JPS61114624A - Optical heterodyne receiver - Google Patents
Optical heterodyne receiverInfo
- Publication number
- JPS61114624A JPS61114624A JP59236222A JP23622284A JPS61114624A JP S61114624 A JPS61114624 A JP S61114624A JP 59236222 A JP59236222 A JP 59236222A JP 23622284 A JP23622284 A JP 23622284A JP S61114624 A JPS61114624 A JP S61114624A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- frequency
- low
- filter
- intermediate frequency
- 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
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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
- H04B10/60—Receivers
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- 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】
（座業上の利用分野）
本発明は、光通信システムや光情報処理システム等に用
いられる光ヘテロダイン受信装＆に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of sedentary use) The present invention relates to an optical heterodyne receiver used in optical communication systems, optical information processing systems, and the like.
（１１を米技術とその問題点）
一般に光ヘテロダイン検波を用いる通信方法は、従来の
光直接検波を用いる通信方法に比べ、光受信感度を１０
−１００倍以上に高めることができるという大きな特長
があるため、長距離光通信幹線システム等に有効な通信
方法として期待されている。(11 is US technology and its problems) In general, communication methods that use optical heterodyne detection have an optical reception sensitivity of 10% compared to communication methods that use conventional optical direct detection.
- Since it has the great advantage of being able to increase the speed by more than 100 times, it is expected to be an effective communication method for long-distance optical communication trunk systems.
光ヘテロダイン検波を用いる通信方法のうち周波数変調
を用いる光ヘテロダイン横波方法は、光源として半導体
レーザを用いれば光源の直接周波数変調が可能とな夛、
挿入損失のめる外部光変調器音用いなけルばならない他
の光ヘテロダイン検波方法にくらべ、中継器間隔を長く
できる可能性を持っている。しかし、この光ヘテロダイ
ン検波方法で半導体レーザを光源として用いた場合には
、そのスペクトル拡が勺（ＦＭ雑音）が受信感度を劣化
させる場合があった。特に周波数変調された信号光をヘ
テロダイン検波した後、得られた中間周波信号を周波数
弁別検波する場合には、半導体レーザのＦＭ雑音も同時
に周波数弁別検波され、ベースバンドにおける強度備前
となυベースバンドにおける信号対雑音比（８／Ｎ比）
を劣化させるという問題がめった（斉藤他、「コヒーレ
ント光ファイバ伝送変復調技術」研究実用化報告、第３
１巻、第１２号、Ｐ２１７３，１９８２）。Among communication methods that use optical heterodyne detection, the optical heterodyne transverse wave method that uses frequency modulation allows direct frequency modulation of the light source by using a semiconductor laser as the light source.
Compared to other optical heterodyne detection methods that require the use of external optical modulator sound to account for insertion loss, this method has the potential to lengthen the repeater spacing. However, when a semiconductor laser is used as a light source in this optical heterodyne detection method, its spectrum broadening (FM noise) may degrade reception sensitivity. In particular, when the frequency-modulated signal light is heterodyne-detected and the resulting intermediate frequency signal is frequency-discriminatively detected, the FM noise of the semiconductor laser is also frequency-discriminatively detected at the same time, and the intensity at the baseband becomes υbaseband. Signal-to-noise ratio (8/N ratio) at
(Saito et al., Research and Practical Application Report on Coherent Optical Fiber Transmission Modulation and Demodulation Technology, Vol. 3)
Volume 1, No. 12, P2173, 1982).
（発明の目的）
本発明の目的は、スペクトル拡が夛を持つ半導体レーザ
を用いた場合でも、周波数変調された信号の復調時にお
ける受信感度劣化が小さい光ヘテロダイン受信装置Ｍ［
を提供することにある。(Objective of the Invention) An object of the present invention is to provide an optical heterodyne receiver M[
Our goal is to provide the following.
（発明の構成）
本発明の光ヘテロダイン受信装置は、周波数変調された
信号光と局部発振光を合波する光合波部と、この光合波
部によって得られる合波光を受光して中間周波信号を得
る受光部と、この中間周波信号から復調信号を得る信号
゛復調部を含む光ヘテロダイン受信装置において、信号
復調部にベースバンドにおける低周波雑音を遮断するた
めのバイパスフィルタを含むことによシ構成される。(Structure of the Invention) The optical heterodyne receiver of the present invention includes an optical multiplexer that multiplexes frequency-modulated signal light and local oscillation light, and receives the multiplexed light obtained by the optical multiplexer to generate an intermediate frequency signal. In an optical heterodyne receiving device, the optical heterodyne receiving device includes a signal demodulation section that obtains a demodulated signal from the intermediate frequency signal, and a signal demodulation section that obtains a demodulated signal from this intermediate frequency signal. be done.
