IEC 61300-3-35:2022 is concerned with the observation and classification of debris, scratches and defects. The inspection requirements are based on IEC TR 62627-05. Advice for cleaning of contamination from fibres/ferrule is found in IEC TR 62627-01 and a recommendation is given in Annex D. IEC TR 62572-4 provides the cleaning method for a stub for optical transceivers. Visual inspection is in addition to, and does not replace measurement of performance parameters such as attenuation and return loss, or end face parameters. The dimensions specified are chosen such that they can be easily estimated. Not only the zones A and B on the fibre are inspected for defects and scratches but the whole contact area (where the two fibres/ferrules meet when mated) needs to be inspected for contamination (this is up to 250 µm diameter for cylindrical ferrules and the whole ferrule surface for rectangular ferrules).The objectives of this document are the following: - specify the minimum criteria for a microscope to be compliant to this document; - specify the procedure and criteria for inspecting fibre-optic end faces for cleanliness to determine if the end faces are fit for use. All connector optical interfaces (IEC 61755 series and IEC 63267 series) are based on physical contact between fibre cores; - provide quantitative criteria for the analysis of end face images. This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - adding of a statement that visual inspection is not a substitute for optical qualification such as attenuation and return loss measurement; - adding of some terms and definitions; - adding requirements for SM 35 dB connectors; - adding of a sentence in Clause 5 concerning the susceptibility of the methods to system variability and variability within systems from same supplier; ...