We present an all-fiber Michelson interferometer based repetition-rate stabilization of mode-locked lasers for ultralow noise microwave generation. The absolute rms timing jitter of pulse trains is suppressed down to 1.4 fs over 1 s when a 10-km-long fiber interferometer is employed. The absolute timing jitter of the generated 10 GHz microwave is 7.6 fs over 0.1 s when a 1-km-long fiber interferometer is used.