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How to Choose Between 1000BASE-SX vs. 1000BASE-LX

Gigabit Ethernet, a significant advancement in the telecom industry, offers speeds of up to 1000Mbps through a standard for transmitting Ethernet frames at a gigabit per second. SFP transceivers, available in various types, are crucial for selecting the appropriate transceiver to meet optical range requirements. Among these, 1000BASE-LX and 1000BASE-SX SFP are common types on the market. This blog will show you detailed information about the difference between fiber 1000BASE-SX vs. 1000BASE-LX.


What is 1000BASE-SX SFP?


1000BASE-SX is a gigabit Ethernet standard operating over fiber optic cables at wavelengths of 850 nanometers, suitable for both single-mode and multimode fiber. It can cover distances of up to 550 meters on multimode fiber. The “SX” designation denotes its suitability for short distances, typically ranging from 220m to 550m over multimode fiber. For instance, utilizing the 6COMGIGA 850nm 1000BASE-SX SFP module (SFP-1G-SX), transmission extends up to 220 meters via Fiber Distributed Data Interface(FDDI), 275 meters via 62.5μm/125µm OM1 fibers, and up to 550 meters when deploying 50μm/125µm OM2 fibers, and now it often functions effectively over longer distances with high-quality fiber, for example, it support distances of up to 1 kilometer, utilizing laser-optimized OM3, OM4, or OM5 multimode fiber. The SFP 1G SX is now particularly popular for intra-building links, commonly deployed in large office buildings, co-location facilities, and carrier-neutral internet exchanges; the Cisco GLC-SX-MMD 1000BASE-SX SFP operates at an 850nm wavelength and is only compatible with multimode optical fiber featuring LC connectors.


What is 1000BASE-LX SFP?


IEEE 802.3 Clause 38 specifies 1000BASE-LX as a standard for implementing Gigabit Ethernet networks, with the “LX” indicating long wavelength suitable for long cable runs of fiber optic cabling (1270–1355 nm). It can operate over single-mode and multimode fiber, covering distances of up to 10km and 550m, respectively. For link distances beyond 300m, a special launch conditioning patch cord may be necessary. This version of Gigabit Ethernet is designed for connecting high-speed hubs, Ethernet switches, and routers across different wiring closets or buildings, supporting longer-length multimode building fiber backbones and single-mode campus backbones. The GLC-GE-DR-LX by Cisco, an SFP 1G LX module, operates at a wavelength of 1310nm for a distance of 10 km. Due to its low cost and extended reach, 1000BASE-LX SFP has become one of the most prevalent standards in enterprise networks.


The Difference Between 1000BASE-SX vs. 1000BASE-LX


The 1000BASE-SX and 1000BASE-LX LC SFP transceivers are compatible with the IEEE 802.3z standard, facilitating Gigabit Ethernet transmission over fiber optic cabling. These transceivers exhibit differences in various aspects; follow us to check more in the next part.


Different Optical Fiber Types: The 1000BASE-SX SFP transceiver is designed for multimode fiber, which has a thicker core and allows for higher speeds over shorter distances. Conversely, the SFP LX transceiver is compatible with single-mode and multimode fibers and facilitates data transmission and reception.


Maximum Transmission Distance: The 1000BASE-SX SFP transceivers are ideal for short distances, typically within small areas or buildings, reaching up to 1km. In contrast, the 1000BASE-LX SFP transceivers are primarily utilized for long-distance transmission, supporting up to 10km distances.


Dispersion: Dispersion characteristics vary between the two optic types. 1000BASE-SX SFP modules experience modal dispersion, where light rays follow different paths through the fiber. This results in varied arrival times at the receiving end, limiting achievable distances. Conversely, 1000BASE-LX SFP modules are affected by waveguide dispersion, which results from the light’s width being larger than the core of the fiber. While this offers better control of photon paths, it is more susceptible to microbends, twists, and stress on the fiber.


Application: The 1000BASE-SX SFP module is commonly deployed in short-range applications within local area networks (LANs), data centers, and campus networks. Conversely, the 1000BASE-LX SFP module is suitable for long-range applications, including wide area networks (WANs), metropolitan area networks (MANs), and long-haul connections between different locations.




The Gigabit Ethernet solution over fiber supports half- and full-duplex transmission at speeds of 1Gbps (1000Mbps). Designed specifically for cost-effective multimode fiber runs, the 1000BASE-SX standard is optimized for deployment in horizontal and shorter-length backbone applications. Conversely, the 1000BASE-LX standard accommodates longer-length multimode building fiber backbones and single-mode campus backbones. The 1000BASE-LX standard supports multimode lengths of 550m and single-mode lengths of 10km. Through these main differences, you can easily choose between these two different 1G network modules according to your other personal network needs.

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