Timing jitter and linewidth measurement of optical frequency combs based on Brillouin amplification of single comb line

Accurate characterizations of timing jitter spectra and comb mode linewidth of optical frequency combs (OFCs) are of great significance for their ever-growing applications with low noise requirements. We demonstrate a method for OFC's timing jitter and linewidth measurement, which combines Brillouin selective amplification of individual comb lines with delayed self-heterodyne method. The technique utilizes narrowband Brillouin gain in optical fibers to effectively extract and amplify individual comb lines from densely spaced frequency combs. The extracted comb lines serve as continuous wave lasers for delayed self-heterodyne detection, thereby eliminating the requirement for precise delay control and complex dispersion compensation in traditional fiber delay line methods based on pulse interference. The influence of delay length and frequency interval on the sensitivity of timing jitter measurement is studied in detail. The comparison with traditional methods validates the accuracy of the proposed scheme in timing jitter and linewidth characterization.