JPH1154823A - Optical frequency chirp compensation circuit - Google Patents
Optical frequency chirp compensation circuitInfo
- Publication number
- JPH1154823A JPH1154823A JP9209062A JP20906297A JPH1154823A JP H1154823 A JPH1154823 A JP H1154823A JP 9209062 A JP9209062 A JP 9209062A JP 20906297 A JP20906297 A JP 20906297A JP H1154823 A JPH1154823 A JP H1154823A
- Authority
- JP
- Japan
- Prior art keywords
- optical
- optical frequency
- frequency chirp
- amplifier
- medium
- 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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- Lasers (AREA)
- Semiconductor Lasers (AREA)
- Optical Communication System (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、光強度変調時に誘
発される光周波数チャープを補償する光周波数チャープ
補償回路に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical frequency chirp compensating circuit for compensating an optical frequency chirp induced during light intensity modulation.
【０００２】[0002]
【従来の技術】従来より、光信号を光強度変調した場
合、光強度を変調する装置等により時間的光周波数変
動、即ち光周波数チャープが誘発されることが知られて
いる。図１はこの時のスペクトルの変化を示すもので、
図中、破線１はレーザ等からの連続的な光信号のスペク
トル、実線２は変調後の光信号のスペクトル、ハッチン
グで示した部分３は光周波数チャープである。2. Description of the Related Art It has been conventionally known that, when an optical signal is modulated in optical intensity, a temporal optical frequency fluctuation, that is, an optical frequency chirp is induced by a device for modulating the optical intensity. FIG. 1 shows the change of the spectrum at this time.
In the figure, a broken line 1 is a spectrum of a continuous optical signal from a laser or the like, a solid line 2 is a spectrum of a modulated optical signal, and a hatched portion 3 is an optical frequency chirp.
【０００３】この変調後の光信号をそのまま光ファイバ
で伝送すると、光周波数チャープがファイバ媒質の分散
の影響を受けて波形劣化を引き起こすため、光周波数チ
ャープを抑圧する必要がある。[0003] If the modulated optical signal is transmitted as it is through an optical fiber, the optical frequency chirp is affected by the dispersion of the fiber medium and causes waveform deterioration, so that it is necessary to suppress the optical frequency chirp.
【０００４】図２は従来の光周波数チャープ補償回路の
一例を示すもので、光周波数チャープを含む変調後の光
信号１１を狭帯域の光フィルタ１２を通過させることに
より、光周波数チャープの帯域をカットし、ほぼ変調前
の光周波数成分のみとなった光信号１３を出力する如く
なっている。FIG. 2 shows an example of a conventional optical frequency chirp compensating circuit. The modulated optical signal 11 including the optical frequency chirp is passed through a narrow-band optical filter 12 to reduce the band of the optical frequency chirp. The optical signal 13 which has been cut and has substantially only the optical frequency component before modulation is output.
【０００５】図３は従来の光周波数チャープ補償回路の
他の例を示すもので、Master Laser２１、アイソレータ
２２及びSlave Laser ２３からなる注入同期型レーザの
Slave Laser ２３に、変調後の光信号２４を光増幅器２
５で増幅しカプラ２６を介して注入することによって、
変調信号をMaster Laser２１から出力されるレーザ光に
載せ換え、光増幅器２７及び光フィルタ２８を介して取
り出すようになしたもので、この時の出力光信号２９の
チャープ量はMaster Laser２１のチャープ量まで抑圧さ
れる。FIG. 3 shows another example of a conventional optical frequency chirp compensating circuit, which is an injection-locked laser comprising a Master Laser 21, an isolator 22 and a Slave Laser 23.
The modulated optical signal 24 is supplied to the Slave Laser 23 by the optical amplifier 2.
