What is material dispersion? In which way it is helpful in optical communication?
Material dispersion is the phenomena whereby materials cause a "bundle" of light to spread out as it propagates. We know that a laser pulse, while almost monochromatic, actually contains a continuum of wavelengths in a small range. The index of refraction of a material is dependant on the wavelength, so each frequency component actually travels at a slightly different speed. As the distance increases, the pulse becomes broader as a result.
The phenomena is NOT helpful in optical communications. On the contrary, material dispersion limits how much data can be sent, as the pulses will overlap and information will be lost. Ongoing research is attempting to reduce the effects of material dispersion. Promising methods include graded-index fibers and optical temporal solitons.
Gary Russell, M.S., Systems Engineer, Reston, VA
'As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.'