||Fiber-optic Fabry-Pérot interferometers (FFPIs) have several advantages such as small size, high resolution, and simple structure. Among them, open-cavity FFPI sensors have high potentials in applications of refractive index (RI) sensing due to the high RI sensitivity. Previous study has proposed a FFPI formed by splicing fibers with a lateral offset, which requires precise alignment and enhances the fabrication difficulty. Moreover, some studies utilize femtosecond lasers to manufacture FFPI sensors, which results in high cost. As a result, we propose a method to simply splice a beveled single-mode fiber (SMF) to a cleaved lead-in SMF to fabricate an open-cavity FFPI. We have also employed chemical etching process to enlarge and control the cavity size. The utilized method is shown to reduce the fabrication difficulty, and no high-cost femtosecond lasers are required.|
The characteristics of our FFPI are demonstrated through measuring the reflection spectra. It is found that the free spectrum range of the interference fringes decreases with the etching time, and the calculated etching rates of the 3.5°-tiled sample and the 4°-tiled sample are 36.96nm/min and 49.36nm/min, respectively. We then apply the 3.5°-tiled FFPI to environmental parameter sensing. The RI sensitivity of the FFPI is 1202.77nm/RIU in the RI range of 1.3330~1.3478. The temperature sensitivity of the FFPI is only 8.64pm/°C between 25°C~85°C, which indicates that the FFPI can be used without temperature disturbance. In the frequency range of 200Hz~5000Hz, our FFPI exhibits signal-to-noise ratios of 42dB~46dB, which is higher than other FFPI vibration sensors. From the experimental results, our fabricated FFPI sensor indeed has good potentials for the measurement of RI and vibration.