wavelengths greater than 1400 nm are significantly higher that 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, lla, IlIa, lllb, or IV.
The International Electro-technical Commission (IEC) is an
international standards body that writes laser safety standards under
IEC-60825. Classification schemes are similar and divided into
Classes 1, 1M, 2, 2M, 3B, 3R 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 circuit packs 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 circuit pack shelves. The circuit packs themselves,
however, may be FDA/CDRH Class I, IIIb, or IV or IEC Class 1, 1M,
3B, 3R or 4. State of the art Raman and EDFA optical amplifiers have
now extended into the Class IV/4 designations
Laser safety precautions
for optical fiber
telecommunications
systems
In its normal operating mode, an optical fiber telecommunication
system is totally enclosed and presents no risk of eye injury. It is a
Class I/1 system under the FDA/CDRH and IEC classifications.
The fiber optic cables that interconnect various components of an
optical fiber telecommunication system can disconnect or break, and
may expose people to lightwave emission. Also, certain measures and
maintenance procedures may expose the technician to emission from
the semiconductor laser during installation and servicing. Unlike more
familiar laser devices, such as solid-state and gas lasers, the emission
pattern of a semiconductor laser results in a highly divergent beam. In
a divergent beam, the irradiance (power density) decreases rapidly
with distance. The greater the distance, the less energy will enter the
eye and the less potential risk for eye injury. Inadvertently viewing an
unterminated fiber or damaged fiber with the unaided eye at distances
greater than 5 to 6 inches normally will not cause eye injury provided
the power in the fiber is less than a few milliwatts at the near IR
wavelengths and a few tens of milliwatts at the far IR wavelengths.
Laser safety
Safety
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365-372-333 R2.1
Issue 4, June 2005
Lucent Technologies
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