100m fiber optic cable speed is slow after passing through a router

Slow speeds on a 100M fiber connection are often caused by router limitations, Wi-Fi interference, or hardware and configuration issues.

Check Your Router and Hardware

Your router acts as the traffic controller for your network. Older or low-quality routers may not handle fiber speeds efficiently, even if the fiber line itself supports 100 Mbps or higher. Ensure your router supports at least 100 Mbps Ethernet ports and modern Wi-Fi standards (Wi-Fi 5 or Wi-Fi 6) to avoid bottlenecks. Inspect all cables for damage, bends, or loose connections, and use Cat 5e or Cat 6 Ethernet cables for optimal performance .

Test Wired Speeds

Connect a device directly to the router using an Ethernet cable and run a speed test. If speeds are normal over a wired connection, the issue is likely with Wi-Fi performance rather than the fiber line itself .

Optimize Wi-Fi Performance

Wi-Fi speed can be affected by distance from the router, physical obstacles, and interference from other devices. Place the router in a central location, away from walls and electronic devices. Consider using dual-band or tri-band routers to reduce congestion and improve throughput .

Inspect Fiber Signal and Equipment

Even with fiber, signal attenuation or faulty transceivers can reduce speeds. Check for visible damage to fiber cables, clean connectors, and ensure transceivers are functioning properly. If possible, test the fiber signal with a power meter or OTDR to confirm it is within normal levels .

Restart and Update

Sometimes, simply rebooting the router can resolve temporary glitches. Additionally, ensure the router firmware is up to date, as firmware bugs can limit performance .

Consider Device Limitations

Older devices may have network cards that cannot handle full 100 Mbps speeds. Verify that your device's network interface card (NIC) supports the connection speed . By systematically checking these factors—router quality, Wi-Fi setup, fiber signal integrity, and device capabilities—you can identify the cause of slow speeds and restore your fiber connection to its expected performance.