IEC 61746-2:2010

Overview

IEC 61746-2:2010 - "Calibration of optical time-domain reflectometers (OTDR) - Part 2: OTDR for multimode fibres" defines procedures and uncertainty analysis for calibrating multimode OTDRs. The standard addresses distance and loss scale calibration, measurement errors and uncertainties, and includes an optional test for the OTDR source modal condition (laser modal behaviour). It explicitly does not cover correction of OTDR response.

Keywords: calibrating multimode optical time domain reflectometers (OTDR), OTDR calibration, multimode fibre OTDR.

Key topics and technical requirements

• Scope and applicability: Procedures tailored for OTDRs used with multimode fibres (IEC 60793-2-10 A1 fibres).
• Minimum OTDR features required (to qualify for full calibration):
  • Ability to measure category A1a/A1b multimode fibres
  • Programmable index of refraction (or equivalent)
  • Display of a trace with logarithmic power scale and linear distance scale
  • Two markers/cursors with displayed loss and distance between points
  • Ability to measure absolute distance from OTDR zero reference
  • Ability to report displayed power level relative to a reference level
• Calibration domains covered:
  • Distance calibration (location/length) including models for location deviation and methods such as external source, concatenated-fibre and recirculating delay line
  • Vertical (power/attenuation) scale calibration and loss-difference methods, including long-fibre techniques and determination of displayed power level
  • Measurement errors, uncertainty budgets and how to use calibration results
• Optional tests: Laser source modal condition / near-field characterisation of OTDR sources (related to encircled flux considerations)
• Preparation & quality requirements: Traceability, test conditions, documentation and laboratory organization consistent with metrology best practice

Practical applications and users

• Calibration laboratories and metrology facilities establishing traceable OTDR calibrations for multimode systems
• Telecom test engineers, field service managers and contractors who depend on accurate distance/attenuation readings in multimode links
• OTDR and fibre-equipment manufacturers validating instrument performance and factory calibration
• Standards and compliance teams integrating OTDR calibration into QA and acceptance testing procedures

Benefits: improves confidence in distance measurements, loss characterisation and uncertainty reporting for multimode fibre deployments and maintenance.

Related standards

• IEC 60793-2-10 (multimode fibre product spec)
• IEC 61280 series (encircled flux and multimode attenuation test procedures)
• IEC 61745 (end-face image analysis for fibre geometry)
• ISO/IEC 17025 (competence of testing and calibration laboratories)

Use IEC 61746-2 when calibrating multimode optical time-domain reflectometers (OTDR) to ensure repeatable, traceable distance and loss measurements with documented uncertainty.