In reference to assets.avm.de/files/docs/fritzbox/fritzbox-7530/fritzbox-7530_man_e...:

Connecting to the Internet Access: Fiber Optic Modem
Overview
You can connect your FRITZ!Box to a fiber optic modem (FTTH-ONT).
Requirements
• A fiber optic modem that is connected to your fiber optic connec-
tion
• A network cable (for instance, from the FRITZ!Box package)
Example Configuration
FRITZ!Box Internet
Instructions: Connecting to a Fiber Optic Modem
1. Insert one end of the network cable into the “LAN 1” port on the
FRITZ!Box.
2. Insert the other end of the network cable into the LAN (Ethernet)
port on the fiber optic modem.