外差BOTDA中相位解調(diào)系統(tǒng)的設(shè)計(jì)與實(shí)現(xiàn)
發(fā)布時間：2018-09-06 13:01
【摘要】：本文在綜述布里淵光時域分析(BOTDA)技術(shù)研究現(xiàn)狀的基礎(chǔ)上,論述了自發(fā)布里淵散射(SPBS)和受激布里淵散射(SBS)的作用機(jī)理,根據(jù)受激布里淵散射的作用機(jī)理,分析了布里淵頻移受溫度和應(yīng)變影響的特性,研究了布里淵頻移與光纖溫度和應(yīng)變的對應(yīng)關(guān)系。介紹了傳統(tǒng)的直接檢測BOTDA系統(tǒng)原理和可以同時檢測布里淵幅度和相移的外差BOTDA系統(tǒng)原理,對比分析了兩種系統(tǒng),推導(dǎo)了受激布里淵散射作用傳輸函數(shù)和兩種系統(tǒng)輸出信號的信噪比表達(dá)式。在分析外差BOTDA系統(tǒng)的基礎(chǔ)上,深入研究了布里淵相位的解調(diào)方法,設(shè)計(jì)了模擬相位解調(diào)系統(tǒng)和數(shù)字相位解調(diào)系統(tǒng)。在Simulink系統(tǒng)中搭建了模擬相位解調(diào)系統(tǒng)模型,仿真實(shí)現(xiàn)了對射頻信號和本振信號的相位差提取。針對模擬相位解調(diào)系統(tǒng)中由于正交解調(diào)模塊AD0105B中的硬件結(jié)構(gòu)、系統(tǒng)中AOM的頻率不穩(wěn)定性引起的誤差提出了相應(yīng)的解決辦法。使用Labview軟件搭建了數(shù)字相位解調(diào)仿真平臺,在此平臺上使用過零檢測法、相關(guān)檢測法以及I/Q正交檢測法實(shí)現(xiàn)了對相位差信息的提取,并在不同噪聲條件下分析了三種方法的性能:小噪聲條件下,過零檢測法受噪聲影響較大,相關(guān)檢測法、I/Q正交檢測法基本不受影響,保持較好的解調(diào)精度;大噪聲條件下,過零檢測法受噪聲影響很大,喪失解調(diào)能力,相關(guān)檢測法發(fā)生邊緣漂移現(xiàn)象,解調(diào)精度降低,I/Q正交檢測法受影響較小,依然保持較高的解調(diào)精度。后期針對三種數(shù)字解調(diào)算法提出了相應(yīng)的優(yōu)化方案:在過零檢測法中,加入疊加平均過程,實(shí)現(xiàn)在噪聲環(huán)境中提取高精度相位差信息;在相關(guān)檢測法中,提出迭代相關(guān)檢測方案,極大的提高了算法的抗噪聲能力,適用于低信噪比信號中精確提取相位信息。在I/Q正交檢測法中,對數(shù)據(jù)進(jìn)行全相位預(yù)處理過程,解決了I/Q正交檢測法檢測非整周期序列時存在的頻譜泄露問題。
[Abstract]:Based on the review of the research status of Brillouin optical time domain analysis (BOTDA) technology, the mechanism of self-releasing Brillouin scattering (SPBS) and stimulated Brillouin scattering (SBS) is discussed in this paper, according to the mechanism of stimulated Brillouin scattering. The effect of temperature and strain on Brillouin frequency shift is analyzed, and the relationship between Brillouin frequency shift and fiber temperature and strain is studied. This paper introduces the principle of traditional direct detection BOTDA system and heterodyne BOTDA system which can detect Brillouin amplitude and phase shift simultaneously. The transfer function of stimulated Brillouin scattering and the expression of signal-to-noise ratio of the output signals of the two systems are derived. Based on the analysis of heterodyne BOTDA system, the method of Brillouin phase demodulation is studied, and the analog phase demodulation system and digital phase demodulation system are designed. An analog phase demodulation system model is built in Simulink system, and the phase difference between RF signal and local oscillator signal is extracted by simulation. This paper presents a solution to the error caused by the frequency instability of AOM in the analog phase demodulation system due to the hardware structure of the quadrature demodulation module (AD0105B) and the frequency instability of the AOM in the system. The digital phase demodulation simulation platform is built with Labview software. The zero-crossing detection method, the correlation detection method and the I / Q orthogonal detection method are used to extract the phase difference information on the platform. At the same time, the performance of three methods is analyzed under different noise conditions: under the condition of small noise, the zero crossing detection method is greatly affected by noise, the correlation detection method I / Q orthogonal detection method is basically unaffected, and the demodulation accuracy is better under the condition of large noise. The zero-crossing detection method is greatly affected by the noise and loses the demodulation ability. The correlation detection method has the phenomenon of edge drift. The demodulation accuracy is reduced and the I / Q quadrature detection method is less affected, and the demodulation accuracy is still high. In the later stage, three digital demodulation algorithms are proposed: in the zero-crossing detection method, the superposition average process is added to extract the high-precision phase difference information in the noise environment, and in the correlation detection method, the phase difference information is extracted in the noise environment. An iterative correlation detection scheme is proposed, which greatly improves the anti-noise ability of the algorithm and is suitable for extracting phase information accurately in low SNR signals. In the I / Q orthogonal detection method, the whole phase preprocessing process of the data is carried out, which solves the spectrum leakage problem in the detection of non-integer periodic sequences by the I / Q orthogonal detection method.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TP212
