According to the manufacturer: "The new top model is suitable for common fibre optic connections: two SFP modules are included for the GPON and AON standards, as well as for use with a fibre optic modem (ONT) via the 2.5 Gbit/s WAN port. Alternatively, the FRITZ!Box 5690 Pro can be used on all DSL connections including supervectoring for speeds of up to 300 MBit/s." G.Fast is not explicitly mentioned in the manufacturer's documentation, but the speed over copper is achieved.