激光器驅動電路中英文翻譯

1 中文 2540 字 Laser driver circuit Small changes will directly semiconductor laser drive current to the output intensity fluctuation. To stabilize the output 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 the need of the light source is modulated to eliminate the influence of background light and, integrated laser modulation circuit comprises a crystal oscillation circuit and divider circuit design. Making the specific circuit and complete the relevant experimental. The experimental results show that the circuit can provide a driving current of high stability, Current stability up to 0.05%; Soft start and current-limiting protection circuit can protect the semiconductor laser and enhance the impact capability. Modulation circuit generates a carrier signal needed for laser diode modulation and direct to complete the output light modulation, The switch can be conveniently realized from 256Hz to 512kHz range of 12 kinds of commonly used modulation frequency selection. Semiconductor laser with its excellent 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. Semiconductor 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 laser drive current requirements is very high. Driving technology of semiconductor laser usually adopts constant current drive mode, this work, through the principle of negative feedback control loop, directly provide the effective control of the drive current. In addition, the transient current or voltage spikes, and overcurrent, overvoltage will damage the semiconductor laser drive circuit, therefore should be considered in the protection circuit against electric shock measures and special. 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 not 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 characteristics is 2 complex, such as the relaxation oscillation, since the pulse and multi-pulse phenomena. In this paper, experiments were conducted to study the characteristics of low frequency modulation. Semiconductor laser output is stable, and can be directly modulated, it has been widely applied in optical system, is the preferred source sensor system. This paper describes the design of a high stability driving current, modulation, simple operation and low cost driving circuit for the light source of optical fiber systems. In this paper, the design of driving the semiconductor laser modulation circuit composed 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 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 adding current-limiting protection in a driver circuit. Circuit to realize the modulation and frequency can be adjusted to generate a modulated signal. The constant 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 current 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 adjust the output voltage through the triode, adjustment and output current of semiconductor lasers, so that the whole closed-loop feedback system in the dynamic balance. Figure 1 Constant current map Because the switch instantaneous in power supply generates a voltage, current surge, as well as the surge interference effects are likely to cause the breakdown and 116AR81 16R 6 A5.1KA1O P A M PA R ?O P A M P+ 1 2 V12U7l a s e rQ22 N 2 2 2 2 AR71K- 1 2 VVr1 16R 5 A1M3 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 discharge 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 electrode of the triode Q voltage gradually rises. As the capacitor charging and the conduction of the triode, output voltage Vo is achieved from 0 to the maximum rise slowly, until the capacitor charge saturation, the voltage and current stabilizing. When the power supply is disconnected, the process of reverse, so as to realize the current and voltage decreases slowly. Figure 2 Soft start circuit diagram Laser soft start time and the charging capacitor and the corresponding resistance, when the capacitor charging tends to saturation, the output voltage soft start circuit can achieve maximum. Power supply voltage is V I, the capacitor voltage is Vo, the capacitor charging formula: 10 (1 )RCiV V e According to this formula can calculate the electric charge and discharge time. 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. 