JP2004264368A

JP2004264368A - Reflective optical device

Info

Publication number: JP2004264368A
Application number: JP2003043261A
Authority: JP
Inventors: Hiroaki Ono; 博章小野; Shohei Abe; 昇平阿部; Hideo Takeshita; 秀生竹下; Hideaki Wada; 秀亮和田; Mototsugu Goto; 元次後藤; Yuko Ota; 猶子大田
Original assignee: FDK Corp
Current assignee: FDK Corp
Priority date: 2003-02-20
Filing date: 2003-02-20
Publication date: 2004-09-24
Also published as: WO2004074923A1

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a reflective optical device small in the number of components, high in motion reliable, capable of being downsized at a low cost and having a 2×2 type optical switch function or a completely cyclical 4-port optical circulator function. <P>SOLUTION: A polarization separating and synthesizing double refraction means 10, a polarization rotating means 12, first and second optical path controlling double refraction means 16, 20 and a polarization rotating and reflecting means 22 (or an optical path changing and reflecting means) are aligned along an optical axis in this order. First and second linear phase elements 14, 18 are respectively inserted between the polarization rotating means and the first optical path controlling birefringence means and between the first and second optical path controlling birefringence means. A light incident and outgoing part comprising four or more aligned optical fibers is positioned on the side opposite to the polarization rotating and reflecting means. The polarization rotating means consists of ±45° variable Faraday rotator 26 and a left-to-right pair of half-wave plates 27a, 27b. The device yields the optical switch function by changing polarizing directions. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ファラデー回転子を用いて偏光方向を制御すると共に複屈折手段を用いて光路シフトを制御する反射型の光デバイスに関し、±４５度可変ファラデー回転子によって光スイッチ機能を実現したり、あるいは４５度固定ファラデー回転子によって光サーキュレータ機能を実現するようにした反射型光デバイスに関するものである。
【０００２】
【従来の技術】
【特許文献１】
特開２０００−３９５９０号公報
【０００３】
光通信システムあるいは光計測システムなどにおいては、光路の切り換えを行うための光スイッチや光路を制御するための光サーキュレータなどの光デバイスが組み込まれている。光スイッチは、入力ポートからの入力光を、出力ポートの選択された任意の一つに出力するというような光路切り換え機能を有する光デバイスであり、１×２型（１入力・２出力）が最も基本的な形態である。光サーキュレータは、第１ポートからの入力光を第２ポートへ出力し、第２ポートからの入力光を第３ポートに出力するというように光路を循環的に制御する機能を有する光デバイスであり、３ポート型が最も基本的な形態である。
【０００４】
特に光通信用の光デバイスとしては、偏波無依存であること、光ファイバとの整合性が良好なこと、信頼性が高いことなどが肝要である。そのような要求を満たしうるものとして、例えば偏波面に応じて光路を制御する複屈折結晶と偏波面の回転角を制御するファラデー回転子などの各種光素子を組み合わせ配列した光素子群によって必要な光機能部を実現する構成がある。
【０００５】
この種の光デバイスでは、かつては光素子群の一端側から光が入力し、光素子群を一方向に進行して、他端側から出力する構造（言わば透過型）が一般的であった。しかし近年、光デバイスの小型化などの観点から、配列されている光素子群と反射手段（ミラー）を組み合わせ、一端側から入力する光が光素子群を進行してミラーに達し、該ミラーで反射した光が光素子群を逆行して一端側から出力するようにし、光が光素子群を往復する間、光路の切り換えや制御を行う反射型の光デバイスが開発されている。例えば特許文献１には、複屈折結晶、４５度ファラデー回転子、１／２波長板、複屈折結晶を一列に配列し、更にその列の一端に入出射部を設け、他端に偏波回転素子と反射体を配置した反射型光サーキュレータが開示されている。
【０００６】
【発明が解決しようとする課題】
このような反射型の光デバイスは、光が光素子群を往復する間に必要な機能をもたせることができるため、部品点数を削減でき、光軸方向の長さを大幅に短縮できる利点を有する。しかし、従来の反射型光デバイスは機能面で制約があり用途が限られている。
【０００７】
前記特許文献１で開示されている構成の反射型光サーキュレータは、確かにサーキュレータ機能を呈するものの不完全な循環型である。例えば３ポート型の場合、第１ポートからの入力光は第２ポートに出力し、第２ポートからの入力光は第３ポートに出力するが、第３ポートからの入力光は第１ポートには出力できない。４ポート以上の形式の場合でも、最終ポートからの入力光は第１ポートには出力できない。
【０００８】
上記の反射型光サーキュレータの構造を利用し、ファラデー回転子を固定磁界印加方式から可変磁界印加方式に置き換えて±４５度可変ファラデー回転子にすると、スイッチ機能が得られる。しかし、１×２型（１入力・２出力）又は２×１型（２入力・１出力）であり、２×２型（２入力・２出力）は得られない。
【０００９】
本発明の目的は、２×２型の光スイッチ機能を呈する反射型光デバイスを提供することである。本発明の他の目的は、完全な循環型の４ポート光サーキュレータ機能を呈する反射型光デバイスを提供することである。本発明の更に他の目的は、部品点数が少なく、動作の信頼性が高く、安価にでき、小型化できる反射型光デバイスを提供することである。
【００１０】
【課題を解決するための手段】
本発明は、偏波方向が直交関係にある同じ光路の光を分離し異なる光路の光を合成する偏波分離合成用複屈折手段と、異なる光路の光の偏波方向を直交から平行又は平行から直交の関係に変換する偏波回転手段と、偏波方向に応じて光路シフトを制御する第１及び第２の光路制御用複屈折手段と、偏波面を往復で９０度回転させて反射する偏波回転反射手段又は往復の光路を変更して反射する光路変更反射手段とを、その順序で光軸に沿って配列し、
偏波回転手段と第１の光路制御用複屈折手段の間に一部の光路の光の偏波方向を９０度回転する第１の直線位相子が、また第１の光路制御用複屈折手段と第２の光路制御用複屈折手段の間に他の一部の光路の光の偏波方向を９０度回転する第２の直線位相子がそれぞれ挿入され、
偏波回転反射手段又は光路変更反射手段とは反対側に位置する入出射部には４本以上の光ファイバが配列されており、
前記偏波回転手段は、±４５度可変ファラデー回転子と一対の１／２波長板の組み合わせからなり、偏波方向を切り換えることで光スイッチ機能を呈することを特徴とする反射型光デバイスである。
【００１１】
また本発明は、偏波方向が直交関係にある同じ光路の光を分離し異なる光路の光を合成する偏波分離合成用複屈折手段と、異なる光路の光の偏波方向を直交から平行又は平行から直交の関係に変換する偏波回転手段と、偏波方向に応じて光路シフトを制御する第１及び第２の光路制御用複屈折手段と、偏波面を往復で９０度回転させて反射する偏波回転反射手段又は往復の光路を変更して反射する光路変更反射手段とを、その順序で光軸に沿って配列し、
偏波回転手段と第１の光路制御用複屈折手段の間に一部の光路の光の偏波方向を９０度回転する第１の直線位相子が、また第１の光路制御用複屈折手段と第２の光路制御用複屈折手段の間に他の一部の光路の光の偏波方向を９０度回転する第２の直線位相子がそれぞれ挿入され、
偏波回転反射手段又は光路変更反射手段とは反対側に位置する入出射部には４本以上の光ファイバが配列されており、
前記偏波回転手段は、４５度固定ファラデー回転子と一対の１／２波長板の組み合わせからなり、光サーキュレータ機能を呈することを特徴とする反射型光デバイスである。
【００１２】
こられの構成によって本発明に係る反射型光デバイスは、典型的には４本のファイバを用いた２×２型（２入力・２出力）光スイッチ、あるいは４ポート完全循環型の光サーキュレータとして動作することになる。
【００１３】
偏波回転反射手段は、例えば１／４波長板又は４５度固定ファラデー回転子からなる往復９０度偏波回転子と、平面反射体の組み合わせからなる構成とする。光路変更反射手段は、例えば２段階の反射で光路を切り換えるＶ型反射体からなる。この場合、Ｖ型反射体は、Ｖ型反射面が偏波分離合成用複屈折手段による分離方向と平行な向きに設置する。
【００１４】
偏波分離合成用複屈折手段は、偏波分離合成用複屈折結晶と偏波分散補償用複屈折結晶とからなり、偏波分離合成用複屈折結晶による偏波分散を偏波分散補償用複屈折結晶で補償する構成、あるいは偏波分離合成用複屈折結晶を２分割し、それらの間に１／２波長板を挿入して常光・異常光を入れ換えることにより偏波分散を補償する構造とする。
【００１５】
偏波回転反射手段としては、１／４波長板又は４５度固定ファラデー回転子からなる往復９０度偏波回転子と、２段階の反射で光路を切り換えるＶ型反射体であってもよい。この場合、Ｖ型反射体は、Ｖ型反射面が偏波分離合成用複屈折手段による分離方向と直交する向きに設置する。更に光路変更反射手段としては、２段階の反射で往復路の光路を切り換えると共に往復路で常光光路と異常光光路を入れ換える方錐状反射体を用いることもできる。これらの構成によれば、反射によって常光と異常光を入れ換えることができるために偏波分散を補償できる。従って、偏波分離合成用複屈折手段に上記のような複数の複屈折結晶を組み合わせを用いる必要が無くなり、構成がより一層簡素化される。
【００１６】
入出射部は、４本の光ファイバと、４芯フェルールと、各光路に共通の結合用レンズと、該結合用レンズからの斜め方向の出射光を光軸に平行に、光軸に平行な光を結合用レンズへの斜め方向の入射光にする光路補正素子からなる構成とする。あるいは、入出射部は、４本の光ファイバを並設したファイバアレイと、各ファイバアレイにそれぞれ対応してレンズ素子を配列したコリメータレンズアレイとで構成してもよい。
【００１７】
なおＶ型反射体は、Ｖ溝の内面に反射膜を形成した構成でもよいし、三角柱プリズムの外面に反射膜を形成した構成でもよい。方錐状反射体も、四角錐状（ピラミッド形状）の穴の内面に反射膜を形成した構成でもよいし、四角錐プリズムの外面に反射膜を形成した構成でもよい。いずれにしても、反射面が所定の角度と向きを有していればよく、反射面以外の多少の形状変更は自由である。
【００１８】
光スイッチとして機能させる光デバイスの場合、±４５度可変ファラデー回転子にはファラデー回転の方向を切り換える可変磁界を印加するために電磁石を使用する。その磁気ヨークに半硬質磁性材料を用いると、通電を停止しても磁化状態が自己保持されるため、省電力化を図ることができる。
【００１９】
本発明では、第１及び第２の光路制御用複屈折手段という２段階の光路シフト機構を組み込み、往復路の光路シフトを制御することで、特定のポートから入力する光を所望のポートに結合させているのである。
【００２０】
【実施例】
図１は本発明に係る反射型光スイッチの一実施例を示す説明図である。Ａは素子の配列構造と各位置での偏波状態を示しており、Ｂはその光路を示している。光スイッチ本体は、偏波分離合成用複屈折手段１０と、偏波回転手段１２と、第１の直線位相子１４と、第１の光路制御用複屈折手段１６と、第２の直線位相子１８と、第２の光路制御用複屈折手段２０と、偏波回転反射手段２２とを、その順序で光軸に沿って配列した構成である。説明を分かり易くするため、素子の配列方向（光軸）をｚ軸とし、該ｚ軸に直交する２軸をそれぞれｘ軸（横軸）、ｙ軸（縦軸）とする座標軸を設定する。また便宜的に、往路における光の進行方向を基準として、ｘ方向を右方向、ｙ方向を上方向と言い、光路については下から順に１段目、２段目、…、５段目と称する。また偏波の回転方向は、ｚ方向（往路における光の進行方向）を基準として反時計回りを＋側とする。
【００２１】
光は光軸に平行に入出射する。偏波分離合成用複屈折手段１０は、偏波方向が直交関係にある同じ光路の光を常光・異常光に分離し異なる光路の常光・異常光を合成するもので、光学軸がｘｚ面内でｚ軸から傾いている複屈折結晶２４からなる。なお、組み合わされている次の複屈折結晶２５は、複屈折結晶２４で生じる偏波分散を補償するためのものであり、光学軸がｙ軸に平行に設定され、常光・異常光が入れ替わることで光路長を補正している。偏波回転手段１２は、異なる光路の光の偏波方向を直交から平行又は平行から直交の関係に変換するものであり、±４５度可変ファラデー回転子２６と左右分割されている一対の１／２波長板２７ａ，２７ｂの組み合わせからなる。±４５度可変ファラデー回転子２６は、磁気光学結晶（例えばＢｉ置換希土類鉄ガーネットＬＰＥ膜）からなるファラデー素子と該ファラデー素子に外部から磁界を印加する電磁石を備え、該電磁石への通電電流の向きを切り換えることでファラデー回転角を＋４５度又は−４５度に切り換えることができる構造である。左側の１／２波長板２７ａは光学軸がｘｙ面内でｘ軸に対して＋２２．５度傾き、右側の１／２波長板２７ｂは光学軸がｘｙ面内でｘ軸に対して−２２．５度傾くように組み合わせたものである。第１の直線位相子１４は、２段目光路と４段目光路に配置された１／２波長板１４ａ，１４ｂ（いずれも光学軸はｘｙ面内でｘ軸に対して＋４５度傾いている）からなり、２段目光路と４段目光路の光の偏波方向を９０度回転する。第１の光路制御用複屈折手段１６は、偏波方向に応じて光路シフトを制御するもので、光学軸がｙｚ面内でｚ軸から傾いている複屈折結晶からなる。第２の直線位相子１８は、１段目光路と５段目光路に配置された１／２波長板１８ａ，１８ｂ（いずれも光学軸はｘｙ面内でｘ軸に対して＋４５度傾いている）からなり、１段目光路と５段目光路の光の偏波方向を９０度回転する。第２の光路制御用複屈折手段２０は、第１の光路制御用複屈折手段１６と同じもので、偏波方向に応じて光路シフトを制御するもので、光学軸がｙｚ面内でｚ軸から傾いている複屈折結晶からなる。偏波回転反射手段２２は、偏波面を往復で９０度回転させて反射するもので、１／４波長板２８と平面反射体２９の組み合わせからなる（１／４波長板に代えて４５度固定ファラデー回転子を用いることも可能である）。１／４波長板２８は、直線偏光を回転偏光に、あるいは回転偏光を直線偏光に変換する機能を有する。偏波回転手段１２における±４５度可変ファラデー回転子２６により偏波方向を＋４５度又は−４５度に切り換えることによって、この光デバイスは光スイッチ機能を呈する。
【００２２】
この反射型光スイッチの動作は次の通りである。まず、±４５度可変ファラデー回転子２６で偏波面に＋４５度ファラデー回転が生じるように、電磁石への通電電流を制御するものとする。
【００２３】
３段目左側の第１入力ポート（Ｉ１）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段１０（複屈折結晶２４）で常光は直進し、異常光は屈折して＋ｘ方向に光分離すると共に複屈折結晶２５で偏波分散が補償される。±４５度可変ファラデー回転子２６では偏波方向が＋４５度回転し、左右一対の１／２波長板２７ａ，２７ｂで両光の偏波方向が直交から平行（ｙ軸と平行）の関係に変換される。１／２波長板は、入力光の偏波面を光学軸に対して対称な方向に変換する性質を備えているからである。両光は第１の直線位相子１４をバイパスし、第１の光路制御用複屈折手段１６では異常光となるので上方向（＋ｙ方向）に屈折して４段目光路にシフトする。第２の直線位相子１８もバイパスし、第２の光路制御用複屈折手段２０でも異常光となるので上方向（＋ｙ方向）に屈折して５段目光路にシフトする。そして１／４波長板２８で円偏波になり、平面反射体２９に達する。
【００２４】
平面反射体２９による反射光は円偏波のままであるが、再び１／４波長板２８を通過することで直線偏光に戻る。しかし両光の偏波方向はｘ軸と平行となる。これら両光は、第２の光路制御用複屈折手段２０に対しては常光であるので光路はシフトせず、そのまま直進する。次に第２の直線位相子１８（１／２波長板１８ｂ）を通過することで偏波方向がｙ軸と平行になり、第１の光路制御用複屈折手段１６では異常光となるので下方向（−ｙ方向）に屈折して４段目光路にシフトする。両光は第１の直線位相子１４（１／２波長板１４ｂ）を通過することで偏波方向がｘ軸と平行になり、１／２波長板２７ａ，２７ｂで左側光路の光の偏波方向は＋４５度回転し、右側光路の光は−４５度回転する。そのため、両光は偏波方向が平行から直交の関係となる。そして±４５度可変ファラデー回転子２６でそれぞれ＋４５度回転する。両光は偏波分離合成用複屈折手段１０（複屈折結晶２４）で常光は直進し、異常光は−ｘ方向に屈折することで合成され、４段目左側の第１出力ポート（Ｏ１）に結合する。
【００２５】
２段目左側の第２入力ポート（Ｉ２）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段１０（複屈折２４）で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。±４５度可変ファラデー回転子２６では偏波方向が＋４５度回転し、左右一対の１／２波長板２７ａ，２７ｂで両光の偏波方向が直交から平行（ｙ軸と平行）の関係に変換される。両光は第１の直線位相子１４（１／２波長板１４ａ）を通過して偏波方向がｘ軸と平行になり、第１の光路制御用複屈折手段１６では常光となるため直進する。第２の直線位相子１８をバイパスし、第２の光路制御用複屈折手段２０でも常光となるため直進する。そして１／４波長板２８を通過することで円偏波になり、平面反射体２９に達する。
【００２６】
平面反射体２９による反射光は円偏波のままであるが、再び１／４波長板２８を通過することで直線偏光に戻る。しかし、偏波方向はｙ軸と平行となる。これら両光は、第２の光路制御用複屈折手段２０に対しては異常光であるので−ｙ方向に屈折して光路は１段目にシフトする。両光は第２の直線位相子１８（１／２波長板１８ａ）を通過することで偏波方向がｘ軸と平行になり、第１の光路制御用複屈折手段１６では常光であるため直進し、第１の直線位相子１４をバイパスする。両光は、１／２波長板２７ａ，２７ｂで左側光路の光は＋４５度回転し、右側光路の光は−４５度回転し、±４５度可変ファラデー回転子２６でそれぞれ＋４５度回転する。そのため、両光は偏波方向が平行から直交の関係となる。そして両光は偏波分離合成用複屈折手段１０（複屈折結晶２４）で常光は直進し、異常光は−ｘ方向に屈折することで合成され、１段目左側の第２出力ポート（Ｏ２）に結合する。
【００２７】
次に、±４５度可変ファラデー回転子２６で偏波面に−４５度ファラデー回転が生じるように、電磁石への通電電流を制御するものとする。
【００２８】
３段目左側の第１入力ポート（Ｉ１）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段１０で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。±４５度可変ファラデー回転子２６では偏波方向が−４５度回転し、左右一対の１／２波長板２７ａ，２７ｂで両光の偏波方向が直交から平行（ｘ軸と平行）の関係に変換される。両光は第１の直線位相子１４をバイパスし、第１の光路制御用複屈折手段１６では常光となるので直進し、第２の直線位相子１８もバイパスし、第２の光路制御用複屈折手段２０でも常光となるのでそのまま３段目光路を直進する。そして１／４波長板２８で円偏波になり、平面反射体２９に達し反射する。
【００２９】
反射光は円偏波のままであるが、再び１／４波長板２８を通過することで直線偏光に戻る。しかし、両光の偏波方向はｙ軸と平行となる。これら両光は、第２の光路制御用複屈折手段２０に対しては異常光であるので−ｙ方向に屈折して２段目光路にシフトする。次に第２の直線位相子１８をバイパスし、第１の光路制御用複屈折手段１６でも異常光となるので下方向（−ｙ方向）に屈折して１段目光路にシフトする。両光は第１の直線位相子１４をバイパスし、１／２波長板２７ａ，２７ｂで左側光路の光は＋４５度回転し、右側光路の光は−４５度回転する。そして±４５度可変ファラデー回転子２６でそれぞれ−４５度回転する。両光は偏波分離合成用複屈折手段１０で常光は直進し、異常光は−ｘ方向に屈折することで合成され、１段目左側の第２出力ポート（Ｏ２）に結合する。
【００３０】
２段目左側の第２入力ポート（Ｉ２）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段１０で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。±４５度可変ファラデー回転子２６では偏波方向が−４５度回転し、左右一対の１／２波長板２７ａ，２７ｂで両光の偏波方向が直交から平行（ｘ軸と平行）の関係に変換される。両光は第１の直線位相子１４（１／２波長板１４ａ）を通過して偏波方向がｙ軸と平行になり、第１の光路制御用複屈折手段１６では異常光となるため上方向（＋ｙ方向）に屈折して３段目光路にシフトする。第２の直線位相子１８をバイパスし、第２の光路制御用複屈折手段２０でも異常光となるため上方向（＋ｙ方向）に屈折して４段目光路にシフトする。そして１／４波長板２８で円偏波になり、平面反射体２９に達し反射する。
【００３１】
反射光は円偏波のままであるが、再び１／４波長板２８を通過することで直線偏光に戻る。しかし、偏波方向はｘ軸と平行となる。これら両光は、第２の光路制御用複屈折手段２０に対しては常光であるのでそのまま直進する。両光は第２の直線位相子１８をバイパスし、第１の光路制御用複屈折手段１６でも常光であるためそのまま４段目光路を直進し、第１の直線位相子１４（１／２波長板１４ｂ）を通過することで偏波方向がｙ軸と平行になる。両光は、１／２波長板２７ａ，２７ｂで左側光路の光は＋４５度回転し、右側光路の光は−４５度回転し、±４５度可変ファラデー回転子２６でそれぞれ−４５度回転する。そして両光は偏波分離合成用複屈折手段１０で常光は直進し、異常光は−ｘ方向に屈折することで合成され、４段目左側の第１出力ポート（Ｏ１）に結合する。
【００３２】
つまり、±４５度可変ファラデー回転子２６によりファラデー回転角を＋４５度に制御することによって、３段目左側の第１入力ポート（Ｉ１）から入射する光を４段目左側の第１出力ポート（Ｏ１）から出射させ、２段目左側の第２入力ポート（Ｉ２）から入射する光を１段目左側の第２出力ポート（Ｏ２）から出射させることができる。また、ファラデー回転角を−４５度に制御することによって、３段目左側の第１入力ポート（Ｉ１）から入射する光を１段目左側の第２出力ポート（Ｏ２）から出射させ、２段目左側の第２入力ポート（Ｉ２）から入射する光を４段目左側の第１出力ポート（Ｏ１）から出射させることができる。このようにして、２×２型（２入力・２出力）の反射型光スイッチが実現できる。
【００３３】
入出射部の例を図２及び図３に示す。図１から分かるように、反射型光スイッチ本体における入出射位置は、左側光路に等間隔で並んでいる。従って、４本の光ファイバ３０を一列に配列した構成で対応できる。
【００３４】
図２に示す例は、４芯フェルール３１と、各光路に共通の光集束性の結合用レンズ３２と、該結合用レンズ３２からの斜め方向の出射光を光軸に平行に、光軸に平行な光を結合用レンズ３２への斜め方向の入射光にする光路補正素子３４からなる。ここで光路補正素子３４は、４個の楔形プリズム３４ａ，…，３４ｄを光軸に関して対称配置し結合した構造である。内側プリズム３４ｂ，３４ｃの２個と外側プリズム３４ａ，３４ｄの２個はそれぞれ同一形状であり、光が入出射する一方の面は光軸に対して垂直であるが、他方の面は光軸に対して傾いている（傾斜は内側プリズムの方が外側プリズムよりも急である）。勿論、一体で精度よく加工できればそれでもよいし、内側の２個を一体化し、外側と組み合わせた３ピース構成でもよい。
【００３５】
図３に示す例は、４本の光ファイバ３０を配列したファイバアレイ３６と、各光ファイバにそれぞれ対応して４個のレンズ素子３７を配列したコリメータレンズアレイ３８とからなる。
【００３６】
これらによって４本の光ファイバ３０を一列に配列した入出射部を構成し、それを、例えば図１に示す反射型光スイッチ本体の平面反射体２９とは反対側のポートの位置に設置すればよいことになる。
【００３７】
また図１の例では、偏波分離合成用複屈折手段が、偏波分離合成用複屈折結晶と偏波分散補償用複屈折結晶とからなるが、図４に示すように、偏波分離合成用複屈折結晶を２分割し（複屈折結晶４０ａと複屈折結晶４０ｂ）、それらの間に１／２波長板４１を挿入した構造としてもよい。ここで一方の複屈折結晶４０ａは、光学軸がｘｚ面内にあってｚ軸に対してある向き（例えば＋側）に傾いている設定とし、他方の複屈折結晶４０ｂは、光学軸がｘｚ面内にあってｚ軸に対して反対の向き（従って−側）に傾いている設定とする。また、１／２波長板４２は、光学軸がｘｙ面内にあってｘ軸に対して４５度傾いている設定として通過光の偏波方向を９０度回転させ、常光・異常光が入れ替わるようにする。すると、前半分の複屈折結晶４０ａにおいて直進した常光成分が後半分の複屈折結晶４０ｂでは異常光成分となって−ｘ方向に屈折して分離し、また前半分の複屈折結晶４０ａにおいて＋ｙ方向に屈折した異常光成分は後半分の複屈折結晶４０ｂでは常光成分となって直進するため分離することになり、偏波分散を補償することができる。
【００３８】
図５は、反射型光スイッチ本体の他の実施例を示している。基本的な構成は図１と類似しているので、説明を簡略化するため、同一であってよい部材には同一符号を付し、主に相違点について説明する。この実施例では、偏波分離合成用複屈折手段として偏波分離合成用複屈折結晶２４のみを用いる。偏波回転反射手段４２の反射体としては、２段階の反射で光路を切り換えるＶ型反射体４３を用いる。このＶ型反射体４３は、４５度傾斜のＶ溝面が反射面となっているもので、そのＶ溝がｙ軸に平行となる向きに設置する。
【００３９】
この実施例の反射型光スイッチ本体の動作は、反射の部分を除けば図１の例と殆ど同様である。Ｖ型反射体４３では、左側光路の光はＶ溝の両面における２段階の反射で右側光路の光となり、右側光路の光は同様にＶ溝の両面における２段階の反射で左側光路の光となる。これによって、偏波分離合成用複屈折結晶２４での往路と復路で常光・異常光の入れ替えが行われることになる。従って、図１のような偏波分散補償用複屈折結晶２５を組み込まなくても実質的に偏波分散を補償することができる。
【００４０】
