EXFO FTB-8510B Guia Del Usuario página 1191

System Tab
Default Test Preferences
SONET/SDH LOP
Allows the selection of the default low order path background
traffic. Not suppoted on the FTB-8140. Choices are AIS,
Unequipped, and Equipped (PRBS 2^23-1 pattern). The default
setting is Equipped.
The diagram above shows a test case data path that is terminated
at the SONET/SDH low order path. The remaining STS-1 or AU-3
timeslot not involved in the test case are filled with background
traffic of STS-1 or AU-3 level depending on the interface being
SONET or SDH. At the low order path level, the data path not
involved in the data path defined in the test case are filled with a
background traffic equivalent to the VT Group (VTG) or Tributary
Unit Group (TUG) type defined by the traffic selected in the data
path. Further, the remaining VTG or TUG within the high order
path, selected in the test case, are respectively filled with traffic of
equivalent rate for SONET and SDH data paths.
541
SONET/SDH Application