脈沖編碼多模激光器BOTDR系統(tǒng)建模分析與優(yōu)化設計
發(fā)布時間：2019-07-08 11:01
【摘要】：本文在闡述布里淵光時域反射(BOTDR)技術研究現(xiàn)狀的基礎上,對光纖布里淵散射理論,包括自發(fā)布里淵散射和受激布里淵散射機理進行了分析,同時介紹了利用布里淵頻移和強度實現(xiàn)溫度和應變同時測量的原理。研究了外差檢測脈沖編碼BOTDR系統(tǒng),分別介紹了Golay碼、Simplex碼和CCPONS碼應用于移頻外差檢測BOTDR系統(tǒng)的編解碼原理及編碼增益,用MATLAB對三種不同碼型編碼系統(tǒng)時域輸出信號進行仿真對比,并對比分析了編碼長度和疊加平均次數(shù)增加時的信噪比改善效果。分別提出了基于窄譜DFB激光器單波長、三波長和多模FP激光器的APD外差檢測Golay編碼BOTDR系統(tǒng),分析了三種系統(tǒng)編解碼原理及外差檢測原理,討論了光纖受激布里淵散射閾值對編碼長度的限制問題,并推導了系統(tǒng)信噪比的數(shù)學表達式;研究了系統(tǒng)信噪比與APD倍增因子、編碼長度和縱模數(shù)之間的相互制約關系,分別得到了APD最佳倍增因子、最佳編碼長度和最佳縱模數(shù)的表達式,選用帶寬為500 MHz的APD光電檢測器和峰值功率50 mW、脈沖寬度100 ns的入纖脈沖時,分別對提出的三種系統(tǒng)進行建模分析和優(yōu)化設計并用MATLAB對系統(tǒng)性能進行仿真驗證。結果表明,為了實現(xiàn)高精度傳感,除了要考慮光纖受激布里淵散射對編碼長度的限制問題、信號功率過大造成的APD光電檢測器飽和的問題,還需根據(jù)實際系統(tǒng)考慮激光器類型、接收機帶寬等其他因素,權衡各個參數(shù)來確定最佳APD倍增因子、最佳編碼長度和最佳縱模數(shù)。對于單頻編碼BOTDR系統(tǒng),選取APD倍增因子為5,編碼長度128位時可獲得最佳的溫度和應變分辨率1.60℃和35.48??;對于三波長編碼系統(tǒng),APD倍增因子為5,編碼長度64位時可獲得最佳的溫度和應變分辨率1.33℃和29.49??;對于多模編碼系統(tǒng),APD倍增因子為5,編碼長度32位,縱模數(shù)為7時可獲得最佳的溫度和應變分辨率1.29℃和29.16??。
文內圖片：
圖片說明：自發(fā)布里淵散射過程示意圖
[Abstract]:On the basis of expounding the research status of Brillouin optical time domain reflection (BOTDR) technology, this paper analyzes the Brillouin scattering theory of optical fiber, including the mechanism of self-published Brillouin scattering and stimulated Brillouin scattering, and introduces the principle of simultaneous measurement of temperature and strain by Brillouin frequency shift and intensity. The pulse coding BOTDR system of heterodyne detection is studied. The coding and decoding principle and coding gain of Golay code, Simplex code and CCPONS code applied to frequency shift heterodyne detection BOTDR system are introduced respectively. The time domain output signals of three different code coding systems are simulated and compared with MATLAB, and the signal to noise ratio (SNR) improvement effect with the increase of coding length and superposition average number is compared and analyzed. The APD heterodyne detection Golay encoded BOTDR system based on narrow spectrum DFB laser single wavelength, three wavelength and multimode FP laser is proposed respectively. the coding and decoding principles and heterodyne detection principles of the three systems are analyzed. The limitation of fiber stimulated Brillouin scattering threshold to the coding length is discussed, and the mathematical expression of the signal to noise ratio of the system is derived. The relationship between signal-to-noise ratio (SNR) and APD multiplication factor, coding length and longitudinal modulus is studied. The expressions of optimal multiplication factor, optimal coding length and optimal longitudinal modulus of APD are obtained respectively. The APD photodetector with bandwidth of 500 MHz and the input pulse with peak power of 50 mW, pulse width of 100 ns are selected. The three proposed systems are modeled, analyzed and optimized, and the performance of the system is verified by MATLAB simulation. The results show that in order to realize high precision sensing, in addition to the limitation of fiber stimulated Brillouin scattering to coding length and the saturation of APD photodetector caused by excessive signal power, it is necessary to weigh the parameters to determine the optimal APD multiplication factor, optimal coding length and optimal longitudinal modulus according to other factors such as laser type, receiver bandwidth and so on. For single-frequency coding BOTDR system, the best temperature and strain resolution can be obtained when the APD multiplication factor is 5, and the best temperature and strain resolution can be obtained when the coding length is 128 bits, and the best temperature and strain resolution can be obtained when the APD multiplication factor is 5 and the coding length is 64 bits for the three-wavelength coding system, and the best temperature and strain resolution can be obtained when the coding length is 128 bits, and the best temperature and strain resolution can be obtained at 1.60 鈩，
本文編號：2511540
文內圖片：
圖片說明：自發(fā)布里淵散射過程示意圖
[Abstract]:On the basis of expounding the research status of Brillouin optical time domain reflection (BOTDR) technology, this paper analyzes the Brillouin scattering theory of optical fiber, including the mechanism of self-published Brillouin scattering and stimulated Brillouin scattering, and introduces the principle of simultaneous measurement of temperature and strain by Brillouin frequency shift and intensity. The pulse coding BOTDR system of heterodyne detection is studied. The coding and decoding principle and coding gain of Golay code, Simplex code and CCPONS code applied to frequency shift heterodyne detection BOTDR system are introduced respectively. The time domain output signals of three different code coding systems are simulated and compared with MATLAB, and the signal to noise ratio (SNR) improvement effect with the increase of coding length and superposition average number is compared and analyzed. The APD heterodyne detection Golay encoded BOTDR system based on narrow spectrum DFB laser single wavelength, three wavelength and multimode FP laser is proposed respectively. the coding and decoding principles and heterodyne detection principles of the three systems are analyzed. The limitation of fiber stimulated Brillouin scattering threshold to the coding length is discussed, and the mathematical expression of the signal to noise ratio of the system is derived. The relationship between signal-to-noise ratio (SNR) and APD multiplication factor, coding length and longitudinal modulus is studied. The expressions of optimal multiplication factor, optimal coding length and optimal longitudinal modulus of APD are obtained respectively. The APD photodetector with bandwidth of 500 MHz and the input pulse with peak power of 50 mW, pulse width of 100 ns are selected. The three proposed systems are modeled, analyzed and optimized, and the performance of the system is verified by MATLAB simulation. The results show that in order to realize high precision sensing, in addition to the limitation of fiber stimulated Brillouin scattering to coding length and the saturation of APD photodetector caused by excessive signal power, it is necessary to weigh the parameters to determine the optimal APD multiplication factor, optimal coding length and optimal longitudinal modulus according to other factors such as laser type, receiver bandwidth and so on. For single-frequency coding BOTDR system, the best temperature and strain resolution can be obtained when the APD multiplication factor is 5, and the best temperature and strain resolution can be obtained when the coding length is 128 bits, and the best temperature and strain resolution can be obtained when the APD multiplication factor is 5 and the coding length is 64 bits for the three-wavelength coding system, and the best temperature and strain resolution can be obtained when the coding length is 128 bits, and the best temperature and strain resolution can be obtained at 1.60 鈩，
本文編號：2511540
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