating the transmittance of light passing through the second transmitting element from the intensity of light acquired by the spectrum data acquiring means;
Based on the transmittance calculated by the first transmittance calculating unit and the second transmittance calculating unit and the transmission characteristics of the first transmitting element and the second transmitting element, the light is incident on the branching unit. Wavelength detection means (33 ') for determining the wavelength of light;
An optical spectrum analyzer comprising: a wavelength calibrator (55) for calibrating the wavelength information based on the wavelength detected by the wavelength detector.