JPS62177987A - Automatic power control method of semiconductor laser drive circuit - Google Patents
Automatic power control method of semiconductor laser drive circuitInfo
- Publication number
- JPS62177987A JPS62177987A JP1778486A JP1778486A JPS62177987A JP S62177987 A JPS62177987 A JP S62177987A JP 1778486 A JP1778486 A JP 1778486A JP 1778486 A JP1778486 A JP 1778486A JP S62177987 A JPS62177987 A JP S62177987A
- Authority
- JP
- Japan
- Prior art keywords
- semiconductor laser
- power control
- automatic power
- current
- temperature
- 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
Links
- 239000004065 semiconductor Substances 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims description 16
- 238000006243 chemical reaction Methods 0.000 claims abstract description 4
- 238000012544 monitoring process Methods 0.000 abstract 1
- 230000007423 decrease Effects 0.000 description 12
- 230000003287 optical effect Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 2
- 235000002568 Capsicum frutescens Nutrition 0.000 description 1
- 210000000078 claw Anatomy 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000013256 coordination polymer Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
Classifications
-
- 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
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
-
- 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
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
- H01S5/06837—Stabilising otherwise than by an applied electric field or current, e.g. by controlling the temperature
Abstract
Description
【発明の詳細な説明】
(技術分野)
本発明は半導体レーザ駆動回路の自動電力制御方法に関
し、より詳細には半導体レーザを駆動する駆動回路の自
動電力制御をディジタル的に処理するのに適用し得る半
導体レーザ駆動回路の自動電力制御方法に関するもので
ある。DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an automatic power control method for a semiconductor laser drive circuit, and more specifically, it is applied to digitally process automatic power control for a drive circuit that drives a semiconductor laser. The present invention relates to an automatic power control method for a semiconductor laser drive circuit.
(従来技術)
従来、半導体レーザ駆動回路の自動電力制御には、温度
変化に伴う半導体レーザ(Lr))の光出力を一定にす
るため、フォトダイオード(PD)からのモニタ電流を
ディジタル的に処理して半導体レーザ駆動電流制御を行
う方法がある。この方法においては、半導体レーザのI
/L特性(先出カー順電力特性)曲線が温度変化によっ
て異なるので自動電力側1ll(APC)の分解能が低
下するという欠点がある。また、制御電流範囲を広くと
らなければならないため、分解能を上げることが出来ず
、半導体レーザに過電流(サージ電流等)を流しこれを
劣化、破壊する恐れがある。(Prior art) Conventionally, automatic power control of a semiconductor laser drive circuit involves digitally processing the monitor current from a photodiode (PD) in order to keep the optical output of the semiconductor laser (Lr) constant due to temperature changes. There is a method of controlling the semiconductor laser drive current. In this method, the I
Since the /L characteristic (previous car order power characteristic) curve differs depending on the temperature change, there is a drawback that the resolution of the automatic power side 111 (APC) decreases. Furthermore, since the control current range must be widened, the resolution cannot be improved, and there is a risk that an overcurrent (surge current, etc.) may flow into the semiconductor laser and cause it to deteriorate or be destroyed.
(目的)
本発明は、上述した従来の欠点に鑑みてなされたもので
、その目的とするところは、温度変動で容易に変化する
半導体レーザ光出力を一定にするために、半導体駆動電
流、すなわち半導体レーザの光出力制御をディジタル/
アナログコンバータ等を用いてディジタル的に処理する
自動電力制御において、常に高分解能の状態で半導体レ
ーザの電力制御を行うことができる半導体レーザ駆動回
路の自動電力制御方法を提供することである。(Objective) The present invention has been made in view of the above-mentioned drawbacks of the conventional art, and its purpose is to maintain a constant semiconductor laser light output, which easily changes due to temperature fluctuations, by changing the semiconductor drive current, that is, to Digitally control the optical output of semiconductor lasers
An object of the present invention is to provide an automatic power control method for a semiconductor laser drive circuit that can always perform power control of a semiconductor laser in a high-resolution state in automatic power control that is digitally processed using an analog converter or the like.
(構成)
本発明は−J−記の目的を達成させるため、半導体レー
ザを駆動する駆チj1回路の自動電力制御をディジタル
的な処理で行う半導体レーザ駆動回路の自動電力制御方
法において、ディジタルからアナ【二Iグのi検出力レ
ベルを温度制御し、該アナログ出力信−号が入力される
演算増幅器の基Yf1!電イ☆を同時に温度制御するこ
とを特徴とUまたものである。(Structure) In order to achieve the object stated in -J-, the present invention provides an automatic power control method for a semiconductor laser drive circuit in which automatic power control of a driver circuit for driving a semiconductor laser is performed by digital processing. The base Yf1 of the operational amplifier temperature-controls the detection power level of the analog output signal and inputs the analog output signal. It is also characterized by temperature control at the same time.
