Dispersion Shifted Fiber 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 includes 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. Dispersion-shifted fiber is specified in
ITU-T G.653. ==References==