本文選題：分布式光纖傳感器　切入點：布里淵散射　出處：《燕山大學》2014年碩士論文

【摘要】：基于布里淵光時域反射(Brillouin Optical Time Domain Reflectometry, BOTDR)的分布式光纖傳感技術是一種利用自發(fā)布里淵散射的測量技術，其測量的參數(shù)作為光纖位置長度的函數(shù)，它可以連續(xù)測量整個光纖長度上沿光纖路徑分布的外部物理參量，并使同時獲取被測參量的空間分布狀況以及其隨時間變化狀態(tài)成為可能。相比于傳統(tǒng)的測量儀器，具有全面的連續(xù)性，遠距離，大容量，無損檢測和網(wǎng)絡智能等優(yōu)點。然而由于自發(fā)布里淵散射光極其微弱，BOTDR系統(tǒng)中空間分辨率和動態(tài)范圍兩大性能指標相互制約。因此，本文在深入分析BOTDR系統(tǒng)傳感機理的基礎上，提出將偽隨機序列應用于傳感系統(tǒng)中，以提高系統(tǒng)測量的信噪比并獲得較好的測量效果。 首先，介紹了分布式光纖傳感技術的分類和基于Brillouin散射的分布式光纖傳感技術的國內外發(fā)展現(xiàn)狀；介紹了光纖中的三種散射效應，推導了Brillouin頻移、散射譜強度與溫度、應變的定量關系，介紹了BOTDR系統(tǒng)的信號檢測原理，并重點闡述了相干檢測原理，并給出了系統(tǒng)的性能參數(shù)指標。 其次，提出采用偽隨機序列編碼技術來改善Brillouin分布式光纖傳感系統(tǒng)的信噪比。介紹了偽隨機序列的概念和產生機理，并就產生的偽隨機序列進行性質仿真驗證。最后將m序列應用于BODTR系統(tǒng)，通過仿真分析m序列對系統(tǒng)信噪比的影響。 再次，將m序列應用于BOTDR光纖傳感系統(tǒng)，設計了編碼光脈沖模塊和散射信號采集與相關解調處理模塊。通過理論分析和實驗研究，證明與單脈沖探測方案相比，該方案可以顯著提高BOTDR光纖傳感系統(tǒng)的信噪比。驗證了采用m序列改善系統(tǒng)性能的可行性。 最后，設計了一套基于編碼光脈沖和相關解調的BOTDR分布式光纖傳感系統(tǒng)，并對其各個子系統(tǒng)進行了闡述。通過分布式溫度測量實驗證明與單脈沖探測方案相比，該方案可以在不降低空間分辨率的前提下有效降低測試系統(tǒng)噪聲。
[Abstract]:The distributed optical fiber sensing technology based on Brillouin Optical Time Domain reflectometry (BOTDR) is a measurement technique based on self-published Brillouin scattering.It can continuously measure the external physical parameters along the path of the fiber and make it possible to obtain the spatial distribution of the measured parameters and the variation of the parameters with time at the same time.Compared with traditional measuring instruments, it has the advantages of overall continuity, long distance, large capacity, nondestructive testing and network intelligence.However, the spatial resolution and dynamic range of the self-issued Brillouin scattering light are restricted to each other in the BOTDR system.Therefore, on the basis of deeply analyzing the sensing mechanism of BOTDR system, this paper proposes to apply pseudorandom sequences to the sensing system to improve the signal-to-noise ratio (SNR) of the system and obtain better measurement results.Firstly, the classification of distributed optical fiber sensing technology and the development status of distributed optical fiber sensing technology based on Brillouin scattering are introduced, three scattering effects in optical fiber are introduced, the frequency shift of Brillouin, the intensity and temperature of scattering spectrum are derived.The quantitative relationship of strain, the principle of signal detection in BOTDR system is introduced, the principle of coherent detection is expounded, and the performance parameters of the system are given.Secondly, pseudorandom sequence coding technique is proposed to improve the signal-to-noise ratio of Brillouin distributed optical fiber sensor system.The concept and mechanism of pseudorandom sequence are introduced, and the properties of pseudorandom sequence are verified by simulation.Finally, m sequence is applied to BODTR system, and the influence of m sequence on SNR is analyzed by simulation.Thirdly, the m sequence is applied to the BOTDR optical fiber sensing system, and the coded optical pulse module and the scattering signal acquisition and correlation demodulation processing module are designed.The theoretical analysis and experimental study show that the proposed scheme can significantly improve the signal-to-noise ratio (SNR) of the BOTDR optical fiber sensing system compared with the monopulse detection scheme.The feasibility of using m sequence to improve system performance is verified.Finally, a BOTDR distributed optical fiber sensing system based on coded optical pulse and related demodulation is designed, and its subsystems are described.The experimental results of distributed temperature measurement show that compared with the monopulse detection scheme, the proposed scheme can effectively reduce the noise of the test system without reducing the spatial resolution.
【學位授予單位】：燕山大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TP212;TN911.3

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