group velocity

Group velocity refers to the travel times oflight with different wavelengths.

Since light waves or infrared rays are not monochromatic, i.e. consist of several frequencies or wavelengths, their propagation in an optical waveguide is also different. They propagate at different speeds in the transmission medium and can even overlap or even mutually cancel each other out. In extreme cases, these superpositions mean that the signal can no longer be evaluated at the receiving location. For this reason, the group velocity is an important measure for optical waveguides.