The fundamental mode can be launched in the multimode(MM) fibers with high accuracy by suppressing modal speckle by using broad-bandwidth excitation sources such as ultra-short pluses. As temporal coherence length of broad-bandwidth sources is very short, temporal interference between the modes and thus the presence of speckle is prevented. In this paper, single-mode(SM) excitation of step-index and graded-index multimode fibers with light sources with short temporal coherence lengths is demonstrated using a Ti:Sapphire laser with wavelengths of 790 ran and 836 nm and pulse widths of 60-90 fs. As a result, the stability of the spatial beam profile was verified by coupling the output of a MM fiber into SM fiber and SM excitation in the presence of mode-coupling for the MM fibers was confirmed by experiment.
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