Direct answer
Average optical power and optical modulation amplitude describe different quantities. PAM4 OMAouter compares outer levels and cannot be recovered from one average reading alone. Retain modulation, per-lane scope, pattern and conditions; shared dBm units do not make results interchangeable in budgets or acceptance tables.
Separate averages from level differences
Keysight's average-power guidance describes the average signal component. Its NRZ OMA guidance uses one/zero power difference and excludes PAM4. The PAM Outer OMA guidance defines the corresponding outer-level measurement.
These sources explain fields rather than validate any module's compliance. Use this guide for data-sheet review, test requests and passive-cabling boundaries, not transmitter design or calibration procedures.
| Field | Describes | Retain |
|---|---|---|
| Average optical power | Average component | Wavelength, port, conditions |
| NRZ OMA | One/zero power difference | NRZ method and pattern |
| PAM4 OMAouter | Outer-level power difference | Applicable method and settings |
| Per-lane result | A specified lane | Lane and wavelength IDs |
| Total output | Aggregate within a boundary | Included channels |
Equal averages can have different level separation
For an original arithmetic example, assume equal high/low occupancy in a simplified NRZ signal. Levels of 1.8/0.2 mW and 1.4/0.6 mW both average 1 mW, but their differences are 1.6 and 0.8 mW.
These are not module measurements or standard-pattern OMA results. They show only why the average is insufficient; they are not a PAM4 acceptance formula.
Also separate linear power from logarithmic units. Subtracting two dBm readings produces a logarithmic ratio, not OMA expressed in dBm. Establish the quantity before applying the approved calculation and units.
Retain pattern and method
Keysight's Outer OMA measurement uses selected symbol sequences rather than eye-opening height alone. Preserve settings instead of treating an attractive eye diagram as proof of all modulation requirements.
A test request should identify module part, format, lane and required results. The responsible party selects applicable settings; a tutorial bandwidth or historical example is not a universal rule for 400G/800G products.
Keep per-lane and aggregate fields distinct
The HUBER+SUHNER 800G example separates per-lane average launch power from total output, while sensitivity specifies OMAouter, lane and TECQ conditions. Only the field relationships are cited, not its limits for another module.
Retain full column names. An OMAouter receiver constraint cannot be directly combined with an average-power number to declare an approved passive-loss budget without review.
| Deliverable | Include | Purpose |
|---|---|---|
| Module data | Full part and revision | Applicable requirements |
| Field dictionary | Original name, unit, definition | Avoid mixed quantities |
| Lane map | Lane, wavelength, port | Identify results |
| Method record | Pattern, reference plane, settings | Preserve conditions |
| Acceptance scope | Separate module/passive checks | Prevent scope extension |
Accept passive assemblies separately
A modulation report does not automatically cover cord endfaces, continuity, mapping or agreed loss. Deliver module and passive records separately, linked by ports and revisions, so exceptions can be investigated.
No ARRANEX transceiver, OMA instrument or compliance-test service is asserted. Related cabling pages organize interface and channel inputs; agree actual assembly delivery separately.
Procurement FAQ
- Does passing average power prove passing OMAouter? Review the different quantities separately.
- Are matching dBm units enough? Check quantity, lane and conditions.
- Can an NRZ OMA method be reused unchanged for PAM4? Select the applicable format-specific method.
- Does total output replace per-lane results? Identify included channels; do not substitute automatically.
- What belongs in the RFQ? Module part, original fields, lane map, required report and passive-test scope.
Related products and reading
- High-density multifiber assemblies
- Data-center migration requirements
- WDM power reports
- FEC and passive-fiber acceptance
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