10-25
Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 10 Network Reference
10.7.3 Fiber Cut Scenarios
in turn leads to an LOS for both the optical payload and the OSC at Node A, which causes Node A to
turn off the OSCM OSC transmitter and OPT-BST-L amplifier lasers. The sequence of events after a fiber
cut is as follows (refer to the numbered circles in Figure 10-16):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects an LOS-P on the OPT-BST-L card. Refer to the
Cisco ONS 15454 DWDM Troubleshooting Guide.
3. On the OPT-BST-L card, the simultaneous LOS-O and LOS-P detection triggers a command to shut
down the amplifier. CTC reports an LOS alarm (loss of continuity), while LOS-O and LOS-P are
demoted. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide.
4. The OPT-BST-L card amplifier is shut down within one second.
5. The OSCM laser is shut down.
6. The OPT-AMP-L, OPT-AMP-C, or OPT-AMP-17-C card automatically shuts down due to a loss of
incoming optical power.
7. The Node A power monitoring photodiode detects an LOS-O on the OPT-BST-L card and the OSCM
card detects an LOS (OC3) at the SONET layer. Refer to the Cisco ONS 15454 DWDM
Troubleshooting Guide.
8. The Node A power monitoring photodiode detects an LOS-P on the OPT-BST-L card. Refer to the
Cisco ONS 15454 DWDM Troubleshooting Guide.
9. On the OPT-BST-L, the simultaneous LOS-O and LOS-P detection triggers a command to shut down
the amplifier. CTC reports an LOS alarm (loss of continuity), while the LOS-O and LOS-P are
demoted. Refer to the Cisco ONS 15454 DWDM Troubleshooting Guide.
10. The OPT-BST-L card amplifier is shut down within one second.
11. The OSCM laser is shut down.
12. The Node A OPT-AMP-L, OPT-AMP-C, or OPT-AMP-17-C card automatically shuts down due to
an LOS for the incoming optical power.
When the fiber is repaired, either an automatic or manual restart at the Node A OPT-BST-L transmitter
or at the Node B OPT-BST-L transmitter is required. A system that has been shut down is reactivated
through the use of a restart pulse. The pulse indicates the optical path is restored and transmission can
begin. For example, when the far end, Node B, receives a pulse, it signals to the Node B OPT-BST-L
transmitter to begin transmitting an optical signal. The OPT-BST-L receiver at Node A receives that
signal and signals the Node A OPT-BST-L transmitter to resume transmitting.
Note During a laser restart pulse, APR ensures that the laser power does not exceed Class 1 limits. See the
“10.7.2 Automatic Power Reduction” section on page 10-19 for more information about APR.
10.7.3.4 Scenario 4: Fiber Cut in Nodes Using OPT-AMP-L, OPT-AMP-C, or OPT-AMP-17-C (OPT-LINE
Mode) Cards
Figure 10-17 shows nodes using OPT-AMP-L, OPT-AMP-C, OPT-AMP-17-C (in OPT-LINE mode)
cards with a fiber cut between them.
Note A generic reference to the OPT-AMP card also refers to the OPT-AMP-L, OPT-AMP-17-C or
OPT-AMP-C cards.
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