Cisco NCS 2000 series Troubleshooting Manual page 112

General Troubleshooting
Scenario 1: Span Loss Change > 5 dBm and OSC Power Value on the Receiver less than –42 dBm
The symptoms of the possible span loss scenarios (except for span loss decrease) are described in the following
paragraphs. Refer to the linear network given below during the discussion of the scenarios.
Figure 14: Linear Network, With No Fiber Cut
The basic assumption is that the network ALS feature (for feature details, refer to the Network Optical
Safety––Automatic Laser Shutdown section in the Network Reference chapter of the Configuration guide) is
active (ALS Mode = Auto Restart on the OPT-BST, OPT-AMP-C, OPT-AMP-17-C, [+ OSCM] and
OSC-CSM). Given this assumption, the starting condition is as shown in Figure 1.
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.
Scenario 1: Span Loss Change > 5 dBm and OSC Power Value on the Receiver less than –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.
In node view (single-shelf mode) or shelf view (multishelf mode), the alarm panels of the two nodes (ROADM
and OLA in this example) show the LOS (OTS or AOTS) condition on the LINE-RX port of the OPT-BST,
OPT-AMP-C, OPT-AMP-17-C, or OSC-CSM.
An EOC condition is always present on both nodes because the OSC optical link is down due to an incoming
power level lower than the optical sensitivity limit (–42 dBm). The system condition remains unchanged.
Every 100 seconds, the ALS protocol turns up the OSC TX laser in a pulse mode (pulse duration = 2 seconds),
but the excessive loss on the span prevents the OSC link from synchronizing, and the MSTP system remains
unoperational.
Note During the attempt to restart, a valid power value is reported by the OSC transmit card (in the example, the
OSC-CSM in the OLA node), but on the OSC receive card (the OSCM in the ROADM node), the alarm
condition persists.
Cisco NCS 2000 series Troubleshooting Guide, Release 11.0
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