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Dispersion-shifted fiber

 
Computer Desktop Encyclopedia: dispersion-shifted fiber

A singlemode optical fiber that has been designed to reduce chromatic dispersion. The fiber core is fabricated in several layers with different refractive indices running in parallel throughout its length. Zero-dispersion-shifted fiber has zero chromatic dispersion at 1550 nm. It is no longer manufactured, because it causes interference in WDM transmission. Nonzero-dispersion-shifted fiber is designed for WDM. It has zero dispersion near 1500 nm and beyond 1600 nm, which provides lower dispersion in the 1550 nm range. See graded-index fiber, step index fiber and dispersion.

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Wikipedia: Dispersion-shifted fiber
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Dispersion-shifted fiber (DSF), specified in ITU-T G.653, is a type of single-mode optical fiber with a core-clad index profile tailored to shift the zero-dispersion wavelength from the natural 1300 nm in silica-glass fibers to the minimum-loss window at 1550 nm. The group-velocity or intramodal dispersion which dominates in single-mode fibers is comprised of both material and waveguide dispersion. Waveguide dispersion can be made more negative by changing the index profile and thus be used to offset the fixed material dispersion, shifting or flattening the overall intramodal dispersion. This is advantageous because it allows a communication system to possess both low dispersion and low attenuation. However, when used in wavelength division multiplexing systems, dispersion-shifted fibers can suffer from four-wave mixing which causes intermodulation of the independent signals. As a result nonzero dispersion shifted fiber is often used.

References

  • L.G. Cohen, C. Lin, and W. G. French, Electron. Lett., 15, 334 (1979).

 
 
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step-index fiber (technology)
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