Figure - Cisco ONS 15454 Troubleshooting Manual

1.1.2 Terminal Loopbacks

Figure 1-6

optical card and travels through the cross-connect card to the electrical card. The terminal loopback on
the electrical card turns the signal around before it reaches the LIU and sends it back through the
cross-connect card to the optical card. This test verifies that the cross-connect card and terminal circuit
paths are valid, but does not test the LIU on the electrical card.
CTC sometimes refers to terminal loopbacks as terminal (inward) loopbacks. "Inward" is meant to
Note
clarify that the loopback signal travels inward toward the facility where it originates and not outward
toward the span.
Figure 1-6
1.1.2.2 ONS 15454 Card Behavior
ONS 15454 terminal port loopbacks can either terminate or bridge the signal. In the ONS 15454 system,
all optical, electrical, Ethernet, and FC_MR-4 terminal loopbacks are terminated as shown in
During terminal loopbacks, some ONS 15454 cards bridge the loopback signal while others terminate it.
If a port terminates a terminal loopback signal, the signal only loops back to the originating port and is
not transmitted downstream. If the port bridges a loopback signal, the signal loops back to the originating
port and is also transmitted downstream.
Table 1-2
In Table
Note
AIS is injected downstream for all cards except Ethernet cards.
Table 1-2
Card/Port
DS-1
DS-3
DS3XM-6 or DS3XM-12
All OC-N cards
EC-1
G-Series Ethernet
1. G-Series Ethernet terminal loopback is terminated and Ethernet transmission is disabled. No
Cisco ONS 15454 Troubleshooting Guide, R8.5
1-6
shows a terminal loopback on a DS-N electrical card. The test-set traffic comes in on the
Terminal Loopback Path on a DS-N Card
DS-N XC OC-N
lists ONS 15454 card terminal loopback bridging and terminating behaviors.
1-2, no AIS signal is injected if the signal is bridged. If the signal is terminated, an applicable
ONS 15454 Card Terminal Loopback Behavior
AIS is inserted for Ethernet, but a TPTFAIL alarm is raised on the far-end Ethernet port.
Test Set
Terminal Loopback Signal
Terminated
Bridged
Bridged
Bridged
Bridged
1
Terminated
Chapter 1 General Troubleshooting
Table
November 2009
1-2.