nolldispersionen

Nolldispersionen is a term used in optics to describe conditions under which chromatic dispersion is effectively zero. Dispersion is the dependence of a medium’s refractive index on wavelength, which causes different spectral components of a light pulse to travel at different speeds and can broaden the pulse over distance. Nolldispersionen therefore refers to regimes or designs where this spreading is minimized or canceled for a range of wavelengths.

In optical fibers, the zero-dispersion wavelength (ZDW) is the wavelength at which the material and waveguide dispersions cancel, making the second derivative of the propagation constant with respect to angular frequency vanish. In standard silica fibers the ZDW lies near 1.3 micrometers, and designers can shift it through fiber design (core, cladding, or photonic-crystal structures) so that it aligns with telecommunications windows around 1.55 micrometers. Operating near the ZDW reduces linear pulse broadening, benefiting ultrafast and high-bandwidth applications; however, higher-order dispersion and nonlinear effects remain.

Nolldispersionen can also be pursued through dispersion-compensation strategies, such as dispersion-compensating fibers, fiber Bragg gratings, or carefully engineered multi-material waveguides. The concept relies on understanding and balancing the wavelength dependence of the refractive index and the waveguide geometry, often described by the Sellmeier equation for n(λ) and by the dispersion parameter β2(λ).

While zero dispersion is a useful design goal, it is rarely perfect across broad spectral ranges or changing operating conditions. In practice, engineers aim for minimal dispersion over the intended band and use compensation techniques to manage residual effects.