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Fiber Optics |
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| The technology |
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| Light does travel in straight lines, thus when there are bends in wires through which the light travels, there is considerable loss of transmission. Fiber optics uses a principle known as internal reflection that allows light to travel long distances without any loss. |
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| The light in a fiber-optic cable travels through the core by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances. However, some of the light signal degrades within the fiber, mostly due to impurities in the glass. The extent that the signal degrades depends on the purity of the glass and the wavelength of the transmitted light (for example, 850 nm = 60 to 75 percent/km; 1,300 nm = 50 to 60 percent/km; 1,550 nm is greater than 50 percent/km). Some premium optical fibers show much less signal degradation -- less than 10 percent/km at 1,550 nm. |
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| A Fiber-Optic Relay System |
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| Fiber-optic relay systems consist of the following: |
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- Transmitter - Produces and encodes the light signals
- Optical fiber - Conducts the light signals over a distance
- Optical regenerator - May be necessary to boost the light signal (for long distances)
- Optical receiver - Receives and decodes the light signals
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| Transmitter |
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| The transmitter is like the sailor on the deck of the sending ship. It receives and directs the optical device to turn the light "on" and "off" in the correct sequence, thereby generating a light signal. |
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| The transmitter is physically close to the optical fiber and may even have a lens to focus the light into the fiber. The most common wavelengths of light signals are 850 nm, 1,300 nm, and 1,550 nm (infrared, non-visible portions of the spectrum). |
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| Optical Receiver |
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| The optical receiver takes the incoming digital light signals, decodes them and sends the electrical signal to the other computers, televisions and telephones.. The receiver uses a photocell or photodiode to detect the light. |
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