JP4369363B2 - Bidirectional optical transmission system and optical transceiver - Google Patents

Bidirectional optical transmission system and optical transceiver Download PDF

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JP4369363B2
JP4369363B2 JP2004510151A JP2004510151A JP4369363B2 JP 4369363 B2 JP4369363 B2 JP 4369363B2 JP 2004510151 A JP2004510151 A JP 2004510151A JP 2004510151 A JP2004510151 A JP 2004510151A JP 4369363 B2 JP4369363 B2 JP 4369363B2
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optical
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transmission
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JPWO2003103194A1 (en
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和利 加藤
由明 山林
昇 石原
俊一 東野
由一 千葉
安弘 鈴木
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NTT Electronics Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2587—Arrangements specific to fibre transmission using a single light source for multiple stations

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Description

技術分野
本発明は、主装置と従装置との間を光ファイバで双方向伝送する双方向光伝送方式、及び光送受信装置に関する。
背景技術
従来の双方向光伝送方式の構成を図１６に示す。図１６において、１５−１、１５−２は光ファイバ、４１は主装置の光送信回路、４２は主装置の光受信回路、４３は光受信部、４４は光送信部、４８は従装置の光受信回路、４９は従装置の光送信回路である。
主装置と従装置で双方向伝送する方式の構成について図１６（ａ）で説明する。図１６は主装置と従装置との間を２芯の光ファイバで双方向伝送する双方向光伝送方式である。即ち、図１６（ａ）に示すように、主装置の光送信回路４１と従装置の光受信回路４８との間、及び従装置の光送信回路４９と主装置の光受信回路４２との間は２芯の光ファイバ１５−１と１５−２で接続され、双方向伝送する。図１６（ａ）において、主装置の光送信回路４１は光ファイバ１５−１を通して下り光信号を送信し、従装置の光受信回路４８はその下り光信号を受信する。従装置の光送信回路４９は光ファイバ１５−２を通して上り光信号を送信し、主装置の光受信回路４２はその上り光信号を受信する。図１６（ｂ）には、従装置の光受信回路４８と光送信回路４９のヘッドエンド構成を示す。図１６（ｂ）において、従装置の光受信回路４８では、光ファイバ１５−１を介して受信した下り光信号は、光受信部４３で検出され、検出された下り信号は光受信回路４８内で信号処理される。一方、上り信号は光送信部４４で上り光信号に変調される。変調された上り光信号は光ファイバ１５−２を通して送信される。
上り光信号、又は下り光信号の送信と受信の動作を図１７に示す。図１７において、主装置の光送信回路で、下り信号の駆動電流により発光素子を駆動する（図１７（ａ））。発光素子の光出力は駆動電流に対して、ほぼ直線的な関係にある（図１７（ｂ））。その結果、主装置の光送信回路は下り信号の波形に近い下り光信号出力を送信する（図１７（ｃ））。従装置の光受信回路では、光受信回路入力の信号成分に対して閾値を設定して、下り信号を検出する（図１７（ｄ））。従装置の光送信回路と主装置の光受信回路の動作も同様である。即ち、主装置の光送信回路と従装置の光送信回路はそれぞれ発光素子を持つ必要がある。
従来の他の双方向伝送方式の構成を図１８に示す。本構成は、主装置と複数の従装置で２芯光ファイバ双方向・波長多重マルチポイント伝送する双方向光伝送方式である。図１８において、４１−１〜４１−Ｎは主装置の光送信回路、４２−１〜４２−Ｎは主装置の光受信回路、４５−１、４５−２は主装置の波長多重回路、１５−１、１５−２は光ファイバ、１６−１、１６−２は光ファイバの途中に設けられた波長多重回路、４８−１〜４８−Ｎは従装置の光受信回路、４９−１〜４９−Ｎは従装置の光送信回路である。ここでは、２以上の複数を表すときに記号Ｎを用いた。例えば、光送信回路４１−１〜４１−Ｎは２以上の複数の光送信回路を表す。
主装置と複数の従装置で双方向伝送する方式の構成について説明する。図１８において、主装置の複数の光送信回路４１−１〜４１−Ｎは下り信号で変調したそれぞれの下り光信号をそれぞれ予め割り当てられた波長（λ１、λ２・・λＮ）で主装置の波長多重回路４５−１に向けて送信する。波長多重回路４５−１は、複数の光送信回路から送信された、異なる波長の下り光信号を光ファイバ１５−１に波長多重する。光ファイバ１５−１の途中に設けられた波長多重回路１６−１は、それぞれの下り光信号を波長に応じてそれぞれの従装置に向けて波長分離する。それぞれの従装置の光受信回路４８−１〜４８−Ｎは光ファイバ１５−１を通して受信した下り光信号から信号成分を検出する。一方、それぞれの従装置の光送信回路４９−１〜４９−Ｎは上り信号で変調した上り光信号を光ファイバ１５−２に送信する。光ファイバ１５−２の途中に設けられた波長多重回路１６−２は複数の光送信回路４９−１〜４９−Ｎから送信された、それぞれ予め割り当てられた波長（λ１、λ２、・・λＮ）の上り光信号を主装置に向けて波長多重する。主装置の波長多重回路４５−２は複数の従装置の光送信回路４９−１〜４９−Ｎから送信された、それぞれ予め割り当てられた波長（λ１、λ２、・・λＮ）の上り光信号を波長毎に主装置の光受信回路４２−１〜４２−Ｎに向けて波長分離する。主装置の複数の光受信回路４２−１〜４２−Ｎは、それぞれ受信した上り光信号から上り信号を検出する。
ここで、従装置の光送信回路４９−１〜４９−Ｎはそれぞれ、所定の波長の上り光信号を送信しなければならない。それぞれの従装置の光送信回路４９−１〜４９−Ｎはそれぞれ発光素子を持つ必要があり、さらに、これらの発光素子の波長を高精度に制御したり、維持したりする必要がある。従装置は一般にそれぞれ異なる場所に分散配置されるため、環境温度等が異なる。環境温度の変化により発光素子の波長が所定の値から変移すると、光ファイバ１５−２の途中にある波長多重回路１６−２や、主装置の波長多重回路４５−２において、光損失が増大する。さらに、変移が大きい場合は伝送ができなくなる虞があった。
本発明は、このような問題を解決するために、従装置の光送信回路で発光素子を不要とし、また、従装置の光送信回路で発光素子の波長を高精度に制御したり、維持したりすることを不要とすることを目的とする。
なお、光信号を処理する光部品として、従来は、半導体光増幅回路（例えば、Ｔ．Ｍｕｋａｉ ａｎｄ Ｔ．Ｓａｉｔｏｈ，“５．２ｄＢ ｎｏｉｓｅ ｆｉｇｕｒｅ ｉｎ ａ １．５ｕｍ ＩｎＧａＡｓＰ ｔｒａｖｅｌｉｎｇ ｗａｖｅ ｌａｓｅｒ ａｍｐｌｉｆｉｅｒ”，Ｅｌｅｃｔｒｏｎ．Ｌｅｔｔ．，Ｖｏｌ．２３，Ｎｏ，５，ｐｐ．２１６−２１８（１９８７））がある。これは、入力光信号と出力光信号の波形がリニアーな関係となる半導体光増幅回路である。
発明の開示
前述した目的を達成するために、本願第一の発明は、主装置と従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向伝送する双方向光伝送方式であって、前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を前記第一の光ファイバに向けて送信する光送信回路と、前記第二の光ファイバを通して受信した上り光信号から上り信号を検出する光受信回路とを備え、前記従装置は、前記第一の光ファイバを通して受信した前記下り光信号から前記信号成分を検出する光受信回路と、前記受信した下り光信号の一部を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記第二の光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式である。
本願第二の発明は、主装置と従装置との間を１芯の光ファイバで方向多重双方向伝送する双方向光伝送方式であって、前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を前記光ファイバに向けて送信する光送信回路と、前記光ファイバを通して受信した上り光信号から上り信号を検出する光受信回路とを備え、前記従装置は、前記光ファイバを通して受信した前記下り光信号から前記信号成分を検出する光受信回路と、前記受信した下り光信号の一部を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式である。
本願第三の発明は、本願第二の発明である主装置と従装置との間を１芯の光ファイバで方向多重双方向伝送する双方向光伝送方式において、前記飽和増幅・減衰回路が、半導体光増幅器であって、前記下り光信号の入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、前記下り光信号の入射端面から送出する反射型構成であることを特徴とする双方向光伝送方式である。
本願第四の発明は、主装置と複数の従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向・波長多重マルチポイント伝送する双方向光伝送方式であって、前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を前記第一の光ファイバに向けて送信する複数の光送信回路と、前記第二の光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する複数の光受信回路とを備え、前記複数の従装置は、それぞれ、前記第一の光ファイバを通して受信した前記下り光信号から前記信号成分を検出する光受信回路と、それぞれ、前記受信した下り光信号の一部を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記第二の光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式である。
本願第五の発明は、主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式であって、前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を前記光ファイバに向けて送信する複数の光送信回路と、前記光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する複数の光受信回路とを備え、前記複数の従装置は、それぞれ、前記光ファイバを通して受信した前記下り光信号から前記信号成分を検出する光受信回路と、それぞれ、前記受信した下り光信号の一部を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式である。
本願第六の発明は、本願第五の発明である主装置と複数の従装置を１芯の光ファイバで方向多重双方向―波長多重マルチポイント伝送する双方向光伝送方式において、前記飽和増幅・減衰回路が、半導体光増幅器であって、前記下り光信号の入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、前記下り光信号の入射端面から送出する反射型構成であることを特徴とする双方向光伝送方式である。
本願第七の発明は、主装置と複数の従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式であって、前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を従装置毎の波長と時間領域に分離して前記第一の光ファイバに向けて送信する光送信回路と、前記第二の光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する少なくとも１の光受信回路とを備え、前記複数の従装置は、それぞれ、前記第一の光ファイバを通して受信した前記下り光信号から前記信号成分を検出する光受信回路と、それぞれ、前記受信した下り光信号の一部を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記第二の光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式である。
本願第八の発明は、本願第七の発明である主装置と複数の従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式において、前記光送信回路に光出力の波長を従装置毎の波長に可変できる波長可変光源を用いたことを特徴とする双方向光伝送方式である。
本願第九の発明は、主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式であって、前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を従装置毎の波長と時間領域に分離して前記光ファイバに向けて送信する光送信回路と、前記光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する少なくとも１の光受信回路とを備え、前記複数の従装置は、それぞれ、前記光ファイバを通して受信した前記下り光信号から前記信号成分を検出する光受信回路と、それぞれ、前記受信した下り光信号の一部を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式である。
本願第十の発明は、本願第九の発明である主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式において、前記飽和増幅・減衰回路が、半導体光増幅器であって、前記下り光信号の入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、前記下り光信号の入射端面から送出する反射型構成であることを特徴とする双方向光伝送方式である。
本願第十一の発明は、本願第九の発明である主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式において、前記光送信回路に光出力の波長を従装置毎の波長に可変できる波長可変光源を用いたことを特徴とする双方向光伝送方式である。
本願第十二の発明は、受信した第一の光信号の一部を飽和増幅・減衰回路によって第二の送信信号で変調した第二の光信号を光ファイバに向けて送信する光送信回路を備える光送受信装置に対して、第一の送信信号で変調した信号成分にバイアス成分を重畳した第一の光信号を送信する光送信回路と、光ファイバを通して受信した前記第二の光信号から信号成分を検出する光受信回路とを備える光送受信装置である。
本願第十三の発明は、信号で変調した信号成分にバイアス成分を重畳した光信号を、光ファイバを通して受信する光受信回路と、前記受信した光信号の一部を飽和増幅・減衰回路によって送信する信号で変調して光ファイバに向けて送信する光送信回路とを備える光送受信装置である。
本願第十四の発明は、本願第十二の発明である光送受信装置において、前記バイアス成分が前記信号成分の５０％以上、好ましくは１００％以上であることを特徴とする光送受信装置である。
本願第十五の発明は、本願第十三の発明である光送受信装置において、前記飽和増幅・減衰回路が、制御電流によって増幅度を制御する増幅部と送信する信号によって光信号を変調する変調部とを有する半導体光増幅器であることを特徴とする光送受信装置である。
本願第十六の発明は、本願第十三の発明である光送受信装置において、前記飽和増幅・減衰回路が、制御電流によって飽和させる増幅部と送信する信号によって光信号を吸収する変調部とを有する半導体光素子であることを特徴とする光送受信装置である。
なお、これらの各構成は、可能な限り組み合わせることができる。
ここで、飽和増幅・減衰回路は、光入力が小さい範囲では線形増幅するが、光入力が大きくなると増幅度は飽和し、光入力レベルに関わらず光出力が一定となる回路である。さらに、増幅度が制御可能であり、増幅度を高くして飽和型増幅させたり、逆に増幅度を抑えて減衰させたりすることができる。なお、飽和増幅・減衰回路での減衰には単に増幅度を小さくしたものも含まれる。
２芯光ファイバ双方向伝送とは、下り光信号の伝送に第一の光ファイバを、上り光信号の伝送に第二の光ファイバを使用して双方向伝送する技術をいう。１芯光ファイバ方向多重双方向伝送とは、下り光信号と上り光信号の伝送に同じ光ファイバを使用し、同じ波長を有する下り光信号と上り光信号の合流、分岐に光合分岐回路を利用して双方向伝送する技術をいう。
２芯光ファイバ双方向・波長多重マルチポイント伝送とは、主装置と複数の従装置を１対Ｎのマルチポイント接続した伝送方式において、下り光信号の伝送に第一の光ファイバを、上り光信号の伝送に第二の光ファイバを使用し、上り光信号と下り光信号にそれぞれ従装置ごとに異なる波長を割り当てて、主装置と光ファイバの途中に設けられた波長多重回路の間を波長多重伝送して双方向伝送する技術をいう。１芯光ファイバ方向多重双方向・波長多重マルチポイント伝送とは、主装置と複数の従装置を１対Ｎのマルチポイント接続した伝送方式において、下り光信号の伝送と上り光信号の伝送に同じ光ファイバを使用し、上り光信号と下り光信号は同じ波長で、かつ従装置ごとに異なる波長を割り当てて、主装置と光ファイバの途中に設けられた波長多重回路の間を波長多重伝送して双方向伝送する技術をいう。
２芯光ファイバ双方向・波長時分割多重マルチポイント伝送とは、主装置と複数の従装置を１対Ｎのマルチポイント接続した伝送方式において、下り光信号の伝送に第一の光ファイバを、上り光信号の伝送に第二の光ファイバを使用し、上り光信号と下り光信号にそれぞれ従装置ごとに異なる波長と時間領域を割り当てて、主装置と光ファイバの途中に設けられた波長多重回路の間を波長多重伝送して双方向伝送する技術をいう。１芯光ファイバ方向多重双方向・波長時分割多重マルチポイント伝送とは、主装置と複数の従装置を１対Ｎのマルチポイント接続した伝送方式において、下り光信号の伝送と上り光信号の伝送に同じ光ファイバを使用し、上り光信号と下り光信号は同じ波長で、かつ従装置ごとに異なる波長と時間領域を割り当てて、主装置と光ファイバの途中に設けられた波長多重回路の間を波長多重伝送して双方向伝送する技術をいう。
また、ここでは、下りとは、主装置から従装置への信号の流れをいい、上りとは、従装置から主装置への信号の流れをいう。
発明を実施するための最良の形態
以下、本発明を実施するための形態について詳細に説明するが、本発明はこれらの形態に限定して解釈されない。
（実施の形態１）
本実施の形態は、２芯光ファイバ双方向伝送する双方向光伝送方式である。本発明の実施の形態の構成を図１に示す。図１において、１１は主装置の光送信回路、１２は主装置の光受信回路、１５−１、１５−２は光ファイバ、１８は従装置の光受信回路、１９は従装置の光送信回路、２１は光分岐回路、２２は光受信部、２３は駆動部、２４は飽和増幅・減衰回路としての出力強度飽和型増幅変調器である。
主装置と従装置で双方向伝送する方式の構成について図１（ａ）で説明する。図１（ａ）において、主装置の光送信回路１１は光ファイバ１５−１を通して下り光信号を送信し、従装置の光受信回路１８は当該下り光信号を受信する。従装置の光送信回路１９は光ファイバ１５−２を通して上り光信号を送信し、主装置の光受信回路１２は当該上り光信号を受信する。図１（ｂ）には、従装置の光受信回路１８と光送信回路１９のヘッドエンド構成を示す。図１（ｂ）において、従装置の光受信回路１８では、光ファイバ１５−１を介して受信した下り光信号を、光分岐回路２１で２つに分岐する。分岐された下り光信号を光受信部２２で検出し、検出された下り信号を光受信回路１８内で信号処理する。出力強度飽和型増幅変調器２４は分岐された下り光信号の一部を駆動部２３からの上り信号で飽和増幅、減衰し、上り光信号に変調する。変調された上り光信号は光ファイバ１５−２を介して送信される。
次に、本構成での動作を説明する。下り光信号の送信と受信の動作を図２に、上り光信号の送信と受信の動作を図３に示す。図２において、主装置の光送信回路では、下り信号で変調した信号成分にバイアス成分を重畳し、発光素子の駆動電流とする（図２（ａ））。発光素子の光出力は駆動電流に対して、ほぼ直線的な関係にある（図２（ｂ））。その結果、主装置の光送信回路は駆動電流の波形に近い下り光信号出力を送信する（図２（ｃ））。従装置の光受信回路では、光受信回路入力の信号成分に対して閾値を設定して、下り信号の信号成分を検出する（図２（ｄ））。ここでは、下り信号は強度変調されて送受信する例を示したが、位相変調や周波数変調等の変調形式であってもよい。これらの変調形式でも、主装置の光送信回路では、信号成分にバイアス成分を重畳して送信し、従装置の光受信回路では信号成分から下り光信号成分を検出する。
図３において、下り光信号の一部を分岐して出力強度飽和型増幅変調器に入力する（図３（ａ））。出力強度飽和型増幅変調器は、光入力が小さい範囲では線形増幅するが、光入力が大きくなると増幅度は飽和し、光入力レベルに関わらず光出力が一定となる（図３（ｂ））。さらに、出力強度飽和型増幅変調器は、制御端子から増幅度を制御可能な増幅変調器であり、増幅度を高くして飽和型増幅させたり、逆に増幅度を抑えて減衰させたりすることができる（図３（ｂ））。この出力強度飽和型増幅変調器に分岐した下り光信号を入力すると、下り光信号は信号成分にバイアス成分が重畳されているため、飽和型増幅によりバイアス成分は増幅され、信号成分は圧縮される（図３（ｃ））。さらに、出力強度飽和型増幅変調器の制御端子に従装置の光送信回路の駆動部からの上り信号を入力すると、上り信号に応じて増幅度が制御される結果、飽和型増幅時にはバイアス成分が増幅されるとともに信号成分が圧縮された高出力の光信号が出力され、増幅度が抑えられた減衰時にはバイアス成分と信号成分が共に圧縮された低出力の光信号が出力される（図３（ｃ））。主装置の光受信回路では、光受信回路入力の信号成分に対して閾値を設定して、上り光信号の信号成分を検出する（図３（ｄ））。
ここで、前記バイアス成分が前記信号成分の５０％以上であると、強度変調した信号のマーク率が５０％デューティの場合に、前記バイアス成分の光電力が前記信号成分の平均光電力以上になり、出力強度飽和型増幅変調器でバイアス成分を増幅することが容易となる。前記バイアス成分が前記信号成分の１００％以上であると、前記バイアス成分の光電力が前記信号成分のピーク光電力以上になり、出力強度飽和型増幅変調器でバイアス成分を増幅することが一層容易となる。以下の実施の形態でも同様である。
以上説明したように、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を送信することにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
（実施の形態２）
本実施の形態は、１芯の光ファイバで方向多重双方向伝送する双方向光伝送方式である。本発明の実施の形態の構成を図４に示す。図４において、１１は主装置の光送信回路、１２は主装置の光受信回路、１４は主装置の光合分岐回路、１５は光ファイバ、１７は従装置の光合分岐回路、１８は従装置の光受信回路、１９は従装置の光送信回路、２１は光分岐回路、２２は光受信部、２３は駆動部、２４は飽和増幅・減衰回路としての出力強度飽和型増幅変調器である。
