JP4637454B2 - Polarization extinction ratio measuring device and measuring method of polarization extinction ratio usable in the measuring device - Google Patents

Description

【数１０】

により与えられる分岐出力光量Ｐ（１）とＰ（２）を用いて算出される前記ＰＥＲを、前記角度ａと角度ｂのうちのいずれか一方を一定の値にして他方を変動させ、前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τを前記ＰＭＦに与える擾乱によって変化させながら測定し、前記ＰＥＲを縦軸にとり、前記角度ａと角度ｂのうちの変動させる方の角度を前記縦軸に直交する横軸にとり、第１のＰＥＲ−角度曲線である前記ＰＥＲを測定する前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τを０にしたときのＰＥＲ−角度ａまたは角度ｂ曲線と、第２のＰＥＲ−角度曲線である前記ＰＥＲを測定する前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τをπにしたときのＰＥＲ−角度ａまたは角度ｂ曲線とを求め、前記第１のＰＥＲ−角度曲線と前記第２のＰＥＲ−角度曲線との交点から被測定物のＰＥＲを算出することを特徴としている。
【００４５】
本発明の偏光消光比等の測定装置の例は、前記角度ａがある未知の一定の値であるとき、前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて前記第１のＰＥＲ−角度曲線ならびに前記第２のＰＥＲ−角度曲線を求め、前記第１のＰＥＲ−角度曲線ならびに前記第２のＰＥＲ−角度曲線のピーク値を与える角度ｂ、および前記第１のＰＥＲ−角度曲線と前記第２のＰＥＲ−角度曲線とが交差するときの角度ｂの値から前記被測定物のＰＭＦへ入射する入射光の偏光方向と前記ＰＭＦの固有偏光軸とのなす角度を求めることを特徴としている。
【００４６】
本発明の偏光消光比等の測定装置の例は、前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて前記第１のＰＥＲ−角度曲線ならびに前記第２のＰＥＲ−角度曲線を求め、前記第１のＰＥＲ−角度曲線と前記第２のＰＥＲ−角度曲線とが交差するときの角度ｂの値から前記被測定物のＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸の回転基準方向とのなす角度を求めることを特徴としている。
【００４７】
本発明の偏光消光比等の測定装置の例は、前記角度ｂを一定の値にして前記角度ａを変動させ、前記角度ａの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させることにより変動するＰＥＲ値の最小値を測定することを特徴としている。
【００４８】
本発明の偏光消光比等の測定装置の例は、前記測定装置が、前記（数式９）と（数式１０）により与えられる分岐出力光量Ｐ（１）とＰ（２）を用いて算出される前記ＰＥＲを、前記角度ａと角度ｂのうちのいずれか一方を一定の値にして他方を変動させ、前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τを前記ＰＭＦに与える擾乱によって少なくとも０〜２πの間にわたって変化させて測定し、前記ＰＥＲを縦軸にとり、前記角度ａと角度ｂのうちの変動させる方の角度を前記縦軸に直交する横軸にとり、前記の如く測定した前記角度ａと角度ｂのうちの変動させる方の角度において少なくとも０〜２πの間にわたって変化させた前記位相差τの各値の時のＰＥＲの値の分布をグラフに表し、前記グラフにおける前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τの変化に基づくＰＥＲの変動量が最小になるとともに、前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τの変化に基づき変化するＰＥＲの値の最小値が最大になるＰＥＲの値を被測定物のＰＥＲとして求めることを特徴としている。
【００４９】
本発明の偏光消光比等の測定装置の例は、前記角度ａがある未知の一定の値であるとき、前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて測定したＰＥＲの値の分布を表す前記グラフで、前記角度ｂの各値におけるＰＥＲの値の最大値が極大になる角度ｂ、および前記角度ｂの各値におけるＰＥＲの値の最小値が最大になる角度ｂの値から前記被測定物のＰＭＦへ入射する入射光の偏光方向と前記ＰＭＦの固有偏光軸とのなす角度を求めることができることを特徴としている。
【００５０】
本発明の偏光消光比等の測定装置の例は、前記角度ａの値に関わらず前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて測定したＰＥＲの値の分布を表す前記グラフで、前記角度ｂの各値におけるＰＥＲの値の最小値が最大になる角度ｂの値から、前記被測定物のＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸の回転基準方向とのなす角度を求めることができることを特徴としている。
【００５１】
本発明の偏光消光比等の測定装置の例は、前記角度ａの値に関わらず前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて測定したＰＥＲの値の分布を表す前記グラフで、前記角度ｂの各値におけるＰＥＲの値の最小値が最大になる角度ｂの値から、前記被測定物のＰＭＦの固有偏光軸と前記ＰＭＦのコネクタのキー方向とのなす角度あるいは前記被測定物のＰＭＦの固有偏光軸と前記ＰＭＦのコネクタを取り付けるアダプタのキー溝の方向とのなす角度を求めることができることを特徴としている。
【００５２】
本発明の偏光消光比等の測定装置の例は、前記角度ｂを一定の値にして前記角度ａを変動させ、前記角度ａの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させることにより変動するＰＥＲ値の最小値を測定することを特徴としている。
【００５３】
本発明の偏光消光比等の測定装置の例は、前記擾乱付加部に、前記光ファイバの側面方向から該光ファイバに振動を与える加振手段が用いられていることを特徴としている。
【００５４】
本発明の偏光消光比等の測定装置の例は、前記光ファイバが、前記擾乱を与えられる部分の両側において所定の間隔をおいて少なくとも２カ所の固定部で固定保持されており、該光ファイバに与えられる擾乱は、該ファイバの２カ所の固定部の間の部分に該ファイバの外部から振動として与えられる擾乱であることを特徴としている。
【００５５】
本発明の偏光消光比等の測定装置の例は、前記光ファイバに与えられる擾乱が、該ファイバの２カ所の固定部の間の部分をたわませるように該ファイバの外部から振動として与えられる擾乱であることを特徴としている。
【００５６】
本発明の偏光消光比等の測定装置の例は、前記光ファイバに与えられる擾乱は、該ファイバの２カ所の固定部の間の部分に、該光ファイバの長さ方向に交差する方向に周期的に変位する加振部を当てて該ファイバの２カ所の固定部の間の部分を周期的にたわませるように該ファイバの外部から振動として与えられる擾乱であることを特徴としている。
【００５７】
本発明の偏光消光比等の測定装置の例は、前記加振部が、当該光ファイバの固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱を当該光ファイバに与える全過程において、該光ファイバの２カ所の固定部の間の部分を該光ファイバの長さ方向に交差する方向の同一方向に当該光ファイバを周期的にたわませるように該ファイバ当てられていることを特徴としている。
【００５８】
本発明の偏光消光比等の測定装置の例は、前記光ファイバを固定する２カ所の固定部の間の所定の間隔が１００ｍｍであり、２カ所の固定部の間の当該光ファイバの長さ方向に直行する方向の変位が、前記擾乱を与える全過程において、同一方向に初期値が１ｍｍ、最大値が３±１ｍｍであることを特徴としている。
【００５９】
本発明の偏光消光比等の測定装置の例は、前記光ファイバに与えられる擾乱が２Ｈｚ（ヘルツ）で変化する擾乱であることを特徴としている。
【００６０】
本発明の目的を達成するため、本発明の偏光消光比等の測定方法は、被測定物である光ファイバあるいは光ファイバを有する光デバイスにコヒーレント光を入射させ出力させたときの分岐出力光量としての、互いに直交する偏光モードの光パワーＰ（１）とＰ（２）ならびにそれらの比としてのＰＥＲ＝１０ｌｏｇ（Ｐ（１）／Ｐ（２））等を測定する偏光消光比等の測定方法であって、前記測定方法、前記光ファイバの一部に、当該光ファイバの固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱を与える擾乱付加手段を用い、前記擾乱付加手段により前記光ファイバの一部に当該光ファイバの固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱を与えたときの前記光パワーＰ（１）とＰ（２）ならびにＰＥＲを測定することができる機能を有していることを特徴としている。
【００６１】
本発明の偏光消光比等の測定方法の例は、前記測定方法は、被測定物である光ファイバあるいは光ファイバを有する光デバイスにコヒーレント光を入射しその出力光を偏光分離素子に導き、分岐出力光量として互いに直交する偏光モードの光パワーＰ（１）とＰ（２）ならびにそれらの比としてのＰＥＲ＝１０ｌｏｇ（Ｐ（１）／Ｐ（２））等を測定する偏光消光比等の測定方法であって、前記光ファイバの一部に、当該光ファイバの固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱を与え、特定のパラメータを変化させたときの前記特定のパラメータに関する前記ＰＥＲの変動量が最小になり、かつ、測定対象範囲の前記特定のパラメータの各値に対応するＰＥＲの最小値が最大になるところを求めて、前記被測定物のＰＥＲの値を求めることを特徴としている。
【００６２】
本発明の偏光消光比等の測定方法の例は、前記光ファイバの一部に、当該光ファイバの固有偏光モード間の位相差を０〜２πラディアンの間にわたって変化させるような擾乱を与える擾乱の与え方が、前記位相差がステップ状に変化するように擾乱を与える擾乱の与え方であることを特徴としており、前記擾乱を与える手段にステップモータを用いることができる。
【００６３】
本発明の偏光消光比等の測定方法の例は、前記光ファイバの一部に、当該光ファイバの固有偏光モード間の位相差を０〜２πラディアンの間にわたって変化させるような擾乱を与える擾乱の与え方が、前記位相差が連続的に変化するように擾乱を与える擾乱の与え方であることを特徴としており、前記擾乱を与える手段にモータを用いることができる。
【００６４】
本発明の偏光消光比等の測定方法の例は、前記光パワーＰ（１）が前記偏光分離素子の偏光分離軸に平行な方向に振動する偏光モードの光パワーであり、前記光パワーＰ（２）が前記偏光分離素子の偏光分離軸に直交する方向に振動する偏光モードの光パワーであることを特徴としている。
【００６５】
本発明の偏光消光比等の測定方法の例は、前記光ファイバがＰＭＦであることを特徴としている。
【００６６】
本発明の偏光消光比等の測定方法の例は、前記特定のパラメータが、被測定物である前記ＰＭＦの固有偏光軸と前記ＰＭＦに入射する入射光の偏光方向とのなす角度、ならびに、被測定物である前記ＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸とのなす角度のいずれか一方または双方であることを特徴としている。
【００６７】
本発明の偏光消光比等の測定方法の例は、前記特定のパラメータを変化させる方法が、被測定物である前記ＰＭＦの固有偏光軸と前記ＰＭＦに入射する入射光の偏光方向とのなす角度ならびに被測定物である前記ＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸とのなす角度の一方を固定して他方を変化させて測定する方法であることを特徴としている。
【００６８】
本発明の偏光消光比等の測定方法の例は、被測定物のＰＥＲを測定することができるとともに、前記ＰＭＦの固有偏光軸と前記ＰＭＦに入射する入射直線偏光の偏光方向のなす角度ならびに前記ＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸の回転基準方向とのなす角度の少なくとも一方を前記ＰＥＲの測定と同時に測定することができることを特徴としている。
【００６９】
本発明の偏光消光比等の測定方法の例は、前記測定方法が、前記（数式９）と（数式１０）により与えられる分岐出力光量Ｐ（１）とＰ（２）を用いて算出される前記ＰＥＲを、前記角度ａと角度ｂのうちのいずれか一方を一定の値にして他方を変動させ、前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τを前記ＰＭＦに与える擾乱によって変化させながら測定し、前記ＰＥＲを縦軸にとり、前記角度ａと角度ｂのうちの変動させる方の角度を前記縦軸に直交する横軸にとり、第１のＰＥＲ−角度曲線である前記ＰＥＲを測定する前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τを０にしたときのＰＥＲ−角度ａまたは角度ｂ曲線と、第２のＰＥＲ−角度曲線である前記ＰＥＲを測定する前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τをπにしたときのＰＥＲ−角度ａまたは角度ｂ曲線とを求め、前記第１のＰＥＲ−角度曲線と前記第２のＰＥＲ−角度曲線との交点から被測定物のＰＥＲを算出することを特徴としている。
【００７０】
本発明の偏光消光比等の測定方法の例は、前記角度ａがある未知の一定の値であるとき、前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて前記第１のＰＥＲ−角度曲線ならびに前記第２のＰＥＲ−角度曲線を求め、前記第１のＰＥＲ−角度曲線ならびに前記第２のＰＥＲ−角度曲線のピーク値を与える角度ｂ、および前記第１のＰＥＲ−角度曲線と前記第２のＰＥＲ−角度曲線とが交差するときの角度ｂの値から前記被測定物のＰＭＦへ入射する入射光の偏光方向と前記ＰＭＦの固有偏光軸とのなす角度を求めることを特徴としている。
【００７１】
本発明の偏光消光比等の測定方法の例は、前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて前記第１のＰＥＲ−角度曲線ならびに前記第２のＰＥＲ−角度曲線を求め、前記第１のＰＥＲ−角度曲線と前記第２のＰＥＲ−角度曲線とが交差するときの角度ｂの値から前記被測定物のＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸の回転基準方向とのなす角度を求めることを特徴としている。
【００７２】
本発明の偏光消光比等の測定方法の例は、前記角度ｂを一定の値にして前記角度ａを変動させ、前記角度ａの各値において前記光ファイバに前記擾乱を与えて前記光ファイバにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させることにより変動するＰＥＲ値の最小値を測定することを特徴としている。
【００７３】
本発明の偏光消光比等の測定方法の例は、前記測定方法が、前記（数式９）と（数式１０）により与えられる分岐出力光量Ｐ（１）とＰ（２）を用いて算出される前記ＰＥＲを、前記角度ａと角度ｂのうちのいずれか一方を一定の値にして他方を変動させ、前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τを前記ＰＭＦに与える擾乱によって少なくとも０〜２πの間にわたって変化させて測定し、前記ＰＥＲを縦軸にとり、前記角度ａと角度ｂのうちの変動させる方の角度を前記縦軸に直交する横軸にとり、前記の如く測定した前記角度ａと角度ｂのうちの変動させる方の角度において少なくとも０〜２πの間にわたって変化させた前記位相差τの各値の時のＰＥＲの値の分布をグラフに表し、前記グラフにおける前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τの変化に基づくＰＥＲの変動量が最小になるとともに、前記角度ａと角度ｂのうちの変動させる方の角度の各値における前記位相差τの変化に基づき変化するＰＥＲの値の最小値が最大になるＰＥＲの値を被測定物のＰＥＲとして求めることを特徴としている。
【００７４】
本発明の偏光消光比等の測定方法の例は、前記角度ａがある未知の一定の値であるとき、前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて測定したＰＥＲの値の分布を表す前記グラフで、前記角度ｂの各値におけるＰＥＲの値の最大値が極大になる角度ｂ、および前記角度ｂの各値におけるＰＥＲの値の最小値が最大になる角度ｂの値から前記被測定物のＰＭＦへ入射する入射光の偏光方向と前記ＰＭＦの固有偏光軸とのなす角度を求めることができることを特徴としている。
【００７５】
本発明の偏光消光比等の測定方法の例は、前記角度ａの値に関わらず前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて測定したＰＥＲの値の分布を表す前記グラフで、前記角度ｂの各値におけるＰＥＲの値の最小値が最大になる角度ｂの値から、前記被測定物のＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸の回転基準方向とのなす角度を求めることができることを特徴としている。
【００７６】
本発明の偏光消光比等の測定方法の例は、前記角度ａの値に関わらず前記角度ｂを変動させ、前記角度ｂの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させて測定したＰＥＲの値の分布を表す前記グラフで、前記角度ｂの各値におけるＰＥＲの値の最小値が最大になる角度ｂの値から、前記被測定物のＰＭＦの固有偏光軸と前記ＰＭＦのコネクタのキー方向のなす角度あるいは前記被測定物のＰＭＦの固有偏光軸と前記ＰＭＦのコネクタを取り付けるアダプタのキー溝の方向のなす角度を求めることができることを特徴としている。
【００７７】
本発明の偏光消光比等の測定方法の例は、前記角度ｂを一定の値にして前記角度ａを変動させ、前記角度ａの各値において前記ＰＭＦに前記擾乱を与えて前記ＰＭＦにおける前記位相差τを少なくとも０〜２πラディアンの間にわたって変化させることにより変動するＰＥＲ値の最小値を測定することを特徴としている。
【００７８】
【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例について説明する。なお、説明に用いる各図は本発明を理解できる程度に各構成成分の寸法、形状、配置関係などを概略的に示してある。そして、本発明の説明の都合上、部分的に拡大率を変えて図示する場合もあり、必要な部分だけを図示する場合もあり、本発明の説明に用いる図は、必ずしも実施例などの実物や記述と相似形でない場合もある。また、各図において、同様な構成成分については同一の番号を付けて示し、重複する説明を省略することもある。
【００７９】
また、本発明の測定装置に用いることができる本発明の測定方法の説明は、本発明の測定装置を説明するときにそこに用いられている例として説明する測定方法と重複するので、重複するところは本発明の測定装置の説明で測定方法の説明を兼ねることにする。
【００８０】
図１と図２は本発明の偏光消光比等の測定装置の概要を説明する図で、図１は被測定物が光ファイバで、測定用の光源としてコヒーレントプローブ光を用いた場合について、図２は被測定物がレーザダイオードにＰＭＦを取り付けたレーザダイオードモジュールの場合についてそれぞれ説明する図である。
【００８１】
図１と図２で、符号１は測定用光源としてのコヒーレントプローブ光、１１はＰＭＦ２１が取り付けられているレーザダイオードモジュール、２は被測定物の光ファイバとしてのＰＭＦ、３はＰＭＦ２またはＰＭＦ２１に擾乱を与えるための擾乱付加部としての加振器、４，５はコネクタ、６は検出部、７は偏光分離素子、８は偏光分離軸に直交する方向に振動する偏光成分の光パワー、９は偏光分離軸に平行な方向に振動する偏光成分の光パワー、１０はＰＥＲ算出部、ｘ軸はＰＭＦ２，２１の固有偏光軸、ｙ軸はＰＭＦの端面においてｘ軸に直交する軸である。
【００８２】
図示の都合で、加振器３は図ではＰＭＦ２，ＰＭＦ２１から離れているように書いてあるが、実際にはそれぞれＰＭＦ２，ＰＭＦ２１に接触するように配置されている。
【００８３】
図１あるいは図２で、コヒーレントプローブ光１またはレーザダイオードモジュール１１からＰＭＦ２またはＰＭＦ２１に入射した直線偏光は、それぞれコネクタ５から検出部６の偏光分離素子７に入射する。偏光分離素子７は、後述のように、前記ＰＭＦからの入射光の方向に平行な軸を回転の中心として回転できるようになっている。コネクタ５から検出部６の偏光分離素子７に入射した光は、偏光分離素子７によって偏光分離軸に直交する方向に振動する偏光成分の光パワー８、偏光分離軸に平行な方向に振動する偏光成分の光パワー９に分離されて検出され、その値がＰＥＲ算出部１０に入力されてＰＥＲが算出され、ＰＥＲの測定結果として検出部６から出力される。このＰＥＲ測定過程において、加振器３はそれぞれＰＭＦ２，ＰＭＦ２１に、後述するような方法で、ＰＭＦ２，ＰＭＦ２１の固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱を与え、擾乱によるＰＥＲの変化を測定する。
【００８４】
以下、さらに具体的に説明する。
【００８５】
図３は偏光モードを説明する図で、ａはそれぞれのＰＭＦに入射する直線偏光の方向と当該ＰＭＦの固有偏光軸であるｘ軸とのなす角、ｂは偏光分離素子７の偏光分離軸とｘ軸とのなす角である。
【００８６】
図４は、図１および図２で説明した加振器３を含む擾乱付加部を説明する図で、符号２２は擾乱付加部、２３は支持台、２４は被測定物としての光ファイバを固定して保持する固定具としてのファイバクランプ、２５は、本発明にしたがってＰＥＲを測定する時に被測定物としての光ファイバに局所的に応力がかかるのを防ぐとともに、光ファイバの実質的固定部として作用する支柱、２６は加振器３の一部であるテンション付与部で図示の２本の支柱２５の間に配置される被測定物である光ファイバに擾乱を与える部分、２７はストッパー、４５，４６，４７は矢印である。支持台２３は被測定物である光ファイバを安定に支持することができるものであり、内側にテンション付与部２６の加振動力源としてのモータやリニアーモーションガイド（以下、リニアーモーションをＬＭともいう）などが取り付けられている。
【００８７】
図５はテンション付与部２６を説明する図で、符号２８はＬＭガイド、２９はテンション付与プレート、３０はテンション付与プレート２９に取り付けられているバネ固定支柱Ａ、３１はモータ３３の回転板３９にモータ３３の回転中心３８から偏心して取り付けられているバネ固定支柱Ｂ、３２はバネ、３４は図４でテンション付与プレート２９の支持台２３の上に出ている部分、３５はテンション付与プレート２９の振動方向と振幅を示す矢印、３６はモータ３３の回転板３９の回転方向を示す矢印、３７はテンション付与プレート２９の端部である。
【００８８】
図６と図７はＬＭガイド２８を説明する図で、図６は平面図、図７は断面図である。図６と図７で符号４０はＬＭレールすなわちリニアーモーションレール、４１はＬＭブロックで、ＬＭブロック４１は符号４２と４３で示した部分の凸部でＬＭレールの凹部に結合してＬＭレール上を矢印４４で示した両方向へ正確にそしてスムースに移動することができるようになっている。テンション付与プレート２９はＬＭブロック４１に固定されており、ＬＭブロック４１とともに動くようになっている。
【００８９】
図５で、モータ３３の回転にしたがって、回転板３９の回転中心３８からずれた位置に設けられているバネ固定支柱Ｂの運動によって、バネ３２の伸び力が周期的に変化し、その結果、バネ固定支柱Ａが周期的に変化する引張力を受ける。バネ固定支柱Ａが取り付けられているテンション付与プレート２９は、図６，図７で説明した構造のＬＭブロック４１に取り付けられているため、バネ３２の伸縮運動によって、ＬＭガイド２８上を矢印３５の方向に振動する。
【００９０】
図８は、擾乱付加部２２に取り付けたＰＭＦに、固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱を与える方法について説明する図である。図８で符号５０は加振器のモータ３３とモータ制御回路を電気的に接続する接続線、５１は消光比測定器本体である。消光比測定器本体５１には、前記モータ制御回路、検出部６の構成要素である受光部や演算部などが配置されている。
【００９１】
図８において、次のようにして擾乱付加部２２に被測定物としての光ファイバを取り付ける。
【００９２】
まず、テンション付与部２６を図４に示した矢印４６の方向に所定量だけ移動させ、ストッパ２７の可動部分を図４に示した矢印４７の方向に出してテンション付与部２６を所定位置に止める。この状態で、レーザダイオードモジュール１１から出ているＰＭＦ２１を、まず、図で左側のファイバクランプ２４に挟んで固定し、ファイバクランプ２４からレーザダイオードモジュール１１と反対側に出ているＰＭＦを、左側の支柱２５の左側から向こう側を通って左側の支柱２５の所定位置に接しさせて右側の支柱２５に向けて、矢印４６の方向に引っ込めてあるテンション付与部２６の手前を通り、右側の支柱２５の所定位置に接しさせて右側の支柱２５の向こう側から右側を通って右側のファイバクランプ２４に導き、左側の支柱２５と右側の支柱２５の間のＰＭＦが直線状に張るように調整して、その状態で右側のファイバクランプ２４に該ＰＭＦを固定し、その先の端部に取り付けられているコネクタ５を消光比測定器本体５１のアダプタに取り付ける。この状態で矢印４６の方向に引いておいたテンション付与部２６を押さえて、ストッパ２７を矢印４７と逆の方向に引いてテンション付与部２６の押さえを解除し、テンション付与部２６を図４の矢印４５の方向へ戻して、ＰＭＦ２１の所定位置に当接させる。このとき、テンション付与部２６が加振されて振動しているときに最も矢印４６方向に引っ込んだ状態でも、テンション付与部２６に当接している部分のＰＭＦが図８で手前に所定量だけ撓むようにテンション付与部２６の初期位置を設定するのが好ましい。
【００９３】
好適な一例として、左側の支柱２５と右側の支柱２５の各中心間距離が１０ｃｍ、前記テンション付与部２６の初期位置の状態におけるＰＭＦのたわみ量が１ｍｍ、テンション付与部２６の矢印４５および４６方向の振動数が２Ｈｚ、テンション付与部２６の矢印４５および４６方向の振動による当該ＰＭＦの振幅が２±１ｍｍになるようにして、被測定物であるＰＭＦに固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって連続的にかつ周期的に変化させるような擾乱を与えて、被測定物のＰＥＲ、ＰＭＦの固有偏光軸と前記ＰＭＦに入射する入射光の偏光方向とのなす角度、ならびに、被測定物である前記ＰＭＦの固有偏光軸とコネクタのキー方向とのズレ角度を測定した。ここで、コネクタのキー方向はそれを取り付けるアダプタのキー溝方向と実質的に同じであり、いずれを測定時に使用するかは測定系の構成により適宜決めることが好ましい。
【００９４】
図９は、消光比測定器本体５１の要部を説明する図である。図９で、符号５２は検出部の主要部分、５３はたとえばＦＣタイプやＳＣタイプなどの光アダプタ、５４は偏光分離素子、５５と５６は偏光分離素子５４で分離されて出力された互いに直交する偏光モードの光パワーＰ（１）とＰ（２）とをそれぞれ検出するフォトダイオード、５７は演算回路である。
【００９５】
偏光分離素子５４とフォトダイオード５５，５６は一体化されており、偏光分離素子５４に入射した光の透過方向を軸として回転させ、ＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸のなす角度をたとえばステップ状に変化させて、各前記角度において被測定物であるＰＭＦに固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって連続的にかつ周期的に変化させるような擾乱を与えて、前記偏光分離素子の出力光を測定する。
【００９６】
図８のＰＭＦ２１に取り付けられているコネクタ５は図９の光アダプタ５３に接続される。これによって、レーザダイオードモジュール１１のレーザダイオードから出てＰＭＦ２１を伝送される光は、ＰＭＦを伝送中に、擾乱付加部２２のテンション付与部２６によるＰＭＦ２１への加振によって、該ＰＭＦの固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって連続的にかつ周期的に変化するような擾乱を付加されて、ＰＭＦのコネクタ５が取り付けられている端部から出射し、偏光分離素子５４に入射し、偏光分離素子５４で光量分岐されてそれぞれフォトダイオード５５と５６により検出され、電流波形として演算回路５７に送られ、ＰＥＲ、ＰＭＦの固有偏光軸に対する前記ＰＭＦに入射する入射光の偏光方向のズレ角度、前記ＰＭＦの固有偏光軸とコネクタのキー方向とのズレ角度などが算出される。
【００９７】
以上で本発明の偏光消光比等の測定装置の要部の構成について概略説明したが、たとえば図９の偏光分離素子からの分岐出力光量はいくつかのパラメータによって敏感に変化する。
【００９８】
そこで、以下に本発明の技術思想の主要部分について説明する。
【００９９】
特定のパラメータの１つとして、被測定物である前記ＰＭＦの固有偏光軸と前記ＰＭＦに入射する入射光の偏光方向とのなす角度を角度ａ（単位：ラディアン）とし、特定のパラメータの他の１つとして、被測定物である前記ＰＭＦの固有偏光軸と前記偏光分離素子の偏光分離軸とのなす角度を角度ｂ（単位：ラディアン）とし、被測定物である前記ＰＭＦに擾乱を与えることによって当該ＰＭＦに生じる当該ＰＭＦの固有偏光モード間の位相差をτ（単位：ラディアン）とするとき、偏光分離素子から分岐出力される互いに直交する光パワーＰ（１）とＰ（２）は、次の（数式１１）と（数式１２）で与えられる数式により与えられる。
【０１００】
【数１１】

