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03_200023_CH02/Batesx 1/17/01 8:17 AM Page 37

Basic Fiberoptics Technologies 37

Table 2-3
Window of Frequencies Normal Wavelength Used
Comparison of
800-900 nanometers (nm) 850 nm
Frequency
Windows and 1250-1350 nm 1310 nm
Operating
1500-1600 nm 1550 nm
Wavelength Used

described previously.The common wavelengths used in fiber systems
today are shown in Table 2-3. This table indicates that a transmitter
operating at 850 nanometers will produce a range of frequencies
between 800 and 900 nanometers, opening the door for dispersion.
The same is true with the other operating frequencies.

Types of Fiber

Already the discussion has led to differences in the actual glass.
There is fiberoptic, and there is fiberoptic. The characteristics of the
glass differ based on materials and manufacturer. Not all fibers are
the same.When first introduced, fiber quality was less than that pro-
duced by current technology. Moreover, the chemicals used to pro-
duce the glass change the characteristics.The original glass was very
“lossy” and barely suited to use in communications systems.The first
fiber systems in telecommunications networks produced losses in
the range of 20 decibels per kilometer. Improvements in the 1980s
created glass that reduced the loss to 1 decibel per kilometer. Newer
fibers have losses of 0.2 decibels per kilometer or better. The chemi-
cals (dopants) added to the glass change the refractive index of the
glass, creating more absorption, which is a problem.