glass fiber: see fiberglass.

fiber, dietary, bulky part of food that cannot be broken down by enzymes in the small intestine of the digestive system. Almost all natural fiber comes from plants. Although fiber has little nutritional value, it offers other health benefits. By adding bulk to the diet, fiber prevents constipation, minimizes intestinal disorders, and may serve as an aid in dieting. The benefits of consuming foods high in fiber include lower blood levels of cholesterol and triglycerides. Foods high in fiber include legumes, green, leafy vegetables, whole fruits, and unrefined foods such as bran and sprouted seeds. Fiber is also known as roughage. Robert L. Ory, Grandma Called It Roughage: Fiber Facts and Fallacies (1991).

fiber optics, transmission of digitized messages or information by light pulses along hair-thin glass fibers. Each fiber is surrounded by a cladding having a high index of refractance so that the light is internally reflected and travels the length of the fiber without escaping. Cables of optical fibers can be made smaller and lighter than conventional cables using copper wires or coaxial tubes, yet they can carry much more information, making them useful for transmitting large amounts of data between computers and for carrying data-intensive television pictures or many simultaneous phone conversations. Optical fibers are immune to electromagnetic interference (from lightning, nearby electric motors, and similar sources) and to crosstalk from adjoining wires, and tapping into them is more easily detected. To keep a signal from deteriorating, optical fibers require fewer repeaters over a given distance than does copper wire. In addition to communications, optical fibers are beginning to be used in medical procedures, automobiles, and aircraft and are expected to have many other applications.

fiber, threadlike strand, usually pliable and capable of being spun into a yarn. Many different fibers are known to be usable; some 40 of these are of commercial importance, and others are of local or specialized use. Fibers may be classified as either natural or synthetic. The natural fibers may be further classed according to origin as animal, vegetable, or inorganic fibers.

Animal fibers are composed chiefly of proteins; they include silk, wool, and hair of the goat (known as mohair), llama and alpaca, vicuña, camel, horse, rabbit, beaver, hog, badger, sable, and other animals. Vegetable fibers are composed chiefly of cellulose and may be classed as short fibers, e.g., cotton and kapok; or long fibers, including flax, hemp, Manila hemp, istle, ramie, sisal hemp, and Spanish moss. The chief natural inorganic fiber is asbestos. Fibers are also derived from other inorganic substances that can be drawn into threads, e.g., metals (especially gold and silver). Artificial fibers can be produced either by the synthesis of polymers (nylon) or by the alteration of natural fibers (rayon).

Fibers are classified according to use as textile, cordage, brush, felt, filling, and plaiting fibers. The largest volume is used for textiles and cordage. The chief textile fibers used for clothing and domestic goods are cotton, wool, rayon, nylon, flax, and silk. Coarse-textured fibers (principally jute) are used for burlap, floor covering, sacks, and bagging materials. Cordage fibers include most of the long vegetable fibers and cotton. Brush fibers include istle, sisal, broomcorn, palmyra, and animal hairs. The chief felt fibers are rabbit and beaver hair. Filling fibers include horsehair, wool flock, kapok, cotton, and Spanish moss. Plaiting fibers are used for braided articles (e.g., hats, mats, and baskets) and include Manila hemp, sisal, rushes, and grasses.

Flax, hemp, and wool have been used extensively from remote times; cotton, however, became the leading commercial fiber c.1800. The demand for fibers was greatly increased by the invention of spinning and weaving machinery during the Industrial Revolution. The artificial fibers (see synthetic textile fibers) have rapidly grown in diversity and extent of use since the development of rayon in 1884.

Thin transparent fibres of glass or plastic that transmit light through their length by internal reflections, used for transmitting data, voice, and images. Fibre-optic technology has virtually replaced copper wire in long-distance telephone lines and is used to link computers in local area networks, with digitized light pulses replacing the electric current formerly used for the signal. Telecommunication using fibre optics is usually conducted with infrared light. Fibre optics uses light in the visible wavelengths to transmit images directly, in various technical devices such as those developed for endoscopy.

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