At least in the Zurich city network and with AON, no support is necessary.
Use the (supplied) PON module for this.
Wait a few minutes after plugging it in, then make the setting in the menu at
http://fritz.box/ (if not automatically):
Internet > Access data > [Internet access] > Provider: iWay Fiber; Access type: iWay Fiber.
Pay attention to this:
Internet > Access data > [Provider services]: [x] Allow automatic setup by the Internet provider.