JPH04299622A - Dispersion equalizing optical transmission system and dispersion equalization optical repeater - Google Patents
Dispersion equalizing optical transmission system and dispersion equalization optical repeaterInfo
- Publication number
- JPH04299622A JPH04299622A JP3089858A JP8985891A JPH04299622A JP H04299622 A JPH04299622 A JP H04299622A JP 3089858 A JP3089858 A JP 3089858A JP 8985891 A JP8985891 A JP 8985891A JP H04299622 A JPH04299622 A JP H04299622A
- Authority
- JP
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- Prior art keywords
- optical
- dispersion
- signal
- equalizing
- repeater
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Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 167
- 230000005540 biological transmission Effects 0.000 title claims abstract description 35
- 239000006185 dispersion Substances 0.000 title claims abstract description 34
- 239000013307 optical fiber Substances 0.000 claims abstract description 28
- 230000010355 oscillation Effects 0.000 claims description 7
- 239000004065 semiconductor Substances 0.000 abstract description 16
- 238000001228 spectrum Methods 0.000 abstract description 11
- 230000000694 effects Effects 0.000 abstract description 2
- 230000001902 propagating effect Effects 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 description 11
- 238000010586 diagram Methods 0.000 description 8
- 238000004891 communication Methods 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 230000001427 coherent effect Effects 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000002547 anomalous effect Effects 0.000 description 1
- 230000008033 biological extinction Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
- Optical Communication System (AREA)
Abstract
Description
【０００１】0001
【産業上の利用分野】本発明は、光通信、特に超長距離
光ファイバ伝送に用いられる分散等化光伝送システムお
よび分散等化光中継器に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersion-equalizing optical transmission system and a dispersion-equalizing optical repeater used in optical communications, particularly ultra-long distance optical fiber transmission.
【０００２】0002
【従来の技術】近年、光信号を光のまま増幅する光増幅
器、特に希土類ドープ光ファイバ増幅器の研究開発が活
発に進められている。この光増幅器を用いると光ファイ
バ伝送時に光ファイバによって受けた損失を補償するこ
とができるので、光増幅器を中継器として用い、光信号
を電気信号に変換することなく長距離を伝送しようとす
る試みが各所でなされている。例えば光の周波数あるい
は位相情報を用いるコヒーレント光通信では光増幅器の
多段中継により２．５Ｇｂ／ｓのＣＰＦＳＫ（位相連続
周波数偏移変調）信号の２，２００ｋｍ伝送が実現され
ている（Ｓ．Ｓａｉｔｏｅｔ ａｌ．， ”Ａｎ ｏｖ
ｅｒ ２，２００ｋｍ ｃｏｈｅｒｅｎｔ ｔｒａｎｓ
ｍｉｓｓｉｏｎ ｅｘｐｅｒｉｍｅｎｔ ａｔ ２．５
Ｇｂｉｔ／ｓｕｓｉｎｇ ｅｒｂｉｕｍ−ｄｏｐｅｄ
−ｆｉｂｅｒ ａｍｐｌｉｆｉｅｒｓ”， Ｔｅｃｈｎ
ｉｃａｌ Ｄｉｇｅｓｔ ｏｎ Ｏｐｔｉｃａｌ Ｆｉ
ｂｅｒＣｏｍｍｕｎｉｃａｔｉｏｎ Ｃｏｎｆｅｒｅｎ
ｃｅ １９９０ （ＯＦＣ’９０）， ｐａｐｅｒ Ｐ
Ｄ２ ）。2. Description of the Related Art In recent years, research and development of optical amplifiers for amplifying optical signals as they are, particularly rare earth-doped optical fiber amplifiers, has been actively conducted. Using this optical amplifier can compensate for the loss caused by the optical fiber during optical fiber transmission, so an attempt was made to use the optical amplifier as a repeater to transmit optical signals over long distances without converting them into electrical signals. is being done in various places. For example, in coherent optical communication that uses optical frequency or phase information, transmission of 2.5 Gb/s CPFSK (phase continuous frequency shift keying) signals over 2,200 km has been realized by multi-stage repeating of optical amplifiers (S. Saito et al. ., ”An ov
er 2,200km coherent trans
mission experiment at 2.5
Gbit/sustaining erbium-doped
-fiber amplifiers”, Techn.
ical Digest on Optical Fi
berCommunication Conference
ce 1990 (OFC'90), paper P
D2).
