In optical Fiber communication, the Wavelength dependence of the velocity of propagation (of the optical signal) on the bulk material of which the fiber is made.

Note 1: Because every optical signal has a finite spectral width, material Dispersion results in spreading of the signal. Note 2: Use of the redundant term “chromatic dispersion” is discouraged. Note 3: In pure silica, the basic material from which the most common telecommunication-grade fibers are made, material dispersion is minimum at wavelengths in the vicinity of 1.27 um (slightly longer in practical fibers).