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232 Chapter 9

800,000
Figure 9-12
Capital costs for a 700,000
metropolitan-area
600,000
network 500,000
in $ USD 400,000

300,000

200,000
100,000
0
All optical SONET and
Fiber

TDM digital cross-connect and fiber-based architecture such as
SONET or SDH. Figure 9-12 shows the differences in pricing the
systems out in a metropolitan network where a carrier may be plan-
ning a new architecture. This figure shows that the older architec-
tures are rapidly becoming obsolete as all-optical networking
strategies and components become the method of choice.

DWDM Application Drivers

Beyond cost savings associated with using DWDM technology com-
pared with the cost of dedicated fiber, two other forms of savings
should be considered. These are related to the cost of future
upgrades and the opportunity costs of fiber.

Future Upgrades

In the mid-1990s in the telephone industry, many carriers believed
their fiber capacity was sufficient for many years of expansion. Inter-
net and data communications placed unanticipated demands on net-