The term dispersion describes all effects that lead to impulse broadening or flattening during its propagation along an optical fiber. This may lead to increasing overlapping of neighboring impulses. The receiver cannot distinguish the separate impulses, as shown in figure 11. Transmission errors are the result. The most common types of dispersion are mode dispersion and chromatic dispersion, which, again, consists of material dispersion and wave-guide dispersion.
The bandwidth-length product (BLP) is a figure indicating the quality of an optical transmission system. It describes which bandwidth can be transmitted over a certain distance. The BLP is always specified for a length of 1 kilometer. Therefore, a BLP of 500MHz*km means that a bandwidth of 500MHz can be reached for a link length of 1 km, but only 250MHz for 2 km and 1000MHz for 500 meters. Due to the high quality of single mode fibers, this value will normally not be specified in favor of the attenuation values. The BLP of a Multimode OM4 fiber is 4700 MHz*km at a wavelength of 850nm.