JPH04248504A - Optical transmitter - Google Patents
Optical transmitterInfo
- Publication number
- JPH04248504A JPH04248504A JP3035619A JP3561991A JPH04248504A JP H04248504 A JPH04248504 A JP H04248504A JP 3035619 A JP3035619 A JP 3035619A JP 3561991 A JP3561991 A JP 3561991A JP H04248504 A JPH04248504 A JP H04248504A
- Authority
- JP
- Japan
- Prior art keywords
- optical
- dispersion
- dispersion medium
- optical amplifier
- loss
- 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.)
- Granted
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 61
- 239000006185 dispersion Substances 0.000 claims abstract description 35
- 230000005540 biological transmission Effects 0.000 claims abstract description 32
- 230000035945 sensitivity Effects 0.000 abstract description 10
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 230000006866 deterioration Effects 0.000 abstract description 4
- 230000003321 amplification Effects 0.000 abstract description 2
- 238000003199 nucleic acid amplification method Methods 0.000 abstract description 2
- 239000002612 dispersion medium Substances 0.000 description 31
- 239000000835 fiber Substances 0.000 description 13
- 238000010586 diagram Methods 0.000 description 8
- 239000013307 optical fiber Substances 0.000 description 7
- 230000007423 decrease Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000002609 medium Substances 0.000 description 2
- 229910052691 Erbium Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- -1 rare earth ions Chemical class 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Landscapes
- Light Guides In General And Applications Therefor (AREA)
- Lasers (AREA)
- Optical Communication System (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は、高速光伝送システム、
長中継伝送システムにおいて必要とされる光伝送装置に
関する。[Industrial Application Field] The present invention relates to a high-speed optical transmission system,
The present invention relates to an optical transmission device required in a long relay transmission system.
【０００２】0002
【従来の技術】高速・長中継デジタル光伝送システムを
実現する上で、伝送路である光ファイバの分散と伝送さ
れる信号光のスペクトル広がりによる波形歪みが大きな
問題であった。それを解決する方法として、ファイバの
分散を零にするのが最も有効な方法である。しかし、あ
るファイバが与えられたときそのファイバの分散は、あ
る特定の波長（零分散波長）で零となるのみで、零分散
波長の両側で分散の符号が反転し、零分散波長からずれ
る従って大きくなって行く。現実のシステムを考えた場
合、ファイバおよび光源の波長特性のバラツキを考えた
とき、例えファイバの零分散波長を用いたシステムでも
、光源の波長と施設されるファイバの零分散波長は完全
には一致せず有限の分散σを持つことになる。そこで、
図４のように伝送路であるファイバの分散とちょうど反
対の分散（−σ）を持った分散媒質（例えばファイバ）
を接続しトータルの分散を零にすることにより、分散に
よる波形劣化を除去した後に受光素子で電気信号に変換
することができる。2. Description of the Related Art In realizing a high-speed, long-haul digital optical transmission system, waveform distortion caused by dispersion of optical fibers serving as transmission lines and spectrum broadening of transmitted signal light has been a major problem. The most effective way to solve this problem is to make the fiber dispersion zero. However, when a certain fiber is given, the dispersion of that fiber becomes zero only at a certain wavelength (zero dispersion wavelength), and the sign of the dispersion is reversed on both sides of the zero dispersion wavelength, and it deviates from the zero dispersion wavelength. It's getting bigger. When considering actual systems, and considering variations in the wavelength characteristics of fibers and light sources, even in systems that use the zero dispersion wavelength of the fiber, the wavelength of the light source and the zero dispersion wavelength of the installed fiber do not completely match. Therefore, it has a finite variance σ. Therefore,
As shown in Figure 4, a dispersion medium (for example, a fiber) has a dispersion (-σ) that is exactly opposite to the dispersion of the fiber that is the transmission path.
By connecting them to make the total dispersion zero, it is possible to remove waveform deterioration due to dispersion and then convert it into an electrical signal using the light receiving element.
