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- Modal_dispersion abstract "Modal dispersion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because the propagation velocity of the optical signal is not the same for all modes. Other names for this phenomenon include multimode distortion, multimode dispersion, modal distortion, intermodal distortion, intermodal dispersion, and intermodal delay distortion.In the ray optics analogy, modal dispersion in a step-index optical fiber may be compared to multipath propagation of a radio signal. Rays of light enter the fiber with different angles to the fiber axis, up to the fiber's acceptance angle. Rays that enter with a shallower angle travel by a more direct path, and arrive sooner than rays that enter at a steeper angle (which reflect many more times off the boundaries of the core as they travel the length of the fiber). The arrival of different components of the signal at different times distorts the shape. Modal dispersion limits the bandwidth of multimode fibers. For example, a typical step-index fiber with a 50 µm core would be limited to approximately 20 MHz for a one kilometer length, in other words, a bandwidth of 20 MHz·km. Modal dispersion may be considerably reduced, but never completely eliminated, by the use of a core having a graded refractive index profile. However, multimode graded-index fibers having bandwidths exceeding 3.5 GHz·km at 850 nm are now commonly manufactured for use in 10 Gbit/s data links. Modal dispersion should not be confused with chromatic dispersion, a distortion that results due to the differences in propagation velocity of different wavelengths of light. Modal dispersion occurs even with an ideal, monochromatic light source. A special case of modal dispersion is polarization mode dispersion (PMD), a fiber dispersion phenomenon usually associated with single-mode fibers. PMD results when two modes that normally travel at the same speed due to fiber core geometric and stress symmetry (for example, two orthogonal polarizations in a waveguide of circular or square cross-section), travel at different speeds due to random imperfections that break the symmetry.".
- Modal_dispersion wikiPageExternalLink modal_dispersion.
- Modal_dispersion wikiPageExternalLink definition.aspx?id=3772.
- Modal_dispersion wikiPageID "7705960".
- Modal_dispersion wikiPageRevisionID "601486302".
- Modal_dispersion hasPhotoCollection Modal_dispersion.
- Modal_dispersion subject Category:Fiber_optics.
- Modal_dispersion subject Category:Telecommunications_engineering.
- Modal_dispersion type BodyPart105220461.
- Modal_dispersion type Eye105311054.
- Modal_dispersion type FiberOptics.
- Modal_dispersion type Organ105297523.
- Modal_dispersion type Part109385911.
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- Modal_dispersion comment "Modal dispersion is a distortion mechanism occurring in multimode fibers and other waveguides, in which the signal is spread in time because the propagation velocity of the optical signal is not the same for all modes.".
- Modal_dispersion label "Dispersion intermodale".
- Modal_dispersion label "Modal dispersion".
- Modal_dispersion sameAs Dispersion_intermodale.
- Modal_dispersion sameAs m.0269fzp.
- Modal_dispersion sameAs Q3030551.
- Modal_dispersion sameAs Q3030551.
- Modal_dispersion sameAs Modal_dispersion.
- Modal_dispersion wasDerivedFrom Modal_dispersion?oldid=601486302.
- Modal_dispersion isPrimaryTopicOf Modal_dispersion.