EXFO FTB-800 Series for FTB-1 - Manual (Page 226)

Test Setup - Test Configurator, Timer, and System
216 FTB-700G/800 Series
Signal - Signal Configuration (SONET/SDH)
STS/AU Path (SONET/SDH HOP):
The following diagram shows a test case data path that is terminated
right after SONET/SDH high order path. High order background traffic is
automatically adapted to the rate (STS-1, AU-3, or AU-4) signal level for
the paths that are not defined in the test case.