Optical fibers are glass materials which induce the transmission of light, its information transmission media. There are Single-mode and multiple mode optical fibers, according to size. Optical fibers are cylinder-shape dielectric waveguides that consist of a core, cladding and acryl coating. Light is totally reflected due to the difference of refractive index at the core and clad layer, and is transmitted through the core layer. It is classified as single-mode or multi-mode, according to the number of radio wave modes at the core. Single-mode optical fibers are suitable for long distance and large capacity data communication as there is low data loss. Single-mode optical fibers for special purposes consist of cutoff wavelength transition optical fibers and dispersion-shifted optical fibers.