IEC 63267-2-1:2024定义了50/125µm增强宏观弯曲、渐变折射率多模光纤连接的一组指定条件，该连接是为了满足随机配对的抛光物理接触（PC）光纤中的衰减和回波损耗性能要求而保持的。 根据IEC 61300-1，在850 nm的工作波长下，使用符合环绕通量（EF）的发射条件，根据横向光纤芯偏移、数值孔径（NA）失配和光纤芯直径（CD）变化来确定性能等级。 考虑到最先进的技术，光纤芯角偏移被认为是微不足道的，并且被排除在衰减估计的因素之外。衰减和回波损耗性能等级在IEC 63267-1中定义。

IEC 63267-2-1:2024 defines a set of specified conditions for an enhanced macro bend of 50/125 µm, graded index multimode fibre optic connection that is maintained in order to satisfy the requirements of attenuation and return loss performance in a randomly mated pair of polished physically contacting (PC) fibres. An encircled flux (EF) compliant launch condition in accordance with IEC 61300-1, at an operational wavelength of 850 nm, is used for determination of performance grades, based on lateral fibre core offset, numerical aperture (NA) mismatch, and fibre core diameter (CD) variation. Fibre core angular offset is considered insignificant given the state-of-the-art and is excluded as a factor for attenuation estimation. Attenuation and return loss performance grades are defined in IEC 63267-1.