Highly Sensitive Airflow Sensor Based on Fabry-Perot Interferometer and Vernier Effect

A novel highly sensitive airflow sensor based on Fabry-Perot interferometer (FPI) and Vernier effect is proposed and demonstrated. The sensor is fabricated by splicing a section of hollow-core fiber (HCF) between a lead-in single mode fiber (SMF) and a section of SMF, which is almost one-fifteenth the length of the HCF. Airflow changes the cavity length of the FPI, which leads to the shift of the reflection spectrum. The reflection beam from the last end of the SMF is utilized to generate the Vernier effect, which enlarges the shift of the spectrum for 9.57 times than that of a single FPI. According to the experimental results, when the airflow ranges from 0 to 7m/s, the spectrum of the sensor shifts as high as 7.9 nm which is almost eight times more than that of the self-heating sensor based on silver-coated FBG. And the highest airflow velocity sensitivity of the sensor can reach 1.541 nm/(m/s) in the region of 3m/s similar to 7m/s. Besides, the sensor has a series of advantages such as fast response, low cost, compact size, and reflection measurement.