In fiber optic technology, single mode fiber (SM) or monomode fiber is an optical fiber designed to propagate a single rail or one mode of light as a carrier. Generally, single mode cable has a narrow core diameter of 8 to 10 um (micrometers), capable of traveling at wavelengths of 810 nm and 1550 nm. The small single-mode fiber core size and single-light impulse virtually eliminate any distortion that may result from overlapping light pulses. Therefore, single mode fiber optic cable provides the least signal attenuation and the highest transmission speeds of any fiber cable type. For these reasons, single mode optical fiber is the best choice for long-distance data transmission.