inglemode fiber is an optical fiber that is constructed to carry only a single ray of light. The light travels only with one wavelength trought the core and therefore singlemode prevent light rays overlapping. As a result destroying of data is not given, but can be appear at multimode fiber. With singlemode you can reach longer distances in opposite to multimode fiber. The distance of singlemode can be 50 times higher as multimode fiber. Another advantage is in some cases the higher bandwidth of singlemode fiber. Single-mode fibers are used in long-distance cables, but they require connectors with better precision and expensive devices. On this kind of fiber the light has only one way of travelling inside the fiber core. The core diameter is between 7 and 10 microns and its cladding diameter is around 125 microns, so both multi-mode and mono-mode cables have the same diameter, what makes the difference is the diameter of the core. There are three types of single-mode fibers: non dispersion-shifted fiber (NDSF), dispersion-shifted fiber (DSF) and non zero-dispersion-shifted fibers (NZ-DSF).