Currently we have five cabled all-silica structured fibre optic standards Categories specified in the published generic structured fibre optic cabling standards. Internationally, ISO/IEC 11801 Ed 2.1:2009 specifies Categories OM1, OM2, OM3 and OS1. Another amendment of ISO/IEC 11801, to be published in early 2010, is also going to include Category OS2 (which already exists in ISO/IEC 24702; Generic cabling for industrial premises). In Europe and the UK, BS EN 50173-1:2007 contains all five specifications but the specifications for OS1 differ to that of the ISO/IEC standards.
Category OM4 cabled optical fibre is to be specified in amendments of both ISO/IEC 11801 and BS EN 50173-1. This information explains the linkage between optical fibres specifications, cabled optical fibre Categories and optical fibre cable standards Table 1 and Table 2 shows the performance requirements for the cabled optical fibre Categories in the ISO/IEC and EN standards including the changes in the amendments listed above (more details about OM4 and its role are given in a separate White Paper)..
BS EN 60793-2-10 (equivalent to IEC 60793-2-10) specifies types or categories (the two words are used interchangeably in the standard) of Multimode optical fibres designated A1. A1a optical fibres are 50/125 m and A1b optical fibres are 62,5/125 m. A1a is subdivided into A1a.1 and A1a.2 and in future a A1a.3 will be included to support the production of OM4 cabled optical fibre. OM1 and OM2 can be produced from any A1a.* or A1b optical fibre. OM3 requires the use of A1a.2 (although in the future A1a.3 could also be used when finally specified).
BS EN 60793-2-50 (equivalent to IEC 60793-2-50) specifies classes of Singlemode optical fibres. OS2 requires the use of B1.3 optical fibre only. The difference between the international and European standards is found in the optical fibres used to build OS1 cabled optical fibre. EN 50173-1 requires either optical fibre of class B1.3 or class B6_a and cabled performance is specified at 1310nm, 1383 nm and 1550 nm. The ISO/IEC fibre optic standard specifies OS1 to be produce from B1.1, B1.3 or B6_a optical fibres. The addition of B1.1. prevent the specification of the whole set at 1383 nm (B1.1 is allowed to have a water peak and would not pass any requirement applied at that wavelength)
The IEC and EN committees have strengthened the relationship between optical fibre specifications of the BS/EN -IEC 60793 series, Categories of cabled optical fibre and the cables themselves in the production of their cable standards listed below which contain references to OM1, OM2, OM3 and OS1:
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