以下、本発明の一実施例に基づいて具体的に説明する。Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.
第1図は本発明による半導体レーザ駆動回路の一実施例
を示す回路図で、1はゲートアレイ、2ば8ビツトの中
央処理ユニット((’l)[J)、3は8ビットのディ
ジタル/アナログ(I)/ A )コンバータ、4はリ
レー、RI〜R,5は抵抗、′T”hl。FIG. 1 is a circuit diagram showing an embodiment of a semiconductor laser driving circuit according to the present invention, where 1 is a gate array, 2 is an 8-bit central processing unit (('l)[J), and 3 is an 8-bit digital/ Analog (I)/A) converter, 4 is relay, RI~R, 5 is resistor, 'T''hl.
1”h2はサーミスタ、[C1は演算増幅器、01゜Q
、 21;): l・ランジスタ、L、 Dは半導体レ
ーザ、PDはフ第1・ダイオード、5は演算増幅器、6
は比較器、7は半導体I/−ザ変変信信号8 Ll半導
体1/ −チリ−+2ツY−で・あ7゜
上iISシた回路において、半導体レーザ1.[)から
のモニタ光はツメ1−ダイオードP i”)で受光され
、そのモニタ電流は演算増幅器5を介して生導体l/−
ザ規定電力を決定する任意の基準L/ヘルと比較器6を
介して比較される。この比較器6がらの出力はゲートア
レイ1へ送られ、さらにCP LJ 2を1J11つて
8ビツトデータとして]) / A ′:jンバータ3
に入力される。このD / Aコンパル夕3の出力N流
1 outは入力データFF(IIEX)で量大、00
で最小となる。ここで最大電流値は■□9.端了と15
v間の抵抗値r(抵抗R3とサーミスタTh2の並列抵
抗値)で決定される。−・般に、この場合の最大電流値
は単純に5/r(A)である。1"h2 is thermistor, [C1 is operational amplifier, 01゜Q
, 21;): L transistor, L and D are semiconductor lasers, PD is a first diode, 5 is an operational amplifier, 6
is a comparator, and 7 is a semiconductor I/- the conversion signal 8 Ll semiconductor 1/- chili + 2 Y-. The monitor light from [) is received by the claw 1-diode P i''), and the monitor current is passed through the operational amplifier 5 to the live conductor l/-
It is compared via a comparator 6 with an arbitrary reference L/Hel to determine the specified power. The output of this comparator 6 is sent to the gate array 1, and further CP LJ 2 is added to 1J1 as 8-bit data]) / A':j converter 3
is input. The output N flow 1 out of this D/A comparator 3 is input data FF (IIEX) with a large amount, 00
is the minimum. Here, the maximum current value is ■□9. End of story and 15
It is determined by the resistance value r between v (parallel resistance value of resistor R3 and thermistor Th2). - Generally, the maximum current value in this case is simply 5/r (A).
第1図から理解されるように、最大出力電流値は温度F
、lJに伴って増加しかつ温度下降に伴って減少する。As can be understood from Figure 1, the maximum output current value is
, lJ, and decreases as the temperature decreases.
D / A 、71ンバータ3の出力電流I。utは、
次いで、演算増幅器I 01の反転入力端子に入力され
て電圧変換される。その出力電圧はT。ut −’Om
Aのたき最小で、非反転入力端子の)S準電圧■と同電
位になる。このとき半導体レーザ駆動電流用トランジス
タQ2のコレクタ電位は最小となり、該トランジスタQ
2のコレクタ電流、つまり半導体レーザL I)に流れ
る電流は最大となる。逆にI out ==M、X時(
FF時)には、演算増幅器IC1の出力電圧は最大(V
+5 / r X抵抗R4)となり、半導体駆動電流
は最小となる。D/A, 71 Output current I of inverter 3. ut is
The signal is then input to the inverting input terminal of the operational amplifier I01 and converted into a voltage. Its output voltage is T. ut -'Om
At the minimum value of A, it becomes the same potential as the )S quasi voltage (■) of the non-inverting input terminal. At this time, the collector potential of the semiconductor laser drive current transistor Q2 becomes the minimum, and the transistor Q
The collector current of No. 2, that is, the current flowing through the semiconductor laser LI) becomes maximum. Conversely, when I out ==M,
At the time of FF), the output voltage of operational amplifier IC1 is the maximum (V
+5/r x resistance R4), and the semiconductor drive current becomes minimum.
