The speed of fibre optic cabling has more to do with signal integrity and bandwidth than any difference in propagation delay. In fact, in some cases a signal can travel faster on a copper wire (0.8c) than it can through an optical fibre (0.6c).

I am sorry if my experimental setup was not clear.

Copper is clearly a different medium than fiber optic.

That is why I stipulated a single medium for the experiment.