JPH08316910A - Optical transmission device - Google Patents
Optical transmission deviceInfo
- Publication number
- JPH08316910A JPH08316910A JP7116003A JP11600395A JPH08316910A JP H08316910 A JPH08316910 A JP H08316910A JP 7116003 A JP7116003 A JP 7116003A JP 11600395 A JP11600395 A JP 11600395A JP H08316910 A JPH08316910 A JP H08316910A
- Authority
- JP
- Japan
- Prior art keywords
- optical
- optical fiber
- transmission line
- signals
- fiber transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
(57)【要約】
【目的】簡単な手法で、偏波スクランブル処理を行わず
にＰＨＢを抑制する。
【構成】互いに波長の異なる直線偏波の光信号を送出す
る複数の光送信器１１１〜１１ｎと、複数の光送信器１
１１〜１１ｎの出力光信号を共に一本に結合する光結合
器１２と、この光結合器１２で結合された光信号を光フ
ァイバケーブルにより伝送する光ファイバ伝送路１３
と、この光ファイバ伝送路１３中に介在され、光ファイ
バケーブルの挿入損失を補償する複数の光増幅器１３１
１〜１３１ｍと、前記光ファイバ伝送路１３の受信側で
個別に各波長の光信号を受信する複数の光受信器１４１
〜１４ｎとを具備し、光結合器１２で複数の光送信器１
１１〜１１ｎの任意の出力光信号を対にして互いに偏波
方向が直交するように、かつ同一振幅レベルとなるよう
にして結合するようにしたことを特徴とする。
(57) [Abstract] [Purpose] A simple method suppresses PHB without performing polarization scrambling. [Structure] A plurality of optical transmitters 111 to 11n for transmitting linearly polarized optical signals having different wavelengths, and a plurality of optical transmitters 1
An optical coupler 12 that couples the output optical signals of 11 to 11n together, and an optical fiber transmission line 13 that transmits the optical signals coupled by the optical coupler 12 by an optical fiber cable.
And a plurality of optical amplifiers 131 interposed in the optical fiber transmission line 13 for compensating the insertion loss of the optical fiber cable.
1 to 131 m, and a plurality of optical receivers 141 that individually receive optical signals of respective wavelengths on the receiving side of the optical fiber transmission line 13.
˜14n, and a plurality of optical transmitters 1 in the optical coupler 12.
It is characterized in that arbitrary output optical signals 11 to 11n are paired and coupled so that the polarization directions thereof are orthogonal to each other and have the same amplitude level.
Description
【０００１】[0001]
【産業上の利用分野】この発明は、例えば長距離光ファ
イバ通信システムに用いられる長距離光伝送装置に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long-distance optical transmission device used in, for example, a long-distance optical fiber communication system.
【０００２】[0002]
【従来の技術】現在、世界中に１００００ｋｍ級の光増
幅器を用いた長距離光ファイバ通信システムの設置が行
われている。しかしながら、最近になって、光増幅器で
信号光と直交する偏波の雑音光が強く発生することが報
告されている。これはエルビウム原子の二つの励振密度
の存在に起因して、一方が一つの偏波の光と相互作用
し、他方がそれと直交偏波の光と相互作用するためであ
ると考えられている。すなわち、信号光がエルビウム原
子の一つの励起状態と強く相互作用するように偏光して
いると、他方の励起状態が強く反転分布し、結果的に多
量のノイズが放出されることになるといわれている。2. Description of the Related Art Currently, long-distance optical fiber communication systems using optical amplifiers of 10,000 km class are installed all over the world. However, recently, it has been reported that noise light having a polarization orthogonal to the signal light is strongly generated in the optical amplifier. It is considered that this is because one of the two interacts with light of one polarization and the other interacts with light of orthogonal polarization due to the existence of two excitation densities of the erbium atom. That is, it is said that if the signal light is polarized so that it strongly interacts with one excited state of the erbium atom, the other excited state has a strong population inversion, resulting in the emission of a large amount of noise. There is.
【０００３】このようなエルビウムドープ光ファイバ増
幅器における偏波依存性は偏波ホールバーニング（Pola
rization Hole Burning ：以下、ＰＨＢと記す）と呼ば
れ、長距離光ファイバ通信システムに多大な信号対雑音
比の劣化をもたらす。The polarization dependence of such an erbium-doped optical fiber amplifier is called polarization hole burning (Pola
rization hole burning (hereinafter referred to as PHB), which causes a great deterioration of the signal-to-noise ratio in the long distance optical fiber communication system.
