Abstract: The dynamic sensors for speed and flow are applied inpathological physiological research of thecardiovascular system and for the study of blood flowin the capillaries. The use of laser Doppler anemometry(LDA) method is considered the major prospective forthis application. This method is based on the Dopplershift of the frequency of laser radiation scattered byblood particles in movement. However, to have access toinner organs, a small-size delivery system and opticalprobe are necessary. In this paper, we report a novelminiature optical probe for the differential-type LDA,suitable for use in small blood vessels and in othersmall channels. For the construction of the probe,two-core single mode optical fiber was used. This fiberhad two anisotropic 8 $mu cores, located symmetricallywith respect to the fiber axis. The separation betweenthem was 25 $mu@. In the fiber, a directional couplerwas integrated near the fiber's remote end. The couplerwas fabricated by heating of a small section of thefiber, with simultaneous elongation of this section.For heating, the carbon-dioxide laser was utilized. Thecarbon-dioxide laser was also used to fabricate a lensat the fiber tip. At the fiber entrance, the laserlight was launched in one of the fiber's cores. Thefiber was typically of several meters long. Near thefiber end, this radiation was splitted by thedirectional coupler, and the second core was excitedtoo. At the fiber tip, the fused lens providedcollimation of the emerging beams and secured theirintersection in front of the fiber tip. In thisintersection volume, the interference field was formed.In the flow, this periodic pattern resulted in Dopplerfrequency shift of the light scattered by movingparticles. This probe was successfully used togetherwith the LDA signal processing equipment for velocitymeasurement in small tubes for blood-flow simulationexperiments. In the probe, the two cores are identical,and the between the directional coupler and the fibertip is very small. Thereafter, all extrinsic fields andeffects have identical influence on the propagationconstant of each core. Hence, the resultant parasiticphase modulation, that is the main problem in thefiber-based differential LDA, is negligible in thisprobe. This is the principal advantage of this probe.However, its small size and integrated nature are alsoof value for biomedical applications. !22
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机译：摘要：速度和流量的动态传感器在心血管系统的病理生理研究中以及在毛细血管中的血流研究中都得到了应用。激光多普勒风速测定法（LDA）的使用被认为是该应用的主要前景。该方法基于运动中血液颗粒散射的激光辐射频率的多普勒频移。但是，要获得内脏器官，必须使用小型传送系统和光学探头。在本文中，我们报告了一种适用于小血管和其他小通道的新型LDA微型光学探头。为了构造探头，使用了两芯单模光纤。该纤维具有两个各向异性的8μm芯，相对于纤维轴对称放置。它们之间的距离是25 $ mu @。在光纤中，定向耦合器集成在光纤远端附近。耦合器是通过加热一小部分纤维并同时延长该部分来制造的。为了加热，使用了二氧化碳激光器。二氧化碳激光也被用来在纤维尖端制造透镜。在光纤入口处，激光束被发射到光纤的一个纤芯中。纤维通常长几米。在光纤末端附近，该辐射被定向耦合器分开，第二个磁芯也被激发。在光纤尖端，熔融透镜提供了出射光束的准直，并将它们的交叉点固定在光纤尖端的前面。在这个相交的空间中，形成了干涉场。在流动中，这种周期性模式导致了运动粒子散射的光的多普勒频移。该探头已与LDA信号处理设备一起成功用于小管中的速度测量，以进行血流模拟实验。在探头中，两个纤芯是相同的，并且定向耦合器和光纤尖端之间的纤芯很小。此后，所有外在场和效应对每个核的传播常数具有相同的影响。因此，在基于光纤的差分LDA中，主要的问题是寄生相位调制，在该探头中可以忽略不计。这是该探头的主要优点。但是，它的小尺寸和整体性质对于生物医学应用也很有价值。 ！22
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