主装置と従装置で双方向伝送する方式の構成について図４（ａ）で説明する。図４（ａ）において、主装置の光送信回路１１は主装置の光合分岐回路１４と光ファイバ１５を通して下り光信号を送信し、従装置の光受信回路１８は従装置の光合分岐回路１７を通して前記下り光信号を受信する。従装置の光送信回路１９は従装置の光合分岐回路１７と光ファイバ１５を通して上り光信号を送信し、主装置の光受信回路１２は主装置の光合分岐回路を通して前記上り光信号を受信する。図４（ｂ）には、従装置の光受信回路１８と光送信回路１９のヘッドエンド構成を示す。図４（ｂ）において、従装置の光受信回路１８では、光分岐回路２１で従装置の光合分岐回路１７を介して受信した下り光信号を２つに分岐する。分岐した下り光信号を光受信部２２で検出し、検出した下り信号を光受信回路１８内で信号処理する。出力強度飽和型増幅変調器２４は分岐した下り光信号の一部を駆動部２３からの上り信号で飽和増幅、減衰して上り光信号に変調する。変調された上り光信号は従装置の光合分岐回路１７と光ファイバ１５を介して送信される。光合分岐回路１７と光分岐回路２１は一体で構成してもよい。
次に、本構成での動作を説明する。下り光信号の送信と受信の動作は図２と、上り光信号の送信と受信の動作は図３と同様である。異なるのは、主装置と従装置にそれぞれ光合分岐回路１４、１７を備えることにより、１芯の光ファイバで双方向伝送が可能になっていることである。これらの光合分岐回路によって、上り光信号と下り光信号が分離される。光合分岐回路には、方向性光結合回路や光サーキュレータ等が適用できる。主装置の光送信回路及び光受信回路、並びに従装置の光送信回路及び光受信回路は、実施の形態１と同じ動作をする。
１芯の光ファイバで方向多重双方向伝送する双方向光伝送方式においては、下り信号と上り信号が同一波長で同一光ファイバ上を伝送される。そのため、主装置で上り信号を受信する場合、光ファイバの途中で反射した下り信号と相互干渉する場合がある。本実施の形態では、発光素子の駆動電流を制御して、下り信号に信号成分が重畳しているため、下り信号光のスペクトル幅を広くすることもできる。信号光のスペクトル幅が広くなると、上り信号と線路途中で反射した下り信号との相互干渉が抑制され、上り信号に加算する雑音を抑圧することが可能となる。
従って、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバに送信する構成とすることにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
また、従装置の光送信回路は出力強度飽和型増幅変調器によって、下り光信号と同じ波長の上り光信号を送信するため、光合分岐回路の特性に波長依存性があっても、上り光信号の波長を高精度に制御したり、維持したりする必要はなくなった。
さらに、本従装置の光送信回路において、半導体光増幅器の出力強度飽和増幅機能を広範囲の波長にわたって動作させると、波長ごとに従装置の種類が異なるのではなく、同一種の従装置を任意の従装置に適用することができる。即ち、従装置間で、相互運用性（インタオペラビリティ）を確保することが可能となった。
（実施の形態３）
本実施の形態は、主装置と複数の従装置で２芯光ファイバ双方向・波長多重マルチポイント伝送する双方向光伝送方式である。本発明の実施の形態の構成を図５に示す。図５において、１１−１〜１１−Ｎは主装置の光送信回路、１２−１〜１２−Ｎは主装置の光受信回路、１３−１、１３−２は主装置の波長多重回路、１５−１、１５−２は光ファイバ、１６−１、１６−２は光ファイバの途中に設けられた波長多重回路、１８−１〜１８−Ｎは従装置の光受信回路、１９−１〜１９−Ｎは従装置の光送信回路である。ここでは、２以上の複数を表すときに記号Ｎを用いた。例えば、光送信回路１１−１〜１１−Ｎは２以上の複数の光送信回路を表す。図５において、下方向の矢印は下り、上方向の矢印は上りの伝送方向を表す。
主装置と複数の従装置で双方向伝送する方式の構成について説明する。図５において、主装置の複数の光送信回路１１−１〜１１−Ｎは下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を主装置の波長多重回路１３−１に送信する。光送信回路１１−１〜１１−Ｎの光信号の波長はそれぞれ予め割り当てられている（λ１、λ２、・・λＮ）。波長多重回路１３−１は、複数の光送信回路１１−１〜１１−Ｎから送信された、異なる波長（λ１〜λＮ）の下り光信号を光ファイバ１５−１に波長多重する。光ファイバ１５−１の途中に設けられた波長多重回路１６−１は、それぞれの下り光信号を波長に応じてそれぞれの従装置に向けて波長分離する。それぞれの従装置の光受信回路１８−１〜１８−Ｎは光ファイバ１５−１を通して受信した下り光信号から信号成分を検出する。それぞれの従装置の光送信回路１９−１〜１９−Ｎは受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバ１５−２に送信する。従装置の光送信回路の出力強度飽和型増幅変調器で下り光信号を飽和増幅するため、送信する波長は下り光信号と同じである。光ファイバ１５−２の途中に設けられた波長多重回路１６−２は複数の光送信回路１９−１〜１９−Ｎから送信された、異なる波長（λ１〜λＮ）の上り光信号を主装置に向けて波長多重する。主装置の波長多重回路１３−２は複数の従装置の光送信回路１９−１〜１９−Ｎから送信された、異なる波長（λ１〜λＮ）の上り光信号を波長毎に主装置の光受信回路１２−１〜１２−Ｎに向けて波長分離する。主装置の複数の光受信回路１２−１〜１２−Ｎは受信した上り光信号から上り信号を検出する。
次に、本構成での動作を説明する。下り光信号の送信と受信の動作は図２と、上り光信号の送信と受信の動作は図３と同様である。異なるのは、主装置に波長多重回路１３−１と１３−２、光ファイバの途中に波長多重回路１６−１と１６−２を備えることにより、主装置と複数の従装置で波長多重マルチポイント伝送が可能になっていることである。波長多重回路１６−１と１６−２によって、上り光信号と下り光信号が多重、分離される。主装置の光送信回路及び光受信回路、並びに従装置の光送信回路及び光受信回路は、実施の形態１と同じ動作をする。
従って、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を送信する構成とすることにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
また、従装置の光送信回路は出力強度飽和型増幅変調器によって、下り光信号と同じ波長の上り光信号を送信するため、波長多重回路の波長特性に対して従装置側の送信回路では上り光信号の波長を高精度に一致させたり、維持したりする必要はなくなった。
さらに、本従装置の光送信回路において、半導体光増幅器の出力強度飽和増幅機能を広範囲の波長にわたって動作させると、波長ごとに従装置の種類が異なるのではなく、同一種の従装置を任意の従装置に適用することができる。即ち、従装置間で、相互運用性（インタオペラビリティ）を確保することが可能となった。
（実施の形態４）
本実施の形態は、主装置と複数の従装置で１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式である。本発明の実施の形態の構成を図６に示す。図６において、１１−１〜１１−Ｎは主装置の光送信回路、１２−１〜１２−Ｎは主装置の光受信回路、１３−１、１３−２は主装置の波長多重回路、１４は主装置の光合分岐回路、１５は光ファイバ、１６は光ファイバの途中に設けられた波長多重回路、１７−１〜１７−Ｎは従装置の光合分岐回路、１８−１〜１８−Ｎは従装置の光受信回路、１９−１〜１９−Ｎは従装置の光送信回路である。ここでは、２以上の複数を表すときに記号Ｎを用いた。例えば、光送信回路１１−１〜１１−Ｎは２以上の複数の光送信回路を表す。図６において、下方向の矢印は下り、上方向の矢印は上り、上下両方向の矢印は上り下りの双方向の伝送方向を表す。
主装置と複数の従装置で双方向伝送する方式の構成について説明する。図６において、主装置の複数の光送信回路１１−１〜１１−Ｎは下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を主装置の波長多重回路１３−１に向けて送信する。光送信回路１１−１〜１１−Ｎの下り光信号の波長は予め割り当てられている（λ１、λ２、・・λＮ）。主装置の波長多重回路１３−１は、複数の光送信回路１１−１〜１１−Ｎから送信された、異なる波長（λ１〜λＮ）の下り光信号を波長多重する。主装置の光合分岐回路１４はこれらの下り光信号を光ファイバ１５−１に合流させる。光ファイバ１５の途中に設けられた波長多重回路１６は、それぞれの下り光信号を波長に応じてそれぞれの従装置に向けて波長分離する。それぞれの従装置の光合分岐回路１７−１〜１７−Ｎは下り光信号を対応する光受信回路１８−１〜１８−Ｎに分岐する。光受信回路１８−１〜１８−Ｎは受信した下り光信号から信号成分を検出する。
それぞれの従装置の光送信回路１９−１〜１９−Ｎは受信した下り光信号の一部を光分岐回路（図示せず）によって分岐して、飽和増幅・減衰回路によって上り信号で変調した上り光信号を送信する。前記下り光信号の一部を分岐する光分岐回路と前記光合分岐回路１７を一体で構成してもよい。下り光信号は従装置の光送信回路の出力強度飽和型増幅変調器によって飽和増幅されるため、送信する波長は下り光信号と同じである。従装置の光合分岐回路１７−１〜１７−Ｎは上り光信号を光ファイバ１５に合流させる。光ファイバ１５の途中に設けられた波長多重回路１６は複数の光送信回路１９−１〜１９−Ｎから送信された、異なる波長（λ１〜λＮ）の上り光信号を主装置に向けて波長多重する。主装置の波長多重回路１３−２は複数の従装置の光送信回路１９−１〜１９−Ｎから送信された、異なる波長（λ１〜λＮ）の上り光信号を波長毎に主装置の光受信回路１２−１〜１２−Ｎに向けて波長分離する。主装置の複数の光受信回路１２−１〜１２−Ｎは受信した上り光信号からそれぞれ上り信号を検出する。
次に、本構成での動作を説明する。下り光信号の送信と受信の動作は図２と、上り光信号の送信と受信の動作は図３と同様である。異なるのは、主装置に波長多重回路１３−１と１３−２、及び光合分岐回路１４を、光ファイバの途中に波長多重回路１６を、複数の従装置に光合分岐回路１７−２〜１７−Ｎを備えることにより、主装置と複数の従装置で１芯光ファイバ方向多重双方向・波長多重マルチポイント伝送が可能になっていることである。これらの波長多重回路と光合分岐回路によって、複数の上り光信号と複数の下り光信号が多重、又は分離される。主装置の光送信回路及び光受信回路、並びに従装置の光送信回路及び光受信回路は、実施の形態１と同じ動作をする。
１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式においては、下り信号と上り信号が同一波長で同一光ファイバ上を伝送される。そのため、主装置で上り信号を受信する場合、光ファイバの途中で反射した下り信号と相互干渉する場合がある。本実施の形態では、発光素子の駆動電流を制御して、下り信号に信号成分が重畳しているため、下り信号光のスペクトル幅を広くすることもできる。信号光のスペクトル幅が広くなると、上り信号と線路途中で反射した下り信号との相互干渉が抑制され、上り信号に加算する雑音を抑圧することが可能となる。
従って、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバに送信する構成とすることにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
また、従装置の光送信回路は出力強度飽和型増幅変調器によって、下り光信号と同じ波長の上り光信号を送信するため、波長多重回路の波長特性に対して従装置側の送信回路では上り光信号の波長を高精度に一致させたり、維持したりする必要はなくなった。
さらに、本従装置の光送信回路において、半導体光増幅器の出力強度飽和増幅機能を広範囲の波長にわたって動作させると、波長ごとに従装置の種類が異なるのではなく、同一種の従装置を任意の従装置に適用することができる。即ち、従装置間で、相互運用性（インタオペラビリティ）を確保することが可能となった。
（実施の形態５）
本実施の形態は、主装置と複数の従装置で１芯光ファイバ方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式である。本発明の実施の形態の構成を図７に示す。図７において、１１−１〜１１−Ｎは主装置の光送信回路、１２−１〜１２−Ｎは主装置の光受信回路、１３は主装置の波長多重回路、１４−１〜１４−Ｎは主装置の光合分岐回路、１５は光ファイバ、１６は光ファイバの途中に設けられた波長多重回路、１７−１〜１７−Ｎは従装置の光合分岐回路、１８−１〜１８−Ｎは従装置の光受信回路、１９−１〜１９−Ｎは従装置の光送信回路である。ここでは、２以上の複数を表すときに記号Ｎを用いた。例えば、光送信回路１１−１〜１１−Ｎは２以上の複数の光送信回路を表す。図７において、下方向の矢印は下り、上方向の矢印は上り、上下両方向の矢印は上り下りの双方向の伝送方向を表す。
主装置と複数の従装置で双方向伝送する方式の構成と動作について説明する。図７において、実施の形態４との相違点は、主装置の光合分岐回路と波長多重回路の配置である。つまり、実施の形態４とは、主装置の波長多重回路と光合分岐回路との接続が逆になっている。光合分岐回路と波長多重回路は共に線形回路のため、接続の順番を入れ替えても同じ動作となる。光合分岐回路と波長多重回路の光損失、必要個数によって実施の形態４と実施の形態５のいずれかが選択される。
１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式においては、下り信号と上り信号が同一波長で同一光ファイバ上を伝送される。そのため、主装置で上り信号を受信する場合、光ファイバの途中で反射した下り信号と相互干渉する場合がある。本実施の形態では、発光素子の駆動電流を制御して、下り信号に信号成分が重畳しているため、下り信号光のスペクトル幅を広くすることもできる。信号光のスペクトル幅が広くなると、上り信号と線路途中で反射した下り信号との相互干渉が抑制され、上り信号に加算する雑音を抑圧することが可能となる。
従って、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバに送信する構成とすることにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
また、従装置の光送信回路は出力強度飽和型増幅変調器によって、下り光信号と同じ波長の上り光信号を送信するため、波長多重回路の波長特性に対して従装置側の送信回路では上り光信号の波長を高精度に一致させたり、維持したりする必要はなくなった。
さらに、本従装置の光送信回路において、半導体光増幅器の出力強度飽和増幅機能を広範囲の波長にわたって動作させると、波長ごとに従装置の種類が異なるのではなく、同一種の従装置を任意の従装置に適用することができる。即ち、従装置間で、相互運用性（インタオペラビリティ）を確保することが可能となった。
（実施の形態６）
出力強度飽和型増幅変調器を備える光送受信装置について説明する。通常の半導体光増幅器は、入力光に対して出力光が線形増幅される領域を使用して光増幅する。一方、出力強度飽和型増幅変調器は、半導体光増幅器において入力光に対して出力光の強度が飽和増幅する領域を積極的に利用し、かつ変調も行うようにしたものである。出力強度飽和型増幅変調器は入力光を増幅するだけのため、出力光の波長は入力光に追随する。
出力強度飽和型増幅変調器の概略構造を図８に示す。図８において、３１は出力強度飽和型増幅変調器、３３は増幅変調部、３４は出射口である。図８において、入力光に対して、増幅変調部３３で制御端子（図示せず）からの入力信号により飽和増幅と減衰を行う。飽和増幅と減衰により、増幅変調された出力光は出射口３４から出力される。このように、飽和増幅と減衰により、入力信号で変調することができる。
増幅器としての増幅度は増幅変調部に設けられた電極への入力信号電流の大小によって決定される。入力信号電流を大きくすると、増幅度も大きくなる。また、入力光に対して出力光の強度が飽和する飽和点も同時に大きくなる。入力信号電流を小さくすると入力光の増幅度が小さく、あるいは減衰することになる。入力信号電流によって光位相を変調すると位相変調、又は光周波数を変調すると周波数変調することになる。ここで、飽和増幅され、変調された出力光の波長は、出力強度飽和型増幅変調器への入力光の波長と同じである。
他の出力強度飽和型増幅変調器の概略構造を図９に示す。前述の出力強度飽和型増幅変調器は、１の電極で飽和増幅と変調を行った。本出力強度飽和型増幅変調器は飽和増幅部と変調部を分離したものである。従って、制御端子も増幅制御端子と変調入力端子に分離する。
図９において、３２は出力強度飽和型増幅変調器、３５は増幅部、３６は変調部、３４は出射口である。図９において、入力光に対して、増幅制御端子（図示せず）からの制御入力信号により増幅部３５で飽和増幅を行い、変調部３６で変調入力端子（図示せず）からの変調入力信号により変調を行う。増幅変調された出力光は出射口３４から出力される。このように、増幅部と変調部を分離することにより、それぞれ独立に増幅作用と変調作用を行うことができる。
増幅器としての増幅度は増幅部に設けられた電極への制御入力信号電流の大小によって決定される。制御入力信号電流を大きくすると、増幅度も大きくなる。また、入力光に対して出力光の強度が飽和する飽和点も同時に大きくなる。増幅部を複数に分割し、前段部では増幅度を大きく、後段部では増幅度を小さくすることによって、効率的に飽和増幅することもできる。変調部では、変調入力信号電流によって、出力光を増幅又は減衰して強度変調する。変調入力信号電流によって光位相を変調すると位相変調、又は光周波数を変調すると周波数変調することになる。ここで、飽和増幅され、変調された出力光の波長は、出力強度飽和型増幅変調器への入力光の波長と同じである。
従って、出力強度飽和型増幅変調器３１又は３２を実施の形態で説明する従装置の光送受信装置に適用すると、上り光信号の波長を下り光信号の波長に追随させることができ、従装置での上り光信号の波長を高精度に制御したり、維持したりすることを不要とすることができた。
（実施の形態７）
反射膜付き出力強度飽和型増幅変調器を備える光送受信装置について説明する。通常の半導体光増幅器は、入力光に対して出力光が線形増幅される領域を使用して光増幅する。さらに、入射端面の入射口から入射した光信号を増幅して、入射端面と対向する出射端面の出射口から出射する。一方、反射膜付き出力強度飽和型増幅変調器は、半導体光増幅器において入力光に対して出力光の強度が飽和増幅する領域を積極的に利用し、かつ変調も行うようにしたものである。さらに、入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、入射端面の入射口から入射した光信号を飽和増幅、減衰させて、コーティグした反射膜で反射させた後、前記下り光信号の入射端面から送出する反射型構成である。
反射膜付き出力強度飽和型増幅変調器の概略断面を図１０に示す。図１０において、３３は増幅変調部、３７は反射膜付き出力強度飽和型増幅変調器、３９は入出射口、４０は反射膜である。
図１０において、入出射口３９からの入射光に対して、増幅変調部３３で入力信号により飽和増幅と減衰を行う。飽和増幅と減衰により、増幅変調された光信号は反射膜４０で反射されて、入出射口３９から出射する。出射した光信号は入射光を飽和増幅、減衰させるため、その波長は入射光と同じである。増幅器としての増幅度は増幅変調部に設けられた電極への入力信号電流の大小によって決定される。入力信号電流を大きくすると、増幅度も大きくなる。また、入力光に対して出力光の強度が飽和する飽和点も同時に大きくなる。入力信号電流を小さくすると入力光の増幅度が小さく、あるいは減衰することになる。入力信号電流によって光位相を変調すると位相変調、又は光周波数を変調すると周波数変調することになる。
他の反射膜付き出力強度飽和型増幅変調器の概略断面を図１１に示す。前述の出力強度飽和型増幅変調器は、１の電極で飽和増幅と変調を行った。本出力強度飽和型増幅変調器は飽和増幅部と変調部を分離したものである。従って、制御端子も増幅制御端子と変調入力端子に分離する。図１１において、３５は増幅部、３６は変調部、３８は反射膜付き出力強度飽和型増幅変調器、３９は入出射口、４０は反射膜である。
図１１において、入出射口３９からの入射光に対して、増幅制御端子（図示せず）からの制御入力信号により増幅部３５で飽和増幅を行い、変調部３６で変調入力端子（図示せず）からの変調入力信号により変調を行う。飽和増幅と減衰により、増幅変調された光信号は反射膜４０で反射されて、入出射口３９から出射する。出射した光信号は入射光を飽和増幅、減衰させるため、その波長は入射光と同じである。
増幅器としての増幅度は増幅部に設けられた電極への制御入力信号電流の大小によって決定される。制御入力信号電流を大きくすると、増幅度も大きくなる。また、入力光に対して出力光の強度が飽和する飽和点も同時に大きくなる。増幅部を複数に分割し、前段部では増幅度を大きく、後段部では増幅度を小さくすることによって、効率的に飽和増幅することもできる。変調部では、変調入力信号電流によって、出力光を増幅又は減衰して強度変調する。変調入力信号電流によって光位相を変調すると位相変調、又は光周波数を変調すると周波数変調することになる。
従って、反射膜付き出力強度飽和型増幅変調器３７又は３８を、従装置の光送受信装置、特に、実施の形態で説明する下り光信号の伝送と上り光信号の伝送に同じ光ファイバを使用する双方向光伝送方式に利用する従装置の光送受信装置に適用すると、上り光信号の波長を下り光信号の波長に追随させることができ、従装置での上り光信号の波長を高精度に制御したり、維持したりすることを不要とすることができた。
（実施の形態８）
本実施の形態は、反射膜付き出力強度飽和型増幅変調器を備える光送受信装置及び前記光送受信装置を利用した双方向光伝送方式である。反射膜付き出力強度飽和型増幅変調器を備える光送受信装置の構成を図１２に示す。図１２において、１５は光ファイバ、１７は従装置の光合分岐回路、１８は従装置の光受信回路、１９従装置の光送信回路、２２は光受信部、２３は駆動部、３７は反射膜付き出力強度飽和型増幅変調器である。
図１２において、光ファイバ１５を伝搬してきた下り光信号は、光合分岐回路１７によって、一部は光受信回路１８の光受信部で受信される。光合分岐回路１７で分岐された他の下り光信号は、反射膜付き出力強度飽和型増幅変調器３７に入射し、飽和増幅、変調された後、光合分岐回路１７に戻る。戻った光信号は、上りの光信号として光ファイバ１５を伝搬する。戻った光信号の波長は下り光信号の波長と同じである。ここで、反射膜付き出力強度飽和型増幅変調器３７を反射膜付き出力強度飽和型増幅変調器３８に置き換えても同様の効果が得られる。
反射膜付き出力強度飽和型増幅変調器は、入射口と出射口が共通であるために、実施の形態で説明する下り光信号の伝送と上り光信号の伝送に同じ光ファイバを使用する双方向光伝送方式に有効である。反射膜付き出力強度飽和型増幅変調器をこれらの伝送方式に適用すると、図１２と図４（ｂ）とを比較すれば明らかなように、本実施の形態を示す図１２では図４（ｂ）の光分岐回路２１が不要となる。このため、分岐に伴う光損失も減少する。
従って、本反射膜付き出力強度飽和型増幅変調器を、従装置の光送受信装置、特に、実施の形態で説明する下り光信号の伝送と上り光信号の伝送に同じ光ファイバを使用する双方向光伝送方式に利用する従装置の光送受信装置に適用すると、上り光信号の波長を下り光信号の波長に追随させることができ、従装置での上り光信号の波長を高精度に制御したり、維持したりすることを不要とすることができた。さらに、１芯光ファイバ方向多重双方向伝送や１芯光ファイバ双方向―波長多重マルチポイント伝送方式においては、光分岐回路の削減と光損失の減少を可能とすることができた。
（実施の形態９）
飽和増幅部及び変調部を有する出力強度飽和型増幅変調器を備える光送受信装置について説明する。飽和増幅部としては、入力光に対して出力光の強度が飽和増幅する領域を用いる半導体光増幅を利用する。変調部としては、小型低電圧で駆動できる半導体吸収型変調を利用する。吸収型変調は高速の変調が可能である。
出力強度飽和型増幅変調器の概略構造を図１３に示す。図１３において、６１は飽和増幅部及び変調部を有する出力強度飽和型増幅変調器、６２は飽和増幅部、６３は変調部、６４は半導体光増幅を実現する半導体活性層、６５は変調を実現する吸収変調層である。
図１３において、入力光に対して飽和増幅部６２で入力信号の飽和増幅を行い、バイアス成分が増幅されるとともに信号成分が圧縮され、さらに、変調部６３において変調される。変調部６３は吸収型変調を実現し、活性層のキャリアライフタイムに制限されないため、高速変調が可能である。本変調部では、吸収端が使用する波長に比べ短波長側に設定されているため、変調効率は入力光の波長に依存しない。
従って、出力強度飽和型増幅変調器６１を実施の形態で説明する従装置の光送受信装置に適用すると、上り光信号の波長を下り光信号の波長に追随させることができ、従装置での上り光信号の波長を高精度に制御したり、維持したりすることを不要とすることができた。
