JPH10163555A - Method for controlling light output level and device for controlling light output level - Google Patents
Method for controlling light output level and device for controlling light output levelInfo
- Publication number
- JPH10163555A JPH10163555A JP32395896A JP32395896A JPH10163555A JP H10163555 A JPH10163555 A JP H10163555A JP 32395896 A JP32395896 A JP 32395896A JP 32395896 A JP32395896 A JP 32395896A JP H10163555 A JPH10163555 A JP H10163555A
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- circuit
- average value
- output
- bias current
- current
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は,光ファイバを伝送
媒体とする光通信システムの中の光送信器等に用いられ
る半導体レーザの駆動回路に関し,特にレーザの出力を
一定に保つ光出力補償回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for a semiconductor laser used in an optical transmitter or the like in an optical communication system using an optical fiber as a transmission medium, and more particularly to an optical output compensating circuit for maintaining a constant laser output. About.
【0002】[0002]
【従来の技術】従来,半導体レーザを使用した半導体レ
ーザ(以下,LDと呼ぶ)モジュールの駆動方法とし
て,レーザ発振を開始するしきい値電流Ith近傍の値
の直流バイアス電流Ibを印加し,さらに信号成分とし
てパルス変調電流Ip重畳する方法が一般的である。こ
こで,しきい値電流Ithは,周囲温度により変化す
る。このためLDを一定の電流で駆動した場合,周囲温
度により光出力レベルが変動が生じる。またLDの劣化
により電気信号を光信号に変換する効率である微分効率
ηが悪化し,光出力レベル,消光比が悪化する。2. Description of the Related Art Conventionally, as a method of driving a semiconductor laser (hereinafter referred to as LD) module using a semiconductor laser, a DC bias current Ib having a value near a threshold current Ith for starting laser oscillation is applied. In general, a pulse modulation current Ip is superimposed as a signal component. Here, the threshold current Ith changes depending on the ambient temperature. Therefore, when the LD is driven with a constant current, the light output level varies depending on the ambient temperature. Further, the differential efficiency η, which is the efficiency of converting an electric signal to an optical signal, is deteriorated due to the deterioration of the LD, and the light output level and the extinction ratio are deteriorated.
【0003】このため,光出力を一定に保つための方法
として,既に,特開平7−147446号公報及び特開
平4−82285号公報(以下,夫々従来技術1及び2
と呼ぶ)などが提案されている。[0003] For this reason, as a method for maintaining a constant optical output, Japanese Patent Application Laid-Open Nos. 7-147446 and 4-82285 (hereinafter referred to as prior arts 1 and 2 respectively) have been proposed.
Etc.) have been proposed.
【0004】図7は,従来技術1による光ファイバーモ
ジュールの駆動回路の構成を示すブロック図である。図
7に示すように,LD51の光出力を検出する受光素子
52と,LD51にパルス電流を供給するパルス電流変
調回路53と,パルス電流変調回路53のパルス電流値
を制御するパルス電流制御回路54と,受光素子の検出
出力を検出するパワーモニター回路55と,LD51を
発光するバイアス電流Ibを制御するバイアス電流制御
回路56を備えている。FIG. 7 is a block diagram showing a configuration of a driving circuit of an optical fiber module according to the prior art 1. As shown in FIG. 7, a light receiving element 52 for detecting the optical output of the LD 51, a pulse current modulation circuit 53 for supplying a pulse current to the LD 51, and a pulse current control circuit 54 for controlling the pulse current value of the pulse current modulation circuit 53 A power monitor circuit 55 for detecting a detection output of the light receiving element; and a bias current control circuit 56 for controlling a bias current Ib for emitting light from the LD 51.
【0005】ここで提案されているLD駆動回路は,要
約すると一定時間毎にバイアス電流Ibを2点以上変化
させて,その際のLD51の発光パワーを受光パワー検
出手段によって検出して,しきい値電流を算出し,しき
い値電流より若干高めのLD51の直流バイアス電流I
bをバイアス電流制御回路54に設定する。In the LD drive circuit proposed here, in summary, the bias current Ib is changed at two or more points at regular time intervals, and the light emission power of the LD 51 at that time is detected by the light reception power detection means, and the threshold is detected. Value current and calculate the DC bias current I of the LD 51 slightly higher than the threshold current.
b is set in the bias current control circuit 54.
【0006】また,LD51のしきい値電流と微分効率
ηの変化を検出することで,微分効率η等の変化に対応
したパルス電流にパルス電流制御回路54にて設定する
ことで光出力レベルを一定に保持している。Further, by detecting a change in the threshold current of the LD 51 and the differential efficiency η, the pulse current control circuit 54 sets a pulse current corresponding to the change in the differential efficiency η or the like, thereby setting the light output level. Holds constant.
【0007】次に,従来技術2について説明する。図8
は従来技術2に提案されている光出力補償回路を示す図
である。図8に示すように,光出力補償回路は,LDの
出力光信号から抽出したモニタ信号の直流成分と信号成
分(パルス成分)とについてそれぞれ帰還制御を行い,
出力光信号の平均光パワーと消光比といずれも補償す
る。具体的には,モニタ用受光素子(PD)61から出
力されたモニタ信号は,増幅回路62,積分回路63
と,ピークホールド回路64とに入力される。ここで,
積分回路63は,モニタ信号から出力光信号の平均値を
抽出する。一方,ピークホールド回路は,モニタ用受光
素子61に交流的に結合されており,モニタ信号の信号
振幅を抽出する。従って,ピークホールド回路64が抽
出した信号振幅を一定にするように,レーザダイオード
駆動回路65の駆動電流に,減算回路66,比較器6
7,68を介して負帰還をかけて,出力光信号の信号振
幅を安定化させる。Next, the prior art 2 will be described. FIG.
FIG. 2 is a diagram showing an optical output compensation circuit proposed in the prior art 2. As shown in FIG. 8, the optical output compensation circuit performs feedback control on the DC component and the signal component (pulse component) of the monitor signal extracted from the output optical signal of the LD, respectively.
