What are slide emitting fibers?

No, there are not any side-emitting fibers. All fiber optics acquires the light at one end and transport this to the other. While light enters a fiber and travels by the core this encounters multitude of obstacles: microscopic fissures and cracks, impurities and other components that obstruct the passage of some light and that, in turn, escapes by the outer cladding.

All fibers lose several lights though the cladding since there is no perfect systems. It unavoidable effect is used to produce elements known as "side emitting fibers" that, in fact are normal fiber optics along with a clear protective external cladding that permit to view the escaping light. Actually, some manufacturers induce stresses on the fibers, using torsion or bending to bruise the fibers and cause more light to prevent along the way. Various glass fibers are made side emitting, through the expedient method of cladding a bunch in a clear tube and breaking them at intervals. Evidently there comes a point along the tube while there are no more unbroken fibers to carry on the process.