Chapter 8: Troubleshooting
Cable Diagnostics
Page 8-2
Cable Diagnostics
This section describes how to diagnose cable faults.
The Cable Diagnostics feature may be used to test Ethernet cables connected to the Main PSU
port and the Aux port. The feature uses Time Domain Reflectometry (TDR) technology to test
individual twisted pairs in the cable, to identify open circuit and short circuit faults, and indicate
the approximate location of the fault:
•
Open circuit – An open circuit is detected when the impedance is greater than 300 ohms.
•
Short circuit – A short circuit is detected when the impedance is less than 33 ohms.
•
Approximate location of the fault - The fault location is reported as a distance from the
ODU along the cable, and is accurate to +/- 2 meters (6.5 feet).
Note
•
The cable diagnostics results are provided only as a guide.
•
The feature reliably detects all open circuit and short circuit faults in cable pairs,
but it is not possible to reliably detect short circuit faults between wires in different
cable pairs. Except for that specific circumstance, an OK result for all pairs means
the cable is good.
•
The presence of LPUs can affect the accuracy and reliability of the results.
Before initiating the test, confirm that all outdoor drop cables (that is those that connect the
ODU to equipment inside the building) are specified as supported, as defined in
Test scenarios
The Cable Diagnostics test may be performed in following scenarios:
Scenarios
Actions
Main PSU port “Down”
Check for physical Ethernet cable connectivity between Power over
Ethernet (PoE) and Customer Data Network (or LAN).
If the cable connectivity is OK, Perform
Aux port “Down”
Check for physical Ethernet cable connectivity between ODU and
Customer Data Network or Management Agent.
If the cable connectivity is OK, Perform
Main PSU or Aux port is
“Up” but the Ethernet
speed is noticed slow
There is a possibility that one or more cable pairs have intermittent
contact with the RJ45 connector pin. This could result in intermittent
communication errors.
Follow procedure
If Ethernet Rx Crc and Align counter is greater than ten (>10),
Perform