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114 Chapter 5

Benefits of Fiber over Other Media

The benefits of fiber over other media are shown in Table 5-2. How-
ever, it is important to note that fiber has been used extensively in
the long-distance telecommunications networks and the local tele-
phone company networks. It is more recent that a single-mode fiber
has worked its way into end-user networks (LANs and Campus Area
Networks [CANs]). With single-mode fiber, the speeds are constantly
being upped, while the error performances are continually being
improved. This table concentrates on the bit error rates (BERs) and
the speed of the cabling systems.

Wave-Division Multiplexing

Now back to the wave division-multiplexing concept.There is no mis-
take; demands and needs for telecommunications services are grow-
ing. The combination of voice, data, and multimedia applications
that are constantly putting pressure on the infrastructure adds to
the growing problem, where normal digital transmission systems
use TDM and cable TV (CATV) analog technologies use FDM. WDM
is a combination of the two schemes. Use of a TDM multiplexer
breaks the bandwidth down to specific timeslots such as those found
in SONET-based networks. However, by using the combination of
frequency (different wavelengths) and time (timeslots), the fiber can
be used to carry orders of magnitude more than traditional fiber-
based systems. Figure 5-6 shows the combination of the two multi-
plexing arrangements in a single format. Furthermore, several
different wavelengths and colors of light can be used to produce far
more capacity.
No one can mistake the fact that telecommunications capacity
needs are growing rapidly. Dense WDM (DWDM) was developed to
produce even better results on a single fiber pair than the original
techniques deployed on the backbone networks. Expanding capacity