TP-LINK´s TL-SM321B-2 and TL-SM321A-2 is designed to work in a pair to create an on-site gigabit fiber communication up to 2km (2,000 meters). With one single-mode fiber, the pair of modules can create a full-duplex gigabit path between your switches, storage devices, and server. The SM311 series Fiber Module Cards are introduced for extending transfer distance. Attached to our managed/smart switches, they can extend the distance to several kilometers even tens of kilometers which can basically satisfy the distance requirement of LAN. The 1G optical module is already a very mature series of products, which are favored by the majority of users since its advantages of low power consumption, small size, long transmission distance, and low price. It has minimum guaranteed optical budget of 12 dB, with in most cases is enough to reach about 10 km distance. However, distance is just indicative.
[PDF Version]