SFP-module, TP-Link TL-SM321B, 1000Base-BX WDM, 1250 Mbit/s

The TP-LINK TL-SM321B is a WDM Bi-Directional SFP module designed for Gigabit Ethernet links over a single optical fiber. It uses different wavelengths for transmit and receive (TX 1310 nm / RX 1550 nm) and complies with the 1000Base-BX standard, enabling fiber connections up to 10 km when paired with compatible TP‑LINK equipment such as routers, switches and media converters.

Advantages

The module reduces fiber deployment costs by using a single strand for bidirectional traffic and supports plug-and-play installation. It operates with an internal +3.3 V power supply and can be paired with the complementary TL‑SM321A for full duplex links. Compatibility with a range of TP‑LINK devices simplifies integration into existing networks.

Key specifications

• Standard: 1000Base-BX
• Type: WDM Bi-Directional SFP module
• Tx wavelength: 1310 nm
• Rx wavelength: 1550 nm
• Maximum distance: up to 10 km
• Power supply: internal +3.3 V
• Pairing: use with TL‑SM321A
• Compatible devices: TP‑LINK routers, switches and media converters (examples: MC220L, TL-R4199G/4299G, TL-SG3109, TL-SL3428/3452, TL-SG2109WEB/2216WEB/2224WEB, TL-SL2210WEB/2218WEB/2428WEB/2452WEB, TL-SL1351 and equivalent)

How to use

Insert the TL-SM321B into an SFP slot of a compatible TP‑LINK device and connect a single-mode fiber cable. Use the TL‑SM321A at the remote end to complete the WDM bi-directional link. No additional configuration is required for basic operation; the module follows plug-and-play behavior, but verify device firmware and port settings for optimal performance.

Recommendations

For reliable links, use single-mode fiber rated for the target distance, clean connectors before mating, and pair TL‑SM321B with TL‑SM321A. Check compatibility lists and firmware versions on TP‑LINK devices when integrating into managed networks.