（実施の形態１０）
本実施の形態は、主装置と複数の従装置で２芯光ファイバ双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式である。本発明の実施の形態の構成を図１４に示す。図１４において、２５は主装置の光送信回路、２６は主装置の光受信回路、１５−１、１５−２は光ファイバ、１６−１、１６−２は光ファイバの途中に設けられた波長多重回路、１８−１〜１８−Ｎは従装置の光受信回路、１９−１〜１９−Ｎは従装置の光送信回路である。ここでは、２以上の複数を表すときに記号Ｎを用いた。例えば、光送信回路１１−１〜１１−Ｎは２以上の複数の光送信回路を表す。図１４において、下方向の矢印は下り、上方向の矢印は上りの伝送方向を表す。
主装置と複数の従装置で双方向伝送する方式の構成について説明する。図１４において、主装置の光送信回路２５は下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を従装置に向けて送信する。その際、主装置の光送信回路２５において、その中に有する波長可変光源の波長は、外部の制御信号によってＮ個の波長（λ１〜λＮ）のいずれかが割り当てられる。割り当てられる波長は、従装置の光受信回路１８−Ｎに送信する光信号はλＮの波長である。つまり、主装置の光送信回路２５は、従装置ごとに異なる時間領域と波長で光信号を送信する。
光ファイバ１５−１の途中に設けられた波長多重回路１６−１は、それぞれの下り光信号を波長に応じてそれぞれの従装置に向けて波長分離する。それぞれの従装置の光受信回路１８−１〜１８−Ｎは光ファイバ１５−１を通して受信した下り光信号から信号成分を検出する。それぞれの従装置の光送信回路１９−１〜１９−Ｎは受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバ１５−２に向けて送信する。従装置の光送信回路の出力強度飽和型増幅変調器で下り光信号を飽和増幅するため、送信する波長は下り光信号と同じである。光ファイバ１５−２の途中に設けられた波長多重回路１６−２は複数の光送信回路１９−１〜１９−Ｎから送信された、異なる波長（λ１〜λＮ）の上り光信号を主装置に向けて波長多重する。主装置の光受信回路２６は受信した上り光信号から上り信号を検出する。
次に、本構成での動作を説明する。下り信号の送信には、従装置の受信回路に送信する信号ごとに時間領域を分離する。さらに、従装置の受信回路に送信する信号ごとに波長可変レーザの波長を変える。例えば、従装置の受信回路１８−１に送信するときは、波長λ１でかつ時間領域がｔ１で下り光信号を送信する。下り信号で光を変調する動作は図２と同様である。時間領域はタイムスロットごとに受信する従装置の受信回路を変えてもよいし、一定の長さの情報をまとめたブロックごとでもよい。所定の従装置の受信回路に送信する光信号の時間領域と他の従装置の受信回路に送信する光信号の時間領域の間隔は複数の従装置との距離に応じて予め調整してもよいし、一定間隔を空けておくことでもよい。波長・時分割多重された光信号は、波長多重回路１６−１で従装置ごとに分離され、従装置の光受信回路１８−１〜１８−Ｎで受信される。光受信回路１８−１〜１８−Ｎでの下り信号の受信動作は図２（ｄ）と同様である。光受信回路１８−１〜１８−Ｎでは波長ごと、換言すると時間領域ごとに分離された光信号を受信する。
上り信号の送信動作は図３に示す飽和増幅及び変調動作と同様であるが、送信光信号は、各従装置に下り光信号が到達しているときに、上り光信号を送信する。各従装置からの上り光信号は波長多重回路１６−２で多重され、主装置の光受信回路２６で受信される。光受信回路２６で受信する際に、各従装置からの上り光信号が重ならないように、主装置から従装置へ向けて送信する際に時間領域の間隔が設定されている。下り光信号と上り光信号は別の光ファイバを用いて伝送される。このように動作して、２芯光ファイバ双方向・波長時分割多重マルチポイント伝送が行われる。
なお、主装置において、光受信回路２５に代えて、図５のように、主装置の波長多重回路１３−２と複数の主装置の光受信回路１２−１〜１２−Ｎとしてもよい。このような構成にすると、主装置から各従装置までの距離差に係らず、各従装置からの上り光信号が重ならないように、所定の従装置の受信回路に送信する光信号の時間領域と他の従装置の受信回路に送信する光信号の時間領域の間隔を設定する必要がなくなる。
ここで、各時間領域に割り当てられる波長は、λ１〜λＮのすべてを割り当てる必要はなく、各従装置へ送信する情報量に応じて変えることもできる。さらに、時間領域の長さも各従装置に対して一定ではなく、各従装置へ送信する情報量に応じて変えることもできる。
従って、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバに送信する構成とすることにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
また、従装置の光送信回路は出力強度飽和型増幅変調器によって、下り光信号と同じ波長の上り光信号を送信するため、波長多重回路に対して、上り光信号の波長を高精度に制御したり、維持したりする必要はなくなった。
さらに、本従装置の光送信回路において、半導体光増幅器の出力強度飽和増幅機能を広範囲の波長にわたって動作させると、波長ごとに従装置の種類が異なるのではなく、同一種の従装置を任意の従装置に適用することができる。即ち、従装置間で、相互運用性（インタオペラビリティ）を確保することが可能となった。
（実施の形態１１）
本実施の形態は、主装置と複数の従装置で１芯光ファイバ双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式である。本発明の実施の形態の構成を図１５に示す。図１５において、２５は主装置の光送信回路、２６は主装置の光受信回路、１５−１、１５−２は光ファイバ、１６−１、１６−２は光ファイバの途中に設けられた波長多重回路、１８−１〜１８−Ｎは従装置の光受信回路、１９−１〜１９−Ｎは従装置の光送信回路である。ここでは、２以上の複数を表すときに記号Ｎを用いた。例えば、光送信回路１１−１〜１１−Ｎは２以上の複数の光送信回路を表す。図１５において、下方向の矢印は下り、上方向の矢印は上りの伝送方向を表す。
主装置と複数の従装置で双方向伝送する方式の構成について説明する。図１５において、主装置の光送信回路２５は下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を従装置に向けて送信する。その際、主装置の光送信回路２５において、その中に有する波長可変光源の波長は、外部の制御信号によってＮ個の波長（λ１〜λＮ）のいずれかが割り当てられる。割り当てられる波長は、従装置の光受信回路１８−Ｎに送信する光信号はλＮの波長である。つまり、主装置の光送信回路２５は、従装置ごとに異なる時間領域と波長で光信号を送信する。
光ファイバ１５の途中に設けられた波長多重回路１６は、それぞれの下り光信号を波長に応じてそれぞれの従装置に向けて波長分離する。それぞれの従装置の光受信回路１８−１〜１８−Ｎは光ファイバ１５−１を通して受信した下り光信号から信号成分を検出する。それぞれの従装置の光送信回路１９−１〜１９−Ｎは受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバ１５に向けて送信する。従装置の光送信回路の出力強度飽和型増幅変調器で下り光信号を飽和増幅するため、送信する波長は下り光信号と同じである。光ファイバ１５の途中に設けられた波長多重回路１６は複数の光送信回路１９−１〜１９−Ｎから送信された、異なる波長（λ１〜λＮ）の上り光信号を主装置に向けて波長多重する。主装置の光受信回路２６は受信した上り光信号から上り信号を検出する。
次に、本構成での動作を説明する。下り信号の送信には、従装置の受信回路に送信する信号ごとに時間領域を分離する。さらに、従装置の受信回路に送信する信号ごとに波長可変レーザの波長を変える。例えば、従装置の受信回路１８−１に送信するときは、波長λ１でかつ時間領域がｔ１で下り光信号を送信する。下り信号で光を変調する動作は図２と同様である。時間領域はタイムスロットごとに受信する従装置の受信回路を変えてもよいし、一定の長さの情報をまとめたブロックごとでもよい。所定の従装置の受信回路に送信する光信号の時間領域と他の従装置の受信回路に送信する光信号の時間領域の間隔は複数の従装置との距離に応じて予め調整してもよいし、一定間隔を空けておくことでもよい。波長・時分割多重された光信号は、波長多重回路１６で従装置ごとに分離され、従装置の光受信回路１８−１〜１８−Ｎで受信される。光受信回路１８−１〜１８−Ｎでの下り信号の受信動作は図２（ｄ）と同様である。光受信回路１８−１〜１８−Ｎでは波長ごと、換言すると時間領域ごとに分離された光信号を受信する。
上り信号の送信動作は図３に示す飽和増幅及び変調動作と同様であるが、送信光信号は、各従装置に下り光信号が到達しているときに、上り光信号を送信する。各従装置からの上り光信号は波長多重回路１６で多重され、主装置の光受信回路２６で受信される。光受信回路２６で受信する際に、各従装置からの上り光信号が重ならないように、主装置から従装置へ向けて送信する際に時間領域の間隔が設定されている。下り光信号と上り光信号は同じ光ファイバを用いて伝送される。このように動作して、１芯光ファイバ双方向・波長時分割多重マルチポイント伝送が行われる。
なお、主装置において、光受信回路２５に代えて、図６のように、主装置の波長多重回路１３−２と複数の主装置の光受信回路１２−１〜１２−Ｎとしてもよい。このような構成にすると、主装置から各従装置までの距離差に係らず、各従装置からの上り光信号が重ならないように、所定の従装置の受信回路に送信する光信号の時間領域と他の従装置の受信回路に送信する光信号の時間領域の間隔を設定する必要がなくなる。
ここで、各時間領域に割り当てられる波長は、λ１〜λＮのすべてを割り当てる必要はなく、各従装置へ送信する情報量に応じて変えることもできる。さらに、時間領域の長さも各従装置に対して一定ではなく、各従装置へ送信する情報量に応じて変えることもできる。
従って、主装置の光送信回路が下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を光ファイバに送信し、従装置の光送信回路が受信した下り光信号の一部を飽和増幅・減衰回路によって上り信号で変調した上り光信号を光ファイバに送信する構成とすることにより、従装置側では、発光素子を使用することなく、双方向伝送をすることができた。
また、従装置の光送信回路は出力強度飽和型増幅変調器によって、下り光信号と同じ波長の上り光信号を送信するため、波長多重回路や光合分岐回路に対して、上り光信号の波長を高精度に制御したり、維持したりする必要はなくなった。
さらに、本従装置の光送信回路において、半導体光増幅器の出力強度飽和増幅機能を広範囲の波長にわたって動作させると、波長ごとに従装置の種類が異なるのではなく、同一種の従装置を任意の従装置に適用することができる。即ち、従装置間で、相互運用性（インタオペラビリティ）を確保することが可能となった。
１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式においては、下り信号と上り信号が同一波長で同一光ファイバ上を伝送される。そのため、主装置で上り信号を受信する場合、光ファイバの途中で反射した下り信号と相互干渉する場合がある。本実施の形態では、発光素子の駆動電流を制御して、下り信号に信号成分が重畳しているため、下り信号光のスペクトル幅を広くすることもできる。信号光のスペクトル幅が広くなると、上り信号と線路途中で反射した下り信号との相互干渉が抑制され、上り信号に加算する雑音を抑圧することが可能となる。
【図面の簡単な説明】
図１は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図２は、本願発明の双方向光伝送方式の動作図である。
図３は、本願発明の双方向光伝送方式の動作図である。
図４は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図５は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図６は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図７は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図８は、本願発明の実施形態を示す出力強度飽和型増幅変調器の概略構造図である。
図９は、本願発明の実施形態を示す出力強度飽和型増幅変調器の概略構造図である。
図１０は、本願発明の実施形態を示す反射膜付き出力強度飽和型増幅変調器の概略断面図である。
図１１は、本願発明の実施形態を示す反射膜付き出力強度飽和型増幅変調器の概略断面図である。
図１２は、反射膜付き出力強度飽和型増幅変調器を備える光送受信装置の構成図である。
図１３は、本願発明の実施形態を示す出力強度飽和型増幅変調器の概略構造図である。
図１４は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図１５は、本願発明の実施形態を示す双方向光伝送方式の構成図である。
図１６は、従来の双方向光伝送方式の構成図である。
図１７は、従来の双方向光伝送方式の動作図である。
図１８は、従来の双方向光伝送方式の構成図である。
図中の符号の説明は次の通りである。１１、１１−１、１１−２、１１−Ｎは主装置の光送信回路、１２、１２−１、１２−２、１２−Ｎは主装置の光受信回路、１３、１３−１、１３−２は主装置の波長多重回路、１４、１４−１、１４−２、１４−Ｎは主装置の光合分岐回路、１５、１５−１、１５−２は光ファイバ、１６、１６−１、１６−２は波長多重回路、１７、１７−１、１７−２、１７−Ｎは従装置の光合分岐回路、１８、１８−１、１８−２、１８−Ｎは従装置の光受信回路、１９、１９−１、１９−２、１９−Ｎは従装置の光送信回路、２１は光分岐回路、２２は光受信部、２３は駆動部、２４は出力強度飽和型増幅変調器、２５は主装置の光送信回路、２６は主装置の光受信回路、３１は出力強度飽和型増幅変調器、３２は出力強度飽和型増幅変調器、３３は増幅変調部、３４は出射口、３５は増幅部、３６は変調部、３７は反射膜付き出力強度飽和型増幅変調器、３８は反射膜付き出力強度飽和型増幅変調器、３９は入出射口、４０は反射膜、４１、４１−１、４１−２、４１−Ｎは主装置の光送信回路、４２、４２−１、４２−２、４２−Ｎは主装置の光受信回路、４３は光受信部、４４は光送信部、４５−１、４５−２は主装置の波長多重回路、４８、４８−１、４８−２、４８−Ｎは従装置の光受信回路、４９、４９−１、４９−２、４９−Ｎは従装置の光送信回路、６１は出力強度飽和型増幅変調器、６２は飽和増幅部、６３は変調部、６４は半導体活性層、６５は吸収変調層である。Technical field
The present invention relates to a bidirectional optical transmission system for bidirectional transmission between a main apparatus and a slave apparatus using an optical fiber, and an optical transmission / reception apparatus.
Background art
A configuration of a conventional bidirectional optical transmission system is shown in FIG. In FIG. 16, 15-1 and 15-2 are optical fibers, 41 is an optical transmission circuit of the main device, 42 is an optical reception circuit of the main device, 43 is an optical reception unit, 44 is an optical transmission unit, and 48 is an auxiliary device. An optical receiver circuit 49 is a slave optical transmitter circuit.
A configuration of a system for bidirectional transmission between the master device and the slave device will be described with reference to FIG. FIG. 16 shows a bidirectional optical transmission system in which a main apparatus and a slave apparatus are bidirectionally transmitted with a two-core optical fiber. That is, as shown in FIG. 16A, between the optical transmission circuit 41 of the master device and the optical receiver circuit 48 of the slave device, and between the optical transmitter circuit 49 of the slave device and the optical receiver circuit 42 of the master device. Are connected by two-core optical fibers 15-1 and 15-2 for bidirectional transmission. In FIG. 16A, the optical transmission circuit 41 of the main device transmits a downstream optical signal through the optical fiber 15-1, and the optical reception circuit 48 of the slave device receives the downstream optical signal. The optical transmission circuit 49 of the slave device transmits the upstream optical signal through the optical fiber 15-2, and the optical reception circuit 42 of the main device receives the upstream optical signal. FIG. 16B shows the head end configuration of the optical receiver circuit 48 and the optical transmitter circuit 49 of the slave device. In FIG. 16B, in the optical receiver circuit 48 of the slave device, the downstream optical signal received via the optical fiber 15-1 is detected by the optical receiver 43, and the detected downstream signal is stored in the optical receiver circuit 48. Is signal processed. On the other hand, the upstream signal is modulated into the upstream optical signal by the optical transmitter 44. The modulated upstream optical signal is transmitted through the optical fiber 15-2.
FIG. 17 shows transmission and reception operations of the upstream optical signal or downstream optical signal. In FIG. 17, the light emitting element is driven by the drive current of the downstream signal in the optical transmission circuit of the main device (FIG. 17A). The light output of the light emitting element has a substantially linear relationship with the drive current (FIG. 17B). As a result, the optical transmission circuit of the main apparatus transmits a downstream optical signal output close to the waveform of the downstream signal (FIG. 17C). In the optical receiver circuit of the slave device, a threshold is set for the signal component of the optical receiver circuit input, and the downstream signal is detected (FIG. 17 (d)). The operations of the optical transmission circuit of the slave device and the optical reception circuit of the main device are the same. That is, the optical transmission circuit of the main device and the optical transmission circuit of the slave device must each have a light emitting element.
The configuration of another conventional bidirectional transmission system is shown in FIG. This configuration is a bidirectional optical transmission system in which a master device and a plurality of slave devices perform two-core optical fiber bidirectional / wavelength multiplexing multipoint transmission. In FIG. 18, 41-1 to 41-N are optical transmission circuits of the main apparatus, 42-1 to 42-N are optical reception circuits of the main apparatus, 45-1 and 45-2 are wavelength multiplexing circuits of the main apparatus, 15 -1, 15-2 are optical fibers, 16-1, 16-2 are wavelength multiplexing circuits provided in the middle of the optical fiber, 48-1 to 48-N are slave optical receiver circuits, and 49-1 to 49-49. -N is the optical transmission circuit of the slave device. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 41-1 to 41-N represent two or more optical transmission circuits.
