【作者】 高庆；

【导师】 朱永；

【作者基本信息】 重庆大学 ， 光学工程， 2005， 硕士

【摘要】 随着我国基础设施建设速度加快,人们对于结构的健康监测也越来越关注。常规的监测方法越来越不能满足长期健康测量的要求,因而国内外科研人员都将目光投向光纤传感器。在众多的光纤传感器中,由于FBG传感器具有波长编码,易复用的优点,光纤F-P 传感器具有静态测量精度高,制作简单、成本低的特点,而成为实际结构健康监测中使用广泛的两种传感器。在一个大型的工程中,往往需要综合使用这两种传感器,然而在研究和工程应用中解调装置往往都是针对其中的一种传感器研制开发的。所以为了节约解调系统成本,提高系统的集成度、可靠性,增加易用性,有必要研制一套通用的解调系统,来实现对光纤F-P和FBG传感器的解调。论文首先系统地分析了光纤FBG 和F-P 传感器技术特点和各种解调方法的原理,并在此基础上提出了以可调光纤F-P滤波器为基础的通用解调方案。接着,针对可调光纤F-P 滤波器的非理想性能的影响,理论分析了设置波长参考的必要性,指出了设置单波长参考的不足,提出通过增加光纤F-P 滤波器扫描电压的幅值将单波长参考变成双波长参考的新方法,并设计了基于恒温FBG 的波长参考装置。根据设计的系统光路方案,分析了系统对可调光纤F-P 滤波器、宽带光源、探测器等主要光学部件参数的要求,选择了具体的部件。然后,根据传感输出的模拟信号的特点设计了模拟信号的调理电路;在分析了可调光纤F-P 滤波器的驱动信号产生方式的基础上,选择了由DSP 软件产生、DA 输出的驱动信号发生电路方案,保证了双通道数据采集的时间一致性;完成了以DSP(TMS320VC5416)为核心的数字电路的设计,主要包括AD、DA、CPLD、FLASH、HPI 接口等功能单元电路。在硬件设计的基础上,还设计了上位PC 机和DSP 的软件系统,两者之间通过串口进行信息的交换。用C++ Builder 编制了上位机的程序,完成了通过串口通讯来控制DSP 的动作,实现数据的可视化输出、数据的存储和查询等功能;DSP 部分的程序能够实现数据的高速单次和连续采集和处理的功能,并具备和上位机通讯的能力。最后,分别利用光纤FBG 和F-P 传感器进行了解调实验,通过对FBG 的实验发现双波长参考可以提高测量的精度,实验结果表明所设计的系统能够对两种传感器正常解调,实现了预期的目的。更多还原

【Abstract】 With the development of infrastructures in China, health monitoring of those structures has become a hot point. As fiber optical sensors have more advantages over traditional ones, they have been studied widely. There are two typical ones, fiber Bragg grating (FBG) sensor and fiber Fabry-Perot (F-P) sensor. FBG sensor is often needed due to its wavelength-decoded characteristic and multiplexing ability, while fiber F-P sensor is utilized due to the advantages of high measurement accuracy, low cost and insensitivity of temperature fluctuation. Different interrogation units have been developed according to different sensing principle of those sensors at present. In many practical complicated sensing systems, those two types of fiber sensors may be both wanted, therefore a set of general demodulation system for those two sensors is demanded. The purpose of this thesis is to study a general demodulation method for FBG and fiber F-P sensors, and design relevant demodulation system. The main points of the thesis are as follows: Firstly, the technology characteristics of FBG and fiber F-P sensors are analyzed, and the principles of classical demodulation methods for them are investigated and compared. Then a conclusion is drawn that a general demodulation system can be realized based on tunable fiber F-P filter, and the setup of general demodulation system is put forwarded. Secondly, as the spectrum measurement precision of tunable fiber F-P filter was affected by its performance defect, a standard wavelength reference is required in the general demodulation system. The wavelength reference theory is then studied, and a single wavelength reference based on thermostatic FBG is presented. Further research shows that there is shortage of single wavelength reference, and a new wavelength reference scheme to increase spectrum measurement accuracy is put forwarded. With this scheme, the single wavelength reference can be easily converted to dual wavelength references. Therefore, an actual wavelength reference device is designed and manufactured. Other main optical components, such as tunable fiber F-P filter, the board band source, the photo detector and so on, are selected to meet the requirements of the designed system. Thirdly, analog circuits are designed to condition sensor’s output signal and the methods of generating periodic driving signal for tunable fiber F-P filter are also analyzed. In order to sample two channels synchronously, the method of DA+DSP signal generating is adopted. The hardware based on DSP (TMS320VC5416) system is developed, and peripheral circuits of the DSP system are accomplished including FLASH, AD, DA, etc. In addition, communication interfaces, such as serial interface with PC and HPI interface with host processor, are also developed. Fourthly, the software for upper PC and DSP system are written. The main functions of the upper PC software (in C++ Builder language) are to send commands to DSP system, receive data form DSP system, and display, store results etc. As for DSP system, the program is used for sampling and processing data with high speed. Finally, temperature test of SLD driver is carried out, and the results show that SLD driver works well. In order to compare the performances of wavelength reference schemes, single wavelength and dual wavelength references, FBG temperature sensing experiment is carried out. It shows that measurement accuracy of dual wavelength reference is higher than that of the single one. Measuring experiments are also done on fiber F-P sensor with general demodulation system. All results demonstrated the feasibility of the general demodulation system, and it indicates a potential possibility of using the system in practical engineering applications.更多还原