It occurred to me that your speed is set by the modem's sync profile on xDSL. But what about FTTH? I guess there is no such thing as syncing on FTTH since there is not bit-tone allocation to do on FTTH considering it's a totally different technology.
How is the speed limited to what each customer pays for then? Is it a mechanism similar to cable where the modem gets an encrypted configuration file telling it what is the provisioned speed?
There is a BRAS server in the CO that sets the speed policy that is set to each ONT upon configurarion. The tech before completion configures the ONT with a set of numerical values so the equipment in the CO can now see and speak to the ONT. Each profile on Fibe TV is set to 300 Mb/s down and then whatever upload corresponds to the product your paying for. Speed policy kicks in and takes care of regulating your speed. For fibe tv on vlan 36 you have a dedicated 56Mb/s for TV that is completely seperate.