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. km at 850 nm are now commonly manufactured for use in 10 Gbit/s data links.However, multimode graded-index fibers having bandwidths exceeding 3.5 GHz Modal dispersion may be considerably reduced, but never completely eliminated, by the use of a core having a graded refractive index profile. 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 Modal dispersion limits the bandwidth of multimode fibers. The arrival of different components of the signal at different times distorts the shape. 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). Rays of light enter the fiber with different angles to the fiber axis, up to the fiber's acceptance angle. In the ray optics analogy, modal dispersion in a step-index optical fiber may be compared to multipath propagation of a radio signal. Other names for this phenomenon include multimode distortion, multimode dispersion, modal distortion, intermodal distortion, intermodal dispersion, and intermodal delay distortion. 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.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |