Fast Ethernet (FE), developed in 1995, provides data transfer rates up to 100 Mbps, an enhancement of 10 megabits (Mbps) Ethernet. Although the demands of modern high-speed development have led to 100M Ethernet being replaced by Gigabit Ethernet or even 10G Ethernet in many infrastructures, edge products that support 10M/100M/1G are still common. This post will focus on Fast Ethernet standards, especially 100BASE-T, 100BASE-TX, 100BASE-FX, etc.

What is 100BASE-T/100BASE-TX?

100BASE-T is a Fast Ethernet standard that supports 100 Mbps based on a Twisted Pair Ethernet cable. It is an upgrade of 10BASE-T, increasing the speed from 10 Mbps to 100 Mbps. IEEE802.3 specified three 100BASE-T Ethernet PHYs, including 100BASE-TX, 100BASE-T2, and 100BASE-T4. The figures in T2 and T4 refer to the number of pairs of Twisted Pair cables used for transmission. 100BASE-T2 and 100BASE-T4 using Cat 3 cables are rarely deployed in the market; thus, 100BASE-T is often referred to as 100BASE-TX. And 10GBASE-T optical modules are now available in the market.

What is 100BASE-FX?

Different from 100BASE-TX, 100BASE-FX is the FE standard, delivering 100Mbps over fiber optic cables. For transmission, 100BASE-FX adopts two fibers for transmitting and receiving. The market for 100BASE-FX optical transceivers has differentiated into multiple standards to cope with different distance usage scenarios, such as 100BASE-SX, 100BASE-LX, 100BASE-EX, 100BASE-ZX, 100BASE-EZX, 100BASE-BX, etc.

Similar 100BASE Term Explained

100BASE-SX is used for short-reach transmission. It supports 100Mbps up to 2km over multimode fiber (MMF) at the wavelength of 1310nm (550m over MMF at 850nm). 

100BASE-LX is used for long-distance transmission. It supports 100Mbps up to 10km/20km over single-mode fiber (SMF) at the wavelength of 1310nm. 

100BASE-EX is used for extended-reach transmission. It supports 100Mbps up to 40km over single-mode fiber (SMF) at 1310 nm wavelength. 

100BASE-ZX  is used for extremely long transmission. It supports 100Mbps up to 80km over single-mode fiber (SMF) at 1550 nm wavelength. 

100BASE-EZX is used for ultra-long reach transmission. It supports 100Mbps up to 120km over single-mode fiber (SMF) at the wavelength of 1550nm. 

100BASE-BX is a simplex bidirectional FE standard that uses only a single fiber for transmitting and receiving signals. The 100BASE-BX10 and 100BASE-BX20 are both for long-distance transmission, providing up to 10km and 20km of 100Base-BX throughput over single-mode fiber (SMF) using 1310nm/1550nm wavelengths via LC simplex connectors. 

100BASE-FX vs 100BASE-TX, What is the Difference?

The table below lists the key parameters of 100BASE-FX vs 100BASE-TX and compares other 100BASE terms.

As can be seen from the table above, the differences between 100BASE-FX and 100BASE-TX are mainly the following:

Connectors: 100BASE-TX uses RJ-45 connectors, while 100BASE-FX adopts duplex LC/SC/FC/ST connectors.

Media: 100BASE-TX transit data via twisted pair copper cables. 100BASE-FX uses multimode-mode fiber as the transmission medium.

Max Transmission Distance: 100BASE-TX provides a maximum transmission distance of up to 100 meters. It is used for short-range applications restricted by the copper transmission medium. The transmission medium of 100BASE-FX is fiber, which can support longer distances. 100BASE-FX provides a maximum transmission distance of up to 2 kilometers.

FAQs on 100BASE SFP

What type of fiber does 100Base-FX require?

Refer to IEEE 802.3ah, 100Base-FX is multimode. 100Base-FX devices such as transceivers or media converters often use duplex multimode fiber working at 1310 nm wavelength. LC connectors are the most common interface type.

What are the application differences between 100BASE-FX vs 100BASE-TX?

100BASE-TX is commonly used in office and home networks where electromagnetic interference is low. It is ideal for connecting devices like computers and printers within a LAN, and its affordability and simple installation make it popular in these environments.

100BASE-FX, on the other hand, is better suited for long-distance connections, such as between buildings or across large campuses. It is also used in areas with high electromagnetic interference, where fiber optic cables offer better protection. Typical use cases include backbone connections in enterprise networks and high-speed links in data centers.

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