A media converter is a compact device that converts copper Ethernet (RJ45) to fiber optic (SFP/SC/LC). Plug your Ethernet cable into the RJ45 port. To connect your fiber optic cable to a router, ensure you have the following: Fiber optic modem (ONT): Most fiber connections require an Optical Network Terminal (ONT), provided by your ISP. Compatible router: Verify that your router supports fiber optic input (look for an SFP or WAN port labeled. This video will tell you how to make the RJ45 port on the router to use wi. more Fiber optic link has many advantages, such as fast speed, people tend to choose it to connect some IP devices to the router by using fiber optic cable. However, modern networks often combine both technologies.