【数１２】

そして、偏光消光比ＰＥＲは、次の（数式１３）で与えられる数式によって算出することができる。
【０１０１】
【数１３】

前記数式により与えられるＰＥＲは、前記角度ａまたは角度ｂを変えると、図１０のＰＥＲ−角度曲線６０とＰＥＲ−角度曲線６１の間で変化する。ただし、図１０では、角度ａ、角度ｂの単位をラディアンではなく度で表している。すなわち、特定パラメータとして、角度ａまたは角度ｂを横軸にとり、ＰＥＲを縦軸にとると、角度ａまたは角度ｂの各値におけるＰＥＲは、ＰＥＲ−角度曲線６０とＰＥＲ−角度曲線６１に挟まれた範囲（符号６５で示した範囲、以下、範囲６５ともいう）の値をとる。そして、ＰＥＲ−角度曲線６０とＰＥＲ−角度曲線６１に挟まれた範囲６５におけるＰＥＲの変化は、前記位相差τが０〜２πラディアンの間で変化することによって生じる。
【０１０２】
図１０で、符号６２はＰＥＲ−角度曲線６０の最大値、符号６３はＰＥＲ−角度曲線６１の最大値、符号６４はＰＥＲ−角度曲線６０とＰＥＲ−角度曲線６１の交点である。交点６４のＰＥＲ値が本発明における被測定物としてのＰＭＦのＰＥＲを与える。そして、角度ａを一定の値に固定して角度ｂを変化させたとき、すなわち、横軸を角度ｂにしたときに、最大値６２を与える角度あるいは最大値６３を与える角度と交点６４の角度の差から、入射光の偏光方向のＰＭＦの固有偏光軸に対するズレ角度αを求めることができる。さらに、交点６４を与える角度からＰＭＦの固有偏光軸とコネクタのキー方向とのズレ角度βを求めることができる。
【０１０３】
図１１〜図１８は前記数式５〜数式７に基づくシミュレーションの結果得られたグラフで、縦軸は消光比（単位：ｄＢ）、横軸は角度（単位：度）である。
【０１０４】
図１１は、角度ｂ＝０度にしたときの消光比−角度ａ特性を表し、図１２は、角度ｂ＝２．５度にしたときの消光比−角度ａ特性を表し、図１３は、角度ｂ＝５度にしたときの消光比−角度ａ特性を表し、図１４は、角度ｂ＝１０度にしたときの消光比−角度ａ特性を表し、図１５は、角度ａ＝０度にしたときの消光比−角度ｂ特性を表し、図１６は、角度ａ＝２度にしたときの消光比−角度ｂ特性を表し、図１７は、角度ａ＝５度にしたときの消光比−角度ｂ特性を表し、図１８は、角度ａ＝１０度にしたときの消光比−角度ｂ特性を表している。
【０１０５】
図１１〜図１８で、符号６０１，６０３，６０４，６０５，６０６，６１０，６１１，６１２，６１３，６２０，６２１，６２２，６２３，７００，７２０，７２１，７３０，７３１，７７０，７７１，７８０，７８１，８２０，８２１，８３０，８３１は消光比−角度特性曲線、６０２，６０７，６０８，６１４，６１５，６２４，６２５，７１０，７４０，７５０，７９０，８００，８４０，８５０は各消光比−角度特性曲線の極大値または最大値、６０９，６１６，６２６，７６０，８１０，８６０は２つの消光比−角度特性曲線の交点である。
【０１０６】
前記のように、図１１〜図１４は角度ｂを一定の値にし、角度ａをパラメータにしたときの消光比−角度特性曲線、図１５〜図１８は角度ａを一定の値にし、角度ｂをパラメータにしたときの消光比−角度特性曲線である。
【０１０７】
図１１からわかるように、角度ｂが０度のときは、ＰＥＲは位相差τの値によらず消光比−角度特性曲線７００上を変化する。このときの本発明の場合の被測定物のＰＥＲは消光比−角度特性曲線７００の最大値に一致する。そして、そのときの角度ａは０度である。
【０１０８】
図１２〜図１４は、角度ｂが０でない場合である。前記位相差τが０ラディアンのときは、ＰＥＲは図中で極大値を与える角度が正になる曲線で与えられ、前記位相差τがπラディアンのときは、ＰＥＲは図中で極大値を与える角度が負になる曲線で与えられる。前記τが０とπラディアンの間のときは、被測定物のＰＥＲは、位相差τの変化によって、それぞれ図示の２つの消光比−角度特性曲線に挟まれた範囲の値をとる。
【０１０９】
図１２において、消光比−角度特性曲線７２０と消光比−角度特性曲線７２１は数式上は同一の消光比−角度特性曲線で、交点７６０の左側の部分が消光比−角度特性曲線７２０、交点７６０の右側の部分が消光比−角度特性曲線７２１である。また、消光比−角度特性曲線７３０と消光比−角度特性曲線７３１は同一の消光比−角度特性曲線で、交点７６０の左側の部分が消光比−角度特性曲線７３０、交点７６０の右側の部分が消光比−角度特性曲線７３１である。
【０１１０】
図１２で明らかなように、交点７６０の左側では、消光比−角度特性曲線７２０が消光比−角度特性曲線の上限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線７２０より上の値をとることはなく、そして、消光比−角度特性曲線７３０が消光比−角度特性曲線の下限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線７３０より下の値をとることはない。また、交点７６０の右側では、消光比−角度特性曲線７３１が消光比−角度特性曲線の上限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線７３１より上の値をとることはなく、そして、消光比−角度特性曲線７２１が消光比−角度特性曲線の下限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線７２１より下の値をとることはない。このようなことを考慮して、交点７６０を境にして左側と右側で数式の上では異なる曲線ではあるが、位相差τの変化に基づく消光比−角度特性曲線の変化の上限に当たる消光比−角度特性曲線７２０と消光比−角度特性曲線７３１をアッパーラインともいうことにし、位相差τの変化に基づく消光比−角度特性曲線の変化の下限に当たる消光比−角度特性曲線７３０と消光比−角度特性曲線７２１をローワーラインともいうことにする。
【０１１１】
図１３において、消光比−角度特性曲線７７０と消光比−角度特性曲線７７１は数式上は同一の消光比−角度特性曲線で、交点８１０の左側の部分が消光比−角度特性曲線７７０、交点８１０の右側の部分が消光比−角度特性曲線７７１である。また、消光比−角度特性曲線７８０と消光比−角度特性曲線７８１は同一の消光比−角度特性曲線で、交点８１０の左側の部分が消光比−角度特性曲線７８０、交点８１０の右側の部分が消光比−角度特性曲線７８１である。
【０１１２】
図１４において、消光比−角度特性曲線８２０と消光比−角度特性曲線８２１は数式上は同一の消光比−角度特性曲線で、交点８６０の左側の部分が消光比−角度特性曲線８２０、交点８６０の右側の部分が消光比−角度特性曲線８２１である。また、消光比−角度特性曲線８３０と消光比−角度特性曲線８３１は同一の消光比−角度特性曲線で、交点８６０の左側の部分が消光比−角度特性曲線８３０、交点８６０の右側の部分が消光比−角度特性曲線８３１である。
【０１１３】
また、図１５からわかるように、角度ａが０度のときは、ＰＥＲは位相差τの値によらず消光比−角度特性曲線６０１上を変化する。このときの本発明の場合の被測定物のＰＥＲは消光比−角度特性曲線６０１の最大値に一致する。そして、そのときの角度ｂは０度である。
【０１１４】
図１６〜図１８は、角度ａが０でない場合である。前記位相差τが０ラディアンのときは、ＰＥＲは図中で極大値を与える角度ｂが正になる曲線で与えられ、前記位相差τがπラディアンのときは、ＰＥＲは図中で極大値を与える角度ｂが負になる曲線で与えられる。前記τが０とπラディアンの間のときは、被測定物のＰＥＲは、位相差τの変化によって、それぞれ図示の２つの消光比−角度特性曲線に挟まれた範囲の値をとる。
【０１１５】
図１６において、消光比−角度特性曲線６０３と消光比−角度特性曲線６０４は数式上は同一の消光比−角度特性曲線で、交点６０９の左側の部分が消光比−角度特性曲線６０３、交点６０９の右側の部分が消光比−角度特性曲線６０４である。また、消光比−角度特性曲線６０５と消光比−角度特性曲線６０６は同一の消光比−角度特性曲線で、交点６０９の左側の部分が消光比−角度特性曲線６０５、交点６０９の右側の部分が消光比−角度特性曲線６０６である。
【０１１６】
図１６で明らかなように、交点６０９の左側では、消光比−角度特性曲線６０３が消光比−角度特性曲線の上限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線６０３より上の値をとることはなく、そして、消光比−角度特性曲線６０５が消光比−角度特性曲線の下限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線６０５より下の値をとることはない。また、交点６０９の右側では、消光比−角度特性曲線６０６が消光比−角度特性曲線の上限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線６０６より上の値をとることはなく、そして、消光比−角度特性曲線６０４が消光比−角度特性曲線の下限となっており、位相差τがどのように変化しても、そのときの消光比−角度特性曲線が消光比−角度特性曲線６０４より下の値をとることはない。このようなことを考慮して、交点６０９を境にして左側と右側で数式の上では異なる曲線ではあるが、位相差τの変化に基づく消光比−角度特性曲線の変化の上限に当たる消光比−角度特性曲線６０３と消光比−角度特性曲線６０６をアッパーラインともいうことにし、位相差τの変化に基づく消光比−角度特性曲線の変化の下限に当たる消光比−角度特性曲線６０４と消光比−角度特性曲線６０６をローワーラインともいうことにする。
【０１１７】
図１７において、消光比−角度特性曲線６１０と消光比−角度特性曲線６１１は数式上は同一の消光比−角度特性曲線で、交点６１６の左側の部分が消光比−角度特性曲線６１０、交点６１６の右側の部分が消光比−角度特性曲線６１１である。また、消光比−角度特性曲線６１２と消光比−角度特性曲線６１３は同一の消光比−角度特性曲線で、交点６１６の左側の部分が消光比−角度特性曲線６１２、交点６１６の右側の部分が消光比−角度特性曲線６１３である。
【０１１８】
図１８において、消光比−角度特性曲線６２０と消光比−角度特性曲線６２１は数式上は同一の消光比−角度特性曲線で、交点６２６の左側の部分が消光比−角度特性曲線６２０、交点６２６の右側の部分が消光比−角度特性曲線６２１である。また、消光比−角度特性曲線６２２と消光比−角度特性曲線６２３は同一の消光比−角度特性曲線で、交点６２６の左側の部分が消光比−角度特性曲線６２２、交点６２６の右側の部分が消光比−角度特性曲線６２３である。
【０１１９】
図１２と図１６について説明したのと同様に、消光比−角度特性曲線７７０と消光比−角度特性曲線７８１、消光比−角度特性曲線８２０と消光比−角度特性曲線８３１、消光比−角度特性曲線６１０と消光比−角度特性曲線６１３、消光比−角度特性曲線６２０と消光比−角度特性曲線６２３をそれぞれアッパーラインといい、消光比−角度特性曲線７８０と消光比−角度特性曲線７７１、消光比−角度特性曲線８３０と消光比−角度特性曲線８２１、消光比−角度特性曲線６１２と消光比−角度特性曲線６１１、消光比−角度特性曲線６２２と消光比−角度特性曲線６２１をそれぞれローワーラインという。
【０１２０】
そして、図１１と図１５の場合は、前記アッパーラインとローワーラインが消光比−角度特性曲線７００あるいは消光比−角度特性曲線６０１のところで重なっているということもできる。
【０１２１】
被測定物としてのＰＭＦに加えられる擾乱によって、前記ＰＭＦの固有偏光モード間の位相差τが０〜２πの間にわたって変化したとき、測定される消光比−角度特性曲線は前記アッパーラインとローワーラインの間で変動する。
【０１２２】
アッパーラインとローワーラインについての概念は以上の説明からあきらかであるが、図１２〜図１４および図１６〜図１８で、符号６０３，６０６，６１０，６１３，６２０，６２３，７２０，７３１，７７０，７８１，８２０，８３１で示した消光比−角度特性曲線は本発明でいうアッパーラインで、符号６０４，６０５，６１１，６１２，６２１，６２２，７２１，７３０，７７１，７８０，８２１，８３０で示した消光比−角度特性曲線は本発明でいうローワーラインである。そして、符号６０１と７００で示した消光比−角度特性曲線はアッパーラインとローワーラインが一致した場合であるということができる。
【０１２３】
図１１〜図１８において、アッパーラインとローワーラインの交点のＰＥＲ値から被測定物のＰＥＲを求めることができる。
【０１２４】
図１９〜図２６は、本発明の偏光消光比等測定装置を用いてＰＥＲの偏光消光比等を測定した例を説明するグラフである。
【０１２５】
図１９は角度ｂを０度にして角度ａをパラメータとして変化させたときの消光比−角度ａ特性を示すグラフ、図２０は角度ｂを２．５度にして角度ａをパラメータとして変化させたときの消光比−角度ａ特性を示すグラフ、図２１は角度ｂを５度にして角度ａをパラメータとして変化させたときの消光比−角度ａ特性を示すグラフ、図２２は角度ｂを１０度にして角度ａをパラメータとして変化させたときの消光比−角度ａ特性を示すグラフ、図２３はＰＭＦの固有偏光軸と入射角の偏光方向の角度ズレすなわち角度ａを０度にして、後述の受光部角度をパラメータとして変化させたときの消光比−角度特性を示すグラフ、図２４は角度ａを２度にして受光部角度をパラメータとして変化させたときの消光比−角度特性を示すグラフ、図２５は角度ａを５度にして受光部角度をパラメータとして変化させたときの消光比−角度特性を示すグラフ、図２６は角度ａを１０度にして受光部角度をパラメータとして変化させたときの消光比−角度特性を示すグラフをそれぞれ表しており、縦軸は消光比（単位：ｄＢ）、横軸は図１９〜図２２の場合は角度ａ、図２３〜図２６の場合は受光部角度である。ここで、受光部角度とは、角度ｂと被測定物としてのＰＭＦの固有偏光軸と前記ＰＭＦのコネクタのキー方向あるいはそのコネクタが取り付けられるアダプタのキー溝方向とのズレ角度とを合わせた角度のことである。たとえば図８と図９で説明した場合には、消光比測定器本体５１に偏光分離素子の回転角度として受光部角度が表示されるようにすることもできる。
【０１２６】
図１９〜図２６で、符号９６，９９，１３０，１３４，１２１，１２４，１４０，１４４，５３０，５１１，１７３，１７２，１９１，１９４，５０１，５０４はそれぞれアッパーラインを表し、９８，９７，１３２，１３１，１２３，１２２，１４３，１４１，５１０，５３１，１７１，１７４，１９３，１９２，５０３，５０２はそれぞれローワーラインを表す。符号１１１，１３６，１３７，１２５，１２６，１４５，１４６，１６７，１８５，１８６，１９５，１９６，５１５，５１６はそれぞれ各アッパーラインの極大値あるいは最大値、１１２，１３５，１２７，１４７，１６８，１８７，１９７，５１７はそれぞれ各ローワーラインの最大値である。
【０１２７】
図１９〜図２６で、アッパーライン９６とアッパーライン９９はローワーラインの最大値１１２を与える角度の左側と右側の曲線であり，アッパーライン１３０とアッパーライン１３４はローワーラインの最大値１３５を与える角度の左側と右側の曲線であり，アッパーライン１２１とアッパーライン１２４はローワーラインの最大値１２７を与える角度の左側と右側の曲線であり，アッパーライン１４０とアッパーライン１４４はローワーラインの最大値１４７を与える角度の左側と右側の曲線であり，アッパーライン５３０とアッパーライン５１１はローワーラインの最大値１６８を与える角度の左側と右側の曲線であり，アッパーライン１７３とアッパーライン１７２はローワーラインの最大値１８７を与える角度の左側と右側の曲線であり，アッパーライン１９１とアッパーライン１９４はローワーラインの最大値１９７を与える角度の左側と右側の曲線であり，アッパーライン５０１とアッパーライン５０４はローワーラインの最大値５１７を与える角度の左側と右側の曲線である。また、ローワーライン９８とローワーライン９７はローワーラインの最大値１１２を与える角度の左側と右側の曲線であり，ローワーライン１３２とローワーライン１３１はローワーラインの最大値１３５を与える角度の左側と右側の曲線であり，ローワーライン１２３とローワーライン１２２はローワーラインの最大値１２７を与える角度の左側と右側の曲線であり，ローワーライン１４３とローワーライン１４１はローワーラインの最大値１４７を与える角度の左側と右側の曲線であり，ローワーライン５１０とローワーライン５３１はローワーラインの最大値１６８を与える角度の左側と右側の曲線であり，ローワーライン１７１とローワーライン１７４はローワーラインの最大値１８７を与える角度の左側と右側の曲線であり，ローワーライン１９３とローワーライン１９２はローワーラインの最大値１９７を与える角度の左側と右側の曲線であり，ローワーライン５０３とローワーライン５０２はローワーラインの最大値５１７を与える角度の左側と右側の曲線である。
【０１２８】
図１９〜図２６のデータは、横軸の角度の各１つの測定点において、被測定ＰＭＦに、図４〜図８を用いて説明したような、被測定ＰＭＦの固有偏光モード間の位相差を少なくとも０〜２πラディアンの間にわたって変化させるような擾乱（たとえば、振動数２Ｈｚの連続的な擾乱）を与え、そのときの消光比を測定して、各測定点の角度において得られた消光比の最大値を図のアッパーラインとして、最小値をローワーラインとしてそれぞれ記録する方法で行った。
【０１２９】
図１９で符号１０１〜１１０で示した点、図２３で符号１５５〜１６４で示した点、図２４で符号１７５〜１８４で示した点、図２６で符号５０５〜５１４で示した点は各データの取り方を説明するための測定点の例を示すもので、奇数番の点はアッパーライン上の点、偶数番の点はローワーライン上の点である。そして、図１９で、点１０１と１０２，１０３と１０４，１０５と１０６，１０７と１０８，１０９と１１０はそれぞれ角度ａが同じ値のときのもので、それぞれ角度ａが０．５度ずつ変わっている。また、図２３で、点１５５と１５６，１５７と１５８，１５９と１６０，１６１と１６２，１６３と１６４、図２４で、点１７５と１７６，１７７と１７８，１７９と１８０，１８１と１８２，１８３と１８４、図２６で、点５０５と５０６，５０７と５０８，５０９と５１０，５１１と５１２，５１３と５１４はそれぞれ受光部角度が同じ値のときのもので、受光部角度が１度ずつ変わっている。
【０１３０】
図１９を例にとって説明すると、角度ａを０．５度ずつ変化させＰＥＲを測定するが、その測定の過程で、各測定点で角度ａの変化を止めて、被測定ＰＥＲにその固有偏光モード間の位相差τが０〜２πの間にわたって変化するような擾乱をかけながらＰＥＲを測定した。たとえば、点１０１と１０２のところの角度ａで角度ａの変化を所定時間止めて、図４〜図８を用いて説明したようにモータを連続的に回転させて被測定物のＰＭＦに擾乱を与えながらＰＥＲの最大値と最小値を求め、その後角度ａを０．５度変化させて点１０３と１０４のところの角度ａで角度ａの変化を再び所定時間止めて、図４〜図８を用いて説明したようにモータを連続的に回転させて前記ＰＭＦに擾乱を与えながらＰＥＲの最大値と最小値を求め、その後さらに角度ａを０．５度変化させて点１０５と１０６のところの角度ａで角度ａの変化を再び所定時間止めて、前記擾乱を与えながらＰＥＲの最大値と最小値を求め、同様に点１０７と１０８のところの角度ａで測定し、次に点１０９と１１０のところの角度ａで測定し、以下同様に測定を続けて図１９のデータを得た。
【０１３１】
図１９で、点１０１と１０２のところの角度ａで角度ａの変化を所定時間止めて、図４〜図８を用いて説明したようにモータを連続的に回転させて被測定物のＰＭＦに擾乱を与えながら被測定物のＰＥＲの測定を行う場合、該測定の初期状態で該ＰＭＦの固有偏光モード間の位相差τがどのような値になっているかわからないとき、測定されるＰＥＲは点１０１と１０２ところのＰＥＲの値の間の値になる。そして、該ＰＭＦの固有偏光モード間の位相差τが０〜２πの間にわたって変化するように該ＰＭＦに擾乱を連続して与え続けながらＰＥＲを測定すると、測定されたＰＥＲの値は点１０１のところの値と点１０２のところの値の間の値を示し、最大値として点１０１のところのＰＥＲが確実に求まり、最小値として点１０２のところのＰＥＲが確実に求まる。前記図２３，図２４，図２６の各測定点の場合も同様である。
【０１３２】
図２３の点１６３と点１６４のＰＥＲの差、その他各測定点のＰＥＲの最大−最小値の差、図２４の点１７９と点１８０のＰＥＲの差、その他各測定点のＰＥＲの最大−最小値の差、図２６の点５１３と点５１４のＰＥＲの差、その他各測定点のＰＥＲの最大−最小値の差から明らかなように、測定の条件によって各測定点でのＰＥＲの最大−最小値の差に大きな違いがある。
【０１３３】
図１９〜図２２のデータで、各ローワーラインの最大値がほぼ角度ａ＝０度のところにあるが、各ローワーラインの最大値が角度ａ＝０．０度に厳密に一致しないのは、測定上の誤差によるものである。また、図２０〜図２２の各図で、アッパーラインの各極大値とローワーラインの最大値の差は角固定した角度ｂの値に一致している。
【０１３４】
図２３〜図２６のデータでは各ローワーラインの最大値を与える受光部角度の値が０度からずれているが、このずれ量から該ＰＭＦの固有偏光軸と該ＰＭＦのコネクタのキー方向あるいはそのコネクタを取り付ける測定器本体のアダプタのキー溝の方向のズレ角度を求めることができる。さらに、ローワーラインの最大値を与える受光部角度とアッパーラインの極大値を与える受光部角度との差より該ＰＭＦの固有偏光軸と偏光分離素子の偏光分離軸のズレ角αを求めることができることがわかる。
【０１３５】
すなわち、図１９〜図２６のデータにおいて、ローワーラインの最大値から被測定物のＰＭＦの正しいＰＥＲを求めることができるとともに、同じデータを用いて、ＰＭＦに取り付けられているコネクタのキー方向が該ＰＭＦの偏光固有軸からずれている量や、入射偏光の方向が該ＰＭＦの偏光固有軸からずれている量などを求めることができる。
【０１３６】
図２７と図２８はＰＭＦに取り付けられているコネクタのキー方向について説明する図である。符号９０５はＰＭＦ２１に取り付けられているコネクタ５のキー、９０１はコネクタ５が装着される本発明の消光比測定器本体５１のアダプタ５３に設けられているキー溝である。コネクタ５はキー９０５がキー溝９０１に入るようにアダプタ５３に取り付けられ、これによって、コネクタ５のキー方向とアダプタ５３のキー溝方向との位置関係が保たれる。
【０１３７】
また、偏光分離素子の回転基準方向は偏光分離素子を回転させて入射光を測定するときの基準となる方向であり、たとえば、光アダプタのキー溝の方向にとることもできる。なお、コネクタおよびアダプタにキーとキー溝のいずれか一方だけをつけてもよく、そしてその付け方を前記とは逆に、コネクタにキー溝をアダプタにキーをつけてもよく、また、それぞれにキーとキー溝の双方をつけることも可能であり、いずれの場合も本発明が多大な効果を発揮することは以上の説明から明らかである。
【０１３８】
以上、本発明の実施の形態例を説明したが、本発明は前記実施の形態例に狭く限定されるものではなく、本発明の技術思想を活用して、多くのバリエーションを可能とするものである。
【０１３９】
たとえば、被測定物としての光ファイバに与える擾乱を連続ではなくステップモータを用いて段階的に変化させたり、擾乱に変調信号を重畳させたり、測定制御系をコンピュータ制御したりするなど、多くのバリエーションが可能である。
【０１４０】
【発明の効果】
以上説明したように、本発明によれば、ＰＭＦのように諸種の物理的条件でＰＥＲが変化してしまう場合には従来全くできなかった正確なＰＥＲの測定が正確にしかも極めて容易にできるのみならず、入射光と被測定物のＰＭＦの固有偏光軸のずれ角、被測定物のＰＭＦの固有偏光軸と偏光分離素子の偏光分離軸のなす角度、被測定物のＰＭＦの固有偏光軸とそれに取り付けられているコネクタのキー方向のズレ角などを測定することができる。
【０１４１】
さらに光源としての制約も大幅に緩和することができる。
【０１４２】
本発明を、たとえば、ＰＭＦを取り付けたレーザダイオードモジュールの製造工程に適用することにより、従来は合格品を不合格品に判定したり、不合格品を合格品に判定したりしていた検査工程の信頼性を極めて高いものにすることができるとともに、製品の品質を各段に高めることができ、製造コストを大幅に低減することができる。
【０１４３】
以上のように、本発明は工業上多大な効果を発揮するものである。
【図面の簡単な説明】
【図１】 本発明の偏光消光比等の測定装置の概要を説明する図である。
【図２】 本発明の偏光消光比等の測定装置の概要を説明する図である。
【図３】 偏光モードを説明する図である。
【図４】 本発明の擾乱付加部の例を説明する図である。
【図５】 本発明のテンション付与部の例を説明する図である
【図６】 本発明のテンション付与部に用いるリニアーモーションガイドの例の平面図である。
【図７】 本発明のテンション付与部に用いるリニアーモーションガイドの例の断面図である。
【図８】 本発明の擾乱付加部の例を説明する図である。
【図９】 本発明の消光比測定器本体の例を説明する図である。
【図１０】 本発明の測定方法におけるＰＥＲの角度依存特性ついて説明する図である。
【図１１】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１２】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１３】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１４】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１５】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１６】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１７】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１８】 本発明の測定方法によるＰＥＲ−角度依存特性の例である。
【図１９】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２０】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２１】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２２】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２３】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２４】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２５】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２６】 本発明の測定方法によるＰＥＲ等の測定例である。
【図２７】 コネクタのキー方向を説明する図である。
【図２８】 コネクタのキー方向を説明する図である。
【図２９】 従来の典型的なＰＥＲ測定方法を説明する図である。
【図３０】 従来の典型的なＰＥＲ測定方法の改良として提案された従来のＰＥＲ測定装置を説明する図である。
【図３１】 従来の典型的なＰＥＲ測定方法の改良として提案された従来のＰＥＲ測定装置を説明する図である。
【図３２】 従来の典型的なＰＥＲ測定方法の改良として提案された従来のＰＥＲ測定装置を説明する図である。
【図３３】 従来の典型的なＰＥＲ測定方法の改良として提案された従来のＰＥＲ測定装置を説明する図である。
【符号の説明】
１：コヒーレントプローブ光、
２，２１，２０３：ＰＭＦ、
３：加振器
４，５：コネクタ
６：検出部
７：偏光分離素子
８：偏光分離軸に直交する方向に振動する偏光成分の出力光パワー
９：偏光分離軸に平行な方向に振動する偏光成分の出力光パワー
１０：ＰＥＲ算出部
１１：レーザダイオードモジュール
２２：擾乱付加部
２３：支持台
２４：ファイバクランプ
２５：支柱
