EXFO FTB-7000 OTDR Series for FTB-500 - Manual (Page 251)

Analyzing Bidirectional Traces
OTDR 237
Analyzing the Fiber on a Specific Fiber Span
Analyzing the Fiber on a Specific Fiber Span
If you want to focus your fiber analysis on a specific fiber span, you can
define events (new or existing) as span start and span end.
Span start and span end are defined on both the A->B and B->A trace.
Traces are aligned on the span start of the A->B trace and on the span end
of the B->A trace. The two other span events are not used in the
bidirectional analysis.
Changes to the span start and span end modify the events table. The span
start becomes Event 1 and its distance reference becomes 0. All events on
both traces are numbered on the trace display. The cumulative loss is
calculated within the defined fiber span only.
Note: To keep a set fiber span during trace reanalysis, activate the fiber span
delimitation memory (for details, see Saving the Span-Start and Span-End
Information on page 85); otherwise, the span start and span end markers
are reset to zero in the process.
You can use the zoom control buttons to modify the trace display. For more
information, see Using Zoom Controls on page 137.