This International Standard deals with reliability assessment of laser modules used for telecommunication. The aim of this standard is: ?C to establish a standard method of assessing the reliability of laser modules in order to minimize risks and to promote product development and reliability; ?C to establish means by which the distribution of failures with time can be determined. This should enable the determination of equipment failure rates for specified end of life criteria. In addition@ guidance is given on: ?C the testing that a system supplier should ensure is in a place prior to procurement of a laser module from a laser module manufacturer; ?C a range of activities expected of a system supplier to verify a laser module manufacturer's reliability claims. Further details concerning the rationale are given in annexes A and B.