What are the uses of RRU optical modules

RRUs typically use optical modules such as 1.25G, 2.5G, 6G, or 10G SFP/SFP+ modules to connect to BBUs via fiber, often employing CWDM for efficient long-distance transmission.

Overview

Remote Radio Units (RRUs) are deployed near antennas to handle radio signal transmission and reception, converting digital signals from the Baseband Unit (BBU) into RF signals and vice versa. To connect RRUs to BBUs, high-speed optical modules are used over fiber optic links, ensuring low latency and reliable communication .

Types of Optical Modules

In 4G networks, the commonly used optical modules include:

• 1.25G optical modules – suitable for lower-capacity links or short distances.
• 2.5G optical modules – standard for medium-capacity RRU-BBU connections.
• 6G optical modules – used for higher throughput requirements.
• 10G optical modules – for high-capacity or aggregated RRU connections . These modules are typically SFP or SFP+ form factors, compatible with single-mode fiber (OS2) for long-distance transmission.

Wavelength Division Multiplexing (WDM)

To optimize fiber usage, especially when multiple RRUs share limited fiber resources, Coarse Wavelength Division Multiplexing (CWDM) is employed. CWDM allows multiple optical signals at different wavelengths to travel over a single fiber, reducing the number of fibers required between the BBU and multiple RRUs. The BBU connects to a CWDM multiplexer using a CWDM-compatible optical module, which then transmits to the RRU using another CWDM optical module .

Fiber Requirements

RRUs generally require 2–6 core optical fibers depending on the configuration and data rate. The optical modules ensure that the digital signals are transmitted efficiently over these fibers, maintaining signal integrity and supporting high-speed data transfer for LTE or 5G services .

Summary

Optical modules are critical for RRU operation, providing the high-speed, low-latency link between the RRU and BBU. The choice of module depends on the required data rate, distance, and network architecture, with CWDM often used to maximize fiber efficiency in distributed base station deployments. These modules enable RRUs to support advanced wireless technologies while maintaining reliable connectivity.