IEC TR 60825-17:2015(E) recommends safety measures to protect against effects caused exclusively by thermal, opto-mechanical and related effects in passive optical components and optical cables used in high power optical fibre communication systems. It does not apply to the use of high power optical systems in explosive atmospheres or the use of optical fibres in material processing machines. Throughout this part of IEC 60825, a reference to laser is taken to include light-emitting diodes (LEDs) and optical amplifiers. This second edition cancels and replaces the first edition published in 2010. This edition constitutes a technical revision.