IEC 61291-2:2016(E) provides a performance specification template which applies to optical amplifiers (OAs) to be used in single channel applications. Multichannel applications are covered in IEC 61291-4. The object of this performance specification template is to provide a frame for the preparation of performance standards and/or product specifications on the performance of OA devices to be used in single channel applications. In the performance standards or product specifications, other specifications such as ratings, operating conditions, tests and pass/fail criteria could be included in addition to the requirements based on this performance specification template. Product specification writers may add specification parameters and/or groups of specification parameters for particular applications. However, product specification writers should not remove specification parameters specified in this standard. This fourth edition cancels and replaces the third edition published in 2012. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - the title of this standard has been changed from digital applications to single channel applications; - the scope has been changed and, as a result, the titles of tables have been changed; - Terms and definitions have been revised; - three tables regarding the minimum list of relevant parameters of power amplifiers, pre-amplifiers and line amplifiers based on semiconductor optical amplifier (SOA) components have been added; - transient parameters have been added in the minimum list of relevant parameters of pre-amplifiers and line amplifiers based on optical fibre amplifier (OFA) module. Keywords: optical amplifiers (OAs) used in single channel applications