Optic fiber is widely used in communication. It consists of a core and cladding. Core refractive index is always greater than cladding refractive index. Some of the main types of optic fibers are Erbium doped fiber, termination fiber, photonic crystal fiber, photosensitive fiber, bend-insensitive fiber, high-index fiber and polarization-preserving fiber. In photosensitive fibers, refractive index is subjected to a change on an exposure to ultraviolet light. By doping proper amount of germanium and boron ions, sensitivity can be increased which finds immediate application in Bragg grating. Bragg grating is a periodic variation of the refractive index along the fiber axis. This is used in pump lasers, optical filters etc. Bend-insensitive fibers are fabricated by increasing the numerical aperture. This reduces bending loss.