Why do optical fibers lose so much energy?

Optical fibers have several characteristics that contribute to loss in transmission. The most common are cladding loss between the core and cladding diameters, packing fraction loss due to gaps between individual fibers in light guides and fresnel losses due to reflections off the end faces. Additional factors include extreme bends over long durations, fracture cracks due to bending, and cross-talk between individual fibers.