Simultaneous Triangular Waveform Signal and Microwave Signal Generation Based on Dual-Loop Optoelectronic Oscillator

Abstract

A self-starting triangular waveform and microwave signal generator based on a dual-loop optoelectronic oscillator (OEO) is proposed. In this scheme, two continuous waves (CWs) with different wavelength are emitted from two laser diodes (LDs) to form two feedback loops in an OEO system. When the oscillation is established and the modulation index of the Mach–Zehnder modulator (MZM) is set to be 0.752, a triangular waveform could be generated by the superposition of the two oscillation signal envelopes on photodetector with appropriate time delay between two wavelength channels. Although the proposed system is similar to a traditional dual-loop OEO and no more devices are required, it is not only a microwave signal source with high side-mode suppression ratio (SMSR) but a triangular waveform generator simultaneously as well. The operation principle is theoretically analyzed and stimulated. In experimental demonstration, the full-duty-cycle triangular waveform signal and high-quality microwave signal at 5 GHz can be achieved simultaneously. In addition, the experiment result shows that the variety of the modulation depth for triangular waveform generation does not influence the quality of the generated microwave signal.