JPS60264130A - Laser diode drive circuit - Google Patents

Laser diode drive circuit

Info

Publication number
JPS60264130A
JPS60264130A JP59120441A JP12044184A JPS60264130A JP S60264130 A JPS60264130 A JP S60264130A JP 59120441 A JP59120441 A JP 59120441A JP 12044184 A JP12044184 A JP 12044184A JP S60264130 A JPS60264130 A JP S60264130A
Authority
JP
Japan
Prior art keywords
laser diode
level
circuit
modulation
output
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.)
Granted
Application number
JP59120441A
Other languages
Japanese (ja)
Other versions
JPH0238026B2 (en
Inventor
Kunio Tejima
手島　邦夫
Kiwamu Matsushita
松下　究
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Priority to JP59120441A priority Critical patent/JPS60264130A/en
Publication of JPS60264130A publication Critical patent/JPS60264130A/en
Publication of JPH0238026B2 publication Critical patent/JPH0238026B2/ja
Granted legal-status Critical Current

Links

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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0427—Electrical excitation ; Circuits therefor for applying modulation to the laser

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
  • Optical Communication System (AREA)

Abstract

PURPOSE:To keep a drive level of a laser diode constant in high speed and to obtain a laser diode output with a low distortion by providing a DC level fixing circuit fixing a DC level of a modulation signal input and a DC coupling circuit superimposing a variable DC level on an output of the said DC level fixing circuit. CONSTITUTION:A base band video signal inputted to a modulation input terminal 5 is subject to DC limit for its pedestal level by a clamp circuit 20, the result is given to an inverting input of a differential amplifier 21, from which the signal is outputted to a resistor 6 as a negative modulation signal and fed to the laser diode 1. On the other hand, a DC bias current driving the laser diode 1 controls a non-inverting input of the differential amplifier 21 by setting a voltage at a bias set terminal 22, a DC bias voltage superimposed on the modulation signal is impressed to a resistor 6, transistors 3, 4 of Darlington connection are drives, causing a DC lighting level of the laser diode 1 to be set. Thus, the base band video signal is operated in the range of a constant drive current versus light emitting output characteristic of the laser diode 1.

Description

【発明の詳細な説明】 〔発明の技術分野〕 この発明は、トランジスタ等によるレーザダイオード駆
動回路、特にレーザダイオードの発光特性の非直線性に
基づく歪の発生の低＄に関するものである。DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a laser diode drive circuit using a transistor or the like, and particularly to a low-cost distortion generation circuit based on the nonlinearity of the light emission characteristics of the laser diode.

〔従来技術〕[Prior art]

レーザダイオードは、第１図静特性図に示すように、所
定の閾値電流を越えるバイアス電流を流すと発振し、そ
の発光出力電力はバイアス電流と閾値電流との差に比例
する。しかしその直線性は十分良好とは言えず、レーザ
ダイオードを用いたアナログ光強度変調による光伝送で
は、非直線歪が問題となっている。この歪を改善する方
法として、レーザダイオードの発光出力の一部を受光素
子で検出し、その信号を増幅してレーザダイオードに負
帰還することにより、歪の低減を図る方法が従来から行
なわれている。As shown in the static characteristic diagram of FIG. 1, a laser diode oscillates when a bias current exceeding a predetermined threshold current is applied thereto, and its light emitting output power is proportional to the difference between the bias current and the threshold current. However, its linearity cannot be said to be sufficiently good, and nonlinear distortion is a problem in optical transmission by analog light intensity modulation using a laser diode. As a method to improve this distortion, a conventional method has been used to reduce distortion by detecting a part of the laser diode's light emission output with a light receiving element, amplifying the signal, and feeding it negative feedback to the laser diode. There is.

第２図は従来のレーザダイオード駆動回路の一例を示す
結線図である。図において１１１はレーザダイオード、
（２１はとのレーザダイオード等に電源を供給する直流
電源、＋３１　、　（４１１ｉレーザダイオードｉｌｌ
を駆動するためダーリントン接続されたＮＰＮ形トラン
ジスタ、（５）は抵抗１６）コンデンサ（７１を通じて
上記トランジスタ１３＋のベースに変調入力を加えるた
めの変調入力端子、（８）は上記レーザダイオードの発
光出力の一部を光導波路（９）を通して受光する受光素
子である。FIG. 2 is a wiring diagram showing an example of a conventional laser diode drive circuit. In the figure, 111 is a laser diode,
(21 is a DC power supply that supplies power to the laser diode, etc., +31, (411i laser diode ill
(5) is a modulation input terminal for applying a modulation input to the base of the transistor 13+ through a resistor (16) and a capacitor (71), and (8) is a modulation input terminal for applying a modulation input to the base of the transistor (13+) through the resistor (16) and capacitor (71). This is a light receiving element that receives a portion of light through an optical waveguide (9).

