基于分布式布里渊放大的长距离BOTDA光纤传感研究

发布时间：2018-06-18 05:43

本文选题：分布式光纤传感 + 布里渊光时域分析　；参考：《四川师范大学》2017年硕士论文

【摘要】：受激布里渊散射(SBS)在分布式光纤传感、光纤激光器、微波光子学等领域得到了广泛应用。本文概述了基于SBS的布里渊光时域分析(BOTDA)传感系统的关键问题及研究进展;介绍了BOTDA系统涉及的关键器件;提出了三种基于频率梳分布式布里渊放大(DBA)泵浦的长距离BOTDA新结构及一种基于频率梳脉冲的高空间分辨相干BOTDA新结构,并系统研究了其传感特性。具体总结如下:(1)针对基于DBA的长距离BOTDA中,独立DBA泵浦源频率漂移对系统稳定性的影响,提出一种基于一阶DBA泵浦的BOTDA新结构,有效降低了频率漂移对传感稳定性的影响。验证了光脉冲编码(OPC)技术用于该系统的可行性;将频率梳技术应用于该系统以扩展脉冲增益谱,从而有效抑制了脉冲失真所致的测量误差;具体研究了暂态增益(TG)波动对传感性能的影响。研究表明:在脉宽较小的DBA-BOTDA系统中,若使用足够数量的频率梳,则可使出射脉冲形状趋于初始状态;频率梳数量、编码脉冲间隔和编码长度需进行一定的优化,才能使TG波动处于可接受的范围内以控制解码误差。相关研究内容以第一作者发表于《IEEE Photonics Technology Letters》。(2)提出一种基于二阶DBA泵浦的长距离BOTDA传感新方案。相比基于一阶DBA泵浦的BOTDA系统,可获取更平坦的增益分布,提高信噪比~3dB。并且对一阶DBA泵浦、二阶DBA泵浦和脉冲光的功率分布进行了数值模拟,实验测得的脉冲光功率分布与模拟结果吻合较好。最后在实验上利用仅~6dBm二阶泵浦及~1.5dBm一阶泵浦功率(比基于分布式拉曼放大(DRA)的长距离BOTDA系统所需泵浦功率降低两个数量级),高效实现了~99km传感距离、5m空间分辨率。相关研究内容以第二作者发表于《Optics Express》。(3)研究了基于频率梳DBA泵浦的相干BOTDA长距离传感特性。系统引入相干检测可一次性对多个探测频率梳同时解调,加快了数据采集速度;利用频率梳DBA泵浦本身作为探测光,可使脉冲仅受频率梳泵浦的宽带增益,从而避免了脉冲波形及功率的频移相关性,显著抑制了长距离传感的非局域效应。在实验上使用~1.5dBm的DBA泵浦和~10dBm的脉冲光实现了~74.2km的传感。(4)在频率梳DBA泵浦的相干BOTDA基础上,针对双边带(DSB)频率梳脉冲导致的非线性效应对布里渊增益谱(BGS)重构的影响,提出了仅利用其中一个脉冲边带的传感新结构。研究表明:在基于DSB的频率梳脉冲BOTDA系统中,过高峰值功率引起的边带间非线性作用会导致BGS分裂;使用其中一个边带可抑制该非线性效应对BGS重构的影响;该结构与相移脉冲(PSP)相结合可实现高空间分辨传感。实验上,在~592m的光纤上实现了空间分辨率为~60cm的传感。研究内容(3)、(4)以第二作者发表于《Optics Express》。
[Abstract]:Stimulated Brillouin scattering (SBS) has been widely used in distributed optical fiber sensing, fiber laser, microwave photonics and so on. In this paper, the key problems and research progress of Brillouin optical time domain analysis (BOTDA) sensing system based on SBS are summarized, and the key devices involved in BOTDA system are introduced. Three novel structures of long distance BOTDA pumped by frequency comb distributed Brillouin amplification (DBA) and a new structure of high spatial resolution coherent BOTDA based on frequency comb pulses are proposed. The following is summarized as follows: (1) aiming at the effect of frequency drift of independent DBA pump source on system stability in DBA based long distance BOTDA, a new BOTDA structure based on first-order DBA pumping is proposed, which can effectively reduce the influence of frequency drift on sensing stability. The feasibility of using the optical pulse coding (OPC) technique in the system is verified, and the frequency comb technique is applied to the system to expand the pulse gain spectrum, thus effectively reducing the measurement error caused by the pulse distortion. The effect of transient gain TG fluctuation on the sensing performance is studied in detail. The results show that in DBA-BOTDA system with small pulse width, if a sufficient number of frequency combs are used, the shape of the outgoing pulse tends to the initial state, and the number of the frequency comb, the coding pulse interval and the coding length need to be optimized to a certain extent. In order to make TG fluctuation within acceptable range to control decoding error. A novel scheme for long distance BOTDA sensing based on second-order DBA pumping is proposed by the first author in IEEE Photonics Technology Letters >. Compared with the BOTDA system pumped by first order DBA, the gain distribution can be obtained more flat and the SNR can be improved by 3 dB. The power distributions of first-order DBA pumping, second-order DBA pumping and pulse light are numerically simulated, and the experimental results are in good agreement with the simulation results. Finally, using only 6 dBm second-order pumping power and 1.5dBm first-order pumping power (two orders of magnitude less than that required for long distance BOTDA systems based on distributed Raman amplification DRAs), the spatial resolution of 99km sensing distance is realized efficiently. In this paper, the long range sensing characteristics of coherent BOTDA pumped by frequency comb DBA are studied by the second author in < Optics Express >. The system introduces coherent detection to demodulate multiple probe frequency combs at the same time, which accelerates the data acquisition speed. Using the frequency comb DBA pump itself as the detection light, the pulse can only be pumped by the broadband gain of the frequency comb pump. Thus, the correlation of pulse waveform and power shift is avoided, and the nonlocal effect of long distance sensing is significantly suppressed. In the experiment, we use DBA pump of 1.5dBm and pulse light of 10dBm to realize the sensing of 74.2km. On the basis of coherent BOTDA pumped by frequency comb DBA, the effect of nonlinear effect caused by the frequency comb pulse on the reconstruction of Brillouin gain spectrum (BGSs) is studied. A novel sensing structure using only one pulse sideband is proposed. The results show that in DSB-based frequency comb pulse BOTDA system, the nonlinear interaction between the sideband caused by excessive peak power will lead to BGS splitting, and one of the sideband can restrain the influence of the nonlinear effect on the BGS reconstruction. The structure combined with PSPs can realize high spatial resolution sensing. In the experiment, the sensor with spatial resolution of 60 cm is realized on the optical fiber of 592 m. The study was published in the second author, Optics Express.
【学位授予单位】：四川师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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