40GHz optoelectronic oscillator with low-frequency optical and microwave devices

A high frequency optoelectronic oscillator (OEO) using only low frequency optical and microwave devices is attractive as it provides a low cost and high quality solution at the same time. In this paper, a novel OEO scheme is reported. The proposed optoelectronic oscillator includes a 5GHz directly modulated DFB laser, an optical circulator, a 10GHz photodetector, a 10GHz RF amplifier, and a bandpass RF filter with a central frequency at 5GHz. The OEO oscillates at the 5GHz and with a continuous wave injected into the directly modulated DFB laser, higher harmonics will be generated. The harmonic order can be controlled by the frequency difference between the free running DFB laser and injection lightwave. An optical domain combined dual-loop configuration with polarization-beam splitter and a polarization-beam combiner is employed to suppress the sidemodes in each single loop. Experiment results are proposed to verify the scheme, in which 40GHz microwave is obtained.