The sweep rate, sweep range, and coherence length of swept sources, respectively, determine the acquisition rate, axial resolution, and imaging range of optical coherence tomography (OCT). In this paper, we demonstrate a reconfigurable high-speed and broadband swept laser by time stretching of a flat spectrum femtosecond pulse train with over 100 nm bandwidth and a repetition rate of 100 MHz. By incorporating an optical modulator and utilizing appropriate dispersive modules, the reconfiguration of the swept source is demonstrated with sweep rates of 25 and 2.5 MHz. The 2.5 MHz swept source enables an imaging range of >110mm with 6 dB sensitivity roll-off in OCT, which is the longest imaging range ever reported for megahertz OCT.