【作者】 刘琨；

【导师】 刘铁根； 井文才；

【作者基本信息】 天津大学 ， 光学工程， 2009， 博士

【摘要】 本文采用F-P可调谐光滤波器和掺铒光纤放大器构建光纤传感系统,并从理论、系统和实验三个方面对光纤传感技术进行深入研究。光纤传感系统具有开环和闭环两种结构,可分别实现应变、气体参量的准分布式、高灵敏度传感。理论分析了开环光纤传感系统中光栅光谱曲线和F-P可调谐光滤波器3-dB带宽之间的数学关系,从理论和实验两个方面研究了光滤波器的非线性特性并对其进行补偿;设计完成了系统的光学、机械、电路和数据处理部分,并对传感网络进行扩展;采用该系统进行应变传感实验,解调灵敏度优于3με,扫描频率达到6 0 Hz。分别采用速率方程和传输方程建立了基于闭环光纤传感系统的气体传感理论模型,分析了泵浦功率和系统损耗对气体传感灵敏度的影响;设计完成了系统的光学、机械和数据处理部分;采用波长扫描技术进行乙炔气体传感,灵敏度优于100 ppm,引入波长调制技术后乙炔气体传感的灵敏度提高至75 ppm,同时还可实现气体种类识别。工作中的主要创新点:1.基于多光束干涉理论建立了F-P可调谐光滤波器的系统模型,研究了光滤波器的非线性特性及其来源;提出了基于开环光纤传感系统的光滤波器非线性特性研究方法,利用波长-电压关系及其多项式拟合分析了光滤波器的非线性特性及波长随机误差;采用两种方法实现了光滤波器的非线性补偿。2.阐明了采用传输方程研究气体传感灵敏度的可行性;深入探讨了泵浦功率和系统损耗对气体传感灵敏度的影响,并从实验上进行验证;理论推导了光纤气体传感系统的检测极限。3.将波长扫描技术和波长调制技术引入光纤气体传感系统,提出了基于虚拟仪器技术的波长调制/二次谐波提取方案,极大的提高了气体传感灵敏度,同时实现了气体的种类识别。更多还原

【Abstract】 - II - Optical fiber sensing system is developed in this dissertation, using Fabry-Perot (F-P) type tunable optical filter (TOF) and Erbium-doped fiber amplifier (EDFA). Further study has been done in theory, systems and experiments. The system has two configurations of open loop and closed loop, which can be used to realize strain and gas sensing respectively with quasi-distributed ability and high sensitivity.The relationship between the detected spectra of the gratings and the 3-dB bandwidth of the F-P type TOF in the open loop optical fiber sensing system is deduced mathematically. The nonlinearity of the F-P type TOF is investigated theoretically and experimentally, which can be compensated. The optics, mechanics, hardware and data processing of the system had been designed and realized. And the tolerance extension of the system had been also discussed. The system can be used to realize strain sensing with demodulation sensitivity less than 3μεand scan rate close to 6 0 Hz.Based on closed loop optical fiber sensing system, the gas sensing model is established using rate equations and transmission equations respectively. The influences of pump power and system loss on the gas sensing sensitivity are analyzed. The optics, mechanics and data processing of the system had been designed and realized. Using wavelength sweep technique, the system can be used to realize acetylene sensing with sensitivity less than 100 ppm. And the sensitivity can be enhanced to 75 ppm by use of wavelength modulation technique, with probability of gas recognition at the same time.Major innovations of this dissertation:1. The model of F-P type TOF is established based on multiple-beam interference. And the nonlinearity characteristic of F-P type TOF and its source are analyzed. The investigation of F-P type TOF nonlinearity using the open loop optical fiber sensing system is put forward. And the wavelength-voltage relationship and its polynomial fit are adopted to model the nonlinearity and analyze the random error of wavelength measurement. The nonlinearity of F-P type TOF can be compensated by use of two methods respectively.2. Transmission equations are used to model the gas sensing system and investigate the sensitivity. The influences of pump power and system loss on the gas sensing sensitivity are analyzed, which can be validated experimentally. And the detection limit of the gas sensing system is deduced theoretically.3. Wavelength sweep technique and wavelength modulation technique are introduced into the gas sensing system. The scheme of wavelength modulation/2nd harmonic components calculation based on virtual instrument technique is put forward. By using these techniques, the gas sensing sensitivity is improved remarkably, and the gas recognition can be also realized.更多还原