【正文】 ure）這些參數(shù)進(jìn)行實(shí)時(shí)監(jiān)視，并能夠在各項(xiàng)參數(shù)超過(guò)設(shè)定值時(shí)設(shè)置報(bào)警標(biāo)志位的功能。而且此單片機(jī)是一款在家電和工業(yè)控制領(lǐng)域使用廣泛的芯片，用量大，性能穩(wěn)定可靠，價(jià)格低。早期的光收發(fā)器中，大都使用專(zhuān)用模擬器件，所以要實(shí)現(xiàn)功率APC、溫度補(bǔ)償和消光比自動(dòng)控制都非常困難，或者很難得到滿意的效果。光電感應(yīng)二極管的反向漏電流與激光器的發(fā)射功率成正比。其值的大小會(huì)影響通信系統(tǒng)的誤碼率,因此需要控制在一定范圍內(nèi)。ATMEGA88 單片機(jī)內(nèi)部有一個(gè)標(biāo)準(zhǔn)的硬件I2C 接口，可以用來(lái)為系統(tǒng)設(shè)備提供SFPMSA（SFP 多源協(xié)議）要求的對(duì)外I2C。如圖4 所示,調(diào)制電流設(shè)置表為80 個(gè)字節(jié)，每?jī)蓴z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。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。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(chǎng)應(yīng)用的潛在問(wèn)題有待驗(yàn)證。C80186。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。由此驗(yàn)證了此設(shè)計(jì)方案的可行性和正確性。表1 光收發(fā)器的參數(shù)測(cè)試結(jié)果參數(shù)單位設(shè)計(jì)要求測(cè)試結(jié)果40186。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。圖4 ATMEGA88 與PHY1076 連接圖激光器的發(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。由于沒(méi)有辦法檢測(cè)工作中消光比的大小，因此無(wú)法引入反饋電路實(shí)現(xiàn)消光比自動(dòng)控制。此時(shí)就需要調(diào)節(jié)功率設(shè)置寄存器的值來(lái)獲得更大的偏置電流以保持功率穩(wěn)定。TOSA 內(nèi)部集成了一個(gè)激光發(fā)射二極管和一個(gè)光電感應(yīng)二極管。對(duì)具體某一個(gè)光收發(fā)器則希望其發(fā)光功率和消光比能夠長(zhǎng)期維持在一定范圍內(nèi)。ATMEL 公司的AVR 單片機(jī)ATMEGA88 是一款8 位單片機(jī)，內(nèi)部集成FLASH、RAM、EEPROM、內(nèi)部時(shí)鐘和ADC。該信號(hào)經(jīng)過(guò)限幅放大處理后，從PHY1076 的RX+/端輸出差分電壓串行數(shù)字信號(hào)。 ，具有外圍電路簡(jiǎn)單，控制電路只需要普通的8位單片機(jī)就可以實(shí)現(xiàn)的特點(diǎn)。由于涉及到高速電路設(shè)計(jì)、精密機(jī)械加工和光學(xué)設(shè)計(jì)，光收發(fā)器的成本占據(jù)了光纖通信系統(tǒng)和的重要部分，而較高的光收發(fā)器價(jià)格成了制約光纖接入推廣的瓶頸。進(jìn)一步降低光收發(fā)器的成本將有利于光接入的應(yīng)用推廣，加快光進(jìn)銅退的步伐。本文主要研究了PHY1076 的性能，選擇了ATMEL 公司的ATMEGA88 單片機(jī)進(jìn)行控制，設(shè)計(jì)出光收發(fā)器樣品，并進(jìn)行了性能測(cè)試， 光收發(fā)器。3) 控制及DDM 部分：PHY1076 是一款模擬數(shù)字混合芯片，其內(nèi)部包括多個(gè)模數(shù)(A/D)、數(shù)模轉(zhuǎn)換(D/A)器。無(wú)需任何外圍電路即可構(gòu)成系統(tǒng)，支持在線編程下載和單步調(diào)試。要維持穩(wěn)定的光功率則需要使用APC(自動(dòng)功率控制)電路。激光器的發(fā)光功率與電流成正比，激光器的陰極接到PHY1076 的Laser_bias 引腳。本設(shè)計(jì)中是通過(guò)外接單片機(jī)來(lái)根據(jù)溫度進(jìn)行寄存器設(shè)置，達(dá)到溫度補(bǔ)償?shù)哪康?。比較可行的辦法是尋找消光比與溫度變化的統(tǒng)計(jì)規(guī)律，然后通過(guò)外部控制器依規(guī)律進(jìn)行溫度補(bǔ)償。為了達(dá)到輸出光功率和消光比的穩(wěn)定性，就要根據(jù)溫度變化來(lái)響應(yīng)調(diào)節(jié)激光器的偏置電流和調(diào)制電流。收發(fā)器在實(shí)際的應(yīng)用環(huán)境下，重新加電后，就先從EEPROM 中把數(shù)據(jù)加載到RAM 區(qū)，然后就可以在全溫度范圍內(nèi)穩(wěn)定平均輸出光功率和消光比。C25186。5 總結(jié)經(jīng)過(guò)方案討論、硬件設(shè)計(jì)、軟件設(shè)計(jì)和樣品調(diào)試、測(cè)試。s AVR ATMEGA88 microcontroller to control and implement DDM functionality, coupled with the corresponding TOSA (transmitter optical ponents), ROSA (receiver optical ponents) and structural parts to designe a SFP optical transceiver which can work in 10km transmission distance. System block diagram shown in Figure 1:Figure 1 the internal structure of fiber optic transceivers map1) Transmitter works: Serial data signal from the TX + / side of the system input to the PHY1706 laser drive section in the form of differential signal terminal. After amplificationd, drive circuit converted to differential modulation current signal loading to the TOSA (transmitter optical ponents) to control the laser TOSA to emit light pulses, and couple into the fiber to sent to the remote.2) Receive part work principle : Optical pulse signal inputs to the ROSA (receiver optical ponents), and ROSA converts optical pulse signal into the differential voltage signal output to the PHY1076 the limiting amplifier section. After limiting amplified the signals ,it outputs differential voltage serial digital signals from the RX + / side of PHY1076.3) Control and DDM parts: PHY1076 is a mixed analogdigital chip, its internal includes multiple analogdigital (A / D) and digitalanalog converter (D / A) devices. Parameters on the transmit and receive paths are converted into digital stored in the State register for monitoring through ADC, and converts register value into analog for control by a DAC. These registers can be read and set by an external controlle. DDM (Digital Diagnostic Monitor) means that the fiberoptical transceivers is capable of monitoring parameters such as ransmitting power (Tx_power), received power (Rx_power), laser bias current (