本文選題：低相干干涉 + 光纖麥克風(fēng)��； 參考：《安徽大學(xué)》2017年碩士論文

【摘要】：隨著光纖傳感技術(shù)的進(jìn)步與發(fā)展,相比于電學(xué)麥克風(fēng),光纖麥克風(fēng)在微納信號(hào)探測(cè)、光聲光譜測(cè)量等領(lǐng)域具有更廣的應(yīng)用前景。其中,干涉型光纖麥克風(fēng)因其具有結(jié)構(gòu)輕巧、靈敏度高、抗電磁干擾等優(yōu)點(diǎn),吸引了諸多研究人員的關(guān)注。在外腔干涉結(jié)構(gòu)的光纖麥克風(fēng)系統(tǒng)中,薄膜的性能及其制備工藝非常重要,對(duì)薄膜振動(dòng)幅值的定量測(cè)量可直接反映其靈敏度的大小。本文對(duì)基于高靈敏度薄膜的光纖傳感探頭進(jìn)行了研究,結(jié)合可實(shí)現(xiàn)物理量絕對(duì)測(cè)量的低相干光纖微分干涉儀,對(duì)薄膜探頭的靈敏度進(jìn)行了高精度測(cè)量,并將其應(yīng)用于光聲光譜氣體濃度定量標(biāo)定及氣體泄漏聲信號(hào)特征譜分析中。首先,我們采用MEMS等離子體硅刻蝕方法制備大尺寸(直徑3.1mm)的鋁-聚酰亞胺復(fù)合薄膜。該制備方法可在一定程度上釋放膜內(nèi)應(yīng)力,提高薄膜表面平整度;通過(guò)稀釋聚酰胺酸濃度,使膜的厚度低于500nm。復(fù)合薄膜的鋁層在刻蝕過(guò)程中可保護(hù)聚酰亞胺不被破壞,同時(shí)提高膜整體的光反射率;聚酰亞胺的彈性性能好,且其具有的高強(qiáng)度特性可保證復(fù)合薄膜整體的結(jié)構(gòu)強(qiáng)度。其次,對(duì)基于鋁-聚酰亞胺薄膜探頭進(jìn)行了實(shí)驗(yàn)測(cè)量。由于低相干微分干涉測(cè)量可實(shí)現(xiàn)非接觸式絕對(duì)幅值的振動(dòng)測(cè)量,我們將其與鋁-聚酰亞胺薄膜探頭組合成低相干微分干涉光纖麥克風(fēng)系統(tǒng)。該系統(tǒng)可以實(shí)現(xiàn)對(duì)膜振動(dòng)幅值絕對(duì)位移量的測(cè)量,由此直接得出薄膜探頭的聲壓靈敏度。實(shí)驗(yàn)結(jié)果表明:系統(tǒng)的線性響應(yīng)度良好;在頻率響應(yīng)上,系統(tǒng)在1KHz至5KHz頻率段聲壓靈敏度保持穩(wěn)定,平均為120nm/Pa,其最小可探測(cè)聲壓為53uPa;鋁-聚酰亞胺薄膜的結(jié)構(gòu)穩(wěn)定性好,其性能在四個(gè)月時(shí)間內(nèi)保持不變;具有良好的溫度穩(wěn)定性,溫度的上升對(duì)其靈敏度產(chǎn)生微弱的負(fù)影響,影響幅度最大為9.3%。最后,基于鋁-聚酰亞胺膜的光纖麥克風(fēng),我們分別開(kāi)展了光纖光聲光譜測(cè)量和氣體泄漏檢測(cè)的應(yīng)用研究。本文對(duì)光纖光聲光譜測(cè)量系統(tǒng)進(jìn)行了模塊化設(shè)計(jì),包括可調(diào)諧激發(fā)光模塊,開(kāi)放式微腔光聲池和低相干微分干涉麥克風(fēng)模塊,并對(duì)每個(gè)模塊進(jìn)行實(shí)驗(yàn)驗(yàn)證,之后對(duì)整個(gè)系統(tǒng)進(jìn)行實(shí)驗(yàn)。實(shí)驗(yàn)結(jié)果表明:開(kāi)放式微腔光聲池的諧振頻率為3KHz,可產(chǎn)生最大光聲信號(hào)為2.3mPa;相比傳統(tǒng)電學(xué)麥克風(fēng)(BK2192),在脈沖頻率6KHz和7KHz上的信號(hào)強(qiáng)度分別高出10.2dB和9.9dB。在氣體泄漏檢測(cè)方面,通過(guò)拾取氣體泄漏的四極子聲場(chǎng)信號(hào),分辨氣體泄漏的特征頻譜來(lái)判斷氣罐泄漏的相關(guān)信息。實(shí)驗(yàn)表明,隨著氣罐內(nèi)壓及泄漏孔尺寸的改變,氣體泄漏特征譜只出現(xiàn)整體的起伏變化沒(méi)有發(fā)生頻譜上的變化。該研究為氣體泄漏檢測(cè)方法提供了新的檢測(cè)手段。
[Abstract]:With the progress and development of optical fiber sensing technology, compared with electric microphone, fiber optic microphone has a wider application prospect in micro-nano signal detection, photoacoustic spectrum measurement and other fields. Among them, interferometric fiber-optic microphone has attracted many researchers' attention because of its advantages of light structure, high sensitivity, anti-electromagnetic interference and so on. In the optical fiber microphone system with external cavity interference structure, the performance of the film and its fabrication process are very important. The quantitative measurement of the vibration amplitude of the film can directly reflect the sensitivity of the film. In this paper, the optical fiber sensor based on high sensitivity thin film is studied, and the sensitivity of the thin film probe is measured with high precision combined with the low coherent fiber differential interferometer, which can realize the absolute measurement of physical quantity. It is applied to the quantitative calibration of the photoacoustic spectrum gas concentration and the analysis of the characteristic spectrum of the gas leakage acoustic signal. Firstly, large size (diameter 3.1mm) aluminum