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ODU problem at one end causes MW_FEC_UNCOR alarm flashing at the other end

Publication Date:  2012-07-25 Views:  325 Downloads:  0

Issue Description

The case related to RTN950 V1R02C00, The alarm MW_FEC_UNCOR apeared at one end frequently every one minute, The link is 1+1 two ends only as per the picture attached  . 

Alarm Information

The alarm apeared at 3-IFU board at the near end of the link every 1 minute and cleared after apearance by 2 seconds. 

Handling Process

1. After we know the reason of the alarm we asked FM to go to the far end with the spare needed.
2. We asked them first to claim the tower and swap the IF cable between the two ODU and check the alarms at the far end.
3.We found there is no alarm at the near end, so we are sure the problem in the ODU.
4.We asked the FM to return the IF cable to the normal state and change ODU and all the alarms cleared.

Root Cause

1. The alarm apeared at the near end at the 2 IFU related to the 1+1 link.
2.We started by making inloop at 3-IFU and switch off the 5-IFU at the near end.
3. We checked the alarms at the near end there is no alarm.
4. We repeated the inloop at the 5-IFU at the near end and switched off 3-IFU and there is no alarm at the near end.
5.We made outloop at the far end at 3-IFU and switched off 5-IFU and the alarm still existing at the near end.
6.We repeated the outloop at the 5-IFU and switched off 3-IFU and there is no alarm at the near end.
7.We discovered that the problem will be at the far end at the 23-ODU and to be sure we forced of the protection at the far end and monitor the alarm for 24 hours.
8. After 24 hours we checked the history and we found that there is no alarm apeared.
9.We send the field maintenance to chage 23-ODU at the far end and the link became normal.


1. We have to check the ODU flashing alarms in daily basis.
2.For the 1+1 HSB links we need to make audit for the protection in monthly basis by the life test (switching action).