図６は、反射型光スイッチ本体の更に他の実施例を示している。基本的な構成は図１と類似しているので、説明を簡略化するため、同一であってよい部材には同一符号を付し、主に相違点について説明する。この実施例では、図１の偏波回転反射手段２２の代わりに光路変更反射手段を用いており、その光路変更反射手段として２段階の反射で光路を切り換えるＶ型反射体４４を用いている。この場合、偏波を回転させる必要がないため１／４波長板（あるいは４５度固定ファラデー回転子）は不要である。このＶ型反射体４４は、４５度傾斜のＶ溝面が反射面となっているものであるが、この場合には図５とは異なり、Ｖ溝がｘ軸に平行となる向きに設置する。
【００４１】
このＶ型反射体４４では、２段目光路の光はＶ溝の両面での２段階の反射で５段目光路の光となり、逆に５段目光路の光は２段目光路の光となる。また３段目光路の光はＶ溝の両面での２段階の反射で４段目光路の光となり、逆に４段目光路の光は３段目光路の光となる。しかし、ここでは左右の光路の入れ替えは生じない。従って、図１と同様、偏波分離合成用複屈折手段１０として、偏波分散を補償できる構造とするのが好ましい。
【００４２】
この構成では、±４５度可変ファラデー回転子２６によりファラデー回転角を＋４５度に制御することによって、３段目左側の第１入力ポート（Ｉ１）から入射する光は１段目左側の第１出力ポート（Ｏ１）から出射し、２段目左側の第２入力ポート（Ｉ２）から入射する光は４段目左側の第２出力ポート（Ｏ２）から出射する。また、ファラデー回転角を−４５度に制御することによって、３段目左側の第１入力ポート（Ｉ１）から入射する光は４段目左側の第２出力ポート（Ｏ２）から出射し、２段目左側の第２入力ポート（Ｉ２）から入射する光は１段目左側の第１出力ポート（Ｏ１）から出射する。従って、ファラデー回転の方向もしくはポートの位置関係は異なるが、この実施例でも２×２型（２入力・２出力）の反射型光スイッチを実現できる。
【００４３】
図７は、反射型光スイッチ本体の更に他の実施例を示している。基本的な構成は図６と類似しているので、説明を簡略化するため、同一であってよい部材には同一符号を付し、主に相違点について説明する。この実施例では、偏波分離合成用複屈折手段として偏波分離合成用複屈折結晶２４のみを用いている。偏波分散補償用複屈折結晶は不要である。光路変更反射手段としては、２段階の反射で光路を切り換えると共に往復路で常光光路と異常光光路を入れ換える四角錐状（ピラミッド形状）に凹陥した反射面をもつ方錐状反射体４６を用いる。この場合、偏波を回転させる必要がないため、１／４波長板（あるいは４５度固定ファラデー回転子）は不要である。この方錐状反射体４６は、４面の４５度傾斜面で囲まれ、開口の対角線がｘ軸及びｙ軸に一致する向きに設置する。なお、方錐状反射体は一体構造である必要はなく、複数のピースを組み合わせ接合した構造でもよい。
【００４４】
この方錐状反射体４６では、２段目左側光路の光は２段階の反射で５段目右側光路の光となり、逆に５段目左側光路の光は２段目右側光路の光となる。また３段目左側光路の光は２段階の反射で４段目右側光路の光となり、逆に４段目左側光路の光は３段目右側光路の光となる。同様に、右側光路の光は左側光路の光となる。このように、上下の光路の入れ替えと同時に左右の光路の入れ替えも生じる。これによって、偏波分離合成用複屈折結晶２４での往路と復路で常光・異常光の入れ替えが行われることになり、偏波分散補償用複屈折結晶を用いなくても実質的に偏波分散を補償することができるのである。
【００４５】
この構成では、±４５度可変ファラデー回転子２６によりファラデー回転角を＋４５度に制御することによって、３段目左側の第１入力ポート（Ｉ１）から入射する光は１段目左側の第１出力ポート（Ｏ１）から出射し、２段目左側の第２入力ポート（Ｉ２）から入射する光は４段目左側の第２出力ポート（Ｏ２）から出射する。また、ファラデー回転角を−４５度に制御することによって、３段目左側の第１入力ポート（Ｉ１）から入射する光は４段目左側の第２出力ポート（Ｏ２）から出射し、２段目左側の第２入力ポート（Ｉ２）から入射する光は１段目左側の第１出力ポート（Ｏ１）から出射する。従って、ファラデー回転の方向もしくはポートの位置関係は異なるが、この実施例でも２×２型（２入力・２出力）の反射型光スイッチを実現できる。
【００４６】
図２及び図３に示す入出射部は、図５〜図７に示す反射型光スイッチ本体にも適用できることは言うまでもない。図４に示す偏波分散補償機能を有する偏波分離合成用複屈折手段は、図６に示す反射型光スイッチ本体にも適用できる。
【００４７】
次に反射型光サーキュレータについて説明する。図８は本発明に係る反射型光サーキュレータの一実施例を示す説明図であり、素子の配列構造と各位置での偏波状態を示している。光サーキュレータ本体は、偏波分離合成用複屈折手段５０と、偏波回転手段５２と、第１の直線位相子５４と、第１の光路制御用複屈折手段５６と、第２の直線位相子５８と、第２の光路制御用複屈折手段６０と、偏波回転反射手段６２とを、その順序で光軸に沿って配列した構成である。説明を分かり易くするため、ここでも素子の配列方向（光軸）をｚ軸とし、該ｚ軸に直交する２軸をそれぞれｘ軸（横軸）、ｙ軸（縦軸）とする座標軸を設定する。また便宜的に、往路における光の進行方向を基準として、ｘ方向を右方向、ｙ方向を上方向とし、光路は下から順に１段目、２段目、…、５段目と称する。また偏波の回転方向は、ｚ方向（往路における光の進行方向）をみて反時計回りを＋側とする。
【００４８】
光は光軸に平行に入出射する。偏波分離合成用複屈折手段５０は、偏波方向が直交関係にある同じ光路の光を常光・異常光に分離し異なる光路の常光・異常光を合成するもので、光学軸がｘｚ面内でｚ軸から傾いている複屈折結晶６４からなる。なお、組み合わされている次の複屈折結晶６５は偏波分散を補償するためのものであり、光学軸がｙ軸に平行に設定され、常光・異常光が入れ替わることで光路長を補正している。偏波回転手段５２は、異なる光路の光の偏波方向を直交から平行又は平行から直交の関係に変換するものであり、４５度固定ファラデー回転子６６と左右分割されている一対の１／２波長板６７ａ，６７ｂの組み合わせからなる。４５度固定ファラデー回転子６６は、磁気光学結晶からなるファラデー素子と該ファラデー素子に外部磁界を印加する永久磁石を備えた構造である。左側の１／２波長板６７ａは光学軸がｘｙ面内でｘ軸に対して＋２２．５度傾き、右側の１／２波長板２７ｂは光学軸がｘｙ面内でｘ軸に対して−２２．５度傾くように組み合わされている。第１の直線位相子５４は、２段目光路と４段目光路に配置された１／２波長板５４ａ，５４ｂ（いずれも光学軸はｘｙ面内でｘ軸に対して＋４５度傾いている）からなり、２段目光路と４段目光路の光の偏波方向を９０度回転する。第１の光路制御用複屈折手段５６は、偏波方向に応じて光路シフトを制御するもので、光学軸がｙｚ面内でｚ軸から傾いている複屈折結晶からなる。第２の直線位相子５８は、１段目光路と５段目光路に配置された１／２波長板５８ａ，５８ｂ（いずれも光学軸はｘｙ面内でｘ軸に対して＋４５度傾いている）からなり、１段目光路と５段目光路の光の偏波方向を９０度回転する。第２の光路制御用複屈折手段６０は、第１の光路制御用複屈折手段５６と同じもので、偏波方向に応じて光路シフトを制御するもので、光学軸がｙｚ面内でｚ軸から傾いている複屈折結晶からなる。偏波回転反射手段６２は、偏波面を往復で９０度回転させるもので、１／４波長板６８と平面反射体６９の組み合わせからなる（１／４波長板に代えて４５度固定ファラデー回転子を用いてもよい）。１／４波長板６８は、直線偏光を回転偏光に、あるいは回転偏光を直線偏光に変換するものである。これによって、この光デバイスは光サーキュレータ機能を呈する。
【００４９】
この反射型光サーキュレータの動作は次の通りである。４５度固定ファラデー回転子６６は、ここでは偏波方向を反時計方向に４５度回転させるものとする。
【００５０】
３段目左側の第１ポート（Ｐ１）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段５０（複屈折結晶６４）で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。４５度固定ファラデー回転子６６では偏波方向が＋４５度回転し、左右一対の１／２波長板６７ａ，６７ｂで両光の偏波方向が直交から平行（ｙ軸と平行）の関係に変換される。１／２波長板は、入力光の偏波面を光学軸に対して対称な方向に変換する性質を備えているからである。両光は第１の直線位相子５４をバイパスし、第１の光路制御用複屈折手段５６では異常光となるので上方向（＋ｙ方向）に屈折し４段目光路にシフトする。第２の直線位相子５８もバイパスし、第２の光路制御用複屈折手段６０でも異常光となるので上方向（＋ｙ方向）に屈折し５段目光路にシフトする。そして１／４波長板６８で円偏波になり、平面反射体６９に達する。
【００５１】
平面反射体６９による反射光は円偏波のままであるが、再び１／４波長板６８を通過することで直線偏光に戻る。しかし両光の偏波方向はｘ軸と平行となる。これら両光は、第２の光路制御用複屈折手段６０に対しては常光であるので光路はシフトせず、そのまま直進する。次に第２の直線位相子５８（１／２波長板５８ｂ）を通過することで偏波方向がｙ軸と平行になり、第１の光路制御用複屈折手段５６では異常光となるので下方向（−ｙ方向）に屈折し４段目光路にシフトする。両光は第１の直線位相子５４（１／２波長板５４ｂ）を通過することで偏波方向がｘ軸と平行になり、１／２波長板６７ａ，６７ｂで左側光路の光の偏波方向は＋４５度回転し、右側光路の光は−４５度回転する。そのため、両光は偏波方向が平行から直交の関係となる。そして４５度固定ファラデー回転子６６でそれぞれ＋４５度回転する。両光は偏波分離合成用複屈折手段５０（複屈折結晶６４）で常光は直進し、異常光は−ｘ方向に屈折することで合成され、４段目左側の第２ポート（Ｐ２）に結合する。
【００５２】
４段目左側の第２ポート（Ｐ２）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段５０で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。４５度固定ファラデー回転子６６では偏波方向が＋４５度回転し、左右一対の１／２波長板６７ａ，６７ｂで両光の偏波方向が直交から平行（ｙ軸と平行）の関係に変換される。両光は第１の直線位相子５４（１／２波長板５４ｂ）を通過して偏波方向がｘ軸と平行になり、第１の光路制御用複屈折手段５６では常光となるため直進する。第２の直線位相子５８をバイパスし、第２の光路制御用複屈折手段６０でも常光となるため直進する。そして１／４波長板６８で円偏波になり、平面反射体６９に達する。
【００５３】
平面反射体６９からの反射光は円偏波のままであるが、再び１／４波長板６８を通過することで直線偏光に戻る。しかし、偏波方向はｙ軸と平行となる。これら両光は、第２の光路制御用複屈折手段６０に対しては異常光であるので−ｙ方向に屈折して光路は３段目にシフトする。両光は第２の直線位相子５８をバイパスし、第１の光路制御用複屈折手段５６でも異常光であるため−ｙ方向に屈折して光路は２段目にシフトする。両光は、１／２波長板６７ａ，６７ｂで左側光路の光の偏波方向は＋４５度回転し、右側光路の光は−４５度回転して直交の関係となり、４５度固定ファラデー回転子６６でそれぞれ＋４５度回転する。そして両光は偏波分離合成用複屈折手段５０で常光は直進し、異常光は−ｘ方向に屈折することで合成され、２段目左側の第３ポート（Ｐ３）に結合する。
【００５４】
２段目左側の第３ポート（Ｐ３）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段５０で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。４５度固定ファラデー回転子６６では偏波方向が＋４５度回転し、左右一対の１／２波長板６７ａ，６７ｂで両光の偏波方向が直交から平行（ｙ軸と平行）の関係に変換される。両光は第１の直線位相子５４（１／２波長板５４ａ）を通過して偏波方向がｘ軸と平行になり、第１の光路制御用複屈折手段５６では常光となるのでそのまま直進し、第２の直線位相子５８をバイパスし、第２の光路制御用複屈折手段６０でも常光となるのでそのまま直進する。そして１／４波長板６８で円偏波になり、平面反射体６９に達する。
【００５５】
平面反射体６９による反射光は円偏波のままであるが、再び１／４波長板６８を通過することで直線偏光に戻る。しかし両光の偏波方向はｙ軸と平行となる。これら両光は、第２の光路制御用複屈折手段６０に対しては異常光であるので−ｙ方向に屈折し１段目光路にシフトする。次に第２の直線位相子５８（１／２波長板５８ａ）を通過して偏波方向がｘ軸と平行になり、第１の光路制御用複屈折手段５６では常光となるので直進する。両光は第１の直線位相子５４をバイパスし、左右の１／２波長板６７ａ，６７ｂで左側光路の光の偏波方向は＋４５度回転し、右側光路の光は−４５度回転して直交関係に戻る。そして４５度固定ファラデー回転子６６でそれぞれ＋４５度回転する。両光は偏波分離合成用複屈折手段５０で常光は直進し、異常光は−ｘ方向に屈折することで合成され、１段目左側の第４ポート（Ｐ４）に結合する。
【００５６】
１段目左側の第４ポート（Ｐ４）から＋ｚ方向に入力する光は、偏波分離合成用複屈折手段５０で常光は直進し、異常光は屈折して＋ｘ方向に光分離するとともに偏波分散が補償される。４５度固定ファラデー回転子６６では偏波方向が＋４５度回転し、左右一対の１／２波長板６７ａ，６７ｂで両光の偏波方向が直交から平行（ｙ軸と平行）の関係に変換される。両光は第１の直線位相子５４をバイパスし、第１の光路制御用複屈折手段５６では異常光となるため上方向（＋ｙ方向）に屈折し２段目光路にシフトする。第２の直線位相子５８をバイパスし、第２の光路制御用複屈折手段６０でも異常光となるため上方向（＋ｙ方向）に屈折して３段目光路にシフトする。そして１／４波長板６８で円偏波になり、平面反射体６９に達する。
【００５７】
平面反射体６９からの反射光は円偏波のままであるが、再び１／４波長板６８を通過することで直線偏光に戻る。しかし、偏波方向はｘ軸と平行となる。これら両光は、第２の光路制御用複屈折手段６０に対しては常光であるのでそのまま直進する。両光は第２の直線位相子５８をバイパスし、第１の光路制御用複屈折手段５６でも常光であるため直進し、第１の直線位相子５４もバイパスする。両光は、左右の１／２波長板６７ａ，６７ｂで左側光路の光の偏波方向は＋４５度回転し、右側光路の光は−４５度回転して直交の関係となり、４５度固定ファラデー回転子６６でそれぞれ＋４５度回転する。そして両光は偏波分離合成用複屈折手段５０で常光は直進し、異常光は−ｘ方向に屈折することで合成され、３段目左側の第１ポート（Ｐ１）に結合する。
【００５８】
このようにして、３段目左側の第１ポート（Ｐ１）から入射する光は４段目左側の第２ポート（Ｐ２）から出射し、２段目左側の第２ポート（Ｐ２）から入射する光は２段目左側の第３ポート（Ｐ３）から出射する。２段目左側の第３ポート（Ｐ３）から入射する光は１段目左側の第４ポート（Ｐ４）から出射し、１段目左側の第４ポート（Ｐ４）から入射する光は３段目左側の第１ポート（Ｐ１）から出射する。従って、４ポート完全循環型の反射型光サーキュレータが実現できる。
【００５９】
第１ポートから第４ポートは、順序は別にして、１列に等間隔で並んでいる状態となるから、入出射部は、前述した図２及び図３と同様の構成であってよい。偏波分離合成用複屈折手段も、図４に示すように、偏波分離合成用複屈折結晶を２分割し、それらの間に１／２波長板を挿入した構造としてもよい。
【００６０】
図９は、反射型光サーキュレータ本体の他の実施例を示している。基本的な構成は図８と類似しているので、説明を簡略化するため、同一であってよい部材には同一符号を付し、主に相違点について説明する。この実施例では、偏波分離合成用複屈折手段として偏波分離合成用複屈折結晶６４のみを用い、偏波分散補償用複屈折結晶は不要である。偏波回転反射手段８２の反射体として、２段階の反射で光路を切り換えるＶ型反射体６３を用いる。このＶ型反射体８３は、４５度傾斜のＶ溝面が反射面となっているもので、Ｖ溝がｙ軸に平行となる向きに設置する。
【００６１】
この実施例の反射型光サーキュレータ本体の動作は、反射の部分を除けば図８の例と殆ど同様である。Ｖ型反射体８３では、左側光路の光はＶ溝の両面における２段階の反射で右側光路の光となり、右側光路の光は同様にＶ溝の両面における２段階の反射で左側光路の光となる。これによって、偏波分離合成用複屈折結晶６４での往路と復路で常光・異常光の入れ替えが行われることになる。従って、図８のような偏波分散補償用複屈折結晶６５を用いなくても実質的に偏波分散を補償することができる。
【００６２】
図１０は、反射型光サーキュレータ本体の更に他の実施例を示している。基本的な構成は図８と類似しているので、説明を簡略化するため、同一であってよい部材には同一符号を付し、主に相違点について説明する。この実施例では、図８の偏波回転反射手段６２の代わりに光路変更反射手段を用いており、その光路変更反射手段として、２段階の反射で光路を切り換えるＶ型反射体８４を用いている。偏波を回転させないため１／４波長板（あるいは４５度固定ファラデー回転子）は不要である。このＶ型反射体８４は、４５度傾斜のＶ溝面が反射面となっているものであるが、この場合には図９と異なり、Ｖ溝がｘ軸に平行となる向きに設置される。
【００６３】
このＶ型反射体８４では、２段目光路の光はＶ溝の両面での２段階の反射で５段目光路の光となり、逆に５段目光路の光は２段目光路の光となる。また３段目光路の光はＶ溝の両面での２段階の反射で４段目光路の光となり、逆に４段目光路の光は３段目光路の光となる。しかし、ここでは左右の光路の入れ替えは生じない。
【００６４】
この構成では、３段目左側の第１ポート（Ｐ１）から入射する光は１段目左側の第２ポート（Ｐ２）から出射し、１段目左側の第２ポート（Ｐ２）から入射する光は２段目左側の第３ポート（Ｐ３）から出射する。また、２段目左側の第３ポート（Ｐ３）から入射する光は４段目左側の第４ポート（Ｐ４）から出射し、４段目左側の第４ポート（Ｐ４）から入射する光は３段目左側の第１ポート（Ｐ１）から出射する。従って、ポートの位置関係は異なるが、４ポート完全循環型の反射型光サーキュレータが実現できる。
【００６５】
図１１は、反射型光サーキュレータ本体の更に他の実施例を示している。基本的な構成は図１０と類似しているので、説明を簡略化するため、同一であってよい部材には同一符号を付し、主に相違点について説明する。この実施例では、偏波分離合成用複屈折手段として偏波分離合成用複屈折結晶６４のみを用いる。偏波分散補償用複屈折結晶は不要である。そのため光路変更反射手段として、２段階の反射で光路を切り換えると共に往復路で常光光路と異常光光路を入れ換える四角錐状（ピラミッド形状）に凹陥した反射面をもつ方錐状反射体８６を用いている。１／４波長板（あるいは４５度固定ファラデー回転子）は不要である。この方錐状反射体８６は、４面の４５度傾斜面で囲まれ、それら傾斜面が反射面となり、開口の対角線がｘ軸及びｙ軸に一致する向きに設置する。なお、方錐状反射体は一体構造である必要はなく、複数のピースを組み合わせ接合した構造でもよい。
【００６６】
この方錐状反射体８６では、２段目左側光路の光は対向面での２段階の反射で５段目右側光路の光となり、逆に５段目左側光路の光は２段目右側光路の光となる。また３段目左側光路の光は対向面での２段階の反射で４段目右側光路の光となり、逆に４段目左側光路の光は３段目右側光路の光となる。同様に、右側光路の光は左側光路の光となる。このように上下の光路の入れ替えと同時に左右の光路の入れ替えも生じる。これによって、偏波分離合成用複屈折結晶６４での往路と復路で常光・異常光の入れ替えが行われることになり、偏波分散補償用複屈折結晶を用いなくても実質的に偏波分散を補償することができるのである。
【００６７】
この構成でも、３段目左側の第１ポート（Ｐ１）から入射する光は１段目左側の第２ポート（Ｐ２）から出射し、１段目左側の第２ポート（Ｐ２）から入射する光は２段目左側の第３ポート（Ｐ３）から出射する。また、２段目左側の第３ポート（Ｐ３）から入射する光は４段目左側の第４ポート（Ｐ４）から出射し、４段目左側の第４ポート（Ｐ４）から入射する光は３段目左側の第１ポート（Ｐ１）から出射する。従って、４ポート完全循環型の反射型光サーキュレータが実現できる。
【００６８】
図２及び図３に示す入出射部は、図９〜図１１に示す反射型光サーキュレータ本体にも適用できることは言うまでもない。図４に示す偏波分散補償機能を有する偏波分離合成用複屈折手段は、図１０に示す反射型光スイッチ本体にも適用できる。
【００６９】
【発明の効果】
本発明は上記のように構成した反射型光デバイスであり、光軸に沿って往復する光路を利用しているため、入出射部が両端に存在する透過型と異なり、基本的には偏波分離合成用の複屈折結晶が１個で済むなど部品点数を少なくでき安価に作製できるし小型化できる。また光ファイバが一方向のみに出るために、デバイスの取り扱いが容易となる利点もある。
【００７０】
本発明によれば、反射型光スイッチの場合には、２×２型（２入力・２出力）が実現できる。磁気光学方式であり可動部を持たないために、動作の信頼性は極めて高い。また反射型光サーキュレータの場合には、４ポート完全循環型が実現できる。
【図面の簡単な説明】
【図１】本発明に係る反射型光スイッチの一実施例を示す説明図。
【図２】入出力部の一例を示す説明図。
【図３】入出力部の他の例を示す説明図。
【図４】偏波分散補償機能を有する偏波分離合成用複屈折手段の他の例を示す説明図。
【図５】本発明に係る反射型光スイッチの他の実施例を示す説明図。
【図６】本発明に係る反射型光スイッチの更に他の実施例を示す説明図。
【図７】本発明に係る反射型光スイッチの更に他の実施例を示す説明図。
【図８】本発明に係る反射型光サーキュレータの一実施例を示す説明図。
【図９】本発明に係る反射型光サーキュレータの他の実施例を示す説明図。
【図１０】本発明に係る反射型光サーキュレータの更に他の実施例を示す説明図。
【図１１】本発明に係る反射型光サーキュレータの更に他の実施例を示す説明図。
【符号の説明】
１０偏波分離合成用複屈折手段
１２偏波回転手段
１４第１の直線位相子
１６第１の光路制御用複屈折手段
１８第２の直線位相子
２０第２の光路制御用複屈折手段
２２偏波回転反射手段
２６ ±４５度可変ファラデー回転子
２８１／４波長板
２９平面反射体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reflection-type optical device that controls the polarization direction using a Faraday rotator and controls the optical path shift using birefringence means, and realizes an optical switch function by a ± 45-degree variable Faraday rotator, Alternatively, the present invention relates to a reflection type optical device in which an optical circulator function is realized by a 45-degree fixed Faraday rotator.
[0002]
[Prior art]
[Patent Document 1]
JP-A-2000-39590
[0003]
In an optical communication system or an optical measurement system, an optical device such as an optical switch for switching an optical path and an optical circulator for controlling the optical path are incorporated. An optical switch is an optical device having an optical path switching function of outputting input light from an input port to an arbitrary selected one of output ports, and has a 1 × 2 type (1 input / 2 output). This is the most basic form. The optical circulator is an optical device having a function of cyclically controlling an optical path such that an input light from a first port is output to a second port and an input light from the second port is output to a third port. The three-port type is the most basic form.
[0004]
In particular, it is important for an optical device for optical communication to be polarization-independent, have good matching with an optical fiber, and have high reliability. As a device that can satisfy such a requirement, for example, an optical element group in which various optical elements such as a birefringent crystal that controls an optical path according to a polarization plane and a Faraday rotator that controls a rotation angle of the polarization plane are combined and arranged is necessary. There is a configuration for realizing an optical function unit.
[0005]
This type of optical device used to have a structure in which light is input from one end of the optical element group, travels in one direction through the optical element group, and is output from the other end (so-called transmission type). . However, in recent years, from the viewpoint of miniaturization of optical devices and the like, a group of arranged optical elements and a reflecting means (mirror) are combined, and light input from one end travels through the group of optical elements and reaches the mirror. Reflection type optical devices have been developed in which reflected light is output from one end side while traveling backward through the optical element group, and while the light reciprocates through the optical element group, switches and controls the optical path. For example, in Patent Document 1, a birefringent crystal, a 45-degree Faraday rotator, a half-wave plate, and a birefringent crystal are arranged in a single row, and an input / output section is provided at one end of the row, and a polarization rotation is provided at the other end. A reflective optical circulator in which an element and a reflector are arranged is disclosed.
