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There are three main parts within this fast cable.
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
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
Multi-mode fibers
Single-mode fibers have small cores and transmit infrared laser light, while Multi-mode fibers have larger cores and transmit infrared light 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.
How Does an Optical Fiber Transmit Light?
Suppose you want to shine a flashlight beam down a long, straight hallway. Just point the beam straight down the hallway – light travels in straight lines, so it is no problem. What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway is very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.
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.
So, why are fiber-optic systems revolutionising telecommunications?
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
Because of these advantages, you see fiber optics in many industries, most notably telecommunications and computer networks. For example, if you telephone Europe from the United States (or vice versa) and the signal is bounced off a communications satellite, you often hear an echo on the line. But with transatlantic fiber-optic cables, you have a direct connection with no echoes.
Understanding the safety hazards that go with fiber optic cable is critical for those who install or maintain fiber optic systems
Since fiber optic cable carries no electricity, we don’t worry about electrocution. Similarly, we don’t think about personal or property damage due to fire because it isn’t a source of heat or combustion. In fact, since its light source is invisible to the naked eye, we aren’t even sure when it’s transmitting data signals. It’s this lack of understanding that poses the greatest threat to those of us installing or maintaining fiber optic systems.
Dangerous situations arise when untrained people pick up a live fiber, and look directly into it. They see no light. Therefore, they assume there’s no danger. However, such unsuspecting people can end up with a burned retina in a very short time.
Although fiber optics can solve data communications problems, they are not needed everywhere. Most computer data goes over ordinary wires. Most data is sent over short distances at low speed. In ordinary environments, it is not practical to use fiber optics to transmit data between personal computers and printers as it’s too costly. But, who won’t prefer fiber communicating? I certainly would.
