R_LOS Is Reported by a Line Board on a Regular Basis Because of Incorrect Wavelength Monitoring Configuration on the Electrical Regeneration NE (NG WDM Equipment)

R_LOS is reported by a line board on a regular basis because of incorrect wavelength monitoring configuration on the electrical regeneration NE.

Product

OSN 6800, OSN 8800

Fault Symptom

On network L of operator Y in country Z, the TN52ND2 board in slot 4 on NE A reported an R_LOS alarm for its optical port 1 at a specific time in every early morning (00:00–06:00). In addition, on the peer NE (NE B), the TN52ND2 board in slot 6 reported a WAVELEN_OVER alarm for its optical port 1. After a field inspection of the NE configurations, Huawei frontline engineer determined that the wavelength monitoring configuration on NE B was incorrect. After the configuration was corrected, the TN52ND2 board on NE B stopped reporting the WAVELEN_OVER alarm, but the R_LOS alarm on NE A was still reported on a regular basis.

Network Topology

Cause Analysis

As the TN52NQ2 board reported an R_LOS alarm at a specific time in every early morning (00:00–06:00), one can determine that a wavelength drift had occurred on the TN52NQ2 board of the peer NE.

If the wavelength monitoring configuration of the TN52NQ2 board on the peer NE is correct, then there are the following possible causes:

• A multi-NE wavelength locking function has been configured for the TN52NQ2 board on the peer NE and the configuration is incorrect.
• The logical and physical fiber connections between the two NEs are inconsistent.
• An electrical regeneration NE is located between NEs A and B, as shown in the following figure, and the wavelength monitoring configuration on this NE is incorrect.

Procedure

1. Checked the NE monitoring configuration of other NEs on the network. The multi-wavelength locking function was not configured for these NEs.
2. Sent test TTI bytes from optical port 1 on the TN52ND2 board in slot 6 of NE B to optical port 1 on the TN52ND2 board in slot 4 of NE A.
   1. When test TTI bytes were sent in the SM section, optical port 1 on the TN52ND2 board in slot 4 of NE A had not received any TTI bytes.
   2. When test TTI bytes were sent in the PM section, optical port 1 on the TN52ND2 board in slot 4 of NE A received the TTI bytes.
   Based on the preceding information, Huawei determined that an electrical regeneration NE was located between NEs A and B.
   The following describes how to set and check test TTI bytes:
   1. 1. Start the NE Explorer of the transmitting NE, select the board that you use to transmit TTI bytes, and choose OTN Overhead Management > SM Overhead or OTN Overhead Management > PM Overhead.
      
   2. Enter a required value in TTI to be Sent on the right of the window.
      
   3. Start the NE Explorer of the receiving NE, select the board for receiving the TTI bytes, and choose OTN Overhead Management > SM Overhead or OTN Overhead Management > PM Overhead.
   4. Check the value of TTI Received to see whether it is the same as the value of TTI to be Sent.
      
3. Confirmed that the TTI bytes from optical port 1 on the TN52ND2 board in slot 6 of NE B to optical port 1 on the TN52ND2 board in slot 4 on NE A traversed an electrical regeneration NE. Checked that the wavelength monitoring configuration on this NE was incorrect.
4. Correctly the wavelength monitoring configuration for the regeneration NE. Then the TN52ND2 board on NE A stopped reporting the R_LOS alarm.

Conclusion and Suggestion

When a line board on an NE reports an R_LOS alarm at a regular basis, if the wavelength monitoring configuration on the peer NE is correct, check whether:

• The logical and physical fiber connections between the two NEs are consistent.
• An electrical regeneration NE is located between the two NEs.

The following provides the check methods:

1. To check whether the logical and physical fiber connections are consistent, send TTI bytes in the PM section between the two NEs.
2. To check whether an electrical regeneration NE is located between the two NEs, send TTI bytes in the SM section between the two NEs

When the data communication is unavailable or interrupted intermittently, or when packet loss occurs, check the working mode of the interconnected ports. In most cases, the problem is due to the mismatch of the port working modes at the two ends.

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