第1図から明らかなように、演算増幅器I C1の基準
電圧Vは+1.2 Vを抵抗R1と抵抗r2(抵抗R2
とサーミスタ’rhiの並列抵抗イ直)で分圧した値で
あり、基準電圧Vは温度士昇に伴って降下する。つまり
、半導体レーザ駆動最大電流値(FF時)は増加し、逆
に温度下降時には減少する。As is clear from FIG. 1, the reference voltage V of the operational amplifier IC1 is +1.2 V between the resistor R1 and the resistor
The reference voltage V is a value divided by the parallel resistance of the thermistor 'rhi' and the thermistor 'rhi', and the reference voltage V falls as the temperature rises. That is, the maximum current value for driving the semiconductor laser (in FF mode) increases, and conversely decreases when the temperature decreases.
上述した実施例におけるごとく、負の温度係数を有する
2個のサーミスタ(Thl、Th2)を用いた制御方法
によって、温度下條時及び温度上昇時にそれぞれ以下の
制御が行われる。As in the embodiment described above, the following control is performed when the temperature is decreasing and when the temperature is increasing, respectively, by the control method using two thermistors (Thl, Th2) having negative temperature coefficients.
温度下降時、(al D / Aコンバータ3の最大出
力電流■。1は減少し半導体レーザ駆動電流の制御範囲
が挟くなり、fbl演算増幅器ICIの基準電圧■が1
−昇し、半導体レーザ駆動最大電流値が減少するという
制御で低温時の半導体レーザ■、Dの■/L特性の曲線
が急になり、しきい値電流11hが減少することに対す
る自動電力制御の分解能の低下を防ぐことができる〔8
ビツト(256)分解能で制御できる半導体レーザ駆動
電流範囲を最適位置に設定し、■ステップの電流幅を狭
くすることにより分解能を上げる)。一般的な半導体レ
ーザのI/L特性曲線は第2図に示しである。When the temperature falls, the maximum output current (■.1 of the al D/A converter 3) decreases, the control range of the semiconductor laser drive current narrows, and the reference voltage (■) of the fbl operational amplifier ICI decreases to 1.
- Automatic power control to cope with the fact that the curve of the ■/L characteristics of semiconductor lasers ■ and D at low temperatures becomes steeper and the threshold current 11h decreases due to control in which the semiconductor laser drive maximum current value decreases. Decrease in resolution can be prevented [8
The semiconductor laser driving current range that can be controlled with (256) bit resolution is set at the optimum position, and the resolution is increased by narrowing the step current width). The I/L characteristic curve of a typical semiconductor laser is shown in FIG.
温度上昇時、(al D / Aコンバータ3の最大出
力電流■。utは増加し、半導体レーザ駆動電流の制御
範囲は広くなり、山)演算増幅器ICIの基準電圧■が
−下し、半導体駆動最大電流値が増加するという制御で
高温時の半導体レーザL DのI / L特性曲線が穏
やかになり、しきい値電流Itkが増加することに対し
ての分解能を上げることができる。この場合、低温時に
比べ8ビツト分解能の1ステツプの電流幅は広くなるが
、I/I、特性の曲線は穏やかであるため、1ステツプ
の半導体装置ザの光出力レベル幅は変わらない。When the temperature rises, (maximum output current ■.ut of the AL D/A converter 3 increases, the control range of the semiconductor laser drive current becomes wider, and the reference voltage ■ of the operational amplifier ICI decreases, and the maximum output current ■.ut of the semiconductor laser drive increases.) By controlling the current value to increase, the I/L characteristic curve of the semiconductor laser LD at high temperatures becomes gentle, and the resolution with respect to an increase in the threshold current Itk can be improved. In this case, the current width of one step with 8-bit resolution becomes wider than that at low temperature, but the I/I characteristic curve is gentle, so the optical output level width of the one-step semiconductor device remains unchanged.
次に、従来の自動電力制御での半導体レーザ駆動制御電
流を示す第3図のT/T、特性曲線図、および本発明に
よる自動電力制御における半導体レーザ駆動制御電流を
示す第4図のl/L特性曲線図を参照して両者の分解能
について説明する。尚、第3図および第4図には分解能
の違いを数値的に表すために具体的な数値が書き加えら
れている。Next, the T/T and characteristic curve diagrams in FIG. 3 showing the semiconductor laser drive control current in the conventional automatic power control, and the l/T in FIG. 4 showing the semiconductor laser drive control current in the automatic power control according to the present invention. The resolution of both will be explained with reference to the L characteristic curve diagram. Note that specific numerical values have been added to FIGS. 3 and 4 to numerically represent the difference in resolution.
