摘要： 随着通信数据比特率不断提升，PAM4(四阶脉冲幅度调制)光发射机已经在超高速光纤通信系统中得到更广泛的应用。设计了一种包含NRZ（非归零）编码-RZ（归零）编码转换电路的PAM4光发射机，基于电流模逻辑增加了电路的工作速度和抗干扰能力。通过带自偏置可控延时电路实现了NRZ编码到RZ编码的转换，减小了长链路信号传输的色散效应。驱动器采用预驱动与主驱动级联的方式增大电路驱动能力，并通过串联电阻实现级间的共模电平匹配。电路设计采用0.13 μm SOI CMOS工艺，仿真结果表明在两路输入数据比特率为2.5 Gb/s，典型负载为25 Ω时，最大输出电流为120 mA，电流脉冲宽度为125 ps，PAM4眼图张开度良好。

中图分类号： TN432
文献标识码： A
DOI： 10.19358/j.issn.2096-5133.2020.06.010
引用格式： 李喜，林福江. 一种高速大电流的PAM4光发射机设计[J].信息技术与网络安全，2020，39(6)：53-57.

Design of a high-speed PAM4 optical transmitter with large current

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