Fiber optics are a transparent thin fiber, usually made of glass or plastic, for transmitting light. Fiber optics is the branch of science and engineering concerned with such optical fibers. fiber optics are a cylindrical object that transmit light along their shaft. The fiber consists of a core surrounded by a cladding layer. Like other glasses, the glass used in fiber optics has a refractive index of about 1.5. For the fiber to guide the optical signal the refractive index of the core must be slightly higher than that of the cladding, though typically the difference is less than one per cent. The boundary sport ween the core and cladding may either be abrupt, in step-index fiber, or gradual, in graded-index fiber.
Fiber with large core diameter, called multi-mode fiber, may be analyzed by geometric optics. In a step-index fiber, rays of light are guided along the fiber core by total internal reflection. Rays that meet the core-cladding boundary at a high angle (measured relative to a line normal to the boundary) are completely reflected.
Fiber optics can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables. Although fibers can be made out of either transparent plastic or glass, the fibers used in long-distance telecommunications applications are always glass, because of the lower optical attenuation.