IEC 61977 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 can not be tuned;
- they have a maximum of two ports 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).
It is also possible to have a combination of the above categories.
This standard establishes uniform requirements for the following:
- optical, mechanical and environmental properties; measurement and test procedures for quality assessment.