(C) Optical fiber
Fiber optics, or optical fiber, refers to the technology that transmits information as light pulses along a glass or plastic fiber.
A fiber optic cable can contain a varying number of glass fibers, from a few up to a couple hundred. Another glass layer called cladding surrounds the glass fiber core. The buffer tube layer protects the cladding, and a jacket layer acts as the final protective layer for the individual strand.
Fiber optic cables are commonly used because of their advantages over copper cables. Some of those benefits include higher bandwidth and transmit speeds.