36
SYNC/ASYNC FIBER OPTIC MODEM
Figure 5-2. Fiber Optic Modem in Remote Digital Loopback (RLB).
Press the REM pushbutton on the front panel to activate the RLB loopback.
This test causes the TEST LED to light on the front panel of both local and remote
modems. You can also activate this test via the appropriate pin on the digital
interface.
If the RLB test indicates a fault, but the LLB test (see
Section 5.2.1
) was
successful in both local and remote modems, then the line or line circuits on one
side of the line are not functioning properly.
5.2.3 L
OCAL
D
IGITAL
L
OOPBACK
(DIG) N
ON
-S
TANDARD
This test loops the received data back to the remote Fiber Optic Modem, as shown
in
Figure 5-3
. The operator at the remote end uses this test to determine the
performance of the local and remote Fiber Optic Modems and the communication
link.
NOTE
Confirm first that the timing (clock) strap is set to RCV.
Press the DIG pushbutton on the front panel to start the test.
The Local Digital Loopback test is equivalent to activating the remote loopback
from a remote Fiber Optic Modem.
Local Fiber
Optic Modem
Remote Fiber
Optic Modem
