EXFO OTDR 2 - Manual (Page 45)

Preparing Your OTDR for a Test
OTDR 37
Setting Macrobend Parameters
5. If necessary, set the delta value as follows:
5a. From the Wavelengths list, select the pair of wavelengths for
which you want to define the delta value.
Note: Only the combinations of wavelengths your module can support will be
available for a next acquisition. For a current acquisition, the available
wavelength in the file will be used.
5b. In the Delta (loss) box, enter the desired value.
5c. Repeat steps 5a and 5b for all wavelength combinations.