By amplifying at 5 and injecting through coupler 26,
The modulation signal is replaced with the laser light output from the Master Laser 21 and is extracted through the optical amplifier 27 and the optical filter 28. At this time, the chirp amount of the output optical signal 29 is up to the chirp amount of the Master Laser 21. Be suppressed.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、前述し
た図２の構成では、同図(b) に示すような微少な周波数
変化を伴う光周波数チャープだけを取り除いた透過光ス
ペクトル１４を得るためには、光フィルタ１２の通過帯
域特性１５として、変調前の光信号のスペクトルにほぼ
対応した、高い波長設定確度及び狭帯域性が要求される
ことから、実際には、非常に実現困難であった。However, in the configuration of FIG. 2 described above, in order to obtain the transmitted light spectrum 14 from which only the optical frequency chirp with a small frequency change as shown in FIG. In practice, the passband characteristic 15 of the optical filter 12 is required to have a high wavelength setting accuracy and a narrow band property substantially corresponding to the spectrum of the optical signal before modulation, and therefore, it is actually very difficult to realize.
【０００７】また、図３の構成では、Laser 等の光部品
を多数必要とし、また、それらを制御する回路が必要に
なるため、複雑かつ大型になるという問題があった。In addition, the configuration shown in FIG. 3 requires a large number of optical components such as a laser, and requires a circuit for controlling the components.
【０００８】本発明の目的は、容易に光周波数チャープ
を抑圧できるとともに、構成が単純で小型化が可能な光
周波数チャープ補償回路を提供することにある。An object of the present invention is to provide an optical frequency chirp compensating circuit that can easily suppress optical frequency chirp, has a simple configuration, and can be reduced in size.
【０００９】[0009]
【課題を解決するための手段】本発明では前記課題を解
決するため、光信号を光強度変調した際に生じる光周波
数チャープを抑圧する光周波数チャープ補償回路におい
て、入力光のオン・オフ時に電子キャリア密度変動が誘
起される媒質と、該媒質への入力光の光強度を制御する
前置光増幅器とを備え、前記媒質への入力光信号のオン
・オフ時に該媒質内で起きる電子キャリア密度変動より
誘起された位相変調により発生する時間的光周波数変調
効果を利用して、光周波数チャープを抑圧することを特
徴とする。According to the present invention, in order to solve the above-mentioned problems, an optical frequency chirp compensating circuit for suppressing an optical frequency chirp generated when an optical signal is subjected to light intensity modulation is provided with an electronic circuit when input light is turned on and off. A medium in which carrier density fluctuation is induced, and a pre-optical amplifier for controlling the light intensity of input light to the medium, wherein an electron carrier density occurring in the medium when the input optical signal to the medium is turned on / off. The optical frequency chirp is suppressed by utilizing the temporal optical frequency modulation effect generated by the phase modulation induced by the fluctuation.
【００１０】本発明によれば、入力光信号は前置光増幅
器で増幅され、信号オン時の媒質への光信号強度が一定
に保たれるようにレベルコントロールされる。この前置
光増幅器を介した光信号が媒質に注入されると、媒質内
では入力光信号により電子キャリア密度の変化が起き、
屈折率が変化する。この屈折率変化に伴って位相変調が
誘発され、位相変調の時間的変化である光周波数変動が
誘起される。この光周波数変動が、入力光信号自体の光
周波数チャープとは逆の方向性を有するようにすること
により光信号のチャープを抑圧する。According to the present invention, the input optical signal is amplified by the pre-amplifier and level-controlled so that the intensity of the optical signal to the medium when the signal is turned on is kept constant. When the optical signal via the pre-amplifier is injected into the medium, a change in the electron carrier density occurs in the medium due to the input optical signal,
The refractive index changes. A phase modulation is induced with the change in the refractive index, and an optical frequency fluctuation, which is a temporal change of the phase modulation, is induced. The optical frequency fluctuation has a direction opposite to the optical frequency chirp of the input optical signal itself, thereby suppressing the chirp of the optical signal.