上記のように構成されたレーザダイオード駆動回路にお
いては、レーザダイオード＋１１はトランジスタ（４１
からその閾値電流以上のバイアス電流を供給され、変調
入力端子（５１から入力される変調信号に応じた発光動
作をする。レーザダイオード（１）の発光出力の一部は
、光導波路（９）を介して受光素子（８１に伝送受光さ
れる。In the laser diode drive circuit configured as described above, the laser diode +11 is a transistor (41
A bias current higher than the threshold current is supplied from the laser diode (1), and the laser diode (1) emits light in accordance with the modulation signal input from the modulation input terminal (51). The light is transmitted and received by the light receiving element (81).

受光素子（８１からはレーザダイオード（１）が送出す
る光出力信号に比例した受光電流が出力され、その直流
成分、変調信号成分ともに制御信号としてトランジスタ
１３１　、１４１からなる電流増幅器に入力される。上
記制御信号により負帰還がか＼るために、レーザダイオ
ード（１）の非直線性が補償され、光出力信号の変調波
形歪が改善される。A light-receiving current proportional to the optical output signal sent out by the laser diode (1) is output from the light-receiving element (81), and both its DC component and modulation signal component are input as control signals to a current amplifier consisting of transistors 131 and 141. Since negative feedback is generated by the control signal, the nonlinearity of the laser diode (1) is compensated, and the modulation waveform distortion of the optical output signal is improved.

しかるに従来のレーザダイオード駆動回路においては、
変調入力端子（５）からの変調信号入力はコンデンサ（
７）により結合されているため、変調信号入力に含まれ
る直流略号の大きさによりてレーザダイオード（１）に
入力される電流のピーク値が変動し、その結果レーザダ
イオード変調領域が変動し第１図に示されるレーザダイ
オードの閾値附近の非直線部分に信号がかかつて波形歪
が発生するという欠点があった。However, in the conventional laser diode drive circuit,
The modulation signal input from the modulation input terminal (5) is connected to the capacitor (
7), the peak value of the current input to the laser diode (1) changes depending on the magnitude of the DC symbol included in the modulation signal input, and as a result, the laser diode modulation area changes and the first There is a drawback that the signal is distorted in the nonlinear portion near the threshold of the laser diode shown in the figure, causing waveform distortion.

上記欠点はベースバンド映像信号を伝送する場合に特に
問題となる。すなわちベースバンド映像信号のＡ　Ｐ　
Ｌ　（Ａｖｅｒａｇｅ　Ｐｉｃｔｕｒｅ　Ｌｅｖｅｌ　
−）の変化により、正変調方式の場合には同期レベルが
、また負変調方式の場合には白レベルがそれぞれ波形歪
を受ける。The above drawbacks are particularly problematic when transmitting baseband video signals. In other words, A P of the baseband video signal
L (Average Picture Level
-), the synchronization level in the case of the positive modulation method and the white level in the case of the negative modulation method are subjected to waveform distortion.

〔発明の概要〕[Summary of the invention]

この発明は上記従来回路の欠点を除去するためになされ
たもので、変調信号入力の直流分を再生し、差動増幅器
により、信号、バイアスを共にレーザ駆動部とＤＣ結合
することにより、変調入力信号の状態に拘らず一定の低
波形歪の得られるレーザダイオード駆動回路を提供する
ことを目的とするものである。This invention was made in order to eliminate the drawbacks of the above-mentioned conventional circuits, and by regenerating the DC component of the modulation signal input and DC-coupling both the signal and bias with the laser drive section using a differential amplifier, the modulation input It is an object of the present invention to provide a laser diode drive circuit that can obtain constant low waveform distortion regardless of the signal state.

〔発明の実施例〕[Embodiments of the invention]

第３図は、この発明の一実施例を示す結線図であシ１１
１〜（６）、（８）、（９）は第２図の同一符号と同−
又は相当部分を示すものである。図において（２０）は
クランプ回路、（２１）は差動増幅器、（２２）はバイ
アス設定端子である。FIG. 3 is a wiring diagram showing one embodiment of the present invention.
1 to (6), (8), and (9) are the same as the same symbols in Figure 2.
or a considerable portion thereof. In the figure, (20) is a clamp circuit, (21) is a differential amplifier, and (22) is a bias setting terminal.

上記のように構成されたレーザダイオード駆動回路は変
調入力端子（５）に入力される信号がベースバンド映像
信号で変調方式が負変調である場合である。In the laser diode drive circuit configured as described above, the signal input to the modulation input terminal (5) is a baseband video signal and the modulation method is negative modulation.