【０００３】0003
【発明が解決しようとする課題】ところで、上記従来技
術においては次のような問題があった。一般に、光信号
の強度を電気信号に変換する直接検波方式は簡便でかつ
特性も優れているため実用装置として広く用いられてい
る。しかし、直接検波方式において復調される電気信号
のＳ／Ｎ比はＯ／Ｅ変換部の雑音特性と入力光信号パワ
ーで決定されるため、分散媒質を付加するとその媒質が
有する損失分だけ受信感度の低下をもたらす。このこと
は送信側についても同様なことが言える。即ち、送信出
力が分散媒質の損失分だけ減少し、送信受信レベル差と
して伝送路に割り振れる許容損失が減少する。つまり、
分散による波形劣化を補償するために送受信レベル差の
減少が同時に生じるため現実的な有効な方法とは言えな
かった。However, the above-mentioned prior art has the following problems. In general, a direct detection method that converts the intensity of an optical signal into an electrical signal is simple and has excellent characteristics, so it is widely used as a practical device. However, since the S/N ratio of the demodulated electrical signal in the direct detection method is determined by the noise characteristics of the O/E converter and the input optical signal power, adding a dispersion medium increases the reception sensitivity by the loss of that medium. resulting in a decrease in The same thing can be said about the sending side. That is, the transmission output is reduced by the loss of the dispersion medium, and the allowable loss allocated to the transmission path as the difference in transmission and reception levels is reduced. In other words,
In order to compensate for waveform deterioration due to dispersion, the difference in transmission and reception levels simultaneously decreases, so this cannot be said to be a realistically effective method.
【０００４】本発明は前記課題を解決するもので、伝送
路の分散を補償する分散媒質を付加しながら、分散媒質
の損失が受信感度の劣化を招かない構成を可能にした光
伝送装置の提供を目的とする。[0004] The present invention solves the above-mentioned problems, and provides an optical transmission device that enables a configuration in which a dispersion medium is added to compensate for the dispersion of the transmission path, but the loss of the dispersion medium does not cause deterioration of reception sensitivity. With the goal.
【０００５】[0005]
【課題を解決するための手段】本発明は、１台又は複数
の光増幅器を有する光受信回路、光送信回路あるいは光
中継器において、光増幅器と光電気変換部あるいは光増
幅器と光増幅器との間に、伝送路の分散特性を補償する
分散性媒質を有することを特徴とする。[Means for Solving the Problems] The present invention provides an optical receiving circuit, an optical transmitting circuit, or an optical repeater having one or more optical amplifiers. It is characterized by having a dispersive medium in between that compensates for the dispersion characteristics of the transmission path.
【０００６】[0006]
【作用】本発明によれば、光増幅器と分散媒質を装置に
適した組み合せにより、伝送装置の性能が分散媒質の損
失により低下することなく、伝送路の分散を補償するこ
とができる。According to the present invention, by combining an optical amplifier and a dispersion medium suitable for the device, it is possible to compensate for the dispersion of the transmission line without degrading the performance of the transmission device due to loss in the dispersion medium.
【０００７】[0007]
【実施例】以下、本発明による第１、第２、第３、第４
実施例を図面に基づき説明する。本発明においては、光
増幅器と分散媒質を装置に適した組み合せにより、伝送
装置の性能が分散媒質の損失により低下することなく、
伝送路の分散を補償することができる。即ち、直接検波
方式では、光電気変換部でＳ／Ｎが決定され、かつベー
スバンド電気信号に変換されてしまうため伝送路の分散
の影響を光電気変換後では等化できない。従って、Ｓ／
Ｎを決定する回路の前に分散媒質を挿入するしかないた
めに、その損失に敏感に送受信レベル差の減少に反映さ
れてしまっていた。かかる不具合を解決すべく本発明の
図５の光増幅器ＯＡとＯ／Ｅ変換部とからなる受信装置
は、初段の光増幅器ＯＡで受信機としてのＳ／Ｎが決定
され更にＯ／Ｅ単独で受信するよりも高感度になる。し
かも、光増幅された後では、光信号のレベルそのものは
、Ｓ／Ｎ敏感でない。そこで、ＯＡの出力レベルがＯ／
Ｅの受信感度より十分高く設定することにより、ＯＡと
ＯＥの間に分散媒質を挿入しても受信感度には影響せず
分散を補償できる構成が可能となる。[Example] Hereinafter, the first, second, third, and fourth embodiments according to the present invention will be described.