[0006]
[Problems to be solved by the invention]
Such a reflection type optical device has an advantage that the number of components can be reduced and the length in the optical axis direction can be significantly reduced because light can have necessary functions while light travels back and forth between the optical element groups. . However, conventional reflective optical devices are limited in terms of function and their applications are limited.
[0007]
The reflective optical circulator having the configuration disclosed in Patent Document 1 certainly exhibits a circulator function, but is an incomplete circulation type. For example, in the case of a three-port type, input light from the first port is output to the second port, input light from the second port is output to the third port, but input light from the third port is output to the first port. Cannot be output. Even in the case of four or more ports, input light from the last port cannot be output to the first port.
[0008]
When the Faraday rotator is replaced with a variable magnetic field application method from a fixed magnetic field application method to a ± 45 degree variable Faraday rotator utilizing the above-described structure of the reflection type optical circulator, a switching function can be obtained. However, it is 1 × 2 type (1 input / 2 output) or 2 × 1 type (2 input / 1 output), and 2 × 2 type (2 input / 2 output) cannot be obtained.
[0009]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a reflection type optical device having a 2 × 2 type optical switch function. It is another object of the present invention to provide a reflective optical device that exhibits a fully circulating four-port optical circulator function. Still another object of the present invention is to provide a reflection type optical device which has a small number of components, high operation reliability, can be inexpensive, and can be miniaturized.
[0010]
[Means for Solving the Problems]
The present invention provides a birefringence means for separating and combining light in the same optical path having orthogonal polarization directions and combining light in different optical paths, and changing the polarization direction of light in different optical paths from orthogonal to parallel or parallel. Polarization rotating means for converting the optical path into an orthogonal relation, first and second birefringent means for controlling the optical path shift according to the polarization direction, and reflection by rotating the polarization plane by 90 degrees reciprocally. Polarization rotation reflection means or an optical path change reflection means that changes and reflects the reciprocating optical path, are arranged along the optical axis in that order,
A first linear phase shifter for rotating the polarization direction of light in a part of the optical path by 90 degrees between the polarization rotating means and the first optical path controlling birefringent means, and a first optical path controlling birefringent means. A second linear phase shifter that rotates the polarization direction of light in another part of the optical path by 90 degrees is inserted between the second linear path retarder and the second optical path controlling birefringent means, respectively.
Four or more optical fibers are arranged in the input / output unit located on the opposite side to the polarization rotation reflection unit or the optical path changing reflection unit,
The polarization rotator is a reflection type optical device comprising a combination of a ± 45 degree variable Faraday rotator and a pair of half-wave plates, and exhibiting an optical switch function by switching a polarization direction. .
[0011]
Also, the present invention provides a polarization-separating / combining birefringent unit that separates light beams in the same optical path having orthogonal polarization directions and combines light beams in different optical paths, and changes the polarization direction of light beams in different optical paths from orthogonal to parallel or Polarization rotating means for converting from a parallel to orthogonal relationship, first and second optical path controlling birefringent means for controlling the optical path shift according to the polarization direction, and reflection by rotating the plane of polarization 90 degrees back and forth. Polarization rotation reflection means or optical path change reflection means to change and reflect the reciprocating optical path, arranged along the optical axis in that order,
A first linear phase shifter for rotating the polarization direction of light in a part of the optical path by 90 degrees between the polarization rotating means and the first optical path controlling birefringent means, and a first optical path controlling birefringent means. A second linear phase shifter that rotates the polarization direction of light in another part of the optical path by 90 degrees is inserted between the second linear path retarder and the second optical path controlling birefringent means, respectively.
Four or more optical fibers are arranged in the input / output unit located on the opposite side to the polarization rotation reflection unit or the optical path changing reflection unit,
The polarization rotator is a reflection type optical device comprising a combination of a 45-degree fixed Faraday rotator and a pair of half-wave plates, and having an optical circulator function.
[0012]
With this configuration, the reflection type optical device according to the present invention is typically a 2 × 2 type (two input / two output) optical switch using four fibers or a four-port complete circulation type optical circulator. Will work.
[0013]
The polarization rotating / reflecting means has, for example, a configuration including a combination of a reciprocating 90-degree polarization rotator including a quarter-wave plate or a 45-degree fixed Faraday rotator and a plane reflector. The light path changing reflection means is composed of, for example, a V-shaped reflector that switches the light path by two-stage reflection. In this case, the V-shaped reflector is installed so that the V-shaped reflection surface is parallel to the direction of separation by the birefringent means for polarization separation / synthesis.
[0014]
The polarization splitting / combining birefringent means is composed of a polarization splitting / combining birefringent crystal and a polarization dispersion compensating birefringent crystal. A structure that compensates for polarization dispersion by compensating with a refraction crystal, or by dividing a birefringent crystal for polarization separation / synthesis into two and inserting a half-wave plate between them to replace ordinary and extraordinary light. I do.
[0015]
As the polarization rotating / reflecting means, a reciprocating 90-degree polarization rotator including a quarter-wave plate or a 45-degree fixed Faraday rotator, and a V-shaped reflector that switches the optical path by two-stage reflection may be used. In this case, the V-shaped reflector is installed so that the V-shaped reflecting surface is perpendicular to the direction of separation by the birefringent means for polarization separation / synthesis. Further, as the optical path changing / reflecting means, it is also possible to use a pyramidal reflector which switches the optical path of the reciprocating path by two-stage reflection and switches the ordinary optical path and the extraordinary optical path in the reciprocating path. According to these configurations, the ordinary light and the extraordinary light can be switched by reflection, so that the polarization dispersion can be compensated. Therefore, it is not necessary to use a combination of a plurality of birefringent crystals as described above for the birefringent means for polarization separation / synthesis, and the configuration is further simplified.
[0016]
The input / output unit includes four optical fibers, a four-core ferrule, a coupling lens common to each optical path, and obliquely emitted light from the coupling lens parallel to the optical axis and parallel to the optical axis. It is configured to include an optical path correction element that converts light into incident light to the coupling lens in an oblique direction. Alternatively, the input / output unit may be composed of a fiber array in which four optical fibers are juxtaposed, and a collimator lens array in which lens elements are arranged corresponding to the respective fiber arrays.
[0017]
The V-type reflector may have a configuration in which a reflection film is formed on the inner surface of the V-groove, or a configuration in which a reflection film is formed on the outer surface of the triangular prism. The pyramid-shaped reflector may also have a configuration in which a reflection film is formed on the inner surface of a quadrangular pyramid (pyramid) hole, or a configuration in which a reflection film is formed on the outer surface of a quadrangular pyramid prism. In any case, it is only necessary that the reflecting surface has a predetermined angle and direction, and a slight change in shape other than the reflecting surface is free.
[0018]
In the case of an optical device functioning as an optical switch, an electromagnet is used for a ± 45-degree variable Faraday rotator to apply a variable magnetic field that switches the direction of Faraday rotation. When a semi-hard magnetic material is used for the magnetic yoke, the magnetized state is maintained by itself even when the energization is stopped, so that power can be saved.
[0019]
In the present invention, a two-stage optical path shift mechanism of first and second optical path control birefringence means is incorporated, and light input from a specific port is coupled to a desired port by controlling the optical path shift of a reciprocating path. It is making it.
[0020]
【Example】
FIG. 1 is an explanatory view showing one embodiment of the reflection type optical switch according to the present invention. A shows the arrangement structure of the elements and the polarization state at each position, and B shows the optical path. The optical switch body includes a polarization splitting / combining birefringent unit 10, a polarization rotating unit 12, a first linear phase shifter 14, a first optical path controlling birefringent unit 16, and a second linear phase shifter. 18, a second optical path controlling birefringent means 20, and a polarization rotating / reflecting means 22 are arranged along the optical axis in that order. In order to make the description easy to understand, a coordinate axis is set with the element arrangement direction (optical axis) as the z axis and two axes orthogonal to the z axis as the x axis (horizontal axis) and the y axis (vertical axis), respectively. For convenience, the x direction is referred to as a rightward direction, the y direction is referred to as an upward direction, and the optical paths are referred to as a first stage, a second stage,. . The direction of rotation of the polarized light is defined to be positive on the counterclockwise direction with respect to the z direction (the traveling direction of light on the outward path).
[0021]
