激光器驅(qū)動電路中英文翻譯

1、<p><b>　　中文2540字</b></p><p>　　Laser driver circuit</p><p>　　Small changes will directly semiconductor laser drive current to the output intensity fluctuation. To stabilize the o

2、utput power semiconductor laser, Voltage negative feedback principle to design a constant current driving circuit comprises a soft starting and current limiting protection circuit based on; At the same time, according to

3、 the need of the light source is modulated to eliminate the influence of background light and, integrated laser modulation circuit comprises a crystal oscillation </p><p>　　Semiconductor laser with its excel

4、lent characteristics, high efficiency, simple structure, small is widely used in scientific research, national defense, medical, and other areas of processing, its drive technology becomes more and more important. Semico

5、nductor laser is the ideal electron - photon direct conversion devices, quantum efficiency is very high, the current small changes will lead to a great change, the output light intensity of the therefore, semiconductor l

6、aser drive current require</p><p>　　In some applications, DC semiconductor lasers produce DC drive light in the measurement process is vulnerable to interference from ambient light slow change, which could n

7、ot be separated from the environment light required DC optical signal, the signal-to-noise ratio is too small, so to carry on the modulation. When the high-speed modulated semiconductor lasers, there will be dynamic char

8、acteristics is complex, such as the relaxation oscillation, since the pulse and multi-pulse phenomena. In thi</p><p>　　In this paper, the design of driving the semiconductor laser modulation circuit composed

9、 of four parts, including constant current circuit, a soft start, current limit protection and modulation signal generating circuit. The constant current circuit to generate a high stable drive current. Soft start is the

10、 role of eliminating surge may be present in the circuit, to prevent the harm of surge for laser. To avoid damage due to overcurrent caused by semiconductor laser can not be restored, then add</p><p>　　The c

11、onstant current circuit is shown in figure 1, The in-phase end voltage reference Vr into A1 op amp, the operational control amplifier conducting level, and thus to obtain the corresponding output current. The output curr

12、ent generated by sampling voltage sampling resistor Rs, the sampling voltage is amplified as the inverting input voltage feedback voltage feedback amplifier A1, and voltage and the in-phase input end of comparison, Q2 to

13、 adjust the output voltage through the triode, adjustme</p><p>　　Figure 1 Constant current map</p><p>　　Because the switch instantaneous in power supply generates a voltage, current surge, as w

14、ell as the surge interference effects are likely to cause the breakdown and the damage of the semiconductor laser, and therefore must be in the design of soft start circuit drive laser, namely the use of the charge and d

15、ischarge of RC circuit, delay time, the specific circuit as shown in Figure 2 as shown in. Switch S1 is closed, the current through the resistor R1 and capacitor C3 to charge, the base electr</p><p>　　Figure

16、 2 Soft start circuit diagram</p><p>　　Laser soft start time and the charging capacitor and the corresponding resistance, when the capacitor charging tends to saturation, the output voltage soft start circu

17、it can achieve maximum. Power supply voltage is V I, the capacitor voltage is Vo, the capacitor charging formula:</p><p>　　According to this formula can calculate the electric charge and discharge time.</

18、p><p>　　Semiconductor laser with other devices, have normal working current, if the current exceeds this range, the laser will be damaged, therefore must restrict current laser in the set range.</p><

19、p>　　Emitter voltage transistor Q2 as the feedback voltage terminal phase in A3 op amp, when the feedback voltage is less than the limit voltage V, A3 op amp output low level, the transistor Q1 is turned on, this time

20、by a triode Q2 output voltage feedback voltage is greater than the limit; when the voltage of V, A3 op amp output high, triode Q1 cutoff, this limits the triode Q2 emission increases very current, and is limited to a spe

21、cific value. So even if the current caused by Vr control voltage ex</p><p>　　Modulation signal generating circuit is composed of a crystal oscillating circuit and divider circuit is composed of two parts, us

22、ed to generate the high stability of frequency, duty cycle square wave signal is stable. Crystal oscillating circuit directly generated by the active oscillator, oscillation frequency is 1MHz. Frequency divider circuit c

