JPS63203026A - Frequency multiplex transmission system in coherent optical communication - Google Patents
Frequency multiplex transmission system in coherent optical communicationInfo
- Publication number
- JPS63203026A JPS63203026A JP62035119A JP3511987A JPS63203026A JP S63203026 A JPS63203026 A JP S63203026A JP 62035119 A JP62035119 A JP 62035119A JP 3511987 A JP3511987 A JP 3511987A JP S63203026 A JPS63203026 A JP S63203026A
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- light
- multiplex transmission
- demultiplexed
- semiconductor laser
- 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.)
- Pending
Links
- 230000005540 biological transmission Effects 0.000 title claims abstract description 37
- 230000003287 optical effect Effects 0.000 title claims abstract description 32
- 230000001427 coherent effect Effects 0.000 title claims abstract description 13
- 238000004891 communication Methods 0.000 title claims description 11
- 230000010355 oscillation Effects 0.000 claims description 19
- 238000000034 method Methods 0.000 claims description 5
- 239000004065 semiconductor Substances 0.000 abstract description 15
- 230000006641 stabilisation Effects 0.000 abstract description 12
- 238000011105 stabilization Methods 0.000 abstract description 12
- 239000013307 optical fiber Substances 0.000 abstract description 7
- 230000000087 stabilizing effect Effects 0.000 abstract description 2
- 230000000638 stimulation Effects 0.000 abstract 2
- 238000010586 diagram Methods 0.000 description 4
- 230000001419 dependent effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
Classifications
-
- 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
- H04B10/50—Transmitters
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Communication System (AREA)
Abstract
Description
【発明の詳細な説明】
〔概 要〕
コヒーレント光通信で用いられる１つの伝送型態である
周波数多重伝送での各キャリア光として多モード発振し
ている半導体レーザ等の出射光を分波した各分波光を用
いる。周波数多重伝送で必要とされるコヒーレント光源
の高精度な周波数安定化が容易となる。[Detailed Description of the Invention] [Summary] Each carrier light in frequency division multiplexing transmission, which is one transmission type used in coherent optical communication, is a demultiplexed light emitted from a semiconductor laser or the like that oscillates in multiple modes. Uses demultiplexed light. This facilitates highly accurate frequency stabilization of a coherent light source, which is required in frequency multiplexed transmission.
本発明はコヒーレント光通信における周波数多重伝送方
式に関し、更に詳しく言えば、光源として多モード発振
しているレーザを用いたコヒーレント光通信における周
波数多重伝送方式に関する。The present invention relates to a frequency division multiplex transmission system in coherent optical communications, and more specifically, to a frequency division multiplex transmission system in coherent optical communications using a multimode oscillating laser as a light source.
コヒーレント光通信には、その１つの伝送方式として光
周波数多重伝送方式がある。この光周波数多重伝送方式
においても、電気通信の場合と同様に、その各伝送チャ
ネルを形成するのにそのチャネル毎のキャリア光を必要
とする。そのキャリア光の周波数が変化すると、チャネ
ル間の漏話となるからその周波数は高度に安定であるこ
とが必要である。One transmission method for coherent optical communication is an optical frequency multiplexing transmission method. In this optical frequency multiplexing transmission system, as in the case of telecommunications, carrier light is required for each channel to form each transmission channel. If the frequency of the carrier light changes, it will cause crosstalk between channels, so the frequency needs to be highly stable.
従来のコヒーレント光通信における周波数多重伝送シス
テム例を第４図に示す。このシステムにおける周波数多
重伝送態様は次の通りである。周波数安定化回路５２に
よって発振周波数が一定に制御される単−縦モード発振
レーザ（Ｄ Ｆ Ｂレーザ）からなる各周波数安定化光
源４０ａ〜４０ｃからの光を光変調器４１ａ〜４１Ｃで
周波数１位相等の変調をかけ、その各被変調出力光を合
波器４２で合波して光ファイバ４３を介して伝送する。FIG. 4 shows an example of a frequency division multiplexing transmission system in conventional coherent optical communication. The frequency multiplex transmission mode in this system is as follows. The light from each frequency stabilized light source 40a to 40c consisting of a single-longitudinal mode oscillation laser (DFB laser) whose oscillation frequency is controlled to be constant by a frequency stabilization circuit 52 is converted into one frequency phase by optical modulators 41a to 41C. The modulated output lights are multiplexed by a multiplexer 42 and transmitted via an optical fiber 43.
