Analysis of the Anomaly Occurring When an MCA4 Board Scans Optical Channels and the Board Reports the CHAN_ADD Alarm

This case describes how to handle the anomaly that occurs when an MCA4 board scans optical channels.

Product

OptiX OSN 6800

OptiX OSN 8800

OTN

Fault Type

Spectrum Analyzer Unit

CHAN_ADD

Symptom

An ROADM NE is configured with an MCA4 board. On the MCA4 board, the IN1 and IN2 interfaces are connected to the MON interfaces on the OAU in the receive direction and the OAU in the transmit direction on the east direction. The IN3 and IN4 interfaces are connected to the MON interfaces on the OAU in the receive direction and the OAU in the transmit direction on the west direction.

At the IN1 and IN2 interfaces, however, two extra wavelengths are found, as they are not found in the wavelengths from the upstream site. Besides, there is no other inter-ring input, and no existing optical cross-connection involves the two wavelengths. In addition, the two wavelengths are not covered in the wavelengths that should be monitored by MCA4 board as the configuration. In this case, the two wavelengths should traverse the IN3 and IN4 interfaces. At the IN3 and IN4 interfaces, however, the two wavelengths are found and the scanned data is correct.

After a cold reset is performed on the MCA4 on the T2000, the fault persists.

The MCA4 board reports the CHAN_ADD alarms for the two extra wavelengths at the IN1 and IN2 interfaces.

Cause Analysis

Based on the preceding description, the MCA4 has entered an infinite loop when processing certain programs for data scan. As a result, the programs cannot release and update the scanned data.

Procedure

1. The site with the fault consists of many NEs. Therefore, at first the field engineers suspect that fibers on the MCA4 board are connected improperly. To verify this, increase the gain of the OAU on the upstream site connected to the east direction by 2 dBm. That is, the input power of the OAU in the receive direction is increased by 2 dBm. Normally, the MCA4 should detect the change at the IN1 interface connected to the MON interface on the OAU. The scan result at the IN1 interface, however, remains unchanged.
2. Check the fiber connections on the MCA4 board on site. It is found that the fibers are properly connected. Remove the fibers connected to the IN1 and IN2 interfaces. The scan result at the IN1 and IN2 interfaces remains unchanged.
3. Remove the fibers connected to the IN3 and IN4 interfaces and check the scan result of the IN1 to IN4 interfaces. It is found that no power is output.
4. Connect the fiber that is previously connected to the IN2 interface to the IN3 interface. The scan result of the IN3 interface is normal, and no extra wavelengths are found at the IN2 interface. Therefore, the problem may be caused by the IN1 or IN2 interface.
5. Restore the fiber to the IN2 interface and check the scan result of the IN2 interface. The fault recurs.
6. Reseat the MCA4 board, and then connect all the fibers on the board properly. The scanned data at all interfaces on the board is normal.

Result

The problem is solved after the operation is finished as the requests.

Two days later, perform the test again and it is found that the scanned data remains correct.

Reference Information

None.

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