２６：テンション付与部
２７：ストッパー
２８：ＬＭガイド
２９：テンション付与プレート
３０，３１：バネ固定支柱
３２：バネ
３３：モータ
３４：図４でテンション付与プレート２９の支持台２３の上に出ている部分
３５，３６，４４，４５，４６，４７，２０６，２０７，３５２矢印
３７：端部
３８：回転中心３８
３９：回転板
４０：リニアーモーション（ＬＭ）レール
４１：ＬＭブロック
４２，４３：凸部
５０：接続線
５１：消光比測定器本体
５２：検出部の主要部分
５３：光アダプタ
５４：偏光分離素子
５５，５６：フォトダイオード
５７：演算回路
６０，６１：ＰＥＲ−角度曲線
６２，６３：最大値
６４：交点
９６，９９，１３０，１３４，１２１，１２４，１４０，１４４，５３０，５１１，１７３，１７２，１９１，１９４，５０１，５０４，６０３，６０６，６１０，６１３，６２０，６２３，７２０，７３１，７７０，７８１，８２０，８３１：アッパーライン
９８，９７，１３２，１３１，１２３，１２２，１４３，１４１，５１０，５３１，１７１，１７４，１９３，１９２，５０３，５０２，６０４，６０５，６１１，６１２，６２１，６２２，７２１，７３０，７７１，７８０，８２１，８３０：ローワーライン
１１１，１３６，１３７，１２５，１２６，１４５，１４６，１６７，１８５，１８６，１９５，１９６，５１５，５１６，６０７，６０８，６１４，６１５，６２４，６２５，７４０，７５０，７９０，８００，８４０，８５０：アッパーラインの極大値
１１２，１３５，１２７，１４７，１６８，１８７，１９７，５１７：各ローワーラインの最大値
２０１：光源
２０２：偏光子
２０４：検光子
２０５：受光器
３０１：アルミニウム保持板
３２５：可動光ファイバ把持部
３２６：固定光ファイバ把持部
３０２：クランプ部材
３０３：弾性部材
３０４：ベース
３０５：ストッパ
３０６：スライドガイド
３２１：断面矩形の溝
３０７：光ファイバコネクタハーネス品
３０９：光コネクタ
３１０：検出器
３５１：可動光ファイバ把持部摺動制止部
６０１，７００：消光比−角度特性曲線
６０２，７１０：消光比−角度特性曲線の最大値
６０９，６１６，６２６，７６０，８１０，８６０：２つの消光比−角度特性曲線の交点
９０１：アダプタのー溝
９０５：コネクタのキー
ａ，ｂ：角度
ｘ軸：固有偏光軸
ｙ軸：ｘ軸に直交する軸[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a novel measuring apparatus such as a polarization extinction ratio of an optical fiber (hereinafter also simply referred to as a fiber) or an optical device having an optical fiber, and a polarization extinction ratio measuring method that can be used for the measuring apparatus, Specifically, the polarization extinction ratio representing the transmission characteristics of an optical fiber or an optical device having an optical fiber, and the polarization direction of incident light incident on the optical fiberAnd PPolarization extinction ratio of an optical fiber or an optical device having an optical fiber that can simultaneously know the angle between the MF's intrinsic polarization axis, the intrinsic polarization axis of the optical fiber and the polarization separation axis of the polarization separation element, etc. The present invention relates to a novel measuring apparatus and a measuring method such as polarization extinction ratio that can be used in the measuring apparatus.
[0002]
In the present invention, the polarized light is sometimes referred to as polarized light.
[0003]
The polarization extinction-on ratio (hereinafter, also referred to as PER) in the present invention is, for example, an optical fiber that is an object to be measured or an optical device having an optical fiber. 10 log (P (1) / P (2)) (dB), which is the ratio between the optical powers P (1) and P (2) of polarization modes orthogonal to each other, as the branched output light quantity when entering and outputting. That means.
[0004]
The 10 log (P (1) / P (2)) (dB) is an expression usually used in mathematical formulas and means 10 × log (P (1) / P (2)) (dB).
[0005]
In addition, PER may be defined with an opposite sign. In this case, the expression “large” in the former must be expressed as “small” in the latter. In the present invention, the same expression as the former expression is used.
[0006]
In the following, the polarization extinction ratio is also simply referred to as the extinction ratio.
[0007]
[Prior art]
As is well known, a polarization-maintaining fiber having two linear polarization modes with different propagation constants (also referred to as a polarization-maintaining fiber; Polarization Main-Aining Optical Fiber, hereinafter also referred to as PMF) is used between the two polarization modes. Ideally, it does not cause coupling of transmitted light, but in addition to the performance limit of the optical fiber itself, the polarization preserving property is reduced, that is, deteriorated due to the stress applied to the optical fiber at the connector and other physical causes. Some optical mode coupling occurs between the two polarization modes.
[0008]
The polarization preserving characteristics of the PMF and the optical device can be expressed by PER. PER is an important parameter when single polarization transmission or polarization multiplexing transmission is required in an optical communication or measurement system. For example, a modulator made of LiNbO3 operates with only linear polarization input. In addition, the polarization preserving property of the optical fiber is important in the polarization synthesis of the light source for the purpose of improving the reliability of the optical submarine communication system, the polarization synthesis of the pump light of the Raman amplification, and the like.
[0009]
In general, when linearly polarized light is incident on an eigenpolarization mode (hereinafter also referred to as PSP) of a PMF or a polarization device, PER changes in a direction worse than an ideal value due to mode conversion in the PMF, that is, deteriorates. In addition, when a connector is attached to the PMF, the PER deteriorates if there is non-uniform stress that acts on the PMF at the connector portion. Alternatively, when a laser module is manufactured by coupling PMF to a semiconductor laser, if the polarization plane of the laser does not match the intrinsic polarization plane of the PMF, the PER of the output light deteriorates. Furthermore, when a connector is attached to such a laser module with PMF, PER deteriorates further due to the above-described causes.
[0010]
In many cases, the PMF connector is provided with a polarization keyway for the purpose of connection with matching the specific polarization axis. However, the orientation does not always coincide with the PSP due to a manufacturing problem. The amount of deviation of the polarization direction of the key groove of this connector from the PSP is an important parameter for realizing a single polarization operation.
[0011]
A typical conventional method for measuring PER is to detect and measure where the optical power ratio between two orthogonal polarizations is maximized by rotating at least one of the polarizer and analyzer of the measurement system. It was.
[0012]
FIG. 29 is a diagram for explaining a conventional typical PER measurement method. For example, in the case of PMF, as shown in FIG. 29, a polarizer 202 is disposed between the light source 201 and the measured PMF 203, an analyzer 204 is disposed between the measured PMF 203 and the light receiver 205, and the polarizer 202 is disposed. For example, as shown by an arrow 206, the probe light from the light source 201 is rotated in the plane perpendicular to the paper surface of the drawing so that the linear polarization mode of the probe light from the light source 201 matches the PSP of the PMF 203. And the analyzer 204 is rotated from the far side to the near side in a plane perpendicular to the paper surface of the drawing as indicated by an arrow 207, for example, to detect the point where the output from the light receiver 205 is maximized. In this way, while observing the detection result by the light receiver 205, the polarizer 202 and the analyzer 204 are rotated to determine the PSP of the measured PMF 203, and the PER in that case is obtained.
[0013]
This type of PER measurement apparatus is premised on the incidence of linearly polarized light on the PMF PSP that is the object to be measured. Furthermore, a low coherence light source is desired for the probe light. However, in the case of a laser module with a fiber that is a finished product, the PER must be obtained so that the ratio of the optical power of the orthogonal polarization direction is maximized by rotating the analyzer only on the light receiving side, Due to the high coherence of the light source, the PER of the connector itself has deteriorated, or the polarization orientations of the laser and the PMF have shifted, making it impossible to measure PER with accurate reproducibility.
[0014]
As a method for solving such a problem, a PER measuring apparatus such as “JP 2000-97806” has been proposed.
[0015]
30 to 33 are diagrams for explaining the PER measuring apparatus proposed in Japanese Patent Laid-Open No. 2000-97806.
[0016]
FIG. 30 shows two lights, a movable optical fiber gripping part 325 that can move its position while holding the optical fiber and a fixed optical fiber gripping part 326 that cannot move its position while holding the optical fiber. The figure shows an optical fiber fixing jig provided with a fiber gripping part. Reference numeral 301 is a fiber holding plate made of aluminum, 302 is a clamp member made of synthetic resin, 303 is an elastic member, 304 is a base made of aluminum, and 305 is a synthetic material. A stopper 306 made of resin is a slide guide. The clamp member 302 of the movable optical fiber gripping portion 325 is mounted so that the fiber holding plate 301 can be opened and closed. The clamp member 302 and the fiber holding plate 301 constitute the movable optical fiber gripping portion 325.
[0017]
In FIG. 30, a fiber holding plate 301 is formed with a groove 321 having a rectangular cross section having a width for holding an optical fiber. When the outer diameter of the optical fiber attached to the groove 321 is 0.4 mm, the width of the groove 321 is formed to be 0.45 + 0 to 0.05 mm. The groove 321 can be similarly formed on the clamp member 302 side.
[0018]
The elastic member 303 is formed of a torsion coil spring of piano wire. The fiber holding plate 301 is denoted by reference numeral 251 by the force of the elastic member 303 made of a torsion coil spring of a piano wire when the stopper 305 is in a position where the restraint of the fiber holding plate 301 is released as will be described later. A part is arranged along the slide guide 306.
[0019]
As shown in FIG. 31, the torsion coil spring made of a piano wire has a very wide characteristic in a region where the relationship between displacement and load is flat, and by adopting this, it does not depend on the gripping position of the optical fiber. A constant tension can be secured.
[0020]
The movable optical fiber gripping part 325 can be moved along the slide guide 306 by the spring force of the elastic member 303 as will be described later.
[0021]
FIGS. 32 and 33 are diagrams for explaining a method of measuring the PER of the object to be measured by attaching the PMF as the object to be measured to the optical fiber fixing jig described in FIG. 30. Reference numeral 307 denotes the PMF as a connector. The attached optical fiber connector harness product, 309 is an optical connector, and 310 is a detector.
[0022]
32 and 33 show the PMF of the optical fiber connector harness product 307 with the movable optical fiber gripping portion 325 and the fixed optical fiber gripping such that the direction of the natural polarization mode axis of the PMF is parallel to the bottom surface of the groove 321. FIG. 32 shows a state in which the movable optical fiber gripping portion sliding restraining portion 351 of the stopper 305 is in a position to stop the sliding of the movable optical fiber gripping portion. 33, the stopper 305 is rotated in the direction of the arrow 352 in FIG. 32, and the movable optical fiber gripper sliding restraining part 351 of the stopper 305 is in a position enabling the movable optical fiber gripper to slide. It shows the state.
[0023]
The linearly polarized light for measurement is incident on the PMF from the end of the optical fiber connector harness 307 opposite to the optical connector 309, and the output light from the end of the PMF on the optical connector 309 side is input to the detector 310. The PER of the guiding optical fiber connector harness product 307 is measured. As shown in FIG. 32, the sliding of the movable optical fiber gripping portion 325 is stopped by the stopper 305 and no tension is applied to the optical fiber. Thus, the stopper 305 is released to enable the movable optical fiber gripping portion 325 to slide, and the movable optical fiber gripping portion 325 is caused to slide by the force of the elastic member 303 formed of a torsion coil spring of a piano wire. The PER is measured in each case where a constant tension is applied to the fiber without disturbing its crosstalk.
[0024]
In this way, the PER is measured in a state in which the tension applied to the optical fiber as the object to be measured becomes two different values as in the case of FIG. 32 and FIG. 33, and the PER and the difference between them are specified. The pass / fail of the object to be measured is determined by comparing with each reference value set as. For example, the difference between the two PERs is determined to be acceptable when the difference is less than 3 dB set as the reference value, and is rejected when a difference of 3 dB or more is generated.
