1) Log in to the LMT and then choose Alarm Maintenance > Browse Alarm. Then, view the Subrack No., Slot No., and Port No. in the alarm location information.
2) Select the BSC on the Management Tree tab page.
3) On the BSC Device Panel tab page, right-click the corresponding interface board and then choose Interface Board Port Loopback from the shortcut menu.
4) In the displayed dialog box, specify Subrack No., Slot No., and Loopback Object in the Port Location area, and set Loopback Mode to Regenerator Section System Side Loopback and specify Loopback Time in the Maintenance Operation area. Then, click Start to perform the local loopback on the optical port of the BSC interface board.