[kazinator]

They looked at the medium itself, not the attached data link hardware.

Look at the graphs. The fiber has a higher slope; each meter adds more latency than a meter of copper.

This is simply due to the speed of electromagnetic wave propgation in the different media.

https://networkengineering.stackexchange.com/questions/16438...

Both the propagation of light in fiber and signal propagation in copper are much slower than the speed of lightin vaccuum, but they are not equal.

[jauntywundrkind]

There's also hollow core fiber, which is pretty close to speed of light in a vacuum. 2.0e8 m/s for fiber, 2.3e8 m/s for copper, pretty close to the full 3e8 m/s for hollow core.

No glass, just some reflective coating on the inside of a waveguide (hollow tube).

https://azure.microsoft.com/en-us/blog/how-hollow-core-fiber...