Secondary Synchronization Units US4G based on Rubidium technology ( SSU or SASE)
The SSU will receive the pilot frequency through the transmission network and will distribute it to the different network elements that need to be synchronized or to tertiary synchronization units. They will also filter out part of jitter and wander due to transmission impairments.
An important characteristic of these units is the internal frequency difference compared to the nominal value according to time. In order to prevent synchronization disruption accumulating in the synchronization network when the synchronization link is lost, the unit should continue to provide a synchronization signal for a determined period of time (HOLDOVER operating mode). That is why they have oscillators with very high stability. Oscillators used are generally Rubidium oscillators, of which ageing is about 1.10 -11 /month. This unit can also be equipped with a GPS clock, which will ensure backup for the link from the primary clock.
These units have an average cost and their number depends on the transmission network architecture.
Tertiary Synchronization Units US4G based on Quartz (SSU or SASE)
They will receive the pilot frequency throughout the network and will distribute it to the different elements that need to be synchronized. They will also eliminate jitter and wander due to transmission.
Internal oscillators used are generally Quartz oscillators, of which ageing is about 1.10 -9 / day.
These units are cheap and require almost no maintenance.
|
