Design Of SFP56 50Gbit/s 40km Duplex Optical Module Based On PAM4 Modulation Technology

With the popularization of the fifth-generation mobile communication technology(5G)network and the comprehensive construction of 5G base stations in the past two years,all fields of the whole society are eager to develop the communication network to the direction of higher transmission rate,larger information capacity and lower delay.Optical module is a core component in the construction of communication network.Although the appearance of four channel small pluggable(QSFP28)50Gbit/s optical module in the early stage has temporarily solved the problem of no optical module available in the construction of mobile network infrastructure,with the comprehensive construction of 5G network,the optical module is not available.This kind of optical module is no longer suitable for use because of the problems of power consumption and cost.Therefore,a better 50Gbit/s optical module solution is proposed,which can not only meet the demand of communication network for bandwidth,but also reduce the cost and power consumption,so it is very meaningful for the construction of emerging networks.Based on the actual situation,this thesis analyzes the conversion from NRZ modulation technology to PAM4 modulation technology and their advantages and disadvantages and introduces the IEEE 802.3cd protocol about 50 GE Ethernet related standards.According to the protocol requirements and the design scheme of QSFP28 50Gbit/s optical module,using electro-absorption modulation laser(EML),thermoelectric cooler(TEC)and avalanche photodiode(APD)as the core components,a small form-factor pluggable(SFP)50Gbit/s optical module solution with strong environmental temperature adaptability,high receiving sensitivity and able to meet the needs of 40 km information transmission is proposed.The advantages and disadvantages of the two design schemes are compared.For SFP56 50Gbit/s optical module,the design principle is analyzed in detail,the optimization scheme is proposed,and the feasibility is verified.The main contents of this study are as follows:(1)According to the relevant parameter requirements of 50 GE specified in IEEE802.3cd protocol and the basic principle of PAM4 modulation technology,the overall hardware design scheme of SFP56 50Gbit/s optical module is completed by referring to the design scheme of QSFP28 50Gbit/s optical module.(2)How to improve the performance of the module is explored from the generation,transmission and reception of PAM4 electrical signals,including selecting new coding methods,changing the transmission distance of PAM4 electrical signals and changing the parameters that affect the performance of the laser,etc.The change of module performance before and after optimization is obtained by designing comparison experiments through the control variable method,and the final optimization scheme is put forward.(3)In the laboratory environment,the optimized module is tested according to the test items and test procedures specified in the protocol,which are specifically divided into: normal temperature test,high and low temperature test,and 40 km fiber is added to the optical link for test.The test results show that the parameters of the module can meet the requirements of the protocol and have a large margin.