1223931 A7 _ B7 五、發明說明（i) 發明領域： 本發明係有關於一種用於光學收發器之自動功率控制 (APC)電路，更明確而言，係關於一種可以克服追蹤比 (Tracking Rati〇)會隨溫度變化之問題而使光學收發器之發 5光強度維持高穩定度的自動功率控制電路。 發明背景： 在光學收發器中，雷射二極體的發光強度對電流的特 性曲線會隨著溫度有所變化，因而影響整個光學收發器在 10不同溫度下發光強度的穩定性。參見圖一，係顯示雷射二 極體的發光強度對電流在不同溫度下的特性曲線，其中顯 不出雷射二極體之臨界電流込對發光強度隨不同溫度變 化的情形。而臨界電流ith直接影響發光效率。由該圖可 知’如果以一固定的偏動電流“心去驅動雷射二極體，則 15在不同溫度下將無法得到一致的發光強度。 為了克服雷射二極體在不同溫度下有不同發光強度的 問題’ 一般的做法是使用負回授的自動功率控制（Apc)電 路’利用光感測器來監控雷射二極體之發光強度，並利用 經濟部智慧財產局員工消費合作社印製 負回授電路調節雷射二極體之偏動電流，以達到控制其發 20 光強度之目的。 圖二係顯示習用之APC電路結構。APC電路係包括 一光感測器11，用以監控雷射二極體15之發光強度。該 光感測器11係將感應到的雷射光能量轉換成光電流。 此光電流Imon即被利用來監控雷射二極體的發光情況。 本纸張尺度適用中國國家標準(〇^4驗（義297公楚）~~ 1223931 A7 ________B7 _ 五、發明說明（2 ) 運算放大器13係與並聯之電阻器R以及電容器c構 成的積分器16連接成負回授電路。一參考電壓vref由非 反相輸入端輸入該運算放大器13。亦即，非反相輸入端電 壓V+的電壓為vref。運算放大器丨3之反相輸入端電壓V_ 5的電壓值為V5lm〇nX Rm〇n。運算放大器13之輸出電壓v。 與非反相輸入端電壓V+、反相輸入端電壓V·之間的關係 可表示成： V0-A(V+.V.) ........................(1) 10 其中A為一常數。當反相輸入端電壓v_被控制成幾乎與 參考電壓vref相等時，光電流係imcn約等於參考電壓v rex 與電阻Rm°n之比值。亦即：Im〇n=Vref/Rm〇n。一般運用上， 係採用固疋的參考電壓Vref，而Rm〇n為一可變電阻，用以 15調整所需要的光電流Im()n。 經濟部智慧財產局員工消費合作社印製 如果雷射的發光強度變小，光感測器u所感應的發 光強度變小，就會將此現象反應在光電流、⑽上，亦即^ 電流Imon變小，因此反相輸入端電壓Vj==ImQnX尺㈤⑽亦隨之 變小。由等式（1)可知，運算放大器的輸出電壓v。會變 20大。而雷射二極體之偏動電流Ibias可表示成：1223931 A7 _ B7 V. Description of the invention (i) Field of the invention: The present invention relates to an automatic power control (APC) circuit for an optical transceiver. More specifically, it relates to a tracking ratio that can overcome the tracking ratio. ) An automatic power control circuit that keeps the light intensity of the optical transceiver to maintain high stability with the problem of temperature change. BACKGROUND OF THE INVENTION In optical transceivers, the characteristic curve of the light-emitting intensity of a laser diode versus the current varies with temperature, thus affecting the stability of the light-emitting intensity of the entire optical transceiver at different temperatures. Refer to Figure 1, which shows the characteristic curve of the laser diode's luminous intensity versus current at different temperatures, where the critical current of the laser diode 込 versus luminous intensity changes with different temperatures. The critical current ith directly affects the luminous efficiency. It can be seen from the figure that 'if the laser diode is driven with a fixed bias current' heart, 15 will not be able to obtain a uniform luminous intensity at different temperatures. In order to overcome the different laser diodes at different temperatures The issue of luminous intensity 'The general method is to use a negative feedback automatic power control (Apc) circuit' to use a light sensor to monitor the luminous intensity of the laser diode, and print it using the consumer property cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs The negative feedback circuit adjusts the bias current of the laser diode to achieve the purpose of controlling its light intensity. Figure 2 shows the conventional APC circuit structure. The APC circuit includes a light sensor 11 for monitoring The luminous intensity of the laser diode 15. The photo sensor 11 converts the induced laser light energy into a photocurrent. This photocurrent Imon is used to monitor the light emission of the laser diode. This paper The scale is applicable to Chinese national standards (0 ^ 4 test (meaning 297)) ~~ 1223931 A7 ________B7 _ V. Description of the invention (2) The operational amplifier 13 is connected to an integrator 16 composed of a resistor R and a capacitor c connected in parallel. Negative feedback circuit. A reference voltage vref is input from the non-inverting input terminal to the operational amplifier 13. That is, the voltage of the non-inverting input terminal