A configuration of a system that performs bidirectional transmission between the master device and a plurality of slave devices will be described. In FIG. 18, each of the plurality of optical transmission circuits 41-1 to 41-N of the main apparatus has a wavelength (λ 1 , Λ 2 ..Λ N ) To the wavelength multiplexing circuit 45-1 of the main device. The wavelength multiplexing circuit 45-1 wavelength-multiplexes downstream optical signals of different wavelengths transmitted from a plurality of optical transmission circuits onto the optical fiber 15-1. The wavelength multiplexing circuit 16-1 provided in the middle of the optical fiber 15-1 separates the wavelength of each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 48-1 to 48-N of the respective slave devices detect signal components from the downstream optical signal received through the optical fiber 15-1. On the other hand, the optical transmission circuits 49-1 to 49-N of the respective slave devices transmit the upstream optical signal modulated by the upstream signal to the optical fiber 15-2. The wavelength multiplexing circuit 16-2 provided in the middle of the optical fiber 15-2 is transmitted from the plurality of optical transmission circuits 49-1 to 49-N, and is assigned with each wavelength (λ 1 , Λ 2 ..Λ N ) Is multiplexed toward the main unit. The wavelength division multiplexing circuit 45-2 of the master unit transmits the wavelength (λ) respectively transmitted from the plurality of slave unit optical transmission circuits 49-1 to 49-N. 1 , Λ 2 ..Λ N ) Is separated for each wavelength toward the optical receiving circuits 42-1 to 42-N of the main apparatus. The plurality of optical receiving circuits 42-1 to 42-N of the main device detect upstream signals from the received upstream optical signals.
Here, each of the slave optical transmission circuits 49-1 to 49-N must transmit an upstream optical signal having a predetermined wavelength. The optical transmission circuits 49-1 to 49-N of the respective slave devices need to have light emitting elements, respectively, and furthermore, the wavelengths of these light emitting elements need to be controlled and maintained with high accuracy. Since the slave devices are generally distributed at different locations, the environmental temperature and the like are different. When the wavelength of the light emitting element shifts from a predetermined value due to a change in environmental temperature, light loss increases in the wavelength multiplexing circuit 16-2 in the middle of the optical fiber 15-2 and the wavelength multiplexing circuit 45-2 of the main device. . Furthermore, when the transition is large, there is a possibility that transmission cannot be performed.
In order to solve such problems, the present invention eliminates the need for a light emitting element in the optical transmission circuit of the slave device, and controls or maintains the wavelength of the light emitting element with high accuracy in the optical transmission circuit of the slave device. The purpose is to make it unnecessary.
Conventionally, as an optical component for processing an optical signal, a semiconductor optical amplifier circuit (for example, T. Mukai and T. Saitoh, “5.2 dB noise figure in a 1.5 μm InGaAsP traveling wave amplifier amplifier”, ElectroL. , Vol. 23, No. 5, pp. 216-218 (1987)). This is a semiconductor optical amplifier circuit in which the waveforms of an input optical signal and an output optical signal have a linear relationship.
Disclosure of the invention
In order to achieve the above-described object, the first invention of the present application is a bidirectional optical transmission system in which a two-core optical fiber is bidirectionally transmitted between a main device and a slave device using a first optical fiber and a second optical fiber. The main device receives an optical transmission circuit that transmits a downstream optical signal, in which a bias component is superimposed on a signal component modulated by a downstream signal, toward the first optical fiber, and the second optical fiber. An optical receiver circuit that detects an upstream signal from the upstream optical signal, and the slave device detects the signal component from the downstream optical signal received through the first optical fiber, and the received signal A bidirectional optical transmission comprising: an optical transmission circuit configured to transmit the upstream optical signal obtained by modulating a part of the downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit toward the second optical fiber. Is the method
A second invention of the present application is a bidirectional optical transmission system that performs directional multiplexing bidirectional transmission between a master device and a slave device using a single-core optical fiber, wherein the master device uses a signal component modulated by a downstream signal. An optical transmission circuit that transmits a downstream optical signal superimposed with a bias component toward the optical fiber, and an optical reception circuit that detects an upstream signal from the upstream optical signal received through the optical fiber, and the slave device includes An optical receiving circuit for detecting the signal component from the downstream optical signal received through an optical fiber; and the upstream optical signal obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit. A bidirectional optical transmission system comprising an optical transmission circuit that transmits toward a fiber.
The third invention of the present application is a bidirectional optical transmission system in which direction-multiplexed bidirectional transmission is performed with a single-core optical fiber between the main device and the slave device of the second invention of the present application. A semiconductor optical amplifier having a reflection type structure in which a film having a higher reflectance than that of a cleaved state is coated on an end face facing the incident end face of the downstream optical signal and transmitted from the incident end face of the downstream optical signal. Is a bidirectional optical transmission system characterized by
The fourth invention of the present application is a bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength multiplexing multipoint transmission is performed between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber. The main apparatus includes a plurality of optical transmission circuits that transmit the respective downstream optical signals in which a bias component is superimposed on a signal component modulated by the downstream signal toward the first optical fiber, and the second optical fiber. A plurality of optical receiving circuits for detecting upstream signals from the respective upstream optical signals received through the plurality of slave devices, wherein each of the plurality of slave devices extracts the signal component from the downstream optical signal received through the first optical fiber. An optical receiving circuit to detect, and each of the received downstream optical signals is modulated by the upstream amplification signal by a saturation amplification / attenuation circuit, and the upstream optical signal is transmitted to the second optical fiber. A bidirectional optical transmission system characterized by comprising a transmission circuit.
The fifth invention of the present application is a bidirectional optical transmission system in which a master device and a plurality of slave devices are unidirectionally and bidirectionally wavelength-multiplexed multipoint transmission using a single optical fiber, wherein the master device modulates with a downstream signal. A plurality of optical transmission circuits for transmitting the respective downstream optical signals in which a bias component is superimposed on the signal component to the optical fiber, and a plurality of lights for detecting the upstream signal from the respective upstream optical signals received through the optical fiber. Each of the plurality of slave devices saturates a part of the received downstream optical signal, and an optical receiver circuit that detects the signal component from the downstream optical signal received through the optical fiber. An optical transmission circuit that transmits the upstream optical signal modulated with the upstream signal by an amplification / attenuation circuit toward the optical fiber; That.
The sixth invention of the present application is the bidirectional optical transmission system in which the master device and the plurality of slave devices according to the fifth invention of the present application perform directional multiplexing bidirectional-wavelength multiplexing multipoint transmission using a single-core optical fiber. The attenuating circuit is a semiconductor optical amplifier, wherein a film having a higher reflectance than that of the cleaved state is coated on the end face facing the incident end face of the downstream optical signal, and the reflection type is transmitted from the incident end face of the downstream optical signal It is a bidirectional optical transmission system characterized by having a configuration.
The seventh invention of the present application is a bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength time division multiplex multipoint transmission is performed between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber. The master device separates each downstream optical signal obtained by superimposing a bias component on the signal component modulated by the downstream signal into a wavelength and a time domain for each slave device and transmits the separated signals to the first optical fiber. And at least one optical receiving circuit that detects an upstream signal from each upstream optical signal received through the second optical fiber, and each of the plurality of slave devices includes the first light. An optical receiving circuit for detecting the signal component from the downstream optical signal received through the fiber, and the upstream light obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit, respectively. A bidirectional optical transmission system characterized by comprising an optical transmission circuit for transmitting toward the second optical fiber No..
The eighth invention of the present application is a two-core optical fiber bidirectional / wavelength time-division multiplex multipoint between the main device and the plurality of slave devices of the seventh invention of the present application using the first optical fiber and the second optical fiber. In the bidirectional optical transmission system for transmission, the optical transmission circuit uses a wavelength tunable light source capable of changing the wavelength of the optical output to the wavelength of each slave device.
