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• Link-signal-violation errors:
• Code violation error - occurs when a received character is recognized as invalid.
CRC errors
When a frame is received at a link-level facility, its contents (including the CRC field) are
read. The result of this operation must correspond to a specific value; if a mismatch
occurs, a CRC error is raised.
Determining the source of link level errors
If statistically significant amounts of the above errors are viewed on the Enterprise
Manager, the first level of troubleshooting involves the following:
1. Replace the SFP on the suspect link.
2. Replace the channel or device on the suspect link.
3. Replace the interface cable on the suspect link.
4. Run an internal diagnostic on the TFIO if a failure occurs.
Fiber link testing
Testing the fiber link checks the power level, and power loss, of a fiber optic link used to
connect the TFIO ports to other ports. These test procedures consist of measuring the
power level at the Tx output and the Rx input of the TFIO port.
Equipment required
The test equipment required for fiber optic link testing is:
• Optical Power Meter AT & T 938A Optical Loss Set or equivalent
• LC to ST Jumper Cable
• LC to ST Breakout Cable
• LC to ST adapter
Measuring the Transmitter (Tx) output power at the TFIO port
1. Disconnect the fiber optic cable from the TFIO port Tx connector to be tested.
2. Clean the tips of the fiber optic test cable prior to connecting the test cable to the
3. Connect fiber optic test cable to the TFIO port Tx connector and the power meter
– A connection error affects the ability of a link-level facility or a director port to
maintain the connection. In most cases, improper delimiters make the frame
unusable. For example, two consecutive frames transmitted with a SOF character.
– Loss of signal - The receiver does not get any signal, or the signal is below the
minimum level to be read.
– Loss of synchronization - The receiver is not able to distinguish the
synchronization characters.
TFIO port Tx connector and the power meter.
connector.
– For single mode TFIO ports (duplex LC connectors), use a single mode jumper
cable one meter in length.
Appendix A. Data collection and troubleshooting
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Troubleshooting
