In fiber optic cables, light can travel in two forms that characterize the fiber itself: single-mode fiber and multimode fiber.
Single-mode fibre is like a straight shot:: the light path is small in diameter, which makes the signal path mostly straight.
It has a diameter ranging from about 8 um to 10 um depending on the manufacturer. To use this type of fiber, a very precise source must be used which can produce a single mode of light radiation into the fiber. The difference in refractive index between core and cladding of a single mode fiber is very small, and together with the small core this prevents modal dispersion. This optical fiber is capable of propagation wavelengths of 1310 nm and 1550 nm, slightly attenuates the signal. It used for long distances and high bandwidth.
