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1.引言纤维光导激光多普勒流速仪(LDA)可应用于水下,燃烧及涡轮机等测量中,它的小尺寸和整体设计使其配置和调试比较简单,也便于移动,也就特别适用于模型内部及近表面的测量。基于二根普通的单模光导纤维之上的纤维光导LDA早有介绍(Sasaki等,1980)。从原理上说,它有二个严重的缺陷:光导纤维不能保持二束激光的偏振状态。这可能导致整个LDA系统效率的下降。因为对有效的光外差检测(或条纹形成)的条件是每束偏振光的强度应相等。另一个困难的问题是纤维折射指数对诸如压力和温度等外部物理参数的敏感性。
1. Introduction Fiber-optic laser Doppler flowmeters (LDA) can be used in underwater, combustion and turbine measurements, and their small size and overall design make their configuration and commissioning simple and easy to move, which is particularly suitable Measurements inside and near the surface of the model. Fiber optic guides LDA based on two common single-mode optical fibers have been described (Sasaki et al., 1980). In principle, it has two serious drawbacks: the optical fiber can not maintain the polarization state of the two laser beams. This can lead to a reduction in the efficiency of the entire LDA system. Because of the effective optical heterodyne detection (or stripe formation) the condition is that each bundle of polarized light intensity should be equal. Another difficult issue is the sensitivity of the fiber’s refractive index to external physical parameters such as pressure and temperature.