A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating (FBG) coated with a layer of silver film and optically heated by using a 1480 nm laser diode is demonstrated. The silver film absorbs the laser power to heat the FBG to a certain high temperature and the airflow cools down the FBG hot-wire with the cooling effect and hence the Bragg wavelength of the FBG is determined by the airflow velocity. Experimental measurement results show that the heating efficiency of the FBG hot wire is improved by 3.8 times in magnitude by etching the fiber cladding from 125 µm down to 73.4 µm, and the achieved airflow velocity sensitivities, under a laser power of 200 mW, are −3 180 pm/(m/s), −889 pm/(m/s), −268 pm/(m/s), and −8.7 pm/(m/s) at different airflow velocities of 0.1 m/s, 0.5 m/s, 1.5 m/s, and 17 m/s, respectively. In comparison, the sensitivities are only −2193 pm/(m/s), −567 pm/(m/s), −161 pm/(m/s), and −4.9 pm/(m/s) for the reference anemometer without cladding etching even at a much higher heating laser power of 530 mW. These results prove that the method by using a cladding-etched FBG to improve sensitivity of FBG-based hot-wire anemometers works and the sensitivity is improved significantly.

展示了一种基于镀层蚀刻光纤布拉格光栅 (FBG) 的灵敏度增强热线风速计，该光栅涂有一层银膜，并通过使用 1480 nm 激光二极管进行光学加热。银膜吸收激光功率将FBG加热到一定的高温，气流通过冷却作用使FBG热线冷却，因此FBG的布拉格波长由气流速度决定。实验测量结果表明，通过将光纤包层从 125 µm 蚀刻到 73.4 µm，FBG 热线的加热效率提高了 3.8 倍，并且在 200 mW 的激光功率下实现的气流速度灵敏度为 - 3 180 pm/(m/s)、−889 pm/(m/s)、−268 pm/(m/s) 和 −8.7 pm/(m/s) 在 0.1 m/s 的不同气流速度下， 0.5 m/s、1.5 m/s 和 17 m/s，分别。相比之下，参考灵敏度仅为-2193 pm/(m/s)、-567 pm/(m/s)、-161 pm/(m/s)和-4.9 pm/(m/s)即使在 530 mW 的高得多的加热激光功率下，也没有包层蚀刻的风速计。这些结果证明了使用包层蚀刻FBG来提高基于FBG的热线风速计灵敏度的方法是可行的，并且灵敏度得到了显着提高。