One Case Of Signal Integrity Design For 25Gbps Backplane And Optical Module Interface

The Internet,Cloud Computing,Big Data and 5G Communication have flourished in recent years,accelerating the construction of communication network infrastructure,and significantly increasing the competition in the electronic communication equipment industry.Data Center Computing,Storage,and Network performance improvements have become key to addressing these trends and improving the ability to deliver basic services.As the speeds increasing from 10 Gbps to 25 Gbps,the design challenges for high-density and high-speed Ethernet Switch and Router systems increase.On the one hand,it is necessary to ensure the reliability of the system,on the other hand,the control of the cost is more stringent.When high-speed signals are transmitted over long links,the signal quality will be seriously distorted.And the system reliability will be reduced due to factors such as loss,reflections,and crosstalk.The signal integrity of the 25 Gbps highspeed link has become a subject that many enterprises and research institutions at home and abroad rush to break through.The direction studied in this paper is the signal integrity design in 25 Gbps highspeed systems,to solve the problem that the Backplane system and Optical module interface implemented in a low-cost solution.Firstly,the important and difficult parts of signal integrity theory are introduced,including frequency-dependant characteristics of dielectric materials,S-parameter passivity and causality checking algorithms,and equalization techniques commonly used in high-speed digital.And a tool is designed to evaluate the high-speed passive channel quality and calculate the optimal equalization parameters.Secondly,the main factors affecting the passive channel of 25 G Backplane are studied,including the characteristics of PCB materials,the modeling and optimization of vias and capacitor pads.Then,developed a tool to automatic model the capacitive pad in HFSS with VBScript.Channel analysis,COM analysis and signal simulation are performed to ensure the quality of the Backplane.The Design of Experiments method is used to find the optimal FFE coefficient and analyze the influence of PCB processing tolerance on signal quality.Finally,the 25 G optical module interface(CAUI-4 Chip-toModule)system is analyzed,then Retimer is adopted to realize the low-cost and longdistance transmission system.And the system performs very well from validation results.25Gbps Backplane and optical communication technologies are widely used in enterprise-class high-performance switches and routers.However,due to the difficulty and big challenges in high-speed serial channel design,manufacturers that can launch 25 Gbps products in China can be described as rare.The research of high-speed serial bus analysis method in this thesis will provide reference for PCB design and system design of 25 Gbps Backplane and Optical interface.