（発明の原理）
半導体レーザは、その発振時に位相ゆらぎをともなって
お夛これがスペクトル拡が少を生じさせている。これは
ＦＭ雑音とも呼ばれている。この半導体レーザのＦＭ％
音を周波数弁別検波してＦＭ−ＡＭｆ換を行ないＦＭ雑
音のスペクトルを求めると、第２図に示されるよりな１
／ｆＨ音特性が得られる。この図から位相ゆらぎには、
比較的ゆっくシした変動成分が多いということがわかる
（菊池他「ＧａＡｌＡｓレーザのスペクトル純度の測定
」電子通信学会技術研究報告、０ＱＥ８３−２３．１９
８３）。(Principle of the Invention) Semiconductor lasers exhibit phase fluctuations during oscillation, which causes a decrease in spectrum broadening. This is also called FM noise. FM% of this semiconductor laser
When the spectrum of FM noise is obtained by frequency-discriminative detection of the sound and FM-AMf conversion, the result is 1 as shown in Figure 2.
/fH sound characteristics are obtained. From this figure, the phase fluctuation is
It can be seen that there are many relatively slow fluctuation components (Kikuchi et al., "Measurement of spectral purity of GaAlAs laser" IEICE technical research report, 0QE83-23.19
83).
そこで半導体レーザを周波数賀詞して得られた信号光を
別の半導体レーザを用いて光ヘテロダイン検波する場合
を考える。検波して得られる中間周波成分は、周波数変
調信号と送信光用および局部発振光用の半導体レーザの
位相ゆらぎが加え合わさったものでるる。例えばこの中
間周波成分を周波数弁別検波した場合には、１号がベー
スバンド信号に変換されるとともに、半導体レーザの位
相ゆらぎがベースバンド雑音となってあられれる。Therefore, let us consider a case where a signal light obtained by increasing the frequency of a semiconductor laser is optically heterodyne detected using another semiconductor laser. The intermediate frequency component obtained by detection is a combination of the frequency modulation signal and the phase fluctuations of the semiconductor lasers for transmission light and local oscillation light. For example, when this intermediate frequency component is frequency-discriminatively detected, No. 1 is converted into a baseband signal, and the phase fluctuation of the semiconductor laser becomes baseband noise.
この時の雑音は前記のように１／ｆ特性をもっている。The noise at this time has a 1/f characteristic as described above.
このため信号速度に対応した低域フィルタを用いて信号
を復調した場合には、１／／雑音の上表な成分はフィル
タ内に含まれる。従って１／／１１音が受領回路で発生
する熱雑音を上まわる場合には、この１／／雑音で受信
感度が決定されることを本発明者は見出した（この１／
ｆ雑音で決まる８７Ｎは信号光パワーに依存しないので
符号１１１４夛率にフロアを生じる）。本発明では、半
導体レーザの位相ゆらぎによる雑音は低周波成分が大き
いことに着目し、低域遮断フィルタで低周波雑音をカッ
トするものである。このときこの低域遮断によυ、復調
信号に波形歪みが生じ、これによる感度劣化が生じる場
合があるが、低周波雑音の低減による８７Ｎの改善が、
波形歪みによる劣化よシ大きけれは、受信装置全体での
感度は改善されることになる。特に１／／雑音の影響お
よび波形歪みの影響を評価することによ）最適な低域遮
断周波数を求め、これに合うフィルタを用いれば受信感
度を最適にすることが可能である。特に低域遮断に強い
ＩＢ２Ｂ符号等を用いれは低域遮断の周波数をかな夛高
くすることができ、大きなＳ／Ｎ改嵜が期待される。Therefore, when a signal is demodulated using a low-pass filter corresponding to the signal speed, the 1// noise component is included in the filter. Therefore, the inventor found that if the 1//11 sound exceeds the thermal noise generated in the receiving circuit, the receiving sensitivity is determined by this 1// noise (this 1//11 sound
87N, which is determined by f noise, does not depend on the signal light power, so it creates a floor in the code 1114 frequency). In the present invention, attention is paid to the fact that noise due to phase fluctuation of a semiconductor laser has a large low frequency component, and the low frequency noise is cut by a low cutoff filter. At this time, this low-frequency cutoff causes waveform distortion in the demodulated signal, which may cause deterioration of sensitivity, but the improvement of 87N due to the reduction of low-frequency noise is
If the deterioration due to waveform distortion is greater than that, the sensitivity of the entire receiving device will be improved. In particular, by determining the optimal low cutoff frequency (by evaluating the effects of noise and waveform distortion) and using a filter that matches this frequency, it is possible to optimize reception sensitivity. In particular, if an IB2B code that is strong in low-frequency cutoff is used, the low-frequency cutoff frequency can be significantly increased, and a large S/N improvement is expected.
