Singledispersion

Singledispersion, sometimes written single-dispersion, is an informal term used in optics and signal processing to describe a regime in which dispersion is governed predominantly by a single mechanism or a single dispersion coefficient across the operational bandwidth. In common linear-optical analysis, the propagation constant β(ω) is expanded around a center frequency ω0 as β(ω) = β0 + β1(ω−ω0) + 0.5 β2(ω−ω0)^2 + 1/6 β3(ω−ω0)^3 + ...; singledispersion typically retains only β1 and β2, neglecting higher-order terms such as β3, so the phase response is approximately quadratic over the band.

This simplification implies that pulse evolution is dominated by second-order group-velocity dispersion (GVD) with little contribution from third- or higher-order dispersion. Consequently, pulse broadening can be predicted from β2 and the propagation length, and compensation strategies focus on cancelling that dominant β2-term using dispersive elements or fibers tuned to the same sign and magnitude of dispersion.

Limitations include the breakdown of the approximation for wide bandwidths or when higher-order dispersion or wavelength-dependent dispersion cannot be neglected. Real systems also exhibit nonlinearity and multimode effects that violate the single-dispersion assumption.

Applications are most common in short-reach fiber-optic links, certain ultrafast-pulse experiments, and optical-imaging systems where a single, relatively constant dispersion behavior suffices for analysis and design. See also chromatic dispersion, group-velocity dispersion, dispersion compensating techniques.