A ninth invention of the present application is a bidirectional optical transmission system in which a master device and a plurality of slave devices perform direction multiplexing bidirectional / wavelength time division multiplexing multipoint transmission using a single optical fiber, An optical transmission circuit that separates each downstream optical signal obtained by superimposing a bias component on the signal component modulated in step S1 into a wavelength and a time domain for each slave device and transmits the signals to the optical fiber, and each received through the optical fiber. At least one optical receiving circuit that detects an upstream signal from an upstream optical signal, and each of the plurality of slave devices includes an optical receiving circuit that detects the signal component from the downstream optical signal received through the optical fiber; An optical transmission circuit configured to transmit the upstream optical signal obtained by modulating a part of the received downstream optical signal with the upstream signal by a saturation amplification / attenuation circuit toward the optical fiber; A bidirectional optical transmission system, characterized in that it comprises.
The tenth invention of the present application is the above-mentioned saturation in the bidirectional optical transmission system in which the master device and the plurality of slave devices according to the ninth invention of the present application perform direction multiplexing bidirectional / wavelength time division multiplexing multipoint transmission with a single optical fiber. The amplifying / attenuating circuit is a semiconductor optical amplifier, and a film having a higher reflectance than that of the cleaved state is coated on the end face facing the incident end face of the downstream optical signal, and is transmitted from the incident end face of the downstream optical signal. A bidirectional optical transmission system characterized by a reflective configuration.
The eleventh invention of the present application is the bidirectional optical transmission system in which the master device and the plurality of slave devices according to the ninth invention of the present application perform directional multiplexing bidirectional / wavelength time division multiplexing multipoint transmission with a single-core optical fiber, The bidirectional optical transmission system is characterized in that a wavelength variable light source capable of changing the wavelength of the optical output to the wavelength of each slave device is used in the optical transmission circuit.
The twelfth invention of the present application is an optical transmission circuit that transmits a second optical signal, which is obtained by modulating a part of the received first optical signal with a second transmission signal by a saturation amplification / attenuation circuit, toward an optical fiber. An optical transmission circuit that transmits a first optical signal in which a bias component is superimposed on a signal component modulated by a first transmission signal, and a signal from the second optical signal received through an optical fiber. An optical transmission / reception apparatus including an optical reception circuit for detecting a component.
The thirteenth invention of the present application is an optical receiving circuit that receives an optical signal in which a bias component is superimposed on a signal component modulated by a signal through an optical fiber, and a part of the received optical signal is transmitted by a saturation amplification / attenuation circuit. An optical transmission / reception apparatus including an optical transmission circuit that modulates a signal to be transmitted and transmits the modulated signal toward an optical fiber.
A fourteenth invention of the present application is the optical transceiver according to the twelfth invention of the present application, wherein the bias component is 50% or more, preferably 100% or more of the signal component. .
The fifteenth aspect of the present invention is the optical transceiver according to the thirteenth aspect of the present invention, wherein the saturation amplification / attenuation circuit modulates an optical signal with an amplifier that controls the amplification degree by a control current and a signal to be transmitted. An optical transceiver characterized by being a semiconductor optical amplifier having a unit.
According to a sixteenth aspect of the present invention, in the optical transmission / reception apparatus according to the thirteenth aspect of the present invention, the saturation amplification / attenuation circuit includes: an amplification unit that is saturated by a control current; and a modulation unit that absorbs an optical signal by a transmitted signal. An optical transmitter / receiver characterized by being a semiconductor optical device.
These configurations can be combined as much as possible.
Here, the saturation amplification / attenuation circuit is a circuit in which linear amplification is performed in a range where the optical input is small, but when the optical input is increased, the amplification degree is saturated and the optical output is constant regardless of the optical input level. Further, the amplification degree can be controlled, and the amplification degree can be increased and saturated amplification can be performed, or conversely, the amplification degree can be suppressed and attenuated. It should be noted that the attenuation in the saturation amplification / attenuation circuit includes a simple amplification factor.
Two-core optical fiber bidirectional transmission refers to a technique of bidirectional transmission using a first optical fiber for transmission of downstream optical signals and a second optical fiber for transmission of upstream optical signals. Single-core optical fiber directional bidirectional transmission uses the same optical fiber for transmission of downstream optical signals and upstream optical signals, and uses an optical multiplexing / branching circuit to combine and branch downstream optical signals and upstream optical signals having the same wavelength This refers to a technology for bidirectional transmission.
Two-core optical fiber bidirectional / wavelength multiplexing multipoint transmission is a transmission method in which a master device and a plurality of slave devices are connected in a 1-to-N multipoint connection. The second optical fiber is used for signal transmission, and different wavelengths are assigned to the upstream optical signal and downstream optical signal for each slave device, and a wavelength is provided between the wavelength multiplexing circuit provided in the middle of the master device and the optical fiber. This is a technology that performs multiplex transmission and bidirectional transmission. Single-core optical fiber direction multiplexing bidirectional / wavelength multiplexing multipoint transmission is the same as transmission of downstream optical signals and transmission of upstream optical signals in a transmission system in which a master device and a plurality of slave devices are connected in a 1-to-N multipoint connection. Using an optical fiber, the upstream optical signal and downstream optical signal have the same wavelength, and different wavelengths are assigned to each slave device, and wavelength multiplexing transmission is performed between the master device and the wavelength multiplexing circuit provided in the middle of the optical fiber. This is a bidirectional transmission technology.
Two-core optical fiber bi-directional / wavelength time-division multiplex multipoint transmission is a transmission method in which a master device and a plurality of slave devices are connected in a one-to-N multipoint connection. Wavelength multiplexing provided in the middle of the main device and optical fiber, using a second optical fiber for transmission of the upstream optical signal, assigning different wavelengths and time regions to the upstream optical signal and downstream optical signal for each slave device. This is a technology that performs wavelength-division multiplex transmission between circuits for bidirectional transmission. Single-core optical fiber direction multiplexing bidirectional / wavelength time division multiplexing multipoint transmission is a transmission method in which a master device and a plurality of slave devices are connected in a one-to-N multipoint connection, and transmission of downstream optical signals and transmission of upstream optical signals. The same optical fiber is used for the upstream optical signal and downstream optical signal with the same wavelength, and different wavelengths and time regions are assigned to each slave device, and the wavelength multiplexing circuit provided between the master device and the optical fiber is used. Is a technology for transmitting in a wavelength-division multiplexed manner and bi-directional transmission.
Further, here, “down” means a signal flow from the master device to the slave device, and “up” means a signal flow from the slave device to the master device.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is limited to these forms and is not interpreted.
(Embodiment 1)
This embodiment is a bidirectional optical transmission system that performs bidirectional transmission of a two-core optical fiber. The configuration of the embodiment of the present invention is shown in FIG. In FIG. 1, 11 is an optical transmission circuit of the main device, 12 is an optical reception circuit of the main device, 15-1 and 15-2 are optical fibers, 18 is an optical reception circuit of the slave device, and 19 is an optical transmission circuit of the slave device. , 21 is an optical branch circuit, 22 is an optical receiver, 23 is a drive unit, and 24 is an output intensity saturation type amplifying modulator as a saturation amplification / attenuation circuit.
A configuration of a system for bidirectional transmission between the master device and the slave device will be described with reference to FIG. In FIG. 1A, the optical transmission circuit 11 of the main device transmits a downstream optical signal through the optical fiber 15-1, and the optical reception circuit 18 of the slave device receives the downstream optical signal. The optical transmission circuit 19 of the slave device transmits the upstream optical signal through the optical fiber 15-2, and the optical reception circuit 12 of the main device receives the upstream optical signal. FIG. 1B shows the head end configuration of the optical receiver circuit 18 and the optical transmitter circuit 19 of the slave device. In FIG. 1B, in the optical receiver circuit 18 of the slave device, the downstream optical signal received via the optical fiber 15-1 is branched into two by the optical branch circuit 21. The branched downstream optical signal is detected by the optical receiver 22, and the detected downstream signal is signal-processed in the optical receiver circuit 18. The output intensity saturation type amplifying modulator 24 saturates and amplifies a part of the branched downstream optical signal with the upstream signal from the drive unit 23, and modulates it to the upstream optical signal. The modulated upstream optical signal is transmitted through the optical fiber 15-2.
Next, the operation in this configuration will be described. The operation of transmitting and receiving the downstream optical signal is shown in FIG. 2, and the operation of transmitting and receiving the upstream optical signal is shown in FIG. In FIG. 2, in the optical transmission circuit of the main apparatus, a bias component is superimposed on the signal component modulated by the downstream signal to obtain a drive current for the light emitting element (FIG. 2 (a)). The light output of the light emitting element has a substantially linear relationship with the drive current (FIG. 2B). As a result, the optical transmission circuit of the main device transmits a downstream optical signal output close to the waveform of the drive current (FIG. 2C). In the optical receiver circuit of the slave device, a threshold value is set for the signal component of the optical receiver circuit input, and the signal component of the downstream signal is detected (FIG. 2D). Here, an example in which the downlink signal is intensity-modulated and transmitted / received is shown, but a modulation format such as phase modulation and frequency modulation may be used. Even in these modulation formats, the optical transmission circuit of the main device transmits a bias component superimposed on the signal component, and the downstream optical signal component is detected from the signal component of the optical reception circuit of the slave device.
In FIG. 3, a part of the downstream optical signal is branched and input to the output intensity saturated amplification modulator (FIG. 3 (a)). The output intensity saturation type amplifying modulator linearly amplifies the light input in a small range, but the gain is saturated when the light input becomes large, and the light output becomes constant regardless of the light input level (FIG. 3B). . Furthermore, the output intensity saturation type amplification modulator is an amplification modulator whose amplification degree can be controlled from the control terminal, and it is possible to increase the amplification degree to saturate amplification or conversely attenuate the amplification degree while suppressing the amplification degree. (FIG. 3B). When the branched downstream optical signal is input to the output intensity saturated amplification modulator, the bias component is superimposed on the signal component of the downstream optical signal, so that the bias component is amplified and the signal component is compressed by saturation amplification. (FIG. 3C). Furthermore, when an upstream signal is input from the drive unit of the optical transmission circuit of the device according to the control terminal of the output intensity saturation type amplification modulator, the amplification degree is controlled according to the upstream signal. A high-power optical signal that has been amplified and the signal component is compressed is output, and a low-power optical signal in which both the bias component and the signal component are compressed is output at the time of attenuation when the degree of amplification is suppressed (FIG. 3 ( c)). In the optical receiver circuit of the main apparatus, a threshold value is set for the signal component of the optical receiver circuit input, and the signal component of the upstream optical signal is detected (FIG. 3D).
Here, if the bias component is 50% or more of the signal component, the optical power of the bias component is greater than or equal to the average optical power of the signal component when the mark ratio of the intensity-modulated signal is 50% duty. It becomes easy to amplify the bias component with the output intensity saturation type amplifying modulator. When the bias component is 100% or more of the signal component, the optical power of the bias component becomes equal to or higher than the peak optical power of the signal component, and it is easier to amplify the bias component with an output intensity saturated amplification modulator. It becomes. The same applies to the following embodiments.
As described above, a downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal by the optical transmission circuit of the main apparatus is transmitted to the optical fiber, and one of the downstream optical signals received by the optical transmission circuit of the slave apparatus is transmitted. By transmitting an upstream optical signal that is modulated with an upstream signal by a saturation amplification / attenuation circuit, the slave device can perform bidirectional transmission without using a light emitting element.
(Embodiment 2)
The present embodiment is a bidirectional optical transmission system in which direction-multiplexed bidirectional transmission is performed using a single-core optical fiber. The configuration of the embodiment of the present invention is shown in FIG. In FIG. 4, 11 is the optical transmission circuit of the main device, 12 is the optical reception circuit of the main device, 14 is the optical multiplexing / branching circuit of the main device, 15 is the optical fiber, 17 is the optical multiplexing / branching circuit of the slave device, and 18 is the optical multiplexing / branching circuit. An optical receiving circuit, 19 is an optical transmission circuit of a slave device, 21 is an optical branching circuit, 22 is an optical receiving unit, 23 is a driving unit, and 24 is an output intensity saturated amplification modulator as a saturation amplification / attenuation circuit.
A configuration of a system for bidirectional transmission between the master device and the slave device will be described with reference to FIG. In FIG. 4A, the optical transmission circuit 11 of the main apparatus transmits a downstream optical signal through the optical coupling / branching circuit 14 and the optical fiber 15 of the main apparatus, and the optical reception circuit 18 of the slave apparatus passes through the optical coupling / branching circuit 17 of the slave apparatus. The downstream optical signal is received. The optical transmission circuit 19 of the slave device transmits the upstream optical signal through the optical coupling / branching circuit 17 of the slave device and the optical fiber 15, and the optical reception circuit 12 of the main device receives the upstream optical signal through the optical coupling / branching circuit of the main device. FIG. 4B shows the head end configuration of the optical receiver circuit 18 and the optical transmitter circuit 19 of the slave device. In FIG. 4B, in the optical receiving circuit 18 of the slave device, the downstream optical signal received via the optical coupling / branching circuit 17 of the slave device is branched into two by the optical branch circuit 21. The branched downstream optical signal is detected by the optical receiver 22, and the detected downstream signal is signal-processed in the optical receiver circuit 18. The output intensity saturation type amplifying modulator 24 saturates and amplifies a part of the branched downstream optical signal with the upstream signal from the drive unit 23 and modulates it to the upstream optical signal. The modulated upstream optical signal is transmitted through the optical coupling / branching circuit 17 and the optical fiber 15 of the slave device. The optical coupling / branching circuit 17 and the optical branching circuit 21 may be configured integrally.
Next, the operation in this configuration will be described. The operations for transmitting and receiving the downstream optical signal are the same as those in FIG. 2, and the operations for transmitting and receiving the upstream optical signal are the same as those in FIG. The difference is that the optical transmission / reception circuits 14 and 17 are provided in the main device and the slave device, respectively, so that bidirectional transmission is possible with a single-core optical fiber. By these optical coupling / branching circuits, the upstream optical signal and the downstream optical signal are separated. A directional optical coupling circuit, an optical circulator, or the like can be applied to the optical coupling / branching circuit. The optical transmission circuit and optical reception circuit of the main device and the optical transmission circuit and optical reception circuit of the slave device operate in the same manner as in the first embodiment.
In a bidirectional optical transmission system in which direction-multiplexed bidirectional transmission is performed using a single-core optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber at the same wavelength. For this reason, when an upstream signal is received by the main apparatus, there may be mutual interference with a downstream signal reflected in the middle of the optical fiber. In the present embodiment, since the drive current of the light emitting element is controlled and the signal component is superimposed on the downlink signal, the spectrum width of the downlink signal light can be widened. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.
Therefore, the optical transmission circuit of the main device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the slave optical transmission circuit is saturated and amplified. -By adopting a configuration in which an upstream optical signal modulated with an upstream signal by an attenuation circuit is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.
In addition, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as that of the downstream optical signal by the output intensity saturated amplification modulator, the upstream optical signal is not affected even if the optical multiplexing and branching circuit has wavelength dependency. It is no longer necessary to control or maintain the wavelength of the laser with high accuracy.
Further, in the optical transmission circuit of the slave device, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths, the type of the slave device is not different for each wavelength, and the slave device of the same type is arbitrarily set. It can be applied to a slave device. That is, interoperability between the slave devices can be ensured.
(Embodiment 3)
This embodiment is a bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength multiplexed multipoint transmission is performed between a master device and a plurality of slave devices. The configuration of the embodiment of the present invention is shown in FIG. In FIG. 5, 11-1 to 11-N are optical transmission circuits of the main apparatus, 12-1 to 12-N are optical reception circuits of the main apparatus, 13-1 and 13-2 are wavelength multiplexing circuits of the main apparatus, 15 -1, 15-2 are optical fibers, 16-1, 16-2 are wavelength multiplexing circuits provided in the middle of the optical fiber, 18-1 to 18-N are slave optical receiver circuits, and 19-1 to 19-19. -N is the optical transmission circuit of the slave device. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11-1 to 11-N represent two or more optical transmission circuits. In FIG. 5, the down arrow indicates the down transmission direction, and the up arrow indicates the up transmission direction.
A configuration of a system that performs bidirectional transmission between the master device and a plurality of slave devices will be described. In FIG. 5, a plurality of optical transmission circuits 11-1 to 11-N of the main apparatus transmit respective downstream optical signals in which a bias component is superimposed on a signal component modulated by the downstream signal to the wavelength multiplexing circuit 13-1 of the main apparatus. To do. The wavelengths of the optical signals of the optical transmission circuits 11-1 to 11-N are assigned in advance (λ 1 , Λ 2 ..Λ N ). The wavelength multiplexing circuit 13-1 transmits different wavelengths (λ) transmitted from the plurality of optical transmission circuits 11-1 to 11-N. 1 ~ Λ N ) Is multiplexed on the optical fiber 15-1. The wavelength multiplexing circuit 16-1 provided in the middle of the optical fiber 15-1 separates the wavelength of each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 18-1 to 18-N of the respective slave devices detect signal components from the downstream optical signal received through the optical fiber 15-1. Each of the slave optical transmission circuits 19-1 to 19-N transmits, to the optical fiber 15-2, an upstream optical signal obtained by modulating a part of the received downstream optical signal with an upstream signal by a saturation amplification / attenuation circuit. Since the downstream optical signal is saturated and amplified by the output intensity saturation type amplifying modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as that of the downstream optical signal. The wavelength multiplexing circuit 16-2 provided in the middle of the optical fiber 15-2 has different wavelengths (λ transmitted from a plurality of optical transmission circuits 19-1 to 19-N. 1 ~ Λ N ) Is multiplexed toward the main unit. The wavelength division multiplexing circuit 13-2 of the master device transmits different wavelengths (λ) transmitted from the optical transmission circuits 19-1 to 19-N of the slave devices. 1 ~ Λ N ) Is separated for each wavelength toward the optical receiving circuits 12-1 to 12-N of the main apparatus. The plurality of optical receiving circuits 12-1 to 12-N of the main device detect the upstream signal from the received upstream optical signal.