第３図の実施例においても負帰還による歪補償の機能に
関しては第２図の回路と同様であるのでその説明を省略
し、ここではＤＣ直結による波形歪の改善機能について
のみ説明する。In the embodiment shown in FIG. 3, the function of distortion compensation by negative feedback is the same as that of the circuit shown in FIG. 2, so a description thereof will be omitted, and only the waveform distortion improvement function by direct DC connection will be explained here.

変調入力端子（５）に入力されたベースバンド映像信号
はクランプ回路（２０）によシ、ペデスタルレベルを直
流固定された後差動増１幅器（２１）の反転入力端子に
接続され、負変調信号として抵抗（６）に出力されレー
ザダイオード（１）に供給される。The baseband video signal input to the modulation input terminal (5) is connected to the inverting input terminal of the differential amplifier (21) after the pedestal level is fixed to DC by the clamp circuit (20). It is output as a modulation signal to the resistor (6) and supplied to the laser diode (1).

一方レーザダイオード（１１を駆動する直流バイアス電
流はバイアス設定端子（２２）の電圧を設定することに
よシ、差動増幅器（２１）の正相入力端子を制御し、変
調信号と重畳された直流バイアス電圧を抵抗１６＋に印
加しダーリントン接続のトランジスタ１３＋　１４１を
駆動しレーザダイオードｆｉ＋の直流発光レベルを設定
する。第４図は第３図の駆動回路の各部の波形図であ９
２４図（ａｌはクランプ回路（２０）によシペデスタル
レベルをＯｖにクランプした状態のクランプ回路（２０
）の変調信号波形、−第４図（ｂｌは差動増幅器（２１
）によシ反転し、かつ直流バイアスが重畳された変調信
号波形、第４図（ｃｌは変調光出力波形である。On the other hand, the DC bias current that drives the laser diode (11) controls the positive phase input terminal of the differential amplifier (21) by setting the voltage of the bias setting terminal (22), and the DC bias current that drives the laser diode (11) is superimposed on the modulation signal. A bias voltage is applied to the resistor 16+ to drive the Darlington-connected transistor 13+ 141 and set the DC light emission level of the laser diode fi+. Figure 4 is a waveform diagram of each part of the drive circuit in Figure 3.
Figure 24 (al is the clamp circuit (20) in which the pedestal level is clamped to Ov by the clamp circuit (20)
) modulation signal waveform, -Figure 4 (bl is the differential amplifier (21
), and the modulated signal waveform on which a DC bias is superimposed is shown in FIG. 4 (cl is the modulated optical output waveform).

上記のレーザダイオード駆動回路では、ベースバンド映
像信号がＡＰＬの変動によらずレーザダイオード（１）
の駆動電流−発光出力特性（Ｉ−Ｐカーブ）の一定鹸囲
・ニオ４図（ｃ）の（ｄ）〜（ｃ）の範囲）で動作する
ことになり、低歪のレーザダイオード駆動回路が実現で
きる。In the above laser diode drive circuit, the baseband video signal is driven by the laser diode (1) regardless of APL fluctuations.
The low distortion laser diode drive circuit operates within a constant range of drive current vs. light emission output characteristic (I-P curve) (range (d) to (c) in Figure 4 (c)). realizable.

なお上記実施例では変調入力信号がベースバンド映像信
号、変調方式が負変調の場合につき説明したが、正変調
方式でも差動増幅器（２１）の入力信号を正相に変更す
れば同様の効果が得られる。In the above embodiment, the modulation input signal is a baseband video signal and the modulation method is negative modulation. However, even if the modulation method is positive modulation, the same effect can be obtained by changing the input signal of the differential amplifier (21) to the positive phase. can get.

又変調入力信号がディジタル信号等の場合でも、クラン
プ回路（２０）をパルスクランプ回路に変換することに
より、パルスのデユーティ、マーク率によらずパルスピ
ーク光を一定に制御する負帰還形レーザダイオード駆動
回路が得られる。Furthermore, even when the modulation input signal is a digital signal, etc., by converting the clamp circuit (20) into a pulse clamp circuit, a negative feedback laser diode drive can be used to control the pulse peak light constant regardless of the pulse duty or mark rate. A circuit is obtained.

〔発明の効果〕〔Effect of the invention〕

この発明は以上説明したとおシ、クランプ回路と差動増
幅器のバイアス設定端子を設けることにより、レーザダ
イオードの駆動レベルを高速にかつ一定に保ち低歪波の
レーザダイオード出力を得られるという効果がある。As described above, this invention has the effect of keeping the drive level of the laser diode high and constant at high speed and obtaining a laser diode output with a low distortion wave by providing a clamp circuit and a bias setting terminal for the differential amplifier. .