Both the average optical power and the extinction ratio of the output optical signal are compensated. Specifically, the monitor signal output from the monitor light receiving element (PD) 61 is
And the peak hold circuit 64. here,
The integration circuit 63 extracts the average value of the output optical signal from the monitor signal. On the other hand, the peak hold circuit is AC-coupled to the monitoring light receiving element 61 and extracts the signal amplitude of the monitoring signal. Therefore, the subtraction circuit 66 and the comparator 6 are added to the drive current of the laser diode drive circuit 65 so that the signal amplitude extracted by the peak hold circuit 64 is constant.
Negative feedback is applied via 7, 68 to stabilize the signal amplitude of the output optical signal.
【0008】[0008]
【発明が解決しようとする課題】従来の技術において,
一定のパルス変調電流Ipで変調を行う場合,LDの微
分効率が悪化すると消光比も悪化し,「1」レベル信号
送信時と「0」レベル信号送信時との差が小さくなるの
で,温度変動や経年変化によりLDの劣化が生じた場
合,LDの消光比が悪化しデータ通信の信頼性が落ちる
ことが問題であった。即ち,エラーレートが上昇するこ
とである。ここで,消光比とは2値信号のそれぞれに対
応した2種の光強度の比である。SUMMARY OF THE INVENTION In the prior art,
When the modulation is performed with a constant pulse modulation current Ip, the extinction ratio also deteriorates when the differential efficiency of the LD deteriorates, and the difference between when the "1" level signal is transmitted and when the "0" level signal is transmitted becomes small, so that the temperature fluctuation In the case where the LD is deteriorated due to aging or deterioration over time, the extinction ratio of the LD deteriorates and the reliability of data communication decreases. That is, the error rate increases. Here, the extinction ratio is a ratio of two types of light intensity corresponding to each of the binary signals.
【0009】また,従来技術1において,上記問題点を
回避するためには,一定時間毎にバイアス電流Ibを2
点以上変化させ,しきい値電流,微分効率の変化を検出
して,しきい値電流,パルス変調電流Ipを制御する必
要がある。というのは,LDの劣化モードとして長時間
のレーザ発振による遅い劣化と発光素子の欠陥または過
電流,高温通電等の外的要因による急速劣化がある。一
定時間(電源のON時,一定周期,システムエラー発生
時等)でのみパルス変調電流Ipの制御を行うと,LD
の劣化が急速に進んだ場合に,消光比を一定に保持する
ことができなくなるためである。In the prior art 1, in order to avoid the above problem, the bias current Ib is set to 2
It is necessary to control the threshold current and the pulse modulation current Ip by changing the threshold current and the differential efficiency by changing the threshold current and the differential efficiency. This is because, as the degradation modes of the LD, there are slow degradation due to long-time laser oscillation and rapid degradation due to defects in the light emitting element or external factors such as overcurrent and high-temperature energization. If the pulse modulation current Ip is controlled only for a certain period of time (when the power is turned on, at a certain period, when a system error occurs, etc.), the LD
This is because when the deterioration of the chromium rapidly progresses, the extinction ratio cannot be kept constant.
【0010】また,従来技術2では,上記問題点を回避
するために,負帰還回路により消光比の安定を実現して
いる。しかしながら,周波数帯域の広い増幅器及び高速
応答性の良い受光素子が必要となり,また帰還回路は回
路が複雑となりハード量が増加するという欠点を有し
た。In prior art 2, in order to avoid the above problem, the extinction ratio is stabilized by a negative feedback circuit. However, an amplifier having a wide frequency band and a light-receiving element having good high-speed response are required, and the feedback circuit has a disadvantage that the circuit becomes complicated and the amount of hardware increases.
【0011】そこで,本発明の一技術的課題は,デュー
ティ(duty)比の異なる2種類の試験信号のモニタ出力の
差分を監視しパルス変調電流Ipを制御することで,L
Dの劣化により微分効率が変化した場合でも一定の消光
比を保つことができる光出力レベル制御方法と制御装置
とを提供することにある。Therefore, one technical problem of the present invention is to monitor the difference between the monitor outputs of two types of test signals having different duty ratios and control the pulse modulation current Ip, thereby achieving L
An object of the present invention is to provide a light output level control method and a control device capable of maintaining a constant extinction ratio even when the differential efficiency changes due to deterioration of D.
【0012】また,本発明のもう一つの技術的課題は,
バイアス電流Ibの変化を常に監視することにより,急
速なLDの劣化にも対応することができる光出力レベル
制御方法と制御装置とを提供することにある。Another technical problem of the present invention is that
An object of the present invention is to provide a light output level control method and a control device capable of coping with rapid LD deterioration by constantly monitoring a change in the bias current Ib.
【0013】[0013]
【課題を解決するための手段】本発明によれば,バイア
ス電流Ibにパルス変調電流Ipを重畳させる方式のレ
ーザダイオード(以下,LDと呼ぶ)の駆動方法におい
て,デューティ(duty)比が互いに異なる第1及び第2の
試験信号を用い前記LDの光出力をモニタし,モニタ出
力信号の平均値を検出し,その平均値を記憶し,前記第
1及び第2の試験信号の平均値の差分と,前記LDの初
期状態でのモニタ出力平均値とLD発振後のモニタ出力
平均値の差分をとり,前記バイアス電流Ibの変化を監
視しながら,当該差分に応じてパルス変調電流Ipを制
御することを特徴とする光出力レベル制御方法が得られ
る。According to the present invention, in a method of driving a laser diode (hereinafter referred to as an LD) in which a pulse modulation current Ip is superimposed on a bias current Ib, duty ratios are different from each other. The optical output of the LD is monitored using the first and second test signals, the average value of the monitor output signals is detected, the average value is stored, and the difference between the average values of the first and second test signals is detected. And the difference between the monitor output average value in the initial state of the LD and the monitor output average value after the oscillation of the LD is taken, and while monitoring the change in the bias current Ib, the pulse modulation current Ip is controlled in accordance with the difference. Thus, a light output level control method is obtained.
【0014】また,本発明によれば,前記光出力レベル
制御方法において,前記バイアス電流Ibの変化を経時
的に監視し,前記バイアス電流Ibの変化が短時間で進
行している場合に,LD劣化進行信号を出力することを
特徴とする光出力レベル制御方法が得られる。Further, according to the present invention, in the optical output level control method, a change in the bias current Ib is monitored with time, and when the change in the bias current Ib progresses in a short time, the LD is controlled. An optical output level control method characterized by outputting a deterioration progress signal is obtained.