第3図において、8ビウl−D/Aコンバータで従来の
自動電力制御の分解能について、電流的な分解能は温度
に関係なく一定で、その値は、70mA/256’−i
o、27mA
である。In Fig. 3, regarding the resolution of conventional automatic power control using an 8 biu l-D/A converter, the current resolution is constant regardless of temperature, and its value is 70 mA/256'-i
o, 27 mA.
0℃の時の光出力レベルでの1ステップ分解能は、
5mW/20mAX0.27mA=0.0675mW2
O℃の時の光出力レベルでの1ステップ分解能は、
5mW/25mAX0.27mA=0.054mW4O
℃の時の光出力レベルでの1ステップ分解能は、
5mW/30mAX0.27mA−0,045mWであ
る。第3図中aは自動電力制御での制御電流範囲(70
mA)を示す。One step resolution at optical output level at 0℃ is 5mW/20mAX0.27mA=0.0675mW2
One step resolution at optical output level at O℃ is 5mW/25mAX0.27mA=0.054mW4O
The one-step resolution at the optical output level at °C is 5 mW/30 mAX 0.27 mA - 0,045 mW. In Figure 3, a is the control current range (70
mA).
第4図において、8ビットD/A:7ンバータでの本発
明の自動電力制御の分解能について、0℃の時の電流的
分解能は、
20mA/256’−0,078mAで、光出力レベル
での1ステップ分解能は
5mW/20mAX0.078mA−0,0195mW
2O℃の時の電流的分解能は、
25mA/256’−0,097mAで、光出力レベル
での1ステップ分解能は
5mW/25mA xo、097mA−0,0194m
W40℃の時の電流的分解能は、
30mA/256#0.1172mAで、光出力レベル
での1ステップ分解能は
5mW/30mAXO,1,172mA−0,195m
Wである。第4図中■は0℃での制御電流範囲(20m
A)、■は20°Cでの制御電流範囲(25mA)そし
て■は40’Cでの制御電流範囲(30mA)を示す。In Fig. 4, regarding the resolution of the automatic power control of the present invention using an 8-bit D/A:7 inverter, the current resolution at 0°C is 20mA/256'-0,078mA, and the optical output level is 20mA/256'-0,078mA. 1 step resolution is 5mW/20mAX0.078mA-0,0195mW
The current resolution at 20°C is 25mA/256'-0,097mA, and the one-step resolution at the optical output level is 5mW/25mA xo, 097mA-0,0194m.
Current resolution at W40℃ is 30mA/256#0.1172mA, and one step resolution at optical output level is 5mW/30mAXO, 1,172mA-0,195m
It is W. ■ in Figure 4 indicates the control current range at 0℃ (20m
A), ■ indicates the control current range at 20°C (25 mA) and ■ indicates the control current range at 40'C (30 mA).
以上の計算時果によれば、本発明による自動電力制御と
従来例とを比較すると、光出力レヘルの1ステップ分解
能は上がり、温度変動によっても分解能は変わらない。According to the above calculation results, when the automatic power control according to the present invention is compared with the conventional example, the one-step resolution of the optical output level increases, and the resolution does not change even with temperature fluctuations.
以上のように、半導体レーザLDの光出力は、周囲温度
の変動で容易に変化するので、温度が変化しても一定光
出力が得られないように、モニタ光を検知し、半導体レ
ーザ駆動電流にフィードバックする自動電力制御(A
P C)機能を有する半導体レーザ駆動回路で、モニタ
光を受光素子(フォトダイオード)で受け、その電流を
デジタル的に処理し、最終的にD/Aコンバータを用い
てその出力電流によって駆動電流を制御する自動電力制
御方法において、T/L特性の変化による分解能の低下
を防ぐためD/Aコンバータの出力電流を温度制御する
。また、その出力電流が入力される演算増幅器の基準電
圧を温度制御することにより半導体レーザ駆動最大電流
値も制御し、同時に駆動電流範囲を制御する。As mentioned above, the optical output of the semiconductor laser LD easily changes due to fluctuations in the ambient temperature, so in order to prevent a constant optical output even if the temperature changes, monitor light is detected and the semiconductor laser drive current is adjusted. Automatic power control (A
A semiconductor laser drive circuit with PC) function receives monitor light with a light receiving element (photodiode), digitally processes the current, and finally converts the output current into a drive current using a D/A converter. In the automatic power control method, the output current of the D/A converter is temperature-controlled in order to prevent a decrease in resolution due to changes in T/L characteristics. Further, by controlling the temperature of the reference voltage of the operational amplifier to which the output current is input, the semiconductor laser driving maximum current value is also controlled, and at the same time, the driving current range is controlled.
