EXFO FTB-7000 OTDR for FTB-200 v2 - Manual (Page 72)

Testing Fibers in Advanced Mode
58 FTB-7000 Series
Setting a Default Span Start and Span End
Setting a Default Span Start and Span End
By default, the span start and span end of a fiber are assigned, respectively,
to the first event (the launch level event) and the last event (often a
non-reflective or reflective end event) of a trace.
You can change the default fiber span that will be applied during the initial
trace analysis.
You can set the span start and span end on a particular event or at a certain
distance value from the beginning or end of the trace. You can even define
a fiber span for short fibers by placing the span start and the span end on
the same event.
³
By default, the number of available events is set to 10 and, therefore,
does not necessarily reflect the actual number of events displayed.
³
When you set a distance value for the span start or end, the application
searches for a nearby event. If it finds one, the span start or end is
assigned to that event, rather than at the exact distance you have set.
Changes to the span start and span end will modify the contents of the
events table. The span start becomes event 1 and its distance reference
becomes 0. Events excluded from the fiber span are grayed out in the
events table, and do not appear in the trace display. The cumulative loss is
calculated within the defined fiber span only.
Note: You can also change the fiber span of a single trace after the analysis and
reanalyze the trace (see Analyzing or Reanalyzing a Trace on page 151).
However, if you want to keep working with the original parameters, you
must reenter them.