[0025]
[Problems to be solved by the invention]
As described above, in the conventional typical PMF PER measuring method and measuring apparatus, it is assumed that linearly polarized light is incident on the PSF of the PMF to be measured. It is desired to be a coherent light source. However, there is a problem that there is no light source depending on the wavelength range, and furthermore, it has not been able to cope with the change in PER under various physical conditions like PMF.
[0026]
In the measuring method described in Japanese Patent Laid-Open No. 2000-97806 proposed to solve this, a constant tension is applied in the length direction of the optical fiber, and the values of two PERs depending on the presence or absence of the tension are measured. Therefore, it is described that the pass / fail of the PMF connector harness product can be determined without obtaining a highly accurate and accurate PER.
[0027]
  However, as a result of the study of the inventors of the present invention, the method isInHowever, depending on how the tension is applied to the optical fiber, it may be determined that the product is rejected even if it is rejected, and it is impossible to increase the yield of the product except for accidental results. close.
[0028]
Furthermore, in the conventional PER measurement method, not only the correct PER cannot be known, but also the angle between the intrinsic polarization axis of the PMF that is the object to be measured and the polarization direction of the incident light incident on the PMF, and the object to be measured The angle between the intrinsic polarization axis of the PMF and the direction of the key groove of the connector cannot be known. Knowing the angles is extremely important, for example, in order to provide a high-quality light source for a microscope and to realize high reliability in optical communication at low cost.
[0029]
The polarization preserving characteristics of the PMF and the optical device can be expressed by PER. PER is an important parameter when single polarization transmission or polarization multiplexing transmission is required in an optical communication or measurement system. For example, a modulator made of LiNbO3 operates with only linear polarization input. In addition, the polarization preserving property of the optical fiber is important in the polarization synthesis of the light source for the purpose of improving the reliability of the optical submarine communication system, the polarization synthesis of the pump light of the Raman amplification, and the like.
[0030]
  The present invention has been made in view of the above points, and an object of the present invention is to solve the above-described problems andOptical fiberAs well as measuring the PER, the angle between the intrinsic polarization axis of the PMF that is the object to be measured and the polarization direction of the incident light incident on the PMF, and the PMF that is the object to be measured It is an object of the present invention to provide a measuring apparatus and a measuring method capable of measuring an angle formed between an intrinsic polarization axis and a key groove direction of a connector.
Various factors such as the amount of deviation of the polarization key groove of the connector of the optical fiber to be measured from the PSP and the tension on the fiber can be measured separately, and can also be measured on a completed fiber. It is to provide a PER measuring device.
[0031]
[Means for Solving the Problems]
The present invention has been made to achieve the above object.
[0032]
Although the present invention has some remarkable features, the greatest feature of the present invention is that the branching when coherent light is incident on and output from an optical fiber or an optical device having an optical fiber to be measured. Novel polarization quenching that measures optical power P (1) and P (2) of polarization modes orthogonal to each other as output light quantity and PER = 10 log (P (1) / P (2)) as a ratio thereof In a measuring apparatus such as a ratio or a measuring method that can be used for the measuring apparatus, the measuring apparatus or the measuring method has a phase difference between the intrinsic polarization modes of the optical fiber at least 0 to 2π in a part of the optical fiber. Disturbance adding means for applying a disturbance that can be changed between radians is used, and the disturbance adding means applies the disturbance to a part of the optical fiber. The optical powers P (1) and P (2) and PER are measured very accurately when the disturbance is such that the phase difference between the intrinsic polarization modes of the fiber can vary between at least 0 and 2π radians. It is to be able to do. In addition to accurate PER measurement, the angle between the polarization direction of the PMF that is the object to be measured and the polarization direction of the incident light that is incident on the PMF, and the inherent polarization axis of the PMF that is the object to be measured And a novel measuring apparatus and measuring method that can know the angle formed by the key direction of the optical connector attached to the PMF is provided in a small and low-cost manner.
[0033]
  Hereinafter, various examples of the present invention will be described.As is apparent from the description of each claim in the specification of the present invention at the time of filing, the example of the present invention may have one of the various features described above and below alone, May have some of the characteristics.
[0034]
In order to achieve the object of the present invention, the polarization extinction ratio measuring apparatus according to the present invention has a branched output light amount when coherent light is incident on and output from an optical fiber as an object to be measured or an optical device having an optical fiber. Polarization extinction ratio measuring device for measuring optical powers P (1) and P (2) of orthogonal polarization modes as PER and PER = 10 log (P (1) / P (2)) as a ratio thereof The measurement apparatus has at least a disturbance adding unit and a detecting unit, and the disturbance adding unit sets a phase difference between the intrinsic polarization modes of the optical fiber to at least 0 to 2π in a part of the optical fiber. The detector has a function capable of giving a disturbance that varies between radians, and the detector adds the intrinsic polarization of the optical fiber to a part of the optical fiber by the disturbance adding unit. A function capable of measuring the optical powers P (1) and P (2) and PER when a disturbance is applied to change the phase difference between the nodes at least between 0 and 2π radians. It is characterized by being.
[0035]
An example of a measuring apparatus for the polarization extinction ratio, etc. of the present invention is the measuring apparatus for the polarization extinction ratio, etc., wherein the detection unit has a polarization separation element and an optical fiber or an optical fiber that is the object to be measured. The output light that is output by making the coherent light incident on the optical device having the optical device is guided to the polarization separation element, and the disturbance adding unit causes a part of the optical fiber to pass between the intrinsic polarization modes of the optical fiber. The phase difference of at least 0 to 2π radians is applied, the amount of change in the PER with respect to the specific parameter when the specific parameter is changed is minimized, and Measurement that can determine the PER value of the object to be measured by finding where the minimum value of PER corresponding to each value of the specific parameter is maximized It is characterized in that it is a location.
[0036]
An example of a measuring apparatus such as a polarization extinction ratio according to the present invention is a disturbance in which a part of the optical fiber is subjected to a disturbance that changes a phase difference between intrinsic polarization modes of the optical fiber over at least 0 to 2π radians. Is a method of giving a disturbance such that the phase difference changes stepwise, and a stepping motor can be used as the means for giving the disturbance.
[0037]
An example of a measurement apparatus for the polarization extinction ratio of the present invention is a disturbance that can change a phase difference between intrinsic polarization modes of the optical fiber over at least 0 to 2π radians in a part of the optical fiber. The method of giving the disturbance is a method of giving the disturbance so that the phase difference continuously changes, and a motor can be used as the means for giving the disturbance.
[0038]
An example of a measuring apparatus for the polarization extinction ratio and the like of the present invention is an optical power of a polarization mode in which the optical power P (1) vibrates in a direction parallel to the polarization separation axis of the polarization separation element, and the optical power P ( 2) is the optical power of a polarization mode that vibrates in a direction perpendicular to the polarization separation axis of the polarization separation element.
[0039]
The example of the measuring apparatus for the polarization extinction ratio of the present invention is characterized in that the optical fiber is PMF.
[0040]
In the example of the measuring apparatus such as the polarization extinction ratio of the present invention, the specific parameter includes an angle formed between the specific polarization axis of the PMF as a measurement object and the polarization direction of incident light incident on the PMF, and It is one or both of the angles formed between the intrinsic polarization axis of the PMF as a measurement object and the polarization separation axis of the polarization separation element.
[0041]
An example of a measuring device such as a polarization extinction ratio according to the present invention is an angle formed by the device that changes the specific parameter between the intrinsic polarization axis of the PMF as a measurement object and the polarization direction of incident light incident on the PMF. In addition, the apparatus is characterized in that the PER is measured by fixing one of the angles formed by the intrinsic polarization axis of the PMF as the object to be measured and the polarization separation axis of the polarization separation element and changing the other.
[0042]
The example of the measuring apparatus such as the polarization extinction ratio of the present invention can measure the PER of the object to be measured, and can change the polarization direction of the incident linearly polarized light incident on the PMF and the intrinsic polarization axis of the PMF of the object to be measured. It is characterized in that at least one of the angle formed and the angle formed between the intrinsic polarization axis of the PMF and the rotation reference direction of the polarization separation axis of the polarization separation element can be measured simultaneously with the measurement of the PER.
[0043]
An example of a measuring device such as a polarization extinction ratio according to the present invention is that the measuring device is one of the specific parameters, the polarization axis of the incident light incident on the PMF and the intrinsic polarization axis of the PMF as the object to be measured. The angle formed by the direction is defined as an angle a (unit: radians), and the angle formed by the intrinsic polarization axis of the PMF as the object to be measured and the polarization separation axis of the polarization separation element as one of the specific parameters. When the angle b (unit: radians) is used, and the phase difference between eigenpolarization modes of the PMF generated in the PMF by giving a disturbance to the PMF that is the object to be measured is τ (unit: radians), 9) and (Formula 10)
[0044]
[Equation 9]

