Optical Network Design and Implementation

ONS 15454 Timing for SDH

SDH timing parameters must be set for each ONS 15454 SDH. Each ONS 15454 SDH independently accepts its timing reference from one of three sources:

• External— Building-integrated timing supply (BITS) pins on the ONS 15454 SDH backplane for SDH nodes or the Timing A and Timing B connectors on the MIC-C/T/P FMEC in slot 24 for SDH nodes.

• Line— An STM-N card installed in the ONS 15454 SDH that is connected to a node receiving timing from a BITS source.

• Internal— The internal ST3 clock on the TCC card.

In typical ONS 15454 SDH networks, one node is always set to external. In the case of SDH networks, the external node derives its timing from a MIC-C/T/P FMEC timing connector. The MIC-C/T/P FMEC, in turn, derives its timing ...