IEC 61977:2020作为IEC 61977:2020 RLV提供，其中包含国际标准及其红线版本，显示了与上一版本相比技术内容的所有变化。IEC 61977:2020适用于光纤滤波器系列。这些组件具有以下所有一般功能: -它们是无源的，因为它们不包含可以处理发射到输入端口的光信号的光电或其他转换元件； -它们修改光谱强度分布以选择一些波长并抑制其他波长； -它们是固定的，即光谱强度分布的修改是固定的并且不能被调谐； -它们具有用于传输光功率的输入和输出端口或公共端口(具有输入和输出两者的功能)；端口是光纤或光纤连接器； -它们根据其特征而不同。它们可以分为以下几类: -短波通过(仅通过小于或等于指定值的波长)； -长波通过(仅通过大于或等于指定值的波长)； -带通(仅允许光学窗口)； -陷波(仅光学窗口被抑制)； -增益平坦化(补偿器件的光谱分布)。 也可以具有上述类别的组合。本文件提供了通用信息，包括IEC 61753-04x系列文件的术语。参考书目中列出了已发布的IEC 61753-04x系列文件。本文件建立了光学、机械和环境性能的统一要求。这第四版取消并取代了2015年出版的第三版。本版构成技术修订版。与上一版相比，此版本包括以下重大技术变更: -更改对光纤固定滤波器的限制的标题和范围； -增加反映新标题的新术语和定义； -删除IEC TS 62627-09中重复的术语和定义； -图1至图5的垂直轴的协调； -修订第4条，反映最新的技术和市场情况。

IEC 61977:2020 is available as IEC 61977:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61977:2020 applies to the family of fibre optic filters. These components have all of the following general features:
- they are passive for the reason that they contain no optoelectronic or other transducing elements which can process the optical signal launched into the input port;
- they modify the spectral intensity distribution in order to select some wavelengths and inhibit others;
- they are fixed, i.e. the modification of the spectral intensity distribution is fixed and cannot be tuned;
- they have input and output ports or a common port (having both functions of input and output) for the transmission of optical power; the ports are optical fibre or optical fibre connectors;
- they differ according to their characteristics. They can be divided into the following categories:
- short-wave pass (only wavelengths lower than or equal to a specified value are passed);
- long-wave pass (only wavelengths greater than or equal to a specified value are passed);
- band-pass (only an optical window is allowed);
- notch (only an optical window is inhibited);
- gain flattening (compensating the spectral profile of the device).
It is also possible to have a combination of the above categories. This document provides the generic information including terminology of IEC 61753-04x series documents. Published IEC 61753-04x series documents are listed in the Bibliography. This document establishes uniform requirements for optical, mechanical and environmental properties. This fourth edition cancels and replaces the third edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- change of the title and the scope for the limitation to fibre optic fixed filters;
- addition of new terms and definitions reflecting new title;
- removal of terms and definitions duplicated in IEC TS 62627-09;
- harmonization of the vertical axis of Figures 1 to 5;
- restructuration of Clause 4 reflecting the latest technical and market situation.