Light enters and exits parallel to the optical axis. The polarization splitting / combining birefringent means 10 separates light on the same optical path whose polarization directions are orthogonal to each other into ordinary light and extraordinary light, and combines ordinary light and extraordinary light on different optical paths. And a birefringent crystal 24 inclined from the z-axis. The next combined birefringent crystal 25 is for compensating the polarization dispersion generated in the birefringent crystal 24. The optical axis is set parallel to the y-axis, and the ordinary light and the extraordinary light are switched. Is used to correct the optical path length. The polarization rotator 12 converts the polarization directions of the light beams in different optical paths from orthogonal to parallel or from parallel to orthogonal. The ± 45-degree variable Faraday rotator 26 and a pair of 1 / It consists of a combination of two-wavelength plates 27a and 27b. The ± 45-degree variable Faraday rotator 26 includes a Faraday element made of a magneto-optical crystal (for example, a Bi-substituted rare earth iron garnet LPE film) and an electromagnet that applies a magnetic field to the Faraday element from the outside. , The Faraday rotation angle can be switched to +45 degrees or −45 degrees. The left half-wave plate 27a has an optical axis inclined at +22.5 degrees with respect to the x-axis in the xy plane, and the right half-wave plate 27b has an optical axis in the xy plane of -22 with respect to the x-axis. .5 degrees. The first linear phase shifter 14 is a half-wave plate 14a, 14b disposed in the second-stage optical path and the fourth-stage optical path (the optical axis is inclined at +45 degrees with respect to the x-axis in the xy plane). ), The polarization directions of the light in the second and fourth optical paths are rotated by 90 degrees. The first optical path control birefringent means 16 controls the optical path shift according to the polarization direction, and is made of a birefringent crystal whose optical axis is inclined from the z axis in the yz plane. The second linear phase shifter 18 has half-wave plates 18a and 18b arranged in the first-stage optical path and the fifth-stage optical path (both have an optical axis inclined +45 degrees with respect to the x-axis in the xy plane). ), The directions of polarization of the light in the first and fifth optical paths are rotated by 90 degrees. The second optical path controlling birefringent means 20 is the same as the first optical path controlling birefringent means 16 and controls the optical path shift in accordance with the polarization direction. It consists of a birefringent crystal that is tilted from. The polarization rotating / reflecting means 22 reflects the light by rotating the plane of polarization 90 degrees in a reciprocating manner and is composed of a combination of a quarter-wave plate 28 and a plane reflector 29 (fixed at 45 degrees instead of the quarter-wave plate). It is also possible to use a Faraday rotator). The 波長 wavelength plate 28 has a function of converting linearly polarized light into rotationally polarized light or converting rotationally polarized light into linearly polarized light. By switching the polarization direction to +45 degrees or -45 degrees by the ± 45 degree variable Faraday rotator 26 in the polarization rotation means 12, the optical device exhibits an optical switch function.
[0022]
The operation of this reflection type optical switch is as follows. First, the current supplied to the electromagnet is controlled so that the ± 45-degree variable Faraday rotator 26 generates + 45-degree Faraday rotation on the polarization plane.
[0023]
For the light input in the + z direction from the first input port (I1) on the left side of the third stage, the ordinary light goes straight through the polarization splitting / combining birefringent means 10 (birefringent crystal 24), and the extraordinary light is refracted to the + x direction. And the polarization dispersion is compensated by the birefringent crystal 25. In the ± 45-degree variable Faraday rotator 26, the polarization direction rotates by +45 degrees, and the polarization directions of the two lights are changed from orthogonal to parallel (parallel to the y-axis) by a pair of left and right half-wave plates 27a and 27b. Is done. This is because the half-wave plate has a property of converting the plane of polarization of input light into a direction symmetric with respect to the optical axis. Both lights bypass the first linear phase shifter 14 and become extraordinary light in the first optical path control birefringent means 16, so that they are refracted upward (+ y direction) and shifted to the fourth optical path. The second linear phase shifter 18 is also bypassed, and the second optical path controlling birefringent means 20 also becomes extraordinary light, so that it is refracted upward (+ y direction) and shifted to the fifth optical path. Then, the light is circularly polarized by the 波長 wavelength plate 28 and reaches the plane reflector 29.
[0024]
The light reflected by the plane reflector 29 remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 28 again. However, the polarization directions of both lights are parallel to the x-axis. Since these two lights are ordinary lights for the second optical path controlling birefringent means 20, the light paths do not shift but go straight. Next, the light passes through the second linear phase shifter 18 (the half-wave plate 18b) so that the polarization direction becomes parallel to the y-axis, and the first optical path control birefringent means 16 becomes extraordinary light. The light is refracted in the direction (−y direction) and shifts to the fourth optical path. The two lights pass through the first linear phase shifter 14 (the half-wave plate 14b) so that the polarization directions become parallel to the x-axis, and the half-wave plates 27a and 27b cause the polarization of the light in the left optical path. The direction rotates by +45 degrees, and the light in the right optical path rotates by -45 degrees. Therefore, the two lights have a polarization direction that is parallel to orthogonal. Then, each of them is rotated by +45 degrees by the ± 45-degree variable Faraday rotator 26. The two lights are combined by the polarization splitting / combining birefringent means 10 (birefringent crystal 24), the ordinary light goes straight, and the extraordinary light is refracted in the -x direction, and the first output port (O1) on the fourth stage left side To join.
[0025]
For the light input in the + z direction from the second input port (I2) on the left side of the second stage, the ordinary light goes straight through the polarization splitting / combining birefringent means 10 (birefringence 24), and the extraordinary light is refracted in the + x direction. Light is separated and polarization dispersion is compensated. In the ± 45-degree variable Faraday rotator 26, the polarization direction rotates by +45 degrees, and the polarization directions of the two lights are changed from orthogonal to parallel (parallel to the y-axis) by a pair of left and right half-wave plates 27a and 27b. Is done. Both light beams pass through the first linear phase shifter 14 (the half-wave plate 14a), the polarization direction becomes parallel to the x-axis, and the first light path controlling birefringent means 16 becomes ordinary light and travels straight. . The second linear phase shifter 18 is bypassed and the second optical path controlling birefringent means 20 also travels straight because it becomes ordinary light. Then, the light passes through the 板 wavelength plate 28 to become a circularly polarized wave, and reaches the plane reflector 29.
[0026]
The light reflected by the plane reflector 29 remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 28 again. However, the polarization direction is parallel to the y-axis. Since both of these lights are extraordinary lights with respect to the second optical path controlling birefringent means 20, they are refracted in the -y direction and the optical path is shifted to the first stage. The two lights pass through the second linear phase shifter 18 (the half-wave plate 18a), so that the polarization directions become parallel to the x-axis. Then, the first linear phase shifter 14 is bypassed. The two lights are rotated by +45 degrees in the left optical path by the half-wave plates 27a and 27b, are rotated by -45 degrees in the right optical path, and are rotated by +45 degrees by the ± 45-degree variable Faraday rotator 26. Therefore, the two lights have a polarization direction that is parallel to orthogonal. The two lights are combined by the polarization splitting / combining birefringent means 10 (birefringent crystal 24) so that the ordinary light goes straight, and the extraordinary light is refracted in the -x direction to be combined, and the second output port (O2 ).
[0027]
Next, the current supplied to the electromagnet is controlled so that the ± 45-degree variable Faraday rotator 26 causes -45-degree Faraday rotation on the polarization plane.
[0028]
The light input in the + z direction from the first input port (I1) on the left side of the third stage is converted into ordinary light by the polarization splitting / combining birefringent means 10, and extraordinary light is refracted and separated in the + x direction while being polarized. Wave dispersion is compensated. In the ± 45-degree variable Faraday rotator 26, the polarization direction is rotated by −45 degrees, and the pair of right and left half-wave plates 27a and 27b change the polarization direction of both lights from orthogonal to parallel (parallel to the x-axis). Is converted. Both lights bypass the first linear phase shifter 14 and travel straight because they become ordinary light in the first optical path control birefringent means 16, and also bypass the second linear phase shifter 18, and pass through the second optical path control complex. Since the refraction means 20 also becomes ordinary light, it goes straight through the third-stage optical path as it is. The light becomes circularly polarized by the 波長 wavelength plate 28, reaches the plane reflector 29, and is reflected.
[0029]
The reflected light remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 28 again. However, the polarization directions of both lights are parallel to the y-axis. Both of these lights are extraordinary lights with respect to the second optical path controlling birefringent means 20, so they are refracted in the -y direction and shifted to the second optical path. Next, the second linear phase shifter 18 is bypassed, and the first birefringent means 16 for controlling the optical path also becomes extraordinary light. Both lights bypass the first linear phase shifter 14, and the light in the left optical path is rotated +45 degrees and the light in the right optical path is rotated -45 degrees by the half-wave plates 27a and 27b. Then, each of them is rotated by -45 degrees by the ± 45-degree variable Faraday rotator 26. The two lights are combined by the polarization splitting / combining birefringent means 10, the ordinary light goes straight, and the extraordinary light is refracted in the -x direction, and is combined with the second output port (O2) on the left side of the first stage.
[0030]
Light input to the + z direction from the second input port (I2) on the left side of the second stage is converted into ordinary light by the polarization splitting / combining birefringent means 10, and extraordinary light is refracted and separated in the + x direction while being polarized. Wave dispersion is compensated. In the ± 45-degree variable Faraday rotator 26, the polarization direction is rotated by −45 degrees, and the pair of right and left half-wave plates 27a and 27b change the polarization direction of both lights from orthogonal to parallel (parallel to the x-axis). Is converted. Since both lights pass through the first linear phase shifter 14 (the half-wave plate 14a), the polarization directions become parallel to the y-axis, and the first light path controlling birefringent means 16 becomes extraordinary light. The light is refracted in the direction (+ y direction) and shifted to the third optical path. Since the second linear phase shifter 18 is bypassed and the second optical path control birefringent means 20 also becomes extraordinary light, it is refracted upward (+ y direction) and shifted to the fourth optical path. The light becomes circularly polarized by the 波長 wavelength plate 28, reaches the plane reflector 29, and is reflected.
[0031]
The reflected light remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 28 again. However, the polarization direction is parallel to the x-axis. Since these two lights are ordinary lights to the second optical path controlling birefringent means 20, they go straight as they are. Since both lights bypass the second linear phase shifter 18 and are ordinary light even in the first optical path control birefringent means 16, they proceed straight through the fourth-stage optical path as they are, and the first linear phase shifter 14 (１／ wavelength) Passing through the plate 14b) makes the polarization direction parallel to the y-axis. The two lights are rotated by +45 degrees in the left optical path by the half-wave plates 27a and 27b, the light in the right optical path is rotated by -45 degrees, and the variable Faraday rotator 26 is rotated by -45 degrees. The two lights are combined by the polarization splitting / combining birefringent means 10, the ordinary light goes straight, and the extraordinary light is refracted in the -x direction, and is combined with the first output port (O1) on the left side of the fourth stage.
