Cisco ONS 15454 - 1.1.2.2 ONS 15454 Card Behavior

1-6
Cisco ONS 15454 Troubleshooting Guide, R8.5
November 2009
Chapter 1 General Troubleshooting
1.1.2 Terminal Loopbacks
Figure 1-6 shows a terminal loopback on a DS-N electrical card. The test-set traffic comes in on the
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.
Note CTC sometimes refers to terminal loopbacks as terminal (inward) loopbacks. “Inward” is meant to
clarify that the loopback signal travels inward toward the facility where it originates and not outward
toward the span.
Figure 1-6 Terminal Loopback Path on a DS-N Card
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 Table 1-2.
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 lists ONS 15454 card terminal loopback bridging and terminating behaviors.
Note In Table 1-2, no AIS signal is injected if the signal is bridged. If the signal is terminated, an applicable
AIS is injected downstream for all cards except Ethernet cards.
DS-N
Test Set
XC OC-N
78259
Table 1-2 ONS 15454 Card Terminal Loopback Behavior
Card/Port Terminal Loopback Signal
DS-1 Terminated
DS-3 Bridged
DS3XM-6 or DS3XM-12 Bridged
All OC-N cards Bridged
EC-1 Bridged
G-Series Ethernet Terminated
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1. G-Series Ethernet terminal loopback is terminated and Ethernet transmission is disabled. No
AIS is inserted for Ethernet, but a TPTFAIL alarm is raised on the far-end Ethernet port.