IEC 61300-3-28:2012 describes methods to measure fast variation of attenuation due to mechanical stresses applied on optical fibres and passive optical components during their lifetime. This method is not designed to measure very fast transient losses (with duration less than 1 ms) that could affect the performance of transmission systems. It is optimised to detect transient losses caused by mechanical stresses due to the tests prescribed in the component performance standards, whose duration is generally longer than several tens of milliseconds. Changes from the previous edition of the document are to update the test method and to reconsider the requirements. Keywords: Transient loss