[0032]
That is, by controlling the Faraday rotation angle to +45 degrees by the ± 45-degree variable Faraday rotator 26, light incident from the first input port (I1) on the third-stage left side is output to the fourth-stage first output port (I1). O1), and the light incident from the second input port (I2) on the second stage left side can be emitted from the second output port (O2) on the first stage left side. Further, by controlling the Faraday rotation angle to -45 degrees, light incident from the first input port (I1) on the left side of the third stage is emitted from the second output port (O2) on the left side of the first stage, so that the two-stage Light incident from the second input port (I2) on the left side of the eye can be emitted from the first output port (O1) on the left side of the fourth stage. In this way, a 2 × 2 (2 input / 2 output) reflective optical switch can be realized.
[0033]
2 and 3 show examples of the input / output unit. As can be seen from FIG. 1, the input / output positions in the reflection type optical switch main body are arranged at equal intervals in the left optical path. Therefore, a configuration in which four optical fibers 30 are arranged in a line can be used.
[0034]
In the example shown in FIG. 2, a four-core ferrule 31, a light-converging coupling lens 32 common to each optical path, and obliquely emitted light from the coupling lens 32 are parallel to the optical axis and parallel to the optical axis. An optical path correction element 34 converts parallel light into light obliquely incident on the coupling lens 32. Here, the optical path correction element 34 has a structure in which four wedge-shaped prisms 34a,. Two of the inner prisms 34b and 34c and two of the outer prisms 34a and 34d have the same shape, and one surface on which light enters and exits is perpendicular to the optical axis, while the other surface is perpendicular to the optical axis. (The inclination is steeper with the inner prism than with the outer prism). Of course, it is sufficient if it can be processed integrally and with high precision, or a three-piece configuration in which two inner parts are integrated and combined with the outer part may be used.
[0035]
The example shown in FIG. 3 includes a fiber array 36 in which four optical fibers 30 are arranged, and a collimator lens array 38 in which four lens elements 37 are arranged corresponding to each optical fiber.
[0036]
These components constitute an input / output unit in which four optical fibers 30 are arranged in a line, and are disposed at, for example, a port position opposite to the plane reflector 29 of the reflective optical switch body shown in FIG. It will be good.
[0037]
Further, in the example of FIG. 1, the birefringence means for polarization separation / combination includes a birefringence crystal for polarization separation / combination and a birefringence crystal for polarization dispersion compensation, but as shown in FIG. The birefringent crystal for use may be divided into two (birefringent crystal 40a and birefringent crystal 40b), and a half-wave plate 41 may be inserted between them. Here, one birefringent crystal 40a is set so that the optic axis is in the xz plane and inclined in a certain direction (for example, + side) with respect to the z axis, and the other birefringent crystal 40b has the optic axis of xz It is set to be in the plane and inclined in the opposite direction (accordingly, on the negative side) with respect to the z-axis. The half-wave plate 42 rotates the polarization direction of the transmitted light by 90 degrees so that the optical axis is in the xy plane and is inclined at 45 degrees with respect to the x axis so that the ordinary light and the extraordinary light are switched. To Then, the ordinary light component traveling straight in the birefringent crystal 40a in the first half becomes an extraordinary light component in the birefringent crystal 40b in the second half and is refracted and separated in the −x direction, and the + y direction in the birefringent crystal 40a in the first half. The extraordinary light component refracted in the second direction becomes an ordinary light component in the latter half birefringent crystal 40b and travels straight to be separated, thereby compensating for polarization dispersion.
[0038]
FIG. 5 shows another embodiment of the reflection type optical switch body. Since the basic configuration is similar to that of FIG. 1, for simplification of description, the same members are denoted by the same reference numerals, and mainly the differences will be described. In this embodiment, only the polarization splitting / combining birefringent crystal 24 is used as the polarization splitting / combining birefringent means. As the reflector of the polarization rotation reflector 42, a V-shaped reflector 43 that switches the optical path by two-stage reflection is used. The V-shaped reflector 43 has a V-groove surface inclined at 45 degrees as a reflection surface, and is installed in a direction in which the V-groove is parallel to the y-axis.
[0039]
The operation of the reflection type optical switch body of this embodiment is almost the same as the example of FIG. 1 except for the reflection part. In the V-shaped reflector 43, the light in the left optical path becomes light in the right optical path by two-stage reflection on both surfaces of the V groove, and the light in the right optical path is similarly reflected by light in the two stages on both surfaces of the V groove and light in the left optical path. Become. As a result, the ordinary light and the extraordinary light are exchanged between the forward path and the return path in the polarization splitting / combining birefringent crystal 24. Therefore, the polarization dispersion can be substantially compensated without incorporating the polarization dispersion compensation birefringent crystal 25 as shown in FIG.
[0040]
FIG. 6 shows still another embodiment of the reflection type optical switch body. Since the basic configuration is similar to that of FIG. 1, for simplification of description, the same members are denoted by the same reference numerals, and mainly the differences will be described. In this embodiment, an optical path changing / reflecting means is used in place of the polarization rotating / reflecting means 22 in FIG. 1, and a V-shaped reflector 44 for switching the optical path by two-stage reflection is used as the optical path changing / reflecting means. In this case, since there is no need to rotate the polarization, a quarter-wave plate (or a 45-degree fixed Faraday rotator) is not required. The V-shaped reflector 44 has a V-groove surface inclined at 45 degrees as a reflection surface. In this case, unlike FIG. 5, the V-groove is installed in a direction in which the V-groove is parallel to the x-axis. .
[0041]
In the V-shaped reflector 44, the light in the second-stage optical path becomes the light in the fifth-stage optical path due to the two-stage reflection on both sides of the V-groove, and conversely, the light in the fifth-stage optical path becomes the light in the second-stage optical path. Become. The light of the third optical path becomes light of the fourth optical path by two-stage reflection on both sides of the V-groove, and the light of the fourth optical path becomes light of the third optical path. However, the left and right optical paths do not interchange here. Therefore, as in FIG. 1, it is preferable that the polarization splitting / combining birefringent means 10 has a structure capable of compensating for polarization dispersion.
[0042]
In this configuration, by controlling the Faraday rotation angle to +45 degrees by the ± 45-degree variable Faraday rotator 26, light incident from the first input port (I1) on the third-stage left side is output to the first-stage first output port (I1). Light emitted from the port (O1) and entering from the second input port (I2) on the second stage left exits from the second output port (O2) on the fourth stage left. Further, by controlling the Faraday rotation angle to -45 degrees, the light incident from the first input port (I1) on the left side of the third stage exits from the second output port (O2) on the left side of the fourth stage, Light incident from the second input port (I2) on the left side of the eye exits from the first output port (O1) on the left side of the first stage. Therefore, although the direction of the Faraday rotation or the positional relationship of the ports is different, a reflection optical switch of 2 × 2 type (2 inputs / 2 outputs) can also be realized in this embodiment.
[0043]
FIG. 7 shows still another embodiment of the reflection type optical switch body. Since the basic configuration is similar to that of FIG. 6, for simplicity of description, the same members are denoted by the same reference numerals, and mainly the differences will be described. In this embodiment, only the polarization splitting / combining birefringent crystal 24 is used as the polarization splitting / combining birefringent means. No birefringent crystal for polarization dispersion compensation is required. As the optical path changing reflecting means, a quadrangular pyramid-shaped reflector 46 having a quadrangular pyramid-shaped (pyramid-shaped) reflecting surface that switches the optical path by two-stage reflection and switches the ordinary optical path and the extraordinary optical path in the reciprocating path is used. In this case, since there is no need to rotate the polarization, a quarter-wave plate (or a 45-degree fixed Faraday rotator) is not required. The pyramid-shaped reflector 46 is surrounded by four 45-degree inclined surfaces, and is installed so that the diagonal line of the opening coincides with the x-axis and the y-axis. The pyramid-shaped reflector does not need to have an integral structure, and may have a structure in which a plurality of pieces are combined and joined.
[0044]
In the pyramidal reflector 46, light in the second-stage left optical path becomes light in the fifth-stage right optical path by two-stage reflection, and conversely, light in the fifth-stage left optical path becomes light in the second-stage right optical path. The light in the third-stage left optical path becomes light in the fourth-stage right optical path due to two-stage reflection, and the light in the fourth-stage left optical path becomes light in the third-stage right optical path. Similarly, light on the right optical path becomes light on the left optical path. In this way, the left and right optical paths are switched at the same time as the upper and lower optical paths are switched. As a result, the ordinary light and the extraordinary light are exchanged between the forward path and the return path in the polarization splitting / combining birefringent crystal 24, and the polarization dispersion can be substantially reduced without using the polarization dispersion compensating birefringent crystal. Can be compensated for.
[0045]
In this configuration, by controlling the Faraday rotation angle to +45 degrees by the ± 45-degree variable Faraday rotator 26, light incident from the first input port (I1) on the third-stage left side is output to the first-stage first output port (I1). Light emitted from the port (O1) and entering from the second input port (I2) on the second stage left exits from the second output port (O2) on the fourth stage left. Further, by controlling the Faraday rotation angle to -45 degrees, the light incident from the first input port (I1) on the left side of the third stage exits from the second output port (O2) on the left side of the fourth stage, Light incident from the second input port (I2) on the left side of the eye exits from the first output port (O1) on the left side of the first stage. Therefore, although the direction of the Faraday rotation or the positional relationship of the ports is different, a reflection optical switch of 2 × 2 type (2 inputs / 2 outputs) can also be realized in this embodiment.
[0046]
It goes without saying that the input / output unit shown in FIGS. 2 and 3 can also be applied to the reflection type optical switch body shown in FIGS. The polarization splitting / combining birefringence means having the polarization dispersion compensation function shown in FIG. 4 can also be applied to the reflection type optical switch body shown in FIG.
[0047]
