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7.1 | |
10-Mbps and 100-Mbps Ethernet | |
| 7.1.8 | |
100BASE-FX |
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At the time copper-based Fast Ethernet was
introduced, a fiber version was also desired. A fiber vervsion could
be used for backbone applications, connections between floors and
buildings where copper is less desirable, and also in high noise
environments. 100BASE-FX was
introduced to satisfy this desire. However, 100BASE-FX was never
adopted successfully. This was due to the timely introduction of
Gigabit Ethernet copper and fiber standards. Gigabit Ethernet
standards are now the dominant technology for backbone installations,
high-speed cross-connects, and general infrastructure needs.
The timing, frame format, and
transmission are all common to both versions of 100 Mbps Fast
Ethernet. 100BASE-FX also uses 4B/5B encoding. In Figure
Figure
200 Mbps transmission is possible because of the separate Transmit and Receive paths in 100BASE-FX optical fiber.
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notice the
highlighted waveform in the example. The top waveform has no
transition, which indicates that a binary 0 is present. In the second
waveform, a transition is in the center of the timing window. A binary
1 is represented by a transition. In the third waveform, there is an
alternating binary sequence. In this example it is more obvious that
no transition indicates a binary 0 and the presence of a transition is
a binary 1. 
summarizes
a 100BASE-FX link and pinouts. Fiber pair with either ST or SC
connectors is most commonly used. 
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