（実施例）
第１図は本発明の一実施例のブロック図であり、第３図
は本発明の一実施例における符号誤シ率特性を示した図
である。(Embodiment) FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 3 is a diagram showing code error rate characteristics in an embodiment of the present invention.
２値周波数変調された信号光１は、局部発振光源２から
出射した局部発振光３と光合波部４で合波される。合波
光５は、受光部６Ｖｃ含まれる光検出器２１でヘテロダ
イン検波され、信号光１と局部発振光３の差周波数をも
つ電気信号２２に変換される。この電気信号２２は中間
周波増幅器２３で増幅された後、中間周波信号７となる
。この中間周波信号７は信号復調部８で復調され４ｉ調
信号９が得られる。ここで、信号値調部８においては、
まず中間周波信号７が周波数弁別検波器２４でベースバ
ンド信号２５に変換され、さらにベースバンド増幅器２
６で増幅される。この後さらに低域遮断フィルタ２７．
ベースバンドフィルタ２８を通って復調信号９が得られ
る。また本実施例においては、中間周波１８号７の周波
数を安定化するための、制御系を用いている。この制御
系ではまず２値周波数変調に対応した２つのキャリア周
波数をもつ中間周波信号７の一部を分離し、低域フィル
タ１０で、低周波側の成分のみを取り出す。ここで得ら
れた低周波側の中間周波数信号の周波数変動を周波数変
動検出器１１で検出し、その慣出侶号１２を駆動回路１
３を介して局部発振光源２の注入電流に帰還して中間周
波数の安定化を行なっている。Signal light 1 subjected to binary frequency modulation is multiplexed with local oscillation light 3 emitted from local oscillation light source 2 by optical multiplexer 4 . The combined light 5 is heterodyne detected by a photodetector 21 included in the light receiving section 6Vc, and converted into an electric signal 22 having a difference frequency between the signal light 1 and the local oscillation light 3. This electrical signal 22 is amplified by an intermediate frequency amplifier 23 and then becomes an intermediate frequency signal 7. This intermediate frequency signal 7 is demodulated by a signal demodulating section 8 to obtain a 4i modulated signal 9. Here, in the signal value adjustment section 8,
First, the intermediate frequency signal 7 is converted into a baseband signal 25 by the frequency discriminator detector 24, and then the baseband amplifier 2
It is amplified by 6. After this, further low-pass filter 27.
A demodulated signal 9 is obtained through the baseband filter 28. Further, in this embodiment, a control system is used to stabilize the frequency of intermediate frequency No. 18 7. In this control system, first, a part of the intermediate frequency signal 7 having two carrier frequencies corresponding to binary frequency modulation is separated, and a low-pass filter 10 extracts only the low frequency side components. A frequency fluctuation detector 11 detects the frequency fluctuation of the intermediate frequency signal on the low frequency side obtained here, and the frequency fluctuation detector 11 detects the frequency fluctuation of the intermediate frequency signal on the low frequency side.
3 to the injected current of the local oscillation light source 2 to stabilize the intermediate frequency.
この実施例において欠、信号光１は波長が１．３μｍで
あＪ）１００Ｍｂ／ｓのマンチェスタ符号（ＩＢ２Ｂ符
号の一種）で変調されている。局部発振光源２としては
波長１．３μｍの分布帰還量の半導体レーザを用い、光
合波部４には単一モードファイバカップラを、光検出器
２１にはＧｅ−ＡＰＤを用いた。また周波数変動検出器
１１は周波数弁別器とループフィルタで構成されている
。In this embodiment, the signal light 1 has a wavelength of 1.3 μm and is modulated with a 100 Mb/s Manchester code (a type of IB2B code). As the local oscillation light source 2, a semiconductor laser with a distributed feedback amount of 1.3 μm in wavelength was used, a single mode fiber coupler was used as the optical multiplexer 4, and a Ge-APD was used as the photodetector 21. Further, the frequency fluctuation detector 11 is composed of a frequency discriminator and a loop filter.
