EXFO FTB-7000 OTDR for FTB-200 v2 - Manual (Page 58)

Testing Fibers in Advanced Mode
44 FTB-7000 Series
Setting the IOR, RBS Coefficient, and Helix Factor
2. From the OTDR Setup window, go to the Acquisition tab.
3. Use the up or down arrow located on the side of the wavelength box to
select the desired wavelength.
4. Select the default settings by pressing Default. When the application
prompts you, answer Yes only if you want to apply the new settings to
all wavelengths.
OR
Enter your own values in the boxes, for each available wavelength.
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.
5. Press Exit OTDR Setup.
I
MPORTANT
Change the default RBS coefficient only if you have values provided
by the fiber manufacturer. If you set this parameter incorrectly, your
reflectance measurements will be inaccurate.
Wavelength for which
RBS and IOR will be
defined
Index of refraction
Rayleigh backscatter
coefficient