The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry （BOTDR） are investigated numerically and experimentally. Simulation results show that the spectral linewi...The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry （BOTDR） are investigated numerically and experimentally. Simulation results show that the spectral linewidth of spontaneous Brillouin scattering remains almost constant when the laser linewidth is less than 1 MHz at the same pulse width; otherwise, it increases sharply. A comparison between a fiber laser （FL） with 4-kHz linewidth at 3 dB and a distributed feedback （DFB） laser with 3-MHz linewidth is made experimentally. When a constant laser power is launched into the sensing fiber, the fitting linewidths of the beat signals （backscattered Brillouin light and local oscillator （LO）） is about 5 MHz wider for the DFB laser than for the FL and the intensity of the beat signal is about a half. Furthermore, the frequency fluctuation in the long sensing fiber is lower for the FL source, yielding about 2 MHz less than that of the DFB laser, indicating higher temperature/strain resolution. The experimental results are in good agreement with the numerical simulations.展开更多
A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linew...A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linewidth and the exponential gain coefficient, is obtained by the calculated data fitting. The formula holds true for two cases involving pump undepletion and depletion. The lineshape change from spontaneous to highly pump-depleted SBS spectra is also investigated. The result shows that for the pump power below the SBS threshold, the Stokes output spectral lincshape evolves from Lorentzian to approximately Gaussian as the pump power increases. For the pump power near or beyond the threshold, the SBS spectrum is in the form of a steady Gaussian profile, and the spectral linewidth comes to a certain value about 7 times narrower than the spontaneous one. The theoretical results are experimentally demonstrated by using several common liquid media.展开更多
理论分析了线宽对受激布里渊散射阈值的影响,使用噪声信号直接调制分布反馈半导体激光器构成可调线宽激光光源,搭建了受激布里渊散射阈值测量系统.结果表明,可调线宽激光的频谱与所使用的噪声信号的频谱类似,光谱与分布反馈半导体激光...理论分析了线宽对受激布里渊散射阈值的影响,使用噪声信号直接调制分布反馈半导体激光器构成可调线宽激光光源,搭建了受激布里渊散射阈值测量系统.结果表明,可调线宽激光的频谱与所使用的噪声信号的频谱类似,光谱与分布反馈半导体激光器输出光的光谱相比明显展宽.当可调线宽激光光源使用400 m V噪声信号进行调制时,长度为900 m单模光纤的受激布里渊散射阈值为616 m W,与使用DFB激光器测量的106 m W阈值相比,提高了7.6 d B.因此,可调线宽激光光源可以提高光纤的受激布里渊散射阈值,增加长距离光纤通信和光载电能传输系统中的光功率.展开更多
基金the National High Technology Research and Development Program of China(Grant No.2012AA041203)the Science and Technology Commission of Shanghai Municipality,China(Grant No.13XD1425400)the Pudong New Area Science and Technology Development Fund,China(Grant No.PKJ2012-D04)
文摘The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry （BOTDR） are investigated numerically and experimentally. Simulation results show that the spectral linewidth of spontaneous Brillouin scattering remains almost constant when the laser linewidth is less than 1 MHz at the same pulse width; otherwise, it increases sharply. A comparison between a fiber laser （FL） with 4-kHz linewidth at 3 dB and a distributed feedback （DFB） laser with 3-MHz linewidth is made experimentally. When a constant laser power is launched into the sensing fiber, the fitting linewidths of the beat signals （backscattered Brillouin light and local oscillator （LO）） is about 5 MHz wider for the DFB laser than for the FL and the intensity of the beat signal is about a half. Furthermore, the frequency fluctuation in the long sensing fiber is lower for the FL source, yielding about 2 MHz less than that of the DFB laser, indicating higher temperature/strain resolution. The experimental results are in good agreement with the numerical simulations.
基金Project supported by the National Natural Science Foundation of China (Grant No 60778019)the Program of Excellent Teamin Harbin Institute of Technology, Chinathe Program of Science and Technology of Education the Bureau of Heilongjiang Province, China (Grant No 11521048)
文摘A theoretical model for calculating spontaneous and stimulated Brillouin scattering（SBS） spectra is described. An empirical formula for the Stokes output spectral linewidth, a function of spontaneous Brillouin linewidth and the exponential gain coefficient, is obtained by the calculated data fitting. The formula holds true for two cases involving pump undepletion and depletion. The lineshape change from spontaneous to highly pump-depleted SBS spectra is also investigated. The result shows that for the pump power below the SBS threshold, the Stokes output spectral lincshape evolves from Lorentzian to approximately Gaussian as the pump power increases. For the pump power near or beyond the threshold, the SBS spectrum is in the form of a steady Gaussian profile, and the spectral linewidth comes to a certain value about 7 times narrower than the spontaneous one. The theoretical results are experimentally demonstrated by using several common liquid media.
文摘理论分析了线宽对受激布里渊散射阈值的影响,使用噪声信号直接调制分布反馈半导体激光器构成可调线宽激光光源,搭建了受激布里渊散射阈值测量系统.结果表明,可调线宽激光的频谱与所使用的噪声信号的频谱类似,光谱与分布反馈半导体激光器输出光的光谱相比明显展宽.当可调线宽激光光源使用400 m V噪声信号进行调制时,长度为900 m单模光纤的受激布里渊散射阈值为616 m W,与使用DFB激光器测量的106 m W阈值相比,提高了7.6 d B.因此,可调线宽激光光源可以提高光纤的受激布里渊散射阈值,增加长距离光纤通信和光载电能传输系统中的光功率.
