There is no fundamental technical difference between LX and LH SFP modules. LX is an IEEE-defined standard, while LH is a vendor-specific naming convention that usually refers to the same optical characteristics. Understanding this distinction helps avoid incorrect assumptions during procurement. This post will focus on several standards for transmission over fiber optic media, especially for SFP modules, including the most commonly 1000BASE-X terms. The details are as follows: Table of Contents What is 1000BASE-SX? What is 1000BASE-LX? What is 1000BASE-LH? What is 1000BASE-EX? What is. Long Haul ( LH ) denotes longer distances while Long Wavelength ( LX ) denotes less energy which is obviously shorter distance.