The Nyquist Theorem Is One Of The Deciding Factor In Data Communication. The Fibre Optics As Well As The Copper Wires Are Communication Mediums. Do You Think The Theorem Is Valid For The Fiber Optics Or For The Copper Wires?

The Nyquist theorem is not applicable to copper wire.  Because it is applicable to noiseless channel. The bandwidth of a copper wire depends on the cable quality, length, and signal to noise ratio of data transmitted. As we see copper bandwidth is directly depends upon the signal to noise ration  which concept is given by Shannon’s  in case of noisy channels.
Also it is not applicable to fibre optic cable: In fiber optic cable we transmit the pulse of light and the light is produced  due to the motion of molecules throughout the system that creates much noise. To calculate the noise created per signal we uses the concept of signal to noise ratio that is given by shanon;s not by nyquiest.