voltage V + is vref. The voltage of the inverting input terminal voltage V_5 of the operational amplifier 3 The value is V5lm〇nX Rm〇n. The output voltage v of the operational amplifier 13 and the relationship between the non-inverting input terminal voltage V + and the inverting input terminal voltage V · can be expressed as: V0-A (V + .V.) .............. (1) 10 where A is a constant. When the inverting input terminal voltage v_ is controlled to be almost equal to the reference voltage vref When equal, the photocurrent system imcn is approximately equal to the ratio of the reference voltage v rex to the resistance Rm ° n. That is: Im〇n = Vref / Rm〇n. In general, a fixed reference voltage Vref is used, and Rm〇 n is a variable resistor used to adjust the required photocurrent Im () n. 15 Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. If the laser's luminous intensity becomes smaller, the luminous intensity induced by the light sensor u If it becomes smaller, this phenomenon will be reflected on the photocurrent and ⑽, that is, the current Imon becomes smaller, so the voltage at the inverting input terminal Vj == ImQnX is also smaller. Formula (1) shows that the output voltage v of the operational amplifier 20 becomes large biasing current Ibias of the laser diode may be expressed as.:
Ibias~( V〇-V Be)/Re ..................(2) 其中VBE是驅動雷射二極體的偏壓，對於雙載子電晶體而 -4- 1223931 Α7 Β7 五、發明說明（3) 言，大約為0.7伏特。Re為射極電阻，用以限制偏動電流 Ibias。當運算放大器的輸出電壓V。變大，雷射二極體之偏 動電流Ibias亦變大，因此，使發光強度至原始設定的位 準，從而達到利用負回授調節發光強度，使發光強度維持 5 穩定的目的。 反之，如果雷射二極體的發光強度變大，則感側到的 光電流Imon跟著變大，運算放大器13之反相輸入端之電 壓V_隨之增大，致使運算放大器13之輸出電壓V。減小。 因此，驅動雷射二極體之偏動電流Ibias會因而變小，使雷 10 射二極體之發光強度減弱，以維持原始設定的位準。 光感測器11所接收到的光功率PR與雷射二極體實際 上發出之光功率Pout之間的關係如下：Ibias ~ (V〇-V Be) / Re ........ (2) where VBE is the bias voltage that drives the laser diode. Crystal and -4- 1223931 Α7 Β7 V. Description of the invention (3) In other words, it is about 0.7 volts. Re is the emitter resistance, which is used to limit the bias current Ibias. When the output voltage of the operational amplifier is V. When it becomes larger, the bias current Ibias of the laser diode also becomes larger. Therefore, the luminous intensity is brought to the original set level, thereby achieving the purpose of adjusting the luminous intensity by using negative feedback and maintaining the luminous intensity to be stable. Conversely, if the light emitting intensity of the laser diode becomes larger, the photocurrent Imon on the sensing side will increase, and the voltage V_ of the inverting input terminal of the operational amplifier 13 will increase accordingly, causing the output voltage of the operational amplifier 13 V. Decrease. Therefore, the bias current Ibias that drives the laser diode will be reduced, and the luminous intensity of the laser 10 diode will be reduced to maintain the original set level. The relationship between the optical power PR received by the optical sensor 11 and the actual optical power Pout emitted by the laser diode is as follows:
Pr- V (T)*p0ut .....................(3) 15 其中(T)為溫度之函數。而光電流即為：Pr- V (T) * p0ut ..... (3) 15 where (T) is a function of temperature. The photocurrent is:
