0

SONET and T-carrier are both synchronous TDM.

But T-carrier does not use atomic clock. Why does SONET?

Is it because SONET does not use buffer? But how does it prevent bit loss if there is no buffering?

  • 1
    SONET/SDH end-stations, like routers or PSTN switches, can be clocked from the line/network. I believe you only need an accurate clock if you are a node able to add/drop/mux SONET channels among different circuits. – Jeff Wheeler Sep 12 at 14:40
3

SONET, or rather the synchronous digital hierarchy it's running on, requires very tight clock coupling across the whole structure. In order to stay within the sub-millisecond tolerances, there's no other way than with atomic clocks.

Sharing a central clock wouldn't work due to the inherent limitation of the speed of light, which covers just 300 km in one ms (or only 200 km over fiber) - minus processing overhead, the hierarchy would need to be very limited in geographic size.

T-carrier uses a much simpler master-slave clocking, so there's no requirements for atomic clocks.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.