TP-Link NET SWITCH MODULE SFP 1000B-BX/TL-SM321A

TP-LINK ́s TL-SM321A adopts the latest standard 1000Base-BX, transmission over a single strand of fiber, with one different wavelength going in each direction. You can extend the network distance up to 10Km with TP-LINK ́s Routers, Switches, Media Converters to provide high speed and stability.
— WDM Bi-Directional SFP Module
— Supports WDM Bi-Directional technology, using a single strand of fiber, cost saving