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Cisco ONS 15454 DWDM Troubleshooting Guide, R7.0.1
78-17742-02
Chapter 1 General Troubleshooting
1.12.2 System Restart after a Fiber Cut
The reactivation of the OCHNC circuits relating to the repaired span (the status changes from Partial to
Complete) can lead to several final conditions that depend on the network topology and node layout.
The rebuilding of circuits automatically triggers the APC check mechanism (for details, refer to the
“Network Reference” chapter of the Cisco ONS 15454 DWDM Reference Manual). The APC check
mechanism impacts the optical gain of the amplifiers (primarily the OPT-PRE card) and the VOA express
attenuation for the optical add/drop multiplexing (OADM) cards. The APC application acts on the
appropriate cards downstream of the repaired span (for each line direction), and attempts to compensate
for the introduction of excess loss.
Because the loss increase exceeds the maximum variation (+/–3 dBm) for which APC is allowed to
compensate, an APC-CORRECTIO N-SKIPPED condition is raised by the first node along the flow
detecting the event. The condition panel of the impacted node (the ROADM, in this example) reports the
APC-CORRECTION-SKIPPED condition and indicates the port or card to which it applies.
To correct Scenario 3:
Step 1 Verify the alarm validity.
Step 2 For both DWDM nodes connected to the repaired span:
a. Double-click the card reporting the issue.
b. Click Conditions.
c. Click Retrieve and verify that an APC-CORRECTION-SKIPPED condition is present on an
aggregate port.
d. If the alarm is correctly reported, go to Step 3. If not, close the CTC application, delete the CTC
cache, and open the CTC connection again. Then, go to Step 1.
Note If the discrepancy persists, log into the Technical Support Website at
http://www.cisco.com/techsupport for more information or call Cisco TAC (1 800 553-2447) in
order to report a service-affecting problem.
Step 3 Measure the new Span Loss value after the fiber has been repaired.
a. In the node view (single-shelf mode) or shelf view (multishelf mode) of both nodes of the span, click
the Maintenance > DWDM > WDM Span Check tabs.
b. Click Retrieve Span Loss Values to retrieve the latest loss data.
Note The two values retrieved at each node level (west side and east side) refer to the two fibers
coming into the node from the adjacent nodes, so they apply to different spans. To complete the
measurement in Step 4, the appropriate values must be taken into account.
Step 4 Compare the Span Measurements of the previous step with the Span Losses values used during the
network design with Cisco MetroPlanner.
Step 5 For the two fibers belonging to the repaired span, identify the one for the W–E line direction. If the Span
Loss Change is greater than 3 dB, continue with Step 6. If not, go to Step 9.
Step 6 Clean the LINE-RX and LINE-TX connectors of the DWDM cards that manage the fiber of the repaired
span. If the problem persists, continue with Step 7. Otherwise, you are finished with the corrective
action.
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