(効果)
途上のごとく、本発明によれば、ディジタルからアナロ
グの変換出力レベルを温度制御し、該アナログ出力信号
が入力される演算増幅器の基準電位を同時に温度制御す
ることにより、低温時に半導体レーザのI/L特性の曲
線が急になり、しきい値電流が減少することに対する自
動電力制御の分解能の低下を防ぎ、また、高温時に半導
体レーザのI / 1.、特性の曲線が穏やかになり、
しきい値電流が増加することに対する自動電力制御の分
解能を−にげることかできるという効果を奏する半導体
レーザ駆動回路の自動電力制御方法を提供することがで
きる。(Effects) According to the present invention, by temperature-controlling the digital-to-analog conversion output level and simultaneously temperature-controlling the reference potential of the operational amplifier to which the analog output signal is input, the semiconductor laser can be operated at low temperatures. This prevents the resolution of automatic power control from decreasing due to the steepening of the I/L characteristic curve and decreasing threshold current, and also prevents the I/L characteristic curve of the semiconductor laser from decreasing at high temperatures. , the characteristic curve becomes gentler,
It is possible to provide an automatic power control method for a semiconductor laser drive circuit that has the effect of reducing the resolution of automatic power control with respect to an increase in threshold current.
第1図は本発明による半導体レーザ駆動回路の自動電力
制御方法を提供する回路図、第2図は一般的な半導体レ
ーザのI/L特性を示す特性曲線図、第3図は従来の自
動電力制御における半導体レーザ駆動制御電流を示すI
/L特性曲線図、第4図は本発明の自動電力制御におけ
る半導体レーザ駆動制御電流を示すI/L特性曲線図で
ある。Fig. 1 is a circuit diagram providing an automatic power control method for a semiconductor laser drive circuit according to the present invention, Fig. 2 is a characteristic curve diagram showing I/L characteristics of a general semiconductor laser, and Fig. 3 is a conventional automatic power control method. I indicating the semiconductor laser drive control current in control
FIG. 4 is an I/L characteristic curve diagram showing the semiconductor laser drive control current in automatic power control of the present invention.
Claims (1)
ジタル的な処理で行う半導体レーザ駆動回路の自動電力
制御方法において、ディジタルからアナログの変換出力
レベルを温度制御し、該アナログ出力信号か入力される
演算増幅器の基準電位を同時に温度制御することを特徴
とする半導体レーザ駆動回路の自動電力制御方法。In an automatic power control method for a semiconductor laser drive circuit in which automatic power control of a drive circuit that drives a semiconductor laser is performed by digital processing, the digital to analog conversion output level is temperature-controlled, and the analog output signal is input. An automatic power control method for a semiconductor laser drive circuit, characterized by simultaneously controlling the temperature of a reference potential of an amplifier.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1778486A JPS62177987A (en) | 1986-01-31 | 1986-01-31 | Automatic power control method of semiconductor laser drive circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1778486A JPS62177987A (en) | 1986-01-31 | 1986-01-31 | Automatic power control method of semiconductor laser drive circuit |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS62177987A true JPS62177987A (en) | 1987-08-04 |
Family
ID=11953340
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP1778486A Pending JPS62177987A (en) | 1986-01-31 | 1986-01-31 | Automatic power control method of semiconductor laser drive circuit |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS62177987A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5023431A (en) * | 1989-08-11 | 1991-06-11 | Massachusetts Institute Of Technology | Linearized thermal feedback circuit and temperature controller circuit utilizing the same |
US5363057A (en) * | 1992-01-30 | 1994-11-08 | Mitsubishi Denki Kabushiki Kaisha | Control device for power amplifier |
-
1986
- 1986-01-31 JP JP1778486A patent/JPS62177987A/en active Pending
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5023431A (en) * | 1989-08-11 | 1991-06-11 | Massachusetts Institute Of Technology | Linearized thermal feedback circuit and temperature controller circuit utilizing the same |
US5363057A (en) * | 1992-01-30 | 1994-11-08 | Mitsubishi Denki Kabushiki Kaisha | Control device for power amplifier |
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