【０００３】0003
【発明が解決しようとする課題】このように光増幅器を
用いて超長距離の光ファイバ伝送を行う場合、光ファイ
バの波長分散が大きい時、あるいは伝送速度が超高速と
なると、分散により波形劣化が起こり、伝送特性に劣化
が生じることが知られている。この劣化は、直接強度変
調を用いる方式の場合特に大きいが、外部変調器を用い
る直接検波方式あるいはコヒーレント光通信方式でも超
高速、超長距離伝送では劣化が生じることが知られてい
る。（Ｎ．Ｔａｋａｃｈｉｏ ｅｔ ａｌ．， ”Ｃｈ
ｒｏｍａｔｉｃ Ｄｉｓｐｅｒｓｉｏｎ Ｅｑｕａｌｉ
ｚａｔｉｏｎｉｎ ａｎ ８ Ｇｂ／ｓ， ２０２ ｋ
ｍ ＣＰＦＳＫ Ｔｒａｎｓｍｉｓｓｉｏｎ Ｅｘｐｅ
ｒｉｍｅｎｔ”， Ｔｅｃｈｎｉｃａｌ Ｄｉｇｅｓｔ
ｏｎ１７ ｔｈ Ｃｏｎｆｅｒｅｎｃｅ ＯＮ Ｉｎ
ｔｅｇｒａｔｅｄ Ｏｐｔｉｃｓ ａｎｄ Ｏｐｔｉｃ
ａｌ Ｆｉｂｅｒ Ｃｏｍｍｕｎｉｃａｔｉｏｎ，Ｐａ
ｐｅｒ ＰＤＡ−１３）。本発明の目的は上記の課題を
解決し、光ファイバの分散の影響を受けないあるいは分
散の影響を容易に補償できる分散等化光伝送システムお
よび分散等化光中継器を提供することにある。[Problem to be Solved by the Invention] When performing ultra-long distance optical fiber transmission using an optical amplifier as described above, when the wavelength dispersion of the optical fiber is large or when the transmission speed becomes extremely high, the waveform deteriorates due to dispersion. It is known that this causes deterioration in transmission characteristics. This deterioration is particularly large in systems that use direct intensity modulation, but it is also known that deterioration occurs in ultra-high-speed, ultra-long-distance transmission even in direct detection systems that use external modulators or coherent optical communication systems. (N. Takachio et al., “Ch.
romatic Dispersion Equali
zationin an 8 Gb/s, 202k
m CPFSK Transmission Expe
Technical Digest
on17 th Conference ON In
tegrated optics and optic
al Fiber Communication, Pa.
per PDA-13). SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a dispersion-equalizing optical transmission system and a dispersion-equalizing optical repeater that are not affected by the dispersion of optical fibers or can easily compensate for the dispersion effects.
【０００４】0004
【課題を解決するための手段】（１）本発明の分散等化
光伝送システムは、送信部に於て、信号を光ＦＳＫ変調
して送信し、光ファイバで伝送した後に光中継器におい
て、前記光ＦＳＫ信号を線形復調系線形に復調し、この
線形復調系から出力される復調信号により光源を再びＦ
ＳＫ変調して送信し、さらに光ファイバで伝送した後、
受信部で信号を復調し、受信する光伝送システムにおい
て、前記光中継器ではマーク信号とスペース信号の光領
域での周波数位置関係が光中継器の前後で反転するよう
にＦＳＫ変調することにより実現される。[Means for Solving the Problems] (1) In the dispersion-equalized optical transmission system of the present invention, a signal is optically FSK modulated and transmitted in a transmitting section, and after being transmitted through an optical fiber, an optical repeater modulates the signal and transmits the signal. The optical FSK signal is linearly demodulated by a linear demodulation system, and the light source is turned back to F by the demodulation signal output from this linear demodulation system.
After transmitting with SK modulation and further transmission through optical fiber,
In an optical transmission system in which a signal is demodulated and received in a receiving section, the optical repeater performs FSK modulation so that the frequency positional relationship in the optical domain of the mark signal and the space signal is reversed before and after the optical repeater. be done.
【０００５】（２）本発明の分散等化光中継器は、上記
（１）記載の分散等化光伝送システムにおける分散等化
光中継器であり、前記線形復調系が光ヘテロダイン受信
器と電気中間周波数領域の線形周波数弁別器とにより構
成される。(2) The dispersion-equalizing optical repeater of the present invention is a dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system described in (1) above, in which the linear demodulation system is connected to an optical heterodyne receiver and an electric It consists of a linear frequency discriminator in the intermediate frequency domain.
【０００６】（３）本発明の分散等化光中継器は、上記
（１）記載の分散等化光伝送システムにおける分散等化
光中継器であり、前記線形復調系が、光ヘテロダイン受
信器と、電気中間周波数領域の周波数弁別器と、この周
波数弁別および光源の非線形性を補償する補償回路によ
り構成される。(3) The dispersion-equalizing optical repeater of the present invention is a dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system described in (1) above, in which the linear demodulation system is an optical heterodyne receiver and an optical heterodyne receiver. , a frequency discriminator in the electrical intermediate frequency region, and a compensation circuit that compensates for this frequency discrimination and the nonlinearity of the light source.
