Fluke OF-500-01 OptiFiber, Technical Reference Handbook, Page: 86 / 278

OF-500 OptiFiber Certifying OTDR
Technical Reference Handbook
3-10
Table 3-1. Settings for OTDR Tests (cont.)
Cable tab MANUAL CABLE
SETTINGS
n
BACKSCATTER
When MANUAL CABLE SETTINGS is disabled, the n and BACKSCATTER values
depend on the selected fiber type. When the MANUAL CABLE SETTINGS is
enabled, the tester enters default values that you can change manually.
The n value is the index of refraction. Index of refraction is used to calculate
length. The default n values defined in the fiber types are suitable for most
applications. Minor differences between the default n and a fiber's actual n
usually do not make enough difference in length to fail a fiber.
Increasing n decreases measured length.*
BACKSCATTER is the backscatter coefficient, which indicates the amount of
light the fiber reflects back to the OTDR (using a 1 ns pulse). This value is used
to calculate event reflectance for OTDR tests.
Enter the backscatter coefficient of the fiber under test, if known. This value is
specified by many fiber manufacturers.
* For singlemode modules, the 30 km range and an n value greater than 1.52 cause an error. These settings produce propagation times that
are beyond the tester’s range.
SETUP Tab Setting Description