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  本文選題：氣體傳感　切入點：光譜吸收　出處：《武漢理工大學(xué)》2015年博士論文

【摘要】：光學(xué)氣體檢測在環(huán)境污染、工業(yè)過程控制、醫(yī)療診斷等領(lǐng)域應(yīng)用較廣�；诠庾V吸收的氣體檢測技術(shù)是通過檢測樣氣透射光強的變化來實現(xiàn)氣體濃度的測量。與傳統(tǒng)方式相比,該技術(shù)具有高精度、低交叉敏感、快速響應(yīng),易于成網(wǎng)等優(yōu)點。其中窄帶光譜吸收技術(shù)采用低成本的寬帶光源,且可以利用濾波器選擇不同的吸收峰實現(xiàn)不同氣體的檢測,具有非常好的工業(yè)應(yīng)用潛質(zhì)。本文提出了基于共軛干涉濾波的光學(xué)氣體傳感方法,該方法是利用光譜吸收和雙光束干涉,實現(xiàn)了共軛干涉濾波器,該濾波器能通過對應(yīng)吸收氣體吸收光譜的光,而反射其他波長的光,從而獲得與氣體吸收譜線反轉(zhuǎn)的梳狀光譜。由于氣體吸收譜線本質(zhì)穩(wěn)定的特性,濾波器將輸出穩(wěn)頻的梳狀光譜,并且通過更換濾波器中氣體種類能輸出對應(yīng)氣體的輸出光譜。該方法能有效的壓縮寬帶光源的譜寬,大大提高氣體檢測靈敏度,且能解決氣體檢測中選擇光源的問題。首先,以分子光譜理論、比爾朗伯定律為基礎(chǔ),分析了氣體吸收線的譜線(線型、線寬、展寬)等理論,研究了基于光譜吸收的氣體濃度檢測技術(shù)。根據(jù)HITRAN數(shù)據(jù)庫以及傅里葉紅外光譜儀對氣體吸收譜線的相關(guān)參數(shù)進(jìn)行了確定。研究了溫度、壓力等因素對譜線展寬以及吸收系數(shù)的影響,為選擇濾波器的物理參數(shù)提供了理論依據(jù)。其次,研究了共軛干涉式濾波器π相移實現(xiàn)方法的研究。通過對共軛干涉式濾波器結(jié)構(gòu)的設(shè)計、比較以及討論,確定其結(jié)構(gòu)。并通過對輸出光強的仿真、實驗比較對濾波器參數(shù)進(jìn)行確定,從而最終能輸出穩(wěn)定的π相移濾波輸出。再次,研究了基于共軛干涉式濾波器的窄帶穩(wěn)定輸出光源,包括線性腔單波長、多波長窄帶光源,以及基于光纖環(huán)形腔的單波長、多波長窄帶輸出光源。該窄帶光源的輸出光能完全對應(yīng)氣體吸收峰的窄線寬以及中心波長,光強穩(wěn)定,能有效的應(yīng)用在(多)氣體濃度檢測上。最后,本文基于差分檢測方案以及共軛干涉式濾波器的穩(wěn)頻輸出光構(gòu)建了單一氣體檢測系統(tǒng)以及多氣體檢測系統(tǒng)。對系統(tǒng)中的窄帶光源、吸收氣室、數(shù)據(jù)處理等關(guān)鍵器件以及關(guān)鍵技術(shù)進(jìn)行分析。并設(shè)計了一種基于光纖空芯光子晶體光纖的氣室結(jié)構(gòu),給低損耗、長光程氣室提供方向。與此同時還采用了氣體傳感系統(tǒng)微弱信號的檢測方法,能有效抑制噪聲,實現(xiàn)輸出信號的光譜重現(xiàn),實驗結(jié)果表明,氣體檢測的靈敏度和信噪比得到明顯的提高。對單一氣體和多氣體共存情況下作了氣體檢測的實驗,驗證了該基于共軛干涉式濾波器的光纖氣體傳感系統(tǒng),在多種氣體混合環(huán)境下,可以完成對不同組分氣體濃度的檢測。
[Abstract]:Optical gas detection is widely used in the fields of environmental pollution, industrial process control, medical diagnosis and so on. The gas detection technology based on spectral absorption realizes the measurement of gas concentration by detecting the change of transmitted light intensity of sample gas. This technique has the advantages of high precision, low cross-sensitivity, fast response and easy netting. The narrow-band spectral absorption technology uses a low cost broadband light source, and the filter can be used to select different absorption peaks to realize the detection of different gases. In this paper, an optical gas sensing method based on conjugate interferometric filtering is proposed. The conjugate interferometer filter is realized by using spectral absorption and two-beam interference. The filter can reflect the light of other wavelengths by absorbing the absorption spectrum of the gas, thus obtaining the comb spectrum which is reversed from the absorption line of the gas, because of the intrinsic stability of the absorption line of the gas, The filter will output the comb spectrum of steady frequency and output spectrum of the corresponding gas by changing the kind of gas in the filter. This method can effectively compress the spectrum width of the broadband light source and greatly improve the sensitivity of gas detection. And it can solve the problem of choosing light source in gas detection. Firstly, based on the theory of molecular spectrum and Bill Lambert's law, the theory of spectrum line (line type, line width, broadening) of gas absorption line is analyzed. The technology of gas concentration detection based on spectral absorption is studied. The parameters of gas absorption spectrum line are determined by HITRAN database and Fourier transform infrared spectrometer. The temperature is studied. The influence of pressure and other factors on spectral line broadening and absorption coefficient provides a theoretical basis for selecting the physical parameters of the filter. The realization method of 蟺 phase shift of conjugate interferometric filter is studied. The structure of conjugate interferometric filter is determined by designing, comparing and discussing its structure. The parameters of the filter are determined experimentally, so that the stable 蟺 phase shift filter output can be output. Thirdly, the narrow band stable output light source based on conjugate interference filter is studied, including linear cavity single wavelength source and multi wavelength narrow band light source. And the single wavelength and multi wavelength narrow band output light source based on fiber ring cavity. The output energy of the narrow band light source completely corresponds to the narrow line width and center wavelength of the gas absorption peak, and the light intensity is stable. Can be used effectively in gas concentration detection. Finally, In this paper, a single gas detection system and a multi-gas detection system are constructed based on the differential detection scheme and the stable output light of the conjugate interferometric filter. The key devices such as data processing and key technologies are analyzed, and a kind of gas chamber structure based on optical fiber hollow photonic crystal fiber is designed to reduce the loss. At the same time, the weak signal detection method of the gas sensing system is adopted, which can effectively suppress the noise and realize the spectral reproduction of the output signal. The experimental results show that, The sensitivity and signal-to-noise ratio of gas detection have been improved obviously. The experiment of gas detection under the condition of the coexistence of single gas and multi-gas is carried out, which verifies the fiber optic gas sensing system based on conjugate interferometric filter. The concentration of different gas components can be detected in the environment of multiple gas mixtures.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TN713

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