In optical fiber technology, single mode fiber (SMF) or monomode fiber, is an optical fiber that is designed for the transmission of a single ray or mode of light as a carrier to propagate at a time. Generally, single mode cable has a narrow core diameter of 8 to 10µm (micrometers), which can propagate at the wavelength of 1310nm and 1550nm. In a single-mode fiber, all signals travel straight down the middle without bouncing off the edges (blue line in the following diagram), eliminating any distortion that could result from overlapping light pulses. Signals such as Cable TV, Internet, and telephone are generally carried by single mode fibers, which are wrapped together into a huge bundle. The single mode optical fiber is the best choice for transmitting data over long distances such as 100 km (60 miles) for its low signal attenuation caused by the single light mode.