Examples will be described based on the drawings. In the present invention, by combining an optical amplifier and a dispersion medium suitable for the device, the performance of the transmission device is not degraded due to loss in the dispersion medium.
It is possible to compensate for dispersion in the transmission path. That is, in the direct detection method, the S/N is determined in the opto-electric converter and converted into a baseband electrical signal, so the influence of dispersion of the transmission path cannot be equalized after opto-electric conversion. Therefore, S/
Since there is no choice but to insert a dispersion medium in front of the circuit that determines N, the loss is sensitively reflected in a decrease in the difference in transmission and reception levels. In order to solve this problem, the receiving device of the present invention, which is composed of the optical amplifier OA and the O/E converter shown in FIG. The sensitivity is higher than when receiving. Furthermore, after optical amplification, the level of the optical signal itself is not sensitive to S/N. Therefore, the output level of OA is O/
By setting the reception sensitivity sufficiently higher than the reception sensitivity of E, it is possible to create a configuration in which dispersion can be compensated for without affecting the reception sensitivity even if a dispersion medium is inserted between OA and OE.
【０００８】第１実施例。図１は、上記原理を用いて光
受信部を構成した場合である。Ｃは同軸ケーブル、Ｏ／
Ｅは光・電気変換回路、Ｄは分散媒質、ＯＡ１およびＯ
Ａ２は光増幅器、Ｆは光ファイバである。ＯＡ２は分散
媒質の損失が大きい場合に必要となる。[0008] First embodiment. FIG. 1 shows a case where an optical receiver is constructed using the above principle. C is coaxial cable, O/
E is a photoelectric conversion circuit, D is a dispersion medium, OA1 and O
A2 is an optical amplifier, and F is an optical fiber. OA2 is necessary when the loss of the dispersion medium is large.
【０００９】第２実施例。図２は、光中継器として光増
幅器を用いた場合の実施例である。２台の光増幅器の間
に、伝送路のファイバの分散に対し予め逆の分散を与え
る分散媒質を挿入することにより伝送路の分散を補償す
る。図２において、Ｆ１及びＦ２は光ファイバ、Ｄは分
散媒質、ＯＡ１及びＯＡ２は光増幅器である。第一段の
光増幅器ＯＡ１により伝送路で減衰した光信号を増幅し
た後、第１実施例と同様の原理・構成で光信号の出力特
性を損なうことなく、伝送路の分散を補償できる。該装
置の場合、到達した光信号を最初に増幅するＯＡ１でＳ
／Ｎが決定されるので、その後段分散媒質はＳ／Ｎ比劣
化を来たすことなく分散を補償することができる。ただ
し、第一段の光増幅器の光出力が十分に高い場合あるい
は分散媒質の損失が無視できる場合、ＯＡ２は省略する
ことができる。Second embodiment. FIG. 2 shows an embodiment in which an optical amplifier is used as an optical repeater. The dispersion of the transmission line is compensated for by inserting a dispersion medium that gives an opposite dispersion to the fiber dispersion of the transmission line between the two optical amplifiers. In FIG. 2, F1 and F2 are optical fibers, D is a dispersion medium, and OA1 and OA2 are optical amplifiers. After the first-stage optical amplifier OA1 amplifies the optical signal attenuated on the transmission line, the dispersion of the transmission line can be compensated for without impairing the output characteristics of the optical signal using the same principle and configuration as in the first embodiment. In the case of this device, S
/N is determined, the subsequent dispersion medium can compensate for dispersion without deteriorating the S/N ratio. However, if the optical output of the first stage optical amplifier is sufficiently high or if the loss of the dispersion medium can be ignored, OA2 can be omitted.
