Effect of fiber dispersion on pulse width

In order to study the influence of dispersion on the information transfer capacity of the communication system,the mechanism of all kinds of dispersion for single-mode and multimode fibers,such as polarization mode dispersion,material dispersion,wave leading dispersion and mode dispersion,was studied by means of simulation.The expanded pulse width induced by dispersion in standard fibers whose refractive index n=1.516 and n=1.458 respectively was obtained after propagating 10km distance.The dispersion effect for multimode fibers with the propagation wavelength as 850nm and 1310nm respectively was compared.The effect of the spectrum width of the different laser sources,such as LD(Δλ=1nm) and LED(Δλ=70nm),on the pulse width was compared.It shows that the group velocity dispersion group velocity dispersion is 0 when the propagation wavelength of the system is 1.27μm for a pure silica fiber,the intra-modal dispersion becomes abnormal dispersion when the graded-index multimode fiber is in the propagation window of 850nm or 1310nm and that the expanded pulse width induced by the chromatic dispersion and modal dispersion would increase with the numerical aperture,refractive index and the spectrum width of the laser source.