The Nyquist theorem defines the maximum bit rate of a noiseless channel.

in automatic control the nyquist theorem is used to determine if a system is stable or not. there is also something called the simplified nyguist theorem that says if the curve cuts the "x-axies" to the right of point (-1,0) then the system is stable, otherwise its not.

I cannot see where the Nyquist theorem relates to cables, fiber or not.
The theorem I know, the Nyquist-Shannon sampling theorem, talks about the limitations in sampling a continuous (analog) signal at discrete intervals to turn it into digital form.

An optical fiber or other cable merely transport bits, there is no analog/digital conversion and no sampling taking place.

The Nyquist theorem is a property of mathematics and has nothing to do with technology. It says that if you have a function whose Fourier spectrum does not contain any sines or cosines above f, then by sampling the function at a frequency of 2fyou capture all the information there is. Thus, the Nyquist theorem is true for all media.

The Nyquist theorem is a property of mathematics and has nothing to do with technology. It says that if you have a function whose Fourier spectrum does not contain any sines or cosines above f, then by sampling the function at a frequency of 2f you capture all the information there is. Thus, the Nyquist theorem is true for all media.