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is important to note that the frequencies used in
fiber optics are not visible to the human eye. To
protect their eyesight, technicians should NEVER
look directly at a fiber connector end, or the output
of a fiber transmitter, without being positive that
there is no light energy being emitted.
Remember,
the laser light sources used in fiber optics can
cause vision damage with repeated exposure!
The
frequencies used in fiber optics are not a range,
but are quite exact. For example, the frequencies
used in multimode are not those between 850 and
1300nm; they are at 850 or 1300nm, plus or minus
10nm. The range from 1550 to 1625nm is used for
Dense Wave Division Multiplexing (DWDM), which
is discussed later in this course.
The
frequencies used in fiber optics are standardized
for the transmission equipment and the testers
used to verify the quality of a fiber link. By
using standard testing equipment, the fiber optic
technician can test a fiber link at the same frequency(s)
that are going to be used by the optoelectronic
transmission devices.
Returning to the the previous highway example,
the technician can test the highway (fiber link)
at the same speed (wavelength) that the selected
vehicle (transmitters and receivers) will be driven.
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