EXFO OTDR 2 - Manual (Page 100)

Analyzing the Results Manually
92 OTDR
Getting Optical Return Loss (ORL)
Getting Optical Return Loss (ORL)
The ORL calculation will provide the following information:

the ORL between markers A and B

the total ORL is calculated either between the span start and the span
end, or on the total fiber span, depending on the option you have
selected. For more information, see Excluding and Including Span Start
and Span End on page 28.
Optical return loss (ORL) refers to the total effect of multiple reflections
and scattering events within a fiber-optic system.
To get the ORL value:
1. From the main window, select the Measure tab.
2. At the bottom of the window, tap ORL. Markers A and B appear on the
graph.
3. Position markers A and B to delimit the area for which you want to
know the ORL value.