Separated-cavity Fabry-Perot interferometric gas pressure sensor based on hollow core Bragg fiber and Vernier effect

An ultra-high sensitivity separated Fabry-Perot interferometers (FPIs) sensor for gas pressure measurement based on hollow core Bragg fiber (HCBF) and Vernier effect is proposed. The HCBF functions as an FPI cavity and possesses low transmission loss. The sensing unit was prepared by splicing an HCBF at the millimeter scale between the single-mode fiber (SMF) and the hollow silica tube (HST). The reference unit was fabricated by sandwiching the HCBF between two SMFs. Both FPIs with similar free spectral ranges (FSRs) were connected to the 3-dB coupler parallelly to generate the Vernier effect. Experimental results showed that the proposed sensor achieved high gas pressure sensitivity of 77.80 nm/MPa with a linearity of 0.9992. Moreover, a low-temperature crosstalk of similar to 0.095 kPa/degrees C implies that the sensor is temperature insensitive. Compared to the traditional optical fiber gas pressure sensor, the proposed sensor features high sensitivity, stability, easy fabrication, and fast response.