How to connect two routers in series for fiber optic cable usage

You can connect two routers in series using fiber optics by linking their SFP ports with compatible fiber cables and configuring one as the primary router and the other as a secondary router with proper IP addressing.Hardware RequirementsSFP Modules: Ensure both routers have compatible SFP (Small Form-factor Pluggable) modules. For single-mode fiber, use single-mode SFPs; for multi-mode fiber, use multi-mode SFPs .Fiber Optic Cable: Use a pre-manufactured fiber patch cable with the correct connectors (e.g., LC-LC, UPC-UPC) and duplex configuration for full-duplex communication .Router Ports: Both routers must have SFP or fiber-capable ports. If not, you may need media converters to bridge fiber to Ethernet.Physical ConnectionInsert the SFP modules into the SFP ports of both routers.Connect the fiber optic cable between the two SFP modules. Ensure the transmit (TX) and receive (RX) strands are correctly aligned for duplex communication .Power on both routers and verify the link lights on the SFP ports indicate a successful connection.Network ConfigurationPrimary Router (Internet Gateway): Connect this router to your ISP or ONT (Optical Network Terminal) via its WAN port .Secondary Router: Connect its SFP port to the primary router's SFP port. Assign a static IP address in a different subnet for the point-to-point link (e.g., 192.168.3.1 for the primary and 192.168.3.2 for the secondary router), .Routing: Set the default gateway on the secondary router to the primary router's point-to-point IP. This ensures all traffic from the secondary router routes through the primary router to the internet .LAN Configuration: Assign a unique LAN subnet to the secondary router (e.g., 192.168.2.0/24) to avoid IP conflicts with the primary router .Optional Access Point Mode: If the secondary router supports “Access Point” mode, enable it to simplify configuration and extend Wi-Fi coverage without double NAT issues .Testing and OptimizationVerify connectivity by pinging the primary router from the secondary router.Test internet access from devices connected to the secondary router.Adjust Wi-Fi channels and router placement to minimize interference and maximize coverage .For advanced setups, configure firewall rules and NAT on the primary router to manage traffic from the secondary router . By following these steps, you can successfully connect two routers in series using a fiber optic cable, ensuring high-speed, reliable communication between them while maintaining proper network segmentation and internet access.