hello, I tell you that it is because the LINE-PROFILE that you configure for each service, you can separate the broadcast domain to which it belongs by tying a GEM-PORT to a specific vlan-id. In fact, in a single ONT you can deliver, for example, 3 vlans that belong to different services (it could be one for the Internet, one for voice and another for management). I am sending you an example of configuring a LINE-PROFILE from U2000 to show it graphically:


This is the same ONT with 2 T-CONTS and 2 GEM-PORTS, and each one is tied to a different vlan, one is for data and the other is for management, and you transport it to the OLT and in the OLT you separate the vlans in the Trunk that you have towards your Uplink transport network. It is in this separation of vlans that the OLT differentiates which traffic belongs to which vlan, and each ONT "invokes" that vlan that it is going to use through the use of the LINE-PROFILE.