23、omposed of a CMOS integrated circuit 4040.1MHz pulse signal after the frequency by 4040, pin output frequency from the switch is selected, the duty cy</p><p>　　Driving an important technical parameters of ci

24、rcuit for current stability. Current stability is in a certain period of time, several measurements through the current size of the semiconductor laser, namely the ratio of output current stability for the relative chang

25、e amount and input current, stability calculation, there will be current relative change is defined as the measurement of the maximum and minimum values, will measure the average value as the input current value.</p&g

26、t;<p>　　Drive circuit based on voltage negative feedback principle, by constant current drive mode to realize the control of the injection current and output power of semiconductor laser, and it can provide high s

27、table output current, current stability 0.05%. Drive circuit with soft start, current limit circuit protection, reduce the damage of semiconductor laser to surge breakdown and current, the modulation circuit and the driv

28、e circuit effectively combined, realize the frequency is, the development o</p><p>　　The causes of dispersion: One is the light emitted by the light source is not monochromatic light; two is the modulation s

29、ignal has a certain bandwidth.</p><p>　　The dispersion of the classification: By different modes or different frequency (or wavelength) light signal components, transmission in optical fibers, due to the phy

30、sical phenomenon of different group velocities cause signal distortion is called fiber dispersion. The fiber dispersion is divided into mode dispersion (or intermodal distortion), material dispersion and waveguide disper

31、sion. After two kinds of dispersion is the dispersion a pattern, also known as intra-modal dispersion.</p><p>　　Dispersion harm: Fiber dispersion in optical signal waveform distortion, performance for the pu

32、lse width, it is the time domain characteristics of optical fiber. In digital communication system, pulse broadening of optical signal is an important index. Pulse broadening is too large can cause adjacent pulse gap dec

33、reases, the adjacent pulse will overlap and regenerative repeater decision errors occur, which increases the BER, transmission bandwidth narrowing, limit the transmission capacity of op</p><p>　　Said method

34、of dispersion: Commonly used dispersion representation has maximum time delay for $S, pulse width R and optical bandwidth of 3dB B three. The maximum time delay difference delay description fiber in the fastest and most

35、slow wave component. Used to describe the effect of fiber dispersion on the transmission signal pulse broadening and optical fiber bandwidth. A section of optical fiber as a network analysis of the dispersion characteris

36、tics, the available time domain method and frequ</p><p><b>　　激光器驅(qū)動電路</b></p><p>　　半導(dǎo)體激光器驅(qū)動電流的微小變化將直接導(dǎo)致其輸出光強的波動。為實現(xiàn)半導(dǎo)體激光器的穩(wěn)定功率輸出,基于電壓負(fù)反饋原理設(shè)計了包含軟啟動和限流保護電路的恒流驅(qū)動電路;同時針對為消除背景光的影響而對光源進行調(diào)制的

37、需要,設(shè)計了包括晶體振蕩電路和分頻電路的集成激光器調(diào)制電路。制作具體電路并完成了相關(guān)實驗。實驗結(jié)果表明該電路能夠提供高穩(wěn)定度的驅(qū)動電流,電流穩(wěn)定度達0.05%;軟啟動和限流保護電路可保護半導(dǎo)體激光器并提高其抗沖擊能力。調(diào)制電路產(chǎn)生半導(dǎo)體激光器調(diào)制所需的載波信號并直接完成輸出光調(diào)制,通過開關(guān)可方便地實現(xiàn)從256Hz到512kHz范圍內(nèi)12種常用調(diào)制頻率的選擇。</p><p>　　半導(dǎo)體激光器以其超小型、高效率、結(jié)

38、構(gòu)簡單等優(yōu)良特性被廣泛應(yīng)用于科研、國防、醫(yī)療、加工等領(lǐng)域,其相應(yīng)的驅(qū)動技術(shù)也顯得越來越重要。半導(dǎo)體激光器是理想的電子-光子直接轉(zhuǎn)換器件,有很高的量子效率,微小的電流變化都將導(dǎo)致其輸出光強的很大變化,因此,半導(dǎo)體激光器的驅(qū)動電流要求非常高。半導(dǎo)體激光器的驅(qū)動技術(shù)通常采用恒流驅(qū)動方式,在此工作方式下,通過負(fù)反饋原理控制回路,直接提供驅(qū)動電流的有效控制。此外,瞬態(tài)的電流或電壓尖峰脈沖,以及過流、過壓都會損壞半導(dǎo)體激光器,因此驅(qū)動電路中還應(yīng)考慮

