This part of IEC60825 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. This part of IEC60825 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 IEC60825 , a reference to ‘laser’ is taken to include light-emitting diodes (LEDs) and optical amplifiers.