Next, the operation in this configuration will be described. The operations for transmitting and receiving the downstream optical signal are the same as those in FIG. 2, and the operations for transmitting and receiving the upstream optical signal are the same as those in FIG. The difference is that the wavelength division multiplexing circuits 13-1 and 13-2 are provided in the main device, and the wavelength division multiplexing circuits 16-1 and 16-2 are provided in the middle of the optical fiber, so that the wavelength division multiplexing multipoints are provided between the main device and the plurality of slave devices. Transmission is possible. The upstream and downstream optical signals are multiplexed and separated by the wavelength multiplexing circuits 16-1 and 16-2. The optical transmission circuit and optical reception circuit of the main device and the optical transmission circuit and optical reception circuit of the slave device operate in the same manner as in the first embodiment.
Therefore, the optical transmission circuit of the main device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the slave optical transmission circuit is saturated and amplified. -By adopting a configuration in which an upstream optical signal modulated with an upstream signal by an attenuation circuit is transmitted, the slave device side can perform bidirectional transmission without using a light emitting element.
Further, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as that of the downstream optical signal by the output intensity saturation type amplifying modulator, the upstream side transmission circuit of the wavelength division multiplexing circuit has the upstream characteristic. It is no longer necessary to match or maintain the wavelength of the optical signal with high accuracy.
Further, in the optical transmission circuit of the slave device, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths, the type of the slave device is not different for each wavelength, and the slave device of the same type is arbitrarily set. It can be applied to a slave device. That is, interoperability between the slave devices can be ensured.
(Embodiment 4)
This embodiment is a bidirectional optical transmission system in which a multiplex optical bidirectional / wavelength multiplexed multipoint transmission is performed by a single optical fiber between a master device and a plurality of slave devices. The configuration of the embodiment of the present invention is shown in FIG. In FIG. 6, 11-1 to 11-N are optical transmission circuits of the main apparatus, 12-1 to 12-N are optical reception circuits of the main apparatus, 13-1 and 13-2 are wavelength multiplexing circuits of the main apparatus, 14 Is an optical coupling / branching circuit of the main device, 15 is an optical fiber, 16 is a wavelength multiplexing circuit provided in the middle of the optical fiber, 17-1 to 17-N are optical multiplexing / branching circuits of the slave device, and 18-1 to 18-N are The optical receiver circuits 19-1 to 19-N are slave optical transmitter circuits. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11-1 to 11-N represent two or more optical transmission circuits. In FIG. 6, a downward arrow indicates a downward transmission direction, an upward arrow indicates an upward transmission direction, and an up and down direction arrow indicates a bidirectional transmission direction.
A configuration of a system that performs bidirectional transmission between the master device and a plurality of slave devices will be described. In FIG. 6, the plurality of optical transmission circuits 11-1 to 11-N of the main apparatus direct the respective downstream optical signals obtained by superimposing a bias component on the signal component modulated by the downstream signal to the wavelength multiplexing circuit 13-1 of the main apparatus. To send. The wavelengths of the downstream optical signals of the optical transmission circuits 11-1 to 11-N are assigned in advance (λ 1 , Λ 2 ..Λ N ). The wavelength division multiplexing circuit 13-1 of the main apparatus transmits different wavelengths (λ) transmitted from the plurality of optical transmission circuits 11-1 to 11-N. 1 ~ Λ N ) Of the downstream optical signal. The optical coupling / branching circuit 14 of the main apparatus joins these downstream optical signals to the optical fiber 15-1. A wavelength multiplexing circuit 16 provided in the middle of the optical fiber 15 separates each downstream optical signal toward each slave device according to the wavelength. The optical coupling / branching circuits 17-1 to 17-N of the respective slave devices branch the downstream optical signal to the corresponding optical receiving circuits 18-1 to 18-N. The optical receiving circuits 18-1 to 18-N detect signal components from the received downstream optical signal.
Each of the slave optical transmission circuits 19-1 to 19-N branches a part of the received downstream optical signal by an optical branch circuit (not shown) and modulates the upstream signal by the saturation amplification / attenuation circuit with the upstream signal. Send an optical signal. The optical branching circuit for branching a part of the downstream optical signal and the optical combining / branching circuit 17 may be configured integrally. Since the downstream optical signal is saturated and amplified by the output intensity saturation amplification modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as that of the downstream optical signal. The optical coupling / branching circuits 17-1 to 17 -N of the slave devices merge upstream optical signals into the optical fiber 15. The wavelength multiplexing circuit 16 provided in the middle of the optical fiber 15 has different wavelengths (λ) transmitted from a plurality of optical transmission circuits 19-1 to 19-N. 1 ~ Λ N ) Is multiplexed toward the main unit. The wavelength division multiplexing circuit 13-2 of the master device transmits different wavelengths (λ) transmitted from the optical transmission circuits 19-1 to 19-N of the slave devices. 1 ~ Λ N ) Is separated for each wavelength toward the optical receiving circuits 12-1 to 12-N of the main apparatus. The plurality of optical receiving circuits 12-1 to 12 -N of the main device each detect an upstream signal from the received upstream optical signal.
Next, the operation in this configuration will be described. The operations for transmitting and receiving the downstream optical signal are the same as those in FIG. 2, and the operations for transmitting and receiving the upstream optical signal are the same as those in FIG. The difference is that the wavelength division multiplexing circuits 13-1 and 13-2 and the optical multiplexing / branching circuit 14 are provided in the main device, the wavelength multiplexing circuit 16 is provided in the middle of the optical fiber, and the optical multiplexing / branching circuits 17-2 to 17- in the plurality of slave devices. By providing N, one-core optical fiber direction-multiplexed bidirectional / wavelength-multiplexed multipoint transmission is possible between the master device and the plurality of slave devices. A plurality of upstream optical signals and a plurality of downstream optical signals are multiplexed or separated by these wavelength multiplexing circuits and optical coupling / branching circuits. The optical transmission circuit and optical reception circuit of the main device and the optical transmission circuit and optical reception circuit of the slave device operate in the same manner as in the first embodiment.
In a bidirectional optical transmission system in which directional multiplexing bidirectional / wavelength multiplexing multipoint transmission is performed using a single-core optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber at the same wavelength. For this reason, when an upstream signal is received by the main apparatus, there may be mutual interference with a downstream signal reflected in the middle of the optical fiber. In the present embodiment, since the drive current of the light emitting element is controlled and the signal component is superimposed on the downlink signal, the spectrum width of the downlink signal light can be widened. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.
Therefore, the optical transmission circuit of the main device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the slave optical transmission circuit is saturated and amplified. -By adopting a configuration in which an upstream optical signal modulated with an upstream signal by an attenuation circuit is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.
Further, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as that of the downstream optical signal by the output intensity saturation type amplifying modulator, the upstream side transmission circuit of the wavelength division multiplexing circuit has the upstream characteristic. It is no longer necessary to match or maintain the wavelength of the optical signal with high accuracy.
Further, in the optical transmission circuit of the slave device, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths, the type of the slave device is not different for each wavelength, and the slave device of the same type is arbitrarily set. It can be applied to a slave device. That is, interoperability between the slave devices can be ensured.
(Embodiment 5)
The present embodiment is a bidirectional optical transmission system in which a master device and a plurality of slave devices perform single-core optical fiber direction multiplexing bidirectional / wavelength multiplexing multipoint transmission. The configuration of the embodiment of the present invention is shown in FIG. 7, 11-1 to 11-N are optical transmission circuits of the main apparatus, 12-1 to 12-N are optical reception circuits of the main apparatus, 13 is a wavelength multiplexing circuit of the main apparatus, and 14-1 to 14-N. Is an optical coupling / branching circuit of the main device, 15 is an optical fiber, 16 is a wavelength multiplexing circuit provided in the middle of the optical fiber, 17-1 to 17-N are optical multiplexing / branching circuits of the slave device, and 18-1 to 18-N are The optical receiver circuits 19-1 to 19-N are slave optical transmitter circuits. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11-1 to 11-N represent two or more optical transmission circuits. In FIG. 7, a downward arrow indicates a downward transmission, an upward arrow indicates an upward transmission, and an up and down arrow indicates an upstream / downward bidirectional transmission direction.
The configuration and operation of a method of bidirectional transmission between the master device and a plurality of slave devices will be described. In FIG. 7, the difference from the fourth embodiment is the arrangement of the optical coupling / branching circuit and the wavelength multiplexing circuit of the main apparatus. That is, the connection between the wavelength division multiplexing circuit and the optical multiplexing / branching circuit of the main device is reversed from that of the fourth embodiment. Since both the optical coupling / branching circuit and the wavelength multiplexing circuit are linear circuits, the same operation is performed even if the order of connection is changed. Either the fourth embodiment or the fifth embodiment is selected depending on the optical loss and the required number of optical multiplexing / branching circuits and wavelength multiplexing circuits.
In a bidirectional optical transmission system in which directional multiplexing bidirectional / wavelength multiplexing multipoint transmission is performed using a single-core optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber at the same wavelength. For this reason, when an upstream signal is received by the main apparatus, there may be mutual interference with a downstream signal reflected in the middle of the optical fiber. In the present embodiment, since the drive current of the light emitting element is controlled and the signal component is superimposed on the downlink signal, the spectrum width of the downlink signal light can be widened. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.
Therefore, the optical transmission circuit of the main device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the slave optical transmission circuit is saturated and amplified. -By adopting a configuration in which an upstream optical signal modulated with an upstream signal by an attenuation circuit is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.
Further, since the optical transmission circuit of the slave device transmits an upstream optical signal having the same wavelength as that of the downstream optical signal by the output intensity saturation type amplifying modulator, the upstream side transmission circuit of the wavelength division multiplexing circuit has the upstream characteristic. It is no longer necessary to match or maintain the wavelength of the optical signal with high accuracy.
Further, in the optical transmission circuit of the slave device, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths, the type of the slave device is not different for each wavelength, and the slave device of the same type is arbitrarily set. It can be applied to a slave device. That is, interoperability between the slave devices can be ensured.
(Embodiment 6)
An optical transmission / reception apparatus including an output intensity saturated amplification modulator will be described. A normal semiconductor optical amplifier performs optical amplification using a region where output light is linearly amplified with respect to input light. On the other hand, the output intensity saturation type amplifying modulator actively utilizes a region where the intensity of the output light is saturated and amplified with respect to the input light in the semiconductor optical amplifier, and also performs modulation. Since the output intensity saturated amplification modulator only amplifies the input light, the wavelength of the output light follows the input light.
A schematic structure of the output intensity saturated amplification modulator is shown in FIG. In FIG. 8, 31 is an output intensity saturation type amplification modulator, 33 is an amplification modulation unit, and 34 is an exit. In FIG. 8, saturation amplification and attenuation are performed with respect to input light by an input signal from a control terminal (not shown) in the amplification modulator 33. The output light that has been amplified and modulated by saturation amplification and attenuation is output from the exit 34. In this way, modulation by the input signal can be performed by saturation amplification and attenuation.
The amplification degree as an amplifier is determined by the magnitude of the input signal current to the electrode provided in the amplification modulation section. Increasing the input signal current increases the amplification. In addition, the saturation point at which the intensity of the output light is saturated with respect to the input light is also increased at the same time. When the input signal current is reduced, the amplification degree of the input light is reduced or attenuated. When the optical phase is modulated by the input signal current, phase modulation is performed, or when the optical frequency is modulated, frequency modulation is performed. Here, the wavelength of the output light subjected to saturation amplification and modulation is the same as the wavelength of the input light to the output intensity saturation type amplification modulator.
FIG. 9 shows a schematic structure of another output intensity saturated amplification modulator. The above-described output intensity saturated amplification modulator performs saturation amplification and modulation with one electrode. This output intensity saturation type amplifying modulator is obtained by separating a saturation amplifying unit and a modulating unit. Therefore, the control terminal is also separated into an amplification control terminal and a modulation input terminal.
In FIG. 9, 32 is an output intensity saturation type amplification modulator, 35 is an amplification unit, 36 is a modulation unit, and 34 is an emission port. In FIG. 9, saturation amplification is performed in the amplification unit 35 by a control input signal from an amplification control terminal (not shown) with respect to input light, and a modulation input signal from a modulation input terminal (not shown) in the modulation unit 36. Modulate with The amplified and modulated output light is output from the exit port 34. In this manner, by separating the amplification unit and the modulation unit, the amplification operation and the modulation operation can be performed independently.
The amplification degree as an amplifier is determined by the magnitude of the control input signal current to the electrode provided in the amplification section. When the control input signal current is increased, the degree of amplification is also increased. In addition, the saturation point at which the intensity of the output light is saturated with respect to the input light is also increased at the same time. By dividing the amplifying unit into a plurality of parts and increasing the amplification degree in the front stage part and decreasing the amplification degree in the rear stage part, it is possible to efficiently perform the saturation amplification. The modulation unit amplifies or attenuates the output light by the modulation input signal current to modulate the intensity. When the optical phase is modulated by the modulation input signal current, phase modulation is performed, and when the optical frequency is modulated, frequency modulation is performed. Here, the wavelength of the output light subjected to saturation amplification and modulation is the same as the wavelength of the input light to the output intensity saturation type amplification modulator.
Therefore, when the output intensity saturated amplification modulator 31 or 32 is applied to the optical transmission / reception apparatus of the slave device described in the embodiment, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal. It is unnecessary to control or maintain the wavelength of the upstream optical signal with high accuracy.
(Embodiment 7)
An optical transmission / reception apparatus including an output intensity saturated amplification modulator with a reflective film will be described. A normal semiconductor optical amplifier performs optical amplification using a region where output light is linearly amplified with respect to input light. Furthermore, the optical signal incident from the incident port on the incident end surface is amplified and output from the output port on the output end surface facing the incident end surface. On the other hand, the output intensity saturation type amplifying modulator with a reflection film actively utilizes a region where the intensity of the output light is saturated and amplified with respect to the input light in the semiconductor optical amplifier, and also performs modulation. Furthermore, the end face opposite to the incident end face is coated with a film having a higher reflectance than that of the cleaved state, and the optical signal incident from the entrance end of the incident end face is saturated, amplified, attenuated, and reflected by the coated reflecting film. After that, the reflection type configuration is such that the downstream optical signal is transmitted from the incident end face.
FIG. 10 shows a schematic cross section of the output intensity saturated amplification modulator with a reflective film. In FIG. 10, 33 is an amplification modulator, 37 is an output intensity saturated amplification modulator with a reflection film, 39 is an entrance / exit, and 40 is a reflection film.
In FIG. 10, saturation amplification and attenuation are performed on the incident light from the incident / exit port 39 by the amplification modulation unit 33 by the input signal. The optical signal that has been amplified and modulated by saturation amplification and attenuation is reflected by the reflective film 40 and is emitted from the entrance / exit port 39. Since the emitted optical signal saturates, amplifies and attenuates the incident light, its wavelength is the same as that of the incident light. The amplification degree as an amplifier is determined by the magnitude of the input signal current to the electrode provided in the amplification modulation section. Increasing the input signal current increases the amplification. In addition, the saturation point at which the intensity of the output light is saturated with respect to the input light is also increased at the same time. When the input signal current is reduced, the amplification degree of the input light is reduced or attenuated. When the optical phase is modulated by the input signal current, phase modulation is performed, or when the optical frequency is modulated, frequency modulation is performed.
FIG. 11 shows a schematic cross section of another output intensity saturated amplification modulator with a reflective film. The above-described output intensity saturated amplification modulator performs saturation amplification and modulation with one electrode. This output intensity saturation type amplifying modulator is obtained by separating a saturation amplifying unit and a modulating unit. Therefore, the control terminal is also separated into an amplification control terminal and a modulation input terminal. In FIG. 11, 35 is an amplifying unit, 36 is a modulating unit, 38 is an output intensity saturated amplification modulator with a reflecting film, 39 is an input / output port, and 40 is a reflecting film.
In FIG. 11, saturation amplification is performed by an amplification unit 35 with respect to incident light from an input / output port 39 by a control input signal from an amplification control terminal (not shown), and a modulation input terminal (not shown) is formed by a modulation unit 36. The signal is modulated by the modulation input signal from The optical signal that has been amplified and modulated by saturation amplification and attenuation is reflected by the reflective film 40 and is emitted from the entrance / exit port 39. Since the emitted optical signal saturates, amplifies and attenuates the incident light, its wavelength is the same as that of the incident light.
The amplification degree as an amplifier is determined by the magnitude of the control input signal current to the electrode provided in the amplification section. When the control input signal current is increased, the degree of amplification is also increased. In addition, the saturation point at which the intensity of the output light is saturated with respect to the input light is also increased at the same time. By dividing the amplifying unit into a plurality of parts and increasing the amplification degree in the front stage part and decreasing the amplification degree in the rear stage part, it is possible to efficiently perform the saturation amplification. The modulation unit amplifies or attenuates the output light by the modulation input signal current to modulate the intensity. When the optical phase is modulated by the modulation input signal current, phase modulation is performed, and when the optical frequency is modulated, frequency modulation is performed.
