End to End BER

[todewey]

I have an application which will only tolerate a BER less than 10 -9. When I have a circuit which consists of multiple(say 3) SONET paths(in series) with BER specs of 10 -12. Do I add these together to get the End-to-End BER???

[lcsaszar]

Yes. The BER actually expresses the probability of occuring a given number of bit errors during a specified time. Since the occurance of bit errors on the Sonet sections are independent events, their probabilities simply add together to get the combined BER.

[m.prouty]

Are these three paths or segements logically cross connected together thru an ADM? If so you can consider you E2E test from the two end systems that are linked together for the optical/electical path. If they are broken down into subrates for the connection of the end system running the application you can consider you E2E to be what ever they terminate the path and are no longer a carrier or subrate of that carrier. For example of you are testing a DS3 across a OC48 link the DS3 to DS3 is your end to end. Once it is no long DS3 or a subrate of that DS3 (if that is what you are testing) you can consider it outside of your End to End. The subrate is that that is connected to your system, e.g. 2mb on a time slot within the STM1. The originatng 2mb port to theh terminating 2mb port are you end to end regardless of how many times the circuit is multiplexed and demultiplexed. So your BER for this circuit should consider all of these connections as the application using this link will realize all of the errors on this link.

Matt