Transmission medium

<p>A transmission medium is a system or substance that can mediate the <a href="/facts/Wave_propagation/PXhWIt7k">propagation</a> of <a href="/facts/Signal/41YqUJ8c">signals</a> for the purposes of <a href="/facts/Telecommunication/vxoj1cxR">telecommunication</a>. Signals are typically imposed on a wave of some kind suitable for the chosen medium. For example, data can modulate sound, and a transmission medium for <a href="/facts/Sound/DlKXlPuF">sounds</a> may be <a href="/facts/Air/hQ95Jznz">air</a>, but solids and liquids may also act as the transmission medium. <a href="/facts/Vacuum/BTk3goyV">Vacuum</a> or air constitutes a good transmission medium for <a href="/facts/Electromagnetic_wave/Ynx7ujCW">electromagnetic waves</a> such as <a href="/facts/Light/jeofpMn4">light</a> and <a href="/facts/Radio_wave/XmB6WPpF">radio waves</a>. While a material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance, by <a href="/facts/Absorption_(electromagnetic_radiation)/xBYKt7yS">absorption</a> or <a href="/facts/Reflection_(physics)/BhcjDs79">reflection</a> or <a href="/facts/Refraction/S8kvSKzM">refraction</a> at the <a href="/facts/Interface_(chemistry)/HnIAndVA">interfaces</a> between media. Technical devices can therefore be employed to transmit or guide waves. Thus, an optical fiber or a copper cable is used as transmission media.
</p><p><a href="/facts/Electromagnetic_radiation/Ynx7ujCW">Electromagnetic radiation</a> can be transmitted through an <a href="/facts/Optical_medium/gm6LqshC">optical medium</a>, such as <a href="/facts/Optical_fiber/5ruuIFbj">optical fiber</a>, or through <a href="/facts/Twisted_pair/L426Jk2C">twisted pair</a> wires, <a href="/facts/Coaxial_cable/aG9FfCpL">coaxial cable</a>, or <a href="/facts/Dielectric/PnVt9P2G">dielectric</a>-slab <a href="/facts/Waveguide/tJS9Y0GH">waveguides</a>.  It may also pass through any physical material that is transparent to the specific <a href="/facts/Wavelength/kcJU0ymz">wavelength</a>, such as <a href="/facts/Water/0lkXnJPK">water</a>, <a href="/facts/Air/hQ95Jznz">air</a>, <a href="/facts/Glass/hezRsAGf">glass</a>, or <a href="/facts/Concrete/K6whGVNx">concrete</a>. <a href="/facts/Sound/DlKXlPuF">Sound</a> is, by definition, the vibration of matter, so it requires a physical medium for transmission, as do other kinds of mechanical waves and <a href="/facts/Heat/FjDGssCs">heat</a> energy. Historically, science incorporated various <a href="/facts/Aether_theories/Gqquyhyv">aether theories</a> to explain the transmission medium. However, it is now known that electromagnetic waves do not require a physical transmission medium, and so can travel through the vacuum of <a href="/facts/Free_space/BTk3goyV">free space</a>. Regions of the <a href="/facts/Electrical_insulation/SfSXkrh5">insulative</a> vacuum can become <a href="/facts/Conductive/BSuyupLP">conductive</a> for <a href="/facts/Electrical_conduction/akyCKvMy">electrical conduction</a> through the presence of free <a href="/facts/Electron/L0KBo5cW">electrons</a>, <a href="/facts/Electron_hole/YymdTv9d">holes</a>, or <a href="/facts/Ion/3bePpDna">ions</a>.
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Transmission medium open-in-new

Transmission medium