Compared with the 4G network, the 5G network has a comprehensive improvement in performance and also gives the 5G network the feasibility of application in more scenarios. It has breakthroughs and applications in high speed, low latency, ubiquitous networks, and the Internet of Everything. There are still some technical difficulties in today’s 5G network. The construction of the 5G network in some areas has already begun.
In the construction of the 5G network, the design and management of the access network are obviously different from the 4G network. 5G access requires much denser base stations and greater communication capacity than 4G networks. In the transformation of the old network, the transformation of the 5G network is much more difficult than that of the 4G network. In addition to the problem of insufficient fiber core resources, it is difficult for 5G equipment to be directly superimposed on 4G base stations. In the face of the problem of fiber core resources, the planning and construction of new optical cable lines have a high cost and a long period of time, and it is difficult to reconstruct some old optical cable links. Considering the bandwidth requirements of communication equipment, the low-cost and most effective way is to use of higher-speed optical modules and interfaces that can directly improve the communication speed of a single-core fiber. Replace 6G and 10G optical modules in 4G base stations and 4G transmission equipment, such as SFP+ and XFP optical modules, with SFP28, DSFP28, QSFP+, and QSFP28 optical modules to directly improve network performance.
In order to save optical cable resources and reduce the cost of the fronthaul network, wavelength division multiplexing technology is also used in the 5G fronthaul network. It also reduces the construction difficulty of networking. However, it is difficult for this type of module to add passive devices to the optical path to reduce the deployment of active devices.
The dual-fiber optical module using CWDM (Coarse Wavelength Division Multiplexer, Coarse Wavelength Division Multiplexer) technology can be solved. The passive CWDM solution has low cost, rapid opening, and a relatively mature solution, which can not only ensure the reliability of data transmission and bandwidth requirements, and can reduce the demand for optical fibers and active equipment, increase the flexibility of deployment, and facilitate the design of a pure digital signal transmission network using the CPRI protocol. Among the existing optical module products, the QSFP28 type 4-channel optical module has a high packaging density, which best meets the application requirements of the access network.
In the current stage of 5G network design and deployment, in order to reduce the occupation of valuable public resources by base station equipment, reduce maintenance pressure, and improve equipment utilization, BBU equipment is centrally deployed to form a BBU pool. The BBU transmits and receives optical signals of corresponding wavelengths through different optical modules to realize packet control and data communication with front-end equipment, effectively saving fiber link resources.
At present, there is another type of application scenario. A single device needs to use a high access network bandwidth, such as 4K live broadcast, AR live broadcast, etc. The front-end equipment collects a large amount of data and information and has high real-time performance. Single-wave 25Gpbs optical communication requires parallel multiple groups. to meet the demand. Although there is PAM (Pulse Amplitude Modulation) technology with higher modulation efficiency, in theory, the cost of an optical module using a single-wave 25Gpbs PAM4 modulation signal will be lower, but the reliability of one PAM4 signal is not as high as that of four NRZ signals. , and the PAM4 modulation chip is currently unable to operate continuously and reliably in harsh environments. Under the extreme working environment of the access network, it is one of the more feasible solutions to use 4WDM optical modules to build a high-performance access network.
