Page 133 - Optical Switching And Networking Handbook

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118 Chapter 5

Figure 5-7
Red
Bidirectional 1R 1 R
transmissions on
a single piece
of fiber
1B
Blue 1 B
Single Fiber

Red
16 R 16 R

16 B 16 B
Blue

Increasing the capacity of the fiber through the use of DWDM
appeals to many of the providers and carriers alike. Fiber-based
multiplexing also adds some other enhancements that were not
available in the past. Because the signal never terminates in the
optical layer, the interfaces can be independent of bit rate and for-
mat. This enables the service providers the opportunity to integrate
DWDM easily with their existing equipment and infrastructure
while still gaining access to the untapped resources and capacities in
their existing fiber.
DWDM combines multiple optical signals so that they can be
amplified as a group and transported over a single fiber, increasing
the capacity. Each signal carried on the DWDM architecture can
operate at a different rate (for example, OC-3, OC-12, OC-48, and so
on) and in a different format (for example, SONET, ATM cells, data).
Using a mix-and-match approach enables the carriers to achieve dif-
ferent rates of speed and aggregated throughput, depending on the
multiplexing equipment used. Future DWDM developments are
touted as being able to carry up to 40 wavelengths of OC-192, or 400
Gbps. As a comparison, 400 Gbps will be 90,000 volumes of an ency-
clopedia in one second.