WDM is a mandatory technology for 5G fronthaul.

For the massive multiple-input, multiple-output antenna (Massive-MIMO) technology adopted by 5G new wireless networks, some physical layer functions can also be moved down to the Active Antenna Unit (AAU) for implementation, thus creating a new network connection requirement - the fronthaul network, which is the transmission channel connecting the AAU and the DU (Distributed Unit), and the interface is eCPRI (enhanced). Common Public Radio Interface), which needs to meet the transmission requirements of >25Gbit/s with high bandwidth and low latency. In addition, compared with 4G, 5G uses higher frequencies, and the coverage of a single base station is smaller than that of 4G, which means that 5G fronthaul networks need denser networking to achieve more base station coverage.

The most essential connection needs of the 5G fronthaul network are > high-speed, large-granularity and direct and efficient transparent transmission of 25 Gbit/s. The optical fiber direct drive solution is a point-to-point direct connection solution between the AAU and the DU through the fronthaul optical module and optical fiber. According to the general demand calculation, an ordinary access point needs 36~48 optical fibers, a C-RAN (Centralized/Collaborative/Cloud Radio Access Network) area will need more than 120 fiber cores, and the backbone optical cable needs more than 300 fiber cores.

      In order to reduce the construction cost of optical fiber and save optical fiber consumption, a single optical fiber can be easily provided with 

18 waves, 32 waves, 40 waves, and even 80 waves/96 waves through WDM technology, which greatly saves the use of access optical fibers 

and solves the pain point problem of lack of access optical fibers.

      WDM is a typical point-to-point topology, both upstream and downstream transmission use independent, different colors of transparent wavelength channels, do not need to carry out any special electrical layer protocol processing, and do not need to dynamically allocate bandwidth between channels, so the complexity of the system is greatly reduced, and the transmission efficiency of transparent transmission has also been greatly improved. While providing high-speed direct channels with higher bandwidth, the transmission latency is the lowest of all fronthaul solutions.

      Therefore, WDM technology will become the best choice for 5G fronthaul technology.

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