Therefore, the output intensity saturated amplification modulator 37 or 38 with a reflective film uses the same optical fiber for transmission and reception of downstream optical signals and transmission of upstream optical signals, which will be described in the embodiments, as a slave optical transceiver. When applied to a slave optical transmitter / receiver used for bidirectional optical transmission, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal, and the wavelength of the upstream optical signal at the slave device can be controlled with high accuracy. It was unnecessary to maintain and maintain.
(Embodiment 8)
The present embodiment is an optical transmission / reception apparatus including an output intensity saturated amplification modulator with a reflective film, and a bidirectional optical transmission system using the optical transmission / reception apparatus. FIG. 12 shows the configuration of an optical transmission / reception device including an output intensity saturated amplification modulator with a reflective film. In FIG. 12, 15 is an optical fiber, 17 is a slave optical coupling circuit, 18 is a slave optical receiver, 19 is a slave optical transmitter, 22 is a receiver, 23 is a driver, and 37 is a reflective film. This is an output intensity saturated amplification modulator.
In FIG. 12, the downstream optical signal that has propagated through the optical fiber 15 is partially received by the optical combining / branching circuit 17 by the optical receiving unit of the optical receiving circuit 18. The other downstream optical signals branched by the optical coupling / branching circuit 17 enter the output intensity saturated amplification modulator 37 with a reflecting film, are saturated, amplified, and modulated, and then return to the optical coupling / branching circuit 17. The returned optical signal propagates through the optical fiber 15 as an upstream optical signal. The wavelength of the returned optical signal is the same as the wavelength of the downstream optical signal. Here, the same effect can be obtained even if the output intensity saturated amplification modulator 37 with a reflective film is replaced with the output intensity saturated amplification modulator 38 with a reflective film.
Since the output intensity saturation type amplifying modulator with a reflecting film has a common entrance and exit, bi-directional transmission using the same optical fiber for downstream optical signal transmission and upstream optical signal transmission described in the embodiment. Effective for optical transmission systems. When the output intensity saturation type amplifying modulator with a reflective film is applied to these transmission systems, as is apparent from a comparison between FIG. 12 and FIG. 4B, FIG. The optical branch circuit 21) is not required. For this reason, the optical loss accompanying branching also decreases.
Therefore, the output intensity saturated amplification modulator with the reflection film is used as a slave optical transmitter / receiver, in particular, bi-directional transmission using the same optical fiber for downstream optical signal transmission and upstream optical signal transmission described in the embodiments. When applied to an optical transmission / reception device of a slave device used in an optical transmission system, the wavelength of an upstream optical signal can be made to follow the wavelength of a downstream optical signal, and the wavelength of the upstream optical signal in the slave device can be controlled with high accuracy. , Could be unnecessary to maintain. Furthermore, in the one-core optical fiber direction multiplexing bidirectional transmission and the one-core optical fiber bidirectional-wavelength multiplexing multipoint transmission system, it is possible to reduce the number of optical branch circuits and the optical loss.
(Embodiment 9)
An optical transmission / reception apparatus including an output intensity saturation type amplification modulator having a saturation amplification unit and a modulation unit will be described. As the saturation amplification unit, semiconductor optical amplification using a region where the intensity of output light is saturated and amplified with respect to input light is used. As the modulation unit, semiconductor absorption modulation that can be driven with a small and low voltage is used. Absorption type modulation can be performed at high speed.
FIG. 13 shows a schematic structure of the output intensity saturated amplification modulator. In FIG. 13, 61 is an output intensity saturated amplification modulator having a saturation amplification unit and a modulation unit, 62 is a saturation amplification unit, 63 is a modulation unit, 64 is a semiconductor active layer for realizing semiconductor optical amplification, and 65 is for modulation. An absorption modulation layer.
In FIG. 13, saturation amplification of the input signal is performed on the input light by the saturation amplification unit 62, the bias component is amplified, the signal component is compressed, and further modulated by the modulation unit 63. The modulation unit 63 realizes absorption modulation, and is not limited by the carrier lifetime of the active layer, so that high-speed modulation is possible. In the present modulation unit, the modulation efficiency is not dependent on the wavelength of the input light because the absorption edge is set on the shorter wavelength side than the wavelength used.
Therefore, when the output intensity saturated amplification modulator 61 is applied to the optical transmission / reception apparatus of the slave device described in the embodiment, the wavelength of the upstream optical signal can be made to follow the wavelength of the downstream optical signal. It was unnecessary to control or maintain the wavelength of the optical signal with high accuracy.
(Embodiment 10)
The present embodiment is a bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength time-division multiplex multipoint transmission is performed between a master device and a plurality of slave devices. The configuration of the embodiment of the present invention is shown in FIG. In FIG. 14, 25 is an optical transmission circuit of the main apparatus, 26 is an optical reception circuit of the main apparatus, 15-1 and 15-2 are optical fibers, and 16-1 and 16-2 are wavelengths provided in the middle of the optical fibers. Multiplex circuits, 18-1 to 18-N are optical receiver circuits of the slave devices, and 19-1 to 19-N are optical transmitter circuits of the slave devices. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11-1 to 11-N represent two or more optical transmission circuits. In FIG. 14, the downward arrow indicates the downward transmission direction, and the upward arrow indicates the upward transmission direction.
A configuration of a system that performs bidirectional transmission between the master device and a plurality of slave devices will be described. In FIG. 14, the optical transmission circuit 25 of the main apparatus transmits each downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal, to the slave apparatus. At that time, in the optical transmission circuit 25 of the main apparatus, the wavelength of the wavelength tunable light source included therein is set to N wavelengths (λ 1 ~ Λ N ) Is assigned. The wavelength to be assigned is λ for the optical signal transmitted to the optical receiving circuit 18-N of the slave device. N Is the wavelength. That is, the optical transmission circuit 25 of the main device transmits an optical signal in a different time region and wavelength for each slave device.
The wavelength multiplexing circuit 16-1 provided in the middle of the optical fiber 15-1 separates the wavelength of each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 18-1 to 18-N of the respective slave devices detect signal components from the downstream optical signal received through the optical fiber 15-1. Each of the slave optical transmission circuits 19-1 to 19-N transmits, to the optical fiber 15-2, an upstream optical signal obtained by modulating a part of the received downstream optical signal with an upstream signal by a saturation amplification / attenuation circuit. . Since the downstream optical signal is saturated and amplified by the output intensity saturation type amplifying modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as that of the downstream optical signal. The wavelength multiplexing circuit 16-2 provided in the middle of the optical fiber 15-2 has different wavelengths (λ transmitted from a plurality of optical transmission circuits 19-1 to 19-N. 1 ~ Λ N ) Is multiplexed toward the main unit. The optical receiving circuit 26 of the main device detects the upstream signal from the received upstream optical signal.
Next, the operation in this configuration will be described. For transmission of the downlink signal, the time domain is separated for each signal transmitted to the receiving circuit of the slave device. Further, the wavelength of the tunable laser is changed for each signal transmitted to the receiving circuit of the slave device. For example, when transmitting to the receiving circuit 18-1 of the slave device, the wavelength λ 1 And the time domain is t 1 The downstream optical signal is transmitted at. The operation of modulating the light with the downstream signal is the same as in FIG. In the time domain, the receiving circuit of the slave device that receives each time slot may be changed, or may be each block in which information of a certain length is collected. The interval between the time domain of the optical signal transmitted to the receiving circuit of a predetermined slave device and the time domain of the optical signal transmitted to the receiver circuit of another slave device may be adjusted in advance according to the distance from the plurality of slave devices. However, it is also possible to leave a certain interval. The wavelength / time-division multiplexed optical signals are separated for each slave device by the wavelength multiplexing circuit 16-1, and received by the optical receiver circuits 18-1 to 18-N of the slave devices. The downstream signal reception operation in the optical receiving circuits 18-1 to 18-N is the same as that in FIG. The optical receiving circuits 18-1 to 18-N receive optical signals separated for each wavelength, in other words, for each time domain.
The upstream signal transmission operation is the same as the saturation amplification and modulation operation shown in FIG. 3, but the upstream optical signal is transmitted when the downstream optical signal arrives at each slave device. The upstream optical signal from each slave device is multiplexed by the wavelength multiplexing circuit 16-2 and received by the optical receiving circuit 26 of the master device. The time domain interval is set when transmitting from the master device to the slave device so that the upstream optical signals from the slave devices do not overlap when received by the optical receiver circuit 26. The downstream optical signal and upstream optical signal are transmitted using different optical fibers. By operating in this way, two-core optical fiber bidirectional / wavelength time division multiplex multipoint transmission is performed.
In the main apparatus, instead of the optical receiving circuit 25, as shown in FIG. 5, the wavelength multiplexing circuit 13-2 of the main apparatus and the optical receiving circuits 12-1 to 12-N of the plurality of main apparatuses may be used. With such a configuration, the time domain of the optical signal transmitted to the receiving circuit of the predetermined slave device so that the upstream optical signal from each slave device does not overlap regardless of the distance difference from the master device to each slave device It is not necessary to set the time domain interval of the optical signal transmitted to the receiving circuit of the other slave device.
Here, the wavelength assigned to each time domain is λ 1 ~ Λ N It is not necessary to assign all of these, and can be changed according to the amount of information transmitted to each slave device. Further, the length of the time domain is not constant for each slave device, and can be changed according to the amount of information transmitted to each slave device.
Therefore, the optical transmission circuit of the main device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the slave optical transmission circuit is saturated and amplified. -By adopting a configuration in which an upstream optical signal modulated with an upstream signal by an attenuation circuit is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.
Also, the optical transmission circuit of the slave device transmits the upstream optical signal having the same wavelength as the downstream optical signal by the output intensity saturation type amplifying modulator, so that the wavelength of the upstream optical signal is controlled with high precision to the wavelength multiplexing circuit. No longer need to be maintained or maintained.
Further, in the optical transmission circuit of the slave device, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths, the type of the slave device is not different for each wavelength, and the slave device of the same type is arbitrarily set. It can be applied to a slave device. That is, interoperability between the slave devices can be ensured.
(Embodiment 11)
This embodiment is a bidirectional optical transmission system in which a single-core optical fiber bidirectional / wavelength time-division multiplex multipoint transmission is performed between a master device and a plurality of slave devices. The configuration of the embodiment of the present invention is shown in FIG. In FIG. 15, 25 is the optical transmission circuit of the main apparatus, 26 is the optical reception circuit of the main apparatus, 15-1 and 15-2 are optical fibers, and 16-1 and 16-2 are wavelengths provided in the middle of the optical fibers. Multiplex circuits, 18-1 to 18-N are optical receiver circuits of the slave devices, and 19-1 to 19-N are optical transmitter circuits of the slave devices. Here, the symbol N is used to represent two or more. For example, the optical transmission circuits 11-1 to 11-N represent two or more optical transmission circuits. In FIG. 15, the downward arrow indicates the downward transmission direction, and the upward arrow indicates the upward transmission direction.
A configuration of a system that performs bidirectional transmission between the master device and a plurality of slave devices will be described. In FIG. 15, the optical transmission circuit 25 of the main device transmits each downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal, to the slave device. At that time, in the optical transmission circuit 25 of the main apparatus, the wavelength of the wavelength tunable light source included therein is set to N wavelengths (λ 1 ~ Λ N ) Is assigned. The wavelength to be assigned is λ for the optical signal transmitted to the optical receiving circuit 18-N of the slave device. N Is the wavelength. That is, the optical transmission circuit 25 of the main device transmits an optical signal in a different time region and wavelength for each slave device.
A wavelength multiplexing circuit 16 provided in the middle of the optical fiber 15 separates each downstream optical signal toward each slave device according to the wavelength. The optical receiving circuits 18-1 to 18-N of the respective slave devices detect signal components from the downstream optical signal received through the optical fiber 15-1. Each of the slave optical transmission circuits 19-1 to 19 -N transmits, to the optical fiber 15, an upstream optical signal obtained by modulating a part of the received downstream optical signal with an upstream signal by a saturation amplification / attenuation circuit. Since the downstream optical signal is saturated and amplified by the output intensity saturation type amplifying modulator of the optical transmission circuit of the slave device, the wavelength to be transmitted is the same as that of the downstream optical signal. The wavelength multiplexing circuit 16 provided in the middle of the optical fiber 15 has different wavelengths (λ) transmitted from a plurality of optical transmission circuits 19-1 to 19-N. 1 ~ Λ N ) Is multiplexed toward the main unit. The optical receiving circuit 26 of the main device detects the upstream signal from the received upstream optical signal.
Next, the operation in this configuration will be described. For transmission of the downlink signal, the time domain is separated for each signal transmitted to the receiving circuit of the slave device. Further, the wavelength of the tunable laser is changed for each signal transmitted to the receiving circuit of the slave device. For example, when transmitting to the receiving circuit 18-1 of the slave device, the wavelength λ 1 And the time domain is t 1 The downstream optical signal is transmitted at. The operation of modulating the light with the downstream signal is the same as in FIG. In the time domain, the receiving circuit of the slave device that receives each time slot may be changed, or may be each block in which information of a certain length is collected. The interval between the time domain of the optical signal transmitted to the receiving circuit of a predetermined slave device and the time domain of the optical signal transmitted to the receiver circuit of another slave device may be adjusted in advance according to the distance from the plurality of slave devices. However, it is also possible to leave a certain interval. The wavelength / time-division multiplexed optical signals are separated for each slave device by the wavelength multiplexing circuit 16 and received by the optical receiver circuits 18-1 to 18-N of the slave devices. The downstream signal reception operation in the optical receiving circuits 18-1 to 18-N is the same as that in FIG. The optical receiving circuits 18-1 to 18-N receive optical signals separated for each wavelength, in other words, for each time domain.
The upstream signal transmission operation is the same as the saturation amplification and modulation operation shown in FIG. 3, but the upstream optical signal is transmitted when the downstream optical signal arrives at each slave device. The upstream optical signal from each slave device is multiplexed by the wavelength multiplexing circuit 16 and received by the optical receiving circuit 26 of the main device. The time domain interval is set when transmitting from the master device to the slave device so that the upstream optical signals from the slave devices do not overlap when received by the optical receiver circuit 26. The downstream optical signal and upstream optical signal are transmitted using the same optical fiber. By operating in this way, single-core optical fiber bidirectional / wavelength time division multiplex multipoint transmission is performed.
In the main apparatus, instead of the optical receiving circuit 25, as shown in FIG. 6, the wavelength multiplexing circuit 13-2 of the main apparatus and the optical receiving circuits 12-1 to 12-N of the plurality of main apparatuses may be used. With such a configuration, the time domain of the optical signal transmitted to the receiving circuit of the predetermined slave device so that the upstream optical signal from each slave device does not overlap regardless of the distance difference from the master device to each slave device It is not necessary to set the time domain interval of the optical signal transmitted to the receiving circuit of the other slave device.
Here, the wavelength assigned to each time domain is λ 1 ~ Λ N It is not necessary to assign all of these, and can be changed according to the amount of information transmitted to each slave device. Further, the length of the time domain is not constant for each slave device, and can be changed according to the amount of information transmitted to each slave device.
Therefore, the optical transmission circuit of the main device transmits a downstream optical signal in which a bias component is superimposed on the signal component modulated by the downstream signal to the optical fiber, and a part of the downstream optical signal received by the slave optical transmission circuit is saturated and amplified. -By adopting a configuration in which an upstream optical signal modulated with an upstream signal by an attenuation circuit is transmitted to the optical fiber, the slave device can perform bidirectional transmission without using a light emitting element.
In addition, the optical transmission circuit of the slave device transmits the upstream optical signal having the same wavelength as the downstream optical signal by the output intensity saturation type amplifying modulator, so that the wavelength of the upstream optical signal is set to the wavelength multiplexing circuit or the optical multiplexing / branching circuit. It is no longer necessary to control and maintain with high precision.
Further, in the optical transmission circuit of the slave device, when the output intensity saturation amplification function of the semiconductor optical amplifier is operated over a wide range of wavelengths, the type of the slave device is not different for each wavelength, and the slave device of the same type is arbitrarily set. It can be applied to a slave device. That is, interoperability between the slave devices can be ensured.
In a bidirectional optical transmission system in which directional multiplexing bidirectional / wavelength multiplexing multipoint transmission is performed using a single-core optical fiber, a downstream signal and an upstream signal are transmitted on the same optical fiber at the same wavelength. For this reason, when an upstream signal is received by the main apparatus, there may be mutual interference with a downstream signal reflected in the middle of the optical fiber. In the present embodiment, since the drive current of the light emitting element is controlled and the signal component is superimposed on the downlink signal, the spectrum width of the downlink signal light can be widened. When the spectrum width of the signal light is widened, mutual interference between the upstream signal and the downstream signal reflected in the middle of the line is suppressed, and noise added to the upstream signal can be suppressed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 2 is an operation diagram of the bidirectional optical transmission system of the present invention.
FIG. 3 is an operation diagram of the bidirectional optical transmission system of the present invention.
FIG. 4 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 5 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 6 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 7 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 8 is a schematic structural diagram of an output intensity saturation type amplifying modulator showing an embodiment of the present invention.
FIG. 9 is a schematic structural diagram of an output intensity saturation type amplifying modulator showing an embodiment of the present invention.
