Length dependence of pulse dispersion in a long multimode optical fiber

Shuttle pulse measurements performed on a 1280-m long multimode optical fiber were used to determine pulse dispersion along a 6400-m extrapolated length. The fiber's steady-state mode coupling length was determined without breaking the fiber. The impulse responses for one, three, and five trips through the fiber were recorded and Fourier transformed to yield the corresponding baseband frequency responses. It was concluded that the coupling length was approximately 840 m, and that the impulse response became increasingly more symmetrical for fiber lengths beyond this coupling length. This agrees with theory.