18-25
Cisco ONS 15454 DWDM Installation and Operations Guide, R6.0
August 2005
Chapter 18 Network Reference
18.7.1 Scenario 1: Fiber Cut in Nodes Using OPT-BST/OPT-BST-E Cards
Figure 18-11 Nodes Using OPT-BST/OPT-BST-E Cards
Two photodiodes at Node B monitor the received signal strength for the optical payload and optical
service channel (OSC) signals. When the fiber is cut, a loss of signal (LOS) is detected at both of the
photodiodes. The AND function then indicates an overall LOS condition, which causes the
OPT-BST/OPT-BST-E transmitter, OPT-PRE transmitter, and OSCM lasers to shut down. This in turn
leads to a LOS for both the optical payload and OSC at Node A, which causes Node A to turn off the
OSCM, OPT-PRE transmitter, and OPT-BST/OPT-BST-E transmitter lasers. The sequence of events
after a fiber cut is as follows (refer to the numbered circles in Figure 18-11):
1. Fiber is cut.
2. Node B power monitoring photodiode detects a Loss of Incoming Overhead (LOS-O) on the
OPT-BST/OPT-BST-E card and the OSCM card detects a LOS (OC3) at the SONET layer. Refer to
the Cisco ONS 15454 Troubleshooting Guide or the Cisco ONS 15454 SDH Troubleshooting Guide.
3. Node B power monitoring photodiode detects a Loss of Incoming Payload (LOS-P) on the
OPT-BST/OPT-BST-E card. Refer to the Cisco ONS 15454 Troubleshooting Guide or the Cisco ONS
15454 SDH Troubleshooting Guide.
4. On the OPT-BST/OPT-BST-E 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 Troubleshooting Guide or the Cisco ONS
15454 SDH Troubleshooting Guide.
5. The OPT-BST/OPT-BST-E card amplifier is shut down within three seconds.
6. The OSCM laser is shut down.
7. The OPT-PRE card automatically shuts down due to a loss of incoming optical power
OPT-BST/OPT-BST-E OPT-BST/OPT-BST-E
P
P
P
OSCM
PP
OSCM
= power monitoring photodiode
= logical AND function
Node A
Side B
Node B
Side A
X
11
1
7
13
10
9 8
12
6
2 3
4
5
2
8
120988
OPT-PRE
OPT-PRE
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