Next, the reflection type optical circulator will be described. FIG. 8 is an explanatory view showing one embodiment of the reflection type optical circulator according to the present invention, and shows an arrangement structure of the elements and a polarization state at each position. The optical circulator body includes a polarization separating / combining birefringent means 50, a polarization rotating means 52, a first linear phase shifter 54, a first optical path controlling birefringent means 56, and a second linear phase shifter. 58, a second optical path controlling birefringent means 60, and a polarization rotating / reflecting means 62 are arranged along the optical axis in that order. For the sake of simplicity of explanation, a coordinate axis is set in which the element arrangement direction (optical axis) is the z axis, and two axes orthogonal to the z axis are the x axis (horizontal axis) and the y axis (vertical axis). I do. For convenience, the x direction is the right direction, the y direction is the upper direction, and the optical path is referred to as the first, second,. The direction of rotation of the polarized light is defined as the + side in the counterclockwise direction as viewed in the z direction (the traveling direction of light in the outward path).
[0048]
Light enters and exits parallel to the optical axis. The polarization splitting / combining birefringent means 50 separates light in the same optical path having orthogonal polarization directions into ordinary light and extraordinary light, and combines ordinary light and extraordinary light in different optical paths, and has an optical axis in the xz plane. And a birefringent crystal 64 inclined from the z-axis. The next combined birefringent crystal 65 is for compensating the polarization dispersion, the optical axis is set parallel to the y-axis, and the ordinary and extraordinary light are exchanged to correct the optical path length. I have. The polarization rotator 52 converts the polarization directions of the light beams in different optical paths from orthogonal to parallel or from parallel to orthogonal. The 45-degree fixed Faraday rotator 66 and a pair of right and left divided 1/2 It consists of a combination of wave plates 67a, 67b. The 45-degree fixed Faraday rotator 66 has a structure including a Faraday element made of a magneto-optical crystal and a permanent magnet for applying an external magnetic field to the Faraday element. The left half-wave plate 67a has an optical axis inclined at +22.5 degrees with respect to the x-axis in the xy plane, and the right half-wave plate 27b has an optical axis in the xy plane of -22 with respect to the x-axis. .5 degrees. The first linear phase shifter 54 is a half-wave plate 54a, 54b disposed on the second-stage optical path and the fourth-stage optical path (both optical axes are inclined +45 degrees with respect to the x-axis in the xy plane). ), The polarization directions of the light in the second and fourth optical paths are rotated by 90 degrees. The first optical path controlling birefringent means 56 controls the optical path shift according to the polarization direction, and is made of a birefringent crystal whose optical axis is inclined from the z axis in the yz plane. The second linear phase shifter 58 is a half-wave plate 58a, 58b disposed in the first-stage optical path and the fifth-stage optical path (both optical axes are inclined +45 degrees with respect to the x-axis in the xy plane). ), The directions of polarization of the light in the first and fifth optical paths are rotated by 90 degrees. The second optical path control birefringent means 60 is the same as the first optical path control birefringent means 56, and controls the optical path shift according to the polarization direction. The optical axis is in the z-axis in the yz plane. It consists of a birefringent crystal that is tilted from. The polarization rotating / reflecting means 62 rotates the polarization plane 90 degrees in a reciprocating manner, and is composed of a combination of a quarter-wave plate 68 and a plane reflector 69 (instead of a quarter-wave plate, a 45-degree fixed Faraday rotator is used). May be used). The 波長 wavelength plate 68 converts linearly polarized light into rotationally polarized light or vice versa. Thereby, the optical device has an optical circulator function.
[0049]
The operation of this reflective optical circulator is as follows. Here, the 45-degree fixed Faraday rotator 66 rotates the polarization direction by 45 degrees counterclockwise.
[0050]
For the light input in the + z direction from the first port (P1) on the left side of the third stage, ordinary light goes straight through the polarization splitting / combining birefringent means 50 (birefringent crystal 64), and the extraordinary light is refracted in the + x direction. Light is separated and polarization dispersion is compensated. In the 45-degree fixed Faraday rotator 66, the polarization direction is rotated by +45 degrees, and the pair of left and right half-wave plates 67a and 67b convert the polarization directions of both lights from orthogonal to parallel (parallel to the y-axis). You. This is because the half-wave plate has a property of converting the plane of polarization of input light into a direction symmetric with respect to the optical axis. Both lights bypass the first linear phase shifter 54 and become extraordinary light in the first birefringence means 56 for controlling the optical path, so that they are refracted upward (+ y direction) and shifted to the fourth optical path. The second linear phase shifter 58 is also bypassed, and becomes extraordinary light even in the second optical path controlling birefringent means 60, so that it is refracted upward (+ y direction) and shifted to the fifth optical path. Then, the light is circularly polarized by the 波長 wavelength plate 68 and reaches the plane reflector 69.
[0051]
The light reflected by the plane reflector 69 remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 68 again. However, the polarization directions of both lights are parallel to the x-axis. Since these two lights are ordinary lights to the second optical path controlling birefringent means 60, the light paths do not shift and go straight. Next, by passing through the second linear phase shifter 58 (the half-wave plate 58b), the polarization direction becomes parallel to the y-axis, and the first optical path controlling birefringent means 56 becomes extraordinary light. The light is refracted in the direction (−y direction) and shifted to the fourth optical path. The two lights pass through the first linear phase shifter 54 (the half-wave plate 54b) so that the polarization directions become parallel to the x-axis, and the half-wave plates 67a and 67b make the polarization of the light in the left optical path. The direction rotates by +45 degrees, and the light in the right optical path rotates by -45 degrees. Therefore, the two lights have a polarization direction that is parallel to orthogonal. Then, the Faraday rotators 66 rotate at +45 degrees, respectively. The ordinary light goes straight and the extraordinary light is refracted in the -x direction by the polarization splitting / combining birefringent means 50 (birefringent crystal 64). The extraordinary light is combined into the second port (P2) on the left side of the fourth stage. Join.
[0052]
The ordinary light enters the + z direction from the second port (P2) on the left side of the fourth stage in the + z direction, and the extraordinary light is refracted and separated in the + x direction while being polarized. The dispersion is compensated. In the 45-degree fixed Faraday rotator 66, the polarization direction is rotated by +45 degrees, and the pair of left and right half-wave plates 67a and 67b convert the polarization directions of both lights from orthogonal to parallel (parallel to the y-axis). You. Both lights pass through the first linear phase shifter 54 (the half-wave plate 54b), the polarization direction becomes parallel to the x-axis, and the first light path controlling birefringent means 56 goes straight because it becomes ordinary light. . The second linear phase shifter 58 is bypassed, and the second optical path controlling birefringent means 60 also travels straight because it becomes ordinary light. Then, the light is circularly polarized by the 波長 wavelength plate 68 and reaches the plane reflector 69.
[0053]
The reflected light from the plane reflector 69 remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 68 again. However, the polarization direction is parallel to the y-axis. Since both of these lights are extraordinary lights with respect to the second optical path controlling birefringent means 60, they are refracted in the -y direction and the optical path is shifted to the third stage. Since both lights bypass the second linear phase shifter 58 and are also extraordinary lights in the first optical path control birefringent means 56, they are refracted in the -y direction and the optical path is shifted to the second stage. The two lights are rotated by +45 degrees in the polarization direction of the light in the left optical path by the half-wavelength plates 67a and 67b, and the lights in the right optical path are rotated by -45 degrees to have an orthogonal relationship, and the 45-degree fixed Faraday rotator 66 To rotate +45 degrees respectively. The two lights are combined by the polarization splitting / combining birefringent means 50, the ordinary light goes straight, and the extraordinary light is refracted in the -x direction, and combined to the third port (P3) on the left side of the second stage.
[0054]
Light input in the + z direction from the third port (P3) on the left side of the second stage is converted into ordinary light by the polarization splitting / combining birefringent means 50, and extraordinary light is refracted and separated in the + x direction while being polarized. The dispersion is compensated. In the 45-degree fixed Faraday rotator 66, the polarization direction is rotated by +45 degrees, and the pair of left and right half-wave plates 67a and 67b convert the polarization directions of both lights from orthogonal to parallel (parallel to the y-axis). You. Both light beams pass through the first linear phase shifter 54 (the half-wave plate 54a), and their polarization directions become parallel to the x-axis. Then, the second linear phase shifter 58 is bypassed, and the second light path controlling birefringent means 60 also becomes ordinary light, so that it proceeds straight. Then, the light is circularly polarized by the 波長 wavelength plate 68 and reaches the plane reflector 69.
[0055]
The light reflected by the plane reflector 69 remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 68 again. However, the polarization directions of both lights are parallel to the y-axis. Since both of these lights are extraordinary lights with respect to the second optical path controlling birefringent means 60, they are refracted in the -y direction and shifted to the first optical path. Next, the light passes through the second linear phase shifter 58 (the half-wave plate 58a) and the polarization direction becomes parallel to the x-axis. Both lights bypass the first linear phase shifter 54, and the left and right half-wave plates 67a and 67b rotate the polarization direction of the light in the left optical path by +45 degrees and the light in the right optical path rotates by -45 degrees. Return to the orthogonal relationship. Then, the Faraday rotators 66 rotate at +45 degrees, respectively. The two lights are combined by the polarization splitting / combining birefringent means 50, the ordinary light goes straight, and the extraordinary light is refracted in the -x direction, and is combined with the fourth port (P4) on the left side of the first stage.
[0056]
For the light input in the + z direction from the fourth port (P4) on the left side of the first stage, ordinary light goes straight through the polarization splitting / combining birefringent means 50, and the extraordinary light is refracted and separated in the + x direction while being polarized. The dispersion is compensated. In the 45-degree fixed Faraday rotator 66, the polarization direction is rotated by +45 degrees, and the pair of left and right half-wave plates 67a and 67b convert the polarization directions of both lights from orthogonal to parallel (parallel to the y-axis). You. The two lights bypass the first linear phase shifter 54 and become extraordinary light in the first optical path control birefringent means 56, so that they are refracted upward (+ y direction) and shifted to the second-stage optical path. Since the second linear phase shifter 58 is bypassed and the second optical path controlling birefringent means 60 also becomes abnormal light, it is refracted upward (+ y direction) and shifted to the third optical path. Then, the light is circularly polarized by the 波長 wavelength plate 68 and reaches the plane reflector 69.