【０００４】従来では、偏波スクランブル処理によって
ＰＨＢを抑えている。すなわち、伝送前に信号光の偏波
状態をエルビウム原子の平均寿命（１ｍｓ程度）より速
く、二つの直交する偏波状態に切り替えることで、ＰＨ
Ｂを抑制し、信号対雑音比の改善を図っている。このよ
うな偏波スクランブラは、偏波依存位相変調器またはフ
ァラデー回転子で実現できる。Conventionally, PHB is suppressed by polarization scrambling. That is, by switching the polarization state of the signal light to two orthogonal polarization states faster than the average life of the erbium atom (about 1 ms) before transmission,
B is suppressed and the signal-to-noise ratio is improved. Such a polarization scrambler can be realized by a polarization dependent phase modulator or a Faraday rotator.
【０００５】しかしながら、偏波スクランブル処理を行
うと、他の効果によって信号が劣化する。すなわち、偏
波をスクランブルすると、光ファイバと光増幅器におけ
る偏波依存性ロス（Polarization Dependant Loss ：以
下、ＰＤＬと記す）によって受信信号の振幅が変動して
しまう。However, the polarization scrambling process deteriorates the signal due to other effects. That is, when the polarized wave is scrambled, the amplitude of the received signal fluctuates due to polarization dependent loss (hereinafter referred to as PDL) in the optical fiber and the optical amplifier.
【０００６】この問題を防ぐためには、受信帯域より数
倍高い周波数でスクランブルする必要がある。しかし、
高い周波数で偏波をスクランブルするために必要となる
高振幅の電気信号の発生が困難である。また、光スペク
トルも広がることから、波長多重を用いるシステムで
は、チャネル間のクロストークも増加してしまい、波長
分散などによる信号劣化も発生してしまう。To prevent this problem, it is necessary to scramble at a frequency several times higher than the reception band. But,
It is difficult to generate the high amplitude electrical signal needed to scramble the polarization at high frequencies. In addition, since the optical spectrum also spreads, in a system using wavelength multiplexing, crosstalk between channels also increases, and signal deterioration due to chromatic dispersion or the like also occurs.
【０００７】[0007]
【発明が解決しようとする課題】以上述べたように、従
来の光伝送装置において、ＰＨＢを抑制するために偏波
スクランブルを行うと、受信信号の振幅変動または光ス
ペクトルの広がりが発生して信号劣化の起因となり、新
たな問題が生じてしまう。As described above, when polarization scrambling is performed in order to suppress PHB in the conventional optical transmission equipment, the amplitude fluctuation of the received signal or the spread of the optical spectrum occurs and the signal This causes deterioration and causes new problems.
【０００８】この発明は上記の課題を解決するためにな
されたもので、簡単な手法で、偏波スクランブル処理を
行わずにＰＨＢを抑制することのできる光伝送装置を提
供することを目的とする。The present invention has been made to solve the above problems, and an object thereof is to provide an optical transmission apparatus capable of suppressing PHB by a simple method without performing polarization scrambling processing. .
【０００９】[0009]
【課題を解決するための手段】上記目的を達成するため
に第１の発明は、互いに波長の異なる直線偏波の光信号
を送出する複数の光送信器と、前記複数の光送信器の出
力光信号を共に一本に結合する光結合器と、この光結合
器で結合された光信号を光ファイバケーブルにより伝送
する光ファイバ伝送路と、この光ファイバ伝送路中に介
在され、前記光ファイバケーブルの挿入損失を補償する
複数の光増幅器と、前記光ファイバ伝送路の受信側で個
別に各波長の光信号を受信する複数の光受信器とを具備
し、前記光ファイバ伝送路中の全偏波モード分散が被伝
送光信号の光周波数スペクトルの標準偏差の逆数より大
きくなるようにしたことを特徴とする。To achieve the above object, a first invention is to provide a plurality of optical transmitters for transmitting optical signals of linearly polarized waves having different wavelengths, and outputs of the plurality of optical transmitters. An optical coupler for coupling optical signals together, an optical fiber transmission line for transmitting the optical signals coupled by the optical coupler by an optical fiber cable, and the optical fiber interposed in the optical fiber transmission line. A plurality of optical amplifiers for compensating for cable insertion loss and a plurality of optical receivers for individually receiving optical signals of respective wavelengths on the receiving side of the optical fiber transmission line are provided. The polarization mode dispersion is set to be larger than the reciprocal of the standard deviation of the optical frequency spectrum of the transmitted optical signal.
