Analysis of Factors Affecting Accuracy of Brillouin Frequency Shift Extraction Based on Similarity Matching

The Brillouin frequency shift extraction algorithm based on similarity matching method exhibits considerable adaptability and does not require a predefined model. In this study, the influence of the brillouin linewidth (short for linewidt), signal-to-noise ratio, sweeping step, and sweeping range on the extraction accuracy of the frequency shift is systematically studied by varying each factor to obtain the influence of the spectral signals and sweep parameters on the performance of the algorithm. The frequency shift error is a linear function of the Brillouin linewidth. The linewidth difference between the selected detected spectrum and the selected reference spectrum does not considerably affect the accuracy of the algorithm. When the signal-to-noise ratio of the selected detected spectrum remains constant, the frequency shift error decreases exponentially with the increasing signal-to-noise ratio of the selected reference spectrum, and vice versa. When the frequency sweep step is maintained constant, the frequency shift error increases with the increasing sweep range of the selected reference spectrum; this is accompanied by a linear increase in the calculation time. The frequency shift error is the smallest when the frequency range of the selected detected spectrum is twice the linewidth. Furthermore, the obtained results can provide a reference for the accurate extraction of Brillouin frequency shift.