Fibre dispersion-Material,Modal,Waveguide dispersion types
This page describes basics of fibre dispersion. It mentions types of dispersion viz. material dispersion, modal dispersion and waveguide dispersion.
Dispersion is the result of spreading of pulse of light when it is transmitted through the optic fibre cable. When the pulse (say 'A') is transmitted on fibre, it becomes longer. It will join with the pulse which is behind this pulse-'A'.
Due to above, recovery of bit stream will become difficult.
In digital optic communication '1' is represented as "light" and
'0' is represented as "no light" or "dark".
In analog optic communication, information is transmitted as continuous series of changes in the analog signal. Hence in analog communication, dispersion results into distortion.
There are different types of dispertion. Following are the important dispersion types, which include material dispersion, Modal dispersion and waveguide dispersion.
This dispersion type is result of material property which is refractive index of fibre. Different fibre will have different refractive indexes. This will result into different wavelengths of light will travel at different speeds in the different types of fibre. As result of this, some pulses of wavelengths will arrive before other pulses. Hence signal pulse disperses or smears out.
This dispersion type is result of different modes of fibre cable. The light travel through different paths in different modes. Hence in different modes, light will have different travel distances. This will cause dispersion.
This is caused by shape and index profile of fibre core. This can be controlled using proper design. This dispersion type helps counteract effect of material dispersion type explained above.
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