In general, SR modules are optimized for shorter distances and are most often associated with 850nm operation over multimode fiber (MMF). In a corner of the data center server room, rows of optical modules are working silently. Among the most common are SR LR, two terms that show up everywhere — from switch ports in data centers to uplinks between buildings. If you've ever. Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. SR. A lot of N-Trons I'm familiar with require a min operating distance of 2 km but wondering if there are others out there that support short runs? Typically any optic (sfp) that is rated for 10km will work for short distance. 0-10km, 10-20km, 20-30 and so on.