polyimide composite films were fabricated by MEMS plasma silicon etching. The prepared method can release the stress in the film to a certain extent and improve the surface smoothness of the film, and the thickness of the film is lower than 500 nm by diluting the concentration of polyamide acid. The aluminum layer of the composite film can protect the polyimide from destruction and improve the overall photoreflectivity of the film. The elastic property of the polyimide is good and its high strength characteristic can guarantee the structural strength of the composite film as a whole. Secondly, the aluminum-polyimide film probe was measured experimentally. Because the non-contact absolute amplitude can be measured by low coherence differential interferometry, we combine it with aluminum polyimide film probe to form a low coherent differential interference optical fiber microphone system. The system can measure the absolute displacement of the film vibration amplitude and obtain the sound pressure sensitivity of the film probe directly. The experimental results show that the linear responsivity of the system is good, the sound pressure sensitivity of the system is stable in the frequency range from 1kHz to 5KHz, the average sound pressure is 120 nm / Pa, and the minimum detectable sound pressure is 53uPa.The structure stability of the aluminum-polyimide film is good. Its performance remains unchanged in four months, and has good temperature stability. The temperature rise has a weak negative effect on its sensitivity, and the maximum effect is 9.3%. Finally, based on the aluminum-polyimide film optical fiber microphone, we developed the optical fiber photoacoustic spectrum measurement and gas leakage detection. In this paper, the modularization design of optical fiber optoacoustic spectrum measurement system is carried out, including tunable excited light module, open microcavity photoacoustic cell and low coherent differential interference microphone module, and each module is verified by experiments. Then the whole system is tested. The experimental results show that the resonant frequency of the open microcavity photoacoustic cell is 3 KHz, and the maximum photoacoustic signal is 2.3 MPA. Compared with the traditional electric microphone (BK2192), the signal intensity at the pulse frequency of 6 kHz and 7 kHz is 10.2dB and 9.9 dB higher than that at the pulse frequency of 6kHz and 7kHz, respectively. In the aspect of gas leakage detection, the relevant information of gas tank leakage is judged by picking up the quadrupole sound field signal of gas leakage and distinguishing the characteristic spectrum of gas leakage. The experimental results show that with the change of the internal pressure of the gas tank and the size of the leak hole, the characteristic spectrum of the gas leakage only changes in the whole fluctuation and does not change in the spectrum. This study provides a new method for gas leakage detection.
【學(xué)位授予單位】：安徽大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN253

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