基于多模声波导光纤的布里渊光时域反射技术研究

发布时间：2018-12-28 18:03

【摘要】：布里渊光时域反射(Brillouin optical time-domain reflectometry, BOTDR)技术是一种分布式光纤传感技术,其工作原理在于布里渊散射光的频移和功率均与应变和温度相关,通过测量脉冲光在光纤中传输时产生的后向自发布里渊散射光的频移与功率来实现光纤沿线应变与温度的测量。多模声波导光纤,是指具有复杂折射率分布且有多个声学激发模式的光纤,这些特征决定了在多模声波导光纤中前向传播的单模泵浦光会激发出多个模式的后向布里渊散射光,布里渊增益谱(Brliiouin Gai n Spectrum, BGS)表现为多峰形态。代表不同声学模式的多峰布里渊散射光在后向传播过程中相互作用产生光学拍,会形成峰值频率为百兆赫兹量级的布里渊拍频谱(Brillouin Beat Spectrum, BBS)。本文的研究工作之一,是在基于BBS探测的布里渊光时域反射技术中,提出对任意多模声波导结构光纤的应变与温度系数进行理论计算的方法。该计算方法可筛选用于基于BBS的光纤传感系统中的高灵敏度光纤,并用于指导设计高应变与高温度灵敏度的多模声波导光纤。本文的另外一个研究工作,是将拉曼放大与零差BOTDR相结合,设计了基于拉曼放大的零差BOTDR系统。提出了一种基于拉曼放大的零差布里渊光时域反射技术,在实现对应变和温度快速单端测量的同时,可实现传感距离或测量精度的提高。该方法通过拉曼放大提高多峰布里渊谱的峰值功率,实现布里渊拍频峰功率的提升,可有效提高传感系统的信噪比(signal-to-noise ratio, SNR)和传感距离。仿真结果表明,所提出的方法在不降低测量精度和测量速度的情况下,在本文的测量条件下可使光纤传感的距离提高11倍。
[Abstract]:Brillouin optical time domain reflectance (Brillouin optical time-domain reflectometry, BOTDR) technology is a distributed optical fiber sensing technology. Its working principle is that the frequency shift and power of Brillouin scattering light are dependent on strain and temperature. The strain and temperature along the fiber are measured by measuring the frequency shift and the power of the self-released Brillouin scattering light generated by the pulse light propagating in the fiber. Multimode acoustic waveguide fiber is a fiber with complex refractive index distribution and multiple acoustic excitation modes. These characteristics determine that single mode pumping light propagating forward in multimode acoustic waveguide fiber can excite multiple modes of Brillouin scattering light. Brillouin gain spectrum (Brliiouin Gai n Spectrum, BGS) shows multi-peak morphology. The interaction of multi-peak Brillouin scattering light representing different acoustic modes produces optical beat during backward propagation, which results in the formation of Brillouin beat spectrum (Brillouin Beat Spectrum, BBS). With a peak frequency of 100 megahertz. In the Brillouin optical time domain reflectance technique based on BBS detection, a theoretical calculation method for strain and temperature coefficients of arbitrary multimode acoustic waveguide fiber is presented in this paper. This method can be used to screen high-sensitivity optical fibers in the optical fiber sensing system based on BBS and to guide the design of multi-mode acoustic waveguide fibers with high strain and high temperature sensitivity. Another work of this paper is to design a BOTDR system based on Raman amplification by combining Raman amplification with homodyne BOTDR. A novel optical time domain reflectance technique based on Raman amplification is proposed. The sensing distance or measurement precision can be improved by fast single end measurement of strain and temperature. In this method, the peak power of Brillouin spectrum is increased by Raman amplification, and the peak power of Brillouin beat frequency is raised. The signal-to-noise ratio (signal-to-noise ratio, SNR) and sensing distance of the sensing system can be improved effectively. The simulation results show that the proposed method can increase the optical fiber sensing distance by 11 times without reducing the measurement accuracy and measuring speed.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253

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