Intermittent BEFFEC_EXC Alarm at IN/OUT optical interfaces on LWF board

The intermittent BEFFEC_EXC alarm is reported at IN/OUT optical interfaces on the LWF board housed in slot 10 of one surack NE.

Product

OptiX BWS 1600G, WDM,OSN 6800,OSN 8800

Fault Type

Optical Transponder Unit

BEFFEC_EXC

Symptom

The intermittent BEFFEC_EXC alarms are reported at the IN/OUT optical interfaces on the LWF board housed in slot 10 of one surack NE.

Initial operations:

• Check connection.
• Replace MR2 board in slot 8, which is connected with the IN optical interface of LWF board.
• Still alarm at NMS.

Expected operations from vendor:

• Clear the Problem
• Provide User Guide (faulty description and problem handling)
• Provide Maintenance Manual Books

Cause Analysis

The LWF board has the FEC function of correcting bit errors generated in the transmission over DWDM equipment. If the number of bit errors is beyond FEC correction ability, the number of uncorrectable bit errors and alarms is reported.

Then, initialize the current performance data and observe the NMS after a certain period. The NMS shows that the channels that report bit errors and number of bit errors are not stable.

If bit errors occur in one direction, it indicates that the fault is related to unidirectional optical fibers or boards. In this case, only the local station has bit errors. This means that the fault happens only in one direction.

Procedure

1. Query performance events
2. After 15m performance, bit errors occur in local station for the signals that are received from the opposite station and pass through 5 OLA stations. The channels that report bit errors and number of bit errors are not stable.
3. No bit error occurs on the signals sent from the opposite station to the local station.
4. Conclusion: Bit errors occur in one direction.
5. Check optical power.
   1. Check the optical power of the amplifier at each station on the NMS. The optical power is identical with the value specified during engineering commissioning.
   2. Check optical power of the LWF at the local station on the NMS. The optical power is identical with the value specified during engineering commissioning.
6. Adjust optical power:
   1. Adjust the optical power. With OSNR guaranteed, increase the input optical power of the optical fiber with bit errors. Observe the variation of the number of bit errors on the NMS. It shows the number of bit errors increases with the optical power. Reduce the input optical power of the fiber. It shows that the number of bit errors decreases with the optical power.
7. Check the transmit power of the LWF board in slot 10 in the local station, which the transmission direction is from the opposite station to the local station. Trace step by step each site the OAU receiving power and transmit go to the local station also power gain. Make sure the power receive and power transmit adjust equally or difference is not significant.
8. The launched optical power of the upstream station is excessively high about +15 dBm and the OAU gain +28 dB.
9. The bit errors are caused by the non-linearity of optical fiber. Reduce the input optical power in the local station and bit error problem is solved.

Reference Information

None.

More related:

When Incorrect Fan Rotation Speed Adjustment of the OptiX OSN NG WDM Products

When Interruption of Existing Services on Some Data Boards of OSN Products

How to do when Bit Errors Occur in Lower Order Path Due to Improper Grounding