What Are Normal and Anomalous Dispersion?

In summary, the conversation discusses the concepts of normal and anomalous dispersion, which refer to the behavior of light in different wavelengths in a medium. The difference in signs for dispersion is due to the use of frequency derivative in ultrafast optics and wavelength derivative in fiber optics. The zero dispersion wavelength is a special point where there is no dispersion. This is commonly used in communication systems.
  • #1
sad life
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i need to know what r normal and anamolous dispersion?
 
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  • #2
From website:

http://www.rp-photonics.com/dispersion.html
Normal and Anomalous Dispersion

One distinguishes normal dispersion (for k'' > 0) and anomalous dispersion (for k'' < 0). Normal dispersion usually occurs for transparent media in the visible spectral region. Great care is recommended when the sign of dispersion is specified, because the ultrafast optics community identifies this with the sign of k'', while the opposite sign is usually used in fiber optics, where the dispersion is often specified with the parameter

dispersion of fibers

which is normally given in units of ps/(nm km) (picoseconds per nanometer and kilometer). The different signs result from using a frequency derivative in one case and a wavelength derivative in the other case. Note also that the conversion factor depends on the wavelength.

Between wavelength regions with normal and anomalous dispersion, there is a zero dispersion wavelength. The region around this wavelength can be special in some respects, not only concerning weak dispersive pulse broadening.
 
  • #3
To summarise Steve's post, normal dispersion occurs where shorter wavelengths travel slower than longer wavelengths. Anomalous dispersion occurs when shorter wavelengths travel faster than longer wavelengths.

The zero dispersion point for optic fibres is around 1550 nm, which is why most communications systems use this wavelength.

Claude.
 

FAQ: What Are Normal and Anomalous Dispersion?

What is normal and anomalous dispersion?

Normal and anomalous dispersion are two types of dispersion, which is the phenomenon of different wavelengths of light traveling at different speeds through a medium. Normal dispersion refers to the situation where shorter wavelengths travel faster than longer wavelengths, while anomalous dispersion occurs when longer wavelengths travel faster than shorter wavelengths.

What causes normal and anomalous dispersion?

Normal and anomalous dispersion are caused by the interaction between light and matter. In a normal dispersion, the atoms or molecules in the medium absorb and re-emit the shorter wavelengths of light more frequently, causing them to travel faster. In an anomalous dispersion, the atoms or molecules absorb and re-emit the longer wavelengths more frequently, leading to their faster travel speed.

How is normal and anomalous dispersion measured?

The degree of normal and anomalous dispersion can be measured using a device called a spectrometer, which separates light into its different wavelengths. By analyzing the resulting spectrum, scientists can determine the speed of light at different wavelengths and determine if normal or anomalous dispersion is occurring.

What are the applications of normal and anomalous dispersion?

Normal and anomalous dispersion have various applications in fields such as optics, telecommunications, and spectroscopy. For example, normal dispersion is used to create prisms and lenses that can separate white light into its component colors, while anomalous dispersion is used in devices such as fiber optic cables to compensate for differences in light speed and prevent signal distortion.

Can normal and anomalous dispersion be controlled?

Yes, normal and anomalous dispersion can be controlled by manipulating the properties of the medium through which light is passing. For example, the use of certain materials or techniques can induce normal or anomalous dispersion in a medium. This control can be important in optimizing the performance of devices that rely on dispersion, such as optical fibers.

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