【０００７】（４）本発明の分散等化光中継器は、上記
（２）又は（３）記載の分散等化光中継器において、光
源を変調して送信するマーク信号及びスペース信号の光
周波数を、前記光ヘテロダイン受信器に含まれる局部発
振光源の光周波数すなわち信号光に対する光領域におけ
る周波数の位置関係により設定することを特徴とする。(4) The dispersion-equalizing optical repeater of the present invention is characterized in that, in the dispersion-equalizing optical repeater described in (2) or (3) above, the optical frequency of the mark signal and the space signal to be transmitted by modulating the light source is is set based on the optical frequency of the local oscillation light source included in the optical heterodyne receiver, that is, the positional relationship of the frequency in the optical region with respect to the signal light.
【０００８】（５）本発明の分散等化光中継器は、上記
（１）記載の分散等化光伝送システムにおける分散等化
光中継器であり、前記線形復調系が光周波数弁別器と光
受信器により構成される。(5) The dispersion-equalizing optical repeater of the present invention is a dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system described in (1) above, in which the linear demodulation system includes an optical frequency discriminator and an optical It consists of a receiver.
【０００９】（６）本発明の分散等化光中継器は、上記
（１）記載の分散等化光伝送システムにおける分散等化
光中継器であり、前記線形復調系が光周波数弁別器、光
受信器、並びに前記光周波数弁別器及び光源の非線形性
を補償する補償回路により構成される。(6) The dispersion-equalizing optical repeater of the present invention is a dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system described in (1) above, in which the linear demodulation system includes an optical frequency discriminator, an optical It is comprised of a receiver, and a compensation circuit that compensates for nonlinearity of the optical frequency discriminator and light source.
【００１０】（７）本発明の分散等化光中継器は、上記
（２）（３）（５）又は（６）記載の分散等化光中継器
において、光源を変調して送信するマーク信号及びスペ
ース信号の光周波数を光または電気中間周波数領域の線
形光周波数弁別器における弁別特性の傾きの向きに応じ
て設定することを特徴とする。(7) The dispersion-equalizing optical repeater of the present invention is the dispersion-equalizing optical repeater described in (2), (3), (5) or (6) above, in which a mark signal is transmitted by modulating the light source. and the optical frequency of the space signal is set according to the direction of the slope of the discrimination characteristic in the linear optical frequency discriminator in the optical or electrical intermediate frequency region.
【００１１】（８）本発明の分散等化光中継器は、上記
（２）（３）（５）又は（６）記載の分散等化光中継器
において、光源を変調して送信するマーク信号及びスペ
ース信号の光周波数を前記復調信号に対するベースバン
ド反転増幅器の出力に応じて設定することを特徴とする
。(8) The dispersion-equalizing optical repeater of the present invention is the dispersion-equalizing optical repeater described in (2), (3), (5) or (6) above, in which a mark signal is transmitted by modulating the light source. and the optical frequency of the space signal is set according to the output of the baseband inverting amplifier for the demodulated signal.
【００１２】0012
【作用】光通信システムは少なくとも送信部、光伝送路
、受信部により構成される。ここでは送信部で信号を光
ＦＳＫ変調して送信する場合を考え、ＦＳＫ信号の内、
マーク信号が長波長側、スペース信号が短波長側に存在
する場合を想定する。このＦＳＫ信号が異常分散を持つ
光ファイバ（１．３μｍ零分散ファイバを１．５μｍ帯
で使用した場合に相当）を伝搬した場合には、短波長側
の信号が速く進み、長波長側の信号には遅れが生じる。
これによりマーク、スペース信号間に伝搬時間差が生じ
ることは勿論であるが、マーク、スペースそれぞれの信
号についても変調によりスペクトル拡がりがあるため、
波長分散の影響で波形歪が生じる。このＦＳＫ信号を光
中継器で線形に復調する。すなわち光周波数の情報を線
形に振幅情報に変換するのである。この振幅情報で半導
体レーザを直接変調すると再びＦＳＫ変調された光信号
を得ることができる。ここで半導体レーザはほぼ線形な
ＡＭ−ＦＭ変換器と考えることができるので、光受信す
る前と同じ条件の光信号を得ることができる。ここで半
導体レーザに加える信号をマーク・スペース間で反転さ
せると送出される光スペクトルを反転させることができ
る。すなわちマーク信号を短波長側に、スペース信号を
長波長側に設定することができる。この信号を再び同じ
分散特性を持つ光ファイバを伝搬させると、ＦＳＫ信号
が光ファイバの波長分散により受ける伝搬時間差はこれ
までと逆になるので、送信器−光中継器、光中継器−受
信器間の伝送距離を等しくすると分散の影響をほぼ零に
することができる。[Operation] The optical communication system is composed of at least a transmitter, an optical transmission line, and a receiver. Here, we will consider the case where the signal is optically FSK modulated and transmitted in the transmitter, and among the FSK signals,
Assume that the mark signal exists on the long wavelength side and the space signal exists on the short wavelength side. When this FSK signal propagates through an optical fiber with anomalous dispersion (equivalent to when a 1.3 μm zero dispersion fiber is used in the 1.5 μm band), the signal on the short wavelength side travels faster, and the signal on the long wavelength side There will be a delay. This naturally causes a propagation time difference between the mark and space signals, but since the mark and space signals also have spectrum broadening due to modulation,
Waveform distortion occurs due to wavelength dispersion. This FSK signal is linearly demodulated using an optical repeater. In other words, optical frequency information is linearly converted into amplitude information. If the semiconductor laser is directly modulated with this amplitude information, an FSK-modulated optical signal can be obtained again. Here, since the semiconductor laser can be considered as a substantially linear AM-FM converter, it is possible to obtain an optical signal under the same conditions as before optical reception. Here, by inverting the signal applied to the semiconductor laser between mark and space, the emitted light spectrum can be inverted. That is, the mark signal can be set to the short wavelength side, and the space signal can be set to the long wavelength side. When this signal is propagated again through an optical fiber with the same dispersion characteristics, the propagation time difference that the FSK signal receives due to the wavelength dispersion of the optical fiber will be reversed, so the transmitter - optical repeater, optical repeater - receiver By making the transmission distances between them the same, the influence of dispersion can be reduced to almost zero.
