When a problem occurs in the SONET/SDH network feeding a WDM network, the equipment in the WDM network generates alarms (for instance, LOS on the input transponder). When the Optical Transport Manager does not diagnose a root-cause in the WDM network, but does diagnose a problem in the SONET/SDH network, it indicates that the WDM alarms are impacts of the SONET/SDH problem.