【0015】また,本発明によれば,バイアス電流Ib
にパルス変調電流Ipを重畳させる方式のレーザダイオ
ード(以下,LDと呼ぶ)の駆動回路において,デュー
ティ(duty)比が互いに異なる第1及び第2の試験信号を
用い前記LDの光出力をモニタするためのモニタ用受光
素子と,前記モニタ用受光素子のモニタ出力信号の平均
値を検出する平均値検出回路と,前記平均値検出回路の
出力を記憶し,前記第1及び第2の試験信号の平均値の
差分と,LDの初期状態でのモニタ出力平均値とLD発
振後のモニタ出力平均値の差分をとる記憶差分演算回路
と,前記バイアス電流Ibの変化を監視するバイアス電
流監視回路と,前記記憶差分演算回路の出力に応じてパ
ルス変調電流を制御するパルス変調制御回路を有するこ
とを特徴とする光出力レベル制御装置が得られる。According to the present invention, the bias current Ib
In a drive circuit of a laser diode (hereinafter, referred to as an LD) of a type in which a pulse modulation current Ip is superimposed on a pulse, a light output of the LD is monitored using first and second test signals having different duty ratios. Light-receiving element for monitoring, an average value detection circuit for detecting an average value of a monitor output signal of the monitor light-receiving element, and an output of the average value detection circuit, and storing the output of the first and second test signals. A storage difference calculation circuit for calculating a difference between the average value, a difference between the monitor output average value in the initial state of the LD and the monitor output average value after LD oscillation, a bias current monitoring circuit for monitoring a change in the bias current Ib, An optical output level control device comprising a pulse modulation control circuit for controlling a pulse modulation current according to the output of the storage difference calculation circuit is obtained.
【0016】さらに,本発明によれば,前記光出力レベ
ル制御装置において,前記バイアス電流Ibの変化を監
視するバイアス電流監視回路内にタイマ回路を設け,前
記バイアス電流Ibの変化が短時間で進行している場合
に,LD劣化進行信号を出力することを特徴とする光出
力レベル制御装置が得られる。Further, according to the present invention, in the optical output level control device, a timer circuit is provided in a bias current monitoring circuit for monitoring a change in the bias current Ib, and the change in the bias current Ib progresses in a short time. In such a case, an optical output level control device characterized by outputting an LD deterioration progress signal is obtained.
【0017】[0017]
【発明の実施の形態】以下,本発明の実施の形態につい
て図面を参照して説明する。Embodiments of the present invention will be described below with reference to the drawings.
【0018】(第1の実施の形態)図1は本発明の第1
の実施の形態による光出力レベル制御装置の構成を示す
ブロック図である。図1に示すように,光出力レベル制
御装置は,LD駆動回路1及びLDモジュール2とを備
えている。(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of an optical output level control device according to an embodiment. As shown in FIG. 1, the optical output level control device includes an LD drive circuit 1 and an LD module 2.
【0019】LD駆動回路1は,モード選択回路3,平
均値検出回路4,記憶差分演算回路5,パルス変調制御
回路6,バイアス制御回路7,切替回路8,バイアス回
路9,バイアス電流監視回路10,及びパルス変調回路
11を備えている。また,LDモジュール2は,その中
に,LD素子12とLD素子12の光出力モニタするた
めのモニタ用受光素子13を備えている。The LD drive circuit 1 includes a mode selection circuit 3, an average value detection circuit 4, a storage difference calculation circuit 5, a pulse modulation control circuit 6, a bias control circuit 7, a switching circuit 8, a bias circuit 9, a bias current monitoring circuit 10 , And a pulse modulation circuit 11. The LD module 2 further includes an LD element 12 and a monitoring light receiving element 13 for monitoring the optical output of the LD element 12.
【0020】LD駆動回路1において,モード選択回路
3は,LD駆動回路1を通常動作モード又はLDの消光
比を制御する試験モードのいづれかに設定する回路であ
る。平均値検出回路4は,デューティ(duty)比の異なる
2種類の試験信号,即ち,第1及び第2の試験信号のモ
ニタ用受光素子13のモニタ出力によりLD素子12の
平均光出力を検出する回路である。In the LD drive circuit 1, the mode selection circuit 3 is a circuit for setting the LD drive circuit 1 to either a normal operation mode or a test mode for controlling the extinction ratio of the LD. The average value detection circuit 4 detects the average light output of the LD element 12 based on two types of test signals having different duty ratios, that is, the monitor output of the monitoring light receiving element 13 of the first and second test signals. Circuit.
【0021】記憶差分演算回路5は,初期状態でのデュ
ーティ(duty)比の異なる第1及び第2の試験信号の平均
値検出回路4の出力を記憶し,その差分を取る回路であ
る。また,記憶差分演算回路5では初期状態での試験信
号の平均光出力とLDの劣化が進んだ後の試験信号の平
均光出力との差分も取る。The storage difference calculation circuit 5 is a circuit that stores the output of the average value detection circuit 4 of the first and second test signals having different duty ratios in the initial state and takes the difference. The storage difference calculation circuit 5 also calculates the difference between the average optical output of the test signal in the initial state and the average optical output of the test signal after the deterioration of the LD has progressed.
【0022】パルス変調制御回路6は,記憶差分演算回
路5の差分結果が初期値に対し変動した場合,パルス変
調電流Ipを制御する回路である。The pulse modulation control circuit 6 is a circuit for controlling the pulse modulation current Ip when the difference result of the storage difference calculation circuit 5 fluctuates from the initial value.
【0023】バイアス制御回路7は,平均値検出回路4
の出力をもとに光出力の平均値が一定となる様にバイア
ス電流Ibの値を制御する回路である。The bias control circuit 7 includes an average value detection circuit 4
Is a circuit for controlling the value of the bias current Ib so that the average value of the optical output becomes constant based on the output of the bias current Ib.
【0024】切替回路8は,平均値検出回路4の出力を
バイアス制御回路7又は記憶差分演算回路5のいずれか
にモード選択回路3の設定に応じて切り替える回路であ
る。バイアス回路9は,LD素子12にバイアス電流I
bを流す回路である。The switching circuit 8 switches the output of the average value detection circuit 4 to either the bias control circuit 7 or the storage difference calculation circuit 5 according to the setting of the mode selection circuit 3. The bias circuit 9 supplies a bias current I to the LD element 12.
b.
