IEC 60793-1-49:2018

Overview

IEC 60793-1-49:2018 is an international standard published by the International Electrotechnical Commission (IEC) that specifies the measurement methods and test procedures for assessing differential mode delay (DMD) in optical fibres. This standard applies exclusively to multimode, graded-index glass-core fibres categorized as A1. The core objective is to provide a rigorous and repeatable method to characterize the modal structure of graded-index multimode fibres, which is critical for evaluating their bandwidth performance.

The third edition of this standard incorporates important technical revisions aimed at improving measurement accuracy and extending the methodology to fibres with smaller DMD values and higher modal bandwidths-such as type A1a.3 fibres used in OM4 cables. These advancements ensure better alignment with the original application goals and enable more precise bandwidth assessments relevant to modern laser transmitters and other launch conditions.

Key Topics

• Differential Mode Delay (DMD): Measurement of time delays between different propagation modes to assess modal dispersion effects within multimode fibres.
• Modal Structure Characterization: Detailed mapping of fibre modal behavior to predict performance under various launch conditions.
• Measurement Apparatus: Guidelines for suitable optical sources, probe fibres, scanning stages, and detection systems to ensure consistent testing.
• Test Sample Preparation: Criteria for specimen length, end-face quality, deployment, and positioning critical to valid test results.
• Data Acquisition and Analysis: Procedures for pulse timing, deconvolution, and calculation of effective modal bandwidth (EMB) including minimum EMB metrics.
• Chromatic Dispersion Considerations: Methods to limit and account for the influence of chromatic dispersion on measurements to isolate pure modal delay.
• Standard Compliance: Recommended reporting details and documentation practices for transparency and repeatability.
• Technical Improvements: Introduction of four-quadrant scanning, detector response specifications, and radial uniformity in bandwidth calculations.

Applications

IEC 60793-1-49:2018 is vital for a range of optical fibre manufacturing and research scenarios, particularly where bandwidth performance under different modal excitation conditions must be known. Practical applications include:

• Optical Fibre Production: Quality control testing during fibre draw to verify compliance with modal bandwidth specifications.
• Cable Manufacturing: Performance validation for OM4 and other high-bandwidth multimode fibre cables used in data centres and enterprise networking.
• Research and Development: Characterizing new fibre designs or optical components that interact with multimode fibre networks.
• System Design: Assisting network planners and engineers in selecting fibres that meet the required bandwidth and modal dispersion criteria for specific transmission equipment.
• Laser Transmitter Compatibility: Ensuring fibre modal properties support standardized laser sources for optimized system performance.

Due to the complexity and equipment required, the testing method is primarily implemented in controlled lab environments rather than in field installations.

Related Standards

• IEC 60793-2-10: Specifies the categories of multimode fibre and associated performance criteria, including A1 and A1a.3 types referenced in IEC 60793-1-49.
• IEC 60793 (Parts 1-1 to 1-48): Covers other measurement methods and test procedures related to optical fibres.
• IEC 60794: Defines specifications for optical fibre cables, which utilize fibres tested according to IEC 60793 series.
• IEC 61280 series: Details optical fibre communication system test methods complementary to fibre characterization.

Summary

IEC 60793-1-49:2018 is an essential standard for ensuring the accurate measurement of differential mode delay in graded-index multimode fibres. This information determines how well a fibre will perform in high-speed, multimode communication systems under various launch conditions and with different types of laser transmitters. Its detailed protocols and updated technical methods facilitate reliable bandwidth assessments, supporting advancements in optical fibre manufacturing, cable design, and systems engineering.

Keywords: differential mode delay, DMD measurement, multimode optical fibre, graded-index fibre, modal structure, effective modal bandwidth, EMB, OM4 fibre, laser transmitter compatibility, optical fibre testing, IEC optical fibre standards.