JPH0127309Y2 - - Google Patents
Info
- Publication number
- JPH0127309Y2 JPH0127309Y2 JP1983198260U JP19826083U JPH0127309Y2 JP H0127309 Y2 JPH0127309 Y2 JP H0127309Y2 JP 1983198260 U JP1983198260 U JP 1983198260U JP 19826083 U JP19826083 U JP 19826083U JP H0127309 Y2 JPH0127309 Y2 JP H0127309Y2
- Authority
- JP
- Japan
- Prior art keywords
- light
- emitting element
- output
- light emitting
- circuit
- 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
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- 230000006866 deterioration Effects 0.000 claims description 23
- 238000001514 detection method Methods 0.000 claims description 11
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
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- Optical Communication System (AREA)
Description
【考案の詳細な説明】
〈産業上の利用分野〉
本考案は、発光素子の光出力を受光素子でモニ
タし、一定の光出力を得る発光素子のAPC回路
に関するものである。[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an APC circuit for a light emitting element that monitors the light output of the light emitting element with a light receiving element to obtain a constant light output.
〈従来技術〉
従来知られている発光素子のAPC回路の構成
を第１図に示す。<Prior Art> The configuration of a conventionally known APC circuit for a light emitting device is shown in FIG.
第１図において、１は入力信号Ｄを受けて駆動
電流Idを出力してレーザーダイオード発光素子２
を発光させる駆動回路、３は発光素子２の光出力
をモニタするフオトダイオード受光素子、４は受
光素子３のモニタ出力が一方の入力に供給され、
他方の入力端子には基準信号erが供給される比較
増幅器、５は発光素子２と直列に接続され比較増
幅器４の出力によつて制御されるバイアス電流Ib
を生じるバイアス電流源である。尚、駆動回路１
の駆動電流IdがRZ信号等のように、平均値がマ
ーク率によつて変化する場合は、第１図の点線に
示すように基準信号erの値をマーク率情報によつ
て修正するようにしている。 In FIG. 1, 1 receives an input signal D and outputs a driving current I d to drive a laser diode light emitting element 2.
3 is a photodiode light receiving element that monitors the light output of the light emitting element 2; 4 is a photodiode light receiving element to which the monitor output of the light receiving element 3 is supplied to one input;
A comparison amplifier 5 is supplied with a reference signal e r to its other input terminal, and a bias current I b connected in series with the light emitting element 2 and controlled by the output of the comparison amplifier 4
It is a bias current source that generates . Furthermore, drive circuit 1
When the average value of the drive current I d changes depending on the mark rate, such as in the RZ signal, the value of the reference signal e r is corrected according to the mark rate information as shown by the dotted line in Figure 1. That's what I do.
このようなAPC回路において、駆動回路１に
入力信号Ｄが与えられると、発光素子２に駆動電
流Idが供給され、発光素子２は発光する。 In such an APC circuit, when an input signal D is applied to the drive circuit 1, a drive current Id is supplied to the light emitting element 2, and the light emitting element 2 emits light.
ところで、一般に、レーザーダイオードのよう
な発光素子は第２図に示すように、発光を始める
閾値電流Ithが周囲温度の上昇（高温側）に伴い
増大する特性を持つているため、温度上昇により
閾値電流Ithが増大した分だけ余計に電流を供給
しなければならない。 By the way, as shown in Figure 2, light-emitting elements such as laser diodes generally have the characteristic that the threshold current I th for starting light emission increases as the ambient temperature rises (on the high temperature side). An additional current must be supplied in proportion to the increase in the threshold current I th .
このため、発光素子２の近傍に発光素子２の光
出力をモニタする受光素子３を設け、このモニタ
出力と基準信号erとを比較増幅器４で比較し、こ
の比較増幅器４の出力によりバイアス電流源５を
制御して閾値電流Ithが増大した分だけ余計にバ
イアス電流Ibを供給して、温度変化による発光素
子の光出力の変化を補償していた。 For this reason, a light receiving element 3 is provided near the light emitting element 2 to monitor the optical output of the light emitting element 2, and the monitor output and the reference signal e r are compared by a comparator amplifier 4, and the bias current is determined by the output of the comparator amplifier 4. The source 5 is controlled to supply an extra bias current I b corresponding to the increase in the threshold current I th to compensate for changes in the light output of the light emitting element due to temperature changes.
以上が、従来知られている発光素子のAPC回
路であるが、このような回路は、次に述べる欠点
を持つていた。 The above is a conventionally known APC circuit for a light emitting element, but such a circuit has the following drawbacks.
即ち、発光素子の経時変化による寿命（劣
化）を検出が困難比較増幅器の動作範囲が広く
なるという点である。 That is, it is difficult to detect the lifetime (deterioration) of the light emitting element due to changes over time, and the operating range of the comparison amplifier becomes wider.
