Direct answer
Numerical aperture describes angular acceptance, not core diameter or guaranteed coupling efficiency. Compare NA with fiber type, wavelength, definition and method. Multimode review includes both spot size and acceptance angle; singlemode coupling also needs mode matching. A larger NA alone does not establish a more suitable assembly.
Separate angular characteristics from dimensions
Corning's glossary relates NA to the sine of the acceptance half-angle and core/cladding refractive indices. Newport's coupling note separates multimode geometry from singlemode mode matching. Review material characteristics with the complete optical configuration.
Use this guide for OEM inputs, test connections and assembly substitution. It provides no laser-alignment procedure or safe-power design. The equipment owner must establish source, installation and safety requirements; NA does not specify safe power.
| Field | Describes | Retain |
|---|---|---|
| NA | Angular acceptance characteristic | Definition, wavelength, method |
| Core diameter | Core dimensions | Units and fiber identity |
| MFD | Modal field dimensions | Wavelength and definition |
| Connector | Mating construction | Exact interface and polish |
| Coupling result | Complete configuration performance | Source, devices, test scope |
Retain the data-sheet footnote
Corning's SMF-28 Ultra sheet lists NA among typical characterizations with a 1310 nm, one-dimensional far-field scan and 1% power-level definition. This illustrates the attached conditions; its value is not a specification for another assembly.
Give definitions their own RFQ field. Where wavelength, threshold or method differs, obtain an explanation before comparing decimals. Retain typical/guaranteed status, footnotes and material part.
A typical characterization does not automatically become a delivery limit. Agree the required interval, method and evidence rather than turning a material sheet into an assembly guarantee.
Multimode review includes spot and angle
Newport's multimode discussion checks both spot size within the core and angular acceptance. Matching one does not establish the complete coupling requirement.
Provide input requirements and mechanical datums so the optical-design party can select the fiber before comparing constructions. The same LC/SC housing does not establish identical fiber or optical conditions. Review whether original validation covers a substitution.
Singlemode needs more than ray geometry
Newport uses Gaussian mode matching and MFD for singlemode coupling. Retain wavelength, mode and positioning rather than transferring a multimode geometric criterion into singlemode acceptance.
Archive MFD and NA definitions separately, with their wavelengths and methods. No universal NA-to-MFD conversion or guaranteed coupling from similar nominal values is established here.
| RFQ input | Include | Resolve |
|---|---|---|
| Material | Full fiber identity and revision | Same fiber or not |
| Application | Wavelength range and input | Applicable conditions |
| Definition | NA threshold, method, value status | Comparable quantity |
| Interface | Endface, position, retention datums | Repeatable configuration |
| Validation | Reference arrangement and boundary | Substitution decision |
Complete substitution with assembly evidence
Material data supports screening. Finished suitability depends on the actual interface and approved configuration. Retain old/new parts and test revisions rather than labeling one similar field as full equivalence.
No ARRANEX specialty NA or coupling efficiency is promised. Related custom pages organize fiber, interface and construction inputs; performance needs separate confirmation.
Procurement FAQ
- Is NA core diameter? Separate angular acceptance from dimensions.
- Is greater NA always better? Review the source, fiber and complete requirement.
- Does equal NA establish interchangeable fibers? Check definitions, wavelengths, construction and evidence.
- Is NA sufficient for singlemode selection? Review mode matching and applicable MFD data.
- What belongs in the RFQ? Fiber, wavelength, NA definition, interface datums and validation requirements.
Related products and reading
- Custom high-density interconnects
- Custom ferrule construction
- Mode-field diameter and core size
- Cutoff wavelength and short assemblies
Related pages support requirements review. Materials, service conditions, performance and delivery scope depend on mutually confirmed specifications.
Contact an engineer with drawings and validation requirements
Sources and review date
Reviewed on 2026-10-20. Source dates remain separate from the review date. Manufacturer examples explain terminology; procurement tables are editorial recommendations, not ARRANEX specifications or certifications.
Sources checked: 2026-10-20