光纤傅里叶变换光谱术在光纤光栅传感解调中的应用

Application of fiber Fourier transform spectroscopy to fiber Bragg grating demodulation

介绍了光纤Mach-Zehnder干涉仪的基本原理和光纤傅里叶变换光谱仪(FFTS)的结构;基于光纤Mach-Zehnder干涉仪,采用傅里叶变换光谱算法对光纤Bragg光栅传感器的波长进行了解调。宽带光源发出的光经过光纤耦合器进入光纤Bragg光栅,其反射光由耦合器返回进入到FFTS中进行测量,FFTS的最高光谱分辨率达到0.05 cm-1,即在近红外1 550 nm波长处分辨率为0.012 nm。分别对光纤Bragg光栅的应变特性和温度特性进行了测量。测量显示:光纤Bragg光栅的应变灵敏度为0.833 pm/με,温度灵敏度为19.78 pm/℃。得到的结果表明FFTS系统具有高分辨率、大测量范围的特点,可满足光纤Bragg光栅传感器波长解调的需求。

The elementary principle of a fiber Mach-Zehnder interferometer and the structure of a Fiber Fourier Transform Spectroscopy（FFTS） were introduced.Then,a novel demodulation scheme for the fiber Bragg grating sensor based on the fiber Mach-Zehnder interferometer and the FFTS was designed to achieve highly stable and accurate wavelength demodulation.In demodulation,the light emitted from a broadband light source was through the fiber coupler into a fiber Bragg grating,and the reflected light of fiber Bragg grating came back from the fiber coupler into the FFTS.The optical path difference of FFTS is up to 10 cm and the maximum spectral resolution is 0.05 cm-1 when the unilateral Fourier transform algorithm is used,which means the wavelength resolution is 0.012 nm in near infrared scope of 1 550 nm.The strain characteristics and temperature characteristics of a fiber Bragg grating were measured by the FFTS,respectively.Experimental results indicate that the strain sensitivity is 0.833 pm/με and the temperature sensitivity is 19.78 pm/℃.Obtained data show that the FFTS system has advantages of high spectral resolution and wide measuring ranges and it can satisfy the wavelength demodulation requirements of fiber Bragg grating sensors.