[0057]
The reflected light from the plane reflector 69 remains circularly polarized, but returns to linearly polarized light by passing through the quarter-wave plate 68 again. However, the polarization direction is parallel to the x-axis. Since both of these lights are ordinary lights for the second optical path controlling birefringent means 60, they go straight as they are. Both lights bypass the second linear phase shifter 58, and also travel straight since the first optical path control birefringent means 56 is ordinary light, and also bypasses the first linear phase shifter 54. The left and right half-wave plates 67a and 67b rotate the polarization direction of the light in the left optical path by +45 degrees, and the light in the right optical path rotates by -45 degrees to have an orthogonal relationship, and the Faraday rotation is fixed at 45 degrees. Each child 66 rotates +45 degrees. The two lights are combined by the polarization splitting / combining birefringent means 50, the ordinary light goes straight, and the extraordinary light is refracted in the −x direction, and is combined with the first port (P1) on the third stage left side.
[0058]
In this manner, the light incident from the first port (P1) on the third stage left exits from the second port (P2) on the fourth stage left and enters from the second port (P2) on the second stage left. Light is emitted from the third port (P3) on the left side of the second stage. The light incident from the third port (P3) on the left side of the second stage exits from the fourth port (P4) on the left side of the first stage, and the light incident from the fourth port (P4) on the left side of the first stage is the third stage. The light exits from the first port (P1) on the left side. Therefore, a reflection optical circulator of a 4-port complete circulation type can be realized.
[0059]
Since the first port to the fourth port are arranged in a line at equal intervals in a different order, the input / output unit may have the same configuration as that of FIGS. 2 and 3 described above. As shown in FIG. 4, the polarization splitting / combining birefringent means may have a structure in which a polarization splitting / combining birefringent crystal is divided into two and a half-wave plate is inserted between them.
[0060]
FIG. 9 shows another embodiment of the reflection type optical circulator body. Since the basic configuration is similar to that of FIG. 8, for the sake of simplicity of description, the same members are denoted by the same reference numerals, and mainly the differences will be described. In this embodiment, only the polarization splitting / combining birefringent crystal 64 is used as the polarization splitting / combining birefringent means, and the polarization dispersion compensating birefringent crystal is not required. As the reflector of the polarization rotation reflector 82, a V-shaped reflector 63 that switches the optical path by two-stage reflection is used. The V-shaped reflector 83 has a 45-degree inclined V-groove surface as a reflection surface, and is installed in a direction in which the V-groove is parallel to the y-axis.
[0061]
The operation of the reflection type optical circulator body of this embodiment is almost the same as that of the example of FIG. 8 except for the reflection part. In the V-shaped reflector 83, the light in the left optical path becomes light in the right optical path by two-stage reflection on both surfaces of the V-groove, and the light in the right optical path similarly becomes the light in the left optical path by two-stage reflection on both surfaces of the V-groove. Become. As a result, the ordinary light and the extraordinary light are exchanged between the forward path and the return path in the polarization splitting / combining birefringent crystal 64. Accordingly, the polarization dispersion can be substantially compensated without using the polarization dispersion compensation birefringent crystal 65 as shown in FIG.
[0062]
FIG. 10 shows still another embodiment of the reflection type optical circulator body. Since the basic configuration is similar to that of FIG. 8, for the sake of simplicity of description, the same members are denoted by the same reference numerals, and mainly the differences will be described. In this embodiment, an optical path changing / reflecting means is used instead of the polarization rotating / reflecting means 62 shown in FIG. . A quarter-wave plate (or a 45-degree fixed Faraday rotator) is not required because the polarization is not rotated. The V-shaped reflector 84 has a 45-degree inclined V-groove surface as a reflection surface. In this case, unlike FIG. 9, the V-groove is installed in a direction parallel to the x-axis. .
[0063]
In the V-shaped reflector 84, the light in the second-stage optical path becomes the light in the fifth-stage optical path due to the two-stage reflection on both surfaces of the V-groove, and conversely, the light in the fifth-stage optical path becomes the light in the second-stage optical path. Become. The light of the third optical path becomes light of the fourth optical path by two-stage reflection on both sides of the V-groove, and the light of the fourth optical path becomes light of the third optical path. However, the left and right optical paths do not interchange here.
[0064]
In this configuration, light incident from the first port (P1) on the left side of the third stage exits from the second port (P2) on the left side of the first stage, and light incident from the second port (P2) on the left side of the first stage. Are emitted from the third port (P3) on the left side of the second stage. Light incident from the third port (P3) on the second stage left exits from the fourth port (P4) on the fourth stage left, and light incident from the fourth port (P4) on the fourth stage left is 3 The light exits from the first port (P1) on the left side of the stage. Therefore, although the positional relationship of the ports is different, a reflection type optical circulator of a 4-port complete circulation type can be realized.
[0065]
FIG. 11 shows still another embodiment of the reflection type optical circulator body. Since the basic configuration is similar to that of FIG. 10, the same reference numerals are given to the same members for simplification of the description, and mainly the differences will be described. In this embodiment, only the polarization splitting / combining birefringent crystal 64 is used as the polarization splitting / combining birefringent means. No birefringent crystal for polarization dispersion compensation is required. Therefore, as a light path changing / reflecting means, a quadrangular pyramid-shaped reflector 86 having a quadrangular pyramid-shaped (pyramid-shaped) reflecting surface that switches the light path by two-stage reflection and switches the ordinary light path and the extraordinary light path in the reciprocating path is used. I have. No quarter-wave plate (or 45-degree fixed Faraday rotator) is required. The pyramid-shaped reflector 86 is surrounded by four 45-degree inclined surfaces, and the inclined surfaces serve as reflection surfaces. The diagonal line of the opening is set so as to coincide with the x-axis and the y-axis. The pyramid-shaped reflector does not need to have an integral structure, and may have a structure in which a plurality of pieces are combined and joined.
[0066]
In the pyramid-shaped reflector 86, the light in the second-stage left optical path becomes the light in the fifth-stage right optical path due to the two-stage reflection on the facing surface, and conversely, the light in the fifth-stage left optical path becomes the light in the second-stage right optical path. It becomes light. The light on the third-stage left optical path becomes light on the fourth-stage right optical path due to two-stage reflection on the facing surface, and conversely, the light on the fourth-stage left optical path becomes light on the third-stage right optical path. Similarly, light on the right optical path becomes light on the left optical path. In this manner, the left and right optical paths are switched at the same time as the upper and lower optical paths are switched. As a result, the ordinary light and the extraordinary light are switched between the forward path and the return path in the polarization splitting / combining birefringent crystal 64, and the polarization dispersion can be substantially reduced without using the polarization dispersion compensating birefringent crystal. Can be compensated for.
[0067]
Also in this configuration, light incident from the first port (P1) on the third stage left exits from the second port (P2) on the first stage left, and enters from the second port (P2) on the first stage left. Are emitted from the third port (P3) on the left side of the second stage. Light incident from the third port (P3) on the second stage left exits from the fourth port (P4) on the fourth stage left, and light incident from the fourth port (P4) on the fourth stage left is 3 The light exits from the first port (P1) on the left side of the stage. Therefore, a reflection optical circulator of a 4-port complete circulation type can be realized.
[0068]
It goes without saying that the input / output unit shown in FIGS. 2 and 3 can be applied to the reflective optical circulator body shown in FIGS. The birefringence means for polarization separation / combination having the polarization dispersion compensation function shown in FIG. 4 can also be applied to the reflection type optical switch body shown in FIG.
[0069]
【The invention's effect】
The present invention is a reflection type optical device configured as described above, and utilizes an optical path reciprocating along the optical axis. The number of parts can be reduced, for example, only one birefringent crystal for separation / synthesis is required, and it can be manufactured at low cost and can be downsized. In addition, since the optical fiber exits in only one direction, there is an advantage that the device can be easily handled.
[0070]
According to the present invention, in the case of a reflection type optical switch, a 2 × 2 type (two inputs and two outputs) can be realized. The operation reliability is extremely high because it is a magneto-optical system and has no moving parts. In the case of a reflection type optical circulator, a four-port complete circulation type can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing one embodiment of a reflection type optical switch according to the present invention.
FIG. 2 is an explanatory diagram illustrating an example of an input / output unit.
FIG. 3 is an explanatory diagram showing another example of the input / output unit.
FIG. 4 is an explanatory view showing another example of a birefringent means for polarization separation / combination having a polarization dispersion compensation function.
FIG. 5 is an explanatory view showing another embodiment of the reflection type optical switch according to the present invention.
FIG. 6 is an explanatory view showing still another embodiment of the reflection type optical switch according to the present invention.
FIG. 7 is an explanatory view showing still another embodiment of the reflection type optical switch according to the present invention.
FIG. 8 is an explanatory view showing one embodiment of the reflection type optical circulator according to the present invention.
FIG. 9 is an explanatory view showing another embodiment of the reflection type optical circulator according to the present invention.
FIG. 10 is an explanatory view showing still another embodiment of the reflection type optical circulator according to the present invention.
FIG. 11 is an explanatory view showing still another embodiment of the reflection type optical circulator according to the present invention.
[Explanation of symbols]
10 Birefringence means for polarization separation / combination
12 Polarization rotating means
14 1st linear phase shifter
16. First birefringent means for optical path control
18 Second linear phase shifter
20 Birefringence means for controlling the second optical path
22 Polarization rotating reflection means
26 ± 45 degree variable Faraday rotator
28 1/4 wavelength plate
29 plane reflector

