SFP Fiber Transceiver TP-LINK ISM321B-20, WDM Bi-Directional, 20 km, 1.25Gb, LC (UPC), SMF

TP-LINK ISM321B-20 is a hot-pluggable SFP fiber transceiver designed for single-mode (SMF) Ethernet links. It supports bi-directional WDM transmission at 1.25 Gb/s (IEEE 802.3z) over a maximum distance of 20 km using a LC (UPC) connector and 9/125 µm fiber. The module runs from a 3.3 V supply and operates across a wide temperature range, packaged in a compact SFP form factor (56.4 × 13.4 × 11 mm).

Advantages

The transceiver is hot-swappable for easy maintenance and replacement without powering down network equipment. Its single-mode fiber design with LC (UPC) connector and WDM bi-directional capability reduces cabling complexity while supporting long-distance links up to 20 km. The module’s compact SFP dimensions and broad operating temperature range make it suitable for varied installation environments.

Suitable for

• Extending Ethernet links between switches and routers in campus networks
• Long-distance fiber connections for ISPs and service providers
• Enterprise backbone and data center uplinks

Key specifications

• Form factor: SFP (small form-factor pluggable)
• Data rate: 1.25 Gb/s (1250 Mbit/s, IEEE 802.3z)
• Transmission type: WDM bi-directional
• Maximum reach: 20 km
• Fiber type: Single-mode fiber (9/125 µm)
• Connector: LC (UPC)
• Interface: Fiber optic SFP
• Operating voltage: 3.3 V
• Operating temperature range: -40 to 85 °C
• Relative humidity (operating/storage): 5–85%
• Dimensions (W×D×H): 56.4 × 13.4 × 11 mm

How to use

Insert the TP-LINK ISM321B-20 SFP transceiver into an SFP slot on a compatible switch, router or transceiver cage while the device is powered on if hot-plugging is supported. Connect single-mode LC fiber cables (9/125 µm) to the LC (UPC) connector, ensuring correct polarity for bi-directional WDM links. Verify link status through the host device’s interface and monitor for optical levels and alarms per network management tools.

Recommendations

For reliable operation, use quality single-mode fiber (9/125 µm) with LC (UPC) connectors and adhere to proper cleaning procedures before connection. Match transceiver wavelength and WDM pair correctly at both ends and observe manufacturer guidelines for ESD protection during handling and installation.