From Wikimedia Commons, the free media repository. Silizezkoa edo plastikozkoa izan daiteke, eta, argi-seinaleak ez ezik, soinua eta datuak transmititzeko ere erabiltzen da. Subcategories This category has the following 9 subcategories, out of 9 total. Pages in category "Optical fibers" This category contains only the following page. Optical fiber.
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An optical fiber is a flexible, transparent fiber made by drawing glass silica or plastic to a diameter slightly thicker than that of a human hair. Fibers are used instead of metal wires because signals travel along them with less loss ; in addition, fibers are immune to electromagnetic interference , a problem from which metal wires suffer.
Optical fibers typically include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide.
Multi-mode fibers generally have a wider core diameter  and are used for short-distance communication links and for applications where high power must be transmitted. Being able to join optical fibers with low loss is important in fiber optic communication. For applications that demand a permanent connection a fusion splice is common. In this technique, an electric arc is used to melt the ends of the fibers together.
Another common technique is a mechanical splice , where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors.
The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. The term was coined by Indian-American physicist Narinder Singh Kapany , who is widely acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinet in Paris in the early s.
John Tyndall included a demonstration of it in his public lectures in London , 12 years later. When the light passes from air into water, the refracted ray is bent towards the perpendicular When the ray passes from water to air it is bent from the perpendicular If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the ray will not quit the water at all: it will be totally reflected at the surface The angle which marks the limit where total reflection begins is called the limiting angle of the medium.
In the late 19th and early 20th centuries, light was guided through bent glass rods to illuminate body cavities. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the s. In the s, Heinrich Lamm showed that one could transmit images through a bundle of unclad optical fibers and used it for internal medical examinations, but his work was largely forgotten.
Wilbur Peters, and Lawrence E. Curtiss, researchers at the University of Michigan , in In the process of developing the gastroscope, Curtiss produced the first glass-clad fibers; previous optical fibers had relied on air or impractical oils and waxes as the low-index cladding material. Kapany coined the term fiber optics , wrote a article in Scientific American that introduced the topic to a wide audience, and wrote the first book about the new field.
At the time, the use in the cameras was classified confidential , and employees handling the cameras had to be supervised by someone with an appropriate security clearance. Charles K. Kao and George A.
They correctly and systematically theorized the light-loss properties for optical fiber and pointed out the right material to use for such fibers— silica glass with high purity. This discovery earned Kao the Nobel Prize in Physics in Maurer , Donald Keck , Peter C. Initially, high-quality optical fibers could only be manufactured at 2 meters per second. Chemical engineer Thomas Mensah joined Corning in and increased the speed of manufacture to over 50 meters per second, making optical fiber cables cheaper than traditional copper ones.
The Italian research center CSELT worked with Corning to develop practical optical fiber cables, resulting in the first metropolitan fiber optic cable being deployed in Turin in The erbium-doped fiber amplifier , which reduced the cost of long-distance fiber systems by reducing or eliminating optical-electrical-optical repeaters, was co-developed by teams led by David N.
The emerging field of photonic crystals led to the development in of photonic-crystal fiber ,  which guides light by diffraction from a periodic structure, rather than by total internal reflection. The first photonic crystal fibers became commercially available in Optical fiber is used as a medium for telecommunication and computer networking because it is flexible and can be bundled as cables.
It is especially advantageous for long-distance communications, because infrared light propagates through the fiber with much lower attenuation compared to electrical cables. This allows long distances to be spanned with few repeaters. The net data rate data rate without overhead bytes per fiber is the per-channel data rate reduced by the FEC overhead, multiplied by the number of channels usually up to 80 in commercial dense WDM systems as of [update].
Fiber is also immune to electrical interference; there is no cross-talk between signals in different cables and no pickup of environmental noise. Non-armored fiber cables do not conduct electricity, which makes fiber a good solution for protecting communications equipment in high voltage environments, such as power generation facilities, or metal communication structures prone to lightning strikes, and also preventing problems with ground loops.
They can also be used in environments where explosive fumes are present, without danger of ignition. Wiretapping in this case, fiber tapping is more difficult compared to electrical connections, and there are concentric dual-core fibers that are said to be tap-proof. Fibers are often also used for short-distance connections between devices.
For example, most high-definition televisions offer a digital audio optical connection. Information traveling inside the optical fiber is even immune to electromagnetic pulses generated by nuclear devices. Copper cable systems use large amounts of copper and have been targeted for metal theft , since the s commodities boom.
Fibers have many uses in remote sensing. In some applications, the sensor is itself an optical fiber. In other cases, fiber is used to connect a non-fiberoptic sensor to a measurement system. Depending on the application, fiber may be used because of its small size, or the fact that no electrical power is needed at the remote location, or because many sensors can be multiplexed along the length of a fiber by using different wavelengths of light for each sensor, or by sensing the time delay as light passes along the fiber through each sensor.
