We demonstrate an all-optical scheme to multiply the repetition frequency of a high-rate optical pulse train by using a spectral filter to remove unwanted frequency components. A stable 58.5-GHz soliton pulse source at 1542 nm is filtered with a Fabry-Perot interferometer to achieve 117 and 175.5 GHz output pulse trains. This scheme is generally applicable to rate multiplication of mode-locked pulse trains using various types of spectral filters. All-optical rate conversion of continuous pulse trains may find applications in time division multiplexed optical networks at high bit rates, where electronic methods are cumbersome.