IEC 61745:2017 describes the calibration of test sets that perform end-face image analysis, also known as "near-field" or "grey-scale" analysis. The principles, however, can be applied to test sets of a different type. The procedures outlined are performed by calibration laboratories and by the manufacturers or users of geometry test sets, for the purpose of calibrating geometry test sets and for evaluating the uncertainties in measurements made on calibrated test sets. The calibration of fibre coating or cable measurement test sets is not covered by this document. This second edition cancels and replaces the first edition, published in 1998, and constitutes a technical revision.This edition includes the following significant technical changes with respect to the previous edition: a) removal of the limitation of single mode optical fibre geometry test sets to include multimode; b) addition of a new annex as mathematical basis. Keywords: end-face image analysis, optical fibre geometry test sets