The ODUk SNCP Protection Is Abnormal due to Incorrect Fiber Connections

The ODUk SNCP protection is abnormal due to incorrect fiber connections.

Product

OptiX OSN 8800

OptiX OSN 6800

OptiX OSN 3800

Fault Type

Protection

Symptom

The OptiX OSN 6800 is tested in an office. The tributary board is TQS, the line board is NS2, and the host version is 5.51.3.25.

One STM-16 service is configured between sites A, B, and C. The service is dropped at site A and site C, and ODUk SNCP protection is configured for the service. The service is configured to pass through site B at the electrical layer and wavelength 15 is used to transmit the service.

The test shows that the protection channel of ODUk SNCP protection between site A and site C is in the SF state and the working channel is normal.

Cause Analysis

The possible causes of the fault are as follows:

• The pass-through service at site B is not configured or configured incorrectly.
• The fiber connections are incorrect.

Procedure

1. Check the service at site B and it is found that ODU1 cross-connections and service between two NS2 boards are configured correctly.
2. On MCA boards at sites A, B, and C, scan all monitoring points of this channel to check for the optical power of wavelength 15. The optical power of wavelength 15 is scanned.
3. Set OTN overheads on the two NS2 boards at sites A and B. Change the TTI byte in the SM overhead to A-slot ID-NS2 and B-slot ID-NS2. The corresponding two NS2 boards can detect the bytes transmitted from the opposite end, which indicates that the optical channel from site A to site B is normal.
4. Repeat the preceding step to set the OTN overheads for the two interconnected NS2 boards at site B and site C. The two NS2 boards fail to receive the TTI byte from the opposite end. This indicates that the optical channel from site B to site C is abnormal. Optical fibers may be connected incorrectly.
5. Check fiber connections at the sites. It is found that optical fibers are connected incorrectly at site C. Adjust fiber connections according to the network design. Then, the fault is rectified.

Result

The problem is resolved.

Reference Information

Conclusions and suggestions for this case are as follows:

• A fault cannot be located accurately only by checking alarms and scanning wavelengths because no optical-layer alarm is reported.
• Modifying the TTI byte is an important means of checking fiber connection correctness of NG WDM equipment.
• The correctness of fiber connections must be ensured in WDM engineering.

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