Light guide

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As a light guide of transparent components such as fibers, tubes or rods are designated, the light transport over short or long distances. The light guide is either by reflection at the interface of the light guide

  • by total reflection due to a lower refractive index of the medium surrounding the light guide or
  • by mirroring the interface or
  • achieved by a suitable refraction gradient.

The main representative is the fiber optic cable , which is mainly used in communications technology and which owes its name to the essential role of the wave properties of light there. Since the optical waveguides often consist of glass fibers , these are also referred to as glass fiber cables or fiber optic cables . In addition to data transmission, they are also used in fiber optic sensors , for imaging and lighting purposes , e.g. B. in endoscopes , for the flexible transport of laser radiation , as well as in lighting installations or for decoration. Optical fibers also include fibers that are partially or entirely based on plastic , such as polymer optical fibers and hard clad silica optical fibers .

Other light guides are planar fiber optic structures (PLWL), which are used in components of integrated optics , such as. B. switches and switches for optical communications technology. The light guides also include light-conducting components made of plastic, such as. B. PMMA or polycarbonate , for displays or for background lighting (Edge Lit Display). In addition, so-called light tubes are used to illuminate buildings with natural sunlight .

The mineral ulexite - in the form of parallel-fiber fragments - is an example of a naturally occurring light guide.


Philipp Bozzini invented one of the first "light guides" in 1806, in which candlelight is guided into body cavities and hollow organs via a system of mirrors and tubes. With this he created the first endoscope . In 1870, John Tyndall tried to direct light into and through a jet of water after Jean-Daniel Colladon had already demonstrated this. In the mid-1950s, optical conductors were primarily used to illuminate internal organs in medical technology. After the development of the laser , it became possible from the mid-1960s to use light guides as light wave guides for the transmission of messages.

Individual evidence

  1. Erwin Böhmer, Dietmar Ehrhardt, Wolfgang Oberschelp: Elements of applied electronics: Compendium for training and occupation. Page 282, Vieweg + Teubner, ISBN 9783834805430 ( Google Books ).
  2. Entry on Ulexit. In: Römpp Online . Georg Thieme Verlag, accessed on December 3, 2016.
  3. Philipp Bozzini: The light guide or description of a simple device and its application to illuminate inner caves and spaces in the living animal body. Weimar 1807; Reprint Stuttgart 1988 (= publication series of the Max-Nitze-Museum , 6.2).
  4. Otto Winkelmann : The Frankfurt light guide - new building according to old plans. On the early history of endoscopy. In: Würzburg medical history reports. Volume 14, 1996, pp. 11-15.
  5. ^ Daniel Colladon: Sur les réflexions d'un rayon de lumière à l'interiéur d'une veine liquide parabolique . In: Comptes rendus . tape 15 , no. 1800 , 1842.