JP3259862B2 - Optical signal transmitter - Google Patents
Optical signal transmitterInfo
- Publication number
- JP3259862B2 JP3259862B2 JP05125793A JP5125793A JP3259862B2 JP 3259862 B2 JP3259862 B2 JP 3259862B2 JP 05125793 A JP05125793 A JP 05125793A JP 5125793 A JP5125793 A JP 5125793A JP 3259862 B2 JP3259862 B2 JP 3259862B2
- Authority
- JP
- Japan
- Prior art keywords
- signal
- light source
- optical
- band
- intensity
- 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.)
- Expired - Lifetime
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- Semiconductor Lasers (AREA)
- Optical Communication System (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は、外部変調方式で光強度
を変調する光ファイバ伝送システムの光送信部に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission section of an optical fiber transmission system for modulating light intensity by an external modulation method.
【０００２】[0002]
【従来の技術】この種の光送信部の従来の技術は、図３
に示すように、光源０からの一定強度の光を、伝送信号
発生器３からの伝送電気信号１０により、外部変調器２
で強度変調し、その出力光を光ファイバ伝送路４で伝送
するように構成されている。2. Description of the Related Art The prior art of this type of optical transmitter is shown in FIG.
As shown in the figure, the light of constant intensity from the light source 0 is transmitted to the external modulator 2 by the transmission electric signal 10 from the transmission signal generator 3.
, And the output light is transmitted through the optical fiber transmission line 4.
【０００３】[0003]
【発明が解決しようとする課題】光ファイバにおける光
非線形効果はいくつかあるが、そのうち最も生じやすい
ものの一つに、誘導ブリュアン散乱（Ｓtimulated Ｂri
llouin Ｓcatterin ,以下ＳＢＳと称する）があり、光
ファイバへの入力信号光強度があるレベルをこえるとＳ
ＢＳが生じ、このとき入力信号光を大きくしても、入力
信号光強度を大きくした分だけ伝送される光信号強度が
増加せず、入力側に戻ってしまう。また、伝送品質に対
しても、例えば、光アナログ信号伝送においては、雑
音，歪み特性の劣化を生じる。このＳＢＳは、信号光強
度があるしきい値Ｐthよりも大きい値のときに発生す
る。Ｐthの値は、以下の式であらわされる。There are several optical nonlinear effects in an optical fiber, one of which is most likely to occur is stimulated Brillouin scattering.
llouin scatterer (hereinafter referred to as SBS), and when the input signal light intensity to the optical fiber exceeds a certain level, S
A BS occurs. At this time, even if the input signal light is increased, the intensity of the transmitted optical signal does not increase by an amount corresponding to the increase of the input signal light intensity, and returns to the input side. Also, with respect to transmission quality, for example, in optical analog signal transmission, noise and distortion characteristics deteriorate. This SBS occurs when the signal light intensity is larger than a certain threshold value Pth . The value of P th is represented by the following equation.
【０００４】[0004]
【数１】 ここで、ΔｖＬＤは光源の線幅、gsbsはブリュアン利
得、Ａeff はファイバのコアの有効断面積、Δvsbsはブ
リュアン利得帯域、Ｌeff はファイバの実効長で、(Equation 1) Here, ΔvLD is the line width of the light source, gsbs is the Brillouin gain, A eff is the effective area of the fiber core, Δvsbs is the Brillouin gain band, L eff is the effective length of the fiber,
【０００５】[0005]
【数２】 であらわされる。ただし、Ｌはファイバ長、αはファイ
バのロスパラメータで、α＝ [ファイバロス (ｄＢ／ｋ
ｍ）] ／４．３４３である。(Equation 2) It is represented by Here, L is the fiber length, α is the fiber loss parameter, and α = [fiber loss (dB / k
m)] / 4.343.
【０００６】半導体レーザの直接変調による強度変調方
式では、直接変調によるチャーピングのために、ΔｖＬ
Ｄの値は数ＧＨｚになり、このとき実際のシステムにお
いてはＳＢＳは問題とならないが、外部変調による強度
変調方式では、チャーピングがないために、ΔｖＬＤの
値はほぼレーザ光源そのものの値になる。通常のＤＦＢ
レーザの場合にはΔｖＬＤは数十ＭＨｚである。従っ
て、ファイバパラメータＡeff ＝５０μｍ2 と１．５５
μｍ帯におけるパラメータΔvsbs＝２０ＭＨｚ、gsbs＝
５×１０-11 ｍ／Ｗを用いると、Ｌ＝５０ｋｍ、 [ファ
イバロス] ＝０．２ｄＢ／ｋｍ、ΔｖＬＤ＝２０ＭＨｚ
のとき、Ｐth＝２．１５ｍｗとなり、実際のシステムに
おいて十分ＳＢＳが起こりうる。In the intensity modulation method based on direct modulation of a semiconductor laser, ΔvL
The value of D becomes several GHz. At this time, SBS does not matter in an actual system. However, in the intensity modulation method using external modulation, the value of ΔvLD becomes almost the value of the laser light source itself because there is no chirping. . Normal DFB
In the case of a laser, ΔvLD is several tens of MHz. Therefore, the fiber parameters A eff = 50 μm 2 and 1.55
Parameter Δvsbs in μm band = 20 MHz, gsbs =
When 5 × 10 −11 m / W is used, L = 50 km, [fiber loss] = 0.2 dB / km, ΔvLD = 20 MHz
In this case, P th = 2.15 mw, so that SBS can sufficiently occur in an actual system.
