Page 306 - Optical Communications Essentials

Optical Networks

296 Chapter Seventeen

Primary 2-fiber loop
Node
1
2-Fiber
protection
loop
Node Node
5 2
Protection-switching loopbacks

Node 4 Cable Node Node 3
failure failure
Figure 17.12. Reconfiguration of a four-fiber BLSR under node
or fiber cable failure.

OC-48 OC-192
Linear chain
OC-12 OC-12 OC-48 BLSR OC-192 BLSR

OC-48 OC-192
OC-3 Interconnected
rings
OC-3 UPSR OC-3

OC-3
Figure 17.13. Generic configuration of a large SONET network consist-
ing of linear chains and various types of interconnected rings.

interconnecting span internally switch the primary-path connections from their
receivers and transmitters to the protection fibers, in order to loop traffic back
to the previous node. This process again forms a closed ring, but now with all
the primary and protection fibers in use around the entire ring, as shown in
Fig. 17.12.

17.2.4. SONET/SDH networks
Commercially available SONET/SDH equipment allows the configuration of a
variety of network architectures, as shown in Fig. 17.13. For example, one can
build point-to-point links, linear chains, UPSRs, BLSRs, and interconnected
rings. The OC-192 four-fiber BLSR could be a large national backbone network
with a number of OC-48 rings attached in different cities. The OC-48 rings can

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