Page 175 - Optical Switching And Networking Handbook

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160 Chapter 7

14
Figure 7-2
International 12
growth of fiber 10
in billions $US 8

6
4
2

0
1998 2000 2002 2004

Let the Buying Begin

Faced with the many challenges of running a network, capacity plan-
ning, increased service needs, fiber depletion, and layered bandwidth
management, the carriers need options to provide an economical
capacity to withstand the onslaught of demand. One way to increase
the fiber capacity is to lay more fiber. Where the cost of laying new
fiber is minimal, this becomes the better solution. Unfortunately, lay-
ing new fiber will not necessarily enable service providers to provide
new services or use the bandwidth management capability of a uni-
fying optical layer.
A second choice is to increase the bit rate using TDM. Tradition-
ally, this has been the carriers’ choice (DS-1, DS-2, DS-3, and so on).
However, when the carriers use this approach exclusively, they must
make quantum leaps in one step, so they do not have to do this on a
regular basis. This leads them to buy more than they initially need.
Based on the SONET hierarchy, the next incremental step from OC-
192 is OC-768 (10 to 40 Gbps). This method has been used with var-
ious networks based on SONET or SDH. Regardless of the location
or technology, the carriers are making large investments in their
infrastructure.