Self-sustained Optical Frequency Combs Generation with a Tunable Line Spacing Based on Coupled Optoelectronic Oscillators

An optical frequency comb (OFC) generator based on a coupled optoelectronic oscillator (COEO) is demonstrated. It consists of a mode-locked ring laser and an optoelectronic feedback loop. The line spacing of the generated OFC is adjustable by only tuning the center frequency of the electrical bandpass filter in the optoelectronic loop. In the experiments, two OFCs with a spacing of 8 GHz and 10 GHz are respectively produced. The phase noise of the self-oscillating signal corresponding to the two spectra is -79.5dBc/Hz and - 75.8dBc/Hz @10KHz offset frequency, respectively.