[Expression 10]

The PER calculated by using the branch output light amounts P (1) and P (2) given by the equation (1) is changed by setting one of the angle a and the angle b to a constant value and changing the other. Measure while changing the phase difference τ at each of the values of the angle a and angle b to be changed by the disturbance applied to the PMF, take the PER as the vertical axis, and change between the angle a and the angle b The phase difference in each value of the angle a and the angle b of the angle a and the angle b for measuring the PER, which is the first PER-angle curve, is the horizontal axis orthogonal to the vertical axis. In each value of the angle to be varied between the angle a and the angle b for measuring the PER that is the PER-angle a or angle b curve when τ is 0 and the PER that is the second PER-angle curve The phase difference τ was set to π Kino PER- angle sought and a or angle b curve is characterized by calculating the PER of the object to be measured from the intersection of the said first PER- angle curve second PER- angle curve.
[0045]
An example of a measuring apparatus for the polarization extinction ratio of the present invention is to change the angle b when the angle a is an unknown constant value, and to give the disturbance to the PMF at each value of the angle b. The first PER-angle curve and the second PER-angle curve are obtained by changing the phase difference τ in the PMF between at least 0 to 2π radians, and the first PER-angle curve and the first PER-angle curve The angle b giving the peak value of the second PER-angle curve, and the value of the angle b when the first PER-angle curve intersects the second PER-angle curve, to the PMF of the object to be measured An angle formed between the polarization direction of incident light and the intrinsic polarization axis of the PMF is obtained.
[0046]
An example of a measuring apparatus for the polarization extinction ratio or the like of the present invention varies the angle b, gives the disturbance to the PMF at each value of the angle b, and sets the phase difference τ in the PMF to at least 0 to 2π radians. The first PER-angle curve and the second PER-angle curve are obtained by varying the angle between the first PER-angle curve and the second PER-angle curve. The angle between the intrinsic polarization axis of the PMF of the object to be measured and the rotation reference direction of the polarization separation axis of the polarization separation element is obtained from the above value.
[0047]
An example of a measuring apparatus for the polarization extinction ratio or the like of the present invention varies the angle a by setting the angle b to a constant value, and gives the disturbance to the PMF at each value of the angle a to thereby change the position in the PMF. It is characterized by measuring the minimum value of the PER value that varies by changing the phase difference τ between at least 0 and 2π radians.
[0048]
In the example of the measuring apparatus for the polarization extinction ratio and the like of the present invention, the measuring apparatus is calculated using the branched output light amounts P (1) and P (2) given by the (Expression 9) and (Expression 10). The PER is changed by setting one of the angle a and the angle b to a constant value and changing the other, and the phase difference τ at each of the values of the angle a and the angle b to be changed is changed. Measured by changing between at least 0 to 2π according to the disturbance applied to the PMF, taking the PER on the vertical axis, and changing the angle a and the angle b on the horizontal axis perpendicular to the vertical axis. The graph shows the distribution of PER values at each value of the phase difference τ varied between at least 0 and 2π in the angle a and the angle b measured as described above. In the graph The amount of change in PER based on the change in the phase difference τ at each value of the angle a and the angle b to be changed is minimized, and the angle of the angle a and the angle b that is changed The PER value at which the minimum value of the PER value that changes based on the change in the phase difference τ in each value is maximized is obtained as the PER of the object to be measured.
[0049]
An example of a measuring apparatus for the polarization extinction ratio of the present invention is such that when the angle a is a certain unknown constant value, the angle b is varied, and the PMF is disturbed at each value of the angle b. In the graph representing the distribution of PER values measured by changing the phase difference τ in the PMF over at least 0 to 2π radians, the angle b at which the maximum value of PER at each value of the angle b is maximized , And the angle formed by the polarization direction of incident light incident on the PMF of the object to be measured and the intrinsic polarization axis of the PMF from the value of the angle b at which the minimum value of PER at each value of the angle b is maximized. It is characterized by being able to seek.
[0050]
The example of the measuring apparatus for the polarization extinction ratio and the like of the present invention varies the angle b regardless of the value of the angle a, and gives the disturbance to the PMF at each value of the angle b, thereby causing the phase difference in the PMF. In the graph showing the distribution of PER values measured by changing τ between at least 0 and 2π radians, from the value of the angle b at which the minimum value of PER at each value of the angle b is maximized, It is characterized in that an angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the rotation reference direction of the polarization separation axis of the polarization separation element can be obtained.
[0051]
The example of the measuring apparatus for the polarization extinction ratio and the like of the present invention varies the angle b regardless of the value of the angle a, and gives the disturbance to the PMF at each value of the angle b, thereby causing the phase difference in the PMF. In the graph showing the distribution of PER values measured by changing τ between at least 0 and 2π radians, from the value of the angle b at which the minimum value of PER at each value of the angle b is maximized, An angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the key direction of the connector of the PMF, or an angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the direction of the key groove of the adapter to which the connector of the PMF is attached. It is characterized by being able to seek.
[0052]
An example of a measuring apparatus for the polarization extinction ratio or the like of the present invention varies the angle a by setting the angle b to a constant value, and gives the disturbance to the PMF at each value of the angle a to thereby change the position in the PMF. It is characterized by measuring the minimum value of the PER value that varies by changing the phase difference τ between at least 0 and 2π radians.
[0053]
The example of the measuring apparatus for the polarization extinction ratio or the like of the present invention is characterized in that a vibration applying means for applying vibration to the optical fiber from the side surface direction of the optical fiber is used in the disturbance adding unit.
[0054]
In an example of a measuring apparatus for polarization extinction ratio and the like according to the present invention, the optical fiber is fixed and held by at least two fixing portions at predetermined intervals on both sides of the portion to which the disturbance is applied. The disturbance given to is characterized by being a disturbance given as vibration from the outside of the fiber to the portion between the two fixed parts of the fiber.
[0055]
In the example of the measuring apparatus such as the polarization extinction ratio of the present invention, the disturbance given to the optical fiber is given as vibration from the outside of the fiber so as to bend the part between the two fixed parts of the fiber. It is characterized by a disturbance.
[0056]
In the example of the measuring apparatus such as the polarization extinction ratio of the present invention, the disturbance given to the optical fiber has a period in a direction intersecting the length direction of the optical fiber in a portion between the two fixed portions of the fiber. It is characterized by a disturbance that is given as vibration from the outside of the fiber so as to periodically deflect the portion between the two fixed parts of the fiber by applying a vibrationally displaced vibration part.
[0057]
An example of a measuring apparatus for the polarization extinction ratio of the present invention is such that the excitation unit causes a disturbance in the optical fiber such that the phase difference between the intrinsic polarization modes of the optical fiber is changed between at least 0 to 2π radians. In the entire process, the portion of the optical fiber between the two fixed portions is applied to the fiber so as to bend the optical fiber periodically in the same direction that intersects the length of the optical fiber. It is characterized by having.
[0058]
In the example of the measuring apparatus for the polarization extinction ratio or the like of the present invention, the predetermined distance between the two fixing parts for fixing the optical fiber is 100 mm, and the length of the optical fiber between the two fixing parts is The displacement in the direction orthogonal to the direction is characterized in that the initial value is 1 mm and the maximum value is 3 ± 1 mm in the same direction in the whole process of giving the disturbance.
[0059]
The example of the measuring apparatus for the polarization extinction ratio of the present invention is characterized in that the disturbance given to the optical fiber is a disturbance that changes at 2 Hz (Hertz).
[0060]
In order to achieve the object of the present invention, the polarization extinction ratio measurement method according to the present invention is used as a branched output light quantity when coherent light is incident on and output from an optical fiber or optical device that is an object to be measured. Measurement method of polarization extinction ratio and the like for measuring optical powers P (1) and P (2) of polarization modes orthogonal to each other and PER = 10 log (P (1) / P (2)) as a ratio thereof In the measurement method, a part of the optical fiber is used with a disturbance adding means for giving a disturbance that changes the phase difference between the intrinsic polarization modes of the optical fiber over at least 0 to 2π radians, Disturbance that causes the phase difference between the intrinsic polarization modes of the optical fiber to vary between at least 0 to 2π radians on a part of the optical fiber by the disturbance adding means. The optical power P (1) and P (2) when given and a function capable of measuring PER are characterized.
[0061]
An example of a method for measuring the polarization extinction ratio, etc. of the present invention is that the measurement method is such that the coherent light is incident on an optical fiber that is the object to be measured or an optical device having an optical fiber, and the output light is guided to a polarization separation element. Measurement of polarization extinction ratio, etc. for measuring optical powers P (1) and P (2) of polarization modes orthogonal to each other as output light quantity and PER = 10 log (P (1) / P (2)) as a ratio thereof A method in which a part of the optical fiber is perturbed so as to change a phase difference between intrinsic polarization modes of the optical fiber over at least 0 to 2π radians, and a specific parameter is changed. The amount of change in the PER with respect to the specific parameter is minimized, and the minimum value of the PER corresponding to each value of the specific parameter in the measurement target range is maximized. The seeking is characterized by determining the value of PER of the object to be measured.
[0062]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is a disturbance that gives a disturbance to a part of the optical fiber such that the phase difference between the intrinsic polarization modes of the optical fiber is changed between 0 and 2π radians. The method of giving is a method of giving a disturbance so that the phase difference changes stepwise, and a step motor can be used as the means for giving the disturbance.
[0063]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is a disturbance that gives a disturbance to a part of the optical fiber such that the phase difference between the intrinsic polarization modes of the optical fiber is changed between 0 and 2π radians. The method of giving is a method of giving a disturbance so that the phase difference changes continuously, and a motor can be used as the means for giving the disturbance.
[0064]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is an optical power of a polarization mode in which the optical power P (1) vibrates in a direction parallel to the polarization separation axis of the polarization separation element, and the optical power P ( 2) is the optical power of a polarization mode that vibrates in a direction perpendicular to the polarization separation axis of the polarization separation element.
[0065]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is characterized in that the optical fiber is PMF.
[0066]
An example of a method for measuring a polarization extinction ratio or the like of the present invention is that the specific parameter includes an angle formed between an intrinsic polarization axis of the PMF as a measurement object and a polarization direction of incident light incident on the PMF, and It is one or both of the angles formed between the intrinsic polarization axis of the PMF as a measurement object and the polarization separation axis of the polarization separation element.
[0067]
An example of a method for measuring a polarization extinction ratio or the like according to the present invention is an angle formed by the method of changing the specific parameter between the intrinsic polarization axis of the PMF as a measurement object and the polarization direction of incident light incident on the PMF. In addition, the method is characterized in that one of the angles formed by the intrinsic polarization axis of the PMF as the object to be measured and the polarization separation axis of the polarization separation element is fixed and the other is changed for measurement.
[0068]
  The example of the measuring method of the polarization extinction ratio and the like of the present invention can measure the PER of the object to be measured, and can also measure the angle between the intrinsic polarization axis of the PMF and the polarization direction of the incident linearly polarized light incident on the PMF, and the Angle formed by the rotation reference direction of the polarization axis of the polarization separation element and the polarization axis of the PMFDegreeAt least one of them can be measured simultaneously with the measurement of the PER.
[0069]
In an example of a method for measuring the polarization extinction ratio and the like of the present invention, the measurement method is calculated by using the branched output light amounts P (1) and P (2) given by (Formula 9) and (Formula 10). The PER is changed by setting one of the angle a and the angle b to a constant value and changing the other, and the phase difference τ at each of the values of the angle a and the angle b to be changed is changed. The first PER-angle is measured by changing the PER according to the disturbance given to the PMF, taking the PER on the vertical axis, and taking the angle a and the angle b to be changed on the horizontal axis perpendicular to the vertical axis. PER-angle a or angle b curve when the phase difference τ in each value of the angle a and the angle b to be measured is the curve that measures the PER, which is a curve, and a second PER -Measure the PER which is an angle curve The PER-angle a or the angle b curve when the phase difference τ at each value of the angle a to be changed between the angle a and the angle b is set to π, and the first PER-angle curve The PER of the object to be measured is calculated from the intersection with the second PER-angle curve.
[0070]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is to vary the angle b when the angle a is an unknown constant value, and give the disturbance to the PMF at each value of the angle b. The first PER-angle curve and the second PER-angle curve are obtained by changing the phase difference τ in the PMF between at least 0 to 2π radians, and the first PER-angle curve and the first PER-angle curve The angle b giving the peak value of the second PER-angle curve, and the value of the angle b when the first PER-angle curve intersects the second PER-angle curve, to the PMF of the object to be measured An angle formed between the polarization direction of incident light and the intrinsic polarization axis of the PMF is obtained.
[0071]
  An example of a method for measuring the polarization extinction ratio or the like of the present invention is to vary the angle b, give the disturbance to the PMF at each value of the angle b, and set the phase difference τ in the PMF to at least 0 to 2π radians. The first PER-angle curve and the second PER-angle curve are obtained by varying the angle between the first PER-angle curve and the second PER-angle curve. Between the intrinsic polarization axis of the PMF of the object to be measured and the rotation reference direction of the polarization separation axis of the polarization separation elementDegreeIt is characterized by seeking.
[0072]
An example of a method for measuring a polarization extinction ratio or the like of the present invention is to vary the angle a by setting the angle b to a constant value, and give the disturbance to the optical fiber at each value of the angle a. The minimum value of the PER value that varies by changing the phase difference τ between at least 0 and 2π radians is measured.
[0073]
In an example of a method for measuring the polarization extinction ratio and the like of the present invention, the measurement method is calculated by using the branched output light amounts P (1) and P (2) given by (Formula 9) and (Formula 10). The PER is changed by setting one of the angle a and the angle b to a constant value and changing the other, and the phase difference τ at each of the values of the angle a and the angle b to be changed is changed. Measured by changing between at least 0 to 2π according to the disturbance applied to the PMF, taking the PER on the vertical axis, and changing the angle a and the angle b on the horizontal axis perpendicular to the vertical axis. The graph shows the distribution of PER values at each value of the phase difference τ varied between at least 0 and 2π in the angle a and the angle b measured as described above. In the graph The amount of change in PER based on the change in the phase difference τ at each value of the angle a and the angle b to be changed is minimized, and the angle of the angle a and the angle b that is changed The PER value at which the minimum value of the PER value that changes based on the change in the phase difference τ in each value is maximized is obtained as the PER of the object to be measured.
[0074]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is to change the angle b when the angle a is an unknown constant value, and to disturb the PMF at each value of the angle b. In the graph representing the distribution of PER values measured by changing the phase difference τ in the PMF over at least 0 to 2π radians, the angle b at which the maximum value of PER at each value of the angle b is maximized , And the angle formed by the polarization direction of incident light incident on the PMF of the object to be measured and the intrinsic polarization axis of the PMF from the value of the angle b at which the minimum value of PER at each value of the angle b is maximized. It is characterized by being able to seek.
[0075]
  An example of a method for measuring the polarization extinction ratio or the like of the present invention is to vary the angle b regardless of the value of the angle a, and to give the disturbance to the PMF at each value of the angle b, so that the phase difference in the PMF. In the graph showing the distribution of PER values measured by changing τ between at least 0 and 2π radians, from the value of the angle b at which the minimum value of PER at each value of the angle b is maximized, The angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the rotation reference direction of the polarization separation axis of the polarization separation elementDegreeIt is characterized by being able to seek.
[0076]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is to vary the angle b regardless of the value of the angle a, and to give the disturbance to the PMF at each value of the angle b, so that the phase difference in the PMF. In the graph showing the distribution of PER values measured by changing τ between at least 0 and 2π radians, from the value of the angle b at which the minimum value of PER at each value of the angle b is maximized, An angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the key direction of the connector of the PMF or an angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the key groove of the adapter to which the connector of the PMF is attached is obtained. It is characterized by being able to.
[0077]
An example of a method for measuring the polarization extinction ratio or the like of the present invention is to vary the angle a by setting the angle b to be a constant value, and to give the disturbance to the PMF at each value of the angle a to thereby change the position in the PMF. It is characterized by measuring the minimum value of the PER value that varies by changing the phase difference τ between at least 0 and 2π radians.
[0078]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. The drawings used for the description schematically show the dimensions, shapes, positional relationships, and the like of the constituent components to the extent that the present invention can be understood. For convenience of explanation of the present invention, there may be a case where the enlargement ratio is partially changed for illustration, and only necessary portions may be illustrated, and the drawings used for the description of the present invention are not necessarily actual objects such as embodiments. And may not be similar to the description. Moreover, in each figure, about the same component, it attaches and shows the same number, The overlapping description may be abbreviate | omitted.
[0079]
In addition, the description of the measurement method of the present invention that can be used for the measurement device of the present invention overlaps with the measurement method described as an example used in the description of the measurement device of the present invention. However, the description of the measuring apparatus of the present invention also serves as an explanation of the measuring method.
[0080]
FIG. 1 and FIG. 2 are diagrams for explaining the outline of a measuring apparatus for the polarization extinction ratio and the like of the present invention. FIG. 1 shows a case where the object to be measured is an optical fiber and coherent probe light is used as a light source for measurement. 2 is a diagram for explaining the case where the object to be measured is a laser diode module in which a PMF is attached to a laser diode.
[0081]
1 and 2, reference numeral 1 is a coherent probe light as a measurement light source, 11 is a laser diode module to which a PMF 21 is attached, 2 is a PMF as an optical fiber of an object to be measured, and 3 is disturbed by the PMF 2 or the PMF 21 4 and 5 are connectors, 6 is a detector, 7 is a polarization separation element, 8 is the optical power of the polarization component that vibrates in the direction perpendicular to the polarization separation axis, and 9 is The optical power of the polarization component that vibrates in the direction parallel to the polarization separation axis, 10 is a PER calculation unit, x-axis is the intrinsic polarization axis of the PMFs 2 and 21, and y-axis is an axis orthogonal to the x-axis at the end face of the PMF.
[0082]
For convenience of illustration, the vibration exciter 3 is illustrated as being separated from the PMF 2 and the PMF 21 in the drawing, but is actually arranged so as to contact the PMF 2 and the PMF 21, respectively.
[0083]
In FIG. 1 or FIG. 2, the linearly polarized light that has entered the PMF 2 or the PMF 21 from the coherent probe light 1 or the laser diode module 11 enters the polarization separation element 7 of the detection unit 6 from the connector 5. As will be described later, the polarization separation element 7 can rotate about an axis parallel to the direction of incident light from the PMF. Light incident on the polarization separation element 7 of the detection unit 6 from the connector 5 is polarized light oscillating in a direction parallel to the polarization separation axis, and the optical power 8 of the polarization component that vibrates in the direction perpendicular to the polarization separation axis by the polarization separation element 7. The component is detected by being separated into the optical power 9, and the value is input to the PER calculator 10 to calculate the PER, and is output from the detector 6 as the PER measurement result. In this PER measurement process, the vibrator 3 causes the PMF 2 and the PMF 21 to be disturbed by changing the phase difference between the intrinsic polarization modes of the PMF 2 and the PMF 21 over at least 0 to 2π radians by the method described later. The change in PER due to the disturbance is measured.
[0084]
More specific description will be given below.
[0085]
FIG. 3 is a diagram for explaining the polarization mode, where a is the angle formed by the direction of linearly polarized light incident on each PMF and the x axis that is the intrinsic polarization axis of the PMF, and b is the polarization separation axis of the polarization separation element 7. This is the angle made with the x-axis.
[0086]
FIG. 4 is a diagram for explaining the disturbance adding unit including the vibrator 3 described with reference to FIGS. 1 and 2. Reference numeral 22 denotes a disturbance adding unit, reference numeral 23 denotes a support base, and reference numeral 24 denotes an optical fiber as an object to be measured. The fiber clamp 25 as a fixing tool to be held is to prevent local stress on the optical fiber as the object to be measured when measuring the PER according to the present invention, and as a substantial fixing part of the optical fiber. The supporting strut 26 is a tension applying portion which is a part of the vibrator 3, and is a portion which gives a disturbance to the optical fiber which is an object to be measured disposed between the two struts 25 shown in the figure, 27 is a stopper, 45 , 46 and 47 are arrows. The support base 23 can stably support an optical fiber as an object to be measured, and a motor or a linear motion guide (hereinafter, linear motion is also referred to as LM) as an excitation force source of the tension applying unit 26 inside. ) Etc. are attached.
[0087]
FIG. 5 is a diagram for explaining the tension applying portion 26, wherein reference numeral 28 denotes an LM guide, 29 denotes a tension applying plate, 30 denotes a spring fixing column A attached to the tension applying plate 29, and 31 denotes a rotating plate 39 of the motor 33. The spring fixing columns B and 32 attached eccentrically from the rotation center 38 of the motor 33 are springs, 34 is a portion protruding on the support 23 of the tension applying plate 29 in FIG. 4, and 35 is the tension applying plate 29. An arrow indicating the vibration direction and amplitude, 36 is an arrow indicating the rotation direction of the rotating plate 39 of the motor 33, and 37 is an end portion of the tension applying plate 29.
[0088]
6 and 7 are views for explaining the LM guide 28, FIG. 6 is a plan view, and FIG. 7 is a cross-sectional view. 6 and 7, reference numeral 40 denotes an LM rail, that is, a linear motion rail, 41 denotes an LM block, and the LM block 41 is a convex portion of a portion indicated by reference numerals 42 and 43 and is coupled to a concave portion of the LM rail to move on the LM rail. It is possible to move accurately and smoothly in both directions indicated by the arrow 44. The tension applying plate 29 is fixed to the LM block 41 and moves together with the LM block 41.
[0089]
In FIG. 5, according to the rotation of the motor 33, the extension force of the spring 32 is periodically changed by the movement of the spring fixing column B provided at a position deviated from the rotation center 38 of the rotating plate 39. The spring fixing column A receives a tensile force that changes periodically. The tension applying plate 29 to which the spring fixing column A is attached is attached to the LM block 41 having the structure described with reference to FIGS. Vibrate in the direction.
[0090]
FIG. 8 is a diagram for explaining a method of giving a disturbance that causes the PMF attached to the disturbance adding unit 22 to change the phase difference between the eigenpolarization modes over at least 0 to 2π radians. In FIG. 8, reference numeral 50 denotes a connection line for electrically connecting the motor 33 of the vibrator and the motor control circuit, and 51 denotes an extinction ratio measuring device main body. The extinction ratio measuring device main body 51 is provided with the motor control circuit, a light receiving unit and a calculation unit which are components of the detection unit 6.
[0091]
In FIG. 8, an optical fiber as a measurement object is attached to the disturbance adding unit 22 as follows.
[0092]
First, the tension applying section 26 is moved by a predetermined amount in the direction of the arrow 46 shown in FIG. 4, and the movable portion of the stopper 27 is moved in the direction of the arrow 47 shown in FIG. 4 to stop the tension applying section 26 in a predetermined position. . In this state, the PMF 21 coming out from the laser diode module 11 is first fixed by being sandwiched by the left fiber clamp 24 in the drawing, and the PMF coming out from the fiber clamp 24 to the opposite side of the laser diode module 11 is fixed to the left side. From the left side of the column 25 through the other side, contact the predetermined position of the column 25 on the left side, and toward the column 25 on the right side, passing in front of the tension applying part 26 that is retracted in the direction of the arrow 46, the right column 25 The right column 25 and the right column 25 through the right side to the right fiber clamp 24, and the PMF between the left column 25 and the right column 25 is adjusted so that it is straight. In this state, the PMF is fixed to the right fiber clamp 24, and the connector 5 attached to the end of the PMF is connected to the extinction ratio measuring device body 5 Attached to the adapter. In this state, the tension applying portion 26 pulled in the direction of the arrow 46 is pressed, the stopper 27 is pulled in the direction opposite to the arrow 47 to release the pressing of the tension applying portion 26, and the tension applying portion 26 is moved as shown in FIG. Returning to the direction of the arrow 45, the PMF 21 is brought into contact with a predetermined position. At this time, even when the tension applying portion 26 is vibrated and vibrated, the portion of the PMF that is in contact with the tension applying portion 26 is bent by a predetermined amount in FIG. Thus, it is preferable to set the initial position of the tension applying unit 26.
[0093]
As a preferred example, the distance between the centers of the left column 25 and the right column 25 is 10 cm, the deflection amount of the PMF in the initial position of the tension applying unit 26 is 1 mm, and the directions of the arrows 45 and 46 of the tension applying unit 26 The frequency of the PMF is 2 ± 1 mm due to the vibration of the tension applying unit 26 in the directions of the arrows 45 and 46, and the phase difference between the intrinsic polarization modes is at least 0. An angle formed by the PER, the intrinsic polarization axis of the PMF of the object to be measured and the polarization direction of the incident light incident on the PMF, while giving a disturbance that continuously and periodically changes between ˜2π radians, and The deviation angle between the intrinsic polarization axis of the PMF as the object to be measured and the key direction of the connector was measured. Here, the key direction of the connector is substantially the same as the key groove direction of the adapter to which the connector is attached, and it is preferable that which one is used during measurement is appropriately determined depending on the configuration of the measurement system.
[0094]
FIG. 9 is a diagram for explaining a main part of the extinction ratio measuring device main body 51. In FIG. 9, reference numeral 52 is a main part of the detection unit, 53 is an optical adapter such as an FC type or SC type, 54 is a polarization separation element, and 55 and 56 are separated by the polarization separation element 54 and output to be orthogonal to each other. A photodiode 57 for detecting the optical powers P (1) and P (2) in the polarization mode is an arithmetic circuit.
[0095]
The polarization separation element 54 and the photodiodes 55 and 56 are integrated, and are rotated about the transmission direction of light incident on the polarization separation element 54 as an axis, so that the intrinsic polarization axis of the PMF and the polarization separation axis of the polarization separation element are formed. For example, by changing the angle in a stepped manner, the PMF that is the object to be measured at each of the angles is subjected to a disturbance that changes the phase difference between the intrinsic polarization modes continuously and periodically over at least 0 to 2π radians. Then, the output light of the polarization separation element is measured.
[0096]
The connector 5 attached to the PMF 21 in FIG. 8 is connected to the optical adapter 53 in FIG. As a result, the light that is transmitted from the laser diode of the laser diode module 11 and transmitted through the PMF 21 is transmitted to the PMF 21 by the tension applying unit 26 of the disturbance applying unit 22 during transmission of the PMF. The phase difference between them is added with a disturbance that changes continuously and periodically over at least 0 to 2π radians, and is emitted from the end where the PMF connector 5 is attached to the polarization separation element 54. The incident light is branched by the polarization separation element 54, detected by the photodiodes 55 and 56, respectively, sent to the arithmetic circuit 57 as a current waveform, and the polarization direction of the incident light incident on the PMF with respect to the intrinsic polarization axes of PER and PMF. Displacement angle, displacement angle between the intrinsic polarization axis of the PMF and the key direction of the connector are calculated.
[0097]
The configuration of the main part of the measuring apparatus such as the polarization extinction ratio of the present invention has been outlined above. For example, the branched output light amount from the polarization separation element in FIG. 9 changes sensitively depending on several parameters.
[0098]
Therefore, the main part of the technical idea of the present invention will be described below.
[0099]
As one of the specific parameters, an angle formed by the polarization axis of the incident light incident on the PMF and the polarization direction of the incident light incident on the PMF is an angle a (unit: radians). One is that the angle between the intrinsic polarization axis of the PMF that is the object to be measured and the polarization separation axis of the polarization separation element is an angle b (unit: radians), and the PMF that is the object to be measured is disturbed. When the phase difference between the intrinsic polarization modes of the PMF generated in the PMF is τ (unit: radians), the optical powers P (1) and P (2) orthogonal to each other branched and output from the polarization separation element are It is given by the following mathematical formulas (11) and (12).
[0100]
## EQU11 ##

