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 me

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/speed-of-light-in-copper-vs-fiber-why-is-fiber-better 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.