Imon=|：(T)*PR .....................(4) 經濟部智慧財產局員工消費合作社印製 20 其中f (T)為反應度(responsivity)，亦為溫度的函數。由式 (3)與式(4可得： P〇ut/Im〇n=l/7/(T)* ^(T) ……（5) 本紙張尺度適用中國國家標準(CNS)A4規格（210 X 297公釐） 五、發明說明（4) ~ ~-- 縱比二、、=為追縱比(Tracking Ratio)。在實際情況下，追 二二變化的情形有兩種’分別顯示於圖三⑷以及圖 ^圖（a)所顯示的情形為追蹤比會隨著溫度的升高 而，而圖三(b)顯示追縱比會隨著溫度的升高而增大。 二-疋兩種If况中的何者，都會使得光學收發器之自動功 率控制系統在溫度變化的情形下，無法維持雷射二極體之 發光強度的良好穩定性。 “以圖一(a)所示者為例，當吾人選定參考電壓Vref以及 X mon之值則光電流I_=Vref/Rmon即為固定。然而， 10當溫度升南時，追縱比Pcnn/Imon變小，換言之，相同的光 電流Imcm所對應的雷射二極體之光功率變小了。反之，如 果是圖三(b)所示的狀況，當溫度升高時，追蹤比p_/Im^ 變大’即相同的光電流在高溫下所對應的雷射二極體 之光功率變大。因此，控制光電流Imon使之固定並不表示 15控制了雷射二極體之光功率。 因此’需要有能夠解決追蹤比隨溫度變化之問題的方 案。本發明即能滿足此一需求。 經濟部智慧財產局員工消費合作社印製 發明概述： 20 本發明之目的係在於提供一種改良之用於光學收發器 之自動功率控制電路結構，其可克服追蹤比會隨溫度變化 的問題。 本發明之另一目的係在於提供一種改良之用於光學收 發器之自動功率控制電路結構，利用低成本而簡單的電路 本紙張尺度適用中國國家標準(CNS)A4規格（210x297公釐） 1223931 A7Imon = |: (T) * PR ........... (4) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 20 where f (T) is Responsivity is also a function of temperature. According to formula (3) and formula (4): P〇ut / Im〇n = l / 7 / (T) * ^ (T) …… (5) This paper size applies the Chinese National Standard (CNS) A4 specification ( (210 X 297 mm) V. Description of the invention (4) ~ ~-The vertical ratio of two, and = are the Tracking Ratio. In actual circumstances, there are two kinds of changes in the tracking of two and two. Figure 3 (b) and Figure ^ (a) show that the tracking ratio will increase with temperature, and Figure 3 (b) shows that the tracking ratio will increase with temperature. Either of the two If conditions will make the automatic power control system of the optical transceiver unable to maintain the good stability of the luminous intensity of the laser diode under temperature changes. "The one shown in Figure 1 (a) As an example, when I choose the values of the reference voltage Vref and X mon, the photocurrent I_ = Vref / Rmon is fixed. However, when the temperature rises south, the chase becomes smaller than Pcnn / Imon, in other words, the same photocurrent The light power of the laser diode corresponding to Imcm becomes smaller. Conversely, if the situation shown in Fig. 3 (b), when the temperature increases, the tracking ratio p_ / Im ^ becomes larger, which is the same The optical power of the laser diode corresponding to the current at high temperature becomes larger. Therefore, controlling the photocurrent Imon to fix it does not mean that 15 controls the optical power of the laser diode. Therefore, 'the need to be able to solve the tracking ratio The solution to the problem of temperature change. The present invention can meet this demand. Printed by the Consumers' Cooperative of the Intellectual Property Bureau of the Ministry of Economics Summary of Invention: 20 The purpose of the present invention is to provide an improved automatic power control for optical transceivers The circuit structure can overcome the problem that the tracking ratio changes with temperature. Another object of the present invention is to provide an improved automatic power control circuit structure for an optical transceiver, which uses a low-cost and simple circuit. China National Standard (CNS) A4 (210x297 mm) 1223931 A7
元件，達到補償追蹤比隨溫度變化造成的不穩定性，從而 使光學收發器之雷射二極體的發光強度維持高穩定度。 根據本發明之一方面，一種用於光學收發器之自動功 率控制電路結構，其係具有一溫度補償電路，用於補償追 5 縱比隨溫度改變造成的誤差。 根據本發明之另一方面，其中該溫度補償電路係具有 一熱敏電阻。 根據本發明之又一方面，該溫度補償電路係耦接至自 動功率控制電路之運算放大器的反相輸入端。 〇 根據本發明之再一方面，該溫度補償電路係耦接至自 動功率控制電路之運算放大器的非反相輸入端。 圖式簡單說明： 圖一係顯示雷射二極體的發光強度對電流在不同溫度 15 下的特性曲線； 圖二係顯示習用之用於光學收發器之自動功率控制電 路結構， 經濟部智慧財產局員工消費合作社印製 圖二(a)係顯示光學收發器之自動功率控制電路中追蹤 比隨著溫度的升高而變小之情形； 20 圖三(t〇係顯示光學收發器之自動功率控制電路中追蹤 比隨著溫度的升高而增大之情形； 圖四係顯示根據本發明之一實施例的用於光學收發器 之自動功率控制電路結構；以及 圖五係顯示根據本發明之另一實施例的用於光學收發 -7- 本紙張尺度適用中國國家標準(CNS)A4規格（210 X 297公釐） 1223931 A7 B7 五、發明說明（6) 器之自動功率控制電路結構 元件符號簡單說明： 11 光感測器 經濟部智慧財產局員工消費合作社印製 5 12 13 14 15 16 10 41 43 44 45 46 15 47 48 49 51 52 20 53 54 55 56 57 25 58 59 電阻器 運算放大器 電阻器 雷射二極體 積分器 光感測器 運算放大器 電阻器 雷射二極體 積分器 熱敏電阻器 電阻器 可變電阻器 感測器 分壓電阻器 運算放大器 電阻器 雷射二極體 積分器 熱敏電阻器 電阻器 可變電阻器 本紙張尺度適用中國國家標準(C^NS)A4規格（210 X 297公釐） 1223931 A7 B7 五、發明說明（7) 實施例詳細說明： 請參見圖四，其係顯示根據本發明之用於光學收發器 的自動功率控制電路結構。於該圖中，具有類似於圖一之 元件符號的元件係與圖一之對應元件相同。41為光感測 5 器，43為運算放大器，44為電阻器，45為雷射二極體， 46為電容器以及電阻器並聯構成的積分器。與圖一最大的 不同之處在於圖一之電阻Rm()n部分係由溫度補償電路取 代。於本實施例中，溫度補償電路係由並聯的熱敏電阻器 47與電阻器Rm 48構成，並可串聯一可變電阻49。