A Flexibly Frequency Switchable Optoelectronic Oscillator Based on a Multi-Passband Microwave Photonic Filter

In this paper, a frequency switchable optoelectronic oscillator (OEO) is proposed, which is based on a multi-passband switchable microwave photonic filter (MPF) composed of a Solc-Sagnac interferometer. By adjusting the polarization state of the Sagnac interferometer via rotating the polarization controller and the open-loop gain of the OEO loop, the signal of OEO with frequency equal to the central frequency of MPF's passbands can be oscillated. In this paper, the feasibility of the generation scheme is verified by the two frequencies that can be switched with the central frequency of 2.37 GHz and 2.87 GHz in the experiment. The effectiveness of fiber ring-assisted frequency selection is also discussed, by cascading fiber rings of different lengths in the OEO loop to achieve different side mode suppression ratio (SMSR). The longer the length of single mode fiber (SMF) in the fiber ring, the higher SMSR of OEO can be obtained.