Chapter 8: Troubleshooting
Cable Diagnostics
Page 8-3
Scenarios
Actions
If Packet Error Rate is greater than 1 in 1 million, Perform
If Number of lost packets are less than two (<2) after performing
, perform
Otherwise check the ODU’s parameter configurations.
Cable Diagnostics test
Menu option: System > Cable Diagnostics
The Cable Diagnostics feature determines a fault in a cable and its approximate location based
on Time Domain Reflectometry (TDR).
When the test is initiated for the selected port(s), the ODU sends a known signal (+1V) over the
twisted pair cable. The transmitted signal will travel down the cable until it reflects off a fault.
The magnitude of the reflection and the time it takes for the reflection to come back can be
used to calculate the distance to the fault on the cable. For example, a +1V reflection will
indicate an open close to the PHY and a -1V reflection will indicate a short close to the PHY.
Based on the returned signal, the radio identifies the cable status and estimates the distance of
the fault. The result of the cable test will be displayed.
The cable diagnostics test can be carried out for Main PSU and AUX ports. This test is not
supported for SFP port.
Caution
•
On the Main PSU port, the presence of LPUs can affect the accuracy of the cable
diagnostics results for some cable configurations. When a fault is detected, the
feature reports the distance corresponding to the final TDR signal reflection. In
configurations where there is a short cable from the ODU to the first LPU (< 2m),
and a moderately long cable to the second LPU (30m), the final TDR signal
reflection may come from one of the LPUs itself, rather than the fault. For
example, a fault in the first short cable may be reported at or near the second LPU.
•
On the Aux port, the presence of LPUs can affect the reliability of the cable
diagnostics results for many cable configurations. Frequently, open circuit faults
may be reported when the cable is OK, and fault distances may be reported
corresponding to the LPU locations. Cable diagnostics tests on the Aux port
should be repeated a number of times to establish a pattern.
Note
All cable diagnostics results should be verified with an external cable tester before
remedial action is taken.
All four twisted pairs of the cable are tested separately and results are displayed for each pair.
The pin to pair mapping of a cable is shown in
