IMC Networks iMcV-LIM User Manual
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9
FEF versus FA
FEF is preferred when the devices at both ends of the fiber can interpret the FEF
signal. This allows FEF to be turned on at both ends, which will engage the FEF
regardless of which direction the fault occurs. (Please refer to diagram on previous
page) For example if a fault should occur on segment 2 in the direction of segment 1
to 3, FEF would be engaged on the iMcV-LIM between segment 2 and 3. This would
then send a signal back to the iMcV-LIM between segment 1 and 2. If the iMcV-LIM
between segment 1 and 2 is in a managed chassis, the chassis would send a trap that
the port is down. Alternatively, if the iMcV-LIM is not in a managed chassis, FXLL
could be engaged to propagate the fault onto the copper port; this would cause
segment 1 to show no link on both ends.
FA is used when connecting to a device that does not support FEF. If an FEF signal is
sent to a device that does not support FEF, the device acts as if there is still a good
connection. The FEF signal is mistaken for data. FA works similar to FEF, in that
when there is a fault in one direction of the fiber, it acts on the fiber in the opposite
direction. But unlike FEF, FA sends no signal. Because of this, FA can not be
enabled on both ends. If it is enabled and a fault occurs, FA will turn signal off in the
opposite direction; the device on the other side of the fiber will see the loss of signal
and engage FA, turning off signal. The net result will be the signal turned off in both
directions, even after the fault has been repaired.
It is highly recommended that only one is chosen, either FEF or FA. If both are
selected FA will take precedence over FEF.
For more information on LinkLoss/FiberAlert, visit the IMC Networks Web site at
http://www.imcnetworks.com/support/
If unsure of how to implement these features
in a specific configuration, contact IMC Networks Technical Support at
(800) 624-1070 (U.S./Canada), +32-16-550880 (Europe) or via e-mail at:
.