Photonic Measurement of Microwave Frequency With Low-Error based on an Optomechanical Microring Resonator

We propose and experimentally demonstrate photonic measurement of microwave frequency by utilizing an optomechanical microring resonator (MRR). The pump powers injected into the MRR would result the resonance red-shifts based on nonlinear effects. In the case of optical single sideband modulation, the frequency intervals between the optical carrier and the corresponding MRR resonance are tunable. Then microwave photonic filters with tunable central frequency could be achieved. Through using two microwave photonic filter responses with different central frequencies, an amplitude comparison function (ACF) (i.e., microwave power ratios) could be obtained. The microwave frequency could be calculated through the frequency-to-power mapping in the monotonic increasing region of the ACF. Moreover, the frequency resolution could be effectively improved by multiple measurement steps, so as to reduce the measurement errors. In the experiment, the microwave frequency could be measured from 8 to 18 GHz with errors lower than 0.035 GHz. The required highest pump power is low as -3.9 dBm. In the future, the measurement range could be largely increased by employing vector network analyzer with a larger bandwidth. The significant optomechanical device and measurement method are competent to measure microwave frequency with dominant advantages, such as all-optical control, compact footprint, low-error, and low-power consumption.