Dispersion in optical fibers refers to the spreading of these light pulses as they travel. Understanding dispersion is crucial for optimizing fiber-optic. Polarization Mode Dispersion Polarization mode dispersion (PMD) represents the polarization dependence of the propagation characteristics of light waves in optical fibers. Such spreading arises from differential mode delay in multimode fibers and material dispersion in both single-mode and multimode fibers. As a pulse of light propagates through a fiber, elements such as numerical aperture, core diameter, refractive index profile, wavelength, and laser line width cause the pulse to broaden.