Eye protection in DWDM systems -- what threshold?

At what power level do DWDM systems become dangerous to work near (i.e. not staring into any optics, using light meters, etc)? I never see technicians on inside DWDM systems using eye protection, but I see power levels of amps going higher and higher. On a recent meter I saw almost .6mW... Any pointers to a document saying 1550nm becomes dangerous at xxxx dbM? Thanks in advance, DJ