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An exception occurs when an MCA4 board scans optical channels

Publication Date:  2012-07-25 Views:  41 Downloads:  0
Issue Description
 An ROADM NE contains an MCA4 board. On the MCA4, the IN1 and IN2 interfaces are connected to the MON interfaces on the receiving and transmitting OAUs on side A. The IN3 and IN4 interfaces are connected to the MON interfaces on the receiving and transmitting OAUs on side B. On the IN1 and IN2 interfaces, however, the MCA4 finds two fabricated channels. The upstream site connected to side A does not transmit the two wavelengths. There are no cross-ring optical inputs. The optical cross-connection does not carry the two wavelengths. In addition, the MCA4 does not monitor the two wavelengths. The two wavelengths traverse the IN3 and IN4 interfaces. On the IN3 and IN4 interfaces, the scan results are correct. Perform a cold reset on the MCA4 on the T2000. The fault persists. 
Alarm Information
 The MCA4 reports the CHAN_ADD alarms for the two fabricated wavelengths on the IN1 and IN2 interfaces. 
Handling Process
 1. Check the fiber connections. It is found that the fibers are properly connected.
2. Remove the fibers connected to the IN1 and IN2 interfaces. The scan results on the IN1 and IN2 interfaces remain unchanged.
3. Remove the fibers connected to the IN3 and IN4 interfaces. The MCA4 finds nothing.
4. Connect the fiber previously connected to the IN2 interface to the IN3 interface. The scan results are correct. The MCA4 does not find the two fabricated channels previously found on the IN2 interface. Therefore, the problem may lie in the IN1 or IN2 interface.
5. Connect the fiber previously connected to the IN2 interface to the IN2 interface again. The fault persists. That is, the MCA4 finds the two fabricated channels again on the IN2 interface. The optical power and OSNR are the same as before.
6. Remove and then reinsert the MCA4. Connect all the fibers. The scan results become correct. Two days later, the scan results remain correct.
Therefore, the problem may be that some programs for data scan run into an infinite loop. As a result, the programs cannot release and update the scanned data. 
 
Root Cause
 The site consists of many NEs. Therefore, engineers doubt that some fibers are wrongly connected to the MCA4. To verify the doubt, increase the gain of the OAU on the upstream site connected to side A by 2 dBm. That is, increase the input power of the receiving OAU on the local NE by 2 dBm. Normally, the MCA4 should detect the change on the IN1 interface connected to the MON interface of the OAU. The scan results on the IN1 interface, however, remain unchanged. Therefore, the problem lies in wrong fiber connections. Move to the field to handle the fault. 
Suggestions
Null

END