本文編號：2226426
[Abstract]:Based on the review of the research status of Brillouin optical time domain analysis (BOTDA) technology, the mechanism of self-releasing Brillouin scattering (SPBS) and stimulated Brillouin scattering (SBS) is discussed in this paper, according to the mechanism of stimulated Brillouin scattering. The effect of temperature and strain on Brillouin frequency shift is analyzed, and the relationship between Brillouin frequency shift and fiber temperature and strain is studied. This paper introduces the principle of traditional direct detection BOTDA system and heterodyne BOTDA system which can detect Brillouin amplitude and phase shift simultaneously. The transfer function of stimulated Brillouin scattering and the expression of signal-to-noise ratio of the output signals of the two systems are derived. Based on the analysis of heterodyne BOTDA system, the method of Brillouin phase demodulation is studied, and the analog phase demodulation system and digital phase demodulation system are designed. An analog phase demodulation system model is built in Simulink system, and the phase difference between RF signal and local oscillator signal is extracted by simulation. This paper presents a solution to the error caused by the frequency instability of AOM in the analog phase demodulation system due to the hardware structure of the quadrature demodulation module (AD0105B) and the frequency instability of the AOM in the system. The digital phase demodulation simulation platform is built with Labview software. The zero-crossing detection method, the correlation detection method and the I / Q orthogonal detection method are used to extract the phase difference information on the platform. At the same time, the performance of three methods is analyzed under different noise conditions: under the condition of small noise, the zero crossing detection method is greatly affected by noise, the correlation detection method I / Q orthogonal detection method is basically unaffected, and the demodulation accuracy is better under the condition of large noise. The zero-crossing detection method is greatly affected by the noise and loses the demodulation ability. The correlation detection method has the phenomenon of edge drift. The demodulation accuracy is reduced and the I / Q quadrature detection method is less affected, and the demodulation accuracy is still high. In the later stage, three digital demodulation algorithms are proposed: in the zero-crossing detection method, the superposition average process is added to extract the high-precision phase difference information in the noise environment, and in the correlation detection method, the phase difference information is extracted in the noise environment. An iterative correlation detection scheme is proposed, which greatly improves the anti-noise ability of the algorithm and is suitable for extracting phase information accurately in low SNR signals. In the I / Q orthogonal detection method, the whole phase preprocessing process of the data is carried out, which solves the spectrum leakage problem in the detection of non-integer periodic sequences by the I / Q orthogonal detection method.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TP212
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