Final answer:
The coupling of light energy into an optical fiber's core is contingent on the fiber's core size and its numerical aperture (NA), which are key to minimizing signal loss and ensuring flexibility and durability through cladding and total internal reflection.
Step-by-step explanation:
The amount of light energy coupled into the core of an optical fiber depends on the core size and numerical aperture (NA) of the optical fiber. Fibers in bundles are surrounded by a cladding material that has a lower index of refraction than the core. This cladding is crucial for preventing light transmission between fibers in a bundle and ensures that light is propagated along the length of the fiber through the principle of total internal reflection. The core and cladding design allows the fibers to be both flexible and durable, with the additional benefit of minimizing signal loss and maintaining high-quality image transmission.