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OPTICAL FIBER: DISPERSION (Types of dispersion (Modal dispersion /…
OPTICAL FIBER: DISPERSION
Dispersion
Different 'portions' of light may have different velocities while travellling along the fibre
Causing there will be time delays between the different portions : Dispersion
Resulting the pulse spreading and leads to overlapping between adjacent pulses
Effect of Dispersion
Cumulative
increasing the pulse spreading with fibre length
Overlapping causing the information error occurs
dispersion set a limit t the maximum length Lmax for a certain bit rate (BR)
Types of dispersion
Modal dispersion / Intermodal dispersion
Material dispersion
Waveguide dispersion
Polarization-mode dispersion (PMD)
Chromatic dispersion = Material + waveguide dispersion
Intramodal dispersion = CD + PMD
Modal dispersion
time delay occurs at different modes and each modes exiting the fibre at different times
1-km long fiber, light entering the fiber at the same time, but the ray will follow the longest path
theres a time delay about 15 to 30 ns per km between the lowest and highest modes
Time delay for modal dispersion:
Pulse spreading
the degree of pulse spreading in MMF depends
fibre length
the core and cladding refractive indices
Time dalay due to intermodal dispersion :
Intramodal dispersion
the magnitude of pulse spreading increase with the distance down the fibre
Chromatic dispersion
Material dispersion
Waveguide dispersion
the magnitude of the pulse spread dependent to the source linewidth
Material dispersion
the RI of the basic silica glass material of the fiber varies with the wavelength
Various wavelength components travel along at different velocities causing he propagation have the different in time delays
the output pulse from a given length of fibre seen to have spread in time relative to the input
Fabrication of OF
OVPA
VAD
PCVD
MCVD
UMMI SHOBIRAH BINTI ALI
