Optical modules used in AAU

AAUs in 5G networks use optical modules, including colored 25G modules and industrial-grade modules, to transmit optical signals between AAUs and DUs, supporting high-speed, multi-wavelength fronthaul connections.

Function and Role

Optical modules in AAUs are responsible for transmitting optical signals between the AAU and fiber optic cables, enabling high-speed communication with Distributed Units (DUs) or Baseband Units (BBUs) in 5G networks . They allow multiplexing of RX and TX signals, supporting the same antenna path and enabling beamforming and signal filtering . In pre-transmission applications, colored optical modules implement passive Wavelength Division Multiplexing (WDM), allowing multiple AAUs to share a single fiber without interference .

Types of Optical Modules

1. Colored 25G Optical Modules
   • Used in 5G pre-transmission and fronthaul applications.
   • Support single-rate 25G or dual-rate 10G/25G operation.
   • Cover a 6-wavelength range (1270–1370 nm), enabling multi-wavelength transmission over a single fiber .
   • Typical deployment: ordinary 5G base stations use six modules (three bidirectional transceivers for three sectors), while high-bandwidth stations may require 12 modules .
2. Industrial-Grade Optical Modules
   • Designed for outdoor AAU deployment to withstand harsh environmental conditions such as high/low temperatures and humidity .
   • Include hardened active optical cables (HAOC) or liquid-cooled modules for high-density DU equipment rooms .
   • Ensure reliable fronthaul performance in extreme conditions.

Deployment Considerations

• Integration with AAU: Optical modules are installed in AAU ports and connected to fiber cables, often alongside RUs and MUs in the AAU logical structure .
• Environmental resilience: Outdoor AAUs require modules that can tolerate temperature fluctuations and mechanical stress .
• Network design: The number of modules depends on base station type, sector count, and bandwidth requirements .
• Compatibility: Modules must support the eCPRI or CPRI interfaces used for fronthaul connections and comply with 5G standards .

Summary

Optical modules in AAUs are critical for high-speed, reliable 5G fronthaul and pre-transmission. They include colored 25G modules for multi-wavelength WDM and industrial-grade modules for outdoor resilience, ensuring efficient signal transmission between AAUs and DUs while supporting the physical layer processing integrated within the AAU .