39、特殊的抗電沖擊措施和保護電路。</p><p>　　在一些測量應(yīng)用中,直流驅(qū)動的半導(dǎo)體激光器產(chǎn)生的直流光在測量過程中容易受到緩慢變化的環(huán)境光的干擾, 導(dǎo)致無法從環(huán)境光中分離出所需直流光信號, 本文系統(tǒng)信噪比過小,因此要對其進行調(diào)制。當(dāng)半導(dǎo)體激光器進行高速調(diào)制時, 會出現(xiàn)很復(fù)雜的動態(tài)特性,如馳豫振蕩、自脈動以及多脈沖等現(xiàn)象。本文對其低頻調(diào)制特性進行了實驗研究。半導(dǎo)體激光器輸出有足夠的穩(wěn)定性,且可直接調(diào)制, 它已在光

40、纖系統(tǒng)中得到普遍應(yīng)用,是傳感器系統(tǒng)的首選光源。本文為光纖系統(tǒng)的光源設(shè)計了一種高穩(wěn)定度驅(qū)動電流、可調(diào)制、操作簡單且成本低廉的驅(qū)動電路。</p><p>　　本文設(shè)計的半導(dǎo)體激光器驅(qū)動調(diào)制電路由四大部分組成,包括恒流電路、軟啟動、限流保護和調(diào)制信號產(chǎn)生電路。恒流電路產(chǎn)生高穩(wěn)定度驅(qū)動電流。軟啟動的作用是消除電路中可能存在的浪涌,防止浪涌對激光器的危害。為避免由于過流等因素引起半導(dǎo)體激光器不可恢復(fù)的損壞,則在驅(qū)動電路中加

41、入限流保護。調(diào)制信號產(chǎn)生電路實現(xiàn)調(diào)制和頻率可調(diào)。</p><p>　　實際的恒流電路見圖1,基準(zhǔn)電壓Vr送入運放A1的同相端,該運放控制放大器的導(dǎo)通程度,并由此獲得相應(yīng)的輸出電流。該輸出電流通過取樣電阻Rs產(chǎn)生取樣電壓,該取樣電壓經(jīng)放大后作為反饋電壓反饋回電壓放大器A1的反相輸入端,并與同相輸入端的電壓比較,通過三極管Q2對輸出電壓進行調(diào)整,進而對半導(dǎo)體激光器的輸出電流進行調(diào)整,使整個閉環(huán)反饋系統(tǒng)處于動態(tài)的平衡中

42、。</p><p><b>　　圖1 恒定電流圖</b></p><p>　　由于在電源開關(guān)開啟的瞬間會產(chǎn)生電壓、電流浪涌沖擊,以及外界干擾產(chǎn)生的浪涌影響都有可能造成半導(dǎo)體激光器的擊穿和損壞,因此必須在激光器驅(qū)動電路中設(shè)計軟啟動電路,即利用RC電路的充放電,實現(xiàn)時間上的延遲,具體電路如圖2所示。開關(guān)S1閉合后,電流經(jīng)電阻R1向電容C3充電,三極管Q基極電壓逐漸升高。隨

43、著電容的充電以及三極管的導(dǎo)通, 輸出電壓Vo實現(xiàn)了從0到最大的緩慢上升, 直到電容充電飽和后,此時電壓和電流趨于穩(wěn)定。當(dāng)電源斷開時,上述過程反向, 從而實現(xiàn)電流和電壓的緩慢下降。</p><p><b>　　圖2 軟啟動電路圖</b></p><p>　　激光器的軟啟動時間與充電電容和相應(yīng)電阻有關(guān),當(dāng)電容充電趨于飽和時, 軟啟動電路的輸出電壓可以達到最大。設(shè)電源電壓為

