Precision time-transfer in transport networks using digital crossconnect systems

The authors describe a technique for precise synchronization of the time-of-delay clocks in networks of digital cross-connect systems (DCS), intended to enhance the performance of reconfigurable transport networks. The method is specifically devised to exploit the fine time resolution of the carrier signals to which a DCS has direct access. The resulting scheme is a master-slave, multisite, implicitly-delay-compensated, nonhierarchical time-transfer method with a theoretical precision of one bit time at the carrier rate. A worst-case estimate of delay asymmetry (including jitter effects) suggests that time-transfer error of under one microsecond should be obtainable. The method is most easily supported by an n/n space-switching DCS which has equal delay on all paths through its core and has a bridging connection feature. A circuit module for DCS hardware support of the time-transfer function is outlined