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OTU3_LOF alarm appears due different codification on OTU board

Publication Date:  2012-07-25 Views:  255 Downloads:  0

Issue Description

Customer installed the following scenario:
Site A - TN54NS3T01 board
Site B- TN54NS3T03 board

After installed and commissioned the both sides presented OTU3_LOF alarm. The performance of the channels are working normally, it was checked the BEF_FEC and AFT_FEC parameters in both sides were in 0. The OCH channel was not presenting alarms.
OSN8800 software version:
TN54NS3: 3.13

Alarm Information

The OTU3_LOF is an alarm indicating that the frame alignment signal(FAS) is abnormal. This alarm occurs when the frame alignment processing is out of frame (OOF) in three consecutive milliseconds.

Possible Causes

- The signals transmitted by the corresponding board at the opposite end do not have a frame structure.

- The input optical power is abnormal.



 - The FEC type is incorrectly configured.

 - The fiber of the transmission line is abnormal


Handling Process

It information was confirmed with R&D department through SR 1086690.

Root Cause

It was checked the possible causes of the problem and the root cause was not founded.

After we checked the board description according to the code we conclued:

One side the board was: TN54NS3T01 - the board works with DQPSK modulation mode

Another side the board was: TN54NS3T03 - the board works with ODB modulation mode

In this case the boards installed are presenting different modulation mode, that´s why the OTU3_LOF is appearing.


Install optical transponder unit same hardware version in both sides.