Hello, friend!
The OLT can change the WLAN password on the U2000.

If you want to send XML files to the ONT, you can configure a VAS profile on the U2000 and deliver the VAS profile to the ONT. The VAS profile is in the XML format.
How do you apply for a VAS profile to modify ONT configurations on the U2000?
1. On the U2000, choose Configuration > Access Profile Management (traditional style) from the main menu or choose Application Center from the Main Menu. Double-click Fixed Network NE Configuration and choose Access Service > Access Profile Management (application style).
2. In the NE Explorer, choose PON Profile > ONT VAS Profile from the navigation tree.
3. Click the General ONT VAS Profile tab.
4. In the ONU list, right-click a profile and choose Modify from the shortcut menu. In the dialog box that is displayed, modify the profile name. Modify related parameters.
5. On the Terminal Reference tab page in the lower pane, right-click an ONU and choose Force Down from the shortcut menu. Configure the value-added service.
Thanks!