Page 185 - Optical Switching And Networking Handbook

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170 Chapter 7

now deployed throughout the carrier infrastructure, and with a
128-channel system coming, DWDM certainly will be a key ingredi-
ent for interoffice interconnectivity. Indeed, deployment of DWDM is
a critical first step toward the establishment of photonic networks in
the access, interoffice, and interexchange segments of today’s
telecommunications infrastructure.
Given the rapidly changing and unpredictable nature of the
telecommunications industry, it is imperative that today’s DWDM
systems adapt to future deployments and network configurations.
Open DWDM systems provide such flexibility to aid the carriers in
planning their future photonic network.
DWDM systems with open interfaces incorporate SONET/SDH,
ATM, Frame Relay, asynchronous/PDH, and other protocols over the
same fiber. Open systems also eliminate additional high-performance
optical transmitters to interface with specific protocols. Rather, open
systems enable service providers to quickly adapt new technologies
to the optical network with “off the shelf,” relatively inexpensive, and
readily available transmitters.
Conversely, proprietary DWDM equipment locks the carrier into a
single vendor, whereas open systems provide more freedom to provide
services and reduce long-term costs. Proprietary systems, in which
SONET/SDH equipment is integrated into the optical multiplexer-
demultiplexer unit, are adequate for straight point-to-point configu-
rations. Nevertheless, they require additional and costly
transmission equipment when deployed in meshed networks.
DWDM systems complying with the ITU standards assure the
carriers that they have systems with recognized industry standards
and the flexibility to grow their optical networks into long-distance,
local exchange, and access networks. Given the amount of growth
and flexibility available, Table 7-6 shows where the vendors will sell
their equipment and the marketplace for the near future. These fig-
ures represent specific categories of users, along with U.S.-based
providers only. Considering other market segments will increase the
numbers dramatically. This is still a place where we will expect to
see much activity.