発光素子は、第２図に示すように、その経時変
化（劣化）によつても閾値電流Ithは上昇し、発
光素子の寿命は、通常、閾値電流Ithが初期値の
約1.5倍になつたことで判断するが、上記説明の
ように、発光素子の閾値電流Ithは、周囲温度の
上昇によつても増大するため、経時変化による閾
値電流Ithの増大分と温度変化による閾値電流Ith
の増大分の和に対応した比較器出力によりバイア
ス電流が制御される。このため、比較器出力を監
視しても、発光素子の経時変化による劣化を検出
することができず、また、比較増幅器が、温度変
化及び経時変化による閾値電流の増大分の和に対
応して動作するため、その動作範囲が広くなると
いう欠点を持つていた。 As shown in Fig. 2, the threshold current I th of a light emitting element increases as it changes over time (deterioration), and the lifespan of a light emitting element is usually such that the threshold current I th is approximately 1.5 times its initial value. As explained above, the threshold current I th of a light emitting element also increases due to a rise in ambient temperature, so the increase in threshold current I th due to changes over time and the threshold due to temperature changes are determined by Current I th
The bias current is controlled by the comparator output corresponding to the sum of the increases. Therefore, even if the comparator output is monitored, it is not possible to detect deterioration of the light emitting element due to changes over time. Because of this, it had the disadvantage that its operating range was wide.
〈考案の目的〉
本考案は、上述した欠点を改良したもので、発
光素子の経時変化による劣化の検出を可能にし、
バイアス電流を制御する比較増幅器の動作範囲が
小さい発光素子のAPC回路を提供することを目
的とする。<Purpose of the invention> The present invention improves the above-mentioned drawbacks, and makes it possible to detect deterioration due to changes in light emitting elements over time.
It is an object of the present invention to provide an APC circuit for a light emitting device in which a comparator amplifier that controls a bias current has a small operating range.
〈考案の構成〉
本考案は、発光素子と、この発光素子を駆動す
る駆動回路と、前記発光素子に接続されバイアス
電流を供給する可変出力のバイアス電流源と、前
記発光素子の出力光を受光する受光素子と、この
受光素子の出力と基準信号とを比較して前記バイ
アス電流源を制御するための比較増幅器とを有す
る発光素子のAPC回路において、前記比較増幅
器の出力と劣化判定値とを比較して劣化検出信号
を出力する劣化検出回路を設けるとともに、前記
比較増幅器と前記バイアス電流源との間に、前記
比較増幅器の出力に前記発光素子の閾値電流の温
度係数に相当する可変係数を乗じ前記バイアス電
流源に出力制御信号として与える可変係数回路を
設けたことを特徴とするものである。<Structure of the invention> The invention comprises a light emitting element, a drive circuit for driving the light emitting element, a variable output bias current source connected to the light emitting element and supplying a bias current, and receiving light output from the light emitting element. In an APC circuit for a light-emitting element, the APC circuit for a light-emitting element has a light-receiving element that controls the output of the light-emitting element, and a comparison amplifier that compares the output of the light-receiving element with a reference signal to control the bias current source. A deterioration detection circuit that compares and outputs a deterioration detection signal is provided, and a variable coefficient corresponding to the temperature coefficient of the threshold current of the light emitting element is provided between the comparison amplifier and the bias current source at the output of the comparison amplifier. The present invention is characterized in that a variable coefficient circuit is provided to supply the bias current source as an output control signal.
〈実施例〉 第３図に本考案の実施例を示す。<Example> FIG. 3 shows an embodiment of the present invention.
本図において、第１図と符号が同じものはその
機能は同じであるので説明を省略する。 In this figure, the parts having the same reference numerals as those in FIG. 1 have the same functions, so a description thereof will be omitted.
本考案の特徴は、比較増幅器４の出力側に温度
係数を持つ可変係数回路６及び発光素子の劣化を
検出する劣化検出回路７を設けたことにある。 The feature of the present invention is that a variable coefficient circuit 6 having a temperature coefficient and a deterioration detection circuit 7 for detecting deterioration of the light emitting element are provided on the output side of the comparison amplifier 4.
この可変係数回路６は、比較増幅器の出力信号
に可変係数Ｋを掛けて、バイアス電流源５に制御
信号として与えるもので、可変係数Ｋは発光素子
２の閾値電流Ithの温度係数に相当する正の温度
係数を持つ。 This variable coefficient circuit 6 multiplies the output signal of the comparator amplifier by a variable coefficient K and provides it to the bias current source 5 as a control signal, and the variable coefficient K corresponds to the temperature coefficient of the threshold current I th of the light emitting element 2. It has a positive temperature coefficient.
