IEC 62221, which is a technical report , describes four methods (A, B, C and D) for the measurement of microbending sensitivity of optical fibres.
These four methods are distinguished by the equipment being used for measurements and their applications:
method A using an expandable drum and applies to category A1 and class B fibres;
method B using a fixed diameter drum and applies to category A1 and class B fibres;
method C using a plate and applied loads and applies to category A1 and class B fibres;
method D using a \'basketweave\' wrap on a fixed diameter drum, and applies to category A1 and class B fibres
Methods A and B may also be used to measure the microbending sensitivity of optical fibre ribbons.
Methods A and C offer the capability to measure the microbending sensitivity over a wide range of applied linear pressure or loads. Method B may be used to determine the microbending sensitivity for a fixed linear pressure.
Methods A, B and D can also be used at different temperatures (temperature cycling) provided special low thermal expansion materials (e.g. quartz drums) are used.
The results from the four methods can only be compared qualitatively . These methods are considered characterization type tests.
It shall be understood that the microbend results from any method, could have significant variation between laboratories .
These methods do not constitute a routine test used in the general evaluation of optical fibre. This parameter is not generally specified within a detail specification.