Real-Time and High-Accuracy Microwave Frequency Identification Based on Ultra-Wideband Optical Chirp Chain Transient SBS Effect

The use of stimulated Brillouin scattering (SBS) for microwave photonics frequency measurement is widely studied because of its unique advantage of high accuracy. However, the technique's slow response severely limits its use for real-time applications. To solve this problem, this work proposes and demonstrates the use of an ultra-wideband optical chirp chain (OCC) transient SBS effect to avoid the need to slowly frequency sweep the Brillouin spectrum. This innovation enables real-time and high-accuracy microwave frequency identification. It is shown that real-time microwave tracking can be achieved by continuously repeating the OCC-modulated wave, which allows for wide-range frequency sweeping over a very short time. High accuracy is achieved by exploiting the narrow bandwidth characteristic of the transient Brillouin spectrum. In the experiments, the temporal resolution is 100 ns for the time-varying frequency microwave identification, enabled by the transient SBS effect, representing at least three orders of magnitude improvement over previously reported SBS-based methods. The frequency measurement is accurate to 1 MHz. In addition, several further benefits, such as resolving multifrequency signals, reconfigurable instantaneous bandwidth, and 20 GHz frequency measurement range, are demonstrated.