Cisco ONS 15454 DWDM Manual page 69

Chapter 1 General Troubleshooting
1.12.2 System Restart after a Fiber Cut
When the network ALS setting is Auto Restart, the system automatically restarts after a fiber cut occurs.
MSTP system restart after a fiber cut is a fully automatic process regulated by a chronological sequence
of steps including the OSC link built-in amplifiers restart and amplifier power control (APC) regulation.
The successful completion of system restart is strictly related to possible changes of the insertion loss
value of the repaired span. A change in insertion loss is dependent on many factors, including the process
of physically repairing the fiber, a change in fiber length after repair, and so on.
Four different scenarios related to span loss are presented in this section:
1.
2.
3.
4.
It is also possible that span loss decreased, but this is unlikely. This condition does not prevent the MSTP
Note
system automatic restart process, but can lead (potentially) to issues downstream of the repaired span,
for example, a Power Overload condition on the OSC receiver or on the Trunk-RX port of a TXP or MXP
card.
These conditions are identified by specific alarms (see the "HI-RX-POWER" section of
"Alarm Troubleshooting"
The symptoms of the possible span loss scenarios (except for span loss decrease) are described in the
following paragraphs. Refer to the linear network in
the scenarios.
The basic assumption is that the network ALS feature (for feature details, refer to the "Network Optical
Safety––Automatic Laser Shutdown" section in the Cisco ONS 15454 DWDM Reference Manual) is
active (ALS Mode = Auto Restart on the OPT-BST [+ OSCM] and OSC-CSM). Given this assumption,
the starting condition is as shown in
The system behavior when the network ALS Mode is DISABLE is a subcase that requires a manual
restart after repairing a single fiber in only one line direction.
The network ALS feature is a function of the ALS Mode settings of the OPT-BST, OPT-BST-E,
Note
OPT-BST-L, OPT-AMP-L, OSCM, and OSC-CSM cards. For the network ALS Mode to be disabled,
each of these cards must have its ALS Mode set to DISABLE.
1.12.2.1 Scenario 1: Span Loss Change > 5 dBm and OSC Power Value on the Receiver < –42 dBm
In network view, both of the lines representing the span remain gray as long as the status of the OCHNC
circuits relating to the repaired span remain in Partial state.
78-17742-02
Span loss increased:
Span loss change > 5 dBm
•
OSC power value on the receiver < –42 dBm
•
Span loss increased:
Span loss change > 5 dBm
•
• OSC power value on the receiver > –42 dBm
Span loss increased: 3 dBm < span loss change < 5 dBm
Span loss increased: span loss change < 3 dBm
of the DWDM Alarm and Troubleshooting Guide).
Figure 1-21 on page 1-61
Figure 1-22 on page 1-62.
Cisco ONS 15454 DWDM Troubleshooting Guide, R7.0.1
1.12.2 System Restart after a Fiber Cut
Chapter 2,
during the discussion of
1-69