Direct answer
Longer wavelengths can show greater bend-related excess loss in singlemode fiber. Comparing 1310 and 1550 nm OTDR traces helps identify suspects, but event alignment, acquisition settings and physical routing must be reviewed before a failure decision.
Definition and use cases
Dual-wavelength investigation correlates traces of the same fiber rather than subtracting two overall loss readings. AFL describes a specific OTDR implementation using singlemode 1310/1550 nm comparisons for bend detection. Its algorithm and thresholds are product-specific, not universal acceptance limits.
Use the method after rack rearrangement, during slack-storage review or for installation comparisons. It does not replace total-loss acceptance or uniquely identify every mechanical cause.
Basis：AFL OTDR FAQ。
Investigation record
| Field | Record | Purpose |
|---|---|---|
| Path identity | Same fiber, direction and ports | Compare the same route |
| Acquisition | Wavelength, pulse, range, averaging | Explain resolution and noise |
| Event alignment | Physical location and analysis region | Compare corresponding events |
| Routing | Corners, ties and storage photographs | Review mechanical suspects |
| Repeat test | Matching before/after settings | Preserve comparable evidence |
Recommended investigation sequence
Confirm isolation and instrument suitability, inspect interfaces and review launch-cable configuration. Keep raw traces, not just the automatic verdict. A local excess at the longer wavelength warrants checking the corresponding storage or restraint point.
Make adjustments only within the cable manufacturer's mechanical conditions, then repeat the test. Never deliberately kink a cable to reproduce a fault. If the change is not repeatable, retain alternative explanations. Short assemblies and closely spaced events also require review of dead zones and available resolution before attributing a loss to one component.
Procurement FAQ
- Does higher 1550 nm loss prove a bend? It is a clue, not unique proof.
- Is there one universal threshold? Use the applicable project and instrument method.
- Can a live link be tested directly? Respect isolation, safety and instrument requirements.
- Is a screenshot sufficient? Retain raw traces and settings.
- What evidence should a supplier receive? Fiber ID, location, both traces and routing state.
Related guides and products
Cable bend-radius review · OTDR launch-cable length。
Related product configuration · Contact an engineer。The product link supports configuration review, not an unverified performance or availability claim.
Sources and review date
Sources reviewed: 2026-10-07. Checklists and process recommendations are general procurement guidance, not complete standard clauses or verified ARRANEX product claims.
Sources checked: 2026-10-07