Facing the increasing demand for computing power, Nokia Shanghai Bell helped China Unicom to complete the building of a 400G C+L ultra-high speed transmission experimental network. 400G WDM/OTN ultra-high-speed transmission technology is steadily improving. In order to better meet the rising demand for the backbone network and the intra-province ultra-high-speed bandwidth, under the unified planning and guidance of the Network Department of China Unicom Group, China Unicom Cloud Network Center, China Unicom Shandong, China Unicom Research Institute, China Information Technology Designing & Consulting Institute (CITC) and Nokia Shanghai Bell jointly built a 400G(PCS-16QAM)/C+L transmission experimental network, to serve the development of digital economy in China through green and energy-saving networks with greater capacity and better performance.