IEC 60794-2-21:2019

Overview

IEC 60794-2-21:2019 is the detailed IEC specification for multi-fibre optical distribution cables for use in premises cabling (indoor cables). It defines cable-level requirements that ensure compatibility with the ISO/IEC 11801 generic cabling series and references the IEC 60794-2-20 family specification. The 3rd edition (with Amendment 1) incorporates modern cabled fibre performance categories (notably OM5 and OS1a) and updates normative status for legacy classes (OM1, OM2, OS1 retained for information).

Key topics and requirements

• Scope and conformity
  • Applies to multi-fibre indoor distribution cables used in customer premises; requirements complement IEC 60794-2-20.
  • Fibre selection for cable testing follows IEC 60794-1-1, Annex B.
• Fibre performance categories
  • Recognized cabled fibre codes: OM3, OM4, OM5, OS1a, OS2 for compatibility with ISO/IEC 11801.
  • OM1/OM2/OS1 are retained informationally but are no longer normative in the latest edition.
• Optical transmission limits
  • Multimode attenuation (max): typically 3.0 dB/km at 850 nm and 1.5 dB/km at 1 300 nm for OM3/OM4/OM5.
  • Single-mode attenuation: OS1a max 1.0 dB/km (1310/1383/1550 nm); OS2 max 0.4 dB/km (same wavelengths).
• Bandwidth (multimode)
  • Minimum uncabled fibre bandwidths specified in MHz·km (examples):
    • OM3: nominal 1500 MHz·km at 850 nm; effective modal guidance (953 nm) ~1 033 MHz·km.
    • OM4: nominal 3500 MHz·km at 850 nm; effective modal guidance (953 nm) ~1 459 MHz·km.
    • OM5: nominal 3500 MHz·km at 850 nm; overfilled and effective values quoted at 953 nm (e.g., effective ~2 470 MHz·km).
• Environmental and mechanical
  • Temperature cycling testing per IEC 60794-2-20 with MICE classification temperature ranges (e.g., −10 °C to +60 °C; −25 °C to +70 °C; −40 °C to +70 °C). Test specimen length and allowable attenuation changes are specified/negotiable between customer and supplier.

Applications - who uses this standard

• Cable manufacturers and designers specifying indoor multi-fibre distribution cables.
• System integrators, data centre and enterprise network designers ensuring ISO/IEC 11801 compatibility.
• Spec writers, procurement teams and testing laboratories validating cable performance (attenuation, bandwidth, environmental behaviour).
• Installation contractors and facility managers selecting multi-fibre distribution solutions for premises cabling.

Related standards

• IEC 60794-2-20 (family specification for multi-fibre optical cables)
• IEC 60794-1-1 (generic cable testing)
• IEC 60793-2-10 / IEC 60793-2-50 (fibre product specifications for multimode and single-mode)
• ISO/IEC 11801 (generic cabling for customer premises)

Keywords: IEC 60794-2-21, multi-fibre distribution cables, indoor optical fibre cables, OM5, OS1a, ISO/IEC 11801, attenuation, bandwidth, MICE classification.