A Simple FBG Fabry–Perot Sensor System With High Sensitivity Based on Fiber Laser Beat Frequency and Vernier Effect

A simple FBG Fabry-Perot sensor system with high sensitivity based on fiber laser beat frequency and Vernier effect is proposed and demonstrated. The sensor head is a Fabry-Perot (F-P) resonant cavity formed by two identical fiber Bragg gratings (FBGs), and the F-P cavity is a part of the laser cavity as a mirror. Vernier effect can be realized by choosing appropriate F-P cavity length and laser cavity length. So we achieved the sensitivity multiplication of the sensor, with sensitivity of 299.17 kHz/°C. The sensing information can be obtained by tracking the envelope of beat frequency signals generated by Vernier effect. This sensor system has the advantages of low cost, simple structure and high sensitivity.