IEC 61753-051-3: 2013 contains the minimum initial test and measurement requirements and severities which a fibre optic attenuator satisfies in order to be categorized as meeting the requirements of single-mode fibre, plug-style fixed attenuator devices used in uncontrolled environments. Optical performances specified in this standard relate to plug-style configurations optical attenuators only. This second edition cancels and replaces the first edition published in 2001 and constitutes a technical revision. The specific technical changes from the previous edition are to reconsider test details and requirement and the constitution of the standard. Keywords: fibre optic attenuator, uncontrolled environments