Tunable optoelectronic oscillator based on a polarization-dependent phase modulator cascaded with a linear chirped FBG

Abstract A tunable optoelectronic oscillator (OEO) based on polarization controlled frequency response shifting of a dispersion-induced microwave photonic filter (MPF) is proposed and experimentally demonstrated. The MPF consists of a phase modulator (PM), a linear chirped fiber Bragg grating (LCFBG), and polarization multiplexed dual loops. Thanks to the polarization properties of the LiNbO 3 crystal, the center frequency of the MPF can be tuned by simply adjusting the polarization state of the optical signal, and a tunable optoelectronic oscillator is established. Compared to the previous structure, the expensive wavelength-tunable laser is not needed in the proposed structure. In addition, the instability of oscillation frequency caused by the bias drifts of the modulator is avoided. A pure oscillation signal with a tunable frequency range from 3.3 to 7.3 GHz is generated. The single-sideband phase noise of the oscillation signal is about −110 dBc/Hz at 10-kHz offset. During more than 30 min observation, the oscillation frequency drift is about 7 kHz.