基于FPGA分布式光纤传感系统的设计及实现

发布时间：2019-06-13 07:19

【摘要】：在分布式光纤传感系统中,数据采样速率及探测脉冲光的脉宽会影响到系统的空间分辨率,而高空间分辨率又是系统所追求的;同时传感信号极其的微弱,信噪比非常低,常常被淹没在噪声中不能直接被识别,需要对数据进行一定的处理。因此,设计出一套不仅可以自由设置探测脉冲光的脉宽、能够进行高速数据采集保证系统空间分辨率,而且能够进行大容量缓存,还能实时对数据进行处理提高信噪比的系统非常的有意义。本文以基于瑞利散射的分布式光纤传感技术原理为基础,结合系统性能需求,选用Altera公司型号为EP4CE15F17C8N的FPGA芯片作为系统的主控制器兼处理器,负责系统的时序、逻辑控制和信号调理,设计了基于FPGA的分布式光纤传感系统。该系统的设计方案为模块化设计,把整个系统分为五个关键功能模块,分别为:脉冲光生成模块、数据采集模块、数据缓存模块、数据处理模块及数据传输模块。对各个模块的主要功能及器件的选择进行了说明:脉冲光生成模块产生适合系统要求的探测脉冲光,可实现最小脉宽5ns、最大频率100MHz的脉冲光生成;数据采集模块采用高速AD6645芯片对传感信号进行A/D转换,FPGA对转换后的数据进行采集,ADC转换速率可达80MSPS;采用两块SDRAM芯片以乒乓操作的形式进行数据缓存;数据处理模块主要是针对传感信号极其微弱和时变特性,先采用滑动累加平均算法对数据进行处理提高信号的信噪比,再对提高信噪比后的信号进行小波变换处理以提取信号的细节部分;通过USB传输模块实现FPGA与上位机间的数据传输。本文详细叙述了系统各个功能模块设计的关键技术及实现方式,同时分析了影响系统空间分辨率和信噪比的相关因素并提出了相应的改进措施,同时对设计的各个功能模块进行功能验证。最后把各个功能模块组合在一起实现整个系统功能,并对整个系统进行验证测试,成功测试到了光纤连接点及光纤尾端处的菲涅尔反射信号,测试结果表明本文设计的基于FPGA的分布式光纤传感系统性能良好,设计方案可行有效,达到预期效果,对分布式光纤传感信号的采集和处理效果明显。
[Abstract]:In the distributed optical fiber sensing system, the data sampling rate and the pulse width of the detection pulse light will affect the spatial resolution of the system, and the resolution between high altitude is pursued by the system. At the same time, the sensing signal is extremely weak and the signal-to-noise ratio is very low, so it is often inundated in the noise and can not be recognized directly, so it is necessary to process the data to a certain extent. Therefore, it is very meaningful to design a set of systems which can not only freely set the pulse width of the detected pulse light, can carry out high-speed data acquisition to ensure the spatial resolution of the system, but also can cache the data in large capacity, and can also process the data in real time to improve the signal-to-noise ratio (SNR). In this paper, based on the principle of distributed optical fiber sensing technology based on Rayleigh scattering, combined with the performance requirements of the system, the FPGA chip of Altera company model EP4CE15F17C8N is selected as the main controller and processor of the system, which is responsible for the timing, logic control and signal conditioning of the system, and a distributed optical fiber sensing system based on FPGA is designed. The design scheme of the system is modular design, the whole system is divided into five key functional modules, namely: pulse light generation module, data acquisition module, data cache module, data processing module and data transmission module. The main functions of each module and the selection of devices are explained as follows: the pulse light generation module produces the detection pulse light suitable for the system requirements, which can realize the pulse light generation of the minimum pulse width of 5 ns and the maximum frequency 100MHz, the data acquisition module uses the high speed AD6645 chip to convert the sensing signal, FPGA collects the converted data, and the ADC conversion rate can reach 80 100MHz. Two SDRAM chips are used to cache the data in the form of ping-pong operation. The data processing module mainly aims at the extremely weak and time-varying characteristics of the sensing signal. Firstly, the sliding accumulation average algorithm is used to process the data to improve the signal-to-noise ratio, and then the signal after improving the signal-to-noise ratio is processed by wavelet transform to extract the details of the signal. The data transmission between FPGA and the upper computer is realized by USB transmission module. In this paper, the key technologies and implementation methods of each functional module of the system are described in detail, and the related factors affecting the spatial resolution and signal-to-noise ratio of the system are analyzed, and the corresponding improvement measures are put forward. At the same time, the function of each functional module is verified. Finally, each functional module is combined to realize the whole system function, and the whole system is verified and tested, and the Fresnel reflection signal at the optical fiber connection point and the end of the optical fiber is successfully tested. The test results show that the distributed optical fiber sensing system based on FPGA has good performance, the design scheme is feasible and effective, and the expected effect is achieved, and the acquisition and processing effect of the distributed optical fiber sensing signal is obvious.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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