【００１１】[0011]
【発明の実施の形態】図４は本発明の光周波数チャープ
補償回路の実施の形態の一例を示すもので、図中、３０
は前置光増幅器、４０は半導体光増幅器、５１は入力光
信号、５２は出力光信号である。FIG. 4 shows an embodiment of the optical frequency chirp compensating circuit according to the present invention.
Denotes a pre-optical amplifier, 40 denotes a semiconductor optical amplifier, 51 denotes an input optical signal, and 52 denotes an output optical signal.
【００１２】前置光増幅器３０は、半導体光増幅器４０
内への入力光の信号オン時の光強度を任意の一定レベル
に制御するもので、一例として、図５(a) に示すよう
な、エルビウムドープ光ファイバ増幅器（ＥＤＦＡ）３
１、ポンプ光制御回路３２、光検出器３３及びカプラ３
４からなる光ファイバ増幅器、または図５(b) に示すよ
うな、エルビウムドープ光ファイバ増幅器３１，３５、
光検出器３３、カプラ３４、アッテネータ３６及びアッ
テネータ制御回路３７からなる光ファイバ増幅器を使用
できる。The pre-amplifier 30 includes a semiconductor optical amplifier 40
The erbium-doped optical fiber amplifier (EDFA) 3 as shown in FIG.
1. Pump light control circuit 32, photodetector 33, and coupler 3
4 or an erbium-doped optical fiber amplifier 31, 35, as shown in FIG.
An optical fiber amplifier including a photodetector 33, a coupler 34, an attenuator 36, and an attenuator control circuit 37 can be used.
【００１３】半導体光増幅器４０は、図６に示すよう
に、その半導体活性層４１が入力光のオン・オフ時に電
子キャリア密度変動が誘起される媒質として用いられ
る。As shown in FIG. 6, the semiconductor active amplifier 41 of the semiconductor optical amplifier 40 is used as a medium in which a change in electron carrier density is induced when input light is turned on and off.
【００１４】前記構成において、入力光信号５１は、前
置光増幅器４０で増幅され、出力レベルコントロールが
行われる。このレベルコントロールされた光信号は半導
体光増幅器４０に入力される。半導体光増幅器４０では
媒質（半導体活性層）４１内の電子キャリアと入力光と
の間の誘導放出過程により利得が生じる。入力光信号の
オン・オフ時に、媒質４１内では電子キャリア密度の変
化ΔＮが起こるため、その屈折率が変化する。In the above configuration, the input optical signal 51 is amplified by the pre-optical amplifier 40, and the output level is controlled. The optical signal whose level has been controlled is input to the semiconductor optical amplifier 40. In the semiconductor optical amplifier 40, a gain is generated by a stimulated emission process between the electron carriers in the medium (semiconductor active layer) 41 and the input light. When the input optical signal is turned on and off, a change ΔN in the electron carrier density occurs in the medium 41, so that the refractive index changes.
【００１５】屈折率変化量Δｎは、 Δｎ＝−λαΓＡg ΔＮ／４π と表される。ここで、λは入力波長、αはチャープパラ
メータ、Γは閉じ込め係数、Ａg は利得係数である。The refractive index change Δn is expressed as follows: Δn = −λαΓA g ΔN / 4π Here, λ is an input wavelength, α is a chirp parameter, Γ is a confinement coefficient, and Ag is a gain coefficient.
【００１６】屈折率変化に伴い、位相変調 Δφ＝−２πΔｎＬ／λ が起こり（但し、Ｌは媒質の光伝搬方向における長
さ）、その時間的変化である光周波数変動δω δω＝−（δφ／δｔ）δω が誘起される。この半導体光増幅器４０内での光周波数
変動、特に図６(b) に示すように信号がオンした時に発
生する負側、つまり低周波側光周波数チャープが、入力
光信号自体の高周波側光周波数チャープを抑圧する。With the change in the refractive index, phase modulation Δφ = −2πΔnL / λ occurs (where L is the length of the medium in the light propagation direction), and the optical frequency fluctuation δω δω = − (δφ / δt) δω is induced. The optical frequency fluctuation in the semiconductor optical amplifier 40, particularly, the negative side, that is, the low frequency side optical frequency chirp generated when the signal is turned on as shown in FIG. 6 (b), is the high frequency side optical frequency of the input optical signal itself. Suppress chirp.