Claims

Polarization splitting / combining birefringent means for separating light in the same optical path having orthogonal polarization directions and combining light in different optical paths, and the relationship between orthogonal to parallel or parallel to orthogonal polarization directions of light in different optical paths Polarization rotation control means for converting the polarization direction and controlling the polarization direction; first and second birefringence means for controlling the optical path shift according to the polarization direction; The polarization rotation reflection means or the optical path change reflection means to reflect and change the reciprocating optical path, which is arranged along the optical axis in that order,
A first linear phase shifter that rotates the polarization direction of light in a part of the optical path by 90 degrees between the polarization rotation control means and the first optical path control birefringent means, and a first optical path control birefringence. A second linear phase shifter that rotates the polarization direction of light in another part of the optical path by 90 degrees between the unit and the second optical path controlling birefringent unit,
Four or more optical fibers are arranged in the input / output unit located on the opposite side to the polarization rotation reflection unit or the optical path changing reflection unit,
The reflection type optical device, wherein the polarization rotation control means comprises a combination of a ± 45 degree variable Faraday rotator and a pair of half-wave plates, and exhibits an optical switch function by switching a polarization direction.

Polarization splitting / combining birefringent means for separating light in the same optical path having orthogonal polarization directions and combining light in different optical paths, and the relationship between orthogonal to parallel or parallel to orthogonal polarization directions of light in different optical paths , A first and a second birefringent means for controlling the optical path according to the direction of polarization, and a polarization rotation reflection for rotating the plane of polarization 90 degrees back and forth for reflection. Means and an optical path changing reflecting means for changing and reflecting a reciprocating optical path, arranged along the optical axis in that order,
A first linear phase shifter for rotating the polarization direction of light in a part of the optical path by 90 degrees between the polarization rotating means and the first optical path controlling birefringent means, and a first optical path controlling birefringent means. A second linear phase shifter that rotates the polarization direction of light in another part of the optical path by 90 degrees is inserted between the second linear path retarder and the second optical path controlling birefringent means, respectively.
Four or more optical fibers are arranged in the input / output unit located on the opposite side to the polarization rotation reflection unit or the optical path changing reflection unit,
The reflection type optical device, wherein the polarization rotator comprises a combination of a 45-degree fixed Faraday rotator and a pair of half-wave plates, and has an optical circulator function.

3. The reflection type optical device according to claim 1, wherein the polarization rotation reflection means comprises a combination of a quarter-wave plate or a 45-degree fixed Faraday rotator and a plane reflector.

2. An optical path changing / reflecting means comprising a V-shaped reflector for switching an optical path by two-stage reflection, wherein the V-shaped reflecting surface is provided in a direction parallel to the direction of separation by the birefringent means for polarization separation / synthesis. Or the reflective optical device according to 2.

The birefringence means for polarization separation / combination is composed of a birefringence crystal for polarization separation / combination and a birefringence crystal for polarization dispersion compensation, and the polarization dispersion caused by the birefringence crystal for polarization separation / combination is compensated for by the birefringence for polarization dispersion compensation. 5. The reflection type optical device according to claim 1, wherein the reflection type optical device is compensated by a crystal.

A structure in which the polarization splitting / combining birefringent means divides the polarization splitting / combining birefringent crystal into two, inserts a half-wave plate between them, and replaces ordinary light and extraordinary light, thereby compensating for polarization dispersion. The reflective optical device according to claim 1, wherein:

The polarization rotating / reflecting means comprises a quarter-wave plate or a 45-degree fixed Faraday rotator, and a V-shaped reflector for switching the optical path by two-stage reflection, and the V-shaped reflection is provided by a polarization separating / combining birefringent means. 3. The reflection type optical device according to claim 1, wherein the reflection type optical device is installed in a direction orthogonal to the separation direction.

3. The reflection type optical device according to claim 1, wherein the optical path changing / reflecting means comprises a pyramid-shaped reflector which switches an optical path of a reciprocating path by two-stage reflection and switches an ordinary optical path and an abnormal optical path in the reciprocating path.

The input / output section is provided with four optical fibers, a four-core ferrule, a coupling lens common to each optical path, and obliquely emitted light from the coupling lens parallel to the optical axis and parallel to the optical axis. 9. The reflection type optical device according to claim 1, further comprising an optical path correction element for converting light into light obliquely incident on the coupling lens.

9. The reflection type according to claim 1, wherein the input / output unit comprises a fiber array in which four optical fibers are juxtaposed, and a collimator lens array in which lens elements are arranged corresponding to the respective optical fibers. Optical device.