Optical Network Design and Implementation

SDH Ring Architectures

This section examines SDH unidirectional and bidirectional ring architectures and examines the differences between two-fiber and four-fiber SDH rings. A comparison is also made between multiplex section (ring) switching versus path (span) switching. SDH provides for three attributes with two choices each, as illustrated in Table 6-13.

Table 6-13. SDH Ring Types

SDH Attribute	Value
Fibers per link	2-fiber 4-fiber
Signal direction	Unidirectional Bidirectional
Protection switching	Multiplex section switching Path switching

Table 6-13 shows various SDH ring configurations that differ in at least one major attribute. The commonly used ring types and topologies are as follows:

• Two-fiber subnetwork connection protection ring (two-fiber ...