【００１７】半導体光増幅器４０では、光周波数変化
量、即ち光周波数チャープ量が、該半導体光増幅器への
入力光強度により容易に変化することから、前置光増幅
器３０で出力レベルの一定制御を行い、半導体光増幅器
４０への信号オン時の入力光強度を一定にしている。ま
た、前置光増幅器３０の出力レベルをコントロールする
ことで、チャープ補償量を任意に設定することも可能で
ある。In the semiconductor optical amplifier 40, the amount of change in the optical frequency, that is, the amount of optical frequency chirp easily changes depending on the intensity of the input light to the semiconductor optical amplifier. By doing so, the input light intensity to the semiconductor optical amplifier 40 when the signal is turned on is kept constant. Further, by controlling the output level of the pre-optical amplifier 30, the amount of chirp compensation can be set arbitrarily.
【００１８】光強度変調された光信号の時間的光周波数
チャープを補償した例を図７に示す。光周波数チャープ
補償回路内で誘起された位相変調に伴う瞬時周波数変化
（周波数チャープ）は、図７(a) に示すような光強度増
加（信号オン）時に周波数が減少し、図７(c) に示すよ
うな負のチャープ特性を有する。入力光信号は、図７
(b) に示すように、これとは逆の周波数変化（正のチャ
ープ）を示すため、図７(d) に示すように、本光周波数
チャープ補償回路によりチャープを抑圧できる。FIG. 7 shows an example of compensating for the temporal optical frequency chirp of an optical signal whose optical intensity has been modulated. The instantaneous frequency change (frequency chirp) caused by the phase modulation induced in the optical frequency chirp compensator decreases as the light intensity increases (signal on) as shown in FIG. Has a negative chirp characteristic as shown in FIG. The input optical signal is shown in FIG.
As shown in FIG. 7B, the opposite frequency change (positive chirp) is shown, so that the chirp can be suppressed by the optical frequency chirp compensating circuit as shown in FIG.
【００１９】なお、前記光周波数チャープ補償回路の半
導体光増幅器４０の後段に、媒質からの自然放出光（Ｓ
Ｅ）及び増幅された自然放出光（ＡＳＥ）を除去する光
フィルタを設けて自然放出光ノイズを除去するようにし
ても良い。The spontaneous emission light (S) from the medium is provided after the semiconductor optical amplifier 40 of the optical frequency chirp compensating circuit.
An optical filter for removing E) and the amplified spontaneous emission light (ASE) may be provided to remove spontaneous emission light noise.
【００２０】[0020]
【発明の効果】以上説明したように、本発明の光周波数
チャープ補償回路によれば、媒質のキャリア密度変化に
よる位相変調効果を利用して補償するので、チャープ量
の光及び電気的制御が容易であり、コンパクトな光周波
数チャープ回路を実現できる。また、媒質に半導体活性
層、つまり半導体光増幅器を用いた場合には利得を得て
動作する等の付加要素も含まれる。As described above, according to the optical frequency chirp compensating circuit of the present invention, compensation is performed using the phase modulation effect due to the change in the carrier density of the medium, so that the optical and electrical control of the chirp amount is easy. Therefore, a compact optical frequency chirp circuit can be realized. Further, when a semiconductor active layer, that is, a semiconductor optical amplifier is used as a medium, additional elements such as operating with gain are included.
【図１】光周波数チャープによるスペクトルの変化の説
明図FIG. 1 is a diagram illustrating a change in spectrum due to optical frequency chirp.
【図２】従来の光周波数チャープ補償回路の一例を示す
図FIG. 2 is a diagram illustrating an example of a conventional optical frequency chirp compensation circuit.