【0025】また,バイアス電流監視回路10は,バイ
アス電流Ibの変化量を監視し,変動が生じた場合に上
位回路に劣化信号を出力する回路である。The bias current monitoring circuit 10 is a circuit that monitors the amount of change in the bias current Ib and outputs a deterioration signal to a higher-level circuit when a change occurs.
【0026】さらに,パルス変調回路11は,LD素子
12にバイアス電流Ibにパルス変調電流Ipを重畳さ
せて流すことによりLD素子12をパルス駆動する回路
である。Further, the pulse modulation circuit 11 is a circuit for pulse-driving the LD element 12 by superimposing and flowing the pulse modulation current Ip on the bias current Ib to the LD element 12.
【0027】始めに,通常のデータ転送を始める前,即
ちLDの初期状態において,上位回路からのモード切替
信号によりLD駆動回路1を試験モードに設定する。試
験モードでは2種類のデューティ(duty)比の異なる試験
信号(第1及び第2の試験信号)を上位回路より送信デ
ータとしてLD駆動回路1に入力する。試験信号Aはデ
ューティ(duty)比6対4の信号であり,試験信号Bは,
duty比4対6の信号である。First, before starting the normal data transfer, that is, in the initial state of the LD, the LD drive circuit 1 is set to the test mode by the mode switching signal from the upper circuit. In the test mode, two types of test signals (first and second test signals) having different duty ratios are input to the LD drive circuit 1 as transmission data from the host circuit. The test signal A is a signal having a duty ratio of 6 to 4, and the test signal B is
This is a signal with a duty ratio of 4 to 6.
【0028】本発明の第1の実施の形態による光出力レ
ベル制御装置の動作について説明する。The operation of the optical output level control device according to the first embodiment of the present invention will be described.
【0029】通常動作を開始する前に,上位回路よりモ
ード選択回路3を試験モードに設定する。試験モードで
は,送信データとしてデューティ(duty)比の異なる2種
類の試験信号AとBを上位回路から出力する。その際の
モニタ用受光素子13の出力を記憶差分演算回路5に入
力する。試験信号AとBは,デューティ(duty)比が異な
るためLD12の光出力レべルが異なり,モニタ出力も
異なる。記憶差分演算回路5では,モニタ出力PA とP
B の差ΔP=PA −PB を取りその結果を記憶する。L
D12は,長時間発振することにより劣化が進み,光出
力ーバイアス電流特性の傾き(微分効率η)が悪化す
る。このためバイアス電流Ibの制御のみでは消光比が
悪化する。これを防ぐため,LDの劣化は徐々に進行す
るという性質を用いて,数ケ月に1度程度の定期的に試
験信号を送信し差分を取って,その値が記憶差分演算回
路5で記憶されている初期値に対して変動した場合,パ
ルス変調制御回路6でパルス変調電流Ipを制御し消光
比を一定に保つ。Before starting the normal operation, the mode selection circuit 3 is set to the test mode by the host circuit. In the test mode, two types of test signals A and B having different duty ratios are output from the upper circuit as transmission data. The output of the monitoring light receiving element 13 at that time is input to the storage difference calculation circuit 5. Since the test signals A and B have different duty ratios, the light output level of the LD 12 is different and the monitor output is also different. In the storage difference calculation circuit 5, the monitor outputs PA and P
Take the difference .DELTA.P = PA-PB of B and store the result. L
D12 deteriorates due to oscillation for a long time, and the gradient (differential efficiency η) of the optical output-bias current characteristic deteriorates. Therefore, the extinction ratio is deteriorated only by controlling the bias current Ib. To prevent this, the test signal is transmitted periodically about once every several months by taking advantage of the property that the LD deterioration gradually progresses, and the difference is stored in the storage difference calculation circuit 5. If the initial value fluctuates, the pulse modulation control circuit 6 controls the pulse modulation current Ip to keep the extinction ratio constant.
【0030】即ち,記憶差分演算回路5での差が初期値
より小さくなった場合は,微分効率ηが悪化しているた
め,パルス変調電流Ipを増加させる。逆に差が大きく
なっている場合はパルス変調電流Ipを減少させる。パ
ルス変調電流Ipを制御することにより,微分効率ηが
悪化しても消光比を一定に保てる。That is, when the difference in the storage difference calculation circuit 5 becomes smaller than the initial value, the pulse modulation current Ip is increased because the differential efficiency η has deteriorated. Conversely, when the difference is large, the pulse modulation current Ip is reduced. By controlling the pulse modulation current Ip, the extinction ratio can be kept constant even if the differential efficiency η deteriorates.
【0031】また,バイアス電流監視回路でバイアス電
流Ibの変化を常に監視し,バイアス電流Ibが大幅に
増加した場合は急速にLD12の劣化が進んだと判断
し,同様にパルス電流Ipを制御する。The bias current monitoring circuit constantly monitors the change in the bias current Ib. If the bias current Ib increases significantly, it is determined that the deterioration of the LD 12 has rapidly progressed, and the pulse current Ip is similarly controlled. .
【0032】次に,本発明の第1の実施の形態による光
出力レベル制御装置について,図1に更に図2乃至図4
を用いて具体的に説明する。Next, an optical output level control device according to a first embodiment of the present invention will be described with reference to FIGS.
This will be specifically described with reference to FIG.
【0033】図2は一般のLDの初期状態での光出力−
電流特性を示すグラフである。図2に示すように,一般
にLDをパルス駆動する場合,バイアス電流Ibをしき
い値電流Ithより多少大きめな値に設定し,そこにパ
ルス変調電流Ipを重畳する。FIG. 2 shows the light output in the initial state of a general LD.
4 is a graph showing current characteristics. As shown in FIG. 2, when the LD is generally pulse-driven, the bias current Ib is set to a value slightly larger than the threshold current Ith, and the pulse modulation current Ip is superimposed thereon.
