Are There Any Differences Between LX, LH and LX/LH?

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We usually see LX SFP, LH SFP and LX/LH SFP on many websites, and many people show their confusion about them. Whether they are the same or different? If they are dissimilar, what differences between them on earth?

The Commonly Used 1000BASE-X Standards about Ethernet
Ethernet was the result of the research done at Xerox PARC in the early 1970s. Ethernet later evolved into a widely implemented physical and link layer protocol. Fast Ethernet increased speed from 10 to 100 megabits per second (Mbit/s). Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. The initial standard for Gigabit Ethernet was produced by the IEEE in June 1998 as IEEE 802.3z, and required optical fiber. 802.3z is commonly referred to as 1000BASE-X, which is used in industry to refer to Gigabit Ethernet transmission over fiber, where options include 1000BASE-SX, 1000BASE-LX, 1000BASE-LX10, 1000BASE-BX10 or the non-standard -EX and -ZX implementation.

Gigabit Ethernet 1000BASE-LX Optical Interface Specifications

1000base-lx/lh SFP1000BASE-LX is a fiber optic Gigabit Ethernet standard specified in IEEE 802.3 Clause 38 which uses a long wavelength laser (1,270–1,355nm). The 1000BASE-LX SFP is specified to work over a distance of up to 10 km over single mode fiber and it can also run over all common types of multimode fiber with a maximum segment length of 550 m. For link distances greater than 300 m, you must install a mode-conditioning patch cord between the transceiver and the MMF cable on both ends of the link.

1000BASE-LH and 1000BASE-LX/LH Optical Interface Specifications
LH refers to Long Haul. Many vendors use both of them for certain SFP modules, but they aren’t a Gigabit Ethernet standard at all. 1000BASE-LX/LH SFP can achieve a distance up to 20 km over single mode fiber. Unlike that, 1000BASE-LH SFP operates a distance up to 70 km over single mode fiber.

Conclusion
In a word, these three modules are all referred to Gigabit Ethernet transmission. Among them, the 1000BASE-LX is a standard, the other two just are terms widely used by vendors. Other long haul transmission standards include 1000BASE-LX10, 1000BASE-EX and 1000BASE-ZX. We can see their differences more clearly in the following chart:

Name  Medium wavelength Specified distance
1000BASE-LX/LH 9/125 Single mode fiber 1310nm  10km
1000BASE-LX 62.5/125, 50/125 Multi mode fiber 1310nm 550m
1000BASE-LX10 9/125 Single mode fiber 1310nm 10km
1000BASE-LH 9/125 Single mode fiber 1310nm 25~70km
1000BASE-EX 9/125 Single mode fiber 1310nm 40km
1000BASE-ZX 9/125 Single mode fiber 1550nm 70km

Related Article: Which Patch Cable Should I Choose for My Optical Transceiver?