受信側では、光ファイバ４３を介して伝送されて来た光
を光カプラ４４で局発半導体レーザ４５からの局発光と
混合し、受光器４６でヘテロダイン検波して中間周波信
号（ＩＦ倍信号を得る。検波されたＩＦ倍信号ＩＦ増幅
器４７．ＩＦフィルタ４８、復調器４９．識別器５０を
介して送信側で送ったベースバンド信号が復号される。On the receiving side, the light transmitted through the optical fiber 43 is mixed with the local light from the local semiconductor laser 45 by the optical coupler 44, and the light receiver 46 performs heterodyne detection to generate an intermediate frequency signal (IF multiplied signal). The baseband signal sent from the transmitting side is decoded via the detected IF multiplied signal IF amplifier 47, IF filter 48, demodulator 49, and discriminator 50.
システムに形成されているチャネル（送信側の各光源周
波数）の選択はチューニング回路５１によって局発半導
体レーザ４５の発振周波数を、ＩＦフィルタ４８に入る
チャネルが所望のチャネルになるように変えることによ
って行なわれる。The channels formed in the system (the frequencies of each light source on the transmitting side) are selected by using the tuning circuit 51 to change the oscillation frequency of the local semiconductor laser 45 so that the channel entering the IF filter 48 becomes the desired channel. It will be done.
上述のようなシステムにおける周波数多重伝送する場合
における送受での周波数領域は、その送信側から受信側
までの光学系では１０”Ｈｚオーダであるのに対して、
受信側の電気系におけるＩＦ倍信号１０９■２オーダで
ある。従って、上述ヘテロゲイン方式で送信側の光源が
高度に安定しているとした場合でも確実にベースバンド
信号の再生を受信側において実現せんとするにはその光
源の精度を１０５のオーダに保たなければならないこと
になる。そして、発振周波数に温度依存性が高い光源、
例えば半導体レーザにおいては、温度１℃の変化で周波
数が１×１０ρ（ＩＯＣ）ｌｌｚはど変わってしまう。In the case of frequency multiplexing transmission in the above-mentioned system, the frequency range for transmission and reception is on the order of 10"Hz for the optical system from the transmitting side to the receiving side.
The IF multiplied signal in the electrical system on the receiving side is on the order of 109×2. Therefore, even if the light source on the transmitting side is highly stable in the heterogain method described above, in order to reliably reproduce the baseband signal on the receiving side, the accuracy of the light source must be maintained on the order of 105. It will happen. and a light source whose oscillation frequency is highly temperature dependent.
For example, in a semiconductor laser, a temperature change of 1° C. causes a frequency change of 1×10ρ(IOC)llz.
しかも、そのような温度−周波数特性の下でなお且つ電
気系の周波数を±１×１０７ （１０Ｍ）Ｈｚの精度に
保つ必要がある。このため、光源の周波数精度は１０８
オーダ程度としなければならなくなる。Moreover, even under such temperature-frequency characteristics, it is necessary to maintain the frequency of the electrical system to an accuracy of ±1×10 7 (10 M) Hz. Therefore, the frequency accuracy of the light source is 108
It will have to be about the order of magnitude.
このような周波数精度を上述システムのような多数の光
源について保つように制御することは技術的に極めて難
しく、これを実現しようとすると、その周波数安定化回
路は非常に大がかりなものとなり、コスト信頼性という
観点から技術的解決が迫られている問題である。It is technically extremely difficult to maintain such frequency accuracy for a large number of light sources like the system described above, and if this were to be achieved, the frequency stabilization circuit would have to be very large, making it difficult to maintain cost and reliability. This is a problem that requires a technological solution from a gender perspective.
これに加えて、周波数多重伝送における各チャネルのた
めの波長間隔をも上述のような周波数制御の下で確保し
なければならないから、各チャネル毎に別個の光源を設
ける場合の周波数安定化は更にその複雑さを増すことは
明らかである。In addition, the wavelength spacing for each channel in frequency multiplexed transmission must be secured under frequency control as described above, so frequency stabilization is even more difficult when a separate light source is provided for each channel. It is clear that this increases the complexity.
本発明は、斯かる問題点に鑑みて創作されたもので、低
コストの下で周波数安定化を容易にすることのできるコ
ヒーレント光通信における周波数多重伝送方式を提供す
ることを目的とする。The present invention was created in view of such problems, and an object of the present invention is to provide a frequency division multiplexing transmission system in coherent optical communication that can facilitate frequency stabilization at low cost.
第１図は本発明の原理ブロック図を示す。この図におい
て、１２は多モード発振１／−ザ、１４は分波器、１６
．・・・１６Ｎは光変調器、１８は合波器、２０は光伝
送路で、レーザ１２の出射光を分波器１４で分波し、そ
の分波光毎に対応光変調器で所要の変調をかけ、各被変
調光信号を合波器１８で合波して光伝送路２０に伝送す
るようにしたのが本発明方式である。FIG. 1 shows a block diagram of the principle of the present invention. In this figure, 12 is a multimode oscillator, 14 is a duplexer, and 16 is a multimode oscillator.
