
Chapter 3. Operation
Loopback Descriptions
* LLB (Optical local loop back)
near
end
(NE) far
end
(FE)
* RLB (Optical Remote loop back)
near
end
(NE) far
end
(FE)
* RRLB (Request optical remote loop back)
near
end
(NE) far
end
(FE)
FEF (Far End Fault)
The FEF function lets the receiving unit advise the far end unit that it has lost the receive
optical signal.
1. Fiber Broken
2-2.FEF sent
3. FEF received
2-1. AIS sent
4. AIS sent
In a FEF enabled unit above, loss of received optical signal will result in an FEF signal being
sent to the far end unit, and AIS (Alarm Indication Signal) sent in both E1/T1 directions.
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