EXFO OTDR 2 - Manual (Page 127)

Analyzing Traces and Events
OTDR 119
Viewing and Modifying Current Measurement Settings
Viewing and Modifying Current Measurement
Settings
You can view the trace settings and modify them at your convenience.
Two groups of settings can be changed:

Fiber settings: index of refraction (IOR), also known as group index,
Rayleigh backscatter (RBS) coefficient, and helix factor.

Detection thresholds: for splice loss, reflectance, and end-of-fiber
detection.
Modifications you make are only applied to the current trace (that is, to a
particular wavelength), not to all traces.
The application will only prompt you to reanalyze the trace if you modify
the RBS coefficient (no analysis necessary when you modify the IOR or
helix factor). If you want to modify the settings that will be used for future
acquisitions, see Setting the IOR, RBS Coefficient, and Helix Factor on
page 24 and Setting the Analysis Detection Thresholds on page 30.