【００１０】第３実施例。図３は、送信部での実施例で
ある。送信部において、伝送路のファイバの分散に対し
予め逆の分散を与え分散媒質とそれによる光損失を補う
光増幅器により構成されている。図３において、Ｃは同
軸ケーブル、Ｅ／Ｏは電気・光変換回路、Ｄは分散媒質
、ＯＡは光増幅器、Ｆは光ファイバである。分散媒質Ｄ
を用いないで直接光増幅器ＯＡに電気光変換部Ｅ／Ｏ出
力を入力する構成において、光増幅器ＯＡとしてＥｒ−
ドープ光ファイバ増幅器を用いた場合、電気光変換部Ｅ
／Ｏの光出力パワーＰ０は光増幅器ＯＡの利得分だけ増
幅されるが、光増幅器ＯＡの３ｄＢ飽和出力以上となる
光増幅器ＯＡの入力パワーＰｉｎより増加させても、光
増幅器ＯＡが出力飽和し光出力パワーはほとんど増加し
ない。図３のように分散媒質Ｄを電気光変換部Ｅ／Ｏと
光増幅器ＯＡの間に挿入することにより、分散媒質Ｄの
損失を光増幅器ＯＡで補償できるだけでなく、更に増幅
できる。とりわけ、飽和が生じているような条件下では
、光増幅器ＯＡの未飽和利得に対し減じた分だけ、分散
媒質Ｄの損失は全く光増幅器ＯＡの出力パワーに影響し
ない。例えば、光増幅器ＯＡの飽和により１０ｄＢ利得
圧縮が生じた場合、分散媒質Ｄの損失が１０ｄＢ以下で
あれば、この送信部光出力パワーは分散媒質Ｄを挿入し
ないものと同等となり、分散媒質Ｄによる損失によって
出力性能が劣化しない。Third embodiment. FIG. 3 shows an example of a transmitter. The transmitting section is composed of a dispersion medium and an optical amplifier that compensates for the optical loss caused by the dispersion medium, which gives an inverse dispersion in advance to the dispersion of the fiber of the transmission line. In FIG. 3, C is a coaxial cable, E/O is an electrical/optical conversion circuit, D is a dispersion medium, OA is an optical amplifier, and F is an optical fiber. Dispersion medium D
In a configuration in which the output of the electro-optic converter E/O is directly input to the optical amplifier OA without using
When using a doped optical fiber amplifier, the electro-optical converter E
The optical output power P0 of /O is amplified by the gain of the optical amplifier OA, but even if it is increased from the input power Pin of the optical amplifier OA, which is 3 dB saturation output or more of the optical amplifier OA, the output of the optical amplifier OA will not be saturated. The optical output power hardly increases. By inserting the dispersion medium D between the electro-optical converter E/O and the optical amplifier OA as shown in FIG. 3, the loss of the dispersion medium D can not only be compensated by the optical amplifier OA, but also can be further amplified. In particular, under conditions where saturation occurs, the loss of the dispersion medium D does not affect the output power of the optical amplifier OA at all by the amount reduced by the unsaturated gain of the optical amplifier OA. For example, when 10 dB gain compression occurs due to saturation of the optical amplifier OA, if the loss of the dispersion medium D is 10 dB or less, the optical output power of this transmitting section will be equivalent to that without inserting the dispersion medium D, and Output performance does not deteriorate due to loss.
【００１１】第４実施例。図４は、具体的に分散媒質と
して光ファイバを用いた場合の実施例である。光増幅器
として希土類イオン（エルビウム）を添加したファイバ
増幅器を用いた例である。伝送路として用いた分散シフ
トファイバ１５０ｋｍ（Ｆ１）での波長分散を光増幅器
（ＯＡ）と光電気変換（Ｏ／Ｅ）の間に挿入した分散媒
質（光ファイバＦ２；ただしＦ１とは波長分散の符号が
反対でその値も大きい）で打ち消す構成である。即ち、
図７・図８に示す如く、実験により分散補償の効果を確
認することができた。Fourth embodiment. FIG. 4 specifically shows an example in which an optical fiber is used as the dispersion medium. This is an example in which a fiber amplifier doped with rare earth ions (erbium) is used as an optical amplifier. The chromatic dispersion in the dispersion shifted fiber 150 km (F1) used as a transmission line is replaced by a dispersion medium (optical fiber F2; however, F1 is the chromatic dispersion (the sign is opposite and the value is also large). That is,
As shown in FIGS. 7 and 8, the effect of dispersion compensation could be confirmed through experiments.