Time delay can be determined using a device such as an optical time-domain reflectometer. Optical fibers can be used as sensors to measure strain , temperature , pressure , and other quantities by modifying a fiber so that the property to measure modulates the intensity , phase , polarization , wavelength , or transit time of light in the fiber.
Sensors that vary the intensity of light are the simplest since only a simple source and detector are required. A particularly useful feature of such fiber optic sensors is that they can, if required, provide distributed sensing over distances of up to one meter. In contrast, highly localized measurements can be provided by integrating miniaturized sensing elements with the tip of the fiber.
Extrinsic fiber optic sensors use an optical fiber cable , normally a multi-mode one, to transmit modulated light from either a non-fiber optical sensor—or an electronic sensor connected to an optical transmitter. A major benefit of extrinsic sensors is their ability to reach otherwise inaccessible places. An example is the measurement of temperature inside aircraft jet engines by using a fiber to transmit radiation into a radiation pyrometer outside the engine.
Extrinsic sensors can be used in the same way to measure the internal temperature of electrical transformers , where the extreme electromagnetic fields present make other measurement techniques impossible.
Extrinsic sensors measure vibration, rotation, displacement, velocity, acceleration, torque, and torsion. A solid-state version of the gyroscope, using the interference of light, has been developed. The fiber optic gyroscope FOG has no moving parts and exploits the Sagnac effect to detect mechanical rotation.
Common uses for fiber optic sensors include advanced intrusion detection security systems. The light is transmitted along a fiber optic sensor cable placed on a fence, pipeline, or communication cabling, and the returned signal is monitored and analyzed for disturbances.
This return signal is digitally processed to detect disturbances and trip an alarm if an intrusion has occurred.
Optical fibers are widely used as components of optical chemical sensors and optical biosensors. Optical fiber can be used to transmit power using a photovoltaic cell to convert the light into electricity.
Optical fibers have a wide number of applications. They are used as light guides in medical and other applications where bright light needs to be shone on a target without a clear line-of-sight path. In some buildings, optical fibers route sunlight from the roof to other parts of the building see nonimaging optics. Optical-fiber lamps are used for illumination in decorative applications, including signs , art , toys and artificial Christmas trees. Optical fiber is an intrinsic part of the light-transmitting concrete building product LiTraCon.
Optical fiber can also be used in structural health monitoring. This type of sensor is able to detect stresses that may have a lasting impact on structures. It is based on the principle of measuring analog attenuation. Optical fiber is also used in imaging optics. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging device called an endoscope , which is used to view objects through a small hole. Medical endoscopes are used for minimally invasive exploratory or surgical procedures.
Industrial endoscopes see fiberscope or borescope are used for inspecting anything hard to reach, such as jet engine interiors. Many microscopes use fiber-optic light sources to provide intense illumination of samples being studied. In spectroscopy , optical fiber bundles transmit light from a spectrometer to a substance that cannot be placed inside the spectrometer itself, in order to analyze its composition.
A spectrometer analyzes substances by bouncing light off and through them. By using fibers, a spectrometer can be used to study objects remotely. An optical fiber doped with certain rare-earth elements such as erbium can be used as the gain medium of a laser or optical amplifier.
Rare-earth-doped optical fibers can be used to provide signal amplification by splicing a short section of doped fiber into a regular undoped optical fiber line.
The doped fiber is optically pumped with a second laser wavelength that is coupled into the line in addition to the signal wave. Both wavelengths of light are transmitted through the doped fiber, which transfers energy from the second pump wavelength to the signal wave.
The process that causes the amplification is stimulated emission. Optical fiber is also widely exploited as a nonlinear medium. The glass medium supports a host of nonlinear optical interactions, and the long interaction lengths possible in fiber facilitate a variety of phenomena, which are harnessed for applications and fundamental investigation. Optical fibers doped with a wavelength shifter collect scintillation light in physics experiments.
Fiber-optic sights for handguns, rifles, and shotguns use pieces of optical fiber to improve visibility of markings on the sight. An optical fiber is a cylindrical dielectric waveguide nonconducting waveguide that transmits light along its axis, by the process of total internal reflection.
The fiber consists of a core surrounded by a cladding layer, both of which are made of dielectric materials. The boundary between the core and cladding may either be abrupt, in step-index fiber , or gradual, in graded-index fiber.
The index of refraction or refractive index is a way of measuring the speed of light in a material.
A fiber-optic cable , also known as an optical-fiber cable , is an assembly similar to an electrical cable , but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed. Different types of cable  are used for different applications, for example, long distance telecommunication , or providing a high-speed data connection between different parts of a building. Optical fiber consists of a core and a cladding layer, selected for total internal reflection due to the difference in the refractive index between the two. In practical fibers, the cladding is usually coated with a layer of acrylate polymer or polyimide. This coating protects the fiber from damage but does not contribute to its optical waveguide properties. Individual coated fibers or fibers formed into ribbons or bundles then have a tough resin buffer layer or core tube s extruded around them to form the cable core.