The optical module in a BBU is located inside the climate-controlled equipment room, connecting the BBU to the RRU via optical fiber.

Location and Placement

The BBU (Baseband Unit) is typically installed in an indoor, climate-controlled equipment room or base station machine room to ensure stable operation and protect sensitive electronics from environmental factors such as temperature fluctuations and humidity . The optical module is integrated into the BBU and serves as the interface for high-speed data transmission to the RRU (Remote Radio Unit), which is mounted outdoors on the telecom tower .

Connection to RRU

The optical module converts electrical signals from the BBU into optical signals, which are transmitted over optical fiber to the RRU. At the RRU, the optical signals are converted back into electrical signals for radio transmission . In 4G networks, optical modules typically range from 1.25G to 10G, while in 5G networks, higher-speed modules such as 25G SFP28 are used . The optical module is usually installed in SFP or SFP+ slots within the BBU cabinet, with proper cable management using fiber binding straps and winding pipes to maintain signal integrity .

Environmental Considerations

Since the BBU is indoors, the optical module operates under controlled temperature conditions, unlike RRUs which require industrial-grade optical modules capable of withstanding -40℃ to 85℃ due to outdoor exposure . This indoor placement ensures reliable performance, easier maintenance, and protection from environmental stress.

Summary

• BBU Location: Indoor equipment room or base station machine room
• Optical Module Placement: Inside the BBU, typically in SFP/SFP+ slots
• Function: Converts electrical signals to optical signals for transmission to RRU
• Connection: Linked to RRU via optical fiber, supporting 4G or 5G data rates
• Environmental Advantage: Indoor placement ensures stable operation and easier maintenance This setup allows the BBU to efficiently process signals while the optical module ensures high-speed, long-distance communication with the RRU.