本実施例では信号が低域遮断に強いマンチェスタ符号で
構成されているので、低域遮断フィルタ２７の遮断周波
数は５ＭＨｚに設定した。またベースバンドフィルタ２
８の帯域は１５０ＭＨ１とした。In this embodiment, since the signal is composed of a Manchester code that is strong against low frequency cutoff, the cutoff frequency of the low frequency cutoff filter 27 is set to 5 MHz. Also baseband filter 2
The band of 8 was set to 150MH1.
この実施例で低域遮断フィルタ２７で生じる波形歪みに
よる受信感度劣化は約１５ ｄＢであった。In this example, the reception sensitivity degradation due to waveform distortion caused by the low-cut filter 27 was approximately 15 dB.
これに対しベースバンドにおける８／Ｎは約１０ｄＢ６
ｃ香されている。このため第３図に示すように低域遮断
フィルタ２７１−用いない場合には、半導体レーザのＦ
Ｍ雑音で決まる８／Ｎのため符号誤シ率１０″以下を実
現することはでさなかりたが、低域遮断フィルタ１０を
用いることにより、符号誤シ率ＩＱ−１１以下を実現す
ることができ、そのときの雑音は受光部６で発生する熱
雑音が王であった。On the other hand, 8/N at baseband is approximately 10 dB6
It is scented. Therefore, as shown in FIG. 3, when the low-pass filter 271 is not used, the
Although it was not possible to achieve a code error rate of less than 10'' due to the 8/N determined by M noise, by using the low-pass filter 10, it was possible to achieve a code error rate of IQ-11 or less. The main noise at that time was thermal noise generated in the light receiving section 6.
不発明では以上の実施例のほかに様々な変形が可能であ
る。たとえば、信号光１がマンチェスタ符号以外０？′
Ｆ号で変調されて７゛ても・その符号に
、合わせて低域遮断フィルタ２７の遮断周波数を決定す
るようにすれば、各棟のディジタル符号やアナログ信号
の場合も本発明の受信装置を用いることができる。また
、低域遮断フィルタ２７の特性を半導体レーザのＦＭ雑
音の周波数特性の逆特性にするようにして８／Ｎの改善
をはかることもできる。また、信号光のレベルにろじて
低域遮断フィルタ２７０遮断周波数を変え、各信号レベ
ルでＳ／Ｎｔ−最適にするようにすることも可能である
。Various modifications are possible in addition to the above-described embodiments. For example, is signal light 1 0 other than Manchester code? ′
Even if it is modulated by the F code, the code will be 7゛.
If the cut-off frequency of the low-pass filter 27 is determined at the same time, the receiving apparatus of the present invention can also be used for digital codes and analog signals of each building. Furthermore, it is also possible to improve 8/N by making the characteristics of the low-pass filter 27 inverse to the frequency characteristics of the FM noise of the semiconductor laser. It is also possible to change the cutoff frequency of the low cutoff filter 270 according to the level of the signal light so that the S/Nt is optimized at each signal level.
さらに中間周波信号７のベースバンド信号２５への変換
は周波数弁別器波器２４以外でも、フィルタと包路線検
波器の組合せ等で実現することもできる。Furthermore, the conversion of the intermediate frequency signal 7 to the baseband signal 25 can be realized by a combination of a filter and an envelope detector, etc., other than the frequency discriminator waver 24.
（発明の効果）
以上のように本発明によれば、ＦＭＩ音が比較的大きな
半導体レーザを用いた場合にも、周波数変調信号の復調
時に半導体レーザのＦＭ雑音の影響の小さい光ヘテロダ
イン受信装置を得ることができる。(Effects of the Invention) As described above, according to the present invention, even when a semiconductor laser with a relatively large FMI sound is used, an optical heterodyne receiving device is provided in which the influence of FM noise of the semiconductor laser is small during demodulation of a frequency modulated signal. Obtainable.
