Information Technology Reference
In-Depth Information
Fiber cables may also fracture when they receive a sharp impact. Fiber-optic
light sources, meters, and even optical time-domain reflectometers (OTDRs) may be
required to troubleshoot a fiber-optic installation.
Fast Ethernet 100BaseFX and SX Wiring
The 100BaseFX standard allows Ethernet transmission at 100 Mbps using multi-
mode fiber at the long wavelength, 1300 nm. The 100BaseFX standard allows links
of up to 2000 m and is widely used both in high-speed fiber backbone uplinks and
in campus links between buildings. The less expensive light-emitting diode (LED)
transmit sources are generally used. As FX uses a different light wavelength than
10BaseFL, it is not compatible or upgradable.
The 100BaseSX standard, on the other hand, uses the same short, 850 nm,
wavelength that 10BaseFL uses. This allows a transceiver to be designed that can
handle either speed and allows for a gradual migration from 10 to 100 Mbps (or
even 1000 Mbps). However, the SX distance is limited to about 500 m because of
the characteristics of multimode fiber at that wavelength.
Both 100BaseFX and 100BaseSX support the relatively short 100-m distances
of the horizontal cabling in TIA/EIA-568-C. The 100-m link is no problem to fiber,
with its inherently greater signaling distances. The moderate backbone connections
of 300 m are also easily accomplished by 100 Mbps Ethernet fiber.
Chapter 11 covers much more information on fiber-optic cabling.
Gigabit Ethernet 1000BaseSX and LX Wiring
The majority of Gigabit Ethernet cabling is done on either 1000BaseSX or 1000BaseLX
standards. As fiber was the first available technology for gigabit, it naturally has a sig-
nificant installed base. However, both these gigabit fiber standards are relatively limited
in distance capability (at fiber norms). They will both easily handle the 100-m horizon-
tal limit of TIA-EIA-568-C but, when used for backbone or centralized fiber, range in
distance from as little as 220 m to about 550 m. Of course, these are the minimum lim-
its for IEEE 802.3z, so most manufacturers exceed these distances by moderate amounts.
As with the other fiber standards, the ā€œSā€ stands for the short wavelength of
850 nm and is used with multimode fiber. The ā€œLā€ indicates the longer wavelength,
which is 1300 nm for multimode and 1310 nm for single mode fiber. As it turns out,
the distance ranges for each technology also mock the S (short distance) and L
(longer distance). Much more technical detail is shown in Chapter 12.
Several longer-range offerings are emerging for the extension of Gigabit
Ethernet into large campus and metropolitan area networks. Among these are pro-
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