QSFP-DD-400G-LR4: Frequently Asked Questions
Q: What is the difference between QSFP-DD 400G LR4 and QSFP112 400G LR4?
A: The main difference is the electrical interface. A typical QSFP-DD 400G LR4 module uses eight electrical lanes operating at approximately 50 Gbps each, while a QSFP112 400G LR4 module uses four electrical lanes operating at approximately 100 Gbps each. Both can use a four-lane optical interface, but optical interoperability depends on the modules’ wavelength specifications, optical lane mapping, and applicable standards. Check the manufacturer’s datasheets and host-device compatibility before connecting them.
Q: What is the difference between 400G LR4 and 400G LR8?
A: The primary difference is the optical lane architecture. A typical 400G LR4 transceiver uses four optical lanes operating at approximately 100 Gbps per lane, while a 400G LR8 transceiver uses eight optical lanes operating at approximately 50 Gbps per lane. Both deliver an aggregate data rate of 400 Gbps over long-reach optical links, but their optical designs, component requirements, power consumption, and costs may differ by product.
Q: What should I check before using a 400G LR4 transceiver in a switch?
A: Before deployment, verify that the switch supports the QSFP-DD form factor, 400G data rate, and the transceiver’s optical interface and specifications. Check the port’s power budget, thermal requirements, firmware compatibility, and supported transceiver list. Although some 400G LR4 modules have power consumption below 10W, actual power requirements vary by model, and the switch must support the specific module’s maximum power and cooling requirements.
Q: Can an OSFP port accommodate a QSFP-DD transceiver such as the QDD-400G-LR4?
A: No. OSFP and QSFP-DD are different transceiver form factors, so a QSFP-DD module cannot be inserted directly into an OSFP port. This applies to QSFP-DD modules such as the QDD-400G-FR4, QDD-400G-SR8, QDD-400G-LR4, and QDD-400G-DR4. To establish a compatible link, select a transceiver that matches the host port’s form factor and supports the required data rate, optical interface, and transmission distance.
Q: Can a 400G LR4 transceiver support an 8 km fiber link?
A: A 400G LR4 transceiver rated for up to 10 km may support an 8 km single-mode fiber link. However, the achievable distance depends on the total optical link budget, including fiber attenuation, connector and splice losses, and other components in the link. Before deployment, confirm that the total link loss falls within the module’s specified limits and that the remote-end transceiver is compatible.
