The chromatic dispersion( CD) is composed of the material dispersion and the waveguide dispersion and leads to a wavelength and path length dependent broadening of the optical pulses in an optical fiber.
This broadening is given in (ps/nm/km) and is specified in ITU Recommendation G.652. The Optical Internetworking Forum( OIF) recommends maximum values of 2000 ps/nm/km for short distances and up to 40,000 ps/nm/km for long distances. Shifts of several picoseconds occur per kilometer of fiber length, adding up to several nanometers of wavelength difference.
The coefficient of waveguide dispersion is always negative and that of material dispersion increases with increasing wavelength. Under these conditions it is possible to compensate the chromatic dispersion. To reduce chromatic dispersion, the dispersion zero-crossing of optical fibers is shifted or the dispersion curve is flattened. Examples of such monomode fibers are the DSF fiber (Dispersion Shifted Fiber), NDSF fiber ( Non Dispersion Shifted Fiber) and the NZDSF fiber (Non Zero Dispersion Shifted Fiber).