1000BaseLX or 1000Base-LX
From Network Dictionary Wiki
1000BaseLX, also known as 1000Base-LX, is a physical layer specification for Gigabit Ethernet over fiber optic cabling as defined in IEEE 802.3z. LX stands for long wavelength, and 1000Base-LX uses long wavelength laser (1310nm) over multimode and single-mode fiber as opposed to 1000Base-SX, which uses short wavelength laser over multimode fiber. The maximum distance of fiber is 550m for multi mode and 5km for single mode.
1000BASE-LX is a fiber optic Gigabit Ethernet standard, using a long wavelength laser (See IEEE 802.3 Clause 38). Signaling speed 1.25±100 ppm GBd, wavelength 1270 to 1355 nm, RMS spectral width (max) 4 nm. Typically, GbE lasers will be specified as having a 1300 or 1310 nm wavelength.
1000BASE-LX is specified to work over a distance of up to 2 km over 9 µm single-mode fiber. In practice it will often operate correctly over a much greater distance. Many manufacturers will guarantee operation up to 10 or 20 km, provided that their equipment is used at both ends of the link. 1000BASE-LX can also run over multi-mode fiber with a maximum segment length of 550 m. For any link distance greater than 300 m, the use of a special launch conditioning patchcord may be required. This launches the laser at a precise offset from the center of the fiber which causes it to spread across the diameter of the fiber core. This reduces the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in multi-mode fiber.