Symptom
In a network consisting of the OptiX BWS 1600G equipment, the ST2 board is used to provide the optical supervisory channel. The customer needs to receive external clock signals at the central station and then transmit the clock signals to remote stations by using the ST2 board. When receiving external clock signals, the ST2 board reports the ADDITION_C_BPV and ADDITION_C_CRC alarms and the external clock signals are unavailable.
Cause analysis
The possible causes of the preceding problem are as follows:
- Performance of the external clock signals is degraded and therefore the signals are unavailable.
- The ST2 board is faulty.
- The external clock signals are distorted.
Procedure
- Connect the clock signals to other equipment in the telecommunications room by using a fiber jumper. The clock tracing is normal. This indicates that the quality of the clock signals is normal.
- Replace the ST2 board on the equipment. The problem persists. This indicates that the board is normal.
- ***yze the ADDITION_C_BPV alarm. The encoding type of the clock signals received at the electrical port is HDB3. According to the HDB3 encoding rule, an ADDITION_C_BPV alarm is reported when four consecutive zeros are output. Such case occurs only when the output signals are distorted due to an external cause. Therefore, it is probable that the external clock signals are distorted.
- Measure the voltages on the clock equipment and the fiber jumper for connecting clock signals to the equipment on the ODF by using a multimeter. It is found that the difference between the voltages is about 0.6 V. Measure the 75-ohm unbalanced power cable in the same way. If the voltage difference is greater than 0.5 V, it is probable that the equipment does not share ground and therefore clock signals are distorted. In this case, you need check whether the grounding is reliable and shared by equipment.
- Check the grounding cables of the newly-deployed equipment. Disconnect the ground bar and re-connect it securely to rectify the fault.
