100Base TX and 100Base FX: Similarities and Differences Offered

Published on Updated on July 03, 2024

Ethernet technologies have significantly evolved over the years. The term "Fast Ethernet" became widely known in 1995, when it was covered under the IEEE802.3u standard.

Fast Ethernet is designed to carry traffic at the rate of 100 Mbit/s at the physical layer in local area networks (LANs). Based on this speed, the cables are termed as 100Base-TX. For a long time, these cables were referred to as 100Base-T cables.

The 100Base-TX cable has replaced the earlier versions of coaxial cables – 100Base-T and 100Base-2. Along with these, there are 100Base-FX cables available, too. At times, it may be confusing for people to differentiate between 100Base-TX and 100Base-FX cables.

This post offers insights on these two types of cables and their increasing popularity in various applications and more.

100Base-TX and 100Base-FX

Breakdown of 100Base-TX/FX

Before going through the comparisons between 100Base-TX and 100Base-FX, we are going to break the "100Base-TX/FX" into parts to make it easier to understand:

  • 100: In 100Base, "100" stands for 100 Mega Hertz or 100 MHz, which translates to 100 Mbit/seconds. This 100 Mbit/seconds theoretically points to 12 Mbps; however, you may not get more than 4 Mbps in real.
  • Base: This is the term for Baseband, which is mainly used to depict the communication used by the Ethernet Network. It depicts that the cable is using all the available bandwidth to transmit the data. Against this, in broadband the cable usually shares the bandwidth. This is one of the reasons why users may face some slowdown at times when multiple users are connected to the network. Although Ethernet users may also experience some slowdown, the frequency is lesser compared to broadband.
  • TX: The term "TX", sometimes referred to as "T", is a term for Twisted Pair, which is a type of physical signal carried by the cable. This TX shows that the application is utilizing CAT5 UTP cables, where two pairs of copper wires are being used to support a speed of 100 Mbit/s.
  • FX: In "FX", the cable uses two pairs of fiber to support more than 100 Mbps. This cable can support a speed up to 2 km.

What is 100BASE-TX?

The 100Base-TX cables operate over two pairs of copper wires within a Cat5 or better cable. It can support data speeds up to 100 meters and must possess a minimum recommended node length of 2.5 meters between two cables.

What is 100BASE-FX?

100BASE-FX is a Fast Ethernet standard that supports 100 Mbps (Megabits per second) data speed over fiber optic cables. This cable is an ideal choice for long-distance applications.

What is the Difference between 100Base-TX and 100Base-FX

The following pointers will help you understand these two technologies better and how they are similar and dissimilar in many ways:

  • Pair of Wires: As said before, 100Base-TX uses two pairs of UTP category 5 wires for signal transmission. At times, it may also use two unshielded twisted pair (STP) type 1 wires. Against this, 100Base-FX uses two pairs of optical fibers for data transmission. Both types of wires assure full-duplex transmission, where one pair of wires transmits the frames from the hub to the device, and the other pair from the device to the hub.
  • Data Rates: Both these wires possess data rates of 125 Mbps. The maximum value of the fundamental frequency of 100Base-T is 31.25 MHz.
  • Encoding and Decoding: Of these, 100Base-T uses the MLT-3 scheme for encoding and decoding. They also use 4B/5B block coding.
  • MLT-3 Encoding: MLT-3 encoding refers to the Multi-Level Transmit, which is a popular signaling method that uses three voltage levels: -1, 0, +1, 0. They move through these voltage levels sequentially. 4B/5B block coding contributes to DC equalization and spectrum shaping. Against this, 100Base-FX uses the NRZ-I encoding scheme along with 4B/5B. The NRZ-I encoding refers to non-return-to-zero, which is a line code in binary code. The pulses in this encoding scheme offer higher energy than the return-to-zero (RZ) code.

100BASE-TX vs. 100BASE-FX: Comparison Summary











Cat 5








Device Type

Media Converter

Media Converter, Optical Transceiver

System Cost



Along with the cables, you need to choose the network devices that are compatible with them. VERSITRON provides various types of conversion devices like 10/100Base-TX to 100Base-FX Industrial Fast Ethernet to Fiber Media Converter, 10/100Base-TX to 100Base-FX Fiber Optic Media Converter, Multimode SC, and so on. The company also provides industrial switches and several other Ethernet devices, which have been installed in various applications across the world.

Rich Tull

Rich Tull
R.W. Tull is the President of Versitron, a leading technology company specializing in data communication and networking solutions. With expertise in Guiding network switches and media converters, R.W. Tull has played a pivotal role in driving Versitron's success. His deep understanding of these technologies has enabled the company to provide innovative and reliable solutions to clients. As a visionary leader, He ensures that Versitron remains at the forefront of the industry, delivering cutting-edge networking solutions that enhance data communication efficiency.
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