其中 10 與電阻器Rm 48並聯連接的熱敏電阻47可藉以調整出補 償光電流Imon所需的最佳幅度。而可變電阻49則用於調 整所需之初始電阻值。熱敏電阻47在選用上，係視狀況 而定。如果是在PQUt/Im()n隨溫度變小的情況下，應選擇使 用負溫度係數之熱敏電阻。而在Pout/Imon隨溫度變大的情 15 況下，則應選擇使用正溫度係數之熱敏電阻。 經濟部智慧財產局員工消費合作社印製 圖五係顯示根據本發明之另一實施例的電路結構。於 該圖中，具有類似於圖四之元件符號的元件係與圖四之對 應元件相同。51為光感測器，53為運算放大器，54為電 阻器，55為雷射二極體，56為電容器以及電阻器並聯構 20 成的積分器。與圖四之電路結構不同，熱敏電阻器57與 電阻器Rm 58並聯的溫度補償電路係接在運算放大器53 的非反相輸入端。較佳而言，該運算放大器53之非反相 輸入端又加上一個分壓電阻52。由於熱敏電阻器57與電 阻器Rm 58並聯的溫度補償電路係接在運算放大器53的 -9- 本纸張尺度適用中國國家標準(CNS)A4規格（2丨0 x 297公釐） 1223931 A7 B7 10 五、發明說明（Ο 非反相輸入端，故可使該運算放大器53之非反相輸入端 的電壓隨溫度變化而改變。在PQut/ImQn隨溫度變小的情況 下，應選擇使用正溫度係數之熱敏電阻，以在高溫下得到 較大之參考電壓vref，從而有較大之光電流imcn。而在 Pout/Imon隨溫度變大的情況下，則應選擇使用負溫度係數 之熱敏電阻，以在高溫下得到較小之參考電壓Vref，從而 有較小之光電流Im()n。 本發明已就貫施例作詳細說明，然而上述實施例僅為 例示性說明本發明之原理以及功效，並非用於限制本發 明。熟知此項技藝者可知，不悖離本發明之精神與範疇的 各種修正、變更均可實行^發明之保護範@係如所附之 申請專利範圍所界定。 裝 計 線The device achieves compensation for the instability caused by the change of the tracking ratio with temperature, thereby maintaining the high stability of the luminous intensity of the laser diode of the optical transceiver. According to one aspect of the present invention, an automatic power control circuit structure for an optical transceiver is provided with a temperature compensation circuit for compensating an error caused by a change in an aspect ratio with temperature. According to another aspect of the present invention, the temperature compensation circuit has a thermistor. According to another aspect of the present invention, the temperature compensation circuit is coupled to an inverting input terminal of an operational amplifier of an automatic power control circuit. 〇 According to another aspect of the present invention, the temperature compensation circuit is coupled to a non-inverting input terminal of an operational amplifier of an automatic power control circuit. Brief description of the figure: Figure 1 shows the characteristic curve of the laser diode's luminous intensity versus current at different temperatures 15; Figure 2 shows the structure of the automatic power control circuit used in optical transceivers, which is the intellectual property of the Ministry of Economic Affairs Figure 2 (a) printed by the Bureau ’s Consumer Cooperative shows the situation where the tracking ratio in the automatic power control circuit of the optical transceiver becomes smaller as the temperature increases; 20 Figure 3 (t〇 shows the automatic power of the optical transceiver The tracking ratio in the control circuit increases as the temperature increases; Fig. 4 shows the structure of an automatic power control circuit for an optical transceiver according to an embodiment of the invention; and Fig. 5 shows the structure of an automatic power control circuit for an optical transceiver according to an embodiment of the invention; Optical transceiver for another embodiment-7- This paper size applies Chinese National Standard (CNS) A4 specification (210 X 297 mm) 1223931 A7 B7 V. Description of the invention (6) Symbols of structural elements of the automatic power control circuit of the device Brief description: 11 Photo sensor Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 5 12 13 14 15 16 10 41 43 44 45 46 15 47 48 49 51 52 20 53 54 55 56 57 25 58 59 Resistor Op Amp Resistor Laser Diode Volume Divider Light Sensor Op Amp Resistor Laser Diode Volume Divider Thermistor Resistor Variable Resistor Sensor Voltage Divider Resistor Op Amp Resistor Ray Radiation Diode Volume Divider Thermistor Resistor Variable Resistor This paper size is applicable to China National Standard (C ^ NS) A4 (210 X 297 mm) 1223931 A7 B7 V. Description of the invention (7) Example details Explanation: Please refer to FIG. 4, which shows the structure of an automatic power control circuit for an optical transceiver according to the present invention. In this figure, the components having the component symbols similar to those in FIG. 1 are the same as the corresponding components in FIG. 1. 