EXFO FTB-5600 Distributed PMD Analyzer - Manual (Page 70)

Managing Results
64 FTB-5600
Section Event Table
The PMD section value provides the PMD of a particular section over the
link. The section's PMD value is the square root difference of the PMD
cumulative curve section's last value and the PMD cumulative curve
section's first value. The formula is:
The contribution value provides a way to evaluate the contribution of a
specific section of the cumulative PMD of a link. Since PMD adds up to the
square, the contribution is computed in squares. The percentage of
contribution values are provided in square since it is mathematically not
possible to provide a square rooted percentage. Values would simply not
add up to 100 % and be harder to interpret.
Below, you can see an example of a fiber with two sections. The first
section has a value of 5 ps and the second section, of 10 ps. This will result
in a 11.2 ps of total cumulative PMD.
PMDSection CumulPMDSectionLastValue
2
CumulPMDSectionFirstValue
2
– =