Setting a Loopback for a VC3 Path (RTN NEs)

The VC3 path loopback is a common fault location method to test and maintain the board. The VC3 path loopback is used to test the fiber connections and SDH interfaces on the board, and is also used to test the SDH service processing module and the cross-connect board.

Context

The VC3 path loopback can be set to an outloop or an inloop.

When an outloop is used, the VC3 signal received by the NE is returned over the VC3 path. In Figure 1, an outloop is set for the first VC3 path in the first VC4 path on the STM-1 line board. An outloop is used to test the fibers connections and interfaces on the SDH board.
Figure 1 Outloop
When an inloop is used, the VC3 signal transmitted by the NE is returned over the VC3 path. In Figure 2, an inloop is set for the first VC3 path in the first VC4 path on the STM-1 line board. An inloop is used to test the SDH service processing module and the cross-connect board.
Figure 2 Inloop

NOTICE:

As an loopback interrupts services, it is only used for fault location and must be released after the fault is removed.

Procedure

In the NE Explorer, select a board and choose Configuration > SDH Interface from the Function Tree.
NOTE:
For the intermediate frequency board: In the NE Explorer, select the board and choose Configuration > Digital Interface from the Function Tree.
Select By function and select VC3 Loopback.
Select an SDH interface from the list and double-click VC3 Loopback to choose the loopback mode.
Click Apply and the Confirm dialog box is displayed.
Click OK. A prompt is displayed indicating that the operation is successful.
Click Close.