Extend 400 Gigabit Ethernet links over duplex single-mode fiber with a 400GBASE-LR4 QSFP112 optical transceiver built for compatible Arista Networks ports. LR4 optics combine four optical lanes onto a duplex fiber pair, allowing a single pluggable module to carry a 400G Ethernet connection beyond the short-reach distances associated with multimode links and direct-attach cabling. The QSFP112-400GB-LR4-AR-AO supports reaches up to 10 km, making it appropriate for inter-building links, campus backbones, and longer data center connections. The QSFP112 form factor installs directly into a compatible high-speed switch or router port. Its 400GBASE-LR4 interface uses single-mode fiber and duplex optical connectivity, so the installed fiber plant, connector type, and port requirements should align with LR4 operation. This module addresses deployments where a 400G uplink must traverse structured fiber rather than remain inside the same rack or row. TAA compliance distinguishes this optic for environments with Trade Agreements Act sourcing requirements. Arista Networks compatibility further targets it to Arista port environments that require a coded third-party optical module. Select it when the link calls for 400GBASE-LR4, QSFP112 host connectivity, single-mode fiber, and long-reach optical transport rather than short-reach parallel-fiber connectivity.