Loopbacks

Overview

Alcatel-Lucent 1850 TSS-5 supports electronic port loopbacks and cross-connect (tributary) loopbacks.

Port loopbacks

Alcatel-Lucent 1850 TSS-5 supports DS1/E1, DS3/E3 facility and terminal electronic port loopbacks. The VLNC5x also supports OC-N/STM-N facility loopbacks. The VLNC35 circuit pack also supports Fast Ethernet terminal loopbacks.

Port loopbacks can be provisioned using the WaveStar^® CIT graphical display (VLNC35 and VLNC5x circuit packs) or the Web-based GUI/Command Line Interface (VLNC60/61/62 and VLNC64 circuit packs).

From the WaveStar^® CIT System View, select Fault → Analysis → Port Loopback and then select the circuit pack and the desired port. Choose either Facility or Terminal for Loopback Type and click on Operate or Release.

For a detailed description of the Command Line Interface (CLI) messages used to provision loopbacks on VLNC60/61/62 and VLNC64 circuit packs and general information about using the Command Line Interface (CLI), refer to Alcatel-Lucent 1850 Transport Service Switch (TSS-5) Command Line Interface Guide.

For a detailed description of the Web-based GUI used to provision loopbacks on VLNC60/61/62 and VLNC64 circuit packs and general information about using the Web-based GUI, refer to Alcatel-Lucent 1850 Transport Service Switch (TSS-5) CLI User Provisioning Guide.

The VLNC5x and VLNC60/61/62 circuit packs also support inband-requested DS1 loopbacks. Inband-requested DS1 loopbacks are provisioned using either inband signal control (ISC) patterns or a bit-oriented codes (BOC) within the DS1 signal received from the DSX or optical fiber. The ability to respond to inband loopback requests is provisionable on a per-port, per-direction basis, and is by default disabled. If inband loopbacks are enabled in either direction, then WaveStar^® CIT-based loopbacks (VLNC5x) or Web-based GUI/CLI-based loopbacks (VLNC60/61/62) are denied. If inband loopbacks are disabled while inband-requested loopbacks are active, the loopbacks are released.

The VLNC5x circuit packs also support Far End Alarm and Control (FEAC) requested DS1 and DS3 facility loopbacks on the channelized, C-bit framed, b-3 DS3 port. The FEAC-requested loopbacks are provisioned using FEAC codes within the b-3 DS3 signal received from the DSX. Requests may be accepted for the DS3 line, individual constituent DS1 signals, or all constituent DS1 signals simultaneously.

The ability to respond to FEAC loopback requests is provisionable on the b-3 DS3 port only, and is by default disabled. If FEAC-requested loopbacks are enabled, then WaveStar^® CIT-based facility loopbacks (VLNC5x) are denied. Terminal loopbacks are not denied. If FEAC-requested loopbacks are disabled while a FEAC-requested loopback is active, the loopback is released.

Active port loopbacks on the VLNC5x circuit pack are indicated by a continuously lighted ABN LED on the SYSCTL circuit pack. Clicking on the Alarm List button from the WaveStar^® CIT System View returns a report that indicates that loopbacks are present.

Facility loopbacks

A Facility loopback connects the incoming received signal to the transmitter in the return direction. Electrical signals are looped back intact, including BPVs. Optical signals are looped back after the optical to electrical conversion.

The VLNC5x circuit pack supports facility loopbacks on DS1/E1, DS3/E3, and OC-n/STM-n interfaces only.

The VLNC60/61/62 and VLNC64 circuit packs support facility loopbacks on DS1 and E1 interfaces only.

The following figure shows a facility loopback used in a test arrangement with an external test set.

Figure 4-2: Facility loopback example

Terminal loopbacks

A Terminal loopback connects the entire signal that is about to be transmitted back into the associated incoming receiver.

The VLNC5x circuit pack supports terminal loopbacks on DS1, E1, DS3, and E3 interfaces only.

The VLNC60/61/62 and VLNC64 circuit packs support terminal loopbacks on DS1 and E1 interfaces only.

The VLNC35 circuit pack supports terminal loopbacks on Fast Ethernet LAN ports.

The following figure shows a terminal loopback used in a test arrangement with an external test set.

Figure 4-3: Terminal loopback example

Cross-connect (tributary) loopbacks

A Cross-Connect loopback connects the incoming received tributary to the outgoing transmitted tributary in the return direction.

Cross-connect loopbacks can be provisioned using the WaveStar^® CIT graphical display (VLNC5x circuit packs).

From the WaveStar^® CIT System View, select Fault → Analysis → Cross-Connect Loopback and then select the circuit pack and the desired port. Click on Operate or Release.

Unconnected tributaries on an OC-N/STM-N interface may be looped back at any rate for which a cross-connection would be allowed for that tributary. For example, in SONET shelves, m1-1-1 may be looped back at the STS1 rate, or at the STS3c rate if tributaries 2 and 3 are also unconnected. Any unconnected VT1.5 may be looped back.

Connected tributaries on an OC-N/STM-N interface may be looped back at the connected rate, if the loopback Command Mode is Forced as part of the loopback request. AIS is inserted toward the output direction on that side.

If a cross-connection exists before the loopback is created, the cross-connection is restored once the loopback is released. Any number of tributaries can have a cross-connect loopback at the same time.

The VLNC5x circuit pack supports cross-connect loopbacks on any tributary (STSN/VT1.5/VCN).

The following figure shows a cross-connect loopback used in a test arrangement with an external test set.