[Expression 12]

The polarization extinction ratio PER can be calculated by the following mathematical formula (Formula 13).
[0101]
[Formula 13]

The PER given by the above equation changes between the PER-angle curve 60 and the PER-angle curve 61 of FIG. 10 when the angle a or the angle b is changed. However, in FIG. 10, the unit of the angle a and the angle b is expressed in degrees instead of radians. That is, when the angle a or the angle b is taken on the horizontal axis and the PER is taken on the vertical axis as specific parameters, the PER at each value of the angle a or the angle b is sandwiched between the PER-angle curve 60 and the PER-angle curve 61. The value of the range (range indicated by reference numeral 65, hereinafter also referred to as range 65). The change in PER in the range 65 sandwiched between the PER-angle curve 60 and the PER-angle curve 61 is caused by the phase difference τ changing between 0 and 2π radians.
[0102]
In FIG. 10, reference numeral 62 is the maximum value of the PER-angle curve 60, reference numeral 63 is the maximum value of the PER-angle curve 61, and reference numeral 64 is an intersection of the PER-angle curve 60 and the PER-angle curve 61. The PER value at the intersection point 64 gives the PER of the PMF as the object to be measured in the present invention. When the angle a is fixed and the angle b is changed, that is, when the horizontal axis is the angle b, the angle giving the maximum value 62 or the angle giving the maximum value 63 and the angle of the intersection 64 From this difference, the deviation angle α of the polarization direction of the incident light with respect to the intrinsic polarization axis of the PMF can be obtained. Further, the deviation angle β between the intrinsic polarization axis of the PMF and the key direction of the connector can be obtained from the angle giving the intersection 64.
[0103]
FIG. 11 to FIG. 18 are graphs obtained as a result of simulation based on Equations 5 to 7, where the vertical axis represents the extinction ratio (unit: dB) and the horizontal axis represents the angle (unit: degree).
[0104]
11 shows the extinction ratio-angle a characteristic when the angle b = 0 degrees, FIG. 12 shows the extinction ratio-angle a characteristic when the angle b = 2.5 degrees, and FIG. FIG. 14 shows the extinction ratio-angle a characteristic when the angle b = 5 degrees, FIG. 14 shows the extinction ratio-angle a characteristic when the angle b = 10 degrees, and FIG. 15 shows the angle a = 0 degree. 16 shows the extinction ratio-angle b characteristic, FIG. 16 shows the extinction ratio-angle b characteristic when the angle a = 2 degrees, and FIG. 17 shows the extinction ratio when the angle a = 5 degrees- The angle b characteristic is shown, and FIG. 18 shows the extinction ratio-angle b characteristic when the angle a = 10 degrees.
[0105]
11 to 18, reference numerals 601, 603, 604, 605, 606, 610, 611, 612, 613, 620, 621, 622, 623, 700, 720, 721, 730, 731, 770, 771, 780, 781, 820, 821, 830, 831 are extinction ratio-angle characteristic curves, 602, 607, 608, 614, 615, 624, 625, 710, 740, 750, 790, 800, 840, 850 are extinction ratio-angles. The maximum or maximum value of the characteristic curve, 609, 616, 626, 760, 810, 860, is the intersection of the two extinction ratio-angle characteristic curves.
[0106]
As described above, FIGS. 11 to 14 are extinction ratio-angle characteristic curves when the angle b is a constant value and the angle a is a parameter, and FIGS. 15 to 18 are the angles a and the angle b. It is an extinction ratio-angle characteristic curve when is used as a parameter.
[0107]
As can be seen from FIG. 11, when the angle b is 0 degree, the PER changes on the extinction ratio-angle characteristic curve 700 regardless of the value of the phase difference τ. At this time, the PER of the object to be measured in the present invention coincides with the maximum value of the extinction ratio-angle characteristic curve 700. The angle a at that time is 0 degree.
[0108]
12 to 14 show a case where the angle b is not zero. When the phase difference τ is 0 radians, the PER is given by a curve in which the angle giving the maximum value is positive in the figure, and when the phase difference τ is π radians, the PER gives the maximum value in the figure. Given as a curve with negative angles. When τ is between 0 and π radians, the PER of the object to be measured takes a value in a range sandwiched between the two extinction ratio-angle characteristic curves shown in the figure due to the change in the phase difference τ.
[0109]
In FIG. 12, the extinction ratio-angle characteristic curve 720 and the extinction ratio-angle characteristic curve 721 are the same extinction ratio-angle characteristic curve in terms of mathematical formulas, and the left part of the intersection 760 is the extinction ratio-angle characteristic curve 720, the intersection 760. The right part of the graph is an extinction ratio-angle characteristic curve 721. The extinction ratio-angle characteristic curve 730 and the extinction ratio-angle characteristic curve 731 are the same extinction ratio-angle characteristic curve. The left part of the intersection point 760 is the extinction ratio-angle characteristic curve 730 and the right part of the intersection point 760 is. It is an extinction ratio-angle characteristic curve 731.
[0110]
As apparent from FIG. 12, on the left side of the intersection point 760, the extinction ratio-angle characteristic curve 720 is the upper limit of the extinction ratio-angle characteristic curve, and no matter how the phase difference τ changes, The extinction ratio-angle characteristic curve never takes a value above the extinction ratio-angle characteristic curve 720, and the extinction ratio-angle characteristic curve 730 is the lower limit of the extinction ratio-angle characteristic curve, and the phase difference τ However, the extinction ratio-angle characteristic curve at that time does not take a value lower than the extinction ratio-angle characteristic curve 730. On the right side of the intersection 760, the extinction ratio-angle characteristic curve 731 is the upper limit of the extinction ratio-angle characteristic curve, and no matter how the phase difference τ changes, the extinction ratio-angle characteristic curve at that time is changed. Never takes a value above the extinction ratio-angle characteristic curve 731, and the extinction ratio-angle characteristic curve 721 is the lower limit of the extinction ratio-angle characteristic curve, and how the phase difference τ changes. However, the extinction ratio-angle characteristic curve at that time never takes a value lower than the extinction ratio-angle characteristic curve 721. In consideration of this, the left and right sides of the equation are different curves on the left and right sides of the intersection 760, but the extinction ratio based on the change in the phase difference τ—the extinction ratio corresponding to the upper limit of the change in the angle characteristic curve— The angle characteristic curve 720 and the extinction ratio-angle characteristic curve 731 are also referred to as upper lines, and the extinction ratio-angle characteristic curve 730 and the extinction ratio-angle corresponding to the lower limit of the extinction ratio-angle characteristic curve based on the change in the phase difference τ. The characteristic curve 721 is also referred to as a lower line.
[0111]
In FIG. 13, an extinction ratio-angle characteristic curve 770 and an extinction ratio-angle characteristic curve 771 are mathematically the same extinction ratio-angle characteristic curve, and the left part of the intersection 810 is the extinction ratio-angle characteristic curve 770, the intersection 810. The right-hand part is an extinction ratio-angle characteristic curve 771. The extinction ratio-angle characteristic curve 780 and the extinction ratio-angle characteristic curve 781 are the same extinction ratio-angle characteristic curve, the left part of the intersection 810 is the extinction ratio-angle characteristic curve 780, and the right part of the intersection 810 is This is an extinction ratio-angle characteristic curve 781.
[0112]
In FIG. 14, the extinction ratio-angle characteristic curve 820 and the extinction ratio-angle characteristic curve 821 are the same extinction ratio-angle characteristic curve in terms of mathematical formulas, and the left part of the intersection 860 is the extinction ratio-angle characteristic curve 820, the intersection 860. The right-hand part is an extinction ratio-angle characteristic curve 821. Also, the extinction ratio-angle characteristic curve 830 and the extinction ratio-angle characteristic curve 831 are the same extinction ratio-angle characteristic curve, the left part of the intersection 860 is the extinction ratio-angle characteristic curve 830 and the right part of the intersection 860 is the right part. It is an extinction ratio-angle characteristic curve 831.
[0113]
As can be seen from FIG. 15, when the angle a is 0 degree, the PER changes on the extinction ratio-angle characteristic curve 601 regardless of the value of the phase difference τ. At this time, the PER of the object to be measured in the present invention coincides with the maximum value of the extinction ratio-angle characteristic curve 601. The angle b at that time is 0 degree.
[0114]
16 to 18 show a case where the angle a is not zero. When the phase difference τ is 0 radians, the PER is given by a curve in which the angle b giving the maximum value is positive in the figure, and when the phase difference τ is π radians, the PER shows the maximum value in the figure. The given angle b is given as a negative curve. When τ is between 0 and π radians, the PER of the object to be measured takes a value in a range sandwiched between the two extinction ratio-angle characteristic curves shown in the figure due to the change in the phase difference τ.
[0115]
In FIG. 16, the extinction ratio-angle characteristic curve 603 and the extinction ratio-angle characteristic curve 604 are mathematically the same extinction ratio-angle characteristic curve, and the left part of the intersection 609 is the extinction ratio-angle characteristic curve 603, the intersection 609. The right-hand part is an extinction ratio-angle characteristic curve 604. The extinction ratio-angle characteristic curve 605 and the extinction ratio-angle characteristic curve 606 are the same extinction ratio-angle characteristic curve. The left part of the intersection 609 is the extinction ratio-angle characteristic curve 605 and the right part of the intersection 609 is the same. This is an extinction ratio-angle characteristic curve 606.
[0116]
As is clear from FIG. 16, on the left side of the intersection 609, the extinction ratio-angle characteristic curve 603 is the upper limit of the extinction ratio-angle characteristic curve, and no matter how the phase difference τ changes, The extinction ratio-angle characteristic curve never takes a value above the extinction ratio-angle characteristic curve 603, and the extinction ratio-angle characteristic curve 605 is the lower limit of the extinction ratio-angular characteristic curve, and the phase difference τ However, the extinction ratio-angle characteristic curve at that time does not take a value lower than the extinction ratio-angle characteristic curve 605. On the right side of the intersection 609, the extinction ratio-angle characteristic curve 606 is the upper limit of the extinction ratio-angle characteristic curve, and the extinction ratio-angular characteristic curve at that time no matter how the phase difference τ changes. Never takes a value above the extinction ratio-angle characteristic curve 606, and the extinction ratio-angle characteristic curve 604 is the lower limit of the extinction ratio-angle characteristic curve, and how the phase difference τ changes. However, the extinction ratio-angle characteristic curve at that time never takes a value lower than the extinction ratio-angle characteristic curve 604. In consideration of such a situation, the left and right sides of the equation are different curves at the intersection 609, but the extinction ratio based on the change in the phase difference τ-the extinction ratio corresponding to the upper limit of the change in the angle characteristic curve- The angle characteristic curve 603 and the extinction ratio-angle characteristic curve 606 are also referred to as upper lines, and the extinction ratio-angle characteristic curve 604 and the extinction ratio-angle corresponding to the lower limit of the extinction ratio-angle characteristic curve based on the change in the phase difference τ. The characteristic curve 606 is also referred to as a lower line.
[0117]
In FIG. 17, the extinction ratio-angle characteristic curve 610 and the extinction ratio-angle characteristic curve 611 are the same extinction ratio-angle characteristic curve in terms of mathematical formulas, and the left part of the intersection 616 is the extinction ratio-angle characteristic curve 610 and the intersection 616. The right-hand part is an extinction ratio-angle characteristic curve 611. The extinction ratio-angle characteristic curve 612 and the extinction ratio-angle characteristic curve 613 are the same extinction ratio-angle characteristic curve. The left part of the intersection point 616 is the extinction ratio-angle characteristic curve 612 and the right part of the intersection point 616 is. This is an extinction ratio-angle characteristic curve 613.
[0118]
In FIG. 18, the extinction ratio-angle characteristic curve 620 and the extinction ratio-angle characteristic curve 621 are the same extinction ratio-angle characteristic curve in terms of mathematical formulas, and the left part of the intersection 626 is the extinction ratio-angle characteristic curve 620, the intersection 626. The right-hand part is an extinction ratio-angle characteristic curve 621. The extinction ratio-angle characteristic curve 622 and the extinction ratio-angle characteristic curve 623 are the same extinction ratio-angle characteristic curve. The left part of the intersection 626 is the extinction ratio-angle characteristic curve 622 and the right part of the intersection 626 is the right part. It is an extinction ratio-angle characteristic curve 623.
[0119]
12 and FIG. 16, the extinction ratio-angle characteristic curve 770 and extinction ratio-angle characteristic curve 781, the extinction ratio-angle characteristic curve 820, the extinction ratio-angle characteristic curve 831, and the extinction ratio-angle characteristic. The curve 610, the extinction ratio-angle characteristic curve 613, the extinction ratio-angle characteristic curve 620, and the extinction ratio-angle characteristic curve 623 are referred to as upper lines, respectively, and the extinction ratio-angle characteristic curve 780, the extinction ratio-angle characteristic curve 771, and the extinction ratio. Ratio-angle characteristic curve 830 and extinction ratio-angle characteristic curve 821, extinction ratio-angle characteristic curve 612 and extinction ratio-angle characteristic curve 611, extinction ratio-angle characteristic curve 622, and extinction ratio-angle characteristic curve 621 are respectively lower lines. That's it.
[0120]
11 and 15, it can be said that the upper line and the lower line overlap at the extinction ratio-angle characteristic curve 700 or the extinction ratio-angle characteristic curve 601.
[0121]
When the phase difference τ between the intrinsic polarization modes of the PMF changes over a range of 0 to 2π due to disturbance applied to the PMF as the object to be measured, the measured extinction ratio-angle characteristic curve is the upper line and the lower line. Fluctuate between.
[0122]
Although the concept about the upper line and the lower line is clear from the above description, in FIGS. 12 to 14 and FIGS. 16 to 18, reference numerals 603, 606, 610, 613, 620, 623, 720, 731, 770, The extinction ratio-angle characteristic curves indicated by 781, 820, 831 are upper lines in the present invention, and are indicated by reference numerals 604, 605, 611, 612, 621, 622, 721, 730, 771, 780, 821, 830. The extinction ratio-angle characteristic curve is the lower line in the present invention. The extinction ratio-angle characteristic curves indicated by reference numerals 601 and 700 can be said to be the case where the upper line and the lower line coincide.
[0123]
11 to 18, the PER of the object to be measured can be obtained from the PER value at the intersection of the upper line and the lower line.
[0124]
FIGS. 19 to 26 are graphs for explaining an example in which the polarization extinction ratio of PER is measured using the polarization extinction ratio measurement apparatus of the present invention.
[0125]
FIG. 19 is a graph showing the extinction ratio-angle a characteristic when the angle b is changed to 0 degree and the angle a is used as a parameter, and FIG. FIG. 21 is a graph showing the extinction ratio-angle a characteristic when the angle b is changed by using the angle a as a parameter, and FIG. 22 is a graph showing the angle b being 10 degrees. FIG. 23 is a graph showing the extinction ratio-angle a characteristic when the angle a is changed as a parameter. FIG. 23 shows an angle deviation between the polarization direction of the intrinsic polarization axis of the PMF and the incident angle, that is, the angle a is 0 degree, which will be described later. FIG. 24 is a graph showing the extinction ratio-angle characteristic when the angle of the light-receiving part is changed as a parameter, and FIG. 24 is a graph showing the extinction ratio-angle characteristic when the angle of the light-receiving part is changed as a parameter with the angle a being 2 degrees. FIG. FIG. 26 is a graph showing extinction ratio-angle characteristics when the angle a is 5 degrees and the light receiving section angle is changed as a parameter. FIG. 26 is an extinction ratio when the angle a is 10 degrees and the light receiving section angle is changed as a parameter. -Each graph showing angle characteristics is shown, the vertical axis is the extinction ratio (unit: dB), the horizontal axis is the angle a in FIGS. 19 to 22, and the light receiving unit angle in FIGS. . Here, the light receiving unit angle is an angle obtained by combining the angle b and the deviation angle between the intrinsic polarization axis of the PMF as the object to be measured and the key direction of the connector of the PMF or the key groove direction of the adapter to which the connector is attached. That is. For example, in the case described with reference to FIGS. 8 and 9, the extinction ratio measuring device main body 51 may display the light receiving unit angle as the rotation angle of the polarization separation element.
[0126]
19 to 26, reference numerals 96, 99, 130, 134, 121, 124, 140, 144, 530, 511, 173, 172, 191, 194, 501, and 504 represent upper lines, and 98, 97, Reference numerals 132, 131, 123, 122, 143, 141, 510, 531, 171, 174, 193, 192, 503, and 502 represent lower lines, respectively. Reference numerals 111, 136, 137, 125, 126, 145, 146, 167, 185, 186, 195, 196, 515, 516 denote local maximum values or maximum values of the upper lines, 112, 135, 127, 147, 168, respectively. Reference numerals 187, 197, and 517 are maximum values of the respective lower lines.
[0127]