【００１２】0012
【発明の効果】以上説明したように本発明によれば、光
送信部で、あるいは光中継部で、あるいは光受信部で補
償用の分散媒質の損失に特性を損なわれることなく、そ
れぞれ伝送路のファイバの分散を補償することができ、
長距離伝送後にも波形歪みの光信号を得ることができる
。As explained above, according to the present invention, the transmission path can be improved without losing the characteristics due to the loss of the compensation dispersion medium in the optical transmitter, the optical repeater, or the optical receiver. can compensate for fiber dispersion,
Even after long-distance transmission, optical signals with waveform distortion can be obtained.
【図１】本発明の第１実施例の構成を示す図である。FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention.
【図２】本発明の第２実施例の構成を示す図である。FIG. 2 is a diagram showing the configuration of a second embodiment of the present invention.
【図３】本発明の第３実施例の構成を示す図である。FIG. 3 is a diagram showing the configuration of a third embodiment of the present invention.
【図４】従来の構成を示す図である。FIG. 4 is a diagram showing a conventional configuration.
【図５】本発明の光増幅器を用いた受信回路の構成例を
示す図である。FIG. 5 is a diagram showing a configuration example of a receiving circuit using the optical amplifier of the present invention.
【図６】本発明の第４実施例の構成を示す図である。FIG. 6 is a diagram showing the configuration of a fourth embodiment of the present invention.
【図７】本発明の第４実施例の分散媒質なしの時の１５
０Ｋｍ伝送後の波形図である。FIG. 7: 15 when there is no dispersion medium according to the fourth embodiment of the present invention
It is a waveform diagram after 0km transmission.
【図８】本発明の第４実施例の分散媒質ありの時の１５
０Ｋｍ伝送後の波形図である。FIG. 8: 15 with dispersion medium according to the fourth embodiment of the present invention
It is a waveform diagram after 0km transmission.
Claims (1)
信回路、光送信回路あるいは光中継器において、光増幅
器と光電気変換部あるいは光増幅器と光増幅器との間に
、伝送路の分散特性を補償する分散性媒質を有すること
を特徴とする光伝送装置。Claim 1: In an optical receiving circuit, optical transmitting circuit, or optical repeater having one or more optical amplifiers, dispersion characteristics of the transmission line are provided between the optical amplifier and the opto-electrical converter or between the optical amplifiers. An optical transmission device characterized by having a dispersive medium that compensates for.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3035619A JP2904445B2 (en) | 1991-02-04 | 1991-02-04 | Optical transmission equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3035619A JP2904445B2 (en) | 1991-02-04 | 1991-02-04 | Optical transmission equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04248504A true JPH04248504A (en) | 1992-09-04 |
| JP2904445B2 JP2904445B2 (en) | 1999-06-14 |
Family
ID=12446873
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3035619A Expired - Lifetime JP2904445B2 (en) | 1991-02-04 | 1991-02-04 | Optical transmission equipment |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2904445B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6930824B1 (en) | 1993-08-10 | 2005-08-16 | Fujitsu Limited | Optical amplifier which compensates for dispersion of a WDM optical signal |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5037303A (en) * | 1973-06-14 | 1975-04-08 | ||
| JPS6265529A (en) * | 1985-09-17 | 1987-03-24 | Hitachi Cable Ltd | Decentralization compensation method for optical communication system |
-
1991
- 1991-02-04 JP JP3035619A patent/JP2904445B2/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5037303A (en) * | 1973-06-14 | 1975-04-08 | ||
| JPS6265529A (en) * | 1985-09-17 | 1987-03-24 | Hitachi Cable Ltd | Decentralization compensation method for optical communication system |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6930824B1 (en) | 1993-08-10 | 2005-08-16 | Fujitsu Limited | Optical amplifier which compensates for dispersion of a WDM optical signal |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2904445B2 (en) | 1999-06-14 |
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