【００１０】第２の発明は、互いに波長の異なる直線偏
波の光信号を送出する複数の光送信器と、前記複数の光
送信器の出力光信号を共に一本に結合する光結合器と、
この光結合器で結合された光信号を光ファイバケーブル
により伝送する光ファイバ伝送路と、この光ファイバ伝
送路中に介在され、前記光ファイバケーブルの挿入損失
を補償する複数の光増幅器と、前記光ファイバ伝送路の
受信側で個別に各波長の光信号を受信する複数の光受信
器と、前記光ファイバ伝送路中の全偏波モード分散が被
伝送光信号の光周波数スペクトルの標準偏差の逆数より
大きくなるように、前記光ファイバ伝送路中に分散配置
される複数の偏波モード分散素子とを具備したことを特
徴とする。A second invention is a plurality of optical transmitters for transmitting linearly polarized optical signals having different wavelengths, and an optical coupler for combining output optical signals of the plurality of optical transmitters together. ,
An optical fiber transmission line for transmitting the optical signal coupled by the optical coupler by an optical fiber cable, a plurality of optical amplifiers interposed in the optical fiber transmission line for compensating the insertion loss of the optical fiber cable, A plurality of optical receivers that individually receive optical signals of each wavelength on the receiving side of the optical fiber transmission line, and the total polarization mode dispersion in the optical fiber transmission line is the standard deviation of the optical frequency spectrum of the transmitted optical signal. It is characterized by comprising a plurality of polarization mode dispersion elements dispersedly arranged in the optical fiber transmission line so as to be larger than the reciprocal number.
【００１１】第３の発明は、互いに波長の異なる直線偏
波の光信号を送出する複数の光送信器と、前記複数の光
送信器の出力光信号を共に一本に結合する光結合器と、
この光結合器で結合された光信号を光ファイバケーブル
により伝送する光ファイバ伝送路と、この光ファイバ伝
送路中に介在され、前記光ファイバケーブルの挿入損失
を補償する複数の光増幅器と、前記光ファイバ伝送路の
受信側で個別に各波長の光信号を受信する複数の光受信
器とを具備し、前記光結合器で前記複数の光送信器の任
意の出力光信号を対にして互いに偏波方向が直交するよ
うに、かつ同一振幅レベルとなるようにして結合するよ
うにしたことを特徴とする。この手法は、特に偏波モー
ド分散が低い光ファイバケーブルを用いる場合に有効で
ある。According to a third aspect of the present invention, a plurality of optical transmitters for transmitting linearly polarized optical signals having different wavelengths, and an optical coupler for coupling the output optical signals of the plurality of optical transmitters together into a single optical coupler. ,
An optical fiber transmission line for transmitting the optical signal coupled by the optical coupler by an optical fiber cable, a plurality of optical amplifiers interposed in the optical fiber transmission line for compensating the insertion loss of the optical fiber cable, A plurality of optical receivers that individually receive optical signals of respective wavelengths on the receiving side of the optical fiber transmission line, and the optical coupler couples arbitrary output optical signals of the plurality of optical transmitters to each other. It is characterized in that the polarization directions are orthogonal to each other and are coupled so that they have the same amplitude level. This method is particularly effective when using an optical fiber cable with low polarization mode dispersion.
【００１２】[0012]
【作用】第１の発明に係る光伝送装置では、光ファイバ
伝送路中の全偏波モード分散が被伝送光信号の光周波数
スペクトルの標準偏差の逆数より大きくなるようにする
ことで、伝送中に波長毎に異なって変動し、光信号全体
の偏光度が下がり、これによってＰＨＢを抑制する。In the optical transmission device according to the first aspect of the present invention, the total polarization mode dispersion in the optical fiber transmission line is set to be larger than the reciprocal of the standard deviation of the optical frequency spectrum of the transmitted optical signal during transmission. And the degree of polarization of the entire optical signal decreases, which suppresses PHB.
【００１３】第２の発明に係る光伝送装置では、光ファ
イバ伝送路中に複数の偏波モード分散素子を分散配置す
ることで、光ファイバ伝送路中の全偏波モード分散が被
伝送光信号の光周波数スペクトルの標準偏差の逆数より
大きくなるようにし、これによってＰＨＢを抑制する。In the optical transmission device according to the second aspect of the present invention, by disposing a plurality of polarization mode dispersion elements in the optical fiber transmission line in a dispersed manner, the total polarization mode dispersion in the optical fiber transmission line is transmitted. To be larger than the reciprocal of the standard deviation of the optical frequency spectrum of, thereby suppressing PHB.