．． . . . 16N is an optical modulator, 18 is a multiplexer, and 20 is an optical transmission line. The light emitted from the laser 12 is demultiplexed by the demultiplexer 14, and each demultiplexed light is modulated as required by the corresponding optical modulator. In the method of the present invention, each modulated optical signal is multiplexed by a multiplexer 18 and transmitted to an optical transmission line 20.
各変調器で変調をかけられる各光信号は多モード発振レ
ーザ１２（例えばＶＳＢレーザ）の出射光を分波器１４
で分波した光信号の各々である（第３図参照）。従って
、レーザ１２の周波数精度を所望の値になるように制御
すれば、周波数多重に用いられる各周波数は同一の周波
数精度にすることができる。これは周波数の安定化を容
易にする。又、多モード発振レーザ１２の各モードは予
め決められた波長間隔となっているから、上述のような
周波数制御において波長間隔制御を考慮する必要がない
ことからもその実現はより容易となる。Each optical signal modulated by each modulator is outputted from a multimode oscillation laser 12 (for example, a VSB laser) and sent to a demultiplexer 14.
(See Figure 3). Therefore, if the frequency accuracy of the laser 12 is controlled to a desired value, each frequency used for frequency multiplexing can be made to have the same frequency accuracy. This facilitates frequency stabilization. Further, since each mode of the multimode oscillation laser 12 has a predetermined wavelength interval, there is no need to consider wavelength interval control in the frequency control as described above, which makes implementation easier.
第２図は本発明の一実施例を示す。この図において、Ｓ
がコヒーレント光通信における周波数多重伝送システム
における送信側を、Ｍがその光ファイバ（第１図の光伝
送路２０相当）と、Ｒが受信側を示している。受信側の
構成は第４図の従来システムと変わるところがないので
、同一構成要素には同一参照番号を付してその説明を省
略する。FIG. 2 shows an embodiment of the invention. In this figure, S
indicates the transmitting side in a frequency division multiplexing transmission system in coherent optical communication, M indicates the optical fiber (corresponding to the optical transmission line 20 in FIG. 1), and R indicates the receiving side. Since the configuration of the receiving side is the same as that of the conventional system shown in FIG. 4, the same reference numerals are given to the same components and the explanation thereof will be omitted.
第２図システムの送信側は多モード発振半導体レーザ１
２Ｓ（第１図の多モード発振レーザ例）、分波器１４、
光変調器１６＋、１６ａ、１６３、合波器１８及び周波
数安定化回路２２から成る。Figure 2: The transmission side of the system is a multimode oscillation semiconductor laser 1
2S (example of multimode oscillation laser in Fig. 1), branching filter 14,
It consists of optical modulators 16+, 16a, 163, a multiplexer 18, and a frequency stabilization circuit 22.
この送信側の構成による周波数多重伝送は次のようにな
る。Frequency multiplex transmission based on this configuration on the transmitting side is as follows.
多モード発振半導体レーザ１２３からの出射光は分波器
１４により分波され、各分波光は対応光変調器において
所要の変調がかけられる。その各被変調光信号は合波器
Ｉ８により合波されて光ファイバＭを介して受信側Ｒに
伝送される。受信側での信号抽出は第４図について説明
した従来システムと同様である。The light emitted from the multimode oscillation semiconductor laser 123 is demultiplexed by the demultiplexer 14, and each demultiplexed light is subjected to required modulation in a corresponding optical modulator. The modulated optical signals are multiplexed by a multiplexer I8 and transmitted to the receiving side R via the optical fiber M. Signal extraction on the receiving side is similar to the conventional system described with reference to FIG.
この周波数多重伝送においては、単一の多モード発振半
導体レーザ１２Ｓからの出射光（第３図参照）を分波し
てその分波光を周波数多重伝送におけるチャネルを形成
するのに用いているから、多モード発振半導体レーザ１
２３の周波数精度を所望の値に周波数安定化回路２２に
より制御すれば、周波数多重伝送における各チャネルキ
ャリア光もすべて同じ周波数精度とされ得るから周波数
安定化が容易になる。また、多モード発振半導体レーザ
１２３の各発振モードはその幾何学的構造で決まる波長
間隔をもっているから、この点からも周波数の安定化の
容易性を高め得る。なお、多モード発振半導体レーザの
各発振モードにおける出力がほぼ同じであることが望ま
しい。これは光フアイバロスが周波数多重伝送に用いら
れる周波数帯域で一様でないことから伝送距離を伸ばす
上で必要になる。In this frequency division multiplex transmission, the light emitted from the single multimode oscillation semiconductor laser 12S (see Figure 3) is demultiplexed and the demultiplexed light is used to form a channel in the frequency division multiplex transmission. Multimode oscillation semiconductor laser 1
If the frequency accuracy of 23 is controlled to a desired value by the frequency stabilizing circuit 22, each channel carrier light in frequency multiplex transmission can all have the same frequency accuracy, which facilitates frequency stabilization. Further, since each oscillation mode of the multimode oscillation semiconductor laser 123 has a wavelength interval determined by its geometric structure, it is possible to improve the ease of frequency stabilization from this point as well. Note that it is desirable that the output in each oscillation mode of the multimode oscillation semiconductor laser be approximately the same. This is necessary in order to extend the transmission distance because optical fiber loss is not uniform in the frequency band used for frequency multiplexing transmission.
