Choose based on testing needs or live-link deployment. For lab work, a QSFP28 loopback adapter such as the model designed for testing provides a controlled path with predictable loss, like a 3 dB insertion loss and a modest 1.5W power draw. For live links, select a 100G QSFP28 transceiver family—options include 100G-BIDI, CWDM4, and PSM4 types—that support QSFP28 ports and optic wavelengths. Also confirm the connector and fiber type align with your equipment, such as LC Duplex or MPO, and plan for distances up to about 2 km over SMF.

100G-BIDI transceivers use bidirectional optics over a single fiber pair, simplifying cabling for shorter runs or testing scenarios. CWDM4 and PSM4 provide four-lane pathways, with CWDM4 using four wavelengths and PSM4 using four parallel 25Gbps channels via an MPO interface. In data-center contexts, CWDM4 and PSM4 enable higher aggregate bandwidth over single-mode fiber, while BIDI emphasizes simpler cabling. Expect distances around 2 km for many 100G SMF deployments, with PSM4 often reaching shorter to mid-range links.

Use a loopback tester when you need to validate TX/RX paths, alignment, and connector integrity without disturbing the network. It provides a controlled environment to confirm port functionality and signal integrity before connecting to real equipment. For production paths, install a live 100G QSFP28 transceiver—such as BIDI, CWDM4, or PSM4 variants—to carry actual traffic between switches or routers. The loopback helps avoid downtime, while live transceivers ensure real network performance and proper interoperability.

Ensure compatibility by matching the QSFP28 port type with the transceiver family you choose, and verify fiber infrastructure supports the selected interface. Use clean LC or MPO connectors and confirm the fiber type (SMF) aligns with the module’s design. Consider power and heat: many devices emphasize low power operation, with typical loopback and transceiver options designed for efficient data-center use. Regular inspection of connectors and a clean, stable cabling path will preserve signal integrity across 100G links.

Check the physical interface and reach requirements. A few QSFP28 options support LC Duplex or MPO connectors, and many 100G modules are designed for single-mode fiber with distances up to 2 km. If you plan longer runs, CWDM4 and PSM4 variants are common choices, while BIDI offers a simpler cabling approach for shorter distances or testing scenarios. Always verify that your switch or router supports QSFP28 100G ports and that your fiber is suitable for the chosen transceiver family.

In this range you’ll encounter loopback adapters for testing, 100G transceivers like BIDI, CWDM4, and PSM4 variants, as well as direct QSFP28 DAC cables and fiber links. Examples include loopback accessories with defined loss and power specs, 100G-BIDI products, CWDM4 and PSM4 transceivers, and copper or fiber interconnects with LC or MPO interfaces. This variety supports both testing environments and live data paths, enabling flexible, scalable 100G testing and deployment.