Thanks for sharing this article here about the fiber optic technology. Your article is very informative and I will share it with my other friends as the information is really very useful. Keep sharing your excellent work. Dispersion in optical fibres Broadening of the transmitted light pulses take place as the light rays move along the optical fibre. This broadening of light pulses is known as dispersion.
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The types are intramodal and intermodal dispersion. Intramodal, or chromatic, dispersion occurs in all types of fibers. Intermodal, or modal, dispersion occurs only in multimode fibers. Each type of dispersion mechanism leads to pulse spreading. As a pulse spreads, energy is overlapped. This condition is shown in figure The spreading of the optical pulse as it travels along the fiber limits the information capacity of the fiber.
Intramodal, or chromatic, dispersion depends primarily on fiber materials. There are two types of intramodal dispersion. The first type is material dispersion. The second type is waveguide dispersion. Intramodal dispersion occurs because different colors of light travel through different materials and different waveguide structures at different speeds.
Material dispersion occurs because the spreading of a light pulse is dependent on the wavelengths' interaction with the refractive index of the fiber core. Different wavelengths travel at different speeds in the fiber material. Different wavelengths of a light pulse that enter a fiber at one time exit the fiber at different times. Material dispersion is a function of the source spectral width. The spectral width specifies the range of wavelengths that can propagate in the fiber. Material dispersion is less at longer wavelengths.
Waveguide dispersion also occurs because light propagates differently in the core than in the cladding. In multimode fibers, waveguide dispersion and material dispersion are basically separate properties. Multimode waveguide dispersion is generally small compared to material dispersion. Waveguide dispersion is usually neglected.
However, in single mode fibers, material and waveguide dispersion are interrelated. The total dispersion present in single mode fibers may be minimized by trading material and waveguide properties depending on the wavelength of operation.
Intermodal or modal dispersion causes the input light pulse to spread. The input light pulse is made up of a group of modes. As the modes propagate along the fiber, light energy distributed among the modes is delayed by different amounts. The pulse spreads because each mode propagates along the fiber at different speeds.
Since modes travel in different directions, some modes travel longer distances. Modal dispersion occurs because each mode travels a different distance over the same time span, as shown in figure The modes of a light pulse that enter the fiber at one time exit the fiber a different times. This condition causes the light pulse to spread.
As the length of the fiber increases, modal dispersion increases. Modal dispersion is the dominant source of dispersion in multimode fibers. Modal dispersion does not exist in single mode fibers. Single mode fibers propagate only the fundamental mode. Therefore, single mode fibers exhibit the lowest amount of total dispersion. Single mode fibers also exhibit the highest possible bandwidth.
What is this condition called? Attenuation Introduction to Fiber Optics Summary. Custom Search. Figure Intramodal Dispersion Intramodal, or chromatic, dispersion depends primarily on fiber materials.
Intermodal Dispersion Intermodal or modal dispersion causes the input light pulse to spread.
Login Now. Dispersion is the broadening of actual time-width of the pulse due to material properties and imperfections. As pulse travels down the fiber, dispersion causes pulse spreading. This limits the distance travelled by the pulse and the bit rate of data on optical fiber. Pulse broadening within a single mode is called as intramodal dispersion or chromatic dispersion. Since this phenomenon is wavelength dependent and group velocity is a function of wavelength, it is also called as group velocity dispersion GVD.
The types are intramodal and intermodal dispersion. Intramodal, or chromatic, dispersion occurs in all types of fibers. Intermodal, or modal, dispersion occurs only in multimode fibers. Each type of dispersion mechanism leads to pulse spreading. As a pulse spreads, energy is overlapped. This condition is shown in figure
In fiber-optic communication , an intramodal dispersion , is a category of dispersion that occurs within a single mode optical fiber. Two distinct types of intramodal dispersion are: chromatic dispersion and polarization mode dispersion. In silica, the index of refraction is dependent upon wavelength. Therefore different wavelengths will travel down an optical fiber at different velocities. This dispersion limits both the bandwidth and the distance over which the information can be transmitted. This is why for long communications links, it is desirable to use a laser with a very narrow linewidth.