The module page answers how one layer is separated from the next. An external source, a faceplate connector, and an on-board module can all appear in neighboring discussions. Only the arrangement a document actually names sits at the center of NPO.
CenterSocketed near-package assembly
ASICOptical engine
OptionalExternal light-source module
Present only when the laser sits outside the engine
EdgeFaceplate exit
Pigtail direct, or through another connector
Boundaries on one board. The external source is drawn to the side: it can be chosen, or it can be absent.
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Socketed near-package assembly
This is the structural boundary the framework gives NPO: a common substrate, a packaged ASIC, an engine, and sockets for assembly and rework. NPOTEC uses that assembly relationship as the center of the module plan, so the surrounding materials and devices have a place to sit. It is not a socket that can be ordered.
What changes between designs Retention can be per socket, and the document also mentions shared bolts to cut overhead. Solder reflow remains on the same comparison table for other co-packaged arrangements. In this document, the name near-package optics refers to the socketed arrangement.
The optical engine is the communications device in the framework. Where it sits relative to the ASIC is what makes people call the arrangement co-packaged or near-package. Which lasers, modulators, detectors, and electrical chips remain inside depends on the source path and the electrical interface that were chosen.
What changes between designs Engines in the document may be soldered or socketed, and the discussion includes electrical engines as well as optical ones. A single standard optical engine is not an object the literature provides.
ELSFP is a faceplate-pluggable form factor that delivers continuous-wave light to systems whose optical engines do not integrate the laser, and it is field-replaceable. The agreement says it is aimed primarily at co-packaged optics, including switches, network interface cards, and ASICs used for artificial intelligence and machine learning. The ECOC 2024 deck names co-packaged and near-packaged systems in the same need statement.
What changes between designs Only a design that places the laser outside the engine needs this module. An integrated laser does not take this path. One source can feed more than one engine, and one engine can have several continuous-wave inputs. In the OIF management white paper, the control intelligence sits in the host board controller, not inside the module.
After the optical conversion leaves the front-panel module, the fiber still has to leave the equipment. The framework discusses where fiber or copper exits the assembly, and how faceplate-connector loss spends the optical budget.
What changes between designs A pigtail that reaches the faceplate, or an engine-side connector that is patched onward, are different loss and density choices. The document does not appoint either one as the near-package exit part.
On-board optics is a neighboring class, not an NPO module
Release 1.1 of the COBO on-board optics specification, dated 9 December 2018, defines 8-lane and 16-lane modules mounted on the printed-circuit board, for up to 1×400G and 2×400G, pigtailed or connectorized, and written to stay consistent with 400G front-panel pluggable practice. The specification says the optical physical layer itself is out of scope.
What changes between designs A board-mounted module, a front-panel pluggable, socketed near-package optics, and co-packaging on the same first-level substrate are four mounting boundaries. This site does not file the COBO module as an NPO model, and it does not treat that lane count as an NPO configuration.