Optical Network Design and Implementation

SONET Layers

SONET has four optical interface layers, which are depicted in Figure 5-3 and are as follows:

• Path

• Line

• Section

• Photonic

Figure 5-3. SONET Layers

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Path Layer

The path layer deals with the transport of services between the path-terminating equipment (PET) NEs. The main function of the path layer is to map the signals into a format required by the line layer. Its functions include reading, interpreting, and modifying the POH for performance and APS.

Path-Terminating Equipment (PTE)

The STS PTE is an NE that multiplexes or demultiplexes the STS payload. As an example, STS-1 PTE assembles 28 1.544-Mbps DS1 signals and ...