OSN3500 Setup SDH Optical Interface Board Loopback The loopback operation reverses the down-plug AIS signal. In the unprotected state, the loopback may cause service interruption or communication signal interruption. The loopback operation can only be used for fault localization. the loopback setting for that port must be cleared after fault localization. the N1 series line veneer (veneer total capacity of STM-16 and below) internal loopback causes ECC loopback. An external loopback on an optical interface does not change the signal structure. Inside the optical interface board, the signal from the optical receiver module is looped back directly to the optical transmitter module at the SDH interface (before signal processing). It can be used to judge whether the SDH interface and the fiber cable connected to the SDH board are normal or not. the VC-4 outer loopback does not change the signal structure. Inside the optical interface board, the VC4 signal from the optical receiver module is looped back directly to the optical transmitter module in the VC4 channel (before signal processing). It can be used to judge whether the VC4 channel in the SDH interface and the fiber cable connecting the SDH single board is normal. If you need to set SDH optical interface board optical port external/internal loopback, select the port that needs to be looped back, and then select "Internal Loopback" or "External Loopback" in the drop-down menu in the corresponding right column. If you need to set SDH optical interface board VC-4 external/internal loopback, select the VC-4 that needs to be looped back, and select "Internal Loopback" or "External Loopback" in the drop-down menu in the corresponding right column.

Loopback is used for fault localization. The external loopback can be used to test whether the interface module and external fiber cable of the single board are normal, while the internal loopback can be used to test whether the cross-connection unit and service path of the equipment are normal. This task describes how to perform the loopback operation of the SDH optical interface board.

Prerequisites

The user has the network management user privilege of "Network Element and Network Operator" or higher.

Impact on the system

Loopback operation reverses the downward insertion of AIS signals. In an unprotected state, loopback may cause a service interruption or communication signal interruption.

The loopback operation can only be used for fault localization, and the loopback setting for that port must be cleared after fault localization.

Internal loops in N1 series line veneers (veneers with a total capacity of STM-16 and below) can cause ECC loopbacks.

Tools, Instruments, and Materials

U2000

Background information

OptiX OSN equipment supports SDH optical interface board outer loopback and inner loopback.

Table 1 Schematic diagram of the optical interface board outer loopback

Loopback point	Explanation	Legend
SDH Optical Interface Board Outer Loopback of Optical Port	The external loopback of the optical interface does not change the signal structure. Inside the optical interface board, the signal from the optical receiver module is looped back directly to the optical transmitter module at the SDH interface (before signal processing). It can be used to determine whether the SDH interface and the fiber cable connected to the SDH board are normal.
SDH Optical Interface Board VC-4 External Loopback	The VC-4 external loopback does not change the signal structure. Inside the optical interface board, the VC4 signal from the optical receiver module is looped back directly to the optical transmitter module in the VC4 channel (before signal processing). It can be used to determine whether the VC4 channel in the SDH interface and connecting SDH single board fiber cable is normal.

Table 2 Schematic diagram of loopback in the optical interface board

Loopback point	Explanation	Legend
SDH Optical Interface Board Intra-Optical Loopback	The inner loopback of the optical interface undergoes signal processing in the local unit. Inside the optical interface board, signals from the cross-connection unit are looped back to the cross-connection unit at the SDH interface (after signal processing). It can be used to determine whether the SDH board service processing module and the cross-over board are normal.
SDH Optical Interface Board VC-4 Internal Loopback	The VC-4 internal loopback undergoes signal processing in the local unit. Inside the optical interface board, the VC-4 signals from the cross-connection unit are looped back in the VC-4 channel (after signal processing) to the cross-connection unit. It can be used to determine whether the SDH board service processing module and the cross-over board are normal.

Operation Steps

1. Double-click the Main Topology icon in the Workbench view to enter the main topology diagram.
2. Right-click on the network element icon and select "Network Element Manager".
3. Select the optical interface board that needs to be looped back, and select "Configuration > SDH Interface" in the Function Tree.
4. Select "By Function", according to the actual need, you can set different loopback functions for SDH optical interface board.
   • If you need to set the loopback function of SDH optical interface board's optical port, select "Optical (Electrical) Port Loopback" in the drop-down menu.
   • If you need to set SDH optical interface board VC-4 loopback, select "VC4 Loopback" in the drop-down menu.
5. According to the actual need, you can set different loopback types of SDH optical interface board.
   • If you need to set the external/internal loopback of the SDH optical interface board optical port, select the port to be looped back, and choose "Internal Loopback" or "External Loopback" in the drop-down menu in the corresponding right column.
   • If you need to set SDH optical interface board VC-4 external/internal loopback, select the VC-4 that needs to be looped back, and choose "Internal Loopback" or "External Loopback" in the drop-down menu in the corresponding right column.
6. Click "Apply", the "Confirm" dialog box will pop up, click "OK". The "Prompt" dialog box pops up, click "OK".
7. The "Result" dialog box pops up, click "Close".
8. Option: Undo Loopback. Set the loopback method to "No Loopback".