Fiber-optic airflow velocity sensing method based on a 45° tilt fiber grating combined with a single-walled carbon nanotube coated fiber.

We propose and experimentally demonstrate an airflow velocity sensing method based on a 45° tilt fiber grating (TFG) that is combined with a single-walled carbon nanotube (SWCNT) coated fiber Bragg grating (FBG). The principle behind which is to produce a dynamic thermal equilibrium between the light heating and the airflow cooling. For the first time, to the best of our knowledge, a 45°-TFG is used as the heating element for the hot-wire anemometer. By diagnosing the Bragg wavelength of the SWCNT coated FBG, the temperature variations of the sensing fiber are measured with respect to the airflow velocities, which vary from 0 to 1 m/s. Moreover, under low light power consumption of 20 mW, the proposed sensor is shown to have good performance. Experimental results reveal that the sensitivity of the sensor increases with the heating pump. Due to the advantages of its simplicity and reliability, alongside its high photo-thermal conversion efficiency, this technique has excellent potential for future use in remote monitoring with airflow velocity sensing.