A tunable comb generator may include a light source to generate an optical signal, an intensity modulator to modulate an intensity of the optical signal from the light source based on a RF drive signal, a frequency-locking loop (FLL) to maintain an optical frequency of the optical signal received from the intensity modulator at a target optical frequency corresponding to a resonance frequency of a periodic optical filter in the FLL, and an optoelectronic oscillator (OEO) loop. The OEO loop may include a photodetector to generate the RF drive signal based on the optical signal from the FLL, a tunable phase shifter to select a resonance frequency of the OEO loop corresponding to a harmonic of the resonance frequency of the periodic optical filter, and one or more phase modulators to generate an optical comb signal by modulating a portion of the optical signal from the FLL.