【００１４】第３の発明に係る光伝送装置では、光結合
器で複数の光送信器の任意の出力光信号を対にして互い
に偏波方向が直交するように、かつ同一振幅レベルとな
るようにして結合することで、対となった光信号の周波
数差により偏波状態を回転させ、高い周波数で偏波スク
ランブルした場合と等価にし、これによってＰＨＢを抑
制する。In the optical transmission device according to the third aspect of the present invention, the optical coupler forms a pair of arbitrary output optical signals of the plurality of optical transmitters so that the polarization directions thereof are orthogonal to each other and the same amplitude level is obtained. By coupling with each other, the polarization state is rotated by the frequency difference between the paired optical signals, which is equivalent to the case of polarization scrambling at a high frequency, thereby suppressing PHB.
【００１５】[0015]
【実施例】まず、図３を参照してこの発明の動作原理を
説明する。図３は互いに波長の異なる直線偏波の二つの
光信号を結合した場合の光出力偏波の状態変化を示すも
のである。DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the operating principle of the present invention will be described with reference to FIG. FIG. 3 shows a state change of the optical output polarization when two optical signals of linear polarization having different wavelengths are coupled.
【００１６】いま、λ１、λ２の直線偏波の光信号を光
結合する場合を考える。初めに、図３（ａ）に示すよう
に、それぞれの偏波状態が一致しているものとすると、
結合した光信号の偏波状態も同じになる。しかし、図３
（ｂ）に示すように、λ１とλ２の偏波状態が直交して
いると、結合した信号の偏波状態は、各瞬間で直線とな
るが、その向きは光信号の光周波数に応じて回転する。
このため、光信号全体の時間平均の偏光度をゼロ（無偏
光）にすることができる。Now, consider a case where optical signals of linearly polarized waves of λ1 and λ2 are optically coupled. First, assuming that the respective polarization states are the same, as shown in FIG.
The polarization states of the combined optical signals are the same. However, FIG.
As shown in (b), when the polarization states of λ1 and λ2 are orthogonal to each other, the polarization state of the combined signal becomes a straight line at each moment, but its direction depends on the optical frequency of the optical signal. Rotate.
Therefore, the time-averaged degree of polarization of the entire optical signal can be zero (non-polarized).
【００１７】例えば、１５５０ｎｍ領域で、波長が１ｎ
ｍ離れた互いに直交する二つの直線偏波の光信号を結合
した場合、振幅が同一であるものと仮定すれば、結合し
た光信号の偏波状態は１２６ＧＨｚで回転することにな
る。すなわち、光信号を１２６ＧＨｚで偏波スクランブ
ルした場合と結果的に同じになる。For example, in the 1550 nm region, the wavelength is 1 n
When two linearly polarized optical signals that are orthogonal to each other at a distance of m are combined, assuming that they have the same amplitude, the polarization state of the combined optical signal rotates at 126 GHz. That is, the result is the same as when the optical signal is polarization scrambled at 126 GHz.
【００１８】この効果は、長距離光伝送におけるＰＨＢ
の抑制に利用可能である。特に、偏波スクランブラを用
いずに、各波長の光信号の偏波状態が直交していると、
エルビウム原子の２つの励振密度の反転分布を抑圧でき
ることから、ＰＨＢを抑制できる。そして、各光信号の
光スペクトルが広がらないため、クロストークの発生は
生じない。This effect is due to PHB in long-distance optical transmission.
It can be used to suppress In particular, without using a polarization scrambler, if the polarization state of the optical signal of each wavelength is orthogonal,
Since the population inversion of the two excitation densities of erbium atoms can be suppressed, PHB can be suppressed. Then, since the optical spectrum of each optical signal does not spread, crosstalk does not occur.
【００１９】但し、この効果は光ファイバ伝送路の全偏
波モード分散ＰＭＤの値ｔｄが比較的小さい場合に限定
される。図１は上記の効果を利用した光伝送装置の実施
例の構成を示すもので、１１１〜１１ｎはそれぞれ互い
に異なる波長λ１〜λｎの直線偏波の光信号を同一振幅
で出力する光送信器である。これらの光送信器１１１〜
１１ｎから出力される光信号はそれぞれ光結合器１２に
送出され、１本に結合される。However, this effect is limited to the case where the value td of the total polarization mode dispersion PMD of the optical fiber transmission line is relatively small. FIG. 1 shows a configuration of an embodiment of an optical transmission apparatus utilizing the above effect. Reference numerals 111 to 11n denote optical transmitters that output linearly polarized optical signals having different wavelengths .lamda.1 to .lamda.n with the same amplitude. is there. These optical transmitters 111 to
The optical signals output from 11n are respectively sent to the optical coupler 12 and combined into one.
