IEC 60793-2-70: 2017 This part of IEC 60793 is applicable to optical fibre types D1, D2, D3, as described in Table 1. These fibres are polarization-maintaining fibre types, and are used or can be incorporated in information transmission equipment and optical fibre cable. These fibres are available for use in optical transport networks. Three types of requirements apply to these fibres:
- general requirements defined in IEC 60793-2;
- specific requirements common to the category D polarization-maintaining fibres covered in this document and which are given in Clause 4;
- particular requirements applicable to individual fibre types or specific applications, which are defined in Annexes A to C.

Table 1- Categories of glass core/glass clad polarization-maintaining fibres

Category	Type	Description
D1	Polarization-maintaining fibre suitable for use at 980 nm	This category of polarization-maintaining fibre is optimised for polarization-maintaining ability in the 980 nm region. This fibre is used for erbium-doped fibre amplifier.
D2	Polarization-maintaining fibre suitable for use at 1 310 nm	This category of polarization-maintaining fibre is optimised for polarization-maintaining ability and connection property of category B fibres in the 1A 310A nm region.
D3	Polarization-maintaining fibre suitable for use at 1 550 nm	This category of polarization-maintaining fibre is optimised for polarization-maintaining ability and connection property of category B fibres in the 1A 550 nm region.