【0034】LD駆動回路1に入力された試験信号はパ
ルス変調回路12にて,図2に示す様にパルス変調電流
Ipが出力されLD素子12に流れることによりパルス
発光する。この際の,LD素子12の光出力をモニタ用
受光素子13にてモニタし平均値検出回路4に出力す
る。The test signal input to the LD drive circuit 1 is pulsed by the pulse modulation circuit 12 outputting a pulse modulation current Ip and flowing through the LD element 12 as shown in FIG. At this time, the light output of the LD element 12 is monitored by the monitoring light receiving element 13 and output to the average value detection circuit 4.
【0035】平均値検出回路4では光出力の平均値を検
出する。試験信号Aの光出力平均値(PA1),試験信号
Bの光出力平均値を(PB2)をそれぞれ記憶差分演算回
路5に出力する。試験信号Aと試験信号Bはデューティ
(duty)比が異なるため光出力レベルも異なる。平均値検
出回路4の出力PA1とPB1との間には,以下の数1式で
示される関係が成りたつ。The average value detection circuit 4 detects the average value of the light output. The average optical output value (P A1 ) of the test signal A and the average optical output value (P B2 ) of the test signal B are output to the storage difference calculation circuit 5, respectively. Test signal A and test signal B are duty
Since the (duty) ratio is different, the light output level is also different. The following equation 1 holds between the outputs P A1 and P B1 of the average value detection circuit 4.
【0036】[0036]
【数1】 記憶差分演算回路5では,PA1とPA2の差分(ΔP11)
を計算し,その値を記憶する。差分は次の数2式で表さ
れる。(Equation 1) In the storage difference calculation circuit 5, the difference between P A1 and P A2 (ΔP 11 )
Is calculated and the value is stored. The difference is represented by the following equation (2).
【0037】[0037]
【数2】 電気信号を光信号に変換する効率である微分効率ηは,
次の数3式で示されるように,光出力−電流特性のグラ
フの傾きで表される。(Equation 2) The differential efficiency η, which is the efficiency of converting an electrical signal to an optical signal, is
As shown by the following equation (3), it is represented by the slope of the graph of the light output-current characteristic.
【0038】[0038]
【数3】 以上,説明したように,LDの初期状態での試験信号A
とBの光出力平均値PA1とPB2を平均値検出回路4で検
出し,その差分ΔP11を記憶差分演算回路5で記憶した
後に,モード選択回路3を通常モードに設定し通常動作
を開始する。(Equation 3) As described above, the test signal A in the initial state of the LD
The average values P A1 and P B2 of the optical outputs B and B are detected by the average value detection circuit 4 and the difference ΔP 11 is stored in the storage difference calculation circuit 5, and then the mode selection circuit 3 is set to the normal mode to perform the normal operation. Start.
【0039】ここで,通常動作状態では,従来の平均光
出力検出による自動光出力制御回路(APC)方式と同
様であり,平均値検出回路4の出力は切替回路8でバイ
アス制御回路7へ入力される。バイアス制御回路7で
は,通常動作中も常時光出力をモニタしその平均値が一
定となるようにバイアス電流Ibを制御する。しかし,
パルス変調電流Ipは初期値のまま一定である。Here, in a normal operation state, the output of the average value detection circuit 4 is input to the bias control circuit 7 by the switching circuit 8 in the same manner as in the conventional automatic light output control circuit (APC) system using the average light output detection. Is done. The bias control circuit 7 constantly monitors the optical output even during the normal operation, and controls the bias current Ib so that the average value is constant. However,
The pulse modulation current Ip is constant at the initial value.
【0040】また,LDの劣化モードとして遅い劣化と
急速劣化の2種類がある。前者の遅い劣化とは,通常の
動作状態で長時間レーザ発振することにより進む劣化で
ある。一方,後者の急速劣化とは,発光素子の欠陥及び
過電流,高温通電等の外的要因により急激に進む劣化で
ある。LDの劣化が進むと微分効率ηが変化する。この
様子を図3に示す。There are two types of LD degradation modes, slow degradation and rapid degradation. The former slow deterioration is deterioration that progresses due to laser oscillation for a long time in a normal operation state. On the other hand, the latter rapid deterioration is deterioration that progresses rapidly due to external factors such as defects of the light emitting element, overcurrent, high-temperature energization, and the like. As the LD deteriorates, the differential efficiency η changes. This is shown in FIG.
【0041】図2に示した初期状態と同一のパルス変調
電流Ipでは,微分効率ηは以下の数4式及び数5式の
様になる。At the same pulse modulation current Ip as the initial state shown in FIG. 2, the differential efficiency η is as shown in the following equations (4) and (5).
【0042】[0042]
【数4】 (Equation 4)
【0043】[0043]
【数5】 上記数4式及び数5式に示されるように,従来のバイア
ス電流Ibの制御のみでは,消光比が悪化しデータ転送
の信頼性が低下する。(Equation 5) As shown in the above equations (4) and (5), only the conventional control of the bias current Ib deteriorates the extinction ratio and lowers the reliability of data transfer.
【0044】これを防ぐために,本発明の第1の実施の
形態においては,定期的(数ヶ月に1度程度)にLD駆
動回路1を試験モードに設定し上位回路より試験信号を
送信して,その際の平均値光出力の差分を取り,記憶差
分演算回路5に記憶してある初期値に対し,変動が生じ
た場合にパルス変調制御回路6でパルス電流Ipを制御
して消光比を一定とする。In order to prevent this, in the first embodiment of the present invention, the LD drive circuit 1 is set to the test mode periodically (about once every several months), and a test signal is transmitted from the upper circuit. The difference of the average light output at that time is obtained, and when a fluctuation occurs with respect to the initial value stored in the storage difference calculating circuit 5, the pulse modulation control circuit 6 controls the pulse current Ip to change the extinction ratio. To be constant.
【0045】初期状態の時と同様に試験信号A送信時の
平均値検出回路6の出力PA2と試験信号B送信時の平均
値検出回路の出力PB2間の差分を記憶差分演算回路5で
取りさらに,初期状態での値ΔP11との差分を取る。微
分効率ηが悪化しているため次の数6式及び数7式の様
になる。As in the initial state, the difference between the output P A2 of the average value detection circuit 6 when the test signal A is transmitted and the output P B2 of the average value detection circuit when the test signal B is transmitted is stored in the storage difference calculation circuit 5. Further, a difference from the value ΔP 11 in the initial state is obtained. Since the differential efficiency η is deteriorated, the following equations (6) and (7) are obtained.
