The limitation is the fiber melting. It won't melt along the whole length - there will be some bend/crack/dirt which will make a hotspot, and that hotspot wil

The limitation is the fiber melting. It won't melt along the whole length - there will be some bend/crack/dirt which will make a hotspot, and that hotspot will then absorb more laser light and get hotter, and you'll get a runaway heating. The hot bit will then propagate slowly towards the laser source, eventually destroying the whole fiber. High power fiber optic communication systems have protections in place to detect this happening and turn off to reduce the damage radius. Learn more: https://www.microcare.com/en-US/Resources/Resource-Center/FAQs/Can-High-Power-Lasers-Can-Damage-Fiber-Networks https://www.microcare.com/en-US/Resources/Resource-Center/FA...