Fiber increases security but is more expensive than copper or wireless.
Explanation:
Fiber optic cables convert your data into light and send it as a laser through a reflective tube. You have to have a node on each side that is able to covert the light to and from data.
With copper or wireless on the other hand, your traffic can be intercepted much more easily as someone could just do a "man in the middle" attack. With copper it would be the physical installation of a switch or something along the line, and with wireless it would be a wireless interceptor (IMSI catcher).