19 to 26, the upper line 96 and the upper line 99 are the left and right curves of the angle that gives the maximum value 112 of the lower line, and the upper line 130 and the upper line 134 are the angles that give the maximum value 135 of the lower line. The upper line 121 and the upper line 124 are the left and right curves of the angle giving the maximum value 127 of the lower line, and the upper line 140 and the upper line 144 are the maximum value 147 of the lower line. The left and right curves of the given angle, the upper line 530 and the upper line 511 are the left and right curves of the angle giving the maximum value 168 of the lower line, and the upper line 173 and the upper line 172 are the maximum values of the lower line. The left and right curves of the angle giving 187 The upper line 191 and the upper line 194 are curves on the left and right sides of the angle that gives the maximum value 197 of the lower line, and the upper line 501 and the upper line 504 are on the left and right sides of the angle that gives the maximum value 517 of the lower line. It is a curve. The lower line 98 and the lower line 97 are curves on the left and right sides of the angle that gives the maximum value 112 of the lower line, and the lower line 132 and the lower line 131 are on the left and right sides of the angle that gives the maximum value 135 of the lower line. The lower line 123 and the lower line 122 are curves on the left and right sides of the angle that gives the maximum value 127 of the lower line, and the lower line 143 and the lower line 141 are on the left side of the angle that gives the maximum value 147 of the lower line. The lower line 510 and the lower line 531 are the left and right curves of the angle that gives the maximum value 168 of the lower line, and the lower line 171 and the lower line 174 are the angles that give the maximum value 187 of the lower line. Left and right curves, low The line 193 and the lower line 192 are curves on the left and right sides of the angle giving the maximum value 197 of the lower line, and the lower line 503 and the lower line 502 are curves on the left and right sides of the angle giving the maximum value 517 of the lower line. .
[0128]
The data in FIGS. 19 to 26 show the phase difference between the eigen polarization modes of the measured PMF as described with reference to FIGS. 4 to 8 at the measured PMF at each measurement point on the horizontal axis. Is given a disturbance (for example, a continuous disturbance with a frequency of 2 Hz), and the extinction ratio at that time is measured to obtain an extinction ratio obtained at each measurement point angle. The maximum value was recorded as the upper line in the figure, and the minimum value was recorded as the lower line.
[0129]
The points indicated by reference numerals 101 to 110 in FIG. 19, the points indicated by reference numerals 155 to 164 in FIG. 23, the points indicated by reference numerals 175 to 184 in FIG. 24, and the points indicated by reference numerals 505 to 514 in FIG. The example of the measurement point for demonstrating how to take is shown, The odd-numbered point is a point on an upper line, and the even-numbered point is a point on a lower line. In FIG. 19, points 101 and 102, 103 and 104, 105 and 106, 107 and 108, 109 and 110 are those when the angle a has the same value, and the angle a changes by 0.5 degrees. Yes. 23, points 155 and 156, 157 and 158, 159 and 160, 161 and 162, 163 and 164, and in FIG. 24, points 175 and 176, 177 and 178, 179 and 180, 181 and 182, and 183 In FIGS. 184 and 26, points 505 and 506, 507 and 508, 509 and 510, 511 and 512, 513 and 514 are obtained when the light receiving unit angles have the same value, and the light receiving unit angle changes by 1 degree. .
[0130]
Referring to FIG. 19 as an example, the PER is measured by changing the angle a by 0.5 degrees. In the course of the measurement, the change of the angle a is stopped at each measurement point, and the intrinsic polarization mode is applied to the measured PER. The PER was measured while applying a disturbance such that the phase difference τ between them varied between 0 and 2π. For example, the change of the angle a is stopped at the angle a at the points 101 and 102 for a predetermined time, and the motor is continuously rotated as described with reference to FIGS. 4 to 8 to disturb the PMF of the object to be measured. The maximum and minimum values of PER are obtained while giving, and then the angle a is changed by 0.5 degrees, and the change of the angle a is stopped again at the angle a at the points 103 and 104 for a predetermined time, and FIGS. As described above, the maximum value and the minimum value of PER are obtained while continuously rotating the motor to give a disturbance to the PMF, and then the angle a is changed by 0.5 degrees to obtain points at points 105 and 106. The change in the angle a is stopped again at the angle a for a predetermined time, and the maximum and minimum values of PER are obtained while applying the disturbance. Similarly, the PER is measured at the angle a at points 107 and 108, and then the points 109 and 110 Measured at an angle a, To obtain the data of FIG. 19 continues to measure as.
[0131]
In FIG. 19, the change of the angle a is stopped at the angle a at the points 101 and 102 for a predetermined time, and the motor is continuously rotated as described with reference to FIGS. When measuring the PER of an object to be measured while giving a disturbance, when the phase difference τ between the intrinsic polarization modes of the PMF is not known in the initial state of the measurement, the measured PER is a point. The value is between the values of PER at 101 and 102. When the PER is measured while continuously perturbing the PMF such that the phase difference τ between the intrinsic polarization modes of the PMF varies between 0 and 2π, the measured PER value is the point 101. A value between the value and the value at the point 102 is shown, and the PER at the point 101 is reliably determined as the maximum value, and the PER at the point 102 is reliably determined as the minimum value. The same applies to the measurement points in FIGS. 23, 24, and 26.
[0132]
23, the difference in PER between points 163 and 164, the difference between the maximum and minimum values of PER at each measurement point, the difference between PERs at points 179 and 180 in FIG. 24, and the maximum and minimum of PER at each other measurement point. As apparent from the difference in values, the difference in PER between points 513 and 514 in FIG. 26, and the difference between the maximum and minimum values of PER at each measurement point, the maximum and minimum PER at each measurement point depends on the measurement conditions. There is a big difference in value difference.
[0133]
In the data of FIGS. 19 to 22, the maximum value of each lower line is at an angle a = 0 degrees, but the maximum value of each lower line does not exactly match the angle a = 0.0 degrees. This is due to measurement errors. Further, in each of FIGS. 20 to 22, the difference between each maximum value of the upper line and the maximum value of the lower line matches the value of the angle b with the angle fixed.
[0134]
In the data of FIGS. 23 to 26, the value of the light receiving unit angle that gives the maximum value of each lower line is deviated from 0 degree. From this deviation amount, the key axis of the PMF connector and the key direction of the PMF connector or its The shift angle in the direction of the keyway of the adapter of the measuring instrument main body to which the connector is attached can be obtained. Further, the deviation angle α between the intrinsic polarization axis of the PMF and the polarization separation axis of the polarization separation element can be obtained from the difference between the light reception portion angle that gives the maximum value of the lower line and the light reception portion angle that gives the maximum value of the upper line. I understand.
[0135]
That is, in the data of FIGS. 19 to 26, the correct PER of the PMF of the object to be measured can be obtained from the maximum value of the lower line, and the key direction of the connector attached to the PMF can be calculated using the same data. The amount of deviation from the polarization intrinsic axis of the PMF, the amount of deviation of the incident polarization direction from the polarization intrinsic axis of the PMF, and the like can be obtained.
[0136]
27 and 28 are diagrams for explaining the key direction of the connector attached to the PMF. Reference numeral 905 denotes a key of the connector 5 attached to the PMF 21, and 901 denotes a key groove provided in the adapter 53 of the extinction ratio measuring device main body 51 of the present invention to which the connector 5 is attached. The connector 5 is attached to the adapter 53 so that the key 905 enters the key groove 901, whereby the positional relationship between the key direction of the connector 5 and the key groove direction of the adapter 53 is maintained.
[0137]
The rotation reference direction of the polarization separation element is a reference direction when measuring the incident light by rotating the polarization separation element, and can be, for example, the direction of the key groove of the optical adapter. Note that only one of the key and keyway may be attached to the connector and adapter, and in the reverse manner, the keyway may be attached to the connector and the adapter may be attached to the key. It is also possible to add both the key groove and the key groove, and it is clear from the above description that the present invention exerts a great effect in either case.
[0138]
The embodiments of the present invention have been described above. However, the present invention is not limited to the embodiments described above, and many variations can be made by utilizing the technical idea of the present invention. is there.
[0139]
For example, the disturbance given to the optical fiber as the object to be measured is changed stepwise using a step motor instead of continuous, the modulation signal is superimposed on the disturbance, and the measurement control system is controlled by a computer. Variations are possible.
[0140]
【The invention's effect】
As explained above, according to the present invention, when PER changes under various physical conditions like PMF, accurate PER measurement that could not be performed at all can be performed accurately and extremely easily. The angle between the incident light and the PMF intrinsic polarization axis of the object to be measured, the angle between the intrinsic polarization axis of the PMF of the object to be measured and the polarization separation axis of the polarization separation element, the intrinsic polarization axis of the PMF of the object to be measured It is possible to measure the misalignment angle in the key direction of the connector attached to it.
[0141]
Furthermore, restrictions on the light source can be greatly relaxed.
[0142]
  By applying the present invention to, for example, a manufacturing process of a laser diode module to which a PMF is attached, conventionally, a pass product is determined to be a fail product,BadAccepted productTogetherThe reliability of the inspection process that has been determined to be a high-quality product can be made extremely high, the quality of the product can be improved at each stage, and the manufacturing cost can be greatly reduced.
[0143]
As described above, the present invention exhibits a great industrial effect.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an outline of a measuring apparatus for polarization extinction ratio and the like according to the present invention.
FIG. 2 is a diagram for explaining the outline of a measuring apparatus such as a polarization extinction ratio according to the present invention.
FIG. 3 is a diagram illustrating a polarization mode.
FIG. 4 is a diagram illustrating an example of a disturbance adding unit according to the present invention.
FIG. 5 is a diagram illustrating an example of a tension applying unit according to the present invention.
FIG. 6 is a plan view of an example of a linear motion guide used in the tension applying unit of the present invention.
FIG. 7 is a cross-sectional view of an example of a linear motion guide used in the tension applying unit of the present invention.
FIG. 8 is a diagram illustrating an example of a disturbance adding unit according to the present invention.
FIG. 9 is a diagram illustrating an example of an extinction ratio measuring device main body according to the present invention.
FIG. 10 is a diagram for explaining the angle-dependent characteristics of PER in the measurement method of the present invention.
FIG. 11 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 12 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 13 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 14 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 15 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 16 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 17 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 18 is an example of PER-angle dependence characteristics by the measurement method of the present invention.
FIG. 19 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 20 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 21 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 22 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 23 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 24 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 25 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 26 is a measurement example of PER and the like by the measurement method of the present invention.
FIG. 27 is a diagram for explaining a key direction of a connector.
FIG. 28 is a diagram for explaining a key direction of a connector.
FIG. 29 is a diagram for explaining a conventional typical PER measurement method.
FIG. 30 is a diagram for explaining a conventional PER measurement apparatus proposed as an improvement of a conventional typical PER measurement method.
FIG. 31 is a diagram for explaining a conventional PER measurement apparatus proposed as an improvement of a conventional typical PER measurement method.
FIG. 32 is a diagram for explaining a conventional PER measurement apparatus proposed as an improvement of a conventional typical PER measurement method.
FIG. 33 is a diagram for explaining a conventional PER measurement apparatus proposed as an improvement of a conventional typical PER measurement method.
[Explanation of symbols]
1: coherent probe light,
2, 21, 203: PMF,
3: Exciter
4, 5: Connector
6: Detection unit
7: Polarization separation element
8: Output light power of the polarization component that vibrates in the direction orthogonal to the polarization separation axis
9: Output light power of the polarization component oscillating in a direction parallel to the polarization separation axis
10: PER calculator
11: Laser diode module
22: Disturbance addition part
23: Support stand
24: Fiber clamp
25: Prop
26: Tension applying part
27: Stopper
28: LM Guide
29: Tension applying plate
30 and 31: Spring fixing column
32: Spring
33: Motor
34: The portion of the tension applying plate 29 protruding above the support base 23 in FIG.
35, 36, 44, 45, 46, 47, 206, 207, 352 arrows
37: End
38: Center of rotation 38
39: Rotating plate
40: Linear motion (LM) rail
41: LM block
42, 43: convex portion
50: Connection line
51: Extinction ratio measuring instrument body
52: Main part of the detector
53: Optical adapter
54: Polarization separation element
55, 56: Photodiode
57: Arithmetic circuit
60, 61: PER-angle curve
62, 63: Maximum value
64: Intersection
96,99,130,134,121,124,140,144,530,511,173,172,191,194,501,504,603,606,610,613,620,623,720,731,770, 781,820,831: Upper line
98, 97, 132, 131, 123, 122, 143, 141, 510, 531, 171, 174, 193, 192, 503, 502, 604, 605, 611, 612, 621, 622, 721, 730, 771, 780, 821, 830: Lower line
111, 136, 137, 125, 126, 145, 146, 167, 185, 186, 195, 196, 515, 516, 607, 608, 614, 615, 624, 625, 740, 750, 790, 800, 840, 850: Maximum value of upper line
112, 135, 127, 147, 168, 187, 197, 517: Maximum value of each lower line
201: Light source
202: Polarizer
204: Analyzer
205: Light receiver
301: Aluminum holding plate
325: Movable optical fiber gripping part
326: Fixed optical fiber gripping part
302: Clamp member
303: Elastic member
304: Base
305: Stopper
306: Slide guide
321: Groove with rectangular cross section
307: Optical fiber connector harness
309: Optical connector
310: Detector
351: Movable optical fiber gripping part sliding stop part
601,700: extinction ratio-angle characteristic curve
602, 710: Maximum value of extinction ratio-angle characteristic curve
609,616,626,760,810,860: intersection of two extinction ratio-angle characteristic curves
901: Adapter groove
905: Connector key
a, b: Angle
x-axis: intrinsic polarization axis
y-axis: An axis perpendicular to the x-axis

Claims (34)

Optical powers P (1) and P (2) of polarization modes orthogonal to each other as the amount of optical power when coherent light is incident on and output from an optical fiber that is an object to be measured or an optical device having an optical fiber, and those In the polarization extinction ratio measuring apparatus for measuring the polarization extinction ratio PER = 10 log (P (1) / P (2)) as a ratio of
The optical fiber is a polarization maintaining optical fiber (hereinafter also referred to as “PMF”).
A disturbance adding unit that applies a disturbance to a part of the optical fiber, the phase difference between the intrinsic polarization modes of the optical fiber being continuously and periodically changed between at least 0 to 2π radians;
The optical powers P (1) and P (1) when the disturbance adding unit applies a disturbance that changes a phase difference between the intrinsic polarization modes of the optical fiber over at least 0 to 2π radians on a part of the optical fiber. 2) and a detection unit that measures the polarization extinction ratio PER, and the detection unit guides the outgoing light that is output by causing the coherent light to be incident on the optical fiber that is the object to be measured or the optical device having the optical fiber. An angle formed by the polarization axis of the PMF and the polarization direction of incident light incident on the PMF, and the polarization axis of the polarization axis of the PMF that is the object to be measured and the polarization of the polarization separation element The amount of fluctuation of the optical powers P (1) and P (2) when either or both of the angles formed with the separation axis is changed is minimized, and the measurement range The object to be measured is obtained by finding the point where the minimum value of the polarization extinction ratio PER as the ratio of the optical powers P (1) and P (2) corresponding to each value of the powers P (1) and P (2) is maximized An apparatus for measuring a polarization extinction ratio, wherein The apparatus for measuring a polarization extinction ratio according to claim 1,
The apparatus for measuring a polarization extinction ratio, wherein the disturbance adding unit gives a disturbance so that the phase difference changes in a stepwise manner. In the measuring apparatus of polarization extinction ratio according to claim 1 or claim 2,
The apparatus for measuring a polarization extinction ratio, wherein the disturbance adding unit applies disturbance by periodically vibrating the optical fiber using a step motor. In the measuring apparatus of polarization extinction ratio of any one of Claims 1-3,
The disturbance adding unit gives a disturbance capable of continuously and periodically changing a phase difference between natural polarization modes of the optical fiber over a range of at least 0 to 2π radians on a part of the optical fiber,
The detection unit includes a polarization separation element that guides outgoing light that is output by causing coherent light to enter and output to the optical fiber or an optical device including the optical fiber, and incident light incident on the intrinsic polarization axis of the PMF and the PMF. The optical powers P (1) and P (1) when one of the angle between the polarization direction and the angle between the intrinsic polarization axis of the PMF and the polarization separation axis of the polarization separation element is fixed and the other is changed. 2) The amount of variation is minimized, and the minimum value of the ratio of the optical powers P (1) and P (2) corresponding to each value of the optical powers P (1) and P (2) in the measurement target range An apparatus for measuring the polarization extinction ratio, wherein the PER is obtained by obtaining the point where the maximum value is obtained. In the measuring apparatus of polarization extinction ratio of any one of Claims 1-4,
An angle formed between the intrinsic polarization axis of the PMF and the polarization direction of incident light incident on the PMF is an angle a (unit: radians), and an angle formed between the intrinsic polarization axis of the PMF and the polarization separation axis of the polarization separation element. Is the angle b (unit: radians), and τ (unit: radians) is the phase difference between the intrinsic polarization modes of the PMF generated in the PMF by perturbing the PMF by the perturbation adding unit.
The detection unit includes the following (Equation 1) and (Equation 2), that is,

