(optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables
and used to transmit light signals over long distances.
If you look closely at a single optical fiber, you will see that it has the following parts:
- Thin glass center of the fiber where the light travels.
- Outer optical material surrounding the core that reflects the light back into the core.
- Plastic coating that protects the fiber from damage and moisture.Hundreds or thousands of these optical fibers are arranged in bundles in optical cables. The bundles are protected by the cable's outer covering, called a jacket
Optical fibers come in two types:Single-mode fibers
- Used to transmit one signal per fiber (used in telephones and cable TV)Multi-mode fibers
- Used to transmit many signals per fiber (used in computer networks, local area networks)
have small cores (about 3.5 x 10-4 inches or 9 microns in diameter) and transmit infrared laser light (wavelength = 1,300 to 1,550 nanometers). •Multi-mode fibers
have larger cores (about 2.5 x 10-3 inches or 62.5 microns in diameter) and transmit infrared light (wavelength = 850 to 1,300 nm) from light-emitting diodes (LEDs).Some optical fibers can be made from plastic
. These fibers have a large core (0.04 inches or 1 mm diameter) and transmit visible red light (wavelength = 650 nm) from LEDs.ADVANTAGES OF FIBER OPTICS
Compared to conventional metal wire (copper wire), optical fibers are:
- Several miles of optical cable can be made cheaper than equivalent lengths of copper wire. This saves your provider (cable TV, Internet) and you money.
- Optical fibers can be drawn to smaller diameters than copper wire.
•Higher carrying capacity
- Because optical fibers are thinner than copper wires, more fibers can be bundled into a given-diameter cable than copper wires. This allows more phone lines to go over the same cable or more channels to come through the cable into your cable TV box.
•Less signal degradation
- The loss of signal in optical fiber is less than in copper wire.
- Unlike electrical signals in copper wires, light signals from one fiber do not interfere with those of other fibers in the same cable. This means clearer phone conversations or TV reception.
- Because signals in optical fibers degrade less, lower-power transmitters can be used instead of the high-voltage electrical transmitters needed for copper wires. Again, this saves your provider and you money.
- Optical fibers are ideally suited for carrying digital information, which is especially useful in computer networks.
- Because no electricity is passed through optical fibers, there is no fire hazard.
- An optical cable weighs less than a comparable copper wire cable. Fiber-optic cables take up less space in the ground. Because of these advantages, you see fiber optics in many industries, most notably telecommunications and computer networks.
"How Fiber Optics Work", HowStuffWorks
), by Craig C. Freudenrich, Ph.D.
HowStuffWorks, Inc., 2002.
Fiber 101: »www.corning.com/opticalfiber/dis ··· ber_101/
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[text was edited by author 2002-07-05 21:41:15]