【００１３】[0013]
【実施例】図１は本発明の第１の実施例を示すブロック
図である。本発明の送信部一では信号源２からの信号に
より半導体レーザ３を直接光周波数偏移（ＦＳＫ）を変
調した。このときマーク信号が長波長（低周波）側、ス
ペース信号が短波長（高周波）側になるように設定した
。この変調信号光は第１の光ファイバ５を伝搬した後、
光中継器１０に入射される。ここで半導体レーザ３の発
振波長は１．５５μｍ、変調の速度は１０Ｇｂ／ｓであ
った。なお今回用いた半導体レーザ３のＦＭ変調特性は
注入電流が大きくなるほど光周波数が高くなるいわゆる
ブルーシフトであった。光ファイバ５の伝送距離は２０
０ｋｍ、零分散波長は１．３μｍであり，使用波長での
分散値は１７ｐｓ／ｎｍ／ｋｍであった。DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a first embodiment of the present invention. In the transmitting section 1 of the present invention, the semiconductor laser 3 is directly modulated in optical frequency shift (FSK) by the signal from the signal source 2. At this time, the mark signal was set to be on the long wavelength (low frequency) side, and the space signal was set to be on the short wavelength (high frequency) side. After this modulated signal light propagates through the first optical fiber 5,
The light is input to the optical repeater 10. Here, the oscillation wavelength of the semiconductor laser 3 was 1.55 μm, and the modulation speed was 10 Gb/s. The FM modulation characteristic of the semiconductor laser 3 used this time was a so-called blue shift in which the optical frequency increases as the injection current increases. The transmission distance of optical fiber 5 is 20
0 km, the zero dispersion wavelength was 1.3 μm, and the dispersion value at the wavelength used was 17 ps/nm/km.
【００１４】光中継器１０ではまず受信信号光が第１の
局部発振光源１１からの光と合波された後、光受信器１
２でヘテロダイン検波される。この光ヘテロダイン検波
によって光領域の信号が電気領域の信号に線形に周波数
変換される。本実施例においては電気中間周波信号の中
心周波数は１５ＧＨｚに設定した。この中間周波信号は
電気領域の線形周波数弁別器１３でベースバンド信号に
変換される。なお線形周波数弁別器１３は遅延検波器の
線形領域を利用することで実現した。このベースバンド
信号により第２の半導体レーザ１４を直接変調すること
で第１の光ファイバ５で受けた分散の影響を保ったまま
でＦＳＫ変調された光信号を再送信することができる。
ここで第２の半導体レーザ１４を変調する変調信号の極
性を調整することで、再送信するＦＳＫ信号の光領域に
おける周波数関係（光スペクトル）を反転することがで
きる。このスペクトルが反転した光信号を第２の光ファ
イバ６を伝搬させることで第１の光ファイバ５で受けた
分散の影響をキャンセルすることができる。光ファイバ
６を伝送した信号は受信部２０においては劣化のない状
態で復調することができる。なお本実施例において第２
の光ファイバ６の長さ、特性は第１の光ファイバ５と同
じであった。また受信部２０は第２の局部発振光源２１
と第２の光受信器２２で構成され、光ヘテロダイン検波
を行うことにより信号の復調が実現されている。In the optical repeater 10, first, the received signal light is multiplexed with the light from the first local oscillation light source 11, and then the optical receiver 1
2, heterodyne detection is performed. This optical heterodyne detection linearly converts the frequency of a signal in the optical domain into a signal in the electrical domain. In this example, the center frequency of the electrical intermediate frequency signal was set to 15 GHz. This intermediate frequency signal is converted into a baseband signal by a linear frequency discriminator 13 in the electrical domain. Note that the linear frequency discriminator 13 was realized by using the linear region of a delay detector. By directly modulating the second semiconductor laser 14 with this baseband signal, the FSK modulated optical signal can be retransmitted while maintaining the influence of dispersion received by the first optical fiber 5. By adjusting the polarity of the modulation signal that modulates the second semiconductor laser 14, the frequency relationship (optical spectrum) in the optical domain of the FSK signal to be retransmitted can be reversed. By propagating this spectrum-inverted optical signal through the second optical fiber 6, the influence of dispersion received by the first optical fiber 5 can be canceled. The signal transmitted through the optical fiber 6 can be demodulated in the receiving section 20 without deterioration. Note that in this example, the second
The length and characteristics of the optical fiber 6 were the same as those of the first optical fiber 5. The receiving section 20 also includes a second local oscillation light source 21.
