If there are a number of paths in which the light ray may travel, the fiber is classified as multimode fiber. Signals do not travel faster in fiber than copper but the density or data capacity of fiber is much greater. Light has higher frequencies and hence shorter wavelengths so that more bits of information can be contained in a length of fiber versus the same length of copper. Fiber has low loss properties and is immune to noise. Two photons can occupy the same space and that is why two flashlight beams, when crossed, simply pass through each other unaffected.
Fiber cables are substantially lighter in weight and occupy much less volume than copper cables.
Since light does not radiate from a fiber-optic cable, it is nearly impossible to secretly tap into it without detection. Interfacing costs for fiber-optic cable are higher since electronic facilities must be converted to optics and vice versa requiring expensive transmitters, receivers, couplers, and connectors. If the fiber-optic cable breaks, splicing can be a costly and tedious task. Fiber also suffers from dispersion and absorption problems. Dispersion causes pulses of light to spread out as they travel through fiber and interfere with pulses of light ahead and behind.