Fluke DTX Compact OTDR User Manual page 17

Setting
n
Index of refraction, which 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
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.
Range
The range setting determines the maximum distance shown on the trace. Select the range that is
nearest to, but not less than, the distance to the event you want to study. If the tester does not
(Manual OTDR
correctly identify the end event, run the OTDR test again using the next higher range.
mode only)
Manual: Lets you select the range.
Auto: The tester selects the range that is nearest to, but not less than the end of the fiber. These
ranges are not limited to the fixed ranges provided.
Table 2. OTDR Test Settings (cont.)
Description
OTDR Test Settings
-continued-
11