Although IEC 60825-2 does not allow Hazard Level 4, it does allow Class 4 radiation on fiber optic cable.
In the past, Class 4 on fiber was not common place on Optical Networks (ONs), in fact, it was almost unheard of. But now, ONs are transmitting Class 4 radiation on a regular basis. Of course, most ONs have built in Automatic Power Reduction (APR) systems to reduce the Class 4 to Hazard Levels 3B and less in case of a fiber break or fiber disconnect.
However, Class 4 radiation on fiber raises the safety risk significanty. Not only is Class 4 radiation an acute hazard to the eyes and skin, it is also an acute fire hazard to low flammability rated material. IEC TC76 is in the process of preparing a new document intended to give safety guidance to users of ONs transmitting Class 4 radiation. This document is IEC 60825-17.
Laser Product Safety LLC will provide more on this issue in the upcoming months as it develops.