また、劣化検出回路７は比較増幅器で構成さ
れ、その一方の端子には比較増幅器４の出力が供
給され、他方の入力端子には劣化判定値esが供給
され、この２つの入力信号を比較して劣化検出信
号Ｓを出力する。 The deterioration detection circuit 7 is composed of a comparator amplifier, one terminal of which is supplied with the output of the comparator amplifier 4, and the other input terminal of which is supplied with the deterioration judgment value e s , which compares these two input signals. and outputs a deterioration detection signal S.
この回路において、その動作は第１図に示す従
来の回路と同様に、発光素子２の周囲温度が上昇
すると、発光素子２の閾値電流Ithも増大し、発
光素子２の光出力が弱まると、受光素子３はこの
状態を検出し、比較増幅器４からはこれに対応し
た信号が出力される。一方、可変係数回路６は温
度特性を持ち、周囲温度の上昇によりその可変係
数Ｋが閾値電流Ithの温度特性と同じ特性で増加
する。バイアス電流源５の制御信号は、比較増幅
器４の出力に可変係数回路６の可変係数Ｋを掛け
たものであるから、バイアス電流源５の制御信号
も閾値電流Ithの温度特性と同じ特性で増加する。
これによつて、閾値電流Ithの温度変化を補償し
たバイアス電流源５の制御信号が得られ、比較増
幅器４の出力信号は閾値電流Ithの温度変化に影
響されなくなる。この可変係数回路６は、例え
ば、第４図に示すように、温度係数が負である感
温素子（サーミスタ）Rtを含む抵抗回路で構成
できる。 In this circuit, the operation is similar to the conventional circuit shown in FIG. 1. When the ambient temperature of the light emitting element 2 increases, the threshold current I th of the light emitting element 2 also increases, and the light output of the light emitting element 2 weakens. , the light receiving element 3 detects this state, and the comparator amplifier 4 outputs a signal corresponding to this state. On the other hand, the variable coefficient circuit 6 has a temperature characteristic, and as the ambient temperature rises, its variable coefficient K increases with the same characteristic as the temperature characteristic of the threshold current I th . Since the control signal for the bias current source 5 is the output of the comparator amplifier 4 multiplied by the variable coefficient K of the variable coefficient circuit 6, the control signal for the bias current source 5 also has the same characteristics as the temperature characteristics of the threshold current I th . To increase.
As a result, a control signal for the bias current source 5 that compensates for the temperature change in the threshold current I th is obtained, and the output signal of the comparator amplifier 4 is not affected by the temperature change in the threshold current I th . The variable coefficient circuit 6 can be configured, for example, as shown in FIG. 4, by a resistance circuit including a temperature sensing element (thermistor) R t having a negative temperature coefficient.
発光素子２が経時変化により劣化した場合、発
光素子２の閾値電流Ithは増大し、その光出力は
弱まり、比較増幅器４の入力側において、入力信
号が設定基準信号erよりも小さくなり、このた
め、比較増幅器４の出力信号が増加する。劣化検
出回路７の一方の入力端子には、劣化判定値esと
して、例えば、発光素子の閾値電流Ithの約1.5倍
に対応する電圧が接続されており、劣化検出回路
７は、比較増幅器４の出力と劣化判定値esとを比
較し、比較増幅器４の出力が劣化判定値esを上回
つたとき、劣化検出信号Ｓを発生する。 If the light-emitting element 2 deteriorates over time, the threshold current I th of the light-emitting element 2 will increase, its light output will weaken, and at the input side of the comparator amplifier 4 the input signal will become smaller than the set reference signal e r ; Therefore, the output signal of comparison amplifier 4 increases. A voltage corresponding to, for example, approximately 1.5 times the threshold current I th of the light emitting element is connected to one input terminal of the deterioration detection circuit 7 as the deterioration judgment value e s . The output of the comparison amplifier 4 is compared with the deterioration determination value e s , and when the output of the comparison amplifier 4 exceeds the deterioration determination value e s , a deterioration detection signal S is generated.
また、何らかの理由で発光素子２が故障した場
合でも、この故障を劣化検出回路７の同様の動作
により検出することができる。 Further, even if the light emitting element 2 fails for some reason, this failure can be detected by the similar operation of the deterioration detection circuit 7.
尚、バイアス電流源５として第５図に示すよう
に、トランジスタTrと可変抵抗Rxの直列回路を
用いれば、可変抵抗Rxの調整により発光素子２
の固体差による閾値電流Ithのばらつきを吸収す
ることができ、劣化判定値esを固定することがで
きる。 Incidentally, if a series circuit of a transistor T r and a variable resistor R x is used as the bias current source 5 as shown in FIG.
It is possible to absorb variations in the threshold current I th due to individual differences in the deterioration determination value e s .