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 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 specific value. So even if the current caused by Vr control voltage exceeds the set V i n1GND2V ou t3U178 L 05C6105C2104C3105S1R11MV0Q2N 22 22 A4 value, the triode Q1 and Q2 are connected in series, so the total current will be clamped in the setting current value. Modulation signal generating circuit is composed of a crystal oscillating circuit and divider circuit is composed of two parts, used 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 composed of a CMOS integrated circuit 4040.1MHz pulse signal after the frequency by 4040, pin output frequency from the switch is selected, the duty cycle is 50%, amplitude is 5V square wave signal. The modulation frequency dividing frequency were 256Hz, 512Hz, 1kHz, 2kHz,4kHz,8kHz,16kHz,32kHz, 64kHz128kHz, 256kHz, 512kHz. Driving an important technical parameters of circuit 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 change 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. 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 stable 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 drive circuit effectively combined, realize the frequency is, the development of new technology of optical fiber communication is essential. The causes of dispersion: One is the light emitted by the light source is not monochromatic light; two is the modulation signal has a certain bandwidth. The dispersion of the classification: By different modes or different frequency (or wavelength) light signal components, transmission in optical fibers, due to the physical 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 dispersion. After two kinds of dispersion is the dispersion a pattern, also known as intra-modal dispersion. Dispersion harm: Fiber dispersion in optical signal waveform distortion, performance for the pulse width, it is the time domain characteristics of optical fiber. 5 In digital communication system, pulse broadening of optical signal is an important index. Pulse broadening is too large can cause adjacent pulse gap decreases, the adjacent pulse will overlap and regenerative repeater decision errors occur, which increases the BER, transmission bandwidth narrowing, limit the transmission capacity of optical fiber. Said method 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 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 characteristics, the available time domain method and frequency domain method. When in the time domain analysis, dispersion effect is represented by the pulse broadening, and analyzed in the frequency domain, the transmission bandwidth said. 6 激光器驅動電路 半導體激光器驅動電流的微小變化將直接導致其輸出光強的波動 。 為實現(xiàn)半導體激光器的穩(wěn)定功率輸出 ,基于電壓負反饋原理設計了包含軟啟動和限流保護電路的恒流驅動電路 ;同時針對為消除背景光的影響而對光源進行調制的需要 ,設計了包括晶體振蕩電路和分頻電路的集成激光器調制電路 。 制作具體電路并完成了相關實驗 。 實驗結果表明該電路能夠提供高穩(wěn)定度的驅動電流 ,電流穩(wěn)定度達 0.05%;軟啟動和限流保護電路可保護半導體激光器并提高其抗沖擊能力 。 調制電路產生半導體激光器調制所需的載波信號并直接完成輸出光調制 ,通過開關可方便地實現(xiàn)從 256Hz到 512kHz范圍內 12種常用調制頻率的選擇 。 半導體激光器以其超小型、高效率、結構簡單等優(yōu)良特性被廣泛應用于科研、國防、醫(yī)療、加工等領域 ,其相應的驅動技術也顯得越來越重要。半導體激光器是理想的電子 -光子直接轉換器件 ,有很高的量子效率 ,微小的電流變化都將導致其輸出光強的很大變化 ,因此 ,半導體激光器的驅動電流要求非常高。半導體激光器的驅動技術通常采用恒流驅動方式 ,在此工作方式下 ,通過負反饋原理控制回路 ,直接提供驅動電流的有效控制。此外 ,瞬態(tài)的電流或電壓尖峰脈沖 ,以及過流、過壓都會損壞半導體激光器 ,因此驅動電路中還應考慮特殊的抗電沖擊措施和保護電路。 在一些測量應用中 ,直流驅動的半導體激光器產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 ,因此要對其進行調制。當半導體激光器進行高速調制時 , 會出現(xiàn)很復雜的動態(tài)特性 ,如馳豫振蕩、自脈動以及多脈沖等現(xiàn)象。本文對其低頻調制特性進行了實驗研究。半導體激光器輸出有足夠的穩(wěn)定性 ,且可直接調制 , 它已在光纖系統(tǒng)中得到普遍應用 ,是傳感器系統(tǒng)的首選光源。本文為光纖系統(tǒng)的光源設計了一種高穩(wěn)定度驅動電流、可調制、操作簡單且成本低廉的驅動電路。 本文設計的半導體激光器驅動調制電路由四大部分組成 ,包括恒流電路、軟啟動、限流保護和調制信號產生電路。恒流電路產生 高穩(wěn)定度驅動電流。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體激光器不可恢復的損壞 ,則在驅動電路中加入限流保護。調制信號產生電路實現(xiàn)調制和頻率可調。 實際的恒流電路見圖 1,基準電壓 Vr送入運放 A1的同相端 ,該運放控制放大器的導通程度 ,并由此獲得相應的輸出電流。該輸出電流通過取樣電阻 Rs產生取樣7 電壓 ,該取樣電壓經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對輸出電壓進行調整 ,進而對半導體激光器的輸出電流進行調整 ,使整個閉環(huán)反饋系統(tǒng)處于動態(tài)的平衡中 。 圖 1 恒定電流圖 由于在電源開關開啟的瞬間會產生電壓、電流浪涌沖擊 ,以及外界干擾產生的浪涌影響都有可能造成半導體激光器的擊穿和損壞 ,因此必須在激光器驅動電路中設計軟啟動電路 ,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 S1閉合后 ,電流經電阻 R1向電容 C3充電 ,三極管 Q基極電壓逐漸升高。隨著電容的充電以及三極管的導通 , 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。 圖 2 軟啟動電路圖 激光器的軟啟動時間與充電電容和相應電阻有關 ,當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。設電源電壓為 Vi,電容電壓為 Vo,電容充電公式為 : 116AR81 16R 6 A5.1KA1O P A M PA R ?O P A M P+ 1 2 V12U7l a s e rQ22 N 2 2 2 2 AR71K- 1 2 VVr1 16R 5 A1MV i n1GND2V ou t3U178 L 05C6105C2104C3105S1R11MV0Q2N 22 22 A8 10 (1 )RCiV V e 根據此公式可以計算電路充放電的時間。 半導體激光器同其他器件一