Move 400 Gigabit Ethernet traffic across up to 2 km of single-mode fiber with an FR4 QSFP-DD optical transceiver. The duplex LC optical interface reduces the fiber count at the host-facing link to a two-fiber connection, while FR4 wavelength multiplexing carries the high-speed Ethernet signal across the specified 1,271–1,331 nm optical range. Install the Axiom Memory AXG102011 in equipment with a QSFP-DD transceiver cage when the link calls for 400 GbE over duplex single-mode fiber rather than a parallel-fiber interface. Its 2 km reach fits interconnects between aggregation, spine, storage, or compute equipment in a building or campus environment where the optical path remains within that distance. The LC connection supports conventional duplex single-mode patching and cross-connect infrastructure. The defining combination is 400G FR4 optics, a QSFP-DD host form factor, duplex LC connectivity, and 2 km single-mode reach. This combination matters where port density and available duplex fiber determine the optical design. Confirm that the host port supports 400 GbE QSFP-DD FR4 optics, verify compatible optics at the far end, and keep the total optical path within the 2 km link limit. Clean and inspect LC end faces before installation to protect the optical connection.