Multiple microwave waveform generation by a dual-loop optoelectronic oscillator

A self-starting multiple microwave waveform signal generator based on a dual-loop optoelectronic oscillator (OEO) is proposed. The structure of the dual-loop OEO with two wavelengths can suppress the random beating noise effectively and generate the microwave signal with low phase noise (−119.8 dBc/Hz at 10 kHz). Then square waveform is generated by setting the modulation index to be 1.15. Sawtooth (Reversed-sawtooth) waveform is obtained by combining a square and a frequency doubling sinusoidal signal which is got by setting the bias of the other MZM driven by OEO at the null point (maximum point). The triangular waveform is obtained by combining two oscillation signal envelopes with a relative 1/4 period time delay, when the modulation index of the MZM is set to 0.7555. The operation principle is theoretically analyzed and simulated. In experimental demonstration, full-duty-cycle and high quality square, sawtooth (reversed-sawtooth) and triangular waveform signals with low phase noise at 4.9641-GHz are achieved. An external synthesizer is replaced by the high-quality microwave signal in this structure.