EXFO FTB-7000 OTDR Series for FTB-500 - Manual (Page 257)

Analyzing Bidirectional Traces
OTDR 243
Viewing and Modifying Current Trace Parameters
Viewing and Modifying Current Trace
Parameters
You can view the current trace parameters for the bidirectional trace as
well as for the A -> B and B -> A traces. However, you can only modify the
analysis settings for the current A->B and B->A traces, not for the
bidirectional trace.
Two groups of parameters can be changed:
³
the fiber settings: index of refraction (IOR), Rayleigh backscatter (RBS)
coefficient, and Helix factor
³
the analysis detection thresholds: for splice loss, reflectance, and
end-of-fiber detection
These modifications alter the displayed traces. These settings will also be
used when you reanalyze the trace.
By default, a tolerance interval parameter is used during bidirectional
analysis to match events from A->B and B->A traces in the resulting
bidirectional trace.
When you know the exact location of events in traces acquired in both
directions and are expecting a perfect match, you could get pairs of closely
spaced events in a combined trace. This is due to a difference in the
measured distance of events in each direction, which is greater than the
default tolerance interval.
You can increase the tolerance interval value in order to eliminate
mismatched events on the bidirectional trace.