【００２０】ここで、各光送信器１１１〜１１ｎの光信
号出力端は偏波保持ファイバを通じて光結合器１２と接
続されており、各光信号は他の光信号と対になって互い
に偏波の向きが直交するように調整される。Here, the optical signal output ends of the optical transmitters 111 to 11n are connected to the optical coupler 12 through a polarization maintaining fiber, and each optical signal forms a pair with another optical signal and is polarized with each other. Are adjusted so that the directions of are orthogonal.
【００２１】光結合器１２で結合された光信号は光ファ
イバ伝送路１３に入力される。この光ファイバ伝送路１
３は光ファイバケーブルの複数箇所（約３０ｋｍ毎）に
エルビウムドープ光ファイバ増幅器（以下、ＥＤＦＡと
記す）１３１１〜１３１ｍを介在するようにしたもの
で、ＥＤＦＡ１３１１〜１３１ｍにより光ファイバケー
ブルの挿入損失を補償するようになっている。但し、光
ファイバ伝送路１３の全偏波モード分散ＰＭＤの値ｔｄ
は使用波長域で十分小さいものとする。The optical signal coupled by the optical coupler 12 is input to the optical fiber transmission line 13. This optical fiber transmission line 1
Reference numeral 3 denotes an optical fiber cable in which erbium-doped optical fiber amplifiers (hereinafter referred to as EDFAs) 1311 to 131m are interposed at a plurality of locations (about every 30km). The EDFAs 1311 to 131m compensate for insertion loss of the optical fiber cable. It is supposed to do. However, the value td of the total polarization mode dispersion PMD of the optical fiber transmission line 13
Shall be sufficiently small in the wavelength range used.
【００２２】光ファイバ伝送路１３を通じて伝送された
光信号は光ファイバ端末でｎ系統に分岐されてｎ個の光
受信器１４１〜１４ｎに入力される。各光受信器１４１
〜１４ｎはそれぞれ互いに異なる波長λ１〜λｎの光信
号を受信する機能を有する。The optical signal transmitted through the optical fiber transmission line 13 is branched into n systems at the optical fiber terminal and input to the n optical receivers 141 to 14n. Each optical receiver 141
14n have a function of receiving optical signals of wavelengths λ1 to λn different from each other.
【００２３】すなわち、上記構成による光伝送装置で
は、被伝送光信号がそれぞれ対となって互いに偏波方向
が直交するように結合されているため、結合した光信号
の偏波状態が伝送中にその周波数差に応じて回転し、偏
波スクランブルした場合と結果的に同じになる。That is, in the optical transmission device having the above-mentioned configuration, the transmitted optical signals are paired and coupled so that the polarization directions thereof are orthogonal to each other, so that the polarization states of the coupled optical signals are not transmitted during transmission. It rotates according to the frequency difference, and the result is the same as the case of polarization scrambling.
【００２４】したがって、上記構成によれば、偏波スク
ランブラを用いずに、各波長の光信号の偏波状態が直交
させているため、エルビウム原子の２つの励振密度の反
転分布を抑圧でき、これによってＰＨＢを抑制できる。
このとき、各光信号の光スペクトルが広がらないため、
クロストークの発生は生じない。Therefore, according to the above configuration, since the polarization states of the optical signals of the respective wavelengths are made orthogonal without using the polarization scrambler, the population inversion of the two excitation densities of the erbium atom can be suppressed, This makes it possible to suppress PHB.
At this time, because the optical spectrum of each optical signal does not spread,
No crosstalk occurs.
【００２５】ところで、図１の構成において、光ファイ
バ伝送路１３の全偏波モード分散ＰＭＤの値ｔｄが大き
い場合、その影響で偏波が伝送中に波長毎に異なって変
動する。すなわち、光ファイバの入力で異なる波長の信
号光の偏波状態が一致していても、伝送中に偏波は直交
したりするので、ＰＨＢによる多重雑音の発生をある程
度抑制できる。By the way, in the configuration of FIG. 1, when the value td of the total polarization mode dispersion PMD of the optical fiber transmission line 13 is large, the polarized wave fluctuates for each wavelength during transmission due to the influence thereof. That is, even if the polarization states of the signal lights of different wavelengths match at the input of the optical fiber, the polarizations are orthogonal to each other during transmission, so that the occurrence of multiple noise due to PHB can be suppressed to some extent.
