roadening in large core step-index optical fibers is dominated by multimode dispersion. The bandwidth of PMMA core polymer optical fiber depends on launch conditions, being substantially greater for collimated input than for mode-filled launching. The dispersion behavior is significantly affected by both mode dependent attenuation and by power coupling between modes. The results of time-domain dispersion measurements performed at 650 nm are presented and examined. The effects of launching conditions and fiber numerical aperture on bandwidth are discussed. Mode conversion is studied by examining far-field output patterns under various launch conditions. Disturbances caused by sharp bends, splices, and couplers can modify the distribution of energy among modes and thus effect the dispersion. Because only the propagation after the disturbance is effected, a given fiber optic link can have different effective bandwidths in the two counter propagating directions. Finally, a method of realizing higher effective bandwidth over a given fiber by mode-selective detection is presented.
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