Move 400 Gigabit optical traffic across coherent transport links with a QSFP-DD optic built for Arista Networks equipment. This TAA-compliant module implements 400GBASE-DCO signaling, pairing a 400G host interface with digital coherent optics for high-capacity optical transport. Its QSFP-DD package puts the coherent interface in a pluggable, high-density transceiver format rather than on a separate transport card. QDD-400GB-DCO-ZR-AR-AO fits deployments where the host platform calls for an Arista-compatible 400GBASE-DCO coherent QSFP-DD optic. Match the transceiver to a supported QSFP-DD port and to the platform's optical transport configuration before installation. The coherent interface is intended for transport applications where 400G capacity and digital coherent operation are selection requirements. Within a 400G optical portfolio, the defining characteristics are its DCO coherent operation, ZR designation, QSFP-DD form factor, Arista Networks compatibility, and TAA-compliant designation. Those attributes distinguish it from non-coherent Ethernet optics and from modules built for other host ecosystems. The module provides a specific 400G coherent option when interface type and platform compatibility must align.