【００２６】そこで、異なる波長の光を偏光を気にせず
に組み合わせ、光ファイバ伝送路１３での偏波モード分
散の値を十分大きくさせ、伝送中に異なる波長の偏波状
態の変動も異ならせる。Therefore, lights of different wavelengths are combined without concern for polarization, the value of polarization mode dispersion in the optical fiber transmission line 13 is made sufficiently large, and the fluctuation of the polarization state of different wavelengths during transmission is also made different. .
【００２７】いま、図４に示すように、光ファイバ伝送
路１３の入力偏波状態を同じにしてみると、光の波長に
よって出力では偏波状態が異なる。すなわち、互いに振
幅と偏光が同じで、光周波数の差がｄｆの光信号を、偏
波モード分散ｔｄを持つ光ファイバで伝送すると、一次
近似ではｔｄ≧２／ｄｆの場合、それぞれの偏波状態が
無相関になる。言い換えれば、全体の信号が無偏光にな
る。As shown in FIG. 4, assuming that the input polarization states of the optical fiber transmission line 13 are the same, the polarization state of the output differs depending on the wavelength of light. That is, when optical signals having the same amplitude and polarization and an optical frequency difference of df are transmitted through an optical fiber having polarization mode dispersion td, when td ≧ 2 / df in the first approximation, the respective polarization states are Becomes uncorrelated. In other words, the entire signal is unpolarized.
【００２８】ＥＤＦＡ１３１１〜１３１ｍと他の部品の
波長依存性を考慮にいれて、伝送距離による光信号の平
均パワースペクトルの例を図５に示す。この場合、光波
長と周波数の平均と標準偏差は下記の式で得られる。FIG. 5 shows an example of the average power spectrum of the optical signal depending on the transmission distance, taking into consideration the wavelength dependence of the EDFAs 1311-131m and other components. In this case, the average and standard deviation of the light wavelength and frequency are obtained by the following formula.
【００２９】[0029]
【数１】 [Equation 1]
【００３０】ここで、λavは平均波長、λは波長、Ｐ
（λ）はパワースペクトル密度、οは波長標準偏差、ο
avは光周波数標準偏差、οf はＥＤＦＡの許容帯域を示
している。Where λ av is the average wavelength, λ is the wavelength, P
(Λ) is the power spectral density, ο is the wavelength standard deviation, ο
av is the optical frequency standard deviation, o f represents the tolerance band of the EDFA.
【００３１】すなわち、もし、偏波モード分散が光ファ
イバ伝送路１３に平均に分散しているとすれば、ｔｄ≧
１／οf となり、ＰＨＢを抑制することができる。以上
のことから、送信波長と、ファイバ及び光増幅器と他の
偏波モード分散を持つ部品の偏波モード分散の選択によ
って、受信側で劣化が少ない信号を受信できることは明
らかである。That is, if the polarization mode dispersion is evenly distributed in the optical fiber transmission line 13, then td ≧
It becomes 1 / o f , and PHB can be suppressed. From the above, it is clear that a signal with little deterioration can be received on the receiving side by selecting the transmission wavelength and the polarization mode dispersion of the fiber and the optical amplifier and other components having the polarization mode dispersion.
【００３２】図２は上記の効果を利用したこの発明に係
る光伝送装置の第２の実施例の構成を示すものである。
但し、図２において、図１と同一部分には同一符号を付
して示し、ここでは異なる部分について説明する。FIG. 2 shows the configuration of a second embodiment of the optical transmission apparatus according to the present invention which utilizes the above effects.
However, in FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and different parts will be described here.
【００３３】すなわち、この実施例では、光ファイバ伝
送路１３の伝送路中に多数の偏波モード分散素子１３２
１〜１３２ｋを平均に配置して、光伝送路の全偏波モー
ド分散ＰＭＤの値ｔｄを増加させている。偏波モード分
散素子の挿入方法としては、光ファイバ自体の特性を変
えるようにしてもよいが、図６に示すように、複数の複
屈折率結晶２１を利用してもよい。尚、図６において、
２２，２３はレンズ、２４，２５はそれぞれ入力用光フ
ァイバ、出力用光ファイバを示している。That is, in this embodiment, a large number of polarization mode dispersion elements 132 are provided in the transmission line of the optical fiber transmission line 13.
1-132k are arranged on the average to increase the value td of the total polarization mode dispersion PMD of the optical transmission line. As a method of inserting the polarization mode dispersion element, the characteristics of the optical fiber itself may be changed, but as shown in FIG. 6, a plurality of birefringent crystals 21 may be used. In addition, in FIG.
Reference numerals 22 and 23 denote lenses, and 24 and 25 denote input optical fibers and output optical fibers, respectively.
