# Frequency grid

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For [telecommunications](/source/telecommunications), a '''frequency grid''' is a table of all the central [frequencies](/source/frequency) (and corresponding [wavelength](/source/wavelength)s) of channels allowed in a [communications system](/source/communications_system).

The most common frequency grid used for [fiber-optic communication](/source/fiber-optic_communication) is that used for channel spacing in [Dense Wavelength Division Multiplexing (DWDM)](/source/wavelength-division_multiplexing) at wavelengths around 1550&nbsp;[nm](/source/Nanometre) and defined by [ITU-T](/source/ITU-T) G.694.1.<ref>ITU-T G.694.1, "Spectral grids for WDM applications: DWDM frequency grid" [http://www.itu.int/rec/T-REC-G.694.1/en ITU-T website]</ref> The grid is defined relative to 193.1&nbsp;[THz](/source/Terahertz_radiation) and extends from 191.7&nbsp;THz to 196.1&nbsp;THz with 100&nbsp;GHz spacing. While defined in frequency, the grid is often expressed in terms of wavelength, in which case it covers the wavelength range of 1528.77&nbsp;nm to 1563.86&nbsp;nm with approximately a 0.8&nbsp;nm channel spacing.

For practical purposes, the grid has been extended to cover 186&nbsp;THz to 201&nbsp;THz and subdivided to provide 50&nbsp;GHz and 25&nbsp;GHz spaced grids.

==References==
<references />

==External links==
*[http://www.telecomengineering.com/downloads/DWDM%20ITU%20Table%20-%20100%20GHz.pdf Complete ITU grid table for 100&nbsp;Ghz spacing]
*[https://web.archive.org/web/20070927225305/http://www.ntt.co.jp/tr/0306/files/ntr200306085.pdf International Standardization Activities on Optical Interfaces]

Category:Multiplexing
Category:ITU-T recommendations
Category:ITU-T G Series Recommendations
G

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