Yes, you can often use your existing router with fiber optic internet, but there are crucial considerations. Understanding compatibility, potential limitations, and when an upgrade is necessary will ensure you get the most out of your high-speed connection. Why Use Fiber Optic Internet? Before diving into the setup, let's quickly. To set up your router for fiber internet quickly, connect the router to your fiber modem, access the router's settings via a web browser, and input the provided ISP credentials. Make sure to update the firmware, configure Wi-Fi security, and customize your network name for optimal performance. With. Configure the modem for transparent bridge or modem only mode.