Miniature fiber pressure sensor based on an in-fiber confocal cavity

Abstract A new type of miniature pressure sensor based on a hybrid Fabry-Perot (F-P) interferometer is proposed. The in-line air cavity of the sensor is a micro-confocal air cavity, which is formed by splicing together a single mode fiber (SMF) and a solid-core photonic crystal fiber (PCF) with the specific splicing parameters. The sensor is fabricated by simple steps involving only fusion splicing, cleaving and polishing. Optical interference principle of the sensor is analyzed and the parameters in sensor design are discussed. Due to low propagation loss, experiments show that the reflection spectrum of the sensor has a fringe contrast of more than 30 dB. By tracing the trough wavelength in the interference spectrum, the pressure can be demodulated. Within the pressure measurement range of 0–1 MPa, the sensitivity is −193 pm/MPa. The experimental results indicate that the deflection is consistent with the theoretical analysis and the sensor has a good linearity. Easy fabrication, low-cost and high-contrast make it appropriate for practical application.