【００３４】このように、この発明の長距離光伝送装置
では、偏波ホールバーニングを抑えて、信号のスペクト
ル広がりによる信号劣化、またはチャネル間のクロスト
ークなしで、長距離に光を伝送することができる。As described above, in the long-distance optical transmission device of the present invention, polarization hole burning is suppressed, and light is transmitted over a long distance without signal deterioration due to signal spectrum spread or crosstalk between channels. You can
【００３５】[0035]
【発明の効果】以上のようにこの発明によれば、簡単な
手法で、偏波スクランブル処理を行わずにＰＨＢを抑制
することのできる光伝送装置を提供することができる。As described above, according to the present invention, it is possible to provide an optical transmission device capable of suppressing PHB by a simple method without performing polarization scrambling processing.
【図１】この発明に係る光伝送装置の第１の実施例の構
成を示すブロック図である。FIG. 1 is a block diagram showing a configuration of a first embodiment of an optical transmission device according to the present invention.
【図２】この発明に係る光伝送装置の第２の実施例の構
成を示すブロック図である。FIG. 2 is a block diagram showing a configuration of a second embodiment of the optical transmission device according to the present invention.
【図３】この発明の動作原理を説明するための図であ
る。FIG. 3 is a diagram for explaining the operating principle of the present invention.
【図４】この発明の動作原理を説明するための図であ
る。FIG. 4 is a diagram for explaining the operating principle of the present invention.
【図５】図４の動作における伝送距離による光信号の平
均パワースペクトルの例を示す図である。5 is a diagram showing an example of an average power spectrum of an optical signal according to a transmission distance in the operation of FIG.
【図６】第２の実施例の偏波モード分散素子の一例を示
す図である。FIG. 6 is a diagram showing an example of a polarization mode dispersion element according to a second embodiment.
１１１〜１１ｎ…光送信器 １２…光結合器 １３…光ファイバ伝送路 １３１１〜１３１ｍ…エルビウムドープ光ファイバ増幅
器（ＥＤＦＡ） １３２１〜１３２ｋ…偏波モード分散素子 １４１〜１４ｎ…光受信器 ２１…複屈折率結晶 ２２，２３…レンズ ２４，２５…光ファイバ111-11n ... Optical transmitter 12 ... Optical coupler 13 ... Optical fiber transmission line 1311-131m ... Erbium-doped optical fiber amplifier (EDFA) 1321-132k ... Polarization mode dispersion element 141-14n ... Optical receiver 21 ... Birefringence Index crystal 22, 23 ... Lens 24, 25 ... Optical fiber
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｈ０４Ｊ 14/02 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI technical display location H04J 14/02
Claims (4)
出する複数の光送信器と、 前記複数の光送信器の出力光信号を共に一本に結合する
光結合器と、 この光結合器で結合された光信号を光ファイバケーブル
により伝送する光ファイバ伝送路と、 この光ファイバ伝送路中に介在され、前記光ファイバケ
ーブルの挿入損失を補償する複数の光増幅器と、 前記光ファイバ伝送路の受信側で個別に各波長の光信号
を受信する複数の光受信器とを具備し、 前記光ファイバ伝送路中の全偏波モード分散が被伝送光
信号の光周波数スペクトルの標準偏差の逆数より大きく
なるようにしたことを特徴とする光伝送装置。1. A plurality of optical transmitters for transmitting linearly polarized optical signals having mutually different wavelengths, an optical coupler for coupling together output optical signals of the plurality of optical transmitters, and the optical coupling. Optical fiber transmission line for transmitting the optical signal coupled by the optical fiber cable with the optical fiber cable, a plurality of optical amplifiers interposed in the optical fiber transmission line for compensating the insertion loss of the optical fiber cable, and the optical fiber transmission And a plurality of optical receivers for individually receiving optical signals of each wavelength on the receiving side of the optical path, wherein the total polarization mode dispersion in the optical fiber transmission path is the standard deviation of the optical frequency spectrum of the transmitted optical signal. An optical transmission device characterized in that it is made larger than the reciprocal.
