The customer has 2 alarms on BTS3900 (GSM-R network).
1. BBU Optical Module Transmit/Receive Fault
2. RF Unit Maintenance Link Failure
The results of this alarms was restarting of the RF unit.
After combining the RRU log analysis and the alarm of the optical module, the radio frequency maintenance link is triggered by the power-off of the RRU board, as shown in the following screenshot.
The cause of the RRU startup alarm record is 00 00, which represents the board is powered off.
Also the alarm log separately records the root cause of the reset boards as below:
You can check the RRU's power cable and if the voltage is stable.