Flexible RF-Based Comb Generator

A comb generator based on feeding a single dual drive Mach–Zehnder modulator with a sinusoidal radio frequency (RF) at one arm and its double frequency at the other arm is demonstrated. Our comb generator benefits from the superposition of optical subcarriers generated by the fundamental and its second harmonic. We demonstrate flexibility in center wavelength tunability, subcarrier spacing, and subcarrier count. For a fundamental frequency at, e.g., 6.25 GHz, our comb generator can produce 9, 5, 4, or 3 optical subcarriers with a spectral flatness of ${< }{\rm 1.2}~{\rm dB}$ . We successfully demonstrate to the best of our knowledge, the generation of the largest number of comblines requiring the lowest drive signal with the least components within the field of RF-generated combs.