The TP-Link TL-SM321B-2 is a 1000Base-BX WDM Bi-Directional SFP Module designed for short and medium distance fiber networks. It supports up to 2 km transmission distance over 9/125 μm SMF (Single-Mode Fiber) using a single strand of fiber with different wavelengths in each direction. This module is compliant with the Small Form Pluggable Multi-Source Agreement (SFP-MSA) and features Digital Diagnostic Monitoring (DDM) for real-time monitoring of transceiver parameters such as current, transmit/receive optical power, and operating temperature. It is compatible with SFF-8472 and supports hot-swappable installation, providing a fast and stable gigabit fiber connection.