EXFO FTB-7000 OTDR for FTB-200 v2 - Manual (Page 234)

Analyzing Traces with the Bidirectional Analysis Application
220 FTB-7000 Series
Modifying the Alignment of Unidirectional Traces
4. Press Set as Span Start or Set as Span End to set the span start or
span end marker on the appropriate event in the trace display.
Changes to the span start and span end will modify the contents of the
events table. For the A->B trace, the span start becomes event 1 and its
distance reference becomes 0. For the A->B trace, the span end becomes
the last event and its distance reference becomes 0.
Only events between the span start and span end will be numbered in the
trace display and events table.The cumulative loss is calculated within the
defined fiber span only.
I
MPORTANT
To keep a set fiber span during trace reanalysis, activate the
corresponding option (see Saving the Span-Start and Span-End
Information on page 246). Otherwise, the span start and span end
markers are reset to zero in the process.