Incorrect Configuration of an Added Wavelength

During expansion, service interruption occurs in a normal wavelength on an OTU board and the corresponding OTU board reports OTU2_LOF alarm because of the incorrect wavelength configuration of an added wavelength.

Product

OptiX OSN 6800

OptiX OSN 8800

Fault Type

Service Interruption

OTU2_LOF

Symptom

When a 192.20 THz wavelength is added for expansion between sites F and G, the services on the 192.10 THz wavelength between sites B and G are interrupted. In addition, the corresponding OTU board at site G reports an OTU2_LOF alarm.

Figure 1 The Channel allocation of office T in V Network

Figure 2 The internal fiber connections of site F in V Network

Cause Analysis

The possible causes of the fault are as follows:

• The 192.10 THz OTU boards at sites B and G are faulty.
• The 192.10 THz OTU board at site G receives excessively low optical power.
• A 192.10 THz wavelength is introduced between sites B and G, thus resulting in conflicting wavelengths.

Procedure

1. Query the alarms and performance events of the 192.10 THz OTU boards at sites B and G.
   1. The performance of the OTU board at site B is normal, but the OTU2_BDI and ODU2_PM_BDI alarms are generated on the board.
   2. The OTU2_LOF, OTU2_SSF, and ODU2_PM_SSF alarms are generated on the OTU board at site G, but the receive optical power on the WDM side of the board is proper.
   
   Considering that the line power does not change, it is determined that the services may be interrupted due to an OTU2_LOF alarm on the WDM side of the OTU board at site G. Thus, the OTU boards at sites B and G may be faulty.
2. Sites B and G are left unattended. Thus, the OTU boards at the two sites cannot be tested by performing a fiber loopback on each of them. To restore the services in time, perform a cold reset on the OTU board at site B.
   1. When the OTU board at site B is cold reset, no R_LOS alarm is generated on the WDM side of the OTU board at site G but the OTU2_LOF alarm persists. In addition, the receive optical power on the WDM side of the board decreases from –8 dBm to –9.5 dBm.
   2. After the OTU board at site B is cold reset, the fault persists.
   
   The OTU board at site G may receive an excess 192.10 THz wavelength based on the preceding information.
3. Disable the laser on the WDM side of the OTU at site B to check whether the OTU board at site G still receives signals with optical power of –9.5 dBm. Then, disable the laser on the WDM side of the OTU board at site G and find that the receive optical power of the OTU board at site B is –60 dBm and that a R_LOS alarm is reported.
   An excess 192.10 THz wavelength may exist on the fiber from site B to site G.
4. Ask the customer whether the customer adds a board or changes a fiber connection on the live network during the time when the fault occurs.
   1. Check whether the customer has added an OTU board and established the corresponding physical fiber connection at site F to provide a 192.20 THz wavelength between sites F and G.
   2. Query the wavelength information about the new OTU board at site F and find that the wavelength is 192.10 THz and that the new OTU board is physically connected to the M40 optical interface on the TN11M40 board.
   
   The services on an existing wavelength are interrupted because the wavelength on the new board is set incorrectly.

Result

The problem is resolved.

Reference Information

Conclusions and suggestions for this case are as follows:

The NG WDM equipment uses the TN11RMU9 board for wavelength multiplexing. Conflicted wavelengths will result if wavelengths are planned or configured incorrectly. In this case, services on the equipment will be interrupted.

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