Hello, everyone!
I would like to share with you an issue about ODU2_LOFLOM alarm on TN58NS4 line board housed in an OptiX OSN 8800 equipment.
Description:
The network scenario is as follows:
and the scheme of each FOADM node is as below:
Condition:
After create OCHs and client services (10GE LAN) through this route (... <-> 8800_C <-> 8800_A <-> 8800_B <-> ...), the interruption of client services is detected.
Sympton:
During commissioning, some ODU2_LOFLOM alarms appear on NS4 line boards of 3 consecutive FOADM nodes:
These alarms are located in 2 OCHs, as below:
Impact:
The client services carrying through these NS4 line boards are interrupted.
Possible causes:
The possible causes of the ODU2_LOFLOM alarm are as follows:
1) The signals transmitted by the corresponding board at the opposite end do not have a frame structure.
2) The input optical power is abnormal.
3) The FEC type is incorrectly configured.
4) Bit errors in the received signals of the OTU board at the local station are excessive.
5) The fiber of the transmission line is abnormal.
But following the procedure in steps (from 1 to 5) above, all the parameters are apparently correct.
Solution:
During a troubleshooting session with the Huawei TAC, it was found that the current internal logical fiber connection was wrong configured on 20-NS4 and 21-NS4 line boards of node 8800_A.
The internal fibers of both NS4 line boards are created backwards. That is, the 20-NS4 line board must be created to/from 8800_C and the 21-NS4 line board must be created to/from 8800_B.
Using the SM Overhead in the OTN Overhead Management, this problem was detected:
The physical and logical configuration mismatch.
Therefore, it needs to modify the internal logical fibers connections of the 20-NS4 and 21-NS4 in the 8800_A node.
For this, the steps are as follow:
1) Please delete from network layer the WDM Trails carrying through 20-NS4 and 21-NS4.
2) Delete the both internal logical fibers to/from 8800_A / 21-NS4 and then to/from 8800_A / 20-NS4.
a) 8800_A-Shelf2-15-12D40 --> 8800_A-Shelf0-21-58NS4 & 8800_A-Shelf2-1-12M40V --> 8800_A-Shelf0-21-58NS4
b) 8800_A-Shelf1-15-12D40 --> 8800_A-Shelf0-20-58NS4 & 8800_A-Shelf1-3-12M40V --> 8800_A-Shelf0-20-58NS4
3) Then create the internal logical fibers for your specific wavelength.
a) 8800_A-Shelf2-15-12D40 --> 8800_A-Shelf0-20-58NS4 & 8800_A-Shelf2-1-12M40V --> 8800_A-Shelf0-20-58NS4
b) 8800_A-Shelf1-15-12D40 --> 8800_A-Shelf0-21-58NS4 & 8800_A-Shelf1-3-12M40V --> 8800_A-Shelf0-21-58NS4
4) Search the WDM Trails.
The ODU2_LOFLOM alarms dissapears and the client services through both OCHs (A-C_OCh-22 and A-B_OCh-22) are active in normal state without any alarm.
Conclusion:
The OTN Overheads for troubleshooting is sometimes very helpful, as in this case.
Issue solved!!
BR
