The Temporal spreading of a pulse in an Optical Waveguide that is caused by modal or chromatic effects.

The three types of dispersion are:

• Chromatic dispersion: a frequency dependent response of material to waves.
• Modal dispersion: an optical Fiber has multiple modes at a given frequency with each Mode having a different speed.
• Waveguide dispersion: the speed of a Wave in an Optical Fiber depends on its frequency.