| Full title | Optical fibres. Part 2-10: Product specifications. Sectional specification for category A1 multimode fibres |
| Publisher | IEC, TC 86/SC 86A Fibres and cables |
| Current edition | Edition 7.0, 22 May 2019, with Amendment 1, 27 January 2022 (consolidated edition 7.1) |
| Status | Published. Edition 7.0 replaced the sixth edition of 2017 |
| Also published as | EN IEC 60793-2-10:2019 in Europe |
| Related standards | IEC 60793-2; IEC 60793-1 series (test methods); ISO/IEC 11801-1; ANSI/TIA-568.3; IEC 61280-4-1 |
What it covers
IEC 60793-2-10 is the IEC product specification for category A1 multimode fibre. A1 fibre is graded index. The standard covers the bare fibre, which is then built into cables and equipment.
Three types of requirement apply:
- General requirements for all optical fibres, from IEC 60793-2.
- Requirements common to all A1 fibres, in Clause 5.
- Requirements for each sub-category, in the normative Annexes A to D.
Uses listed in the scope include data centres, LANs and SANs, and on-premises intra-building and inter-building installations.
Sub-categories and naming
The 2019 edition changed the names of the A1 sub-categories to match the OM grades in ISO/IEC standards. Table 1 of the standard cross-references the new and old names.
| Current name | 2017 name | Nominal core | ISO/IEC 11801-1 cabled grade | Annex |
|---|---|---|---|---|
| A1-OM1 | A1b | 62.5 µm | OM1 | B |
| A1-OM2 | A1a.1 | 50 µm | OM2 | A |
| A1-OM3 | A1a.2 | 50 µm | OM3 | A |
| A1-OM4 | A1a.3 | 50 µm | OM4 | A |
| A1-OM5 | A1a.4 | 50 µm | OM5 | A |
| A1d | A1d | 100 µm | None | C |
The fibres are 50/125 µm, 62.5/125 µm and 100/140 µm graded index. A1-OM2 to A1-OM5 are four bandwidth grades of 50/125 µm fibre.
Each 50 µm grade comes in two macrobend levels. The suffix a means traditional macrobend loss. The suffix b means enhanced macrobend loss, that is, lower loss.
Bandwidth
Multimode grades are separated mainly by modal bandwidth. Overfilled launch bandwidth relates to LED-type sources. Effective modal bandwidth (EMB) relates to laser (VCSEL) sources and is assured by differential mode delay (DMD) requirements in Annex D.
| Grade | Core | OFL 850 nm | OFL 1300 nm | EMB 850 nm |
|---|---|---|---|---|
| OM3 | 50 µm | 1 500 MHz·km | 500 MHz·km | 2 000 MHz·km |
| OM4 | 50 µm | 3 500 MHz·km | 500 MHz·km | 4 700 MHz·km |
| OM5 | 50 µm | 3 500 MHz·km | 500 MHz·km | 4 700 MHz·km |
These are the minimum values commonly published for A1-OM3 to A1-OM5 fibre and for the matching ISO/IEC 11801-1 cabled grades. The normative values are in Table A.3 of the standard. A1-OM5 is also specified for single or multi-wavelength systems from 850 nm to 950 nm, with a minimum EMB of 2 470 MHz·km at 953 nm. The standard includes informative wideband bandwidth data for A1-OM3 and A1-OM4 over the same range, but this is not normative.
How it relates to ISO/IEC 11801-1
IEC 60793-2-10 specifies fibre. ISO/IEC 11801-1 specifies cabled fibre grades, OM1 to OM5, for generic cabling. An OM4 cable normally contains A1-OM4 fibre.
- The standard notes that OM1 and OM2 cables are not supported for new installations under ISO/IEC 11801-1:2017.
- ISO/IEC 11801:2002 also allowed OM2 cable made with 62.5 µm fibre, and OM1 cable made with 50 µm fibre. Those combinations are not part of IEC 60793-2-10.
- ANSI/TIA-568.3-D uses the same OM names as ISO/IEC 11801-1.
Test methods
Measurements use the IEC 60793-1 series. Examples include IEC 60793-1-20 for fibre geometry, 1-40 for attenuation, 1-41 for bandwidth, 1-47 for macrobending loss and 1-49 for differential mode delay. IEC 61280-4-1 is cited for multimode attenuation measurement of installed cable plant.
What to check on a datasheet
- The IEC designation, such as A1-OM4, or the older A1a.3 on older documents. Both describe the same grade.
- Whether the fibre is an a or b type, if tight bends are expected in enclosures.
- EMB at 850 nm for laser-based applications, and EMB at 953 nm if the fibre is sold as OM5.
- That cable and connectors in one link use the same core size. 50 µm and 62.5 µm fibres should not be mixed.
Related reading: OM4 vs OM5 fibre: which should you specify? · Single-mode vs multimode fibre: OM3, OM4 and OS2 explained.