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Chapter 12: The OptiFiber Pro HDR OTDR Module
HDR OTDR Results
435
Hidden
The event is in the
attenuation dead zone of
the previous event.
The tester detected the event, but does not
have enough information to measure its loss
separately from the previous event. Thus, the
tester includes the loss of the hidden event
with the loss of the previous event. The loss of
the hidden event shows as
N/A
.
A hidden event is often the end of a patch
cord that is hidden in the dead zone made by
the first connector on the cord.
To get a better view of hidden events, do a
Manual OTDR
test with the
Averaging Time
set to
Best Resolution
. Narrow pulse widths
can also help you see hidden events.
If the event is not a connection, inspect the
fiber near the location of the event. Use a
visual fault locator to see faults such as cracks
or breaks in the fiber. Ghosts anywhere on the
fiber and splices near the end of the fiber can
also cause hidden events.
The tester does not give a
PASS
/
FAIL
status to this
event, unless the test limit has a limit for
reflectance and the hidden event exceeds the limit.
Ghost
(Also known as an “echo”.)
The event is a copy of
another reflection. It is
caused by light bouncing
back and forth between
connectors. Page 502
shows OTDR traces with
gainers.
Caused by a dirty or unseated connector,
highly-reflective connector, a connector with
an incorrect polish, a sharp bend, or a crack in
a fiber.
To see where to look for the fault, find the
Ghost Source
in the event table. The ghost
source is always before the ghost. The event
table does not show ghosts that occur after
the end event.
If the ghost source is a hidden event, the tester
possibly will not identify a ghost event as a
ghost.
The tester does not give a
PASS
/
FAIL
status to
this event.
-continued-
Table 17. Event Types in the Event Table (continued)