Co-Packaged Optics or Pluggable Modules: What Changes in the AI Cabling Package?

Follow twelve compute connections across two named packages

Consider two fictional offers for the same twelve planned compute-side connections. Offer A names a Q3400-RA, separate switch-side optical-module items, twelve single-port remote optical modules F01 through F12, and twelve direct fiber assemblies C01 through C12. Offer B substitutes the documented Q3450-LD CPO package and deletes the entire loose-optics allowance. The twelve remote pluggable compute endpoints remain. These allocations and the direct-channel arrangement are stipulated inputs, not quantities derived from switch capacity.

The deletion combines two changes that need different treatment: switch-side conversion moves into the CPO package, while the allowance for modules at the remote endpoints has also disappeared. Following the components from the switch to those endpoints reveals what B supplies and what its material list still needs.

NVIDIA's hardware introduction, updated August 21, 2026, describes Q3400-RA as an air-cooled 4U switch with 144 ports at 800Gb/s across 72 OSFP cages. The separate Q3450-LD integrates silicon photonics with the switch ASIC and presents direct optical connections. The shared Quantum-X800 family name does not establish the same supplied optical package.

Keep the exact ordering identities attached to A and B. The HTML ordering table checked October 20, 2026 lists Q3400-RA as 920-9B36F-00RX-8S0, with lifecycle phase P-Rel, and Q3450-LD as 920-9B36M-00MX-8ES, marked Prototype. That status belongs to the cited ES row; it does not classify every possible Q3450-LD SKU or establish present availability. The offered configuration, delivery status and applicable support documents must be established for the actual purchase.

References: [N1][N2]

Move conversion into the switch; keep laser supply separate

In A's pluggable arrangement, the switch's electrical data path reaches a separate transceiver in a host cage. The fiber-facing interface belongs to that module. In B's CPO arrangement, the switch-side optical engine is integrated with the switch package, and the external data fiber reaches an optical interface presented by the system.

NVIDIA's March 27, 2025 technical blog explains the shorter high-speed electrical path created by integrating photonics with the switch IC. Its August 26, 2025 architecture article distinguishes the optical engine's laser-input fibers from its transmit and receive fibers. An external laser source, or ELS, supplies light; the integrated engine performs data modulation and optical reception. Light generation and data conversion remain different functions even when both are included in the supplied system.

This explains the switch-side change in the twelve-connection case. B can replace the separate switch data-transceiver allowance with its integrated optical package. It still needs the laser units that supply that package, and the offer should identify which are included. Deleting a loose-transceiver line does not make those components disappear.

Here, external means separate from the integrated optical engine. It does not identify an independently mounted laser shelf or an ordinary inter-rack patch cable. The March blog describes front-panel pluggable ELS modules; the offered hardware documentation must establish the actual arrangement. Internal laser-delivery fibers and engine-to-panel assemblies remain supplier-integrated system assemblies unless the exact supply and service documents assign them otherwise.

References: [B1][B2]

Assign ELS supply and service to its equipment owner

The architecture articles discuss accessible or field-replaceable laser modules. The Q3450 FRU Replacements page, updated August 21, 2026, sets a more restrictive model-specific boundary: users must not remove, replace or service the ELS themselves. It requires a genuine NVIDIA-approved replacement unit and directs replacement, repair or RMA to NVIDIA service. Physical replaceability therefore gives a general cabling crew no ELS service authority.

The page describes 18 ELS modules with eight laser emitters per module. The accessory list separately identifies ELS part 692-9IAG1-0P00IH. These describe laser-source components, not removable data transceivers or a population of external patch cords. Neither the twelve planned compute connections nor an emitter total supplies an external cable count.

For B, identify the included laser units, the party responsible for their supply, and the arrangement for supported spares and service coordination under the offered revision's applicable documents. Any unestablished support arrangement stays open in the equipment offer. This assigns the laser responsibility once, separately from the remote optical modules and the external cabling work.

References: [B1][B2][N4][N5]

Twelve remote pluggable endpoints still need optics

F01 through F12 are modules at the remote compute endpoints. They are not the switch-side optical engines now included in B. Moving conversion into the CPO switch does not perform the conversion at the far end of each fiber connection. B still needs twelve remote module allocations unless the endpoint design itself changes.

The manual's August 21, 2026 topology table distinguishes two remote roles. It assigns 980-9IAH3-00XM00 to another pluggable XDR switch and 980-9IAT3-00XM00 to a pluggable XDR HCA on the compute side. The accessory list describes the former as a 1600Gbps twin-port OSFP, 2xDR4, 2xMPO APC, IHS transceiver, and the latter as an 800Gbps single-port OSFP DR4, MPO APC, RHS transceiver. Both are described as CPO interoperable. The twin-port remote-switch item and the single-port compute-side item have different roles in this documentation.