出する複数の光送信器と、 前記複数の光送信器の出力光信号を共に一本に結合する
光結合器と、 この光結合器で結合された光信号を光ファイバケーブル
により伝送する光ファイバ伝送路と、 この光ファイバ伝送路中に介在され、前記光ファイバケ
ーブルの挿入損失を補償する複数の光増幅器と、 前記光ファイバ伝送路の受信側で個別に各波長の光信号
を受信する複数の光受信器と、 前記光ファイバ伝送路中の全偏波モード分散が被伝送光
信号の光周波数スペクトルの標準偏差の逆数より大きく
なるように、前記光ファイバ伝送路中に分散配置される
複数の偏波モード分散素子とを具備したことを特徴とす
る光伝送装置。2. A plurality of optical transmitters for transmitting linearly polarized optical signals having mutually different wavelengths, an optical coupler for coupling together output optical signals of the plurality of optical transmitters, and the optical coupling. Optical fiber transmission line for transmitting the optical signal coupled by the optical fiber cable with the optical fiber cable, a plurality of optical amplifiers interposed in the optical fiber transmission line for compensating the insertion loss of the optical fiber cable, and the optical fiber transmission A plurality of optical receivers that individually receive optical signals of each wavelength on the receiving side of the optical path, and the total polarization mode dispersion in the optical fiber transmission path is greater than the reciprocal of the standard deviation of the optical frequency spectrum of the transmitted optical signal. As described above, an optical transmission device comprising a plurality of polarization mode dispersion elements dispersedly arranged in the optical fiber transmission line.
出する複数の光送信器と、 前記複数の光送信器の出力光信号を共に一本に結合する
光結合器と、 この光結合器で結合された光信号を光ファイバケーブル
により伝送する光ファイバ伝送路と、 この光ファイバ伝送路中に介在され、前記光ファイバケ
ーブルの挿入損失を補償する複数の光増幅器と、 前記光ファイバ伝送路の受信側で個別に各波長の光信号
を受信する複数の光受信器とを具備し、 前記光結合器で前記複数の光送信器の任意の出力光信号
を対にして互いに偏波方向が直交するように、かつ同一
振幅レベルとなるようにして結合するようにしたことを
特徴とする光伝送装置。3. A plurality of optical transmitters for transmitting linearly polarized optical signals having mutually different wavelengths, an optical coupler for coupling together output optical signals of the plurality of optical transmitters, and an optical coupler. Optical fiber transmission line for transmitting the optical signal coupled by the optical fiber cable with the optical fiber cable, a plurality of optical amplifiers interposed in the optical fiber transmission line for compensating the insertion loss of the optical fiber cable, and the optical fiber transmission A plurality of optical receivers that individually receive optical signals of respective wavelengths on the receiving side of the optical path, and the optical coupler couples arbitrary output optical signals of the plurality of optical transmitters with each other in polarization directions. An optical transmission device characterized in that they are coupled so that they are orthogonal to each other and have the same amplitude level.
に偏波保持ファイバを用いることを特徴とする請求項３
記載の光伝送装置。4. A polarization maintaining fiber is used to connect the plurality of optical transmitters to the coupler.
The optical transmission device described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11600395A JP3566396B2 (en) | 1995-05-15 | 1995-05-15 | Optical transmission equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11600395A JP3566396B2 (en) | 1995-05-15 | 1995-05-15 | Optical transmission equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08316910A true JPH08316910A (en) | 1996-11-29 |
| JP3566396B2 JP3566396B2 (en) | 2004-09-15 |
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ID=14676436
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11600395A Expired - Fee Related JP3566396B2 (en) | 1995-05-15 | 1995-05-15 | Optical transmission equipment |
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| Country | Link |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998037396A1 (en) * | 1997-02-25 | 1998-08-27 | Mci Communications Corporation | A method and system for simulating pmd using incremental delay switching |
| JP2011181927A (en) * | 2010-02-26 | 2011-09-15 | Fujitsu Ltd | System and method for mitigating polarization hole burning |
| JP2012015692A (en) * | 2010-06-30 | 2012-01-19 | Fujitsu Ltd | Optical transmission system |
| JP2012161056A (en) * | 2011-02-03 | 2012-08-23 | Fujitsu Ltd | Optical transmission device and optical transmission system |
-
1995
- 1995-05-15 JP JP11600395A patent/JP3566396B2/en not_active Expired - Fee Related
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998037396A1 (en) * | 1997-02-25 | 1998-08-27 | Mci Communications Corporation | A method and system for simulating pmd using incremental delay switching |
| JP2011181927A (en) * | 2010-02-26 | 2011-09-15 | Fujitsu Ltd | System and method for mitigating polarization hole burning |
| JP2012015692A (en) * | 2010-06-30 | 2012-01-19 | Fujitsu Ltd | Optical transmission system |
| JP2012161056A (en) * | 2011-02-03 | 2012-08-23 | Fujitsu Ltd | Optical transmission device and optical transmission system |
| US8873972B2 (en) | 2011-02-03 | 2014-10-28 | Fujitsu Limited | Optical transmission apparatus and optical transmission system |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3566396B2 (en) | 2004-09-15 |
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