【正文】 激光器的發(fā)光效率和閾值電流與環(huán)境溫度成反比，即當(dāng)環(huán)境溫度升高時(shí)，激光器的發(fā)光效率會(huì)降低，閾值電流會(huì)升高。本設(shè)計(jì)中采用查表法來設(shè)置偏置和調(diào)制電流。如圖4 所示,調(diào)制電流設(shè)置表為80 個(gè)字節(jié)，每兩攝氏度占一個(gè)字節(jié)；功率設(shè)置表占用40 個(gè)字節(jié)，每4 攝氏度占用一個(gè)字節(jié)；溫度范圍都是40~120℃，滿足工業(yè)溫度的要求。數(shù)據(jù)表的數(shù)值確定則使用測試的方法得出。最后把這些數(shù)據(jù)保存到溫度查找表中，并同時(shí)保存到ATMEGA88 內(nèi)部的EEPROM 中。4 設(shè)計(jì)結(jié)果及測試分析本設(shè)計(jì)根據(jù)以上討論的方案，選擇PHY1076 專用芯片和ATMEGA88 單片機(jī)，外加適當(dāng)?shù)耐鈬娐吩O(shè)計(jì)電路板，把TOSA、ROSA 焊接到一起裝入定制外殼， 的SFP 光收發(fā)器。同時(shí)設(shè)計(jì)的上位機(jī)調(diào)試軟件對(duì)ATMEGA88 的溫度查找表進(jìn)行調(diào)試，確定了具體每個(gè)溫度下的值。然后對(duì)光收發(fā)器在低溫，常溫，高溫三種環(huán)境下的所有參數(shù)進(jìn)行測試。表1 光收發(fā)器的參數(shù)測試結(jié)果參數(shù)單位設(shè)計(jì)要求測試結(jié)果40186。C80186。激光器的輸出光功率和消光比都在參數(shù)要求范圍內(nèi)，且變化小。由于溫度變高時(shí)需要提供較大的調(diào)制電流，因此信號(hào)的下沖比較明顯，表現(xiàn)在眼圖中就是在眼圖中的“0”信號(hào)出現(xiàn)輕微雙眼線。由此驗(yàn)證了此設(shè)計(jì)方案的可行性和正確性。 單芯片SFP 光收發(fā)器。由于此方案是一個(gè)新的方案，技術(shù)成熟度有待提高，系統(tǒng)兼容性和市場應(yīng)用的潛在問題有待驗(yàn)證。但是可以相信，隨著網(wǎng)絡(luò)速率的加快和光接入對(duì)成本的壓力，新技術(shù)會(huì)越來越完善，市場占有率也會(huì)越來越高，屆時(shí)成本優(yōu)勢就會(huì)體現(xiàn)出來。s ATMEGA88 microcontroller, designed the optical transceiver samples, and conducted the performance test, with the ultimate success of the design of the optical transceiver.2 Discussion About The Design And Working Principle Of Optical TransceiverIn the development process of optical transceiver, there are many different outline package. SFP (Miniaturization hotswappable optical transceiver module) is currently one of the most advanced package in 5Gbps rate, with a small, hotswappable, low power consumption, high system integration and the ability to digitally Diagnostics and so on.This design uses laser driver circuit and optical receiver amplifier circuit ntegrated PHY1076 as a special chip , using ATMEL39。s cathode connected with the PHY1076’s Laser_bias pin. PHY1076’s data in internal power set register is input directly to the DAC, then DAC produces an analog voltage output to control output current in voltagecontrolled current the output current of current source supply the laser with DC bias current through the inductive coupling. Therefore, to modify the value of the power setting register is to modify the laser’s output optical power. The reverse leakage current of photoelectric sensor diode is proportional to the laser’s emission power. The current accesses PHY1076 from the MPD pin, after amplified and converted into a voltage signal,it is introduced into the control side of voltagecontrolled current source as a negative feedback signal in order to play the role of automatic power control. But the power range controled by APC is limited. When the temperature bees larger, APC will not provide enough current to maintain power to be stable due to the reduce of laser’s lightemitting efficient. At this moment we need to adjust the value of the power setting register ??to gain greater bias current to maintain power stable. This design is setting the value of register based on temperature by an external microcontroller to achieve temperature pensation purposes.Figure 2 Working Principle of APC2) The Realize of Extinction Ratio Control: PHY1076 internal modulation current control circuit is shown in Figure 3. Extinction ratio is defined as the ratio of optical power when sending data to 1 and optical power when sending data 0 in optical fiber munication system. Its value will affect the bit error rate of munication systems,hence we need to control within a certain range. In AC coupled circuits of modulated lasers, the average transmit power is affected by the DC bias current with the extinction ratio affected by modulation current. Within the PHY1076, when laser’s modulation current is set by a special register, then output control voltage after digitaltoanalog conversion so as to control the size of the output modulation current. Therefore, set the value of the register properly can obtain the ideal extinction ratio. Since there is no way to detect the size of the extinction ratio during working,we cann’t introduce the feedback circuit to achieve the automatic extinction ratio control. It is more feasible to look for the statistical law in extinction ratio and temperature change, and conduct temperature pensation by an external controller accordance with law. Figure 3 Schematic modulation current control3) ATMEGA88 Control Algorithm Analysis And DDM I