Quality Control
Which OTDR and Attenuation Records Should Buyers Request Before Shipment?
A buyer-focused guide to optical test records, wavelengths, drum and fibre identification, OTDR settings, attenuation results, calibration status and release evidence.
Define the question before asking for an OTDR report
Buyers often request an 'OTDR report' without stating whether they need factory-length verification, optical continuity, attenuation, event location or an installed-link acceptance record. These are not identical tasks. For a manufactured cable drum, the contract should identify the required optical measurements, the applicable product or test standard, wavelengths, sampling basis and acceptance limits. The record should demonstrate that the fibres in the shipped drum match the approved specification, not merely that an instrument displayed a trace.
Keep attenuation measurement and trace interpretation distinct
Attenuation is the loss of optical power over a defined length and wavelength. OTDR estimates loss and distance from backscatter and reflections along the fibre. Its result depends on settings, launch conditions, fibre characteristics and analysis method. A trace is valuable for detecting continuity, length and localized events, but it should not automatically replace the attenuation method required by the purchase specification. Ask the supplier to name the method used and explain how the reported value is calculated.
Record wavelengths and test conditions
The report should state the wavelengths used, because a value without wavelength is not auditable. It should also identify fibre type, test direction when relevant, launch and receive arrangements, pulse width, range, index of refraction or group index setting, averaging time and any event thresholds needed to interpret the trace. Buyers do not need to prescribe every instrument setting for a routine factory test, but the saved file or report must contain enough context for a qualified reviewer to understand what was measured.
Tie every result to fibre, cable length and drum
A useful record identifies the purchase order or production order, cable model, fibre count, fibre or colour identifier, drum or reel number, nominal and measured length, test date and operator or station. The same drum number should appear on the packing list and label. If the supplier provides representative rather than 100-percent results, the sampling plan must be stated. Screenshots with cropped identifiers or reused filenames are weak evidence because they cannot be reconciled to the shipment.
Check instrument identity and calibration status
Record the instrument manufacturer, model and serial number and confirm that calibration or verification status was valid on the test date. IEC 61746-1 addresses calibration of single-mode OTDRs and highlights measurement errors and uncertainties; it does not turn any trace into product acceptance. The supplier's internal procedure should control equipment, reference cords, connectors and data storage. Dirty connectors or an unsuitable range can create misleading events even when the instrument itself is calibrated.
Review traces for consistency, not decorative screenshots
Check that the displayed length is plausible for the drum, the fibre identifier is correct, both requested wavelengths are present where applicable and the noise floor or end event does not hide part of the cable. Unexpected steps, reflectance or apparent gainers and losers should be investigated. Bidirectional analysis may be required for accurate splice-loss evaluation on installed links, while a factory drum without splices has a different purpose. Avoid applying installed-link rules blindly to a production length.
Build a compact pre-shipment evidence pack
For each accepted drum, request the drum schedule, routine optical result, any agreed OTDR file or PDF, metre-mark or length evidence, label photo and packing status. Add the approved datasheet, inspection summary, deviation log and certificate of conformity where contractually required. Use consistent filenames such as order-drum-fibre-wavelength so the evidence remains usable after delivery. A smaller, reconciled pack is stronger than hundreds of unidentified images.
State acceptance and re-test rules in the purchase order
Define who reviews a failed or questionable result, whether the fibre is re-tested after connector cleaning or cable-end preparation, how rework is documented and when a drum must be replaced. Specify whether native instrument files are required in addition to PDFs. Send Jiaxin Fiber the cable model, fibre type, wavelengths, project limits, drum schedule and reporting format before production so the test workflow and release package can be prepared around the actual order.
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