This International Standard applies to optical amplifiers (OAs) and optically amplified, elementary sub-systems for terrestrial applications, using active fibres (optical fibre amplifiers, OFAs) containing rare-earth dopants, which are commercially available. The black box approach is used in this IEC standard. The black box approach is adopted in order to give product specifications which are independent of OA implementation details. For reliability qualification purposes, some information about the internal components is neede d; these internal parts are themselves treated as black boxes. This standard gives requirements for the evaluation of OA reliability by combining the reliability of such internal black boxes. The object of this International Standard is the following: " ðto specify the requirements for the reliability assessment of OFAs; " ðto provide assistance to the purchaser in the selection of consistently high quality OA products for his particular applications; " ðto give the minimum list of reliability qualification tests, requirements on failure criteria during testing and on reliability predictions, and give the relevant normative references. In particular, this International Standard is intended: " ðto establish a standard method for the assessment of the reliability of OFA d evices and sub-systems in order to minimize risks and to promote product development and reliability qualification; " ðto establish means to determine the distribution of failures in time in order to enable the determination of equipment failure rates for specified end-of-life criteria. In addition, guidance is given on: " ðthe controls a customer should make, prior to procurement of an OFA, on the test procedures an OFA manufacturer has in place in order to guarantee product reliability; " ðthe procedures to verify the reliability claims of an OFA manufacturer.