severely errored seconds (ATM) (SES)

Severely Errored Seconds(SES) is a unit for evaluating the error performance ofT-lines.

Severely Errored Seconds refers to a one- second interval in which the error rate is greater than the specified rate and thus affects transmission performance.

The SES unit can refer to errors per unit time in seconds, hours, days or weeks. This method allows a better evaluation of the error distribution than the simple bit error rate( BER).