第１図は本発明の一実施例のブロック図、第２図は半導
体レーザのＦＭ雑音のスペクトルを示し光層、第３図は
本発明の一実施例における符号誤多重特性を示した図で
ある。
１・・・・・・信号光、２・・・・・・局部発振光源、
４・・・・・・光合波部、６・・・・・・受光部、８・
・−・・・信号復調部、１゜・・・・・・低域フィルタ
、１１・・・・・・周波数変動検出器、１３・・・・・
・駆動回路、２１・・団・光検出器、２３・旧・・中間
周波増幅器、２４・・・・・・周波数弁別検波器、
２６・・・・・・ベースバンド増幅器、２７・・
・・・・低域遮断フィルタ、２８・・・・・・ベースバ
ンドフィルタ。
ｌ＋−１
代理人 弁理士 内 原 門：ｊ、、、、）＼【
−１−Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a diagram showing the FM noise spectrum of a semiconductor laser in the optical layer, and Fig. 3 is a diagram showing code error multiplexing characteristics in an embodiment of the invention. be. 1... Signal light, 2... Local oscillation light source,
4... Optical multiplexing section, 6... Light receiving section, 8...
...Signal demodulation section, 1°...Low pass filter, 11...Frequency fluctuation detector, 13...
・Drive circuit, 21. Group photodetector, 23. Old intermediate frequency amplifier, 24. Frequency discrimination detector,
26...Baseband amplifier, 27...
...Low cutoff filter, 28...Baseband filter. l+-1 Agent Patent Attorney Uchihara Mon:j,,,,)\[
-1-
Claims (1)
部と、この光合波部によって得られる合波光を受光して
中間周波信号を得る受光部と、前記中間周波信号から復
調信号を得る信号復調部とを含む光ヘテロダイン受信装
置において、前記信号復調部はベースバンドにおける低
周波雑音を遮断するための低域遮断フィルタを含むこと
を特徴とする光ヘテロダイン受信装置。an optical multiplexer that multiplexes frequency-modulated signal light and local oscillation light; a light receiver that receives the multiplexed light obtained by the optical multiplexer to obtain an intermediate frequency signal; and a demodulated signal from the intermediate frequency signal. 1. An optical heterodyne receiving apparatus comprising a signal demodulating section, wherein the signal demodulating section includes a low cutoff filter for cutting off low frequency noise in a baseband.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59236222A JPS61114624A (en) | 1984-11-09 | 1984-11-09 | Optical heterodyne receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59236222A JPS61114624A (en) | 1984-11-09 | 1984-11-09 | Optical heterodyne receiver |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS61114624A true JPS61114624A (en) | 1986-06-02 |
Family
ID=16997590
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59236222A Pending JPS61114624A (en) | 1984-11-09 | 1984-11-09 | Optical heterodyne receiver |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61114624A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01292873A (en) * | 1988-05-20 | 1989-11-27 | Nec Corp | Laser device oscillation frequency stabilization |
| JP2008520124A (en) * | 2004-11-09 | 2008-06-12 | コリア・アドバンスト・インスティテュート・オブ・サイエンス・アンド・テクノロジイ | Light modulation method and system in fixed wavelength FP-LD by injection of broadband light source using FP-LD injected mutually |
| JP2010268309A (en) * | 2009-05-15 | 2010-11-25 | Nippon Telegr & Teleph Corp <Ntt> | Optical data communication system, communication equipment and communication method |
| US8798478B2 (en) | 1999-12-21 | 2014-08-05 | Korea Advanced Institute Of Science And Technology | Low-cost WDM source with an incoherent light injected fabry-perot laser diode |
-
1984
- 1984-11-09 JP JP59236222A patent/JPS61114624A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01292873A (en) * | 1988-05-20 | 1989-11-27 | Nec Corp | Laser device oscillation frequency stabilization |
| US8798478B2 (en) | 1999-12-21 | 2014-08-05 | Korea Advanced Institute Of Science And Technology | Low-cost WDM source with an incoherent light injected fabry-perot laser diode |
| JP2008520124A (en) * | 2004-11-09 | 2008-06-12 | コリア・アドバンスト・インスティテュート・オブ・サイエンス・アンド・テクノロジイ | Light modulation method and system in fixed wavelength FP-LD by injection of broadband light source using FP-LD injected mutually |
| JP4773454B2 (en) * | 2004-11-09 | 2011-09-14 | コリア・アドバンスト・インスティテュート・オブ・サイエンス・アンド・テクノロジイ | Light modulation method and system in fixed wavelength FP-LD by injection of broadband light source using FP-LD injected mutually |
| US8073334B2 (en) | 2004-11-09 | 2011-12-06 | Korea Advanced Institute Of Science And Technology | Optical modulation method and system in wavelength locked FP-LD by injecting broadband light source using mutually injected FP-LD |
| JP2010268309A (en) * | 2009-05-15 | 2010-11-25 | Nippon Telegr & Teleph Corp <Ntt> | Optical data communication system, communication equipment and communication method |
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