【図３】従来の光周波数チャープ補償回路の他の例を示
す図FIG. 3 is a diagram showing another example of the conventional optical frequency chirp compensating circuit.
【図４】本発明の光周波数チャープ補償回路の実施の形
態の一例を示す図FIG. 4 is a diagram showing an example of an embodiment of an optical frequency chirp compensating circuit of the present invention.
【図５】前置光増幅器の具体的な構成図FIG. 5 is a specific configuration diagram of a pre-optical amplifier.
【図６】半導体光増幅器の構成及びその入力光のオン・
オフ時の時間的光周波数変調効果を示す図FIG. 6 shows the configuration of the semiconductor optical amplifier and the ON / OFF of the input light.
Diagram showing temporal optical frequency modulation effect when off
【図７】光強度変調された光信号の光周波数チャープの
補償のようすの一例を示す図FIG. 7 is a diagram showing an example of how the optical frequency chirp of an optical signal subjected to optical intensity modulation is compensated.
３０…前置光増幅器、４０…半導体光増幅器、４１…半
導体活性層（媒質）、５１…入力光信号、５２…出力光
信号。Reference numeral 30 denotes a pre-optical amplifier, 40 denotes a semiconductor optical amplifier, 41 denotes a semiconductor active layer (medium), 51 denotes an input optical signal, and 52 denotes an output optical signal.
Claims (3)
波数チャープを抑圧する光周波数チャープ補償回路にお
いて、 入力光のオン・オフ時に電子キャリア密度変動が誘起さ
れる媒質と、 該媒質への入力光の光強度を制御する前置光増幅器とを
備え、 前記媒質への入力光信号のオン・オフ時に該媒質内で起
きる電子キャリア密度変動より誘起された位相変調によ
り発生する時間的光周波数変調効果を利用して、光周波
数チャープを抑圧することを特徴とする光周波数チャー
プ補償回路。An optical frequency chirp compensating circuit for suppressing optical frequency chirp generated when an optical signal is subjected to optical intensity modulation, a medium in which a change in electron carrier density is induced when input light is turned on and off, A pre-optical amplifier for controlling the light intensity of the input light, and a temporal optical frequency generated by phase modulation induced by electron carrier density fluctuation occurring in the medium when the input optical signal to the medium is turned on / off. An optical frequency chirp compensating circuit characterized in that optical frequency chirp is suppressed using a modulation effect.
として半導体光増幅器を用いたことを特徴とする請求項
１記載の光周波数チャープ補償回路。2. The optical frequency chirp compensating circuit according to claim 1, wherein a semiconductor optical amplifier is used as a medium in which a change in electron carrier density is induced.
からの自然放出光（ＳＥ）及び増幅された自然放出光
（ＡＳＥ）を除去するための光フィルタを備えたことを
特徴とする請求項１または２記載の光周波数チャープ補
償回路。3. An optical filter for removing spontaneous emission light (SE) and amplified spontaneous emission light (ASE) from a medium in which a change in electron carrier density is induced. Or the optical frequency chirp compensating circuit according to 2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9209062A JPH1154823A (en) | 1997-08-04 | 1997-08-04 | Optical frequency chirp compensation circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9209062A JPH1154823A (en) | 1997-08-04 | 1997-08-04 | Optical frequency chirp compensation circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH1154823A true JPH1154823A (en) | 1999-02-26 |
Family
ID=16566632
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9209062A Pending JPH1154823A (en) | 1997-08-04 | 1997-08-04 | Optical frequency chirp compensation circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH1154823A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013149949A (en) * | 2011-12-21 | 2013-08-01 | Sumitomo Electric Device Innovations Inc | Method for controlling and measuring semiconductor optical amplifier, and semiconductor optical amplifier |
-
1997
- 1997-08-04 JP JP9209062A patent/JPH1154823A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013149949A (en) * | 2011-12-21 | 2013-08-01 | Sumitomo Electric Device Innovations Inc | Method for controlling and measuring semiconductor optical amplifier, and semiconductor optical amplifier |
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