【０００７】本発明の目的は、外部変調による強度変調
方式を用いてＳＢＳの影響を受けずに高強度の光信号を
光ファイバに入力してファイバ伝送を行なうことを可能
にする光信号送信器を提供することにある。An object of the present invention is to provide an optical signal transmitter capable of inputting a high-intensity optical signal to an optical fiber and performing fiber transmission without being affected by SBS using an intensity modulation method based on external modulation. Is to provide.
【０００８】[0008]
【課題を解決するための手段】この目的を達成するため
に、本発明による光信号送信器は、光源と、該光源の光
出力強度を伝送すべきアナログ信号で強度変調して得ら
れる出力光をファイバ伝送路に送出する外部変調器とを
備え、前記ファイバ伝送路で前記出力光が誘導ブリュア
ン散乱を起こすしきい値レベルを大きくする帯域とレベ
ルを有する抑圧信号によって前記光源を直接変調するこ
とにより前記出力光の位相又は光周波数を変調する機能
を持つアナログ光伝送用光信号送信器において、前記抑
圧信号の帯域が前記伝送すべきアナログ信号の帯域の帯
域外であることを特徴とする構成を有している。In order to achieve this object, an optical signal transmitter according to the present invention comprises a light source and an output light obtained by modulating the light output intensity of the light source with an analog signal to be transmitted. An external modulator that sends out the light source to a fiber transmission line, and directly modulates the light source with a suppression signal having a band and a level that increases a threshold level at which the output light causes stimulated Brillouin scattering in the fiber transmission line. in the analog optical transmission optical signal transmitter having a function of modulating the phase or optical frequency of the output light by said depression
Band band of the analog signal band of pressure signal should said transmission
It has a configuration characterized by being out of range .
【０００９】[0009]
【作用】半導体レーザ光源ではその注入電流を変調する
ことによりチャーピングが生じる。チャーピングによっ
て、光源のスペクトル幅が見かけ上広くなる。この広が
りがブリュアン利得帯域Δvsbsよりも十分広ければ、式
（１）からわかるようにＳＢＳが発生するしきい値強度
Ｐthを大きくすることができる。光源が多電極レーザで
ある場合には、多電極レーザの１つ、または複数の電極
への電流を変調することにより、光源のスペクトル幅が
見かけ上広くなる。また、多電極レーザであるので、各
電極が位相制御部、強度変調部などにわかれている。し
たがって、その光出力強度を変えることなく、出力光の
位相、あるいは光周波数を変調して光源のスペクトル線
幅を広くすることができる。In a semiconductor laser light source, chirping occurs by modulating the injection current. Chirping increases the apparent spectral width of the light source. If this spread is sufficiently wider than the Brillouin gain band Δvsbs, the threshold intensity P th at which SBS occurs can be increased as can be seen from equation (1). If the light source is a multi-electrode laser, modulating the current to one or more electrodes of the multi-electrode laser increases the apparent width of the light source spectrum. In addition, since it is a multi-electrode laser, each electrode is divided into a phase control unit, an intensity modulation unit, and the like. Therefore, without changing the light output intensity, the phase or optical frequency of the output light can be modulated to widen the spectral line width of the light source.
