TDM Processing Module

Stratum-2A clock: 

A Stratum 2 clock system tracks an input under normal operating conditions, and holds to the last best estimate of the input reference frequency during impaired operating conditions. A Stratum 2 clock system requires a minimum adjustment (tracking) range of 1.6 x 10-8. The drift of a Stratum 2 with no input reference is less than 1.6 x 10-8 in one year. The short-term drift of the system is less than 1 x 10-10 in 24 hours. If one interprets this specification as a drift of 1 x 10-10 each 24 hours, this amounts to a frame slip rate of approximately 1 slip in 7 days when the Stratum 2 clock system is in the hold mode. A Stratum 2 clock with

a drift of less than 2.5 x 10-11 per day will result in a time to the first frame slip of more than 2 months. Typical examples of Stratum 2 clocks are Rubidium Standards and Double Oven OCXO’s

Stratum-3 clock:

Stratum 3 is defined as a clock system which tracks an input as in Stratum 2, but over a wider range. A
Stratum 3 clock system requires a minimum adjustment (tracking) range of 4.6 x 10-6. The short term drift
of the system is less than 3.7 x 10-7 in 24 hours. This amounts to approximately 255 frame slips in 24 hours
while the system is holding. Some Stratum 3 clock equipment is not adequate to time SONET network
elements.