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一種高速大電流的PAM4光發(fā)射機(jī)設(shè)計(jì)
《信息技術(shù)與網(wǎng)絡(luò)安全》2020年第6期
李 喜,,林福江
中國(guó)科學(xué)技術(shù)大學(xué) 微電子學(xué)院,安徽 合肥230026
摘要: 隨著通信數(shù)據(jù)比特率不斷提升,PAM4(四階脈沖幅度調(diào)制)光發(fā)射機(jī)已經(jīng)在超高速光纖通信系統(tǒng)中得到更廣泛的應(yīng)用,。設(shè)計(jì)了一種包含NRZ(非歸零)編碼-RZ(歸零)編碼轉(zhuǎn)換電路的PAM4光發(fā)射機(jī),基于電流模邏輯增加了電路的工作速度和抗干擾能力。通過帶自偏置可控延時(shí)電路實(shí)現(xiàn)了NRZ編碼到RZ編碼的轉(zhuǎn)換,減小了長(zhǎng)鏈路信號(hào)傳輸?shù)纳⑿?yīng),。驅(qū)動(dòng)器采用預(yù)驅(qū)動(dòng)與主驅(qū)動(dòng)級(jí)聯(lián)的方式增大電路驅(qū)動(dòng)能力,并通過串聯(lián)電阻實(shí)現(xiàn)級(jí)間的共模電平匹配,。電路設(shè)計(jì)采用0.13 μm SOI CMOS工藝,,仿真結(jié)果表明在兩路輸入數(shù)據(jù)比特率為2.5 Gb/s,典型負(fù)載為25 Ω時(shí),,最大輸出電流為120 mA,,電流脈沖寬度為125 ps,PAM4眼圖張開度良好,。
中圖分類號(hào): TN432
文獻(xiàn)標(biāo)識(shí)碼: A
DOI: 10.19358/j.issn.2096-5133.2020.06.010
引用格式: 李喜,,林福江. 一種高速大電流的PAM4光發(fā)射機(jī)設(shè)計(jì)[J].信息技術(shù)與網(wǎng)絡(luò)安全,2020,,39(6):53-57.

Design of a high-speed PAM4 optical transmitter with large current
Li Xi,,Lin Fujiang
School of Microelectronics,University of Science and Technology of China,,Hefei 230026,,China
Abstract: With the continuous improvement of the communication data bit rate, PAM4(four-level pulse amplitude modulation) optical transmitters are more widely used in ultra-high-speed optical fiber communication systems. A PAM4 optical transmitter including NRZ(non-return-to-zero) encoding to RZ(return-to-zero) encoding converter is designed in this paper. Based on current mode logic, it increases the circuit′s working speed and anti-interference ability. The self-biased controllable delay circuit is used to realize the converter from NRZ encoding to RZ encoding, which reduces the dispersion effect of long-link signal transmission. The driver uses a cascade of pre-driver and main driver to increase the driving capability, and achieves common-mode level matching between stages by a series resistor. The circuit design is based on 0.13 μm SOI CMOS process. Simulation results show that the maximum output current is 120 mA, the current pulse width is 125 ps, and the PAM4 eye pattern is open well at an input data rate of 2.5 Gb/s and a typical load of 25 Ω.
Key words : optical-fiber communication;PAM4(four-level pulse amplitude modulation),;optical transmitter,;driver circuit

隨著當(dāng)今社會(huì)通信速度與容量的迅速增長(zhǎng),光纖通信相比傳統(tǒng)的電通信開始展現(xiàn)出巨大優(yōu)勢(shì),。光發(fā)射機(jī)將輸入電壓信號(hào)轉(zhuǎn)化為能調(diào)制激光器發(fā)光的電流信號(hào),,其作用在整個(gè)光纖通信系統(tǒng)中起著極其重要的作用。

 在同等波特率下,,四階脈沖幅度調(diào)制(Four-level Pulse Amplitude Modulation,,PAM4)的比特率相比傳統(tǒng)的非歸零調(diào)制(Non-Return-to-Zero,NRZ)提高一倍,,增大傳輸效率的同時(shí)降低了成本,,PMA4技術(shù)已經(jīng)在超高速信號(hào)互連系統(tǒng)中得到了廣泛認(rèn)可。但PAM4在實(shí)際應(yīng)用上尚存在兩個(gè)問題:一是PAM4的發(fā)射機(jī)的調(diào)制電流不夠大,,使得激光器的消光比不夠大,,從而使信號(hào)在光纖傳輸時(shí)產(chǎn)生誤碼;二是目前輸入數(shù)據(jù)信號(hào)編碼通常采用NRZ編碼,,其調(diào)制產(chǎn)生的光信號(hào)在光纖傳輸中會(huì)顯著地受色散效應(yīng)影響造成碼間干擾,,不適應(yīng)長(zhǎng)距離傳輸。

本文提出的PAM4光發(fā)射機(jī)則能更好地適應(yīng)長(zhǎng)距離光通信:首先采用SOI CMOS工藝,,相比GaAs等工藝折中了成本與性能;其次輸出調(diào)制電流最大能達(dá)到120 mA,可以充分提高激光器的消光比,;另外,,設(shè)計(jì)了編碼轉(zhuǎn)換器,將輸入的非歸零編碼信號(hào)轉(zhuǎn)換為歸零型(Return-to-Zero,,RZ)編碼的信號(hào),,調(diào)制的光信號(hào)更能忍受在光纖傳播時(shí)的非線性和色散效應(yīng),從而更好地適應(yīng)長(zhǎng)距離光通信,。



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作者信息:

李  喜,,林福江

(中國(guó)科學(xué)技術(shù)大學(xué) 微電子學(xué)院,安徽 合肥230026)

 


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