【0046】[0046]
【数6】 (Equation 6)
【0047】[0047]
【数7】 パルス変調制御回路6では,ΔP11>ΔP22と初期値に
対し変動したため,これが一定となるようパルス変調電
流Ipを増加させる。(Equation 7) The pulse modulation control circuit 6 increases the pulse modulation current Ip such that ΔP 11 > ΔP 22 , which has fluctuated from the initial value, becomes constant.
【0048】以上の動作が終了した後は,通常動作モー
ドに設定する。通常動作モードでは光出力平均値検出に
よるバイアス電流Ibの制御を行うのみで,パルス変調
電流Ipの制御は行わない。これにより,光出力レベル
と消光比を一定に保持することができる。この様子を図
4に示す。After the above operation is completed, the normal operation mode is set. In the normal operation mode, only the control of the bias current Ib by the detection of the optical output average value is performed, and the control of the pulse modulation current Ip is not performed. Thus, the light output level and the extinction ratio can be kept constant. This is shown in FIG.
【0049】図4に示すように,微分効率ηはη1 >η
2 となっているため,パルス変調電流IpをIp2とし
増加させている。As shown in FIG. 4, the differential efficiency η is η 1 > η
Since it is 2 , the pulse modulation current Ip is increased to Ip2.
【0050】また,急速に劣化が進む場合は,しきい値
電流Ithが大幅に増加するためバイアス電流Ibも増
加する。バイアス電流Ibの変化を,バイアス電流監視
回路10で監視し,バイアス電流Ibが初期値に対し増
加(例えば1.3倍)した場合は,LDが急速に劣化し
たものと判断して上位回路にLD劣化信号を出力する。
上位回路はこの信号を受けてLD駆動回路1を試験モー
ドに設定して,前述したように,パルス変調電流Ipを
制御してLDの急速劣化に対応して消光比を一定に保
つ。When the deterioration progresses rapidly, the bias current Ib also increases because the threshold current Ith greatly increases. The change in the bias current Ib is monitored by the bias current monitoring circuit 10, and if the bias current Ib increases (for example, 1.3 times) from the initial value, it is determined that the LD has rapidly deteriorated and the upper circuit is determined. An LD deterioration signal is output.
The host circuit receives this signal, sets the LD drive circuit 1 to the test mode, and controls the pulse modulation current Ip to keep the extinction ratio constant in response to the rapid deterioration of the LD, as described above.
【0051】また,バイアス電流Ibが初期値に対し2
倍を越えた場合は,LDの不良と判断し不良信号を上位
装置に出力する。Further, the bias current Ib is 2
If it exceeds twice, it is determined that the LD is defective, and a defect signal is output to the host device.
【0052】以上説明したように,本発明の第1の実施
の形態では,デューティ(duty)比の異なる2種類の試験
信号のモニ夕出力を監視することでLDの劣化が徐々に
進んだ場合も,急速に進んだ場合も消光比を一定に保持
できる。As described above, according to the first embodiment of the present invention, the monitoring of the monitor output of two types of test signals having different duty ratios allows the LD to gradually deteriorate. However, the extinction ratio can be kept constant even when the speed advances rapidly.
【0053】(第2の実施の形態)次に,本発明の第2
の実施の形態について説明する。(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described.
【0054】図5は本発明の第2の実施の形態による光
出力レベル制御装置の構成を示すブロック図である。図
5に示すように,第1の実施の形態では,試験モードと
通常動作モードを,モード選択回路3,切替回路8によ
って切り替えているが,第2の実施の形態では,モード
選択回路3及び切替回路8を除去している点で第2の実
施の形態は第1の実施の形態と異なる。FIG. 5 is a block diagram showing a configuration of an optical output level control device according to a second embodiment of the present invention. As shown in FIG. 5, in the first embodiment, the test mode and the normal operation mode are switched by the mode selection circuit 3 and the switching circuit 8, but in the second embodiment, the mode selection circuit 3 and the normal operation mode are switched. The second embodiment differs from the first embodiment in that the switching circuit 8 is eliminated.
【0055】第2の実施の形態による光出力レベル制御
装置においては,第1の実施の実施の形態と同様に消光
比の制御を行う場合は,上位装置よりモード切替信号と
試験信号A及びBがLD駆動回路1に入力される。モー
ド切替信号は記憶差分演算回路9とパルス変調制御回路
12のイネーブル信号として使われる。モード切替信号
がイネーブル{例えば,ハイ(HI)レベル}の場合に
試験信号AとBが送信され,記憶差分演算回路5は,第
1の実施の形態の場合と同様に,2種類の試験信号間の
差分を取り,初期値に対し変動があった場合にパルス変
調制御回路6でパルス変調電流Ipを制御する。In the optical output level control device according to the second embodiment, when controlling the extinction ratio in the same manner as in the first embodiment, the mode switching signal and the test signals A and B are transmitted from the host device. Is input to the LD drive circuit 1. The mode switching signal is used as an enable signal for the storage difference calculation circuit 9 and the pulse modulation control circuit 12. When the mode switching signal is enabled {for example, high (HI) level}, the test signals A and B are transmitted, and the storage difference calculation circuit 5 performs two types of test signals as in the case of the first embodiment. The pulse modulation current Ip is controlled by the pulse modulation control circuit 6 when the difference between the initial values is obtained.
【0056】通常の動作状態では,モード切替信号は,
ロウ(LO)レベルであり,記憶差分演算回路5とパル
ス変調制御回路6は動作せず,バイアス電流Ibの制御
のみを行う。In a normal operation state, the mode switching signal is
At the low (LO) level, the storage difference calculation circuit 5 and the pulse modulation control circuit 6 do not operate, but only control the bias current Ib.
【0057】第2の実施の形態においては,試験信号と
してデューティ(duty)比が6対4と4対6の信号を使っ
ているが,これは2種類試験信号間でモニタ用受光素子
13の出力の平均値に違いが出るものであればデューテ
ィ(duty)比は幾つでも良い。In the second embodiment, a signal having a duty ratio of 6: 4 and 4: 6 is used as a test signal. Any number of duty ratios may be used as long as the output average value differs.
