Hi!
Maybe because of the effect ONTs number is 0, you can check if the OLT is in a type B scenario or not.
When the GPON type B successfully protects the switching, the ONT stays in the 'O4' state and goes online immediately after switching to another port.
However, the ONT does not go offline. Therefore, the LOS alarm parameter is displayed as '-' in the GPON type B switching scenario.