Lopez-Gil Alexia, Soto Marcelo A, Angulo-Vinuesa Xabier, Dominguez-Lopez Alejandro, Martin-Lopez Sonia, Thévenaz Luc, Gonzalez-Herraez Miguel
Opt Express. 2016 Jul 25;24(15):17200-14. doi: 10.1364/OE.24.017200.
We evaluate the Brillouin frequency shift (BFS) determination error when utilizing the Brillouin phase spectrum (BPS) instead of the Brillouin gain spectrum (BGS) in BOTDA systems. Systems based on the BPS perform the determination of the BFS through a linear fit around the zero de-phase frequency region. An analytical expression of the error obtained in the BFS determination as a function of the different experimental parameters is provided and experimentally validated. The experimental results show a good agreement with the theoretical predictions as a function of the number of sampling points, signal-to-noise ratio (SNR) and Brillouin spectral linewidth. For an equal SNR and linewidth, the phase response only provides a better BFS estimation than the gain response when the fit is performed over a restricted frequency range around the center of the spectral profile. This may reduce the measurement time of specific BOTDA systems requiring a narrow frequency scanning. When the frequency scan covers most of the Brillouin spectral profile, gain and phase responses give very similar estimations of the BFS and the BPS offers no crucial benefit.
我们评估了在布里渊光时域反射仪（BOTDA）系统中使用布里渊相位谱（BPS）而非布里渊增益谱（BGS）时的布里渊频移（BFS）测定误差。基于BPS的系统通过在零去相位频率区域周围进行线性拟合来确定BFS。给出了作为不同实验参数函数的BFS测定中所获误差的解析表达式，并通过实验进行了验证。实验结果表明，作为采样点数、信噪比（SNR）和布里渊光谱线宽的函数，实验结果与理论预测吻合良好。对于相同的SNR和线宽，当在光谱轮廓中心周围的受限频率范围内进行拟合时，相位响应仅比增益响应提供更好的BFS估计。这可能会减少需要窄频率扫描的特定BOTDA系统的测量时间。当频率扫描覆盖大部分布里渊光谱轮廓时，增益和相位响应给出的BFS估计非常相似，并且BPS没有显著优势。