【0058】(第3の実施の形態)次に,本発明の第3
の実施の形態について説明する。図6は本発明の第3の
実施の形態による光出力レベル制御装置の構成をに示す
図である。図6に示すように,本発明の第3の実施の形
態によるものは,バイアス電流監視回路10にタイマ回
路14を内蔵する他は,第2の実施の形態によるものと
同様の構成を有している。このタイマ回路14は,バイ
アス電流の変化する時間を計測する。(Third Embodiment) Next, a third embodiment of the present invention will be described.
An embodiment will be described. FIG. 6 is a diagram showing a configuration of an optical output level control device according to a third embodiment of the present invention. As shown in FIG. 6, the third embodiment of the present invention has the same configuration as that of the second embodiment except that a timer circuit 14 is built in the bias current monitoring circuit 10. ing. This timer circuit 14 measures the time when the bias current changes.
【0059】ここで,LDは,劣化が進むことにより,
しきい値電流Ithが増加し,最終的には光出力レベル
が低下し使用できなくなる。しかし,バイアス電流監視
回路10内にタイマ回路14を設けることにより,バイ
アス電流Ibの増加が短時間で進行している場合は,劣
化進行信号を上位装置に出力しLDの劣化が急速に進ん
でいることを通知するので,事前に劣化を知り,その対
策を早目に行うことができる。Here, as the deterioration of the LD progresses,
The threshold current Ith increases, and finally the light output level decreases and becomes unusable. However, by providing the timer circuit 14 in the bias current monitoring circuit 10, when the increase of the bias current Ib is progressing in a short time, the deterioration progress signal is output to the host device, and the deterioration of the LD rapidly progresses. Notification of deterioration, the deterioration can be known in advance, and the countermeasure can be taken at an early stage.
【0060】[0060]
【発明の効果】以上,説明したように,本発明によれ
ば,デューティ(duty)比の異なる第1及び第2の試験信
号のモニタ出力の差分を監視し,消光比が一定となるよ
うパルス変調電流Ipを制御するために,温度変動,経
年変化等によりLDの特性が悪化した場合でも消光比を
一定の値に保持できる光出力レベル制御方法及び装置を
提供することができる。As described above, according to the present invention, the difference between the monitor outputs of the first and second test signals having different duty ratios is monitored, and the pulse is controlled so that the extinction ratio becomes constant. In order to control the modulation current Ip, it is possible to provide an optical output level control method and apparatus capable of maintaining the extinction ratio at a constant value even when the characteristics of the LD deteriorate due to temperature fluctuation, aging, and the like.
【0061】また,本発明によれば,バイアス電流監視
回路でバイアス電流Ibの変化を監視してバイアス電流
Ibが初期値に対し変動した場合に劣化信号を出力し
て,パルス変調電流Ipを制御する試験モードに設定す
るので,LDの劣化が急速に進んだ場合もパルス変調電
流Ipの値を制御して消光比を一定に保持できる光出力
レベル制御方法及び装置を提供することができる。According to the present invention, the bias current monitoring circuit monitors a change in the bias current Ib and outputs a deterioration signal when the bias current Ib fluctuates from the initial value to control the pulse modulation current Ip. Since the test mode is set to the test mode, even when the LD deteriorates rapidly, it is possible to provide an optical output level control method and apparatus capable of controlling the value of the pulse modulation current Ip and keeping the extinction ratio constant.
【0062】また,本発明によれば,バイアス電流監視
回路に,更に,タイマ回路を設けることによって,バイ
アス電流Ibの変化する時間を計測し短時間でバイアス
電流Ibが増加している場合は上位回路に劣化進行信号
を出力するので,LDの劣化が急速に進行していること
を事前に把握できる光出力レベル制御方法及び装置を提
供することができる。Further, according to the present invention, by providing a timer circuit in the bias current monitoring circuit, the time during which the bias current Ib changes is measured. Since the deterioration progress signal is output to the circuit, it is possible to provide an optical output level control method and apparatus capable of grasping in advance that the deterioration of the LD is rapidly progressing.
【0063】また,本発明によれば,帰還回路による光
出力のピーク値検出を行わないため,高速の受光素子,
増幅器の必要が無いために,従来技術によるもの(例え
ば,従来技術2)よりも回路構成が簡易になり,汎用の
部品が使用できる光出力レベル制御方法及び装置を提供
することができる。Further, according to the present invention, since the peak value of the optical output is not detected by the feedback circuit, a high-speed light-receiving element
Since there is no need for an amplifier, the circuit configuration is simpler than that of the prior art (for example, Conventional Technique 2), and an optical output level control method and apparatus that can use general-purpose components can be provided.
【図1】本発明の第1の実施の形態による光出力レベル
制御装置の構成を示すブロック図である。FIG. 1 is a block diagram illustrating a configuration of an optical output level control device according to a first embodiment of the present invention.
【図2】一般のLDの初期状態の電流−光出力特性図で
ある。FIG. 2 is a current-light output characteristic diagram of a general LD in an initial state.
【図3】LD劣化状態の電流−光出力特性図である。FIG. 3 is a current-light output characteristic diagram in an LD degraded state.
【図4】本発明の第1の実施の形態による光出力レベル
制御装置の動作を説明するための図であり,変調電流の
変化を示している。FIG. 4 is a diagram for explaining an operation of the optical output level control device according to the first embodiment of the present invention, and shows a change in modulation current.
【図5】本発明の第2の実施の形態による光出力レベル
制御装置の構成を示すブロック図である。FIG. 5 is a block diagram showing a configuration of an optical output level control device according to a second embodiment of the present invention.
【図6】本発明の第3の実施の形態による光出力レベル
制御装置の構成を示すブロック図である。FIG. 6 is a block diagram illustrating a configuration of an optical output level control device according to a third embodiment of the present invention.
【図7】従来技術1を示すブロック図である。FIG. 7 is a block diagram showing Conventional Technique 1.
【図8】従来技術2を示す回路図である。FIG. 8 is a circuit diagram showing a conventional technique 2.