FIG. 10 is a schematic cross-sectional view of an output intensity saturated amplification modulator with a reflecting film showing an embodiment of the present invention.
FIG. 11 is a schematic cross-sectional view of an output intensity saturated amplification modulator with a reflecting film showing an embodiment of the present invention.
FIG. 12 is a configuration diagram of an optical transmission / reception apparatus including an output intensity saturated amplification modulator with a reflective film.
FIG. 13 is a schematic structural diagram of an output intensity saturation type amplifying modulator showing an embodiment of the present invention.
FIG. 14 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 15 is a configuration diagram of a bidirectional optical transmission system showing an embodiment of the present invention.
FIG. 16 is a configuration diagram of a conventional bidirectional optical transmission system.
FIG. 17 is an operation diagram of the conventional bidirectional optical transmission system.
FIG. 18 is a configuration diagram of a conventional bidirectional optical transmission system.
The reference symbols in the figure are as follows. 11, 11-1, 11-2, 11 -N are optical transmission circuits of the main device, 12, 12-1, 12-2, 12 -N are optical reception circuits of the main device, and 13, 13-1, 13-. 2 is a wavelength division multiplexing circuit of the main device, 14, 14-1, 14-2, and 14-N are optical multiplexing and branching circuits of the main device, 15, 15-1, and 15-2 are optical fibers, 16, 16-1, and 16 2 is a wavelength multiplexing circuit, 17, 17-1, 17-2, and 17 -N are optical multiplexing and branching circuits of slave devices, 18, 18-1, 18-2, and 18 -N are optical receiving circuits of slave devices, 19 , 19-1, 19-2, and 19 -N are slave optical transmission circuits, 21 is an optical branching circuit, 22 is an optical receiving unit, 23 is a driving unit, 24 is an output intensity saturated amplification modulator, and 25 is a main unit. An optical transmission circuit of the apparatus, 26 an optical reception circuit of the main apparatus, 31 an output intensity saturated amplification modulator, 32 an output intensity saturation amplification modulator, 33 Amplifying and modulating unit 34 is an emission port, 35 is an amplification unit, 36 is a modulation unit, 37 is an output intensity saturated amplification modulator with a reflective film, 38 is an output intensity saturated amplification modulator with a reflective film, and 39 is an incident / exit port. , 40 is a reflective film, 41, 41-1, 41-2, and 41-N are optical transmission circuits of the main device, 42, 42-1, 42-2, and 42-N are optical reception circuits of the main device, and 43 is Optical receiver 44, optical transmitter 45-1, 45-2, wavelength multiplexing circuit of main device, 48, 48-1, 48-2, 48 -N optical receiver circuit of slave device 49, 49- 1, 49-2, 49 -N are slave optical transmission circuits, 61 is an output intensity saturated amplification modulator, 62 is a saturation amplification unit, 63 is a modulation unit, 64 is a semiconductor active layer, and 65 is an absorption modulation layer. is there.

Claims (16)

主装置と従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向伝送する双方向光伝送方式であって、
前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を前記第一の光ファイバに向けて送信する光送信回路と、前記第二の光ファイバを通して受信した上り光信号から上り信号を検出する光受信回路とを備え、
前記従装置は、
前記第一の光ファイバを通して受信した前記下り光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の一方から前記信号成分を検出する光受信回路と、
前記光分岐回路の分岐する前記下り光信号の他方を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記第二の光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式。A bidirectional optical transmission system for bidirectional transmission of a two-core optical fiber between a master device and a slave device using a first optical fiber and a second optical fiber,
The main apparatus includes: an optical transmission circuit that transmits a downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal toward the first optical fiber; and an upstream optical signal that is received through the second optical fiber. And an optical receiving circuit for detecting an upstream signal from
The slave device is
An optical branch circuit for branching the downstream optical signal received through the first optical fiber ;
An optical receiver circuit for detecting the signal component from one of the downstream optical signals branched by the optical branch circuit ;
An optical transmission circuit configured to transmit the upstream optical signal obtained by modulating the other downstream optical signal branched by the optical branching circuit with the upstream signal by a saturation amplification / attenuation circuit toward the second optical fiber. Characteristic bidirectional optical transmission system. 主装置と従装置との間を１芯の光ファイバで方向多重双方向伝送する双方向光伝送方式であって、
前記主装置は、
下り信号で変調した信号成分にバイアス成分を重畳した下り光信号を前記光ファイバに向けて送信する光送信回路と、
前記光ファイバを通して受信した上り光信号から上り信号を検出する光受信回路とを備え、
前記従装置は、
前記光ファイバを通して受信した前記下り光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の一方から前記信号成分を検出する光受信回路と、
前記光分岐回路の分岐する前記下り光信号の他方を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式。A bidirectional optical transmission system that performs directional multiplexing and bidirectional transmission between a master device and a slave device using a single-core optical fiber,
The main unit is
An optical transmission circuit that transmits a downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal toward the optical fiber;
An optical receiving circuit for detecting an upstream signal from an upstream optical signal received through the optical fiber;
The slave device is
An optical branch circuit for branching the downstream optical signal received through the optical fiber ;
An optical receiver circuit for detecting the signal component from one of the downstream optical signals branched by the optical branch circuit ;
An optical transmission circuit configured to transmit the upstream optical signal obtained by modulating the other of the downstream optical signals branched by the optical branching circuit with the upstream signal by a saturation amplification / attenuation circuit toward the optical fiber. Bidirectional optical transmission method. 請求項２に記載の主装置と従装置との間を１芯の光ファイバで方向多重双方向伝送する双方向光伝送方式において、前記飽和増幅・減衰回路が、半導体光増幅器であって、前記下り光信号の入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、前記下り光信号の入射端面から送出する反射型構成であることを特徴とする双方向光伝送方式。  3. A bidirectional optical transmission system that performs directional multiplexing bidirectional transmission between a main device and a slave device according to claim 2 using a single-core optical fiber, wherein the saturation amplification / attenuation circuit is a semiconductor optical amplifier, and Bidirectional optical transmission characterized in that a coating having a higher reflectivity than that of the cleaved state is coated on the end face facing the incident end face of the downstream optical signal, and is transmitted from the incident end face of the downstream optical signal. method. 主装置と複数の従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向・波長多重マルチポイント伝送する双方向光伝送方式であって、
前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を前記第一の光ファイバに向けて送信する複数の光送信回路と、前記第二の光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する複数の光受信回路とを備え、
前記複数の従装置は、
それぞれ、前記第一の光ファイバを通して受信した前記下り光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の一方から前記信号成分を検出する光受信回路と、
それぞれ、前記光分岐回路の分岐する前記下り光信号の他方を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記第二の光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式。A bi-directional optical transmission system that performs two-core optical fiber bi-directional / wavelength multiplexing multi-point transmission between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber,
The main device receives a plurality of optical transmission circuits that transmit respective downstream optical signals, in which a bias component is superimposed on a signal component modulated by a downstream signal, toward the first optical fiber, and the second optical fiber. A plurality of optical receiving circuits for detecting upstream signals from the respective upstream optical signals,
The plurality of slave devices are:
An optical branch circuit for branching the downstream optical signal received through the first optical fiber , and
An optical receiver circuit for detecting the signal component from one of the downstream optical signals branched by the optical branch circuit ;
And an optical transmission circuit for transmitting the upstream optical signal obtained by modulating the other of the downstream optical signals branched by the optical branching circuit with the upstream signal by a saturation amplification / attenuation circuit toward the second optical fiber. A bidirectional optical transmission system characterized by this. 主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式であって、
前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を前記光ファイバに向けて送信する複数の光送信回路と、前記光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する複数の光受信回路とを備え、
前記複数の従装置は、
それぞれ、前記光ファイバを通して受信した前記下り光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の一方から前記信号成分を検出する光受信回路と、
それぞれ、前記光分岐回路の分岐する前記下り光信号の他方を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記光ファイバに向けて送信する光送信回路と
を備えることを特徴とする双方向光伝送方式。A bidirectional optical transmission system that performs directional multiplexing and wavelength multiplexing multipoint transmission between a master device and a plurality of slave devices using a single-core optical fiber,
The main apparatus includes a plurality of optical transmission circuits that transmit a downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal toward the optical fiber, and an upstream optical signal received through the optical fiber. A plurality of optical receiving circuits for detecting upstream signals from
The plurality of slave devices are:
An optical branch circuit for branching the downstream optical signal received through the optical fiber , and
An optical receiver circuit for detecting the signal component from one of the downstream optical signals branched by the optical branch circuit ;
An optical transmission circuit configured to transmit the upstream optical signal obtained by modulating the other downstream optical signal branched by the optical branching circuit with the upstream signal by a saturation amplification / attenuation circuit toward the optical fiber. Bidirectional optical transmission method. 請求項５に記載の主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長多重マルチポイント伝送する双方向光伝送方式において、前記飽和増幅・減衰回路が、半導体光増幅器であって、前記下り光信号の入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、前記下り光信号の入射端面から送出する反射型構成であることを特徴とする双方向光伝送方式。  6. The bidirectional optical transmission system in which the master apparatus and the plurality of slave apparatuses according to claim 5 are unidirectional optical fiber and multiplex multipoint transmission using a single optical fiber, wherein the saturation amplification / attenuation circuit is a semiconductor optical amplifier. And a reflection type structure in which a film having a higher reflectance than that of a cleaved state is coated on an end face facing the incident end face of the downstream optical signal, and is transmitted from the incident end face of the downstream optical signal. Bidirectional optical transmission method. 主装置と複数の従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式であって、
前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を従装置毎の波長と時間領域に分離して前記第一の光ファイバに向けて送信する光送信回路と、前記第二の光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する少なくとも１の光受信回路とを備え、
前記複数の従装置は、
それぞれ、前記第一の光ファイバを通して受信した前記下り光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の一方から前記信号成分を検出する光受信回路と、
それぞれ、前記光分岐回路の分岐する前記下り光信号の他方を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記第二の光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式。A bi-directional optical transmission system that performs two-core optical fiber bidirectional / wavelength time division multiplexing multipoint transmission between a master device and a plurality of slave devices using a first optical fiber and a second optical fiber,
The main apparatus is an optical transmission circuit that separates each downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal into a wavelength and a time domain for each slave apparatus and transmits the signals to the first optical fiber. And at least one optical receiving circuit for detecting an upstream signal from each upstream optical signal received through the second optical fiber,
The plurality of slave devices are:
An optical branch circuit for branching the downstream optical signal received through the first optical fiber , and
An optical receiver circuit for detecting the signal component from one of the downstream optical signals branched by the optical branch circuit ;
And an optical transmission circuit for transmitting the upstream optical signal obtained by modulating the other of the downstream optical signals branched by the optical branching circuit with the upstream signal by a saturation amplification / attenuation circuit toward the second optical fiber. A bidirectional optical transmission system characterized by this. 請求項７に記載の主装置と複数の従装置との間を第一の光ファイバと第二の光ファイバで２芯光ファイバ双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式において、前記光送信回路に光出力の波長を従装置毎の波長に可変できる波長可変光源を用いたことを特徴とする双方向光伝送方式。  A bidirectional optical transmission system in which a two-core optical fiber bidirectional / wavelength time division multiplex multipoint transmission is performed between a master device and a plurality of slave devices according to claim 7 using a first optical fiber and a second optical fiber. A bidirectional optical transmission system characterized in that a wavelength variable light source capable of changing the wavelength of the optical output to the wavelength of each slave device is used in the optical transmission circuit. 主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長多重時分割マルチポイント伝送する双方向光伝送方式であって、
前記主装置は、下り信号で変調した信号成分にバイアス成分を重畳したそれぞれの下り光信号を従装置毎の波長と時間領域に分離して前記光ファイバに向けて送信する光送信回路と、前記光ファイバを通して受信したそれぞれの上り光信号から上り信号を検出する少なくとも１の光受信回路とを備え、
前記複数の従装置は、それぞれ、前記光ファイバを通して受信した前記下り光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の一方から前記信号成分を検出する光受信回路と、
それぞれ、前記光分岐回路の分岐する前記下り光信号の他方を飽和増幅・減衰回路によって前記上り信号で変調した前記上り光信号を前記光ファイバに向けて送信する光送信回路とを備えることを特徴とする双方向光伝送方式。A bidirectional optical transmission system that performs directional multiplexing bidirectional wavelength division multiplexing time division multipoint transmission between a master device and a plurality of slave devices using a single-core optical fiber,
The main device is an optical transmission circuit that separates each downstream optical signal in which a bias component is superimposed on a signal component modulated by a downstream signal into a wavelength and a time domain for each slave device, and transmits the optical signal toward the optical fiber; And at least one optical receiving circuit for detecting an upstream signal from each upstream optical signal received through an optical fiber,
Each of the plurality of slave devices includes an optical branch circuit that branches the downstream optical signal received through the optical fiber ,
An optical receiver circuit for detecting the signal component from one of the downstream optical signals branched by the optical branch circuit ;
And an optical transmission circuit for transmitting the upstream optical signal obtained by modulating the other of the downstream optical signals branched by the optical branch circuit with the upstream signal by a saturation amplification / attenuation circuit toward the optical fiber. Bidirectional optical transmission method. 請求項９に記載の主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式において、前記飽和増幅・減衰回路が、半導体光増幅器であって、前記下り光信号の入射端面と対向する端面に劈開状態に比べて高反射率を有する膜をコーティングし、前記下り光信号の入射端面から送出する反射型構成であることを特徴とする双方向光伝送方式。  10. The bidirectional optical transmission system in which the master device and the plurality of slave devices according to claim 9 are transmitted in a direction-multiplexed bidirectional / wavelength time-division multiplexed multipoint using a single optical fiber. An amplifier having a reflection type configuration in which a film having a higher reflectance than that of a cleaved state is coated on an end surface facing the incident end surface of the downstream optical signal, and is transmitted from the incident end surface of the downstream optical signal. Bidirectional optical transmission method. 請求項９に記載の主装置と複数の従装置を１芯の光ファイバで方向多重双方向・波長時分割多重マルチポイント伝送する双方向光伝送方式において、前記光送信回路に光出力の波長を従装置毎の波長に可変できる波長可変光源を用いたことを特徴とする双方向光伝送方式。  10. The bidirectional optical transmission system in which the master apparatus and the plurality of slave apparatuses according to claim 9 perform directional multiplexing bidirectional / wavelength time division multiplexing multipoint transmission with a single optical fiber. A bidirectional optical transmission system characterized by using a wavelength tunable light source that can be tuned to the wavelength of each slave device. 受信した第一の光信号を光分岐回路で分岐して、前記光分岐回路の分岐した前記第一の光信号の片方を飽和増幅・減衰回路によって第二の送信信号で変調した第二の光信号を光ファイバに向けて送信する光送信回路を備える光送受信装置に対して、第一の送信信号で変調した信号成分にバイアス成分を重畳した第一の光信号を送信する光送信回路と、
光ファイバを通して受信した前記第二の光信号から信号成分を検出する光受信回路とを備える光送受信装置。A second optical signal obtained by branching the received first optical signal with an optical branch circuit and modulating one of the first optical signals branched by the optical branch circuit with a second transmission signal by a saturation amplification / attenuation circuit. An optical transmission circuit that transmits an optical transmission circuit that transmits a signal toward an optical fiber, an optical transmission circuit that transmits a first optical signal in which a bias component is superimposed on a signal component modulated by the first transmission signal, and
An optical transmission / reception apparatus comprising: an optical reception circuit that detects a signal component from the second optical signal received through an optical fiber. 信号で変調した信号成分にバイアス成分を重畳した光信号を、光ファイバを通して受信する光受信回路と、
前記受信した光信号を分岐する光分岐回路と、
前記光分岐回路の分岐する前記下り光信号の片方を飽和増幅・減衰回路によって送信する信号で変調して光ファイバに向けて送信する光送信回路とを備える光送受信装置。An optical receiving circuit that receives an optical signal in which a bias component is superimposed on a signal component modulated by a signal through an optical fiber;
An optical branch circuit for branching the received optical signal ;
An optical transmission / reception apparatus comprising: an optical transmission circuit that modulates one of the downstream optical signals branched by the optical branching circuit with a signal transmitted by a saturation amplification / attenuation circuit and transmits the modulated signal toward an optical fiber. 請求項１２に記載の光送受信装置において、前記バイアス成分が前記信号成分の５０％以上、好ましくは１００％以上であることを特徴とする光送受信装置。  13. The optical transceiver according to claim 12, wherein the bias component is 50% or more, preferably 100% or more of the signal component. 請求項１３に記載の光送受信装置において、前記飽和増幅・減衰回路が、制御電流によって増幅度を制御する増幅部と送信する信号によって光信号を変調する変調部とを有する半導体光増幅器であることを特徴とする光送受信装置。  14. The optical transmission / reception device according to claim 13, wherein the saturation amplification / attenuation circuit is a semiconductor optical amplifier having an amplification unit that controls an amplification degree by a control current and a modulation unit that modulates an optical signal by a signal to be transmitted. An optical transceiver characterized by the above. 請求項１３に記載の光送受信装置において、前記飽和増幅・減衰回路が、制御電流によって飽和させる増幅部と送信する信号によって光信号を吸収する変調部とを有する半導体光素子であることを特徴とする光送受信装置。  14. The optical transceiver according to claim 13, wherein the saturation amplification / attenuation circuit is a semiconductor optical device having an amplification unit that is saturated by a control current and a modulation unit that absorbs an optical signal by a transmitted signal. Optical transmission / reception device.
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