Zhang Yue, Zhang Ji-long, Li Xiao, Wang Zhi-bin, Wang Peng
Key Laboratory of Instrumentation Science and Dynamic Measurement, Engineering Technology Research Center of Shanxi Province for Photoelectric Information and Instrument, North University of China, Taiyuan 030051, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 May;29(5):1300-3.
Unlike the Brillouin scattering, the anti-Stokes Raman scattering i n optic fiber is unrelated with the strain, but isonly the function of the absolute temperature. The frequency shift caused by Raman scattering is about 13.95 Thz. So the Raman scattering is easier to be picked up than Brillouin scattering. It has certain advantage while being used as the signal of the distributed optic-fiber temperature sensor. But it is weaker than the Brillouin scattering, the peak photocurrent produced in APD is of the order of nA, near or even lower than the noise current of the APD. The N/S after being photo-electric transformed is usually lower than 1. The means of Fourier transform and wavelet transform is not effective in dealing with such kind of signal. Through analyzing the feature of the anti-Stokes Raman scattering signal and using the wavelet, the anti-Stokes Raman scattering signal after being cumulated & averaged was picked up. The supersensitive detecting below the "noise current" of the APD was carried out with the senstivity: 0.104 nA x K(-1), lower than the "noise current" of the APD 2 classes.
与布里渊散射不同，光纤中的反斯托克斯拉曼散射与应变无关，仅是绝对温度的函数。拉曼散射引起的频移约为13.95太赫兹。因此，拉曼散射比布里渊散射更容易被检测到。在用作分布式光纤温度传感器的信号时具有一定优势。但它比布里渊散射弱，雪崩光电二极管（APD）产生的峰值光电流为纳安级，接近甚至低于APD的噪声电流。光电转换后的信噪比通常低于1。傅里叶变换和小波变换方法在处理这类信号时效果不佳。通过分析反斯托克斯拉曼散射信号的特征并利用小波，提取了累加平均后的反斯托克斯拉曼散射信号。实现了低于APD“噪声电流”的超灵敏检测，灵敏度为0.104 nA×K⁻¹，比APD的“噪声电流”低2个量级。
