EXFO FTB-800 Series for FTB-1 - Manual (Page 576)

Glossary
566 FTB-700G/800 Series
SONET/SDH
SONET Numbering Convention
The FTB-700G/800 Series supports the Timeslot (default) and hierarchical
two-level numbering conventions as per GR-253.
Hierarchical Notation:
The FTB-700G/800 Series supports numbering SONET high order path
STS-1s and STS-3c using the two-level “STS-3#,STS-1#”convention in an
OC-N. For example: STS-1 [2,3].
The FTB-700G/800 Series supports numbering SONET low order path using
the two-level “VTGroup#,VT#” convention for numbering VTs within an
STS-1. For example: VT1.5 [1,3], VT2 [3,2], VT6 [6,1].