Symptom
On a chain network built with the OptiX OSN 6800, a wavelength is deployed from station A to station B and another wavelength is deployed from station A to station C. One day, two NS2 boards at stations B and C in the downstream direction of station A report IN_PWR_HIGH alarms for three times and also report OCH_SSF and ODU0_PM_DEG alarms. These alarms are cleared half an hour later.
Cause analysis
Possible causes of the problem are as follows:
- The line is malfunctioning.
- A board is malfunctioning.
Procedure
- At station A, check performance of the OBU board that receives signals from station B. Optical power fluctuation occurs when the fault occurs. The receive optical power of the OBU board is suddenly increased from -20.8 dBm to -2.2 dBm. The receive optical power of the two NS2 boards at stations B and C is suddenly increased from -8 dBm to +1 dBm, which is higher than the overload of the NS2 boards.
- At station B, check the transmit optical power of the OBU board that transmits signals to station A. The optical power is always at +4.4 dBm.
- The transmit optical power is stable but the receive optical power is suddenly increased. Therefore, the possibility of a line fault is very low and the VA1 board may be faulty.
- During a test on transmit and receive optical power, the attenuation of the VA1 board is set to 7.5 dBm on the NMS, but the measured total attenuation is about 22 dBm. When the fault occurs, the attenuation of the VA1 board is about 2 dBm. Therefore, it is determined that the attenuation adjustment function of the VA1 board is malfunctioning. The problem is resolved after the VA1 board is replaced and the optical power is adjusted.