【００１０】[0010]
【実施例】本発明の実施例１を図１に示す。本実施例で
は光源として半導体レーザを用いる。半導体レーザ光源
１からの光信号強度を、外部変調器２で変調する。この
とき、半導体レーザ光源１を、ＳＢＳ抑圧信号発生器５
からのＳＢＳ抑圧信号１１で直接変調する。ＳＢＳ抑圧
信号１１としては、単一周波数信号，複数の周波数を周
波数多重した信号、ディジタルの疑似ランダムパターン
信号などがある。ただし、半導体レーザ光源１を変調す
ることにより、光源１の光出力が変調されるが、これに
よって伝送電気信号１０の品質が影響を受けないよう
に、ＳＢＳ抑圧信号１１の帯域、強度を選ぶことが必要
である。たとえば、アナログ光伝送においては、ＳＢＳ
抑圧信号１１の周波数スペクトル、あるいはＳＢＳ抑圧
信号１１と伝送すべき信号１０との高次の和あるいは差
の周波数スペクトルが、伝送すべき信号１０の帯域にな
いか、または帯域内にあってもそのレベルが、伝送すべ
き信号１０の品質を劣化させる程度のレベルを持たない
ように、ＳＢＳ抑圧信号１１の帯域，レベルを選ぶ必要
がある。ディジタル光伝送方式においても、同様にして
光源の変調によって、誤り率の劣化がないようにＳＢＳ
抑圧信号１１の帯域，レベルを選ぶ必要がある。FIG. 1 shows a first embodiment of the present invention. In this embodiment, a semiconductor laser is used as a light source. The intensity of the optical signal from the semiconductor laser light source 1 is modulated by the external modulator 2. At this time, the semiconductor laser light source 1 is switched to the SBS suppression signal generator 5.
Directly with the SBS suppression signal 11 from Examples of the SBS suppression signal 11 include a single frequency signal, a signal obtained by frequency-multiplexing a plurality of frequencies, and a digital pseudo random pattern signal. However, by modulating the semiconductor laser light source 1, the light output of the light source 1 is modulated, but the band and intensity of the SBS suppression signal 11 must be selected so that the quality of the transmission electric signal 10 is not affected by this. is necessary. For example, in analog optical transmission, SBS
Even if the frequency spectrum of the suppressed signal 11 or the frequency spectrum of a higher-order sum or difference between the SBS suppressed signal 11 and the signal 10 to be transmitted is not in the band of the signal 10 to be transmitted or is within the band, It is necessary to select the band and level of the SBS suppression signal 11 so that the level does not have a level that degrades the quality of the signal 10 to be transmitted. Similarly, in the digital optical transmission system, the SBS is controlled so that the error rate is not deteriorated by the modulation of the light source.
It is necessary to select the band and level of the suppression signal 11.
【００１１】具体的な例としては、実験において、伝送
電気信号１０として、それぞれがＦＭ映像信号により変
調された５０個のキャリアを０．５〜２．４ＧＨｚの帯
域に周波数多重した信号を用いて４０ｋｍ伝送したと
き、ＳＢＳ抑圧信号１１として１００ＭＢ／ｓの疑似ラ
ンダムパターン信号を用いてＦＳＫ変調をかけても、光
源の変調によって、０．５〜２．４ＧＨｚの帯域におち
てくる周波数スペクトル成分は雑音レベル以下で観測さ
れなかった。従って、ＦＭ映像信号には影響を及ぼすこ
とはない。ＳＢＳ信号抑圧の結果、ＣＮＲは１５．１ｄ
Ｂが２２．８ｄＢに、ＣＳＯ（複合二次歪み Ｃomposi
te Ｓecond Ｏrder dislortion ）のひずみ率は−２
９．５８ｄＢが−５６．２ｄＢに改善された。As a specific example, in an experiment, a signal obtained by frequency-multiplexing 50 carriers, each modulated by an FM video signal, into a band of 0.5 to 2.4 GHz is used as the transmission electric signal 10. When the signal is transmitted for 40 km and subjected to FSK modulation using a pseudo random pattern signal of 100 MB / s as the SBS suppression signal 11, the frequency spectrum component falling in the band of 0.5 to 2.4 GHz due to the modulation of the light source is It was not observed below the noise level. Therefore, there is no effect on the FM video signal. As a result of the SBS signal suppression, the CNR becomes 15.1d.
B is 22.8 dB, and CSO (composite second-order distortion
The distortion rate of te Second Order is -2.
9.58 dB has been improved to -56.2 dB.
【００１２】実施例２を図２に示す。図１において半導
体レーザ光源１が多電極レーザ６におきかわったもので
ある。多電極レーザ６の位相制御用端子を変調すること
により、半導体レーザ光源１を変調する時に比べ、多電
極レーザ６の出力光強度はほとんどかわらないので、Ｓ
ＢＳ抑圧信号１１の帯域，レベルの制限は緩和される。
また、多電極レーザ６の位相制御用端子を変調すること
により多電極レーザ６の出力光強度が変動する場合で
も、同時に光強度変調用端子の電流を変調することによ
り、多電極レーザ６の出力光強度を一定にしながらＦＳ
Ｋ変調することができる。光源としては半導体レーザ以
外にもファイバ伝送帯域内の波長を出射しかつその位相
又は周波数を変調することができる光源であれば任意の
ものを用いることができる。Embodiment 2 is shown in FIG. In FIG. 1, the semiconductor laser light source 1 is replaced with a multi-electrode laser 6. By modulating the phase control terminal of the multi-electrode laser 6, the output light intensity of the multi-electrode laser 6 hardly changes as compared with when the semiconductor laser light source 1 is modulated.
