Overview
EN ISO 13485:2003 (IEC 61746-1:2009) specifies procedures and requirements for the calibration of Optical Time‑Domain Reflectometers (OTDR) intended for single‑mode fibres. The standard defines how to prepare, execute and document traceable calibrations of OTDR distance, loss and reflectance measurements to ensure reliable field and laboratory test results. It is the European adoption of the IEC text (EN 61746‑1:2011) and is aimed at calibration laboratories, manufacturers and operators of fibre‑optic test equipment.
Key topics and technical requirements
- Scope and preparation for calibration
- Organizational responsibilities, traceability to national/international standards and required documentation.
- Test conditions and preparation steps to ensure reproducible OTDR calibrations.
- Distance (time‑scale) calibration
- Definitions (e.g., location deviation model, attenuation dead zone) and general calibration strategy.
- Methods described include the external source method, concatenated fibre method, and recirculating delay line method.
- Procedures for calibrating OTDR distance scale, system insertion delay and reporting location uncertainty.
- Loss (attenuation) calibration
- Determination of displayed power level and selection of appropriate reference loss points.
- Test planning, sample placement for reliable loss samples and handling of polarization dependence.
- Methods include fibre standard, external source, splice simulator, and power reduction methods with associated uncertainty treatment.
- Reflectance calibration
- Objectives and measurement methods using OTDR traces, including use of the backscatter parameter (K).
- Range, equipment, measurement procedures and uncertainty evaluation for reflectance.
- Normative annexes and supporting material
- Annexes provide designs/specifications for recirculating delay lines, fibre standards, splice simulators, reflectance standards and the mathematical basis.
- Metrological requirements
- Emphasis on measurement uncertainty, calibration procedures, traceability and application of ISO/IEC 17025 principles.
Practical applications - who uses this standard
- Calibration and metrology laboratories providing accredited OTDR calibrations.
- Equipment manufacturers validating OTDR performance during production.
- Telecommunications operators and contractors ensuring test instruments measure fibre length, loss and reflectance accurately in deployments and acceptance testing.
- R&D and test houses developing measurement methods or comparing OTDR models.
Related standards and references
Keywords: OTDR calibration, single‑mode fibre, IEC 61746-1, EN 61746-1, distance calibration, loss calibration, reflectance calibration, measurement uncertainty, traceability.
