Frequency-Stabilized Optoelectronic Oscillator With Simultaneous Wideband Tunability

The continuous exploration and development of photonics on chip (PoC) has been paving the way for integrated optoelectronic oscillators (OEOs), which can significantly reduce the size, weight, and power consumption. The microring resonator (MRR) plays an important role in integrated OEOs because of its high quality factor and wideband tunability. However, the resonant wavelength of on-chip MRR is highly sensitive to environmental fluctuation, which severely degrade the stability of OEO. Here, we propose and experimentally demonstrate a frequency-stabilized OEO with simultaneous wideband tunability. A high-Q silicon nitride MRR is designed and employed as a tunable microwave photonic bandpass filter (MPBF) for mode selection. Meanwhile, a frequency offset correction (FOC) circuit is used to monitor the output frequency of the OEO and provide a control signal for tuning the resonant wavelength of the MRR. Experimental results show that the oscillation frequency of the proposed OEO is tuned from 4 to 12 GHz while maintaining frequency stability at each oscillation frequency. When the oscillation frequency is 10 GHz, the frequency drift is reduced from 586.9 MHz to no more than 40 kHz in 1 h, and the Allan deviation is improved from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.04\times 10^{-2}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.35\times 10^{-12}$ </tex-math></inline-formula> in an averaging time of 1000 s. Meanwhile, the frequency locking range of the proposed OEO can reach up to 200 MHz. The proposed approach provides strong support for further monolithic integration of OEO, which can be potentially applied to radar, sensing systems, and wireless communications.