Microwave frequency measurement based on dual optical frequency combs and stimulated Brillouin scattering

A novel high-accuracy microwave frequency measurement based on dual coherent optical frequency combs and stimulated Brillouin scattering was investigated. The unknown microwave signal and the sweep signal were modulated by two dual parallel Mach-Zehnder modulators as the signal optical and the pump signal which were lunched into the dispersion shift fiber. Using dual optical frequency combs and the sweep signal with shifted frequencies, the proposed measurement system could realize the wave-division and time-division multiplexing simultaneously. At the same time, the action of dual optical frequency combs and stimulated Brillouin scattering brought the system a series of stimulated Brillouin scattering. The frequency of the unknown signal was estimated by measuring the output optical power of the multiple channels. Furthermore, in order to improve the frequency measurement accuracy, the measured optical power values were employed to generate an amplitude comparison function which can be utilized for error correction. The effectiveness of the proposed scheme is verified via numerical simulations with a measurement error at ±2.5 MHz.