A time-multiplexed waveform generator includes a wavelength splitter that receives an input optical signal and spectrally separates the input optical signal into a plurality of frequency components. A plurality of intensity modulators receives each of the frequency components and passes each of the frequency components for a selective time period, and then extinguishes that frequency for the remainder of a chirp time, the plurality of intensity modulators producing a plurality of first output signals. A plurality of adjustable delay lines is positioned after the intensity modulators and receives the first output signals. Each of the adjustable delay lines enables phase control of each of the frequency components associated with the first output signals for compensating any relative drifts of the path lengths and phase coherently stitching a plurality of sub-chirps together. The adjustable delay lines produce a plurality of second output signals. A wavelength combiner receives the second output signals and recombines the output signals to produce a stair-step waveform output signal.