Accurate measurement of time delay of broadband microwave signal via high-repetition-rate pulse train probing SBS based all-optical pulse compression

Abstract

We demonstrate a novel scheme to determine the absolute time delay of an unknown signal in an all-optical pulse compression system based on stimulated Brillouin scattering (SBS). Optical pulse train with high repetition rate is utilized as the probe lightwave and unknown broadband microwave signal is modulated on the pump lightwave. The pump and probe lightwaves interact along an optical fiber via SBS. The finite optical fiber length and high pulse repetition rate of probe signal make SBS insufficient since the first several probe pulses meet a part of the entire pump signal. The absolute time delay of the unknown microwave signal is determined through the amplitude variations of the pulse compression results, which are intrinsically carried by the probe pulses suffering insufficient SBS gain. The measurement of the absolute time delay is theoretically analyzed and is experimentally demonstrated. The maximum experimental error is about 7 ns for a linearly frequency-modulated pulse with 1 GHz sweep range at the center frequency of 10 GHz.