dispersion in optical FIBER:-

Dispersion is splitting of white light in to its components color which results in to broadening of light and this is known as dispersion of light.
Due to broadening of pulses there can be overlapping of adjacent pulses which results into ISI and increases in BER.
Let the pulse width is Tau(T), Hence in order to avoid dispersion or BER due to dispersion, Bit Rate<= 1/2T
As the length of the fiber increases the propagation delay between the spectral components and different models also increases. Hence, Pulse broadening depends on transmission distance or length of the fiber.
The dispersive properties of the fiber are defined by the band width length product which is constant for a particular fiber. BW*L=Constant ↑ Dispersion ∝ Length ↑ → T(Tau)
NOTE:-Dispersion reduces the Capacity, Bandwidth, Bit rate and the Range of the fiber and increases the ISI and number of errors.
NOTE:-The maximum allowance pulse broadening is equal to the pulse width of original pulse i.e “T(Tau)” .