Level 1: During normal operation, there will be no harmful light radiation to humans.

Level 2: Its radiation range is in the visible spectral region, and the AEL value is equivalent to the value when exposed to level 1 product radiation for 0.25 seconds. This level of product requires additional warning signs and safety testing.

Level 3: divided into levels 3a and 3b. For individuals with a 3a level who do not have normal strong light avoidance reactions, the level does not harm the naked eye, but using a lens instrument to observe can harm the eyes. B-level products include radiation within the range, which can cause accidental injury if viewed directly with the naked eye. Its management and control are stricter than Level 2.

Level 4: AEL is above level 3, which not only causes eye damage when viewed directly, but also causes external damage in other situations. It can not only harm the eyes, but also the skin, and even cause a fire. Strictly manage and control such products.

According to the CDRH standard, the output power of laser and single-mode fiber optic communication systems should be below 8.5mW, which is the fourth level. According to IEC standards, for fiber optic communication systems using lasers and single-mode fibers, the output power of the first level product should be less than level 3 and greater than level 4.

After the introduction of fiber amplifiers into optical communication systems, the radiation safety of fiber amplifiers, as a laser product, has also attracted attention due to their higher output power than ordinary semiconductor lasers. The International Telecommunication Union (ITU-T) also considers the safe use of lasers when formulating standards for optical communication systems, especially when using fiber amplifier systems such as wavelength division multiplexing.

Laser cutting machines are different from other ordinary light sources. Because of its monochrome, coherence, collimation and high energy density, the laser generated by the laser can achieve a more concentrated energy effect, thus damaging human organ (especially the human eye). The harm of infrared spectral region lasers to the human body is mainly due to thermal effects, while the harm to blue and purple spectral region lasers is mainly due to photochemical effects. Therefore, when the human eye accidentally faces the laser directly from the laser or fiber optic connector, it may cause harm to the eyes.