IEC 60793-1-34:2021

Overview

IEC 60793-1-34:2021 - Optical fibres - Part 1-34: Measurement methods and test procedures - Fibre curl defines uniform requirements and test methods for measuring fibre curl (latent curvature) in uncoated optical fibres. Fibre curl is a critical mechanical parameter that affects splice loss when using passive alignment fusion splicers or active alignment mass fusion splicers. This third edition (2021) updates measurement equations and test details from the 2006 edition.

Key topics and technical requirements

• Scope and purpose

  • Measurement of fibre curl (radius of curvature) for uncoated optical fibres (types A1, A2, A3 and B as per IEC 60793).
  • Method A (reference): side view microscopy (visual/digital video).
  • Method B: laser beam scattering using a line sensor.

• Measurement principle

  • An uncoated fibre end is mounted in a rotatable fixture with a specified overhang. The fibre is rotated about its axis and the deflection of the free end is recorded.
  • Typical measurement distance from fixture to measurement point: 10 mm to 20 mm. Excessive overhang risks vibration/gravity effects.

• Apparatus and procedure

  • Fibre holding fixture (v-groove, vacuum chuck or ferrule) and a rotator (manual or stepper motor).
  • Deflection measurement via side-view optics or laser detector; data optionally captured and processed by a computer.
  • Radius of curvature is calculated from the measured deflection using circular models derived in Annex C.

• Techniques and calculations

  • Two analysis techniques are described: extrema technique and Fourier fitting.
  • Annex C provides derivations of circular models for both microscopy and laser-scattering methods.
  • Method A is the reference test used to resolve disputes.

• Notable changes in the 2021 edition

  • Modified derivation equations for laser scattering.
  • Change of angular increment from previous ranges to 10° to 45°.
  • Annex B (laser beam scattering) changed from informative to normative.

Practical applications and who uses this standard

• Primary users

  • Optical-fibre manufacturers and production testing labs.
  • Quality assurance engineers and R&D teams evaluating fibre geometry and process control.
  • Fusion splicer and alignment system designers concerned with minimizing splice loss.
  • Telecom and datacom installers or specifiers verifying component compliance.

• Practical value

  • Ensures consistent, reproducible measurement of fibre curl for manufacturing quality control.
  • Reduces splice-loss variability by controlling curvature-related misalignment.
  • Provides standardized methods for contract testing, dispute resolution and product specifications.

Related standards

• IEC 60793 (all parts) - general series for Optical fibres; IEC 60793-1-34:2021 references and applies within this framework.

Keywords: IEC 60793-1-34:2021, optical fibre, fibre curl, measurement methods, side view microscopy, laser beam scattering, splice loss, radius of curvature, fusion splicer, uncoated optical fibres.