Those identities explain the type of item missing from B; they do not establish that A's F01-F12 parts can be reused or that either listed part is approved for an unspecified endpoint. The exact remote equipment, module and supported channel remain the equipment/design owner's selection.

The accessory list also names 980-9I58G-00N030 as a passive single-mode MPO12 APC-to-MPO12 APC fiber cable, 30m. That is a particular listed assembly, not a selected project route length. To carry C01-C12 into B, the external interfaces need their own comparison.

References: [N3][N5]

Resolve the external interface before selecting assemblies

The public Q3450 documents disagree about the physical connector population. The HTML ordering description says 144 MPO connectors, and the specifications page updated September 2, 2026 also lists 144 MPO connectors. The August 21 Cable Installation page instead says 72 front-panel MPO connectors, each serving two independent four-lane XDR ports, totaling 144 ports. These descriptions cannot be used as one consistent physical connector population.

The LinkX product page checked October 20, 2026 adds a naming discrepancy. Its Q3450 copper-cable FAQ calls the fiber connection MMC-12/APC, while the cited hardware manual and topology accessory list use MPO wording. Preserve both names as conflicting evidence; they do not establish interchangeable mating interfaces.

The supplier/OEM owner needs to resolve these questions for B's exact quoted SKU and hardware revision with the applicable faceplate drawing, port-to-connector map, approved external assembly part numbers and connector details. The complete proposed channel must match those returned requirements. This is where the physical-interface uncertainty belongs: it prevents finalizing mating parts, assembly quantities, labels and any patching plan.

C01-C12 therefore remain candidate references against twelve continuing external connection requirements. Neither the switch's headline port total nor the ELS emitter population turns them into twelve approved replacement cables. The final assembly population and mating specification stay unresolved until the hardware-specific return settles them.

References: [N1][N3][N6][N7]

Rebuild the twelve-connection buying comparison

The corrected comparison keeps A's separate switch-side optical-module items, twelve remote module allocations F01-F12 and twelve direct assembly references C01-C12 visible in their original units. It does not derive a switch-module quantity from the twelve connections or the 72 cages. A is the stipulated starting offer, not a validated configuration.

In B, place the integrated switch optics in the supplied switch package and identify the included ELS units with their supply and service owner. Remove the separate switch-side data-transceiver allowance that this package replaces. Restore the twelve remote module requirements that were lost when the entire loose-optics allowance was deleted. Their supported part identities may change; restoring the allowance does not approve retaining A's modules.

Keep the same twelve external connection requirements alongside those remote allocations. C01-C12 carry forward as candidate assembly references, with their parts and allocation subject to the resolved interface and channel definition. If that definition changes the physical assembly arrangement, revise the assembly lines while preserving all twelve endpoint requirements.

The buyer can now compare the supplied optical package, the separately required far-end modules and the remaining external assemblies without omitting the remote optics or counting integrated switch optics twice. This corrected line-item population fixes the buying comparison. It establishes no real module, connector or assembly compatibility, and supplies no price advantage or supported substitution.

References: [N3][N4][N5]

Turn the selected package into an external cabling scope

Once the equipment and channel owners release the actual connection package, set the external cabling boundary at its supplier-approved, field-connected interfaces. For the twelve planned connections, carry the equipment and port identities, assembly parts and lengths, any intermediate patching, approved routes, supply owners and required labels into the issued schedule. The integrated optical engines and internal optical assemblies remain with their named equipment owner; the ELS responsibility stays with the owner identified in B's equipment offer.

The switch substitution also changes facility dependencies. The cited manual describes Q3400-RA as air-cooled and Q3450-LD as liquid-cooled and busbar-powered. Their 4U height does not establish equivalent rack readiness. Cooling and electrical interfaces need the facility and equipment owners' resolution outside the external cabling package; this comparison supplies no connection or energization method.

Leviathan's structured cabling service covers agreed physical routing, dressing, labeling, external connections, checks and handoff records using customer-furnished or separately sourced materials. The engagement establishes the actual permitted tasks, personnel, site requirements and availability. Agree which physical records and checks will be returned and who accepts the optical channel and network operation. Formal instrument testing requires confirmed instruments, personnel, methods and criteria.

For a project inquiry through the structured cabling service and inquiry links below, send both offered switch SKUs and revisions, the resolved interface map, the twelve remote endpoint and module requirements, the proposed assembly schedule, site location and requested physical deliverables. Name the appointed materials supplier and delivery responsibilities. The resulting discussion can price and scope the external physical work against the selected package, with the optical equipment and service responsibilities still attributable to their owners.

References: [N2][N6][L1]