Optical Fiber Thermal Anemometer with Light Source-Heated Fabry-Perot Interferometer

An optical fiber thermal anemometer with a light source-heated Fabry–Perot interferometer (FPI) is proposed. The FPI is fabricated on the tip of a single-mode fiber using an ultraviolet-cured adhesive. A broadband light source acts as a heating light source as well, eliminating the need for a heating resistor or a pump laser which are usually required in optical fiber thermal anemometers. The interference fringe of the FPI shifts with airflow velocity because airflow not only reduces temperature of the FPI but also introduces strain due to wind force. Airflow velocity is therefore measured by detecting wavelength shift of the interference fringe. In the experiment, a high sensitivity up to −3.13 nm/(m·s⁻¹) was achieved at the low velocity region, reducing to ∼−0.2 nm/(m·s⁻¹) at the high velocity region within the measurement range of 0–7 m/s. The response and recovery time is 250 and 580 ms, respectively. It is worth noting that the anemometer maintains a relatively high sensitivity at the high velocity region due to the contribution of wind force effect that makes it outperform most of the fiber thermal anemometers.