Research On Bidirectional Optical Transceiver Based On PAM4 Modulation

Under the promotion of various applications such as super clear video,VR game and Internet of things,5G communication is under construction in full swing.The demand for bandwidth of 5G base stations is greatly increased,but the coverage of base stations is small,and the density of base stations is expected to be 5-10 times that of 4G era,resulting in a substantial increase in the consumption of optical modules in 5G networks.At the same time,the global data center traffic keeps growing at a high speed,and the proportion of cloud data center traffic is expected to increase continuously.Since optical modules are indispensable components in data centers,the increase in the number of data centers will directly drive the demand for optical modules.While the number of optical modules in the market has greatly increased,the demand for their transmission rate is also increasing.NRZ modulation from single wave 25 Gbps to continue to upgrade is difficult,and accompanied by cost,dispersion and many other problems.PAM4(4 Pulse Amplitude Modulation)solves the lifting problem of optical devices,and can transmit twice the rate of NRZ on the basis of the original 25 optical devices.The design scheme of the 50 G QSFP28 PAM4 BIDI transceiver presented in this thesis has many advantages such as low cost per unit bit,small package and high utilization rate of fiber resources,which has a very broad prospect in 5G communication.This thesis mainly includes the following six parts: first,it introduces the development status and trend of 5G communication,as well as the demand and prospect of the optical module in 5G;Then the advantages and disadvantages of PAM4 modulation are analyzed.Then,a general scheme of 50 G QSFP28 PAM4 BIDI optical transceiver is proposed,and each functional unit is designed.Then the design and verification of PCB transmission line are introduced.Furthermore,the performance of optical module is tested and adjusted according to the situation.Finally,the whole design and development process of 50 G QSFP28 PAM4 BIDI optical transceiver is summarized and prospected.After optimization,50 G QSFP28 PAM4 BIDI transceiver can achieve extinction ratio of 4d B and TDECQ of about 1d B at the wavelengths of 1330 nm and 1270 nm.OMA sensitivity of the module can reach-11 d Bm at room temperature under the condition of bit error rate of 2.4E-4.Its performance indicators meet the standard of IEEE 802.3cd LR,which can meet the transmission requirements of 50 GE Ethernet.