and a second optical receiver 22, and demodulation of the signal is realized by performing optical heterodyne detection.
【００１５】本実施例では光中継器１０において第２の
半導体レーザ１４から送出されるＦＳＫ信号の周波数配
置を受信信号と反転させるために、図２（ａ）に示され
るように局部発振光源１１から出力される局部発振光の
光周波数が信号光に対し高周波数側になるように設定し
た。この結果、図２（ｂ）に示されるように電気中間周
波数領域ではマークとスペースの周波数配置が反転した
ものが得られる。この信号を高周波数ほど高いレベルが
出力される線形周波数弁別器１３で弁別しこれによって
得られた信号で第２の半導体レーザ１４を変調すれば図
２（ｃ）に示されるように光領域のスペクトルを反転さ
せることができる。In this embodiment, in order to invert the frequency arrangement of the FSK signal transmitted from the second semiconductor laser 14 in the optical repeater 10 with that of the received signal, the local oscillation light source 11 is used as shown in FIG. 2(a). The optical frequency of the locally oscillated light outputted from the oscillator was set to be on the higher frequency side with respect to the signal light. As a result, as shown in FIG. 2(b), in the electrical intermediate frequency region, the frequency arrangement of marks and spaces is reversed. If this signal is discriminated by the linear frequency discriminator 13, which outputs a higher level as the frequency increases, and the second semiconductor laser 14 is modulated with the signal obtained by this, the optical domain will be changed as shown in FIG. 2(c). The spectrum can be inverted.
【００１６】本実施例において光中継器で受信された信
号には大きな波形歪がみられ、かなりの符号誤りが見ら
れた。しかし受信部２０での受信信号にはほとんど波形
歪がなく、エラーフリーでの受信も可能であった。In this example, the signal received by the optical repeater had large waveform distortion and a considerable number of code errors. However, the received signal at the receiver 20 had almost no waveform distortion, and error-free reception was also possible.
【００１７】図３は本実施例で用いた光中継器１０の変
形例の構成図である。図１の実施例では線形周波数弁別
器１３として遅延検波器の線形領域を用いていた。この
周波数弁別器は完全に線形ではない。また半導体レーザ
１４のＡＭ−ＦＭ変換特性も完全には線形ではない。そ
こでこの不完全性を補正するために本変形例では補償回
路１５を挿入した。この補償回路１５は中間周波数帯の
増幅器でありその周波数特性が前記の線形性からのずれ
を補正する特性となっている。周波数特性の調整は抵抗
とコンデンサによるネットワークにより行った。なおこ
こでは中間周波数帯で非線形性の補償を行うことを考え
たが、周波数弁別器１３と半導体レーザ１４の間のベー
スバンド領域で等化を行うことも可能である。FIG. 3 is a block diagram of a modification of the optical repeater 10 used in this embodiment. In the embodiment shown in FIG. 1, a linear region of a delay detector is used as the linear frequency discriminator 13. This frequency discriminator is not completely linear. Furthermore, the AM-FM conversion characteristics of the semiconductor laser 14 are not completely linear. Therefore, in order to correct this imperfection, a compensation circuit 15 is inserted in this modification. This compensation circuit 15 is an amplifier in an intermediate frequency band, and its frequency characteristics are such as to correct the deviation from the linearity described above. Frequency characteristics were adjusted using a network of resistors and capacitors. Note that although we considered here to compensate for nonlinearity in the intermediate frequency band, it is also possible to perform equalization in the baseband region between the frequency discriminator 13 and the semiconductor laser 14.