Restrictions on the band and level of the BS suppression signal 11 are relaxed.
Even if the output light intensity of the multi-electrode laser 6 fluctuates by modulating the phase control terminal of the multi-electrode laser 6, the output of the multi-electrode laser 6 is simultaneously modulated by modulating the current of the light intensity modulation terminal. FS while keeping light intensity constant
K modulation can be performed. Any light source other than the semiconductor laser can be used as long as it can emit a wavelength in the fiber transmission band and modulate its phase or frequency.
【００１３】[0013]
【発明の効果】以上詳細に説明したように、本発明によ
り、ＳＢＳの発生を抑えることにより、光ファイバへの
出力光の入力強度を大きくとることができ、ＳＢＳによ
る雑音、歪みの劣化を受けないで、出力光の伝送距離を
大きくすることができる効果がある。As described above in detail, according to the present invention, by suppressing the occurrence of SBS, the input intensity of the output light to the optical fiber can be increased, and noise and distortion due to SBS can be reduced. However, there is an effect that the transmission distance of the output light can be increased.
【図１】本発明の１つの実施例を示すブロック図であ
る。FIG. 1 is a block diagram showing one embodiment of the present invention.
【図２】本発明の他の実施例を示すブロック図である。FIG. 2 is a block diagram showing another embodiment of the present invention.
【図３】従来技術のブロック構成図である。FIG. 3 is a block diagram of a conventional technique.
１ 半導体レーザ光源 ２ 外部変調器 ３ 伝送信号発生器 ４ 光ファイバ伝送路 ５ 半導体レーザ光源用ＳＢＳ抑圧信号発生器 ６ 多電極半導体レーザ光源 １０ 伝送電気信号 １１ 半導体レーザ光源用ＳＢＳ抑圧信号 Reference Signs List 1 semiconductor laser light source 2 external modulator 3 transmission signal generator 4 optical fiber transmission line 5 SBS suppression signal generator for semiconductor laser light source 6 multi-electrode semiconductor laser light source 10 transmission electric signal 11 SBS suppression signal for semiconductor laser light source
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ Ｈ０４Ｂ 10/152 ──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. 7 Identification code FI H04B 10/152
Claims (1)
きアナログ信号で強度変調して得られる出力光をファイ
バ伝送路に送出する外部変調器とを備え、前記ファイバ
伝送路で前記出力光が誘導ブリュアン散乱を起こすしき
い値レベルを大きくする帯域とレベルを有する抑圧信号
によって前記光源を直接変調することにより前記出力光
の位相又は光周波数を変調する機能を持つアナログ光伝
送用光信号送信器において、 前記抑圧信号の帯域が前記伝送すべきアナログ信号の帯
域の帯域外であることを特徴とするアナログ光伝送用光
信号送信器。1. An optical modulator comprising: a light source; and an external modulator for transmitting an output light obtained by intensity-modulating an optical output intensity of the light source with an analog signal to be transmitted to a fiber transmission line. An analog optical signal having a function of modulating the phase or optical frequency of the output light by directly modulating the light source with a suppression signal having a band and a level for increasing a threshold level at which light causes stimulated Brillouin scattering.
In transmission optical signal transmitter, the analog optical transmission optical signal transmitter, characterized in that the band of the suppression signal is a band of the band of the analog signal to be the transmission.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05125793A JP3259862B2 (en) | 1993-02-18 | 1993-02-18 | Optical signal transmitter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP05125793A JP3259862B2 (en) | 1993-02-18 | 1993-02-18 | Optical signal transmitter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06244488A JPH06244488A (en) | 1994-09-02 |
| JP3259862B2 true JP3259862B2 (en) | 2002-02-25 |
Family
ID=12881899
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP05125793A Expired - Lifetime JP3259862B2 (en) | 1993-02-18 | 1993-02-18 | Optical signal transmitter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3259862B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3273911B2 (en) * | 1996-11-15 | 2002-04-15 | 松下電器産業株式会社 | Optical fiber amplifier, semiconductor laser module for excitation and optical signal transmission system |
| US5793782A (en) * | 1996-11-15 | 1998-08-11 | Ericsson, Inc. | Linearized external modulator transmitter with improved dynamic range |
| US6657729B2 (en) * | 2000-03-27 | 2003-12-02 | Honeywell International Inc. | Dithering system and method for a laser diode light source for an optical gyroscope |
| US8885675B2 (en) | 2008-03-26 | 2014-11-11 | Nec Corporation | Wavelength variable laser device, and method and program for controlling the same |
-
1993
- 1993-02-18 JP JP05125793A patent/JP3259862B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06244488A (en) | 1994-09-02 |
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