Overview
IEC 61746-1:2009 - Calibration of optical time-domain reflectometers (OTDR) – Part 1: OTDR for single mode fibres - defines procedures and measurement methods for calibrating single‑mode OTDRs. The standard focuses on measurement errors, uncertainties, traceability and test procedures; it does not address corrective compensation of OTDR responses. This edition updates and replaces the earlier IEC 61746 (2005) and aligns graphical symbology with IEC/TR 61930.
Key topics and technical requirements
- Scope & preparation
- Requirements for organization, documentation, test conditions and ensuring traceability of measurements.
- Distance calibration
- General models for location deviation and several methods: external source, concatenated fibre, and recirculating delay line. Procedures include equipment configuration, calibration of auxiliary equipment and uncertainty analysis.
- Loss calibration
- Procedures to determine displayed power level and reference loss. Methods include fibre standard, external source, splice simulator and power reduction variants, with guidance on sample placement, polarization dependence and uncertainty calculation.
- Reflectance calibration
- Methods and limits for measuring reflectance with OTDRs, including use of backscatter parameters and reflectance standards.
- Uncertainty & calculations
- Mathematical basis for calculating measurement results and combined uncertainties (normative annexes provide formulas and derivations).
- Normative annexes
- Practical designs and descriptions for equipment and standards used in calibrations (e.g., recirculating delay line, fibre standard, splice simulator, reflectance standard) plus an informative annex on OTDR backscatter theory.
Applications and who should use it
IEC 61746-1 is intended for professionals involved in high‑accuracy optical fiber test and calibration:
- Calibration laboratories and metrology institutes establishing or documenting OTDR calibration services.
- Test equipment manufacturers validating OTDR distance, loss and reflectance performance.
- Telecom operators and contractors who require traceable calibration of field and laboratory OTDRs for fiber characterization, acceptance testing and troubleshooting.
- Standards bodies and QA teams implementing measurement uncertainty and traceability best practices for single‑mode fibre testing.
Practical benefits include consistent, traceable OTDR measurement results, clear uncertainty budgets for distance/loss/reflectance measurements, and standardized methods for verifying OTDR performance.
Related standards
- IEC 61746 (previous edition, 2005) - superseded by this document.
- IEC/TR 61930 - referenced for updated graphical symbology.
- Consult the IEC online catalogue for additional parts and related standards covering optical measurement and test methods.
Open preview (PDF)Calibration of optical time-domain reflectometers (OTDR) - Part 1: OTDR for single mode fibres
