10-26
Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 10 Network Reference
10.7.3 Fiber Cut Scenarios
Figure 10-17 Nodes Using OPT-AMP Cards
Two photodiodes at Node B monitor the received signal strength for the optical payload and OSC signals.
When the fiber is cut, an LOS is detected at both of the photodiodes. The AND function then indicates
an overall LOS condition, which causes the OPT-AMP-L card amplifier transmitter and OSCM card
OSC lasers to shut down. This in turn leads to an LOS for both the optical payload and OSC at Node A,
which causes Node A to turn off the OSCM card OSC and OPT-AMP-L card amplifier lasers. The
sequence of events after a fiber cut is as follows (refer to the numbered circles in Figure 10-17):
1. Fiber is cut.
2. The Node B power monitoring photodiode detects an LOS-P on the OPT-AMP-L card. Refer to the
Cisco ONS 15454 DWDM Troubleshooting Guide.
3. On the OPT-AMP-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-AMP-L card amplifier is shut down within one second.
5. The OSCM card laser is shut down.
6. The Node A power monitoring photodiode detects an LOS-O on the OPT-AMP-L card and the
OSCM card detects an LOS (OC3) at the SONET layer. Refer to the Cisco ONS 15454 DWDM
Troubleshooting Guide.
7. The Node A power monitoring photodiode detects an LOS-P on the OPT-AMP-L card. Refer to the
Cisco ONS 15454 DWDM Troubleshooting Guide.
OPT-AMP-L OPT-AMP-L
P
P
P
OSCM
PP
OSCM
= power monitoring photodiode
= logical AND function
Node A
Side B
Node B
Side A
X
10
1
7
9
8
11
6
2 3
4
5
2
8
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