We present the design and characteristics of laser Doppler differential velocimeter using a dual-core photonic crystal fiber (DC-PCF). Transmission modes and mode interference characteristics of DC-PCF were investigated. Results show that higher order modes and cladding modes are excited, which can be cut off by bending the DC-PCF. The independent fundamental modes of two cores are clearly obtained. The mode interference near the distal end of DC-PCF was observed, and the interference process from independent faculae to the interaction of two core beams is presented. The velocimeter demonstrates a good working distance (∼30 µm) and a small measuring volume (∼273.4 µm³), which is well suited for flow measurement in micro-scale fluidic channels. The velocity measurement is successfully demonstrated by observing the frequency modulation and the spacing of the fringe projected interference. The measurements are verified and in good agreement with the results obtained by the light gate sensor.

我们介绍了使用双芯光子晶体光纤（DC-PCF）的激光多普勒差分测速仪的设计和特性。研究了DC-PCF的传输模式和模式干扰特性。结果表明，高阶模和包层模被激发，可以通过弯曲DC-PCF来切断。清楚地获得了两个核心的独立基本模式。观察到了DC-PCF远端附近的模干涉，并提出了从独立晶状体到两个核心光束相互作用的干涉过程。速度计显示出良好的工作距离（〜30 µm）和较小的测量体积（〜273.4 µm ^3）），非常适合在微型流体通道中进行流量测量。通过观察频率调制和条纹投影干涉的间距，可以成功地证明速度测量。测量结果经过验证，并与光闸传感器获得的结果高度吻合。