Fiber Optic - Dispersion

1403 Words6 Pages
DISPERSION There are two different types of dispersion in optical fibers. Each type of dispersion mechanism leads to pulse spreading. As a pulse spreads, energy is overlapped. The spreading of the optical pulse as it travels along the fiber limits the information capacity of the fiber. a. intramodal b. intermodal dispersion Intramodal (chromatic, dispersion) 1. occurs in all types of fibers and depends primarily on fiber materials. 2. There are two types of intramodal dispersion. * material dispersion * waveguide dispersion. 3. occurs because different colors of light travel through different materials and different waveguide structures at different speeds. Material dispersion 1. Occurs because the spreading of a light pulse is dependent on the wavelengths' interaction with the refractive index of the fiber core. 2. Different wavelengths travel at different speeds in the fiber material. 3. Different wavelengths of a light pulse that enter a fiber at one time exit the fiber at different times. (diff rays of light enter fiber but will exit at diff times) 4. Material dispersion is a function of the source spectral width. 5. The spectral width specifies the range of wavelengths that can propagate in the fiber. 6. Material dispersion is less at longer wavelengths. Waveguide dispersion 1. Occurs because the mode propagation constant (β)is a function of the size of the fiber's core relative to the wavelength of operation. 2. 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

More about Fiber Optic - Dispersion

Open Document