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  1. In optical transmission technology, modes are discrete light waveforms that propagate in the core glass of an optical fiber, provided that the coupling of the light into the fiber occurs below a certain angle, the acceptance angle. Modes reinforce each other through interference and are also called eigenwaves. While in a single-mode fiber only a single mode, the fundamental mode, is capable of propagation, in a multimode fiber there are many hundreds of modes, which differ, among other things, in field distribution and propagation speed. In the case of optical fibers, a distinction is made between monomode fibers, which know only one mode, and multimode fibers, which know many modes of lower and higher order.
    Propagation of light waves in the optical fiber

    Propagation of light waves in the optical fiber

    The low-order modes are more stable than the high-order modes because they propagate along the core glass. The higher order modes can be lost in tight bends or even in FOC connectors.
  2. Modes can occur not only in the core glass, but also in the cladding glass. These are unwanted modes that occur when the refractive index from the cladding glass is higher than the medium surrounding the cladding glass, for example from the plastic coating. Therefore, the refractive index of the plastic coating is slightly higher than that of the cladding glass. This eliminates any cladding glass modes that may occur after the shortest propagation.
  3. The term modes is also used in room acoustics. It is an effect caused by acoustic reflections and standing waves. In this case, the waves reflected in the room superimpose on those radiated by the loudspeaker. As a result, there are positions in the room where sound pressure maxima and sound pressure minima are formed and the listener perceives certain frequencies as more pronounced and longer, while others are weaker and shorter. This modal effect is limited to lower frequencies below 300 Hz because their wavelengths are approximately the same as those in the room.
Englisch: mode
Updated at: 28.11.2016
#Words: 321
Links: indium (In), transmission, light, coupling, acceptance angle
Translations: DE

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