TP-Link SM321A 1000Base-BX WDM Bi-Directional SFP module 1.25 Gbps 9/125 µm single-mode fiber LC up to 20 km Black/metallic

TP-Link SM321A is a gigabit-class bidirectional WDM SFP optical transceiver module designed for single-mode fiber links without increasing fiber count by using Wavelength Division Multiplexing (WDM) technology. It delivers data rates up to 1.25 Gbps and is suitable for network expansion between routers, switches, and media converters in business environments.

Key Advantages

• 1000Base-BX WDM technology — bidirectional data transmission over a single fiber, reducing cabling costs.

• Up to 1.25 Gbps transmission speed — provides gigabit performance for network links.

• LC (UPC) optical connector — a widely recognized standard in network infrastructures.

• Plug-and-Play design — easy installation in an SFP slot without additional configuration.

• Digital Diagnostic Monitoring (DDM) support — real-time module diagnostics and monitoring.

• Hot-swappable — can be replaced without network downtime.

• SFP-MSA compatibility — compliant with SFP-MSA standards for compatibility with equipment from various vendors.

• Compact metal housing — durable design with EMI suppression.

• Energy-efficient — low 3.3 V power consumption for standard SFP ports.

Technical Specifications

• Type — optical SFP transceiver.

• Model — SM321A.

• Standard — IEEE 802.3z 1000Base-BX.

• Max data rate — 1.25 Gbps.

• Fiber — 9/125 µm single-mode SMF.

• Connector type — LC (UPC).

• Wavelength — TX 1550 nm / RX 1310 nm (WDM).

• Max transmission distance — up to 10 km (depending on fiber and environment).

• Power — 3.3 V (from SFP port).

• Compliance standard — SFP-MSA.

• DDM support — yes.

• Hot-swappable — yes.

• Operating temperature range — 0 °C – 70 °C.

• Storage temperature — -40 °C – 85 °C.

• Certification — FCC, CE.

• Dimensions — 55.4 × 14.6 × 12.9 mm.

• Color — metallic.

Compatibility

• Compatible with — network switches, routers, servers, and media converters with 1000Base-BX SFP slots.

• Pairing required — with the corresponding TL-SM321B module at the far end to provide a bidirectional optical link.

• Not compatible with — traditional 1000Base-LX or 1000Base-SX SFP modules without BX specification; matched module pairs and proper configuration are required.

How to Use

• Install the SM321A into an SFP slot on a network switch, router, or media converter.

• Connect a single-mode fiber cable with LC connectors.

• Use the matching TL-SM321B or the paired passive modem SFP module at the opposite end.

• Verify correct wavelengths on both ends (TX/RX orientation).

• The module operates in plug-and-play mode and automatically establishes the link.

Why Choose This Product
TP-Link SM321A provides professional optical transmission with high speed and low latency while using a single fiber for both directions, reducing cabling and installation complexity. DDM diagnostics, a hot-swappable design, and broad compatibility with standard SFP equipment make it a practical and reliable solution for modern network infrastructure.

Real Use Scenarios

• Network links between two switches in fiber infrastructure up to 10 km.

• Expanding connections between office buildings or server rooms.

• Gigabit WAN links between remote network nodes.

• Connections with media converters or copper/fiber switches.

• Linking optical networks in data centers or campus networks.

Package Contents

• TP-Link SM321A SFP module (1 pc.).

• Installation guide.

About the Brand
TP-Link is a global networking technology manufacturer offering reliable, industry-standard optical and wired network modules with key features such as WDM, DDM, and SFP-MSA compatibility to support business and enterprise networking solutions worldwide.