本文選題：光纖傳感 + 布里淵散射��； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：近年來(lái),布里淵光時(shí)域分析(Brillouin Optical Time Domain Analysis, BOTDA)作為一項(xiàng)應(yīng)用在長(zhǎng)距離上的分布式光纖傳感技術(shù),可以用于任意位置上的溫度和應(yīng)變測(cè)量。因?yàn)槠洫?dú)特的優(yōu)勢(shì),BOTDA技術(shù)被廣泛地應(yīng)用在大型工程設(shè)施的結(jié)構(gòu)健康診斷上。為了進(jìn)一步提高BOTDA在長(zhǎng)距離測(cè)量過(guò)程中的信噪比,本文采用了基于差分放大的方法,來(lái)改進(jìn)BOTDA傳感系統(tǒng)。介紹了布里淵散射形成的物理過(guò)程,以及BOTDA技術(shù)的傳感機(jī)制,研究了直接探測(cè)與相干探測(cè)的信噪比,分析了直接探測(cè)和相干探測(cè)BOTDA系統(tǒng)的噪聲來(lái)源。并且,針對(duì)使用對(duì)數(shù)檢波器的單邊帶調(diào)制相干探測(cè)BOTDA系統(tǒng)在樣機(jī)集成的過(guò)程中,由于數(shù)據(jù)采集卡性能限制而產(chǎn)生的較大量化噪聲的問(wèn)題,采用了差分放大的方法,用來(lái)減小該量化噪聲,提高傳感系統(tǒng)的信噪比。該方法使用一個(gè)頻率可調(diào)的微波信號(hào)和另外一個(gè)頻率固定的微波信號(hào)來(lái)調(diào)制光源發(fā)出的激光,這兩個(gè)微波信號(hào)的功率相同,被調(diào)制的光信號(hào)分別作為探測(cè)光和參考光。其中,探測(cè)光的頻率在布里淵增益范圍內(nèi)掃描,而參考光的頻率在布里淵增益范圍之外。因此,只有探測(cè)光和本振光之間的拍頻信號(hào)攜帶布里淵增益信息,而參考光和本振光之間的拍頻信號(hào)不具有布里淵增益。然后,在經(jīng)過(guò)降頻之后,參考光和探測(cè)光的功率由兩個(gè)對(duì)數(shù)檢波器分別探測(cè)得到。將探測(cè)得到的兩路信號(hào)送入差分放大器中,就可以消除多余的直流信號(hào),并且布里淵信號(hào)被放大。同時(shí),為了證實(shí)這種差分放大方法的有效性,又采用對(duì)比實(shí)驗(yàn)的方法對(duì)其進(jìn)行了驗(yàn)證。此外,為了提升BOTDA系統(tǒng)在實(shí)際測(cè)量溫度和應(yīng)變時(shí)的運(yùn)行效率,使該傳感系統(tǒng)向著產(chǎn)業(yè)化方向發(fā)展,我們研究和探討了 BOTDA系統(tǒng)實(shí)現(xiàn)自動(dòng)控制所需的相關(guān)技術(shù)方法,并且在LabVIEW環(huán)境下編寫(xiě)了一套上位機(jī)軟件系統(tǒng)以實(shí)現(xiàn)上述功能。該軟件系統(tǒng)實(shí)現(xiàn)了對(duì)BOTDA系統(tǒng)各個(gè)模塊的綜合控制、對(duì)采集到的數(shù)據(jù)的存儲(chǔ)和處理。此外,我們還添加了對(duì)測(cè)量結(jié)果和警報(bào)的顯示功能。
[Abstract]:Brillouin Optical Time Domain Analysis, BOTDA) (Brillouin Optical Time Domain Analysis, BOTDA), as a distributed optical fiber sensing technique applied in long distance, can be used to measure temperature and strain at any position in recent years. Because of its unique advantage, BOTDA technology is widely used in structural health diagnosis of large engineering facilities. In order to improve the signal-to-noise ratio (SNR) of BOTDA in the long distance measurement, the differential amplification method is used to improve the BOTDA sensing system. The physical process of Brillouin scattering and the sensing mechanism of BOTDA are introduced. The signal-to-noise ratio of direct detection and coherent detection is studied. The noise sources of direct detection and coherent detection BOTDA systems are analyzed. In order to solve the problem of large quantization noise caused by the performance limitation of data acquisition card during the process of prototype integration, the differential amplification method is used to detect the single sideband modulation coherent BOTDA system using logarithmic detector. It is used to reduce the quantization noise and improve the signal-to-noise ratio of the sensor system. The method uses one frequency adjustable microwave signal and another fixed frequency microwave signal to modulate the laser emitted by the light source. The two microwave signals have the same power and the modulated optical signal is used as the probe light and the reference light respectively. The frequency of the probe light is scanned within the Brillouin gain range, while the reference light frequency is outside the Brillouin gain range. Therefore, only the beat signal between the probe light and the local oscillator light carries Brillouin gain information, while the beat signal between the reference light and the local oscillator light has no Brillouin gain. Then, the power of the reference light and the detection light are detected by two logarithmic detectors after the frequency reduction. When the detected two signals are fed into the differential amplifier, the redundant DC signal can be eliminated, and the Brillouin signal is amplified. At the same time, in order to verify the effectiveness of the differential amplification method, a comparative experiment is used to verify it. In addition, in order to improve the operating efficiency of BOTDA system when measuring temperature and strain, and to make the sensor system develop towards industrialization, we study and discuss the relevant technical methods needed to realize the automatic control of BOTDA system. And under the environment of LabVIEW, a host computer software system is written to realize the above functions. The software system realizes the integrated control of each module of the BOTDA system and the storage and processing of the collected data. In addition, we have added the display of measurements and alerts.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP212

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