1 LD駆動回路 2 LDモジュール 3 モード選択回路 4 平均値検出回路 5 記憶差分演算回路 6 パルス変調制御回路 7 バイアス制御回路 8 切替回路 9 バイアス回路 10 バイアス電流監視回路 11 パルス変調回路 12 LD素子 13 受光素子 14 タイマ回路 REFERENCE SIGNS LIST 1 LD drive circuit 2 LD module 3 mode selection circuit 4 average value detection circuit 5 storage difference calculation circuit 6 pulse modulation control circuit 7 bias control circuit 8 switching circuit 9 bias circuit 10 bias current monitoring circuit 11 pulse modulation circuit 12 LD element 13 light receiving Element 14 Timer circuit
Claims (4)
せる方式のレーザダイオード(以下,LDと呼ぶ)の駆
動方法において,デューティ(duty)比が互いに異なる第
1及び第2の試験信号を用いLDの光出力をモニタし,
モニタ出力信号の平均値を検出し,その平均値を記憶
し,前記第1及び第2の試験信号の平均値の差分と,L
Dの初期状態でのモニタ出力平均値とLD発振後のモニ
タ出力平均値の差分をとり,前記バイアス電流の変化を
監視しながら,当該差分に応じてパルス変調電流を制御
することを特徴とする光出力レベル制御方法。In a method of driving a laser diode (hereinafter, referred to as an LD) of a type in which a pulse modulation current is superimposed on a bias current, the LD is driven by using first and second test signals having different duty ratios. Monitor light output,
The average value of the monitor output signal is detected, the average value is stored, and the difference between the average value of the first and second test signals and L
A difference between a monitor output average value in an initial state of D and a monitor output average value after LD oscillation is obtained, and a pulse modulation current is controlled according to the difference while monitoring a change in the bias current. Light output level control method.
おいて,前記バイアス電流の変化を経時的に監視し,前
記バイアス電流の変化が短時間で進行している場合に,
LD劣化進行信号を出力することを特徴とする光出力レ
ベル制御方法。2. The optical output level control method according to claim 1, wherein the change in the bias current is monitored with time, and when the change in the bias current progresses in a short time,
An optical output level control method, comprising: outputting an LD deterioration progress signal.
せる方式のレーザダイオード(以下,LDと呼ぶ)の駆
動回路において,デューティ(duty)比の互いに異なる第
1及び第2の試験信号を用いLDの光出力をモニタする
ためのモニタ用受光素子と,前記モニタ用受光素子のモ
ニタ出力信号の平均値を検出する平均値検出回路と,前
記平均値検出回路の出力を記憶し,前記第1及び第2の
試験信号の平均値の差分と,LDの初期状態でのモニタ
出力平均値とLD発振後のモニタ出力平均値の差分をと
る記憶差分演算回路と,前記バイアス電流の変化を監視
するバイアス電流監視回路と,前記記憶差分演算回路の
出力に応じてパルス変調電流を制御するパルス変調制御
回路を有することを特徴とする光出力レベル制御装置。3. A driving circuit for a laser diode (hereinafter, referred to as an LD) of a system in which a pulse modulation current is superimposed on a bias current, the first and second test signals having different duty ratios are used for the LD. A monitoring light receiving element for monitoring an optical output, an average value detecting circuit for detecting an average value of a monitor output signal of the monitoring light receiving element, and an output of the average value detecting circuit; (2) a storage difference calculation circuit for calculating a difference between the average value of the test signal, a difference between the average value of the monitor output in the initial state of the LD and the average value of the monitor output after the oscillation of the LD, and An optical output level control device comprising: a monitoring circuit; and a pulse modulation control circuit that controls a pulse modulation current according to an output of the storage difference calculation circuit.
おいて,前記バイアス電流の変化を監視するバイアス電
流監視回路内にタイマ回路を設け,前記バイアス電流の
変化が短時間で進行している場合に,LD劣化進行信号
を出力することを特徴とする光出力レベル制御装置。4. The optical output level control device according to claim 3, wherein a timer circuit is provided in a bias current monitoring circuit for monitoring a change in the bias current, and the change in the bias current progresses in a short time. An optical output level control device for outputting an LD deterioration progress signal.
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JP32395896A JP2877209B2 (en) | 1996-12-04 | 1996-12-04 | Optical output level control method and optical output level control device |
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JP32395896A JP2877209B2 (en) | 1996-12-04 | 1996-12-04 | Optical output level control method and optical output level control device |
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JP2877209B2 JP2877209B2 (en) | 1999-03-31 |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2002076506A (en) * | 2000-08-30 | 2002-03-15 | Nec Corp | Method and device for detecting abnormality of optical module |
WO2004010611A1 (en) * | 2002-07-19 | 2004-01-29 | Matsushita Electric Industrial Co., Ltd. | Burst signal extinction ratio control circuit, integrated circuit thereof, burst signal extinction ratio control method, computer program, and laser diode drive circuit |
US6895028B2 (en) | 2001-12-20 | 2005-05-17 | Kabushiki Kaisha Toshiba | Light-emitting element controller, optical transmitting apparatus, and method and computer program for determining driving current |
WO2016152465A1 (en) * | 2015-03-26 | 2016-09-29 | 株式会社小糸製作所 | Vehicular lamp device and lamp device system |
-
1996
- 1996-12-04 JP JP32395896A patent/JP2877209B2/en not_active Expired - Fee Related
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2002076506A (en) * | 2000-08-30 | 2002-03-15 | Nec Corp | Method and device for detecting abnormality of optical module |
US6895028B2 (en) | 2001-12-20 | 2005-05-17 | Kabushiki Kaisha Toshiba | Light-emitting element controller, optical transmitting apparatus, and method and computer program for determining driving current |
WO2004010611A1 (en) * | 2002-07-19 | 2004-01-29 | Matsushita Electric Industrial Co., Ltd. | Burst signal extinction ratio control circuit, integrated circuit thereof, burst signal extinction ratio control method, computer program, and laser diode drive circuit |
WO2016152465A1 (en) * | 2015-03-26 | 2016-09-29 | 株式会社小糸製作所 | Vehicular lamp device and lamp device system |
JPWO2016152465A1 (en) * | 2015-03-26 | 2018-01-18 | 株式会社小糸製作所 | Vehicle lamp and lamp system |
US10531547B2 (en) | 2015-03-26 | 2020-01-07 | Koito Manufacturing Co., Ltd. | Vehicular lighting device |
Also Published As
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JP2877209B2 (en) | 1999-03-31 |
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