Generally fibers for side illumination are illuminated from both ends. Rayleigh scattering causes some color shift along the length of the fiber. The illuminator has some effect on the nature of the color shifting. Tungsten Halogen will produce very little blue light so the fibers will appear slightly greenish. Metal Halide produces a much more even distribution of light and the same fiber will appear whiter in color.
Longer lengths are possible with an illuminator with an illuminator at both ends.
As bundles of smaller fibers in a transparent plastic tube. There are arguments in favor of both ways. Fibers are usually made of Polymer and are pliable and easy to shape and install. They will become stiffer in time and show an improvement in the optical properties after a period of several days of continuous illumination. We will find these decorative fibers in many of our new buildings, casinos, swimming pools etc.