You can connect Ethernet switches over a single fiber strand using BiDi SFP modules or single-fiber media converters, enabling bidirectional communication without requiring duplex fiber.

Using BiDi SFP Modules

BiDi (Bi-Directional) SFP modules allow a single fiber strand to carry both transmit and receive signals simultaneously by using different wavelengths for each direction. This is ideal when fiber availability is limited or installing new fiber is costly. Each switch must have an SFP port compatible with BiDi modules, and the modules must be paired correctly with matching wavelengths (e.g., 1310 nm TX / 1550 nm RX on one end and reversed on the other) to ensure proper communication .

Single-Fiber Media Converters

If your switches lack SFP ports, single-fiber media converters can bridge copper Ethernet to fiber and enable bidirectional communication over one strand. These converters take the Ethernet signal, convert it to optical, and transmit it over a single fiber using WDM (wavelength division multiplexing). Both ends must use matched A/B pairs to maintain proper TX/RX alignment . This approach also extends the network beyond the 100-meter limitation of standard Ethernet cabling.

Network Topology Considerations

• Star Topology: All switches connect to a central core switch. Each link can use a single fiber with BiDi SFPs, but the core switch must have enough SFP ports to accommodate all connections .
• Daisy Chain or Ring Topology: For distributed networks, a single fiber can connect nodes in a ring using switches with two SFP ports, allowing traffic to pass from one node to the next. However, Ethernet does not natively support daisy-chaining over fiber without proper switching hardware, and care must be taken to avoid loops .
• Distance: Single-mode fiber with BiDi modules or media converters can span several kilometers, making it suitable for campus or metro networks .

Practical Tips

1. Ensure all switches support the required SFP modules or use compatible media converters.
2. Verify wavelength pairing for BiDi modules to prevent signal conflicts.
3. Plan the topology carefully to avoid loops and congestion; consider using spanning tree protocol (STP) for redundancy.
4. Test the setup in a lab environment before full deployment, especially for long-distance or multi-node networks . By using BiDi SFPs or single-fiber media converters, you can efficiently connect multiple switches over a single fiber strand while maintaining high-speed, reliable Ethernet communication.