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Wave-Division and Dense-Wave-Division Multiplexing 117

Table 5-3 Industry Demand Cause

Summary of
Need for bandwidth Internet access, cellular and personal communica
Demand to tions (PCS) and data/voice integration.
Justify the Use
Need for reliable In order to guarantee the reliability customers
of DWDM
communications are demanding, the carriers have been committing
alternate routes and spare fiber capacity to back up
existing infrastructure.
More capacity In order to get the service-level agreements (SLA) and
maintain the network in a fashion expected by the
consumer, the carriers have to install backup circuits
and fibers in their highest-density routes.

Higher performance Network dependency has become the norm. All forms
on the network of traffic must run on the existing infrastructure, and
the carriers must provision capacity to meet the ever-
changing demands of the network.

The major manufacturers obviously have put all their resources
into the development of DWDM techniques to meet the rising
demand from carriers and end users alike.The use of multiple wave-
lengths enables the carriers to achieve 320-Gbps capabilities today,
with terabit speeds being discussed at the beginning of the new mil-
lennium. Using a few different techniques, the major suppliers have
developed keen interest in the ability to use DWDM. Multiwave-
length optical repeaters (MOR) help in deploying this technology out
to the carrier networks. An MOR (or MOR plus) is an amplifier used
to support at least 16 wavelengths on the same fiber in each direc-
tion. Using 16 wavelengths (16 ) operating at the OC-192 rate yields
160 Gbps in each direction or 320 Gbps in one direction. Figure 5-7
shows a typical multiplexer used to generate a bidirectional flow of
information through the fiber multiplexer. This figure shows the
major components of the systems used by Nortel, but the compo-
nents are the same as those used by others (for example, Lucent
Technologies, Siemens, or Alcatel). In either case, the major point
here is that use of a DWDM coupler aggregates the capacity of the
fiber using two different light bands (red and blue) and multiple
wavelengths to achieve the results we have grown to expect.