Troubleshooting Optical Circuit Paths With Loopbacks - Cisco ONS 15600 SDH Troubleshooting Manual

1.2 Troubleshooting Optical Circuit Paths With Loopbacks

Figure 1-4
Test Set
This test can be conducted locally or remotely through the CTC interface without on-site personnel. It
takes place on an STM-16, STM-64, or ASAP port and tests the traffic path on that VC circuit through
the port and SSXC. The signal path is similar to a facility loopback.
The XC loopback breaks down the existing path and creates a new cross-connect—a hairpin—while the
source of the original path is set to inject a line-side AIS-P. The signal path and AIS injection are shown
in Figure
Figure 1-5
External signals from
and to other equipment
If a terminal or facility loopback exists on a port, you cannot create an XC loopback on it.
Note
When testing STM-64 signals with jitter analyzers, be sure to verify with the manufacturer that you are
Note
using the most current test equipment. Some test equipment has demonstrated false high jitter readings
caused by accumulated jitter dependencies within the test equipment.
1.2 Troubleshooting Optical Circuit Paths With Loopbacks
Facility loopbacks or payload loopbacks, terminal loopbacks, and cross-connect (XC) loopback circuits
are often used together to test the circuit path through the network or to logically isolate a fault.
Performing a loopback test at each point along the circuit path systematically isolates possible points of
failure.
The procedures in this section apply to STM-16, STM-64, and ASAP optical ports. (For instructions on
ASAP Ethernet ports, go to the
on page
Cisco ONS 15600 SDH Troubleshooting Guide, R8.0
1-6
Cross-Connect Loopback Path on an STM-N Port
STM-Nx SSXC STM-Ny
x
1-5.
Network Element with SDH Cross-Connect Loopback Function
unlocked
"1.3 Troubleshooting an Ethernet Circuit Path With Loopbacks" section
1-29.) The example in this section tests an STM-N circuit on a three-node MS-SPRing. Using a
Equipment to perform
framing, scrambling, etc.
(such as signal terminating equipment)
O/E R
E/O T
Chapter 1 General Troubleshooting
AIS
Internal signals to and from
other equipment in the NE
July 2010