A wideband-tunable optoelectronic oscillator (OEO) is proposed and experimentally demonstrated based on a tunable microwave photonic filter (MPF) consisting of a polarization modulator, a chirped fiber Bragg grating, and a polarization beam splitter (PBS). By simply adjusting the polarization state of the signal before the PBS, the center frequency of the MPF is tuned. The proposed OEO is experimentally demonstrated. A high-purity microwave signal with a tunable frequency within 5.8-11.8 GHz is generated. The single-sideband phase noise of the generated signal is −104.56 dBc/Hz at 10-kHz offset.

A novel approach to generating an ultraflat and stable optical frequency comb with tunable frequency spacing is proposed and experimentally demonstrated. The proposed generator consists of a polarization modulator (PolM) and a polarizer. The joint operation of a PolM and a polarizer is equivalent to intensity modulation, but with a third controllable parameter in addition to the two controllable parameters in conventional intensity modulation. By tuning the three parameters, an ultraflat optical frequency comb with five comb lines is generated. By cascading the PolM with a second PolM, an ultra-flat optical frequency comb with 25 lines is generated. An experiment using two cascaded PolMs is performed. A 25- line frequency comb with the comb flatness within 1 dB is generated.

Purpose This paper aims to classify the inductorless Chua’s circuits into two types from the topological structures and construct a chaotic circuit under this new classification framework. Design/methodology/approach In this paper, two types of inductorless Chua’s circuit models are presented from topological structure, among which the first type of inductorless Chua’s circuit (FTICC) model is much closer to the original Chua’s circuit. Under this classification framework, a new inductorless Chua’s circuit that belongs to the FTICC model is built by replacing LC parallel resonance of the original Chua’s circuit with a second order Sallen–Key band pass filter. Findings Compared with a paradigm of a reported inductorless Chua’s circuit that belongs to the second type of inductorless Chua’s circuit (STICC) model, the newly proposed circuit can present the attractors which are much more closely to the original Chua’s attractors. The dynamical behaviors of coexisting period-doubling bifurcation patterns and boundary crisis are discovered in the newly proposed circuit from both numerical simulations and experimental measurements. Moreover, a crisis scenario is observed that unmixed pairs of symmetric coexisting limit cycles with period-3 traverse through the entire parameter interval between coexisting single-scroll chaotic attractors and double-scroll chaotic attractor. Originality/value The newly constructed circuit enriches the family of inductorless Chua’s circuits, and its simple topology with small printed circuit board size facilitates the various types of engineering applications based on chaos.

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