Laser Safety Guidelines - Alcatel-Lucent 1200 User Manual

Laser Safety Guidelines

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General Laser Information
Optical fiber telecommunication systems, their associated test sets, and similar operating
systems use semiconductor laser transmitters that emit infrared (IR) light at wavelengths
between approximately 800 nanometers and 1600 nanometers. The emitted light is above
the red end of the visible spectrum, which is normally not visible to the human eye.
Although radiant energy at near-IR wavelengths is officially designated invisible, some
people can see the shorter wavelength energy even at power levels several orders of
magnitude below any that have been shown to cause injury to the eye.
Conventional lasers can produce an intense beam of monochromatic light. The term
monochromaticity means a single wavelength output of pure color that may be visible or
invisible to the eye. A conventional laser produces a small-size beam of light, and because
the beam size is small the power density (also called irradiance) is very high. Consequently,
lasers and laser products are subject to federal and applicable state regulations as well as
international standards for their safe operation.
A conventional laser beam expands very little over distance, or is said to be very well
collimated. Thus, conventional laser irradiance remains relatively constant over distance.
However, lasers used in lightwave systems have a large beam divergence, typically 10 to
20 degrees. Here, irradiance obeys the inverse square law (doubling the distance reduces
the irradiance by a factor of (4) and rapidly decreases over distance.
Lasers and Eye Damage
The optical energy emitted by laser and high-radiance LEDs in the 400-1400 nm range may
cause eye damage if absorbed by the retina. 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 105 or 100,000 times more than at the
cornea and, if sufficiently intense, may cause a retinal burn.
The damage mechanism at the wavelengths used in an optical fiber telecommunications is
thermal in origin, such as damage caused by heating. Therefore, 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 one looks 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.
Classification of Lasers
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
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