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为了实现微流体流场中多点速度测量,提出基于双芯光子晶体光纤的激光多普勒速度计研究。理论分析基于双芯光子晶体光纤的相干特性和控制体特征。计算结果表明纤芯间距为7.4μm,在控制体内可产生5条干涉明纹,与实验结果保持一致。但由于噪声的存在,实验所得各级条纹的强度比值比理论计算结果小。增大纤芯间距,可增加控制体内的干涉条纹数量,从而提高速度测量精度。从双芯光子晶体光纤出射的光斑至相干过程的成像结果表明,速度计的工作距离约30μm。分析基于双芯光子晶体光纤的激光多普勒多点速度测量原理,并进行单点、两点和三点速度测试。单点测量时,粒子平均速度为0.980 m/s,相对不确定度为0.5%;两点测量时,粒子平均速度分别为1.761 m/s、1.769 m/s;三点测量时,粒子平均速度分别为2.106、2.084、2.097 m/s。实验结果表明,基于双芯光子晶体光纤的激光多普勒速度计可进行多点速度测量,而且具有探头微型化、系统简单的特点,因此可嵌入微系统进行流场的多点速度测量。
In order to realize multi-point velocity measurement in microfluidic flow field, a laser Doppler velocimetry study based on dual-core photonic crystal fiber is proposed. The theoretical analysis is based on the coherence properties of the dual-core photonic crystal fiber and the characteristics of the control body. The calculated results show that the distance between the core and the core is 7.4μm, and five interference patterns can be produced in the control body, which are consistent with the experimental results. However, due to the existence of noise, the intensity ratio of the streaks obtained at each experiment is smaller than the theoretical calculation. Increasing the core spacing can increase the number of control fringes in the body, thereby improving the speed measurement accuracy. The imaging results from the two-core photonic crystal fiber to the coherent process show that the working distance of the speedometer is about 30 μm. The principle of laser Doppler multipoint velocity measurement based on dual-core photonic crystal fibers was analyzed and single point, two-point and three-point velocity tests were performed. For single point measurement, the average particle velocity is 0.980 m / s and the relative uncertainty is 0.5%. The average particle velocities are 1.761 m / s and 1.769 m / s at two points measurement. The average particle velocity Respectively, 2.106,2.084,2.097 m / s. The experimental results show that the laser Doppler velocimeter based on dual-core photonic crystal fiber can measure multi-point velocity, miniaturize the probe and simplify the system, so it can embed micro-system to measure multi-point velocity in flow field.