An optically tunable optoelectronic oscillator (OEO) implemented by employing a two-port optical phase modulator without using any electronic microwave filters is proposed and experimentally demonstrated. The key device in the system is the two-port phase modulator, which functions, in conjunction with a dispersive element in the loop, to form a high-Q microwave filter to perform microwave frequency selection. The central frequency of the microwave filter is a function of the optical wavelength and the chromatic dispersion of the dispersive element, therefore, the oscillation frequency can be simply tuned by tuning the wavelength of the laser source or the chromatic dispersion of the dispersive element. A theoretical analysis is provided, which is verified by experiments. The phase noise performance and the frequency tunability are both experimentally investigated.
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