What is 100Base-FX?

100BASE-FX is the technical name for Fast Ethernet over fiber optic cables. It is a version of Fast Ethernet carrying data traffic at 100 Mbps (megabits per second) in local area networks (LAN). It was launched as the IEEE 802.3u standard in 1995. Here, 100 represents the maximum throughput of 100 Mbps, BASE denotes use of baseband transmission, and FX indicates the use of optical fibers in Fast Ethernet.

The 100BASE-FX Physical Medium Dependent (PMD) sublayer is defined by the Fiber Distributed Data Interface (FDDI) standard, providing a reliable foundation for high-speed data transmission over fiber optic networks.

Key Properties

• Dual fiber configuration − Uses two pairs of optical fibers for full-duplex communication. One pair transmits frames from hub to device, while the other transmits from device to hub.

• Extended range − Maximum distance between hub and station is 2000 meters, significantly longer than copper-based alternatives.

• Data transmission − Operates at 125 Mbps signaling rate to achieve 100 Mbps data throughput.

• Encoding scheme − Uses NRZ-I (Non-Return-to-Zero Inverted) encoding combined with 4B/5B block coding for reliable data transmission.

Typical Network Implementation

In most Fast Ethernet applications, fiber optics provides long-distance backbone connectivity, while individual devices connect using twisted pair copper wires (100BASE-TX). This hybrid approach requires media converters to bridge between fiber and copper segments, offering both the extended range of fiber and the cost-effectiveness of copper for end-device connections.

Advantages

• Electromagnetic immunity − Optical fibers are immune to electromagnetic interference, ensuring reliable data transmission.

• Extended transmission distance − Supports up to 2000m without signal degradation, far exceeding copper-based solutions.

• Security − Fiber optic cables are difficult to tap, providing better network security compared to copper cables.

Conclusion

100BASE-FX provides reliable 100 Mbps Fast Ethernet connectivity over fiber optic cables with extended range capabilities up to 2000 meters. Its immunity to electromagnetic interference and enhanced security make it ideal for backbone connections in enterprise networks.