【図面の簡単な説明】[Brief explanation of the drawing]

第１図はレーザダイオードの静特性、第２図は従来のレ
ーザダイオード駆動回路の一例を示す結線図、第３図は
この発明の一実施例を示す結線図、第４図は第３図のレ
ーザダイオード駆動回路の各、部波形図である。 図において（１）はレーザダイオード、＋３１　、１４
１はＮＰＮ形トランジスタ、（５）は変調入力端子、（
６）は抵抗、（７）はコンデンサ、（８１は受光素子、
（９）は光導波路、（２０）はクランプ回路、（２１）
は差動増幅器、（２２）はバイアス設定端子である。 尚、各図中同一符号は同−又は相当部分を示す。 代理人　大岩増雄 第１図 第２図Fig. 1 shows the static characteristics of a laser diode, Fig. 2 is a wiring diagram showing an example of a conventional laser diode drive circuit, Fig. 3 is a wiring diagram showing an example of the present invention, and Fig. 4 is the same as that shown in Fig. 3. FIG. 3 is a waveform diagram of each part of the laser diode drive circuit. In the figure, (1) is a laser diode, +31, 14
1 is an NPN transistor, (5) is a modulation input terminal, (
6) is a resistor, (7) is a capacitor, (81 is a light receiving element,
(9) is an optical waveguide, (20) is a clamp circuit, (21)
is a differential amplifier, and (22) is a bias setting terminal. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa Figure 1 Figure 2

Claims (1)

【特許請求の範囲】[Claims] レーザダイオードの直流バイアス及び変調信号電流を最
終段のトランジスタのコレクタから供給するための複数
段のトランジスタからなるダーリントン回路と、上記レ
ーザダイオードの出力の一部を光導波路を通じて受光し
その出力を検出するフォトダイオードと、このフォトダ
イオードの出力を上記ダーリントン回路の初段のトラン
ジスタベースの変調信号入力端に負帰還接続する負帰還
回路とを備えたレーザダイオード駆動回路において、上
記変調信号入力の直流レベルを固定する直流レベル固定
回路と、この直流レベル固定回路の出力に可変直流レベ
ルを重畳する直流結合回路とを備え）ことを特徴とする
レーザダイオード駆動回路。A Darlington circuit consisting of multiple stages of transistors for supplying the DC bias and modulation signal current of the laser diode from the collector of the final stage transistor, and a part of the output of the laser diode is received through an optical waveguide and the output is detected. In a laser diode drive circuit that includes a photodiode and a negative feedback circuit that connects the output of the photodiode to the first-stage transistor-based modulation signal input terminal of the Darlington circuit, the DC level of the modulation signal input is fixed. 1. A laser diode drive circuit comprising: a DC level fixing circuit for controlling a DC level; and a DC coupling circuit for superimposing a variable DC level on the output of the DC level fixing circuit.
JP59120441A 1984-06-12 1984-06-12 Laser diode drive circuit Granted JPS60264130A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP59120441A JPS60264130A (en) 1984-06-12 1984-06-12 Laser diode drive circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP59120441A JPS60264130A (en) 1984-06-12 1984-06-12 Laser diode drive circuit

Publications (2)

Publication Number Publication Date
JPS60264130A true JPS60264130A (en) 1985-12-27
JPH0238026B2 JPH0238026B2 (en) 1990-08-28

Family

ID=14786279

Family Applications (1)

Application Number Title Priority Date Filing Date
JP59120441A Granted JPS60264130A (en) 1984-06-12 1984-06-12 Laser diode drive circuit

Country Status (1)

Country Link
JP (1) JPS60264130A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1237239A2 (en) * 2001-02-28 2002-09-04 Hamamatsu Photonics K.K. Light-emitting element drive circuit
WO2003049328A1 (en) * 2001-12-07 2003-06-12 Matsushita Electric Industrial Co., Ltd. Optical transmitter apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1237239A2 (en) * 2001-02-28 2002-09-04 Hamamatsu Photonics K.K. Light-emitting element drive circuit
EP1237239A3 (en) * 2001-02-28 2004-12-01 Hamamatsu Photonics K.K. Light-emitting element drive circuit
WO2003049328A1 (en) * 2001-12-07 2003-06-12 Matsushita Electric Industrial Co., Ltd. Optical transmitter apparatus
CN1312862C (en) * 2001-12-07 2007-04-25 松下电器产业株式会社 Optical transmitter apparatus
US7298977B2 (en) 2001-12-07 2007-11-20 Matsushita Electric Industrial Co., Ltd. Optical transmitter

Also Published As

Publication number Publication date
JPH0238026B2 (en) 1990-08-28

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