【００１８】図４は本発明の第２の実施例のブロック図
である。本実施例の光中継器１０ではまずマッハツェン
ダー干渉計の線形領域で構成される光周波数弁別器１６
によりまず光信号がＦＭ−ＡＭ変換される。この変換さ
れた光信号を光受信器１２で検出することにより光周波
数の情報が電気領域の振幅情報に変換される。この信号
の極性を調整して第２の半導体レーザ１４を変調するこ
とによって第１の実施例と同様にＦＳＫ信号の光領域で
のスペクトルを反転させることができ、受信部２０では
ほとんど波形歪の無い信号が得られた。なお本実施例の
受信部２０は第２の光周波数弁別器２３と光受信器２２
により構成されており、光直接周波数弁別受信を行う構
成となっている。その他の構成は第１の実施例と同様で
ある。FIG. 4 is a block diagram of a second embodiment of the present invention. In the optical repeater 10 of this embodiment, first, an optical frequency discriminator 16 constituted by a linear region of a Mach-Zehnder interferometer
First, the optical signal is FM-AM converted. By detecting this converted optical signal with the optical receiver 12, optical frequency information is converted into electrical domain amplitude information. By adjusting the polarity of this signal and modulating the second semiconductor laser 14, the spectrum of the FSK signal in the optical region can be inverted as in the first embodiment. I got no signal. Note that the receiving section 20 of this embodiment includes a second optical frequency discriminator 23 and an optical receiver 22.
It is configured to perform optical direct frequency discrimination reception. The other configurations are similar to the first embodiment.
【００１９】本実施例の光周波数弁別器１６は石英導波
路で構成されたマッハツェンダフィルタであり、導波路
上部に付加されたヒータの温度を変えることにより光周
波数弁別特性を変化させることができる。本実施例では
図５に示されるように信号光のうち高い光周波数をもつ
スペース信号がローレベルとなるように光周波数弁別特
性を設定した。この光周波数弁別出力を光検出した信号
で半導体レーザ１４を変調することにより光領域でのス
ペクトルの反転が実現される。本実施例では光中継器１
０、受信部２０ともに光周波数弁別−直接検波方式を用
いたがヘテロダイン検波方式を用いた第１の実施例と同
様にエラーフリー動作を実現することができた。The optical frequency discriminator 16 of this embodiment is a Mach-Zehnder filter composed of a quartz waveguide, and the optical frequency discrimination characteristics can be changed by changing the temperature of a heater added to the top of the waveguide. In this embodiment, as shown in FIG. 5, the optical frequency discrimination characteristic is set so that the space signal having a high optical frequency among the signal lights becomes a low level. Spectrum inversion in the optical domain is realized by modulating the semiconductor laser 14 with a signal obtained by optically detecting this optical frequency discrimination output. In this embodiment, optical repeater 1
Although the optical frequency discrimination/direct detection method was used in both the receiving section 20 and the receiving section 20, error-free operation could be realized as in the first embodiment using the heterodyne detection method.
【００２０】本発明には以上の実施例の他にも様々な変
形例が考えられる。例えば第１の実施例で再送信される
光ＦＳＫ変調波のスペクトルのマーク・スペース信号の
位置関係は電気領域での線形周波数弁別器１３のスロー
プの向きで決定することも可能であるし、ベースバンド
の反転増幅器を利用して極性を決定することもできる。
また第２の実施例でも反転増幅器を光スペクトル反転に
利用することも可能である。第２の実施例では光周波数
弁別器１６の非線形性を補償する補償回路を付加するこ
とも有効である。[0020] In addition to the above-described embodiments, various modifications of the present invention can be considered. For example, in the first embodiment, the positional relationship between the mark and space signals of the spectrum of the optical FSK modulated wave to be retransmitted can be determined by the direction of the slope of the linear frequency discriminator 13 in the electrical domain; A band inverting amplifier can also be used to determine polarity. Also in the second embodiment, it is also possible to use an inverting amplifier for optical spectrum inversion. In the second embodiment, it is also effective to add a compensation circuit to compensate for the nonlinearity of the optical frequency discriminator 16.
