Design of optical wedge demodulation system for fiber Fabry-Perot sensor
doi: 10.37188/CO.2020-0204
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摘要: 为了实现光纤法布里-珀罗(简称法珀)传感器腔长的解调，提出一种新型光楔式非扫描相关解调系统，对该系统所采用的器件特性及结构进行分析研究。首先，通过模拟不同光谱分布的光源及不同表面反射率的光楔，分析其相关干涉信号并给出系统器件的最优化结构参数。接着通过对比鲍威尔棱镜与柱透镜在线阵CCD上的光强分布特性，实现更均匀的光谱分布。最后，给出解调系统的具体实施方案及数据处理方法。实验结果表明：光源光谱具有高斯分布且谱宽较大及光楔表面反射率
$ R = 0.5$ 时，相关干涉信号特征明显，便于解调。最终解调系统实现在60~100 μm腔长范围内误差小于0.025%的解调。这种光楔式非扫描相关解调方案可以实现光纤法珀腔的传感解调，并可以提高不同类型光纤法珀传感器功率适应性。Abstract: In order to realize the demodulation of the cavity length of the fiber-optic FP sensor, a new optical wedge-type non-scanning correlation demodulation system is proposed, and the characteristics and structure of the devices used in the system are analyzed and studied. First, by simulating the light sources with different spectral distributions and the optical wedges with different surface reflectivities, the correlation interference signals are analyzed and the optimal structure parameters of the system components are given. Then by comparing the light intensity distribution characteristics of the Powell prism and cylindrical lens on the linear array CCD, more uniform spectral distribution is achieved. Finally, the specific implementation scheme and data processing method of the demodulation system are given. The experimental results show that when the light source spectrum has a Gaussian distribution and large spectral width and the reflectivity of the wedge surface is$R = 0.5$ , the characteristics of the correlation interference signal are obvious and convenient for demodulation. Finally, the demodulation system achieves the demodulation effect with an error of less than 0.025% within the cavity length range of 60 μm-100 μm. This optical wedge-type non-scanning correlation demodulation method can realize the sensing demodulation of the fiber-optic FP cavity and improve the power adaptability of different types of fiber-optic FP sensors. -
图 1 光纤法珀传感器光楔式解调系统示意图
Figure 1. Schematic diagram of optical wedge demodulation system for fiber-optic FP sensor
图 4 不同光谱分布下相关干涉信号输出分布
Figure 4. The output light intensity distribution of correlation interference signal under different spectral distributions
图 6 (a)柱透镜和(b)鲍威尔棱镜光强分布效果图
Figure 6. Light intensity distributions of (a) cylindrical lens and (b) Powell prism
图 7 柱透镜和鲍威尔棱镜光强分布经CCD探测基底信号图
Figure 7. Light intensity distributions of the background signals from cylindrical lens and Powell prism detected by CCD
图 8 不同表面反射率的光楔的相关干涉信号对比图
Figure 8. Comparison of correlation interference signals obtained by the optical wedges with different surface reflectivities
图 9 光纤法珀传感器解调系统的光楔结构。(a)光楔制作示意图；(b)CCD结合光楔实物图
Figure 9. Optical wedge structure of fiber-optic FP sensor demodulation system. (a) Schematic diagram of optical wedge fabrication; (b) combination of CCD and optical wedge
图 11 光纤法珀传感器光楔式解调实验系统。(a) 整体结构 (b) 传感器细节图 (c) 暗盒内部结构
Figure 11. Experimental optical wedge demodulation system for the fiber-optic FP sensor. (a) Overall structure; (b) detailed picture of the sensor; (c) internal structure of dark box
图 12 光纤法珀传感器光楔式解调系统CCD采集信号图
Figure 12. Signals collected by CCD in the optical wedge demodulation system for fiber-optic FP sensor
图 13 光纤法珀传感器光楔式解调系统测试结果图
Figure 13. Test results of optical wedge demodulation system for fiber-optic FP sensor
图 14 不同光源功率下采用鲍威尔棱镜及柱透镜的解调系统的解调范围对比图
Figure 14. Comparison of demodulation ranges of the demodulation systems using Powell prism and cylindrical lens under different light source powers
表 1 Test data
Table 1. Test data
Light source
power/mWDemodulation range of
Powell prism/μmDemodulation range of
cylindrical lens/μm5 59.988~100.163 6 58.950~97.83 68.612~84.542 7 59.728~100.531 65.757~86.286 8 59.728~100.531 65.776~94.506 9 59.733~101.993 65.637~94.512 10 60.217~100.739 64.856~93.776 11 60.306~98.514 65.103~95.525 12 59.601~98.966 63.339~94.497 13 59.844~98.817 63.699~95.04 
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