1000Base-BX WDM Bi-Directional SFP Module Adopts the latest standard 1000Base-BX Up to 2 km transmission distance in 9/125 μm SMF (Single-Mode Fiber) Compatible with Small Form Pluggable Multi-Source Agreement (SFP-MSA) Supports Digital Diagnostic Monitoring (DDM) Supports Hot Swappable What This Product Does TP-LINK´s TL-SM321A-2 is developed in accordance with the Small Form Pluggable Multi-Source Agreement (SFP-MSA). As a WDM Bi-Directional optical transceiver TL-SM321A-2 uses an integrated LC Bi-Directional optical interface connector and the data link is up to 2 km in 9/125 μm SMF (Single-Mode Fiber).   Also TL-SM321A-2 incorporates the Digital Diagnostic Monitoring (DDM) feature which is compatible with SFF-8472. DDM supports real-time monitoring of the transceiver and shows parameters including the transceiver current which transmits/receives optical power and operating temperature.   TP-Link's TL-SM321A-2 is used for short-and medium distance fiber network in practice and it provides fast and stable gigabit fiber connection for switches routers servers etc.