【００２１】本発明に用いる電気領域の周波数弁別器１
３としては遅延検波器の他にフォスターシーリー型の検
波器、レシオ検波器、クオドラチャ検波器等の利用が可
能である。また光周波数弁別器としてはマッハツェンダ
干渉計の他にマイケルソン、ファブリペロー等の干渉計
を用いることもできる。本発明では送信部１からの送信
信号がＦＳＫ変調されており、光中継器１０でこの信号
がスペクトルを反転した状態で線形に中継されることが
ポイントである。従って受信部２０ではＦＳＫ信号の復
調が可能な任意の方式を利用することができる。この光
ＦＳＫ信号の復調方式としては光周波数弁別−直接検波
方式、光ヘテロダイン遅滞検波方式、光ヘテロダインデ
ュアルフィルタ検波方式、光ヘテロダインあるいはホモ
ダイン単一フィルタ検波方式等様々なものが考えられる
。またマーク・スペース信号間の周波数偏移量を大きく
とり、両者の強度差も大きくなるようにしておけば、消
光比劣化はあるが近似的に強度変調−直接検波方式を構
成することも可能である。なお本発明は光増幅器の多段
中継システムへの適用が有効である。たとえば光増幅器
を用いた多段中継超長距離伝送システムに於てその中間
点に本発明の分散等化光中継器を配置することにより、
任意の距離の伝送を分散による波形劣化無しに実現する
ことが可能である。Electrical domain frequency discriminator 1 used in the present invention
3, in addition to the delay detector, a Foster-Seeley type detector, a ratio detector, a quadrature detector, etc. can be used. In addition to the Mach-Zehnder interferometer, a Michelson or Fabry-Perot interferometer can also be used as the optical frequency discriminator. The key point of the present invention is that the transmission signal from the transmitter 1 is FSK modulated, and that this signal is linearly relayed by the optical repeater 10 with its spectrum inverted. Therefore, the receiver 20 can use any method capable of demodulating FSK signals. As the demodulation method for this optical FSK signal, various methods can be considered, such as an optical frequency discrimination-direct detection method, an optical heterodyne delayed detection method, an optical heterodyne dual filter detection method, and an optical heterodyne or homodyne single filter detection method. In addition, if the frequency deviation between the mark and space signals is made large, and the difference in intensity between them is also made large, it is possible to approximately configure an intensity modulation-direct detection method, although the extinction ratio will deteriorate. be. Note that the present invention is effectively applied to a multi-stage relay system of optical amplifiers. For example, by placing the dispersion equalizing optical repeater of the present invention at the intermediate point in a multi-stage repeating ultra-long distance transmission system using optical amplifiers,
It is possible to realize transmission over any distance without waveform deterioration due to dispersion.
【００２２】[0022]
【発明の効果】以上のように本発明によれば、光ファイ
バの分散の影響の大きい高速、長距離伝送においても分
散の影響が少なく、高い品質の通信システムを提供する
分散等化光伝送システム及びそのシステムに用いる分散
等化光中継器を得ることができる。As described above, according to the present invention, there is provided a dispersion-equalized optical transmission system that provides a high-quality communication system with less influence of dispersion even in high-speed, long-distance transmission where the influence of dispersion of optical fibers is large. And a dispersion equalization optical repeater for use in that system can be obtained.
【図１】本発明の第１の実施例を示すブロック図。FIG. 1 is a block diagram showing a first embodiment of the present invention.
【図２】図１の実施例における分散等化光中継器の前後
におけるスペクトルの配置を示す図。FIG. 2 is a diagram showing the arrangement of spectra before and after the dispersion equalization optical repeater in the embodiment of FIG. 1;
【図３】第１の実施例の分散等化光中継器の変形例を示
すブロック図。FIG. 3 is a block diagram showing a modification of the dispersion equalization optical repeater of the first embodiment.
【図４】本発明の第２の実施例を示すブロック図。FIG. 4 is a block diagram showing a second embodiment of the present invention.
【図５】光周波数弁別器の弁別特性を示す特性図。FIG. 5 is a characteristic diagram showing the discrimination characteristics of an optical frequency discriminator.
１ 送信部 １０ 光中継器 ２０ 受信部 ３，１４ 半導体レーザ ５，６ 光ファイバ １１，２１ 局部発振光源 １２，２２ 光受信器 １３ 周波数弁別器 １６，２３ 光周波数弁別器 1 Transmission section 10 Optical repeater 20 Receiving section 3,14 Semiconductor laser 5,6 Optical fiber 11, 21 Local oscillation light source 12, 22 Optical receiver 13 Frequency discriminator 16, 23 Optical frequency discriminator
Claims (8)
送信し、光ファイバで伝送した後に光中継器において、
前記光ＦＳＫ信号を線形復調系で線形に復調し、この線
形復調系から出力される復調信号により光源を再びＦＳ
Ｋ変調して送信し、さらに光ファイバで伝送した後に受
信部で信号を復調し、受信する光伝送システムにおいて
、前記光中継器ではマーク信号とスペース信号の光領域
での周波数位置関係（光スペクトル）が光中継器の前後
で反転するようにＦＳＫ変調することを特徴とする分散
等化光伝送システム。[Claim 1] A signal is optically FSK modulated in a transmitter, transmitted through an optical fiber, and then transmitted in an optical repeater.
The optical FSK signal is linearly demodulated by a linear demodulation system, and the light source is switched back to FS using the demodulation signal output from the linear demodulation system.
In an optical transmission system in which the signal is K-modulated and transmitted, and then transmitted through an optical fiber, the signal is demodulated and received at the receiving section. ) is reversed before and after an optical repeater.
テムにおける分散等化光中継器であり、前記線形復調系
が光ヘテロダイン受信器と電気中間周波数領域の線形周
波数弁別器とにより構成されることを特徴とする分散等
化光中継器。2. The dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system according to claim 1, wherein the linear demodulation system includes an optical heterodyne receiver and a linear frequency discriminator in an electrical intermediate frequency domain. A dispersion equalizing optical repeater characterized by:
テムにおける分散等化光中継器であり、前期線形復調系
が、光ヘテロダイン受信器と、電気中間周波数領域の周
波数弁別器と、前期周波数弁別器および光源の非線形性
を補償する補償回路とにより構成されることを特徴とす
る分散等化光中継器。3. A dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system according to claim 1, wherein the first linear demodulation system includes an optical heterodyne receiver, a frequency discriminator in an electrical intermediate frequency domain, and a first half of the linear demodulation system. A dispersion equalizing optical repeater comprising a frequency discriminator and a compensation circuit that compensates for nonlinearity of a light source.