41 is a photo-sensing device, 43 is an operational amplifier, 44 is a resistor, 45 is a laser diode, and 46 is an integrator composed of a capacitor and a resistor in parallel. The biggest difference from Figure 1 lies in Figure 1. The resistor Rm () n is replaced by a temperature compensation circuit. In this embodiment, the temperature compensation circuit is composed of a thermistor 47 and a resistor Rm 48 connected in parallel, and a variable resistor 49 can be connected in series. Among them, the thermistor 47 connected in parallel with the resistor Rm 48 can be used to adjust the optimal amplitude required to compensate the photocurrent Imon. The variable resistor 49 is used to adjust the required initial resistance value. The thermistor 47 is in Selection depends on the situation. If PQUt / Im () n decreases with temperature, a thermistor with a negative temperature coefficient should be selected. In the case where Pout / Imon increases with temperature, 15 Next, you should choose a thermistor with a positive temperature coefficient. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs Figure 5 shows a circuit structure according to another embodiment of the present invention. In this figure, the components having the component symbols similar to those in FIG. 4 are the same as the corresponding components in FIG. 51 is a light sensor, 53 is an operational amplifier, 54 is a resistor, 55 is a laser diode, and 56 is an integrator composed of a capacitor and a resistor in parallel. Different from the circuit structure of FIG. 4, the temperature compensation circuit of the thermistor 57 and the resistor Rm 58 connected in parallel is connected to the non-inverting input terminal of the operational amplifier 53. Preferably, a non-inverting input terminal of the operational amplifier 53 is added with a voltage dividing resistor 52. Since the thermistor 57 and the resistor Rm 58 are connected in parallel to the temperature compensation circuit of the operational amplifier 53, the paper size applies to the Chinese National Standard (CNS) A4 specification (2 丨 0 x 297 mm) 1223931 A7 B7 10 V. Description of the invention (0 non-inverting input terminal, so the voltage of the non-inverting input terminal of the operational amplifier 53 can be changed with temperature. When PQut / ImQn decreases with temperature, you should choose to use positive Thermistor with temperature coefficient, in order to get a larger reference voltage vref at high temperature, so there is a larger photocurrent imcn. And when Pout / Imon becomes larger with temperature, you should choose to use a negative temperature coefficient of the heat The varistor is used to obtain a small reference voltage Vref at high temperature, so that there is a small photocurrent Im () n. The present invention has been described in detail in the embodiments, but the above embodiments are only illustrative examples The principle and effect are not intended to limit the present invention. Those skilled in the art will know that various modifications and changes can be implemented without departing from the spirit and scope of the present invention ^ The protection scope of the invention is @ boundary . Gauge line means
經濟部智慧財產局員工消費合作社印製 本紙張尺度適用中國國家標準(CNS)A4規i (21〇x297^) ~----Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs This paper standard applies to China National Standard (CNS) A4 Regulation (21〇x297 ^) ~ ----