なお、上記実施例において、光源として多モード発振半
導体レーザを用いる例を説明したが、多モード発振する
他のレーザでもよい。In the above embodiments, an example in which a multimode oscillation semiconductor laser is used as a light source has been described, but other lasers that oscillate in a multimode may also be used.
以上述べたように本発明によれば、高い周波数安定度を
要するコヒーレント光通信における多重伝送光源の周波
数安定化を容易にする。光源の共用化が図れるからコス
ト的有利性も得られる。As described above, according to the present invention, frequency stabilization of a multiple transmission light source in coherent optical communication that requires high frequency stability is facilitated. Since the light source can be shared, cost advantages can also be obtained.
第１図は本発明の原理ブロック図、
第２図は本発明の一実施例を示す図、
第３ＦｇＪは光源のスペクトル分布線図、第４図は従来
のコヒーレント光通信における周波数多重伝送システム
例を示す図である。
第１図及び第２図において、
１２は多モード発振レーザ（多モード発振半導体レーザ
１２Ｓ）、
１４は分波器、
１６１ ・・・１６Ｎは光変調器、
１８は合波器、
２０は光伝送路（光ファイバＭ）である。Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a diagram showing an embodiment of the present invention, Figure 3FgJ is a spectral distribution diagram of a light source, and Figure 4 is an example of a frequency division multiplexing transmission system in conventional coherent optical communication. FIG. 1 and 2, 12 is a multimode oscillation laser (multimode oscillation semiconductor laser 12S), 14 is a demultiplexer, 161...16N is an optical modulator, 18 is a multiplexer, and 20 is an optical transmission (optical fiber M).
Claims (1)
で分波し、 その分波光毎に対応光変調器１６＿ｉ（ｉ＝１・・・Ｎ
）で所要の変調をかけ、 各被変調光を合波器（１８）で合波して光伝送路（２０
）を介して伝送することを特徴とするコヒーレント光通
信における周波数多重伝送方式。[Claims] A demultiplexer (14) for the output light of the multimode oscillation laser (12)
The corresponding optical modulator 16_i (i=1...N
) to apply the required modulation, and each modulated light is combined by a multiplexer (18) to form an optical transmission line (20
) is a frequency division multiplexing transmission method in coherent optical communications.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62035119A JPS63203026A (en) | 1987-02-18 | 1987-02-18 | Frequency multiplex transmission system in coherent optical communication |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62035119A JPS63203026A (en) | 1987-02-18 | 1987-02-18 | Frequency multiplex transmission system in coherent optical communication |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS63203026A true JPS63203026A (en) | 1988-08-22 |
Family
ID=12433041
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62035119A Pending JPS63203026A (en) | 1987-02-18 | 1987-02-18 | Frequency multiplex transmission system in coherent optical communication |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS63203026A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5144467A (en) * | 1989-07-28 | 1992-09-01 | Hitachi, Ltd. | Optical tuning method and apparatus suitable for selective reception of optical frequency division multiplex signals |
| US5239400A (en) * | 1991-07-10 | 1993-08-24 | The Arizona Board Of Regents | Technique for accurate carrier frequency generation in of DM system |
| US5434937A (en) * | 1993-11-16 | 1995-07-18 | At&T Corp. | Optical filter having integrated transceivers |
-
1987
- 1987-02-18 JP JP62035119A patent/JPS63203026A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5144467A (en) * | 1989-07-28 | 1992-09-01 | Hitachi, Ltd. | Optical tuning method and apparatus suitable for selective reception of optical frequency division multiplex signals |
| US5239400A (en) * | 1991-07-10 | 1993-08-24 | The Arizona Board Of Regents | Technique for accurate carrier frequency generation in of DM system |
| US5434937A (en) * | 1993-11-16 | 1995-07-18 | At&T Corp. | Optical filter having integrated transceivers |
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