基于Simplex码的BOTDR数字相干探测技术及算法研究

Digital Coherent Detection and Algorithm Research on BOTDR Sensing System with Simplex Code

针对基于Simplex码的BOTDR传感系统相干检测中本地光频率固定的情况,本文提出利用数字相干探测技术方案,设计相关算法,得到传感光纤的三维布里渊散射谱。高速数据采集卡采集每行Simplex码对应的时域信号,转化为数字信号之后在频域进行信号处理与分析。对于所有的编码序列,提取出某频率处所有空间分辨率内的幅度,乘以Simplex码的逆矩阵后进行移位平均,获得该频率处传感光纤的幅度;同理可得到其它频率处的幅度信息;最终获得传感光纤长度上一定频率范围内的幅度信息,即布里渊散射谱。实验中对31位Simplex码的BOTDR系统干涉信号进行数字相干探测,解调出了布里渊散射谱及对应的幅度和频率信息。实验结果表明该探测技术及算法的可行性。

For the fixed frequency of the local oscillator in the coherent detection, digital coherent detection technique and algorithm have been investigated in the Brillouin optical time domain reflectometry （BOTDR） with Simplex code, to obtain the three-dimensional Brillouin scattering spectrum. The time domain signal of every code sequence is collected by the data acquisition card （DAQ）, and then be dealt in the frequency domain according to the algorithm. To all Simplex matrix columns, the amplitude information for a frequency is extracted; and then multiplexed by the Simplex inverse matrix, the amplitude distribution along the sensing fiber is obtained. In the similar way the amplitude for other frequency could also be acquired. So the Brillouin scattering spectrum is constructed. In the experiment digital coherent detection is made for the BOTDR sensing system with 31 bit Simplex code. The Brillouin spectrum and its amplitude and frequency information for 1000m sensing fiber are obtained. Experimental results show the feasibility of the detection technique and algorithm.