The polarization extinction ratio PER calculated using the optical powers P (1) and P (2) given by is varied with the other of the angle a and the angle b being a constant value. The phase difference τ at each value of the angle a and the angle b to be changed is measured while being changed by the disturbance given to the PMF by the disturbance adding unit, and the polarization extinction ratio PER is plotted on the vertical axis. The angle a for measuring the polarization extinction ratio PER, which is a first polarization extinction ratio PER-angle curve, taking the variable axis of the angle a and the angle b as the horizontal axis orthogonal to the vertical axis. The polarization extinction ratio PER-angle a or angle b curve and the second polarization extinction ratio PER-angle curve when the phase difference τ at each value of the angle b to be varied is set to 0. Measure polarization extinction ratio PER The polarization extinction ratio PER−angle a or angle b curve when the phase difference τ at each value of the angle a to be varied between the angle a and the angle b to be determined is π, and the first polarization An apparatus for measuring a polarization extinction ratio, wherein the PER of the object to be measured is calculated from an intersection of an extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve. The apparatus for measuring a polarization extinction ratio according to claim 5,
The detecting unit varies the angle b when the angle a is an unknown constant value, and gives the disturbance to the polarization extinction ratio PMF at each value of the angle b by the disturbance adding unit. The phase difference τ in the PMF is continuously and periodically changed between at least 0 to 2π radians to obtain the first polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve, Each angle b giving a peak value of the first polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve, and the first polarization extinction ratio PER-angle curve and the second polarization The angle between the polarization direction of incident light incident on the polarization extinction ratio PMF and the intrinsic polarization axis of the PMF is determined from the value of the angle b when the extinction ratio PER-angle curve intersects. A device for measuring the polarization extinction ratio. The apparatus for measuring a polarization extinction ratio according to claim 5,
The angle b is varied, the disturbance is given to the PMF at each value of the angle b, and the phase difference τ in the PMF is changed continuously and periodically over at least 0 to 2π radians to change the first b The polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve are obtained, and the first polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve intersect. A polarization extinction ratio measuring apparatus, wherein an angle formed between a characteristic polarization axis of the PMF of the object to be measured and a rotation reference direction of the polarization separation axis of the polarization separation element is obtained from the value of the angle b. The apparatus for measuring a polarization extinction ratio according to claim 5,
The angle b is varied with the angle b set to a constant value, the disturbance is given to the PMF at each value of the angle a, and the phase difference τ in the PMF is continuously varied between at least 0 to 2π radians and An apparatus for measuring a polarization extinction ratio, characterized by measuring the polarization extinction ratio PER when it is periodically changed to obtain a maximum value and a minimum value of the polarization extinction ratio PER at each value of the angle a. In the measuring apparatus of polarization extinction ratio according to claim 1 or claim 2,
The detection unit uses an angle a (unit: radians) as an angle formed between the unique polarization axis of the PMF and the polarization direction of incident light incident on the PMF, and separates the polarization of the PMF from the polarization separation element. An angle formed with the axis is an angle b (unit: radians), and a phase difference between eigenpolarization modes of the PMF generated in the PMF by applying disturbance to the PMF by the disturbance adding unit is τ (unit: radians). When doing the following (Formula 3) and (Formula 4),

The polarization extinction ratio PER calculated using the optical powers P (1) and P (2) given by is varied with the other of the angle a and the angle b being a constant value. The phase difference τ at each value of the angle a and the angle b to be changed is changed continuously and periodically over at least 0 to 2π by the disturbance given to the PMF by the disturbance adding unit. The polarization extinction ratio PER is taken on the vertical axis, the angle of the angle a and the angle b to be changed is taken on the horizontal axis perpendicular to the vertical axis, and the angle a and the angle b measured as described above are taken. The distribution of the value of the polarization extinction ratio PER at each value of the phase difference τ varied between at least 0 and 2π at the angle of variation among the graphs, and the angle a in the graph Corner b, the amount of fluctuation of the polarization extinction ratio PER based on the change of the phase difference τ at each value of the angle to be varied is minimized, and the angle of the angle a and the angle b to be varied is changed. A polarization extinction ratio characterized in that a value of the polarization extinction ratio PER that maximizes a minimum value of the polarization extinction ratio PER that changes based on a change in the phase difference τ at each value is obtained as the PER of the object to be measured. Measuring device. The apparatus for measuring a polarization extinction ratio according to claim 9,
The detection unit varies the angle b when the angle a is an unknown constant value, and gives a disturbance to the PMF by the disturbance adding unit at each value of the angle b to thereby change the position in the PMF. A distribution of values of the polarization extinction ratio PER measured by changing the phase difference τ continuously and periodically over at least 0 to 2π radians is shown in a graph, and the polarization extinction ratio PER at each value of the angle b in the graph. The angle b at which the maximum value of the angle b is maximized, and the polarization direction of the incident light incident on the PMF from the value of the angle b at which the minimum value of the polarization extinction ratio PER at each value of the angle b is maximized An apparatus for measuring a polarization extinction ratio, wherein an angle formed between the PMF and an intrinsic polarization axis is obtained. The apparatus for measuring a polarization extinction ratio according to claim 9,
The detection unit varies the angle b regardless of the value of the angle a, and gives disturbance to the PMF by the disturbance adding unit at each value of the angle b so that the phase difference τ in the PMF is at least 0 to 0. The distribution of the value of the polarization extinction ratio PER measured continuously and periodically over 2π radians is represented in a graph, and the minimum value of the polarization extinction ratio PER at each value of the angle b in the graph An apparatus for measuring the polarization extinction ratio, wherein an angle formed between the intrinsic polarization axis of the PMF and the rotation reference direction of the polarization separation axis of the polarization separation element is obtained from the value of the angle b at which is maximized. The apparatus for measuring a polarization extinction ratio according to claim 9,
The detection unit varies the angle b regardless of the value of the angle a, and gives disturbance to the PMF by the disturbance adding unit at each value of the angle b so that the phase difference τ in the PMF is at least 0 to 0. The distribution of the value of the polarization extinction ratio PER measured continuously and periodically over 2π radians is represented in a graph, and the minimum value of the polarization extinction ratio PER at each value of the angle b in the graph From the value of the angle b at which the PMF becomes the maximum, the angle between the intrinsic polarization axis of the PMF and the key direction of the connector of the PMF or the angle between the intrinsic polarization axis of the PMF and the key groove direction of the adapter for attaching the connector of the PMF An apparatus for measuring a polarization extinction ratio. The apparatus for measuring a polarization extinction ratio according to claim 9,
The detection unit varies the angle a with the angle b set to a constant value, and the disturbance adding unit perturbs the PMF at each value of the angle a so that the phase difference τ in the PMF is at least 0. Measure the polarization extinction ratio PER when it is continuously and periodically changed over 2π radians, and determine the maximum and minimum values of the polarization extinction ratio PER at each value of the angle a. An apparatus for measuring the polarization extinction ratio. The apparatus for measuring a polarization extinction ratio according to any one of claims 1 to 13,
The optical power P (1) is a polarization mode optical power that vibrates in a direction parallel to the polarization separation axis of the polarization separation element, and the optical power P (2) is orthogonal to the polarization separation axis of the polarization separation element. An apparatus for measuring a polarization extinction ratio, characterized in that the optical power is a polarization mode oscillating in a direction. In the measuring apparatus of polarization extinction ratio of any one of Claims 1-14,
The apparatus for measuring a polarization extinction ratio, wherein the disturbance adding unit includes a vibrating unit that vibrates the optical fiber from a side surface direction of the optical fiber. The apparatus for measuring a polarization extinction ratio according to claim 15,
The optical fiber is fixed and held by at least two fixing portions at a predetermined interval on both sides of the portion to be disturbed by the disturbance adding portion,
The disturbance given to the optical fiber by the disturbance adding part is a disturbance given as vibration from the outside of the optical fiber to a portion between the two fixed parts of the optical fiber. measuring device. The polarization extinction ratio measuring device according to claim 16,
The disturbance given to the optical fiber by the disturbance adding part is a disturbance given as vibration from the outside of the optical fiber so as to bend a portion between two fixed parts of the optical fiber. Measuring device for polarization extinction ratio. The polarization extinction ratio measuring device according to claim 17,
The disturbance given to the optical fiber by the disturbance adding portion is periodically displaced in a direction intersecting the length direction of the optical fiber at a portion between two fixed portions of the optical fiber. The apparatus for measuring the polarization extinction ratio is a disturbance given as vibration from the outside of the optical fiber so as to periodically deflect the portion between the two fixed parts. The polarization extinction ratio measuring apparatus according to claim 18,
Disturbances that are periodically displaced in a direction that intersects the length of the optical fiber cause the phase difference between the intrinsic polarization modes of the optical fiber to change continuously and periodically over at least 0-2π radians. In the entire process of applying disturbance to the optical fiber, the optical fiber is periodically bent in the same direction that intersects the length direction of the optical fiber at a portion between the two fixed portions of the optical fiber. A device for measuring polarization extinction ratio, characterized by disturbance. Coherent light is incident on a polarization-maintaining optical fiber, which is an object to be measured, and the output light is guided to a polarization separation element. A method for measuring a polarization extinction ratio for measuring an extinction ratio PER = 10 log (P (1) / P (2)),
Imparting a disturbance to a portion of the optical fiber such that the phase difference between the intrinsic polarization modes of the optical fiber can be continuously and periodically changed between at least 0 to 2π radians;
The angle related to the angle when the angle formed between the intrinsic polarization axis of the PMF and the polarization direction of incident light incident on the PMF or the angle formed between the intrinsic polarization axis of the PMF and the polarization separation axis of the polarization separation element is changed. Obtaining the PER of the object to be measured by obtaining the place where the amount of fluctuation of the polarization extinction ratio PER is minimized and the minimum value of the polarization extinction ratio PER corresponding to each value in the measurement target range is maximized. A characteristic method for measuring the polarization extinction ratio. The method of measuring a polarization extinction ratio according to claim 20,
The optical fiber is a polarization maintaining optical fiber (hereinafter also referred to as “PMF”),
Any of the angle formed between the intrinsic polarization axis of the PMF and the polarization direction of the incident light incident on the PMF, and the angle formed between the intrinsic polarization axis of the PMF as the object to be measured and the polarization separation axis of the polarization separation element Where the amount of fluctuation of the polarization extinction ratio PER with respect to the angle when one or both of them are changed is minimized, and the minimum value of the polarization extinction ratio PER corresponding to each value in the measurement target range is maximized And determining the PER of the object to be measured. In the method for measuring the polarization extinction ratio according to claim 20 or claim 21,
A method for measuring a polarization extinction ratio, wherein the disturbance is applied so that the phase difference changes stepwise. Claim 21 is the method of measuring the polarization extinction ratio according to claim 22,
The optical power P (1) is a polarization mode optical power that vibrates in a direction parallel to the polarization separation axis of the polarization separation element, and the optical power P (2) is orthogonal to the polarization separation axis of the polarization separation element. A method for measuring a polarization extinction ratio, characterized in that the optical power is a polarization mode oscillating in a direction. The method for measuring a polarization extinction ratio according to any one of claims 21 to 23,
One of an angle formed between the intrinsic polarization axis of the PMF and the polarization direction of incident light incident on the PMF and an angle formed between the intrinsic polarization axis of the PMF as a measurement object and the polarization separation axis of the polarization separation element are fixed. Then, the other is changed, and the PER of the object to be measured is obtained. The method for measuring a polarization extinction ratio according to any one of claims 21 to 24,
While measuring the PER of the object to be measured, the angle between the polarization direction of the PMF and the polarization direction of the incident linearly polarized light incident on the PMF, and the rotation reference of the polarization axis of the polarization separation element and the polarization direction of the polarization separation element. A method for measuring a polarization extinction ratio, wherein at least one of angles formed with a direction is measured simultaneously with the measurement of the PER. The method for measuring a polarization extinction ratio according to any one of claims 21 to 25,
An angle formed by the polarization axis of the incident light incident on the PMF and the polarization direction of the incident light entering the PMF is an angle a (unit: radians), and the polarization separation of the polarization axis of the PMF and the polarization separation element is performed. An angle formed with the axis is an angle b (unit: radians), and a phase difference between eigenpolarization modes of the PMF generated in the PMF by giving a disturbance to the PMF that is a measurement object is τ (unit: radians). When doing the following (Formula 5) and (Formula 6), that is,

The polarization extinction ratio PER calculated using the optical powers P (1) and P (2) given by is varied with the other of the angle a and the angle b being a constant value. , The phase difference τ at each value of the angle a and the angle b to be changed is measured while being changed by disturbance applied to the PMF, the polarization extinction ratio PER is taken on the vertical axis, and the angle a and The variable b of the angle b is taken as the horizontal axis orthogonal to the vertical axis, and the polarization extinction ratio PER, which is a first polarization extinction ratio PER-angle curve, is measured. Polarization extinction ratio PER-angle a or angle b curve when the phase difference τ at each value of the angle to be changed is 0, and the polarization extinction ratio PER, which is the second polarization extinction ratio PER-angle curve, The angle a to be measured And the polarization extinction ratio PER−angle a or angle b curve when the phase difference τ at each value of the angle to be varied is set to π, and the first polarization extinction ratio PER−angle. A method of measuring a polarization extinction ratio, comprising calculating PER of an object to be measured from an intersection of a curve and the second polarization extinction ratio PER-angle curve. The method of measuring a polarization extinction ratio according to claim 26,
When the angle a is an unknown constant value, the angle b is varied, the disturbance is given to the PMF at each value of the angle b, and the phase difference τ in the PMF is set to at least 0 to 2π radians. The first polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve are obtained by continuously and periodically changing between them, and the first polarization extinction ratio PER-angle curve and the above-mentioned An angle b that gives a peak value of a second polarization extinction ratio PER-angle curve, and an angle b when the first polarization extinction ratio PER-angle curve intersects the second polarization extinction ratio PER-angle curve A method of measuring a polarization extinction ratio, wherein an angle formed between a polarization direction of incident light incident on the PMF of the object to be measured and an intrinsic polarization axis of the PMF is obtained from the value of. The method of measuring a polarization extinction ratio according to claim 26,
The angle b is varied, the disturbance is given to the PMF at each value of the angle b, and the phase difference τ in the PMF is changed continuously and periodically over at least 0 to 2π radians to change the first b The polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve are obtained, and the first polarization extinction ratio PER-angle curve and the second polarization extinction ratio PER-angle curve intersect. A method for measuring a polarization extinction ratio, wherein an angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the rotation reference direction of the polarization separation axis of the polarization separation element is obtained from the value of the angle b. The method of measuring a polarization extinction ratio according to claim 26,
The angle b is varied by setting the angle b to a constant value, and the disturbance is given to the optical fiber at each value of the angle a so that the phase difference τ in the optical fiber is continuously at least between 0 and 2π radians. A method for measuring a polarization extinction ratio, comprising measuring a minimum value of a polarization extinction ratio PER value that is changed by changing periodically and periodically. The polarization extinction ratio measurement method according to any one of claims 22 to 25, wherein the measurement method includes an intrinsic polarization axis of the PMF that is an object to be measured and a polarization direction of incident light incident on the PMF. Is the angle a (unit: radians), and the angle between the intrinsic polarization axis of the PMF being the object to be measured and the polarization separation axis of the polarization separation element is the angle b (unit: radians). When the phase difference between eigenpolarization modes of the PMF generated in the PMF by giving a disturbance to the PMF that is an object is τ (unit: radians), the following (Equation 7) and (Equation 8):

The polarization extinction ratio PER calculated using the optical powers P (1) and P (2) given by is varied with the other of the angle a and the angle b being a constant value. , Measured by continuously and periodically changing the phase difference τ at each value of the angle a and the angle b between the angle a and the angle b over a range of at least 0 to 2π by a disturbance applied to the polarization extinction ratio PMF. The polarization extinction ratio PER is taken on the vertical axis, and the changing angle of the angle a and the angle b is taken on the horizontal axis orthogonal to the vertical axis, and the angle a and the angle b measured as described above The distribution of the value of the polarization extinction ratio PER at each value of the phase difference τ continuously and periodically changed over at least 0 to 2π in the angle of the fluctuation of Corner The amount of fluctuation of the polarization extinction ratio PER based on the change of the phase difference τ at each value of the angle a and the angle b to be changed is minimized, and the angle a and the angle b to be changed is changed. A polarization extinction ratio characterized in that the value of the polarization extinction ratio PER that maximizes the minimum value of the polarization extinction ratio PER that changes based on the change in the phase difference τ at each angle value is obtained as the PER of the object to be measured. Measuring method. The method of measuring a polarization extinction ratio according to claim 30,
When the angle a is an unknown constant value, the angle b is varied, the PMF is disturbed at each value of the angle b, and the phase difference τ in the PMF is at least between 0 and 2π radians. In the graph showing the distribution of PER values measured continuously and periodically over the angle b, the angle b at which the maximum value of the polarization extinction ratio PER at each value of the angle b is maximized, and the angle b The angle between the polarization direction of the incident light incident on the PMF of the object to be measured and the intrinsic polarization axis of the PMF is obtained from the value of the angle b at which the minimum value of the polarization extinction ratio PER is maximized. A method for measuring the polarization extinction ratio. The method of measuring a polarization extinction ratio according to claim 30,
Regardless of the value of the angle a, the angle b is fluctuated, the disturbance is given to the PMF at each value of the angle b, and the phase difference τ in the PMF is continuously and periodically between 0 and 2π radians. In the graph showing the distribution of values of the polarization extinction ratio PER measured by varying the angle, the value of the angle b at which the minimum value of the polarization extinction ratio PER at each value of the angle b is maximized is measured. A method for measuring a polarization extinction ratio, characterized in that an angle formed between a natural polarization axis of a PMF of an object and a rotation reference direction of a polarization separation axis of the polarization separation element can be obtained. The method of measuring a polarization extinction ratio according to claim 30,
Regardless of the value of the angle a, the angle b is varied, the disturbance is given to the PMF at each value of the angle b, and the phase difference τ in the PMF is continuously and periodically between 0 and 2π radians. In the graph showing the distribution of values of the polarization extinction ratio PER measured by varying the angle, the value of the angle b at which the minimum value of the polarization extinction ratio PER at each value of the angle b is maximized is measured. An angle formed between the intrinsic polarization axis of the PMF of the object and the key direction of the PMF connector or an angle formed between the intrinsic polarization axis of the PMF of the object to be measured and the key groove direction of the adapter to which the PMF connector is attached is obtained. Measuring method of polarization extinction ratio. The method of measuring a polarization extinction ratio according to claim 30,
The angle b is varied with the angle b set to a constant value, the disturbance is given to the PMF at each value of the angle a, and the phase difference τ in the PMF is continuously varied between at least 0 to 2π radians and A method for measuring a polarization extinction ratio, comprising measuring the polarization extinction ratio PER when it is periodically changed, and obtaining a maximum value and a minimum value of the polarization extinction ratio PER at each value of the angle a.

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