44、Vi,電容電壓為Vo,電容充電公式為:</p><p>　　根據(jù)此公式可以計算電路充放電的時間。</p><p>　　半導(dǎo)體激光器同其他器件一樣,都有正常工作電流,如果電流超過這個范圍,激光器將會被損壞,因此必須把激光器的工作電流限制在設(shè)定范圍內(nèi)。</p><p>　　三極管Q2的發(fā)射極電壓作為反饋電壓加在運放A3的同相端,當(dāng)反饋電壓小于限制電壓V時,運放A3輸出低

45、電平,三極管Q1管導(dǎo)通,此時由三極管Q2輸出電壓;當(dāng)反饋電壓大于限制電壓V 時,運放A3 輸出高電平,三極管Q1截止,此時限制了三極管Q2 發(fā)射極電流的增加,而被限制在某一特定值上。因此即使控制電壓Vr 所引起的電流超過設(shè)定值,又由于三極管Q1和Q2是串聯(lián)在一起的,所以總的電流就會被箝制在設(shè)定電流值上。</p><p>　　調(diào)制信號產(chǎn)生電路由晶體振蕩電路和分頻電路兩部分組成,用于產(chǎn)生頻率穩(wěn)定度高,占空比穩(wěn)定的方波

46、信號。晶體振蕩電路直接由有源晶振產(chǎn)生,振蕩頻率為1MHz。分頻電路由CMOS 集成電路4040實現(xiàn)。1MHz脈沖信號經(jīng)4040分頻后,從開關(guān)選中的管腳輸出一定頻率,占空比為50% ,幅值為5V的方波信號。經(jīng)分頻后的調(diào)制頻率分別為256Hz,512Hz,1kHz,2kHz,4kHz,8kHz,16kHz,32kHz,64kHz128kHz, 256kHz,512kHz。</p><p>　　驅(qū)動電路一個重要技術(shù)參數(shù)

47、為電流穩(wěn)定度。電流穩(wěn)定度是在一定時間內(nèi),多次測量通過半導(dǎo)體激光器的電流大小,即穩(wěn)定度為輸出電流的相對變化量與輸入電流的比值, 進行穩(wěn)定度計算,這里將電流相對變化定義為測量最大值與最小值之差,將測量平均值作為輸入電流值。</p><p>　　驅(qū)動電路基于電壓負(fù)反饋原理,通過恒流驅(qū)動方式實現(xiàn)了對半導(dǎo)體激光器注入電流和輸出光強的控制,并能夠提供高穩(wěn)定度的驅(qū)動電流, 電流穩(wěn)定度0.05%。驅(qū)動電路中加入了軟啟動、限流保護

48、等輔助電路,減少了由于浪涌擊穿和過電流導(dǎo)致的半導(dǎo)體激光器的損壞,同時將調(diào)制電路和驅(qū)動電路有效地結(jié)合起來,實現(xiàn)了頻離,發(fā)展新型光纖通信技術(shù)都是至關(guān)重要的。</p><p>　　色散的原因: 一是光源發(fā)出的光并不是單色光;二是調(diào)制信號有一定的帶寬。</p><p>　　色散的分類: 由不同模式或不同頻率( 或波長) 成分組成的光信號,在光纖中傳輸時,由于群速度不同而引起信號畸變的物理現(xiàn)象稱為光

49、纖的色散。光纖的色散分為模式色散( 或模間畸變)、材料色散以及波導(dǎo)色散。后兩種色散是某一模式本身的色散,也稱模內(nèi)色散。</p><p>　　色散的危害: 光纖的色散導(dǎo)致光信號的波形失真,表現(xiàn)為脈沖寬度,它是光纖的時域特性。對于數(shù)字通信系統(tǒng)來講,光信號的脈沖展寬是一項重要的指標(biāo)。脈沖展寬過大就會引起相鄰脈沖間隙減小,相鄰脈沖將會產(chǎn)生部分重疊而使再生中繼器發(fā)生判決錯誤,從而使誤碼率增加,傳輸頻帶變窄,限制了光纖的傳輸