Dispersion (optics)

In optics, dispersion is a phenomenon that causes the separation of a wave into spectral components with different frequencies, due to a dependence of the wave's speed on its frequency. It is most often described in light waves, though it may happen to any kind of wave that interacts with a medium or can be confined to a waveguide, such as sound waves. There are generally two sources of dispersion: material dispersion, which comes from a frequency-dependent response of a material to waves; and waveguide dispersion, which comes because the transverse mode solutions for waves confined laterally within a finite waveguide generally depend upon the frequency (i.e. on the relative size of the wave, the wavelength, and that of the waveguide).

Related Topics:
Optics - Wave - Frequencies - Light - Sound - Transverse mode - Waveguide - Wavelength

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

A related phenomenon is that of modal dispersion, which comes about if a signal consists of a superposition of multiple modes at each frequency—because different modes generally travel at different speeds, dispersion of temporal features (and thus signal degradation) results. A special case of this is polarization mode dispersion (PMD), which comes from a superposition of two modes that normally travel at the same speed due to symmetry (e.g. two orthogonal polarizations in a waveguide of circular or square cross-section), but which travel at different speeds due to random imperfections that break the symmetry.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~