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T3 FIBER OPTIC LINE DRIVER
5.2 Diagnostic Loopbacks
5.2.1 L
OCAL
L
OOPBACK
(LLB)
Local loopback tests the performance of the T3 electrical interface of the local line
driver and the equipment attached to it.
The data received at the T3 electrical interface is looped back to the line driver
attached to it (see Figure 5-2).
Figure 5-2. Local loopback illustrated.
To activate local loopback, s
lide the TEST switch to the LOC position. The LOC
indicator turns On and remains lit as long as the local loopback is active.
5.2.2 R
EMOTE
L
OOPBACK
(RLB)
Remote loopback tests the performance of the local line driver’s T3 electrical and
optical interfaces and the remote line driver’s optical interface.
The data received at the remote line driver’s optical interface is transmitted to the
electrical interface and is simultaneously looped back to the local line driver (see
Figure 5-3).
LOC POSITION
COAX
T3/E3
BERT
FOM
T3/E3
T3 Fiber
Optic Line
Driver
T3 Fiber
Optic Line
Driver
