Laser safety precautions for optical fiber telecommunication 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 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 laser
emissions. 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 un-terminated fiber or damaged fiber with the unaided eye at
distances greater than 130 to 160 mm (5 to 6 in) 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. However, damage may occur if
an optical instrument such as a microscope, magnifying glass, or eye loupe is used to
stare at the energized fiber end.
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