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CHAPTER 5: Troubleshooting and Diagnostics
Figure 5-1. Local Fiber Optic Modem in Analog Loopback (LLB).
If the test detects a fault, repeat the LLB test using external BERT equipment. If
the BERT test indicates an error-free data stream, but the test using DTE indicates
a fault, verify that the cable between the DTE and the Fiber Optic Modem is not
faulty or improperly connected. If the problem persists, follow the DTE
manufacturer’s test procedures to isolate the fault.
To identify a problem in the communication line, perform the LLB loopback at
the remote end of the line. If both LLB tests are error-free, the fault is in the
communication link or in the line interfaces.
After completing the test or correcting the fault, return the ANA pushbutton to
the OFF (up) position.
5.2.2 R
EMOTE
D
IGITAL
L
OOPBACK
(RLB) S
TANDARD
V.54
The Remote Digital Loopback (RLB) test determines the performance of the local
and the remote Fiber Optic Modems as well as their interconnecting lines. The
Remote Digital Loopback sets a loop at the remote Fiber Optic Modem from the
terminal coupled to the local unit (see
Figure 5-2
).
Fiber Optic
Modem
