Chapter 15: Diagnose Problems in Fiber Links
Causes of OTDR Test Failures
501
Table 20. Causes of OTDR Test Failures (continued)
GPU32.EPS
The trace shows a small reflective event with
high loss. Can possibly show as an end event
though it occurs before the end of the link.
Can be caused by very sharp bend, a crack,
or a mechanical splice with high loss. If the
event is a bend, it usually has higher loss at a
longer wavelength. Use a visual fault locator
to verify the problem.
This example shows a sharp bend that occurs
before a connector.
GPU50.EPS
The trace shows an apparent increase in
optical power (a “gainer”).
A gainer does not cause a test failure unless
it exceeds a limit, but it can indicate a
problem such as a connection or splice
between mismatched fibers (different
backscatter coefficients, core sizes,
numerical apertures, or other parameters).
The top example shows a smaller core size
connected to a larger core size. If you do a
test from the other end, you would see a
large reflective event with more loss than a
connector should have.
The bottom example shows a splice between
smaller and larger core sizes.
(continued)
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