Single-Mode Fibre Optic Cable.
Single-Mode Fibre Optic Cable
Multimode fibre cable has multiple modes of propogation - that is, several wavelengths of light are normally used in the fibre core. In contrast, single-mode fibre cable has only one mode of propagation, a single wavelength of light in the fibre core. This means there's no interference or overlap between the different wavelengths or light to garble your data over long distances as can happen with multimode cable.
50 times more distance
What does this get you? Up to 50 times more distance than multimode fibre cable. You can also get higher bandwidth. You can use a pair of single-mode fibre strands full-duplex for up to twice the throughput of multimode fibre cable.
The actual speed and distance you get with single-mode fibre will vary according to the manufacturer of the LAN devices or fibre modems used with the cable.