Fluke CableAnalyzer DSX-5000, Technical Reference Handbook, Page: 387 / 700

Chapter 11: The OptiFiber Pro OTDR Module
OTDR Results
351
Gainer
An apparent gain in the
strength of the returned
signal. A gainer shows as a
negative value of loss.
Page 501 shows OTDR
traces with gainers.
Caused by a splice or connection between two
fibers that have different backscatter
coefficients, numerical apertures, core
diameters, or mode field diameters.
The tester compares the loss of non-reflective
gainers to the limits for splice loss to give the
event a
PASS
/
FAIL
status.
If a gainer occurs at a connection, the gainer
shows as a
Reflection
event with negative loss.
The tester compares reflective gainers to the
limits for reflective events to give the event a
PASS
/
FAIL
status.
Strong reflections at or before an event can
cause tailing after the event, which can cause
a measurement of negative loss.
To find the cause of a gainer, see if the fiber
type is different before and after the splice or
connection. Replace fiber if necessary. Fibers
that are the same can possibly have different
tolerances, which can cause gainers at a splice.
When this occurs, the splice is usually good
and does not require rework.
-continued-
Gainer
(continued)
If you do the OTDR test from the other end,
the gainer event will show a loss. If you save
the result with the same ID as the result from
the other direction, the tester automatically
calculates bi-directional averages of loss
measurements and includes the averaged
values in the test record.
The averaged loss is
more accurate than the loss measured in one
direction. See “Averaged Bi-directional
Results” on page 388.
Gainers at launch events can occur when the
launch cord does not have the same properties
as the fiber under test. In this situation, you
can get more reliable results if you do a bi-
directional test. Use a tail cord that has the
same properties as the launch cord and use
Tail
compensation.
Table 14. Event Types in the Event Table (continued)