基于双斜坡法的光纤应变快速测量方法

Fast Measurement Method of Optical Fiber Strain Based on Double Slope-assisted Technique

为了提高基于布里渊散射的光纤应变测量的实时性,将仅根据两个工作点布里渊增益计算布里渊频移的双斜坡法用于光纤应变测量。介绍双斜坡法的基本原理,基于仿真布里渊谱研究左右两侧工作点选择对布里渊频移计算准确性的影响规律,确定最佳的工作点。基于确定的最佳工作点和不同信噪比的布里渊谱,研究信噪比(signal-to-noise ratio, SNR)对双斜坡法和最小二乘拟合法准确性的影响规律。结果表明:双斜坡法的两个工作点围绕光纤沿线布里渊频移的均值对称时误差最小;随两个工作点频率之差的增加布里渊频移误差先减小后增大。相似准确性下双斜坡法的布里渊谱测量时间仅为最小二乘拟合法的约1/30,布里渊频移的计算时间仅约为后者的1/480。

In order to improve the real-time performance of optical fiber strain measurement based on Brillouin scattering,the double slope-assisted technique,which calculated Brillouin frequency shift based on Brillouin gain at two working points,was used for optical fiber strain measurement.Firstly,the basic principle of double slope-assisted technique was introduced.Secondly,the influence of the left and right working points on the accuracy in Brillouin frequency shift was investigated based on simulated Brillouin spectra,and the optimal working point was determined.Finally,based on the determined optimal working point and Brillouin spectra with different values of signal-to-noise ratio(SNR),the influence of SNR on the accuracy of least-squares fitting method and the double slope-assisted technique was investigated.The results show that if the two working points are symmetrical around the mean value of Brillouin frequency shift along the optical fiber,the error in Brillouin frequency shift attains a minimum value.The Brillouin frequency shift error decreases first and then increases with the frequency difference between the two working points.When the accuracy is similar,the measurement time of Brillouin spectrum of the double slope method is only about 1/30 of the least-squares fitting method.The calculation time of Brillouin frequency shift by the double slope-assisted technique is only about 1/480 of that of the least-squares fitting method.