Hot-Wire Anemometer Based on Silver-Coated Fiber Bragg Grating Assisted by No-Core Fiber

A novel hot-wire anemometer based on a silver-coated optical fiber Bragg grating (FBG) is proposed and experimentally demonstrated with the assistance of a short length of no-core fiber (NCF). The silver coating deposited on the surface of the FBG absorbs light of a pump laser, which is coupled into the fiber cladding by the NCF, to generate the heat, whereas air flow cools down the FBG by taking the heat away. A dynamic thermal equilibrium with a temperature codetermined by the pump laser power and airflow velocity can be reached. Bragg wavelength of the FBG changes with temperature thus is used to measure airflow velocity. Experimental results reveal that the highest resolution of ~ 0.0017 m/s is achieved and the measurement range covers 0-13.7 m/s.