継器において、光源を変調して送信するマーク信号及び
スペース信号の光周波数を、前記光ヘテロダイン受信器
に含まれる局部発振光源の光周波数が受信された信号光
の光周波数より高いか又は低いかに応じて設定すること
を特徴とする分散等化光中継器。4. In the dispersion-equalizing optical repeater according to claim 2 or 3, the optical frequencies of the mark signal and the space signal to be transmitted by modulating the light source are set to the optical frequencies of the local oscillation light source included in the optical heterodyne receiver. A dispersion equalizing optical repeater characterized in that the optical frequency is set depending on whether the optical frequency is higher or lower than the optical frequency of the received signal light.
テムにおける分散等化光中継器であり、前記線形復調系
が線形光周波数弁別器と光受信器により構成されること
を特徴とする分散等化光中継器。5. The dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system according to claim 1, wherein the linear demodulation system is composed of a linear optical frequency discriminator and an optical receiver. Dispersion equalization optical repeater.
テムにおける分散等化光中継器であり、前記線形復調系
が光周波数弁別器、光受信器、並びに前記光周波数弁別
器および光源の非線形性を補償する補償回路により構成
されることを特徴とする分散等化光中継器。6. The dispersion-equalizing optical repeater in the dispersion-equalizing optical transmission system according to claim 1, wherein the linear demodulation system includes an optical frequency discriminator, an optical receiver, and the optical frequency discriminator and the light source. A dispersion equalizing optical repeater comprising a compensation circuit that compensates for nonlinearity.
等化光中継器において、光源を変調して送信するマーク
信号及びスペース信号の光周波数を光または電気中間周
波数領域の線形周波数弁別器における弁別特性の傾きの
向きに応じて設定することを特徴とする分散等化光中継
器。7. In the dispersion-equalizing optical repeater according to claim 2, 3, 5, or 6, the optical frequency of the mark signal and the space signal to be transmitted by modulating the light source is set to a linear frequency in an optical or electrical intermediate frequency region. A dispersion-equalizing optical repeater characterized in that the setting is made according to the direction of the slope of the discrimination characteristic in the discriminator.
散等化光中継器において、光源を変調して送信するマー
ク信号及びスペース信号の光周波数を前記復調信号に対
するベースバンド反転増幅器の出力に応じ設定すること
を特徴とする分散等化光中継器。8. The dispersion-equalizing optical repeater according to claim 2, 3, 5, or 6, in which the optical frequencies of the mark signal and space signal modulated by the light source and transmitted are adjusted by a baseband inverting amplifier for the demodulated signal. A dispersion equalization optical repeater characterized in that settings are made according to the output of the dispersion equalization optical repeater.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3089858A JPH04299622A (en) | 1991-03-27 | 1991-03-27 | Dispersion equalizing optical transmission system and dispersion equalization optical repeater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3089858A JPH04299622A (en) | 1991-03-27 | 1991-03-27 | Dispersion equalizing optical transmission system and dispersion equalization optical repeater |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH04299622A true JPH04299622A (en) | 1992-10-22 |
Family
ID=13982487
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3089858A Withdrawn JPH04299622A (en) | 1991-03-27 | 1991-03-27 | Dispersion equalizing optical transmission system and dispersion equalization optical repeater |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH04299622A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5400165A (en) * | 1993-09-10 | 1995-03-21 | At&T Corp. | Optical communication using dispersion-induced FM to AM conversion with nonlinearity-induced stabilization |
| JPH10145304A (en) * | 1996-10-31 | 1998-05-29 | Alcatel Alsthom Co General Electricite | Adaptive device for optical communication network |
| CN110380774A (en) * | 2019-07-05 | 2019-10-25 | 东南大学 | A kind of the UAV Communication multidiameter delay transmission method and system of adaptive distance |
-
1991
- 1991-03-27 JP JP3089858A patent/JPH04299622A/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5400165A (en) * | 1993-09-10 | 1995-03-21 | At&T Corp. | Optical communication using dispersion-induced FM to AM conversion with nonlinearity-induced stabilization |
| JPH10145304A (en) * | 1996-10-31 | 1998-05-29 | Alcatel Alsthom Co General Electricite | Adaptive device for optical communication network |
| CN110380774A (en) * | 2019-07-05 | 2019-10-25 | 东南大学 | A kind of the UAV Communication multidiameter delay transmission method and system of adaptive distance |
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