Although there are no less than 10 application models for 400G, from the perspective of data center applications, the models for mainstream applications of 400G in the future will not exceed the above four types. According to the evolution law of the backbone of data center, the supporting application distance of multi-mode fiber can basically meet the needs of 90% of the backbone applications of data center. From the current situation of domestic and foreign Internet giants, 400gbase-sr8 is a relatively promising application model.