〈考案の効果〉
以上述べたように、本考案によれば、比較増幅
器の出力側に温度特性を持つ可変係数回路と劣化
検出回路を設けているので、発光素子の温度変化
による閾値電流の増大の補償と、経時変化による
発光素子の劣化の検出とを容易に行なうことがで
き、また、比較増幅器の必要な動作範囲を従来の
ものと比べて小さくすることができる。<Effects of the invention> As described above, according to the invention, since the variable coefficient circuit with temperature characteristics and the deterioration detection circuit are provided on the output side of the comparison amplifier, the increase in threshold current due to temperature changes of the light emitting element is prevented. It is possible to easily compensate for this and to detect deterioration of the light emitting element due to changes over time, and the necessary operating range of the comparator amplifier can be made smaller than that of the conventional one.
第１図は従来の発光素子のAPC回路、第２図
は発光素子の光出力と閾値電流の関係図、第３図
は本考案の実施例による発光素子のAPC回路、
第４図は本考案の実施例によるAPC回路の可変
係数回路、第５図は本考案の実施例によるAPC
回路のバイアス電流源である。
１……駆動回路、２……発光素子、３……受光
素子、４……比較増幅器、５……バイアス電流
源、６……可変係数回路、Rt……感温素子、Tr
……トランジスタ、Rx……可変抵抗。
FIG. 1 is a conventional APC circuit of a light emitting device, FIG. 2 is a diagram showing the relationship between light output and threshold current of a light emitting device, and FIG. 3 is an APC circuit of a light emitting device according to an embodiment of the present invention.
Figure 4 shows a variable coefficient circuit of an APC circuit according to an embodiment of the present invention, and Figure 5 shows an APC circuit according to an embodiment of the present invention.
It is the bias current source for the circuit. DESCRIPTION OF SYMBOLS 1... Drive circuit, 2... Light emitting element, 3... Light receiving element, 4... Comparison amplifier, 5... Bias current source, 6... Variable coefficient circuit, R t ... Temperature sensing element, T r
...transistor, R x ...variable resistance.
Claims (1)
と、前記発光素子に接続されバイアス電流を供給
する可変出力のバイアス電流源と、前記発光素子
の出力光を受光する受光素子と、この受光素子の
出力と基準信号とを比較して前記バイアス電流源
を制御するための比較増幅器とを有する発光素子
のAPC回路において、前記比較増幅器の出力と
劣化判定値とを比較して劣化検出信号を出力する
劣化検出回路を設けるとともに、前記比較増幅器
と前記バイアス電流源との間に、前記比較増幅器
の出力に前記発光素子の閾値電流の温度係数に相
当する可変係数を乗じ前記バイアス電流源に出力
制御信号として与える可変係数回路を設けたこと
を特徴とする発光素子のAPC回路。 A light-emitting element, a drive circuit for driving the light-emitting element, a variable output bias current source connected to the light-emitting element and supplying a bias current, a light-receiving element for receiving output light from the light-emitting element, and a light-receiving element for receiving light output from the light-emitting element. In an APC circuit of a light emitting element having a comparison amplifier for comparing an output and a reference signal to control the bias current source, the output of the comparison amplifier is compared with a deterioration determination value to output a deterioration detection signal. A deterioration detection circuit is provided between the comparator amplifier and the bias current source, and an output control signal is provided to the bias current source by multiplying the output of the comparator amplifier by a variable coefficient corresponding to the temperature coefficient of the threshold current of the light emitting element. 1. An APC circuit for a light emitting element, characterized in that it is provided with a variable coefficient circuit that provides .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1983198260U JPS60108056U (en) | 1983-12-23 | 1983-12-23 | APC circuit of light emitting element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1983198260U JPS60108056U (en) | 1983-12-23 | 1983-12-23 | APC circuit of light emitting element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60108056U JPS60108056U (en) | 1985-07-23 |
| JPH0127309Y2 true JPH0127309Y2 (en) | 1989-08-15 |
Family
ID=30757103
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1983198260U Granted JPS60108056U (en) | 1983-12-23 | 1983-12-23 | APC circuit of light emitting element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60108056U (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52123185A (en) * | 1976-04-09 | 1977-10-17 | Fujitsu Ltd | Optical communication supervisory system |
| JPS5431834A (en) * | 1977-08-16 | 1979-03-08 | Nippon Carbureter | Feeder of liquefied gas fuel of internal combustion engine |
-
1983
- 1983-12-23 JP JP1983198260U patent/JPS60108056U/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52123185A (en) * | 1976-04-09 | 1977-10-17 | Fujitsu Ltd | Optical communication supervisory system |
| JPS5431834A (en) * | 1977-08-16 | 1979-03-08 | Nippon Carbureter | Feeder of liquefied gas fuel of internal combustion engine |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60108056U (en) | 1985-07-23 |
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