A fibre optic cable consists of a bundle of glass or plastic threads that are surrounded by a glass cladding. Fibre optic is a composite material that is able to transmit data, voice and images in a digital format. It is used to replace copper wire in long distance telephone lines, in mobile phones, video cameras and to link computers within local area networks, LAN. Fibre optic is also used in instruments for examining internal parts of the body or inspecting the interiors of manufactured structural products. Fibre optics is widely used because of its low material costs, high transmission capacity, chemical stability and is less susceptible to interference.
Fibre optics (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:
- Core - Thin glass center of the fiber where the light travels
- Cladding - Outer optical material surrounding the core that reflects the light back into the core
- Buffer coating - Plastic coating that protects the fiber from damage and moisture
Optical fibers come in two types:
- Single-mode fibers
- Multi-mode fibers
How do they work?
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. The light in a fiber-optic cable travels through the core (hallway) 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
The Advantages of Fiber Optics
- Less expensive - 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.
- Thinner - 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.
- Light signals - 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.
- Low power - 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.
- Digital signals - Optical fibers are ideally suited for carrying digital information, which is especially useful in computer networks.
- Non-flammable - Because no electricity is passed through optical fibers, there is no fire hazard.
- Lightweight - An optical cable weighs less than a comparable copper wire cable. Fiber-optic cables take up less space in the ground.
- Flexible - Because fiber optics are so flexible and can transmit and receive light, they are used in many flexible digital cameras for the following purposes:
- Medical imaging - in bronchoscopes, endoscopes, laparoscopes
- Mechanical imaging - inspecting mechanical welds in pipes and engines (in airplanes, rockets, space shuttles, cars)
- Plumbing - to inspect sewer lines
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