分布式光纤传感双通道调制光源设计与测试

Design and test of dual-channel light sources for distributed optical fiber sensing

为了满足布里渊光时域分析(BOTDA)光纤传感系统需要频差为布里渊频移的两种激光输出光源的需求,采用布里渊环形腔频移和电光调制的方法设计了双通道光源系统。根据光源的脉冲宽度、重复频率、扫频量等参量,对双通道调制光谱输出进行了仿真,并采用现场可编程门阵列配合直接数字式频率合成器技术的方案建立了系统实验装置,实现了脉冲探测光和扫频抽运光两种激光输出。脉冲探测光输出最小脉宽达10ns,扫频抽运光输出扫频范围达0MHz^90MHz,扫描频率步进值为30Hz,时间步进为1.6μs。结果表明,该光源技术参量满足BOTDA系统的要求,不需引入高频微波信号源等高速器件,信号采集模块可采用100MHz以下光电探测器件实现,降低了系统成本。

For the purpose that a fiber sensor system of Brillouin optical time-domain analysis（ BOTDA） needs two light sources of Brillouin frequency shift,a dual-channel light source system was proposed by employing Brillouin ring cavity frequency shift and electro-optic modulation. According to several parameters,pulse width,repetition frequency rate and step of frequency sweeping,the output light spectrum of dual-channel modulation was simulated. Based on field programmable gate array（ FPGA） and direct digital synthesizer（ DDS） chip,experimental system was setup and both pulse detect light and sweep frequency pulse light could be output from the setup. The minimum pulse width of the detection pulse was 10 ns,and the sweep frequency range reached 0MHz - 90 MHz with a frequency sweep step of 30 Hz and a time step of 1. 6μs. Experimental results show that the dual channel light source can meet the demands of general BOTDA systems,without the necessity of some high speed devices,such as high frequency microwave signal source. Signal acquisition modules can adopt regular photoelectric detectors below 100 MHz so as to reduce the system cost.