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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The B3_EXC_VC4 alarm indicates that B3 bit errors in a VC-4 path cross the threshold.


Alarm Severity Alarm Type


Service quality alarm


When you view an alarm on the network management system, select the alarm. In the Alarm Details field display the related parameters of the alarm. The alarm parameters are in the following format: Alarm Parameters (hex): parameter1 parameter2...parameterN. For details about each parameter, refer to the following table.

Name Meaning

Parameter 1

Indicates the optical interface number. The value is always 0x01.

Parameter 2, Parameter 3

Indicates the VC-4 path number that generates the alarm.

Impact on the System

If the alarm occurs, it indicates that the number of bit errors (lower order B3 bit errors) crosses the performance threshold. The VC-4 services have severe bit errors.

Possible Causes

Possible causes of the B3_EXC_VC4 alarm are as follows:

  • There are B1 or B2 bit errors.
  • The received signals are heavily attenuated.
  • The fiber head is dirty or an incorrect connector is used.
  • The transmit unit at the opposite end is faulty.
  • The receive unit at the local end is faulty.


  1. Check whether B1 or B2 bit errors are present on the line board responsible for service access.

    If... Then...
    The B1_EXC, B1_SD, B2_EXC, or B2_SDalarm is reported Refer to the corresponding section in this document to clear the B1_EXC, B1_SD, B2_EXC, or B2_SD alarm.
    No B1_EXC, B1_SD, B2_EXC, or B2_SD is reported Go to the next step.

  2. Check whether the receive optical power is normal.

    If... Then...
    The optical power is lower than the lower threshold Check whether the fibers are functional, fiber connectors are clean, and transmit optical power of the opposite line board is normal.
    The optical power is normal Go to the next step.

  3. Check whether the working temperature is normal.

    If... Then...
    The working temperature is over high or over low In the case of over high working temperature, add a cooling device to the NE. In the case of the over low working temperature, add a heating device to the NE.
    The working temperature is normal Go to the next step.

  4. Check whether service configurations are correct. If the service configurations are incorrect, rectify the configurations. If the service configurations are correct, go to the next step
  5. Check for the B3_EXC_VC3 alarm on the U2000.

    If... Then...
    If the B3_EXC_VC3 alarm is cleared No further action is required.
    If theB3_EXC_VC3 alarm persists Go to the next step.

  6. Perform loopbacks at both the local and opposite ends to locate the faulty board.

    If... Then...
    The B3 bit error performance event is reported on the opposite board The transmit part of the opposite board is faulty. Replace the faulty board.
    The B3 bit error performance event is reported on the local board The receive part of the local board is faulty. Replace the faulty board.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

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