Application of optical communication demonstration set employing LEDs both as light transmitting and receiving elements for education in various generations

Abstract

Light emitting diodes (LEDs) can act, not only as a light emitting element, but also as a light receiving element when being irradiated with light beams of an appropriate wavelength range in an appropriate manner. By employing this aspect, a simple demonstration set for optical communication has been prepared, in which LEDs are employed both as a light transmitting element and a light receiving element. In this set, LEDs with different colors can be selected as the light transmitting element and the light receiving element. Audio signals (music) can or cannot be reproduced in accordance with combinations of colors of these two LEDs. Thus, this demonstration set can act as a useful introductory tool for explaining relationships among colors of light (wavelengths or frequencies) from LEDs, their energy levels and band gap energies of semiconductor materials used for light emitting layers of the particular LEDs.