Optical module on BBU

BBUs typically use SFP, SFP+, and higher-speed optical modules to connect to RRUs, with speeds ranging from 1.25G in 4G networks to 25G in 5G networks.

Optical Modules in 4G Networks

In 4G networks, BBUs commonly use 1.25G SFP optical modules (gigabit modules) and 10G SFP+ optical modules. The 1.25G SFP modules operate at a wavelength of 850nm, transmit over multimode fiber, and support distances up to 550 meters with power consumption under 1W. The 10G SFP+ modules also use 850nm wavelength, transmit over multimode fiber, and support distances up to 300 meters with similar power efficiency . Other 4G options include 2.5G and 6G optical modules depending on network requirements and distance between BBU and RRU .

Optical Modules in 5G Networks

For 5G networks, BBUs generally use 25G optical modules to handle higher data rates and increased network demands. These modules are designed to support the high-speed fronthaul connections required for 5G, often using enhanced CPRI (eCPRI) protocols for low-latency, high-throughput communication .

Connection and Deployment

BBUs connect to RRUs via optical fibers using these modules. The optical modules are inserted into SFP/SFP+ slots on the BBU, and the fiber is connected to the RRU. In some deployments, CWDM (Coarse Wavelength Division Multiplexing) optical modules are used to optimize fiber usage and support multiple RRUs over a single fiber pair . The choice of module depends on network speed, distance, and the number of RRUs connected.

Summary

• 4G BBU-RRU connections: 1.25G SFP, 2.5G, 6G, 10G SFP+ modules
• 5G BBU-RRU connections: 25G optical modules
• Fiber type: Multimode for short distances, single-mode for longer distances or CWDM setups
• Protocols supported: CPRI and eCPRI for high-speed fronthaul communication These optical modules ensure reliable, high-speed communication between BBUs and RRUs, supporting both current 4G networks and the evolving 5G infrastructure.