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Appendix B
Laser Safety Guidelines
Lasers and Eye Damage
Classification of Lasers
Laser Safety Precautions for Optical Fiber Communication Systems
The optical energy emitted by laser and high-radiance LEDs in the 400-1400 nm range may
cause eye damage. When a beam of light enters the eye, the eye magnifies and focuses the
energy on the retina magnifying the irradiance. The irradiance of the energy that reaches
the retina is approximately 10
intense, may burn the retina.
The damage mechanism at the wavelengths used in an optical fiber telecommunications is
thermal in origin, i.e., damage caused by heating. A specific amount of energy is required
for a definite time to heat an area of retinal tissue. Damage to the retina occurs only when
you look at the light sufficiently long that the product of the retinal irradiance and the
viewing time exceeds the damage threshold. Optical energies above 1400 nm cause corneal
and skin burns but do not affect the retina. The thresholds for injury at wavelengths greater
than 1400 nm are significantly higher than for wavelengths in the retinal hazard region
Manufacturers of lasers and laser products in the U.S. are regulated by the Food and Drug
Administration's Center for Devices and Radiological Health (FDA/CDRH) under 21 CFR
1040. These regulations require manufacturers to certify each laser or laser product as
belonging to one of four major Classes: I, II, IIa, IIIa, IIIb, or IV.
The International Electro-Technical Commission is an international standards body that
writes laser safety standards under IEC-60825. Classification schemes are similar with
Classes divided into Classes 1, 2, 3A, 3B, and 4.
Lasers are classified according to the accessible emission limits and their potential for
causing injury. Optical fiber telecommunication systems are generally classified as Class I/1
because, under normal operating conditions, all energized laser transmitting modules are
terminated on optical fibers which enclose the laser energy with the fiber sheath forming a
protective housing.
Also, a protective housing/access panel is typically installed in front of the laser modules
frames. The modules themselves, however, may be FDA/CDRH Class I or IIIb; or IEC Class 1,
3A, or 3B.
In its normal operating mode, an optical fiber communication system is totally enclosed and
presents no risk of eye injury. It is a Class I/1 system under the FDA and IEC classifications.
The fiber optic cables that interconnect various components of an optical fiber can
disconnect or break, and may expose people to laser emissions. Also, certain measures and
maintenance procedures may expose the technician to emission from the semiconductor
laser during installation and servicing.
5
or 100,000 times more than at the cornea and, if sufficiently
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