1、附录 一、英语原文 Optical fiber Abstract: An optical fiber (or optical fiber) is a flexible, transparent fiber made of a pure glass (silica) not much thicker than a human hair. It functions as a waveguide, or light pipe1, to transmit light between the two ends of the fiber.2 The field of applied science and
2、 engineering concerned with the design and application of optical fibers is known as fiber optics. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used i
3、nstead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces. Specially-designed fibers
4、are used for a variety of other applications, including sensors and fiber lasers. Optical fibers typically include a transparentcore surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by total internal reflection. This causes the fiber to act as
5、 a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those that only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a wider core diameter, and are used for short-distance communication link
6、s and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,050 meters (3,440 ft). Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and the
7、n spliced together, either mechanically or by fusing them with heat. Special optical fiber connectors for removable connections are also available. 【 keywords】 optical Fiber Multi-mode fiber Index of refraction Total internal reflection absorption Fiber optics, though used extensively in the modern
8、world, is a fairly simple, and relatively old, technology. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon and Jacques Babinetin Paris in the early 1840s. John Tyndall included a demonstration of it in his public lectures in L
9、ondon, 12 years later.3 Tyndall also wrote about the property of total internal reflection in an introductory book about the nature of light in 1870: 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
10、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
11、angle of the medium. For water this angle is 4827, for flint glass it is 3841, while for diamond it is 2342.45 Unpigmented human hairs have also been shown to act as an optical fiber.6 Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth centu
12、ry. Image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for internal medical examinations by Heinrich Lamm in the following decade. Modern optical fibers, whe
13、re the glass fiber is coated with a transparent cladding to offer a more suitable refractive index, appeared later in the decade.3 Development then focused on fiber bundles for image transmission. Harold Hopkins and Narinder Singh Kapany at Imperial College in London achieved low-loss light transmis
14、sion through a 75 cm long bundle which combined several thousand fibers. Their article titled A flexible fibrescope, using static scanning was published in the journal Nature in 1954.78 The first fiber optic semi-flexible gastroscope was patented by Basil Hirschowitz, C. Wilbur Peters, and Lawrence
15、E. Curtiss, researchers at the University of Michigan, in 1956. 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. In 1880 Alexander Graham Bell and Su
16、mner Tainter invented the Photophone at the Volta Laboratory in Washington, D.C., to transmit voice signals over an optical beam.9 It was an advanced form of telecommunications, but subject to atmospheric interferences and impractical until the secure transport of light that would be offered by fibe
17、r-optical systems. In the late 19th and early 20th centuries, light was guided through bent glass rods to illuminate body cavities.10Jun-ichi Nishizawa, a Japanese scientist at Tohoku University, also proposed the use of optical fibers for communications in 1963, as stated in his book published in 2
18、004 in India.11 Nishizawa invented other technologies that contributed to the development of optical fiber communications, such as the graded-index optical fiber as a channel for transmitting light from semiconductor lasers.1213 The first working fiber-optical data transmission system was demonstrat
19、ed by German physicist Manfred Brner at Telefunken Research Labs in Ulm in 1965, which was followed by the first patent application for this technology in 1966.1415Charles K. Kao and George A. Hockham of the British company Standard Telephones and Cables (STC) were the first to promote the idea that the attenuation in optical fibers could be reduced below 20 decibels per kilometer (dB/km), making fibers a practical communication medium.16
