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Router with 100m fiber optic cable only has 50m speed

A fiber optic connection rated for 100 meters may only reach 50 Mbps due to router port limitations, cable quality, or network adapter settings.Common Causes

1. Router Port Limitations: Many routers, even if marketed for high-speed fiber, may have WAN or LAN ports limited to 10/100 Mbps. If your router only supports 100 Mbps, your connection cannot exceed this speed regardless of the fiber capability . 2. Ethernet Cable Quality: Using older or damaged cables (Cat5 instead of Cat5e/Cat6) can restrict speeds. Even with fiber, the connection from the router to your device must support gigabit speeds. Cat5e or Cat6 cables are recommended for 1 Gbps performance . 3. Network Adapter Settings: Computers may default to 100 Mbps due to auto-negotiation issues. Check your network adapter settings in Device Manager, ensure "Speed & Duplex" is set to 1 Gbps Full Duplex, and disable any power-saving options that may throttle speed . 4. Intermediate Devices: Switches or wall jacks between the fiber modem and your device can limit speed if they are not gigabit-capable. Direct connections to the router or modem are preferred for testing . 5. Firmware or Driver Issues: Outdated router firmware or network adapter drivers can cause speed drops. Updating both can resolve negotiation problems and restore full speed .

Troubleshooting Steps
  1. Verify Router Specifications: Ensure your router has gigabit WAN/LAN ports. If not, upgrade to a gigabit router .
  2. Check Cables: Replace any Cat5 cables with Cat5e or Cat6 and ensure they are not damaged .
  3. Direct Connection Test: Connect your computer directly to the fiber modem to confirm the maximum speed is achievable.
  4. Adjust Network Adapter Settings: Set speed to 1 Gbps Full Duplex and disable power-saving features .
  5. Update Firmware and Drivers: Ensure the router firmware and network adapter drivers are the latest versions .
  6. Test with Another Device: Sometimes the issue is device-specific; testing with another computer can help isolate the problem . By systematically checking these factors, you can identify why your 100m fiber optic connection is only achieving 50 Mbps and restore it to its full potential.
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