To provide an optical transmitter for generating a modulation light signal of a plurality of wavelengths by using wavelength sweep light, which suppresses interference of an adjacent channel with a simple configuration and to provide an optical communication system.

The optical transmitter 51 includes a wavelength sweep light source 11 for outputting an optical signal for sweeping a prescribed wavelength range in a prescribed repetition frequency, an optical modulator 12 for modulating an output optical signal of the wavelength sweep light source 11 with data obtained by multiplexing transmission data corresponding to each wavelength channel on a time base, and an optical filter 14 having a cyclic passing characteristic corresponding to a channel interval of each wavelength channel in order to filter a modulation optical signal corresponding to each wavelength channel output from the optical modulator 12.