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.

They include: Simple random sampling, Systematic sampling, Stratified sampling, Quota sampling, and Cluster sampling.

Answer is Quota sampling.

Its one of the method of non-probability sampling.

Sampling techniques in researching involves to types of sampling. The probability sampling and the non-probability sampling. Simple random is an example of probability sampling.

You are correct; convenience sampling is not random sampling.