IEC 612021-1:2009 applies to isolators used in the field of fibre optics which are non-reciprocal optical devices, passive components and have two optical ports for directionally transmitting optical power. The specific technical changes with regard to the previous edition are: - the definitions have been reconsidered; - environmental category has been deleted from classification; - the clause relating to quality assessment procedures has been deleted; and - annexes A and B have been added.