Is RRU cascading an optical fiber cable

Yes, RRU cascading can be implemented using optical fiber cables via CPRI connections.

RRU cascading refers to connecting multiple Remote Radio Units (RRUs) to the same SFP port of a baseband unit (BBU or UBRI board) using CPRI (Common Public Radio Interface) connections, which are typically carried over optical fiber cables . This allows more than one RRU to share the same interface port, enabling efficient deployment in sectors with multiple RRUs.

How RRU Cascading Works

• Connection Type: The cascading connection uses CPRI fiber or CPRI cable to link RRUs to the baseband unit .
• Scenario: When multiple RRUs are deployed in the same sector or coverage area, cascading allows them to operate through a single SFP port, reducing the number of required ports on the BBU .
• Fiber Role: Optical fiber is preferred because it supports high-speed, long-distance transmission with minimal signal loss, which is essential for maintaining the integrity of digital signals between the BBU and RRUs .

Additional Context

• RRUs are installed near antennas to minimize RF cable losses and are connected to the BBU via bi-directional optical fiber links .
• The optical interface supports both downlink and uplink signals, converting digital signals from the BBU into RF signals for transmission and vice versa .
• Cascading over fiber ensures that multiple RRUs can be efficiently managed without additional RF ports, which is particularly useful in dense urban deployments or multi-sector configurations . In summary, RRU cascading is not a coaxial RF connection but a digital interconnection using CPRI over optical fiber, enabling multiple RRUs to share a single baseband interface while maintaining high-speed, low-loss communication.