A method of providing a multi-wavelength light source includes the steps of modulating an optical pulse source so as to output optical pulses with a designated repetition frequency, time-division multiplexing the optical pulses output by the optical pulse source so as to output optical pulses with a repetition frequency which is an integral multiple of the designated repetition frequency, and demultiplexing wavelengths of the optical pulses with the repetition frequency which is the integral multiple of the designated repetition frequency so as to output the wavelengths as the multi-wavelength light source.