IEC 60793-1-41:2024

Overview

IEC 60793-1-41:2024 specifies standardized measurement methods and test procedures for determining the modal bandwidth of multimode optical fibres. The fourth edition (2024) updates the previous 2010 edition and adds a direct reference for Method A and Method B. It defines three complementary approaches-time-domain pulse distortion, frequency-domain response, and a DMD-based calculation-to evaluate the fibre baseband frequency response used in production, research and specification of multimode fibres.

Key topics and technical requirements

• Three measurement methods
  • Method A - Time domain (pulse distortion): measures baseband response by observing the broadening of a narrow light pulse.
  • Method B - Frequency domain: directly measures the baseband frequency response using a sinusoidally modulated light source.
  • Method C - OMBc (Overfilled Modal Bandwidth calculated from DMD): uses weighted differential mode delay (DMD) data to calculate the overfilled-launch modal bandwidth; applicable to A1-OM3 to A1-OM5 multimode fibres only.
• Launch conditions
  • Overfilled launch (OFL) and Restricted mode launch (RML) are specified for Methods A and B; the appropriate launch condition is chosen based on fibre type.
  • Method C assumes an overfilled launch when applying DMD weighting.
• Apparatus and procedures
  • Requirements cover radiation sources, launch systems (including mode scramblers), detection and recording systems, computational equipment and overall system performance.
  • Annexes include normative material on mode scrambler requirements, transfer functions, DMD weighting (850 nm), and bandwidth calculation conventions (e.g., −3 dB bandwidth).
• Practical notes
  • These test methods are commonly used in production and laboratory settings and are not easily performed in the field.
  • OFL values historically represent LED-based applications; laser sources (e.g., VCSELs) require other considerations (see IEC 60793-1-49 and IEC 61280-4-1).

Applications - who uses this standard

• Fibre manufacturers for production test and quality control of multimode fibres.
• Component and system designers validating bandwidth performance for data-centre, LAN and short-reach network links.
• Test laboratories and R&D teams performing modal dispersion and DMD analyses.
• Standards and compliance engineers specifying bandwidth limits and test conditions for product datasheets and procurement.

Related standards

• IEC 60793-2-10, IEC 60793-2-30, IEC 60793-2-40 series - fibre category definitions and characteristics.
• IEC 60793-1-49 - methods for effective modal bandwidth of laser-optimized 50 µm fibres.
• IEC 61280-4-1 - multimode fibre test methods (laser/source-dependent considerations).

Keywords: IEC 60793-1-41, modal bandwidth, multimode optical fibre, measurement methods, Method A, Method B, Method C, overfilled launch (OFL), restricted mode launch (RML), differential mode delay (DMD), OMBc, fibre testing.