Group Velocity

The speed at which a particular wave front or swell train advances.

The velocity of propagation of an envelope produced when an electromagnetic wave is modulated by, or mixed with, other waves of different frequencies. Note: The group velocity is the velocity of information propagation and, loosely, of energy propagation. 2. In optical fiber transmission, for a particular mode, the reciprocal of the rate of change of the phase constant with respect to angular frequency. Note: The group velocity equals the phase velocity if the phase constant is a linear function of the angular frequency, = 2f, where f is the frequency. 3. In optical-fiber transmission, the velocity of the modulated optical power.