EXFO OTDR 2 - Manual (Page 128)

Analyzing Traces and Events
120 OTDR
Viewing and Modifying Current Measurement Settings
When viewing or modifying trace settings, these parameters are displayed:

Wavelength: Test wavelength.

IOR: Refraction index of the displayed trace, also known as group
index. If you modify this parameter, the distance measurements for the
trace will be adjusted. You can enter an IOR value directly, or let the
application calculate it with the distance between span start and span
end you provide. The IOR value is displayed with six digits after the
decimal point.

Backscatter: Rayleigh backscatter coefficient setting of the displayed
trace. If you modify this parameter, the reflectance and ORL
measurements for the trace will be adjusted.

Helix factor: Helix for the displayed trace. If you modify this parameter,
the trace distance measurements will be adjusted.
Note: You cannot define a different helix factor for each wavelength. This value
takes into account the difference between the length of the cable and the
length of the fiber inside the cable; it does not vary with wavelengths.

Detection thresholds:

Splice loss: Current setting for detecting small non-reflective events
during trace analysis.

Reflectance: Current setting for detecting small reflective events
during trace analysis.

End-of-fiber: Current setting for detecting important event loss that
could compromise signal transmission during trace analysis.
For more information, see Setting the Analysis Detection Thresholds on
page 30.