Optical Network Design and Implementation

ONS 15454 Timing

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

• External— Building integrated timing supply (BITS) pins on the ONS 15454 backplane

• Line— An OC-N card installed in the ONS 15454 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 networks, one node is always set to external. The external node derives its timing from a BITS source wired to the BITS backplane pins. The BITS source, in